WO2010016562A1 - Etchant for copper or copper alloy material, pre-plating treatment method, and method for forming member for electronic component - Google Patents
Etchant for copper or copper alloy material, pre-plating treatment method, and method for forming member for electronic component Download PDFInfo
- Publication number
- WO2010016562A1 WO2010016562A1 PCT/JP2009/063986 JP2009063986W WO2010016562A1 WO 2010016562 A1 WO2010016562 A1 WO 2010016562A1 JP 2009063986 W JP2009063986 W JP 2009063986W WO 2010016562 A1 WO2010016562 A1 WO 2010016562A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- copper
- tin
- alloy material
- ion source
- copper alloy
- Prior art date
Links
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F1/00—Etching metallic material by chemical means
- C23F1/10—Etching compositions
- C23F1/14—Aqueous compositions
- C23F1/16—Acidic compositions
- C23F1/18—Acidic compositions for etching copper or alloys thereof
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
- C25D5/34—Pretreatment of metallic surfaces to be electroplated
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
- H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
- H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
- H05K3/3457—Solder materials or compositions; Methods of application thereof
- H05K3/3473—Plating of solder
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/07—Electric details
- H05K2201/0753—Insulation
- H05K2201/0769—Anti metal-migration, e.g. avoiding tin whisker growth
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/03—Metal processing
- H05K2203/0392—Pretreatment of metal, e.g. before finish plating, etching
Definitions
- the present invention relates to an etching solution for copper or a copper alloy material, a plating pretreatment method, and a method for forming an electronic component member intended to suppress the generation of whiskers.
- Tin and tin alloys (tin-copper (Sn-Cu), tin-silver (Sn-Ag), tin-bismuth (Sn-Bi), etc.) plating films have excellent solder wettability, so they are suitable for electronic parts. Widely used. However, it is known that whisker-shaped crystals of several tens of ⁇ m to several mm called whiskers are likely to be generated from the tin and tin alloy plating film, and when this whisker is generated from the tin and tin alloy plating film On the other hand, electrical and electronic boards cause short circuits and terminals, significantly reducing product performance and reliability. Here, the generation mechanism of whiskers will be described.
- a copper-tin intermetallic compound layer is formed at the interface between the copper or copper alloy material and the tin and tin alloy plating film due to change over time. .
- the intermetallic compound layer is concentrated at the grain boundary of the tin plating film, and thus is formed unevenly at the interface.
- the intermetallic compound layer thus formed unevenly grows along the grain boundaries of the tin and tin alloy plating film, and generates stress in the tin and tin alloy plating film.
- the whisker is a crystal formed to relieve the stress generated on the tin and tin alloy plating film, that is, the whisker is considered to generate the stress in the driving force.
- the following measures have been used so far (see, for example, Non-Patent Document 1).
- a technique for forming nickel plating on the base of a tin and tin alloy plating film has been proposed. This technique suppresses the generation of whiskers by using the formed nickel plating as a barrier for forming an intermetallic compound between copper, tin, and a tin alloy plating film.
- a technique for increasing the film thickness of the tin and tin alloy plating film to 10 to 20 ⁇ m or more has been proposed.
- this technique by increasing the film thickness of the plating film, the influence of internal stress caused by the formation of the intermetallic compound layer is made difficult to reach the plating surface layer, and the generation of whiskers is suppressed.
- the technique which performs heat processing and a reflow process after a tin and tin alloy plating process is proposed (for example, refer patent document 1 or 2).
- Non-Patent Document 1 Mitsubishi Electric Technical Report, 1979, vol. 53, no. 11 Patent Document 1 JP 2005-307240 A Patent Document 2 JP 2006-161146 A
- the effect of suppressing the whisker is not sufficient, and there are parts that cannot be nickel plated due to necessary characteristics. In some cases, or when there is a part that cannot be thickened, it cannot be applied.
- an oxide film is formed on the tin and tin alloy plating film by the heat treatment or reflow treatment, and tin and tin such as a decrease in solder wettability. Degradation of the alloy plating film occurs.
- the molten tin and tin alloy plating film flow and the film thickness varies. Furthermore, when performing these heat treatments and reflow treatments, it is necessary to prepare and treat new equipment after the plating treatment, resulting in an increase in equipment costs and treatment time. Furthermore, by forming a tin alloy plating film such as Sn—Cu, Sn—Ag, Sn—Bi, etc., the whisker suppression effect is improved as compared with the case where a tin plating film is formed, but the alloy ratio in the film In addition, since it is very difficult to control the alloy ratio in the plating solution, there is a problem that the quality is not stable.
- a tin alloy plating film such as Sn—Cu, Sn—Ag, Sn—Bi, etc.
- an etching process has been carried out in the pre-plating process for the purpose of improving the adhesion between the tin and tin alloy plating film and the material, and generally as an etching solution for copper and copper alloy materials.
- Many chemicals mainly composed of sulfuric acid and hydrogen peroxide are used.
- the etching solution mainly composed of sulfuric acid and hydrogen peroxide water is mainly used for the purpose of removing an oxide film or a work-affected layer on the surface of copper and copper alloy material. Even if it is used on the surface of a material, it has only a smooth and smooth shape.
- the copper-tin intermetallic compound layer is also locally generated at the interface between the copper and copper alloy material and the tin and tin alloy plating film, causing stress to the plating film, and the generation of whiskers. Can not be suppressed.
- various countermeasures have been tried to suppress whiskers generated with the formation of the tin and tin alloy plating film, but a technique that exhibits a sufficient effect has not yet been developed. Therefore, the development of a whisker suppression method that effectively suppresses the generation of whiskers without impairing the performance of the tin and tin alloy plating film is strongly desired.
- the present invention has been made in view of the problems and demands of these prior arts, and effectively reduces whiskers generated on the tin and tin alloy plating film without degrading the performance of the tin and tin alloy plating film. It is an object of the present invention to provide an etching solution for copper or a copper alloy material, a plating pretreatment method, and a method for forming a member for an electronic component, which can suppress the decrease in reliability related to connectivity and the like.
- a cupric ion source, a halogen ion source in the pre-plating surface treatment step of tin and tin alloy plating treatment The surface of the copper or copper alloy material is roughened using an etching solution for copper or copper alloy material containing organic acid as a main component, and tin and tin alloy plating pretreatment is performed, and the surface roughness is large and fine uneven shape It has been found that whiskers generated from tin and tin alloy plating film can be effectively suppressed.
- the etching solution for copper or copper alloy material according to the present invention is an etching solution used on the surface of copper or copper alloy material in order to suppress whisker generated on tin and tin alloy plating film,
- the main component is a cupric ion source, a halogen ion source, and an organic acid.
- the plating pretreatment method according to the present invention is a plating pretreatment method for copper or a copper alloy material surface for suppressing whisker generated on a tin and tin alloy plating film, and a second copper ion source,
- the surface of the said copper or copper alloy material is etched and roughened using the etching solution for copper or copper alloy material which has a halogen ion source and an organic acid as a main component.
- the method for forming an electronic component member according to the present invention includes an etching process step of etching using a copper or copper alloy material etchant containing a cupric ion source, a halogen ion source, and an organic acid as a main component, A plating treatment step of forming tin and a tin alloy plating film on the copper or copper alloy material roughened in the etching treatment step.
- FIG. 1A and 1B are SEM images showing surface states when the lead frame is etched to form a concavo-convex shape in the processing of Example 1 and Example 3.
- FIG. 2A and 2B are SEM images showing surface states when the lead frame is etched to form a concavo-convex shape in the processing of Comparative Example 2 and Comparative Example 3.
- FIG. 1A and 1B are SEM images showing surface states when the lead frame is etched to form a concavo-convex shape in the processing of Comparative Example 2 and Comparative Example 3.
- the etching solution for copper or copper alloy material according to the present invention is an etching solution used for etching treatment before plating treatment for the purpose of suppressing whiskers generated with the formation of tin and tin alloy plating film.
- Copper or copper alloy material such as a lead frame that is a member for electronic parts is subjected to usual predetermined surface treatment such as electrolytic degreasing treatment or pickling treatment, and then the surface of copper or copper alloy material using this etching solution Is etched to form fine irregularities with a large surface roughness.
- a plating film is formed by performing a tin and tin alloy plating treatment, and an electronic component member is formed.
- the copper and copper alloy material according to the present embodiment at least the surface thereof is formed of copper or a copper alloy, or the whole is formed of copper or a copper alloy such as a lead frame. The thing that is. Moreover, what has copper (copper alloy) laminated
- the etching solution for copper or copper alloy material used for the pre-plating etching surface treatment according to the present embodiment will be described.
- This etching solution contains a cupric ion source, a halogen ion source, and an organic acid as main components.
- a cupric ion source copper salts of organic acids such as copper (II) chloride, copper (II) bromide, copper hydroxide (II), copper acetate (II), copper formate (II) and the like are used.
- These cupric ion sources may be used alone or in combination of two or more at any ratio.
- the content of the cupric ion source is 2 to 50 g / L, preferably 5 to 25 g / L.
- the halogen ion source is an ion source such as chloride ion or bromide ion, for example, hydrochloric acid, sodium chloride, potassium chloride, calcium chloride, ammonium chloride, potassium bromide, hydrobromic acid, copper chloride, zinc chloride, iron chloride. , Iron bromide, tin bromide, copper bromide, and the like can be used.
- chloride ion or bromide ion for example, hydrochloric acid, sodium chloride, potassium chloride, calcium chloride, ammonium chloride, potassium bromide, hydrobromic acid, copper chloride, zinc chloride, iron chloride. , Iron bromide, tin bromide, copper bromide, and the like can be used.
- These halogen ion sources may be used individually by 1 type, or may use 2 or more types together in arbitrary ratios.
- copper (II) chloride can be used as having both functions of the halogen ion source and the above-described cupric ion source.
- the content of the halogen ion source is 5 to 200 g / L, preferably 10 to 150 g / L.
- the etching rate decreases, and when it is more than 200 g / L, no improvement in whisker suppression effect is observed.
- organic acids include saturated aliphatic monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, and stearic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and sebacic acid.
- saturated aliphatic monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, and stearic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and sebacic acid.
- Saturated aliphatic dicarboxylic acid acrylic acid, propiolic acid, crotonic acid, oleic acid, methacrylic acid and other unsaturated aliphatic monocarboxylic acids, maleic acid, fumaric acid and other unsaturated aliphatic dicarboxylic acids, benzoic acid, phthalic acid, Carboxylic carboxylic acids such as cinnamic acid, heterocyclic carboxylic acids such as thiophene carboxylic acid and nicotinic acid, aliphatic hydroxy acids such as glycolic acid, lactic acid, leucine acid, malic acid, tartaric acid, gluconic acid and citric acid, salicylic acid and vanillin Aromatic hydroxy acids such as acid and gallic acid can be mentioned.
- organic acids may be used individually by 1 type, or may use 2 or more types together by arbitrary ratios.
- the organic acid content is 5 to 300 g / L, preferably 10 to 200 g / L.
- the etching rate is reduced, and when it is more than 300 g / L, no further improvement in the whisker suppressing effect is observed, which is uneconomical.
- the copper and copper alloy material etching solution according to the present embodiment is mainly composed of a cupric ion source, a halogen ion source, and an organic acid, and tin and tin alloy plating treatment is performed using this etching solution.
- an etching process is performed on the copper or copper alloy surface.
- the uneven shape (surface roughness) formed on the copper or copper alloy material larger and finer than the etching solution that has been used in the past, and the generation of whiskers is effective.
- whiskers is effective.
- a copper-tin intermetallic compound layer is locally formed along the grain boundary of the plating film.
- the surface roughness is large and fine on the copper or copper alloy material by this etching process.
- the etching liquid which concerns on this Embodiment can further contain any 1 or more types of a polyamine compound and a polyvinyl compound.
- the polyamine compound for example, polyethyleneimine, polyalkylene polyamine, or the like can be used.
- a polyvinyl compound polyvinyl pyrrolidone, polyvinyl alcohol, etc. can be used, for example.
- these polyamine compounds and polyvinyl compounds may be used individually by 1 type, or may use 2 or more types together in arbitrary ratios.
- the content of these polyamine compounds and polyvinyl compounds is 0.0001 to 10 g / L, preferably 0.0005 to 5 g / L. When the content is less than 0.0001 g / L, the effect of suppressing whisker by addition cannot be obtained, and when the content is more than 10 g / L, not only the improvement of whisker suppression effect by addition is not seen, but also the etching rate decreases. To do.
- copper or copper can be obtained by further containing any one or more of a polyamine compound and a polyvinyl compound in an etching solution mainly composed of a cupric ion source, a halogen ion source, and an organic acid.
- an etching solution mainly composed of a cupric ion source, a halogen ion source, and an organic acid.
- the alloy material it is possible to form a fine uneven shape with a larger surface roughness. And thereby, the local gathering of stress can be prevented and generation
- this non-uniform intermetallic compound layer causes stress in the tin plating film, resulting in the generation of whiskers.
- the contact area between the copper or copper alloy material and the tin plating film is increased by including polyamine compound or polyvinyl compound, forming a larger unevenness with finer surface roughness.
- the copper diffusion direction does not become one direction but can be made random.
- the etching solution according to the present embodiment may further contain any one or more of a ferric ion source, a zinc ion source, and a nickel ion source.
- ferric ion source for example, iron (III) chloride, iron (III) bromide, iron (III) iodide, iron (III) sulfate, iron (III) nitrate, iron (III) acetate Further, iron (III) ammonium citrate and the like can be used.
- the zinc ion source includes zinc chloride (II), zinc bromide (II), zinc iodide (II), zinc sulfate (II), zinc nitrate (II), zinc acetate (II), zinc formate (II ), Zinc oxalate (II) and the like can be used.
- Nickel ion sources include nickel chloride (II), nickel bromide (II), nickel iodide (II), nickel sulfate (II), nickel nitrate (II), nickel acetate (II), nickel formate (II). ), Nickel sulfamate (II), nickel oxalate (II), and the like. These ferric ion sources, zinc ion sources, and nickel ion sources may be used singly or in combination of two or more at any ratio. The content of these compounds is 0.00005 to 0.005 g / L, preferably 0.0001 to 0.002 g / L.
- any one or more of a ferric ion source, a zinc ion source, and a nickel ion source is added to the etching liquid mainly composed of a cupric ion source, a halogen ion source, and an organic acid. Furthermore, by making it contain, the fall of the etching rate by the fluctuation
- the etching agent according to the present embodiment can further contain various additives.
- a known pH stabilizer can be contained so that a stable etching process can be performed while suppressing fluctuations in pH.
- an additive it is not restricted to this, You may make it contain other various additives.
- the etching solution described above is used as a pretreatment for plating, and the etching treatment for roughening the surface of copper or copper alloy material. To give.
- Etching treatment as a treatment is performed to form a fine uneven shape on the surface of the copper or copper alloy material with a large surface roughness.
- tin or a tin alloy plating process is performed on the copper or copper alloy material whose surface is roughened by the etching process. This etching process can be performed using a known method.
- the etching process is performed by immersing copper or a copper alloy material in the above-described etching solution or by bringing the etching solution into contact with a spray method. .
- electrolytic etching by electrolytic treatment is also possible.
- the processing time of the etching process is not particularly limited, but for example, the processing is performed for 1 to 300 seconds, preferably 5 to 200 seconds.
- the temperature condition of the etching solution is not particularly limited, but is 10 to 80 ° C., preferably 25 to 50 ° C., for example. By this etching treatment, a fine uneven shape with a large surface roughness is formed on the surface of the copper or copper alloy material.
- the average roughness Ra in this description is the same as the “arithmetic average roughness Ra” defined by JIS B 0601-1994. Specifically, the average roughness Ra in the direction of the average line from the roughness curve. A predetermined reference length is extracted, and the absolute values of deviations from the average line of the extracted portion to the roughness curve are summed and averaged.
- a large and fine uneven shape with a Ra value of 0.2 ⁇ m or more is formed on the surface of copper or a copper alloy material using the above-described etching solution. Let it form.
- the intermetallic compound layer generated at the interface between the tin plating film and the copper or copper alloy material formed by the subsequent plating process is formed substantially uniformly over the entire interface, thereby suppressing the local concentration of stress. Can do. As a result, whiskers formed due to the intensive generation of stress can be suppressed.
- the surface of the copper or copper alloy material has a large surface roughness and a fine uneven shape to suppress the occurrence of whiskers. It does not affect the solder wettability of the tin and tin alloy plating film formed by the plating process and the adhesion between the copper or copper alloy material and the tin and tin alloy plating film. Thus, whisker generation can be effectively suppressed without degrading the performance of the tin and tin alloy plating film.
- tin and tin are formed on the surface of the copper or copper alloy.
- Alloy plating treatment is performed.
- known plating methods and conditions can be applied, and there is no particular limitation.
- the tin and tin alloy plating treatment conditions are not particularly limited.
- the temperature of the plating solution is preferably 15 to 55 ° C., and the plating time is preferably changed depending on the desired plating film thickness. .
- an etching process as a pretreatment for plating is performed using an etchant mainly composed of a cupric ion source, a halogen ion source, and an organic acid on the surface of copper or a copper alloy material.
- an etchant mainly composed of a cupric ion source, a halogen ion source, and an organic acid on the surface of copper or a copper alloy material.
- a member for electronic component is formed by forming a tin plating film by a tin and tin alloy plating treatment.
- the member for electronic parts formed in this way is in a state in which whisker causing a short circuit or the like does not occur or the performance of the plating film such as wettability is maintained.
- the etching solution according to the present embodiment is mainly composed of a cupric ion source, a halogen ion source, and an organic acid, and this etching solution is used before tin and tin alloy plating treatment.
- Etching is performed on the copper or copper alloy surface as a treatment.
- the uneven shape (surface roughness) formed on the copper or copper alloy material can be made large and fine, and the generation of whiskers can be more effectively suppressed. That is, the intermetallic compound layer formed at the interface between the copper material and the tin and tin alloy plating film is formed substantially uniformly over the entire interface due to the large surface roughness and fine uneven shape formed by this etching process.
- whisker can be effectively suppressed only by performing an etching process in the pre-treatment process of the tin and tin alloy plating process, so there is no need for an increase in the number of process steps and the addition of special equipment. In addition, it is possible to effectively suppress the generation of whiskers and to form a good electronic component member with improved reliability without connection failure.
- the present invention is not limited to the above-described embodiment, and any design change or the like within a range not departing from the gist of the invention is included in the present invention.
- the various compounds contained in the etching solution according to the above-described embodiment are examples that can be applied, and are not limited to those listed above. Examples Hereinafter, examples of the present invention will be described.
- the etching solution for copper or copper alloy according to the present invention and the etching treatment method using the etching solution are not limited to the following examples.
- Examples 1 to 8 As an example, a copper alloy material (C194) lead frame (surface area: 0.245 dm 2 ) was etched by an immersion method using an etching solution having the composition of Examples 1 to 8 shown in Table 1 below. Using the tin plating bath having the composition shown in FIG. The treated evaluation sample was stored in a thermostat kept at 30 ° C.-60% RH, and after 4000 hours, whiskers on the formed tin plating film were observed with a scanning electron microscope (SEM). In the evaluation test, the surface roughness (Ra) and the unevenness average interval (Sm) after the etching treatment were also measured by laser microscope observation.
- SEM scanning electron microscope
- the uneven average interval (Sm) measured in this example is the “average uneven interval” defined by JIS B 0601-1994. Specifically, from the roughness curve, the average line A certain reference length is extracted in the direction, and the sum of the lengths of the average lines corresponding to one peak and one valley adjacent to the peak is obtained to represent the average value. If Sm is small, it is determined that the uneven surface is fine.
- Comparative Examples 2 to 8 Further, as Comparative Examples 2 to 8, Examples were made using an etching solution having the composition of Comparative Examples 2 to 8 shown in Table 2 below with respect to a copper alloy material (C194) lead frame (surface area: 0.245 dm 2 ).
- etching was performed by an immersion method, and then tin plating was performed using a tin plating bath having the same composition as described above to obtain an evaluation sample. Then, in the same manner as in the examples, the treated evaluation samples were stored in a thermostatic bath maintained at 30 ° C.-60% RH, and formed with a scanning electron microscope (SEM) after lapse of 4000 hours. The upper whisker was observed. Moreover, also about the surface roughness (Ra) after an etching process, and uneven
- FIG. 1A and 1B show SEM images showing the surface state when the lead frame is etched to form a concavo-convex shape
- FIG. 2 shows a comparative example
- 2 and Comparative Example 3 show SEM images showing the surface state when the lead frame is etched to form a concavo-convex shape
- FIG. 2A Comparative Example 2
- FIG. 2B Comparative Example 3
- etching is performed with an etching solution containing copper (II) chloride as a cupric ion source, acetic acid as an organic acid, and sodium chloride as a halogen ion source.
- whisker generation was slightly confirmed, but whisker having a length of 10 ⁇ m or less was only slightly confirmed, and suppression of whisker generation was suppressed. It was confirmed that it was possible. This is because, as can be seen from the fact that the surface of the lead frame after the etching process is rough with a Ra value of 0.22 ⁇ m, the surface of the copper-tin intermetallic compound layer is formed by forming an uneven shape on the surface.
- Example 2 the content of copper (II) chloride as the cupric ion source was 20 g / L by further containing ferric chloride (III) as the ferric ion source. Even in the case, it was possible to form an uneven shape on the surface of the lead frame as in Example 1, and to suppress the generation of whiskers. Furthermore, in Examples 3 to 8 in which various polyamine compounds or polyvinyl compounds were further contained in the etching solution mainly composed of a cupric ion source, an organic acid, and a halogen ion source, generation of whiskers occurred.
- whiskers could be completely prevented. This can be judged from the fact that the surface roughness in the lead frames of Examples 3 to 8 is 0.27 to 0.43 ⁇ m in Ra value, as compared with Examples 1 and 2.
- the surface roughness can be increased, fine irregularities can be formed on the surface of the lead frame, and the intermetallic compound layer can be formed more uniformly over the entire interface, suppressing the concentration of stress locally. It is thought that it was made.
- the whisker having a length of 10 ⁇ m or more is obtained in the comparative example 1 in which the lead frame was not etched as a pre-process of the tin plating process.
- the average spacing of the irregularities formed on the surface of the lead frame is 2.36 ⁇ m to 2.98 ⁇ m in terms of Sm value.
- Sm value 2.36 ⁇ m to 2.75 ⁇ m.
- the surface roughness was large and fine irregularities could be formed on the lead frame surface.
- the average interval of the concavo-convex shape formed on the lead frame surface is 3.60 ⁇ m to 4.55 ⁇ m in Sm value.
- the average interval Sm of the concavo-convex shape was large.
- the measurement result of the average interval Sm of the concavo-convex shape after the etching treatment even if the concavo-convex shape has a surface roughness Ra value of 0.2 ⁇ m or more, if the fine concavo-convex shape is not formed, the whisker suppressing effect It can be clearly seen that is not exhibited.
- the etching solution mainly containing sodium peroxide and sulfuric acid of Comparative Example 2 and the hydrogen peroxide solution and sulfuric acid of Comparative Examples 3, 5, and 6 are mainly used.
- the surface roughness is 0.22 to 0.37 ⁇ m in Ra value, and an uneven shape can be formed.
- it is judged from the average interval Sm value of the uneven shape and FIG. Thus, it was not possible to form a fine uneven shape.
- the comparative example 7 processed using the etching liquid which does not contain the halogen ion source among the cupric ion source which was the main components of the etching liquid in Examples 1 thru
- Comparative Example 8 processed using an etching solution not containing an organic acid, as described above, an uneven shape having a large surface roughness could be formed, but a fine uneven shape was formed. The whisker suppression effect was not possible. From this result, the surface roughness of the lead frame or the like is increased by processing with an etchant containing a cupric ion source, an organic acid, and a halogen ion source as a main component and having a fine surface roughness.
- the surface of the copper and copper alloy material such as a lead frame for forming the plating film is formed by using a second copper ion source, an organic acid, and a halogen ion. It has been found that whiskers can be effectively suppressed by etching with an etchant containing a source as a main component and forming a fine uneven shape on the surface with a large surface roughness.
- copper or copper is used in the pretreatment of the tin and tin alloy plating treatment by using an etching solution mainly composed of a cupric ion source, a halogen ion source, and an organic acid. Since the surface of the alloy material is roughened to form a rough surface with a large surface roughness and fine irregularities, local stress is prevented from occurring in the tin and tin alloy plating film, and whisker generation is effectively prevented. Can be suppressed.
- the plating film can be formed without causing the performance deterioration such as the solder wettability of the plating film.
- the occurrence of whiskers can be suppressed without performing heat treatment or reflow treatment. Furthermore, there is no need to increase the number of processing steps or add special equipment.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Metallurgy (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- Electrochemistry (AREA)
- Manufacturing & Machinery (AREA)
- Microelectronics & Electronic Packaging (AREA)
- ing And Chemical Polishing (AREA)
- Electroplating Methods And Accessories (AREA)
Abstract
Disclosed is a method for forming a member for electronic components, which comprises an etching step wherein etching is carried out using an etchant for copper or copper alloy materials which is mainly composed of a copper (II) ion source, a halogen ion source and an organic acid, and a plating step wherein a tin or tin alloy plating film is formed on a copper or copper alloy material roughened in the etching step. Consequently, whiskers to be generated on the tin or tin alloy plating film are suppressed, thereby maintaining the performance of a resulting product and reliability thereof for connection and the like.
Description
本発明は、本発明は、ウィスカの発生を抑制すること目的とする銅又は銅合金材用エッチング液、めっき前処理方法、並びに電子部品用部材の形成方法に関する。
本出願は、日本国において2008年8月8日に出願された日本特許出願番号2008-205851を基礎として優先権を主張するものであり、この出願を参照することにより、本出願に援用される。 The present invention relates to an etching solution for copper or a copper alloy material, a plating pretreatment method, and a method for forming an electronic component member intended to suppress the generation of whiskers.
This application claims priority on the basis of Japanese Patent Application No. 2008-205851 filed in Japan on August 8, 2008, and is incorporated herein by reference. .
本出願は、日本国において2008年8月8日に出願された日本特許出願番号2008-205851を基礎として優先権を主張するものであり、この出願を参照することにより、本出願に援用される。 The present invention relates to an etching solution for copper or a copper alloy material, a plating pretreatment method, and a method for forming an electronic component member intended to suppress the generation of whiskers.
This application claims priority on the basis of Japanese Patent Application No. 2008-205851 filed in Japan on August 8, 2008, and is incorporated herein by reference. .
錫及び錫合金(錫-銅(Sn-Cu)、錫-銀(Sn-Ag)、錫-ビスマス(Sn-Bi)等)めっき皮膜は、はんだ濡れ性に優れていることから電子部品等に広く利用されている。しかしながら、その錫及び錫合金めっき皮膜からは、ウィスカと呼ばれる数十μm~数mmのひげ状の結晶が発生しやすいことが知られており、このウィスカが錫及び錫合金めっき皮膜から発生した場合には、電気・電子基板においては回路や端子の短絡を引き起こし、製品の性能や信頼性を著しく低下させる。
ここで、ウィスカの発生メカニズムについて説明する。銅又は銅合金材上に錫及び錫合金めっき処理を施した試料においては、経時変化により銅又は銅合金材と錫及び錫合金めっき皮膜との界面に銅-錫金属間化合物層が形成される。この金属間化合物層は、銅の拡散が錫めっき皮膜の表面に向かって一方向に進むと、錫めっき皮膜の粒界に集中してしまうため、その界面に不均一に形成されてしまう。そして、このようにして不均一に形成された金属間化合物層は、錫及び錫合金めっき皮膜の粒界に沿って成長していくとともに、錫及び錫合金めっき皮膜に応力を発生させる。ウィスカは、この錫及び錫合金めっき皮膜上に発生した応力を緩和させるために形成される結晶であり、すなわちウィスカは、その応力を駆動力に発生するものと考えられている。
このようなウィスカの発生を抑制するために、これまで以下のような対策が用いられている(例えば、非特許文献1参照)。
例えば、錫及び錫合金めっき皮膜の下地にニッケルめっきを形成する技術が提案されている。この技術は、形成したニッケルめっきを、素材の銅と錫及び錫合金めっき皮膜との金属間化合物形成のバリアーとすることによって、ウィスカの発生を抑制させるというものである。
また、他の方法として、錫及び錫合金めっき皮膜の膜厚を、10~20μm以上に厚くする技術が提案されている。この技術は、めっき皮膜の膜厚を厚くすることで、金属間化合物層の形成により生じた内部応力の影響をめっき表層まで及び難くして、ウィスカの発生を抑制するというものである。
また、錫及び錫合金めっき処理後に、熱処理やリフロー処理を施す技術が提案されている(例えば、特許文献1又は2参照)。これらの技術は、めっき皮膜に熱処理やリフロー処理を施すことにより、錫及び錫合金めっき皮膜の残留応力を緩和するとともに、銅又は銅合金材とめっき皮膜との界面に均一な金属間化合物層を形成させて、銅の更なる錫及び錫合金めっき皮膜中への拡散を抑える効果を発揮させる。そして、その結果、ウィスカの発生を抑制するというものである。
非特許文献1 三菱電機技報,1979年,vol.53,No.11
特許文献1 特開2005-307240号公報
特許文献2 特開2006-161146号公報 Tin and tin alloys (tin-copper (Sn-Cu), tin-silver (Sn-Ag), tin-bismuth (Sn-Bi), etc.) plating films have excellent solder wettability, so they are suitable for electronic parts. Widely used. However, it is known that whisker-shaped crystals of several tens of μm to several mm called whiskers are likely to be generated from the tin and tin alloy plating film, and when this whisker is generated from the tin and tin alloy plating film On the other hand, electrical and electronic boards cause short circuits and terminals, significantly reducing product performance and reliability.
Here, the generation mechanism of whiskers will be described. In a sample in which tin and tin alloy plating treatment is performed on copper or a copper alloy material, a copper-tin intermetallic compound layer is formed at the interface between the copper or copper alloy material and the tin and tin alloy plating film due to change over time. . When the diffusion of copper proceeds in one direction toward the surface of the tin plating film, the intermetallic compound layer is concentrated at the grain boundary of the tin plating film, and thus is formed unevenly at the interface. The intermetallic compound layer thus formed unevenly grows along the grain boundaries of the tin and tin alloy plating film, and generates stress in the tin and tin alloy plating film. The whisker is a crystal formed to relieve the stress generated on the tin and tin alloy plating film, that is, the whisker is considered to generate the stress in the driving force.
In order to suppress the occurrence of such whiskers, the following measures have been used so far (see, for example, Non-Patent Document 1).
For example, a technique for forming nickel plating on the base of a tin and tin alloy plating film has been proposed. This technique suppresses the generation of whiskers by using the formed nickel plating as a barrier for forming an intermetallic compound between copper, tin, and a tin alloy plating film.
As another method, a technique for increasing the film thickness of the tin and tin alloy plating film to 10 to 20 μm or more has been proposed. In this technique, by increasing the film thickness of the plating film, the influence of internal stress caused by the formation of the intermetallic compound layer is made difficult to reach the plating surface layer, and the generation of whiskers is suppressed.
Moreover, the technique which performs heat processing and a reflow process after a tin and tin alloy plating process is proposed (for example, refer patent document 1 or 2). These technologies apply heat treatment and reflow treatment to the plating film to relieve the residual stress of the tin and tin alloy plating film and to form a uniform intermetallic compound layer at the interface between the copper or copper alloy material and the plating film. It is formed to exert an effect of suppressing diffusion of copper into further tin and tin alloy plating film. As a result, the generation of whiskers is suppressed.
Non-Patent Document 1 Mitsubishi Electric Technical Report, 1979, vol. 53, no. 11
Patent Document 1 JP 2005-307240 A Patent Document 2 JP 2006-161146 A
ここで、ウィスカの発生メカニズムについて説明する。銅又は銅合金材上に錫及び錫合金めっき処理を施した試料においては、経時変化により銅又は銅合金材と錫及び錫合金めっき皮膜との界面に銅-錫金属間化合物層が形成される。この金属間化合物層は、銅の拡散が錫めっき皮膜の表面に向かって一方向に進むと、錫めっき皮膜の粒界に集中してしまうため、その界面に不均一に形成されてしまう。そして、このようにして不均一に形成された金属間化合物層は、錫及び錫合金めっき皮膜の粒界に沿って成長していくとともに、錫及び錫合金めっき皮膜に応力を発生させる。ウィスカは、この錫及び錫合金めっき皮膜上に発生した応力を緩和させるために形成される結晶であり、すなわちウィスカは、その応力を駆動力に発生するものと考えられている。
このようなウィスカの発生を抑制するために、これまで以下のような対策が用いられている(例えば、非特許文献1参照)。
例えば、錫及び錫合金めっき皮膜の下地にニッケルめっきを形成する技術が提案されている。この技術は、形成したニッケルめっきを、素材の銅と錫及び錫合金めっき皮膜との金属間化合物形成のバリアーとすることによって、ウィスカの発生を抑制させるというものである。
また、他の方法として、錫及び錫合金めっき皮膜の膜厚を、10~20μm以上に厚くする技術が提案されている。この技術は、めっき皮膜の膜厚を厚くすることで、金属間化合物層の形成により生じた内部応力の影響をめっき表層まで及び難くして、ウィスカの発生を抑制するというものである。
また、錫及び錫合金めっき処理後に、熱処理やリフロー処理を施す技術が提案されている(例えば、特許文献1又は2参照)。これらの技術は、めっき皮膜に熱処理やリフロー処理を施すことにより、錫及び錫合金めっき皮膜の残留応力を緩和するとともに、銅又は銅合金材とめっき皮膜との界面に均一な金属間化合物層を形成させて、銅の更なる錫及び錫合金めっき皮膜中への拡散を抑える効果を発揮させる。そして、その結果、ウィスカの発生を抑制するというものである。
非特許文献1 三菱電機技報,1979年,vol.53,No.11
特許文献1 特開2005-307240号公報
特許文献2 特開2006-161146号公報 Tin and tin alloys (tin-copper (Sn-Cu), tin-silver (Sn-Ag), tin-bismuth (Sn-Bi), etc.) plating films have excellent solder wettability, so they are suitable for electronic parts. Widely used. However, it is known that whisker-shaped crystals of several tens of μm to several mm called whiskers are likely to be generated from the tin and tin alloy plating film, and when this whisker is generated from the tin and tin alloy plating film On the other hand, electrical and electronic boards cause short circuits and terminals, significantly reducing product performance and reliability.
Here, the generation mechanism of whiskers will be described. In a sample in which tin and tin alloy plating treatment is performed on copper or a copper alloy material, a copper-tin intermetallic compound layer is formed at the interface between the copper or copper alloy material and the tin and tin alloy plating film due to change over time. . When the diffusion of copper proceeds in one direction toward the surface of the tin plating film, the intermetallic compound layer is concentrated at the grain boundary of the tin plating film, and thus is formed unevenly at the interface. The intermetallic compound layer thus formed unevenly grows along the grain boundaries of the tin and tin alloy plating film, and generates stress in the tin and tin alloy plating film. The whisker is a crystal formed to relieve the stress generated on the tin and tin alloy plating film, that is, the whisker is considered to generate the stress in the driving force.
In order to suppress the occurrence of such whiskers, the following measures have been used so far (see, for example, Non-Patent Document 1).
For example, a technique for forming nickel plating on the base of a tin and tin alloy plating film has been proposed. This technique suppresses the generation of whiskers by using the formed nickel plating as a barrier for forming an intermetallic compound between copper, tin, and a tin alloy plating film.
As another method, a technique for increasing the film thickness of the tin and tin alloy plating film to 10 to 20 μm or more has been proposed. In this technique, by increasing the film thickness of the plating film, the influence of internal stress caused by the formation of the intermetallic compound layer is made difficult to reach the plating surface layer, and the generation of whiskers is suppressed.
Moreover, the technique which performs heat processing and a reflow process after a tin and tin alloy plating process is proposed (for example, refer patent document 1 or 2). These technologies apply heat treatment and reflow treatment to the plating film to relieve the residual stress of the tin and tin alloy plating film and to form a uniform intermetallic compound layer at the interface between the copper or copper alloy material and the plating film. It is formed to exert an effect of suppressing diffusion of copper into further tin and tin alloy plating film. As a result, the generation of whiskers is suppressed.
Non-Patent Document 1 Mitsubishi Electric Technical Report, 1979, vol. 53, no. 11
Patent Document 1 JP 2005-307240 A Patent Document 2 JP 2006-161146 A
しかしながら、上述した下地としてニッケルめっき皮膜を形成させる技術や、錫及び錫合金めっき皮膜の膜厚を厚くする技術では、そのウィスカ抑制の効果が十分でなく、必要な特性によりニッケルめっきができない部品がある場合や、膜厚を厚くすることができない部品がある場合には適用することができない。
また、錫及び錫合金めっき後に熱処理やリフロー処理を施す技術の場合には、その熱処理やリフロー処理により錫及び錫合金めっき皮膜上に酸化皮膜が形成され、はんだ濡れ性の低下等の錫及び錫合金めっき皮膜の劣化が生じてしまう。また、リフロー処理の場合には、溶融した錫及び錫合金めっき皮膜が流動して、膜厚にばらつきが生じる。さらに、これらの熱処理やリフロー処理を行う場合には、めっき処理後に新たな設備を用意して処理する必要があり、設備コストや処理時間の増加をもたらす。
さらに、Sn-Cu、Sn-Ag、Sn-Bi等の錫合金めっき皮膜を形成させることによって、錫めっき皮膜を形成させた場合に比べてウィスカの抑制効果は向上するものの、皮膜中の合金比率やめっき液中の合金比率を管理することが非常に困難なため、品質が安定しないという問題がある。
またさらに、従来より、錫及び錫合金めっき皮膜と素材との密着性の向上を目的に、めっき処理の前工程にエッチング処理が実施されており、一般的に銅、銅合金材のエッチング液として硫酸と過酸化水素水を主成分とした薬液が多く使用されている。しかしながら、その硫酸と過酸化水素水を主成分とするエッチング液は、主に銅及び銅合金材の表面の酸化皮膜や加工変質層の除去を目的として使用されるものであり、銅及び銅合金材の表面に対して使用しても、なだらかで平滑な形状にしかならない。その結果、やはり銅-錫金属間化合物層が、銅及び銅合金材と錫及び錫合金めっき皮膜との界面に局部的に発生し、めっき皮膜に応力を生じさせてしまうこととなり、ウィスカの発生を抑制することはできない。
このように、錫及び錫合金めっき皮膜の形成に伴って発生するウィスカの抑制には、これまで種々の対策が試みられてきたが、十分な効果を発揮する技術は未だ開発されていない。したがって、錫及び錫合金めっき皮膜の性能を損なうことなく、効果的にウィスカの発生を抑制するウィスカ抑制方法の開発が強く望まれている。
本発明は、これらの従来技術の問題点並びに要請に鑑みてなされたものであり、錫及び錫合金めっき皮膜の性能を低下させることなく、錫及び錫合金めっき皮膜上に発生するウィスカを効果的に抑制し、接続性等に関する信頼性の低下を防止することができる銅又は銅合金材用エッチング液、めっき前処理方法、並びに電子部品用部材の形成方法を提供することを目的とする。
課題を解決するための手段
本発明者らは、上記課題を解決するために鋭意検討を重ねた結果、錫及び錫合金めっき処理のめっき前表面処理工程において、第二銅イオン源、ハロゲンイオン源、有機酸を主成分とする銅又は銅合金材用エッチング液を用いて銅又は銅合金材の表面を粗化する錫及び錫合金めっき前処理を行い、表面粗さが大きくかつ微細な凹凸形状とすることで、錫及び錫合金めっき皮膜から発生するウィスカを効果的に抑制することができることを見出した。
すなわち、本発明に係る銅又は銅合金材用エッチング液は、錫及び錫合金めっき皮膜上に発生するウィスカを抑制するために、銅又は銅合金材の表面に使用されるエッチング液であって、第二銅イオン源と、ハロゲンイオン源と、有機酸とを主成分とする。
また、本発明に係るめっき前処理方法は、錫及び錫合金めっき皮膜上に発生するウィスカを抑制させるための銅又は銅合金材表面のめっき前処理方法であって、第二銅イオン源と、ハロゲンイオン源と、有機酸とを主成分とする銅又は銅合金材用エッチング液を用いて、上記銅又は銅合金材の表面をエッチング処理して粗化する。
また、本発明に係る電子部品用部材の形成方法は、第二銅イオン源、ハロゲンイオン源、有機酸を主成分とする銅又は銅合金材用エッチング液を用いてエッチングするエッチング処理工程と、上記エッチング処理工程にて粗化された銅又は銅合金材に対して錫及び錫合金めっき皮膜を形成させるめっき処理工程とを有する。 However, with the technology for forming a nickel plating film as the base and the technology for increasing the thickness of the tin and tin alloy plating film, the effect of suppressing the whisker is not sufficient, and there are parts that cannot be nickel plated due to necessary characteristics. In some cases, or when there is a part that cannot be thickened, it cannot be applied.
In addition, in the case of a technique for performing heat treatment or reflow treatment after tin and tin alloy plating, an oxide film is formed on the tin and tin alloy plating film by the heat treatment or reflow treatment, and tin and tin such as a decrease in solder wettability. Degradation of the alloy plating film occurs. Further, in the case of the reflow treatment, the molten tin and tin alloy plating film flow and the film thickness varies. Furthermore, when performing these heat treatments and reflow treatments, it is necessary to prepare and treat new equipment after the plating treatment, resulting in an increase in equipment costs and treatment time.
Furthermore, by forming a tin alloy plating film such as Sn—Cu, Sn—Ag, Sn—Bi, etc., the whisker suppression effect is improved as compared with the case where a tin plating film is formed, but the alloy ratio in the film In addition, since it is very difficult to control the alloy ratio in the plating solution, there is a problem that the quality is not stable.
Furthermore, conventionally, an etching process has been carried out in the pre-plating process for the purpose of improving the adhesion between the tin and tin alloy plating film and the material, and generally as an etching solution for copper and copper alloy materials. Many chemicals mainly composed of sulfuric acid and hydrogen peroxide are used. However, the etching solution mainly composed of sulfuric acid and hydrogen peroxide water is mainly used for the purpose of removing an oxide film or a work-affected layer on the surface of copper and copper alloy material. Even if it is used on the surface of a material, it has only a smooth and smooth shape. As a result, the copper-tin intermetallic compound layer is also locally generated at the interface between the copper and copper alloy material and the tin and tin alloy plating film, causing stress to the plating film, and the generation of whiskers. Can not be suppressed.
As described above, various countermeasures have been tried to suppress whiskers generated with the formation of the tin and tin alloy plating film, but a technique that exhibits a sufficient effect has not yet been developed. Therefore, the development of a whisker suppression method that effectively suppresses the generation of whiskers without impairing the performance of the tin and tin alloy plating film is strongly desired.
The present invention has been made in view of the problems and demands of these prior arts, and effectively reduces whiskers generated on the tin and tin alloy plating film without degrading the performance of the tin and tin alloy plating film. It is an object of the present invention to provide an etching solution for copper or a copper alloy material, a plating pretreatment method, and a method for forming a member for an electronic component, which can suppress the decrease in reliability related to connectivity and the like.
Means for Solving the Problems As a result of intensive studies in order to solve the above problems, the present inventors have found that a cupric ion source, a halogen ion source in the pre-plating surface treatment step of tin and tin alloy plating treatment The surface of the copper or copper alloy material is roughened using an etching solution for copper or copper alloy material containing organic acid as a main component, and tin and tin alloy plating pretreatment is performed, and the surface roughness is large and fine uneven shape It has been found that whiskers generated from tin and tin alloy plating film can be effectively suppressed.
That is, the etching solution for copper or copper alloy material according to the present invention is an etching solution used on the surface of copper or copper alloy material in order to suppress whisker generated on tin and tin alloy plating film, The main component is a cupric ion source, a halogen ion source, and an organic acid.
Moreover, the plating pretreatment method according to the present invention is a plating pretreatment method for copper or a copper alloy material surface for suppressing whisker generated on a tin and tin alloy plating film, and a second copper ion source, The surface of the said copper or copper alloy material is etched and roughened using the etching solution for copper or copper alloy material which has a halogen ion source and an organic acid as a main component.
Moreover, the method for forming an electronic component member according to the present invention includes an etching process step of etching using a copper or copper alloy material etchant containing a cupric ion source, a halogen ion source, and an organic acid as a main component, A plating treatment step of forming tin and a tin alloy plating film on the copper or copper alloy material roughened in the etching treatment step.
また、錫及び錫合金めっき後に熱処理やリフロー処理を施す技術の場合には、その熱処理やリフロー処理により錫及び錫合金めっき皮膜上に酸化皮膜が形成され、はんだ濡れ性の低下等の錫及び錫合金めっき皮膜の劣化が生じてしまう。また、リフロー処理の場合には、溶融した錫及び錫合金めっき皮膜が流動して、膜厚にばらつきが生じる。さらに、これらの熱処理やリフロー処理を行う場合には、めっき処理後に新たな設備を用意して処理する必要があり、設備コストや処理時間の増加をもたらす。
さらに、Sn-Cu、Sn-Ag、Sn-Bi等の錫合金めっき皮膜を形成させることによって、錫めっき皮膜を形成させた場合に比べてウィスカの抑制効果は向上するものの、皮膜中の合金比率やめっき液中の合金比率を管理することが非常に困難なため、品質が安定しないという問題がある。
またさらに、従来より、錫及び錫合金めっき皮膜と素材との密着性の向上を目的に、めっき処理の前工程にエッチング処理が実施されており、一般的に銅、銅合金材のエッチング液として硫酸と過酸化水素水を主成分とした薬液が多く使用されている。しかしながら、その硫酸と過酸化水素水を主成分とするエッチング液は、主に銅及び銅合金材の表面の酸化皮膜や加工変質層の除去を目的として使用されるものであり、銅及び銅合金材の表面に対して使用しても、なだらかで平滑な形状にしかならない。その結果、やはり銅-錫金属間化合物層が、銅及び銅合金材と錫及び錫合金めっき皮膜との界面に局部的に発生し、めっき皮膜に応力を生じさせてしまうこととなり、ウィスカの発生を抑制することはできない。
このように、錫及び錫合金めっき皮膜の形成に伴って発生するウィスカの抑制には、これまで種々の対策が試みられてきたが、十分な効果を発揮する技術は未だ開発されていない。したがって、錫及び錫合金めっき皮膜の性能を損なうことなく、効果的にウィスカの発生を抑制するウィスカ抑制方法の開発が強く望まれている。
本発明は、これらの従来技術の問題点並びに要請に鑑みてなされたものであり、錫及び錫合金めっき皮膜の性能を低下させることなく、錫及び錫合金めっき皮膜上に発生するウィスカを効果的に抑制し、接続性等に関する信頼性の低下を防止することができる銅又は銅合金材用エッチング液、めっき前処理方法、並びに電子部品用部材の形成方法を提供することを目的とする。
課題を解決するための手段
本発明者らは、上記課題を解決するために鋭意検討を重ねた結果、錫及び錫合金めっき処理のめっき前表面処理工程において、第二銅イオン源、ハロゲンイオン源、有機酸を主成分とする銅又は銅合金材用エッチング液を用いて銅又は銅合金材の表面を粗化する錫及び錫合金めっき前処理を行い、表面粗さが大きくかつ微細な凹凸形状とすることで、錫及び錫合金めっき皮膜から発生するウィスカを効果的に抑制することができることを見出した。
すなわち、本発明に係る銅又は銅合金材用エッチング液は、錫及び錫合金めっき皮膜上に発生するウィスカを抑制するために、銅又は銅合金材の表面に使用されるエッチング液であって、第二銅イオン源と、ハロゲンイオン源と、有機酸とを主成分とする。
また、本発明に係るめっき前処理方法は、錫及び錫合金めっき皮膜上に発生するウィスカを抑制させるための銅又は銅合金材表面のめっき前処理方法であって、第二銅イオン源と、ハロゲンイオン源と、有機酸とを主成分とする銅又は銅合金材用エッチング液を用いて、上記銅又は銅合金材の表面をエッチング処理して粗化する。
また、本発明に係る電子部品用部材の形成方法は、第二銅イオン源、ハロゲンイオン源、有機酸を主成分とする銅又は銅合金材用エッチング液を用いてエッチングするエッチング処理工程と、上記エッチング処理工程にて粗化された銅又は銅合金材に対して錫及び錫合金めっき皮膜を形成させるめっき処理工程とを有する。 However, with the technology for forming a nickel plating film as the base and the technology for increasing the thickness of the tin and tin alloy plating film, the effect of suppressing the whisker is not sufficient, and there are parts that cannot be nickel plated due to necessary characteristics. In some cases, or when there is a part that cannot be thickened, it cannot be applied.
In addition, in the case of a technique for performing heat treatment or reflow treatment after tin and tin alloy plating, an oxide film is formed on the tin and tin alloy plating film by the heat treatment or reflow treatment, and tin and tin such as a decrease in solder wettability. Degradation of the alloy plating film occurs. Further, in the case of the reflow treatment, the molten tin and tin alloy plating film flow and the film thickness varies. Furthermore, when performing these heat treatments and reflow treatments, it is necessary to prepare and treat new equipment after the plating treatment, resulting in an increase in equipment costs and treatment time.
Furthermore, by forming a tin alloy plating film such as Sn—Cu, Sn—Ag, Sn—Bi, etc., the whisker suppression effect is improved as compared with the case where a tin plating film is formed, but the alloy ratio in the film In addition, since it is very difficult to control the alloy ratio in the plating solution, there is a problem that the quality is not stable.
Furthermore, conventionally, an etching process has been carried out in the pre-plating process for the purpose of improving the adhesion between the tin and tin alloy plating film and the material, and generally as an etching solution for copper and copper alloy materials. Many chemicals mainly composed of sulfuric acid and hydrogen peroxide are used. However, the etching solution mainly composed of sulfuric acid and hydrogen peroxide water is mainly used for the purpose of removing an oxide film or a work-affected layer on the surface of copper and copper alloy material. Even if it is used on the surface of a material, it has only a smooth and smooth shape. As a result, the copper-tin intermetallic compound layer is also locally generated at the interface between the copper and copper alloy material and the tin and tin alloy plating film, causing stress to the plating film, and the generation of whiskers. Can not be suppressed.
As described above, various countermeasures have been tried to suppress whiskers generated with the formation of the tin and tin alloy plating film, but a technique that exhibits a sufficient effect has not yet been developed. Therefore, the development of a whisker suppression method that effectively suppresses the generation of whiskers without impairing the performance of the tin and tin alloy plating film is strongly desired.
The present invention has been made in view of the problems and demands of these prior arts, and effectively reduces whiskers generated on the tin and tin alloy plating film without degrading the performance of the tin and tin alloy plating film. It is an object of the present invention to provide an etching solution for copper or a copper alloy material, a plating pretreatment method, and a method for forming a member for an electronic component, which can suppress the decrease in reliability related to connectivity and the like.
Means for Solving the Problems As a result of intensive studies in order to solve the above problems, the present inventors have found that a cupric ion source, a halogen ion source in the pre-plating surface treatment step of tin and tin alloy plating treatment The surface of the copper or copper alloy material is roughened using an etching solution for copper or copper alloy material containing organic acid as a main component, and tin and tin alloy plating pretreatment is performed, and the surface roughness is large and fine uneven shape It has been found that whiskers generated from tin and tin alloy plating film can be effectively suppressed.
That is, the etching solution for copper or copper alloy material according to the present invention is an etching solution used on the surface of copper or copper alloy material in order to suppress whisker generated on tin and tin alloy plating film, The main component is a cupric ion source, a halogen ion source, and an organic acid.
Moreover, the plating pretreatment method according to the present invention is a plating pretreatment method for copper or a copper alloy material surface for suppressing whisker generated on a tin and tin alloy plating film, and a second copper ion source, The surface of the said copper or copper alloy material is etched and roughened using the etching solution for copper or copper alloy material which has a halogen ion source and an organic acid as a main component.
Moreover, the method for forming an electronic component member according to the present invention includes an etching process step of etching using a copper or copper alloy material etchant containing a cupric ion source, a halogen ion source, and an organic acid as a main component, A plating treatment step of forming tin and a tin alloy plating film on the copper or copper alloy material roughened in the etching treatment step.
以下、本実施の形態に係る、錫及び錫合金めっき皮膜上に発生するウィスカを抑制するため銅又は銅合金用エッチング液、並びにそのエッチング液を用いためっき前処理方法について詳細に説明する。
本発明に係る銅又は銅合金材用エッチング液は、錫及び錫合金めっき皮膜の形成に伴って発生するウィスカを抑制させることを目的として、めっき処理前のエッチング処理に使用されるエッチング液である。電子部品用部材であるリードフレーム等の銅又は銅合金材に対し、電解脱脂処理や酸洗処理等の通常の所定の表面処理を施した後に、このエッチング液を用いて銅又は銅合金材表面をエッチング処理し、表面粗さが大きくかつ微細な凹凸を形成させる。そして、その後、錫及び錫合金めっき処理を施すことによってめっき皮膜を形成し、電子部品用部材を形成させる。
ここで、本実施の形態に係る銅及び銅合金材料としては、少なくともその表面が銅又は銅合金で形成されているものや、又はリードフレーム等のように全体が銅又は銅合金で形成されているものが挙げられる。また、少なくともその表面が銅又は銅合金で形成されているものとしては、絶縁樹脂表面に銅(銅合金)が積層されているものも含む。
先ず、本実施の形態に係る、めっき前エッチング表面処理に使用される銅又は銅合金材用エッチング液について説明する。このエッチング液は、第二銅イオン源、ハロゲンイオン源、有機酸を主成分としている。
第二銅イオン源としては、塩化銅(II)、臭化銅(II)、水酸化銅(II)や、酢酸銅(II)、ギ酸銅(II)等の有機酸の銅塩等を用いることができ、これらの第二銅イオン源は、1種単独で用いてもよく、又は2種以上を任意の割合で併用してもよい。
この第二銅イオン源の含有量としては、2~50g/L、好ましくは、5~25g/Lである。第二銅イオン源の含有量が、2g/L未満の場合ではエッチング速度が低下してしまい、また50g/Lより多い場合ではウィスカ抑制の効果の向上が見られない。
ハロゲンイオン源としては、塩素イオン、臭素イオン等のイオン源であり、例えば塩酸、塩化ナトリウム、塩化カリウム、塩化カルシウム、塩化アンモニウム、臭化カリウム、臭化水素酸、塩化銅、塩化亜鉛、塩化鉄、臭化鉄、臭化錫、臭化銅等の、溶液中でハロゲンイオンを解離し得る化合物を用いることができる。これらのハロゲンイオン源は、1種単独で用いてもよく、又は2種以上を任意の割合で併用してもよい。なお、例えば塩化銅(II)は、ハロゲンイオン源と、上述した第二銅イオン源の両方の作用を有するものとして使用することができる。
このハロゲンイオン源の含有量としては、5~200g/L、好ましくは10~150g/Lである。ハロゲンイオン源の含有量が、5g/L未満の場合ではエッチング速度が低下してしまい、また200g/Lより多い場合ではウィスカ抑制の効果の向上が見られない。
有機酸としては、ギ酸、酢酸、プロピオン酸、酪酸、吉草酸、カプロン酸、ステアリン酸等の飽和脂肪族モノカルボン酸、シュウ酸、マロン酸、コハク酸、グルタル酸、アジピン酸、セバシン酸等の飽和脂肪族ジカルボン酸、アクリル酸、プロピオール酸、クロトン酸、オレイン酸、メタクリル酸等の不飽和脂肪族モノカルボン酸、マレイン酸、フマル酸等の不飽和脂肪族ジカルボン酸、安息香酸、フタル酸、桂皮酸等の炭素環カルボン酸、チオフェンカルボン酸、ニコチン酸等の複素環カルボン酸、グリコール酸、乳酸、ロイシン酸、リンゴ酸、酒石酸、グルコン酸、クエン酸等の脂肪族ヒドロキシ酸、サリチル酸、バニリン酸、没食子酸等の芳香族ヒドロキシ酸が挙げられる。これらの有機酸は、1種単独で用いてもよく、又は2種以上を任意の割合で併用してもよい。
有機酸の含有量としては、5~300g/L、好ましくは10~200g/Lである。有機酸の含有量が、5g/L未満の場合ではエッチング速度が低下してしまい、また300g/Lより多い場合では、ウィスカ抑制効果の更なる向上は認められず、不経済である。
このように、本実施の形態に係る銅及び銅合金材用エッチング液は、第二銅イオン源、ハロゲンイオン源、有機酸を主成分としており、このエッチング液を用いて錫及び錫合金めっき処理の前処理として銅又は銅合金表面に対してエッチング処理を施す。これにより、従来から使用されていたエッチング液に比べて、銅又は銅合金材に形成される凹凸形状(表面粗さ)を大きく、かつ微細に形成させることが可能となり、ウィスカの発生を効果的に抑制させることができる。
すなわち、これまでの通常のエッチング液を用いてエッチング処理した錫及び錫合金めっき皮膜では、そのめっき皮膜の粒界に沿って局部的に銅-錫金属間化合物層が形成されていた。これに対し、上述した本実施の形態に係るエッチング液を使用してエッチング処理を施した錫及び錫合金めっき皮膜では、このエッチング処理によって、銅又は銅合金材上に表面粗さが大きくかつ微細な凹凸形状が形成されることになり、金属間化合物層が界面全面にほぼ均一に形成されるようになる。これにより、錫めっき皮膜内の応力が界面全体分散され、局部的に集中することがなくなり、その結果、ウィスカの発生が抑制される。
また、本実施の形態に係るエッチング液には、ポリアミン化合物、及びポリビニル化合物のうちの何れか1種以上をさらに含有させることができる。具体的には、ポリアミン化合物としては、例えばポリエチレンイミン、ポリアルキレンポリアミン等を用いることができる。また、ポリビニル化合物としては、例えばポリビニルピロリドン、ポリビニルアルコール等を用いることができる。なお、これらのポリアミン化合物、及びポリビニル化合物は、1種単独で用いてもよく、又は2種以上を任意の割合で併用してもよい。
これらのポリアミン化合物、及びポリビニル化合物の含有量としては、0.0001~10g/L、好ましくは0.0005~5g/Lである。含有量が、0.0001g/L未満の場合では添加によるウィスカ抑制効果が得られず、また10g/Lより多い場合では添加によるウィスカ抑制効果の向上が見られないだけでなく、エッチング速度が低下する。
このようにして、第二銅イオン源、ハロゲンイオン源、有機酸を主成分とするエッチング液に、ポリアミン化合物、及びポリビニル化合物のうちの何れか1種以上をさらに含有させることによって、銅又は銅合金材に対して、より表面粗さの大きく、かつ微細な凹凸形状を形成させることができる。そして、これにより、応力の局部的な集まりを防止して、より効果的にウィスカの発生を抑制させることができる。
すなわち、ポリアミン化合物やポリビニル化合物を含有させることにより、これらの化合物が銅又は銅合金材の表面に不連続に吸着して孔食状態を作りだすものと考えられる。そして、ポリアミン化合物やポリビニル化合物が吸着した部位と吸着しなかった部位とで、エッチング量に差が生じ、それが凹凸となって表れるものと推測される。これによって、銅又は銅合金材の表面に、より表面粗さが大きく、かつ微細な凹凸を形成させることができることになる。
エッチング未処理の場合や従来のエッチング液で処理した場合には、上述したように、銅が錫めっき皮膜の表面に向かって一方向に拡散するとともに、錫めっき皮膜の粒界に集中するため、銅又は銅合金材と錫めっき皮膜との界面に不均一な金属間化合物層を形成させる。そして、この不均一な金属間化合物層が形成されることにより、錫めっき皮膜の内部に応力を生じさせる結果、ウィスカが発生することとなっていた。
しかしながら、本実施の形態のように、ポリアミン化合物やポリビニル化合物を含有させ、より表面粗さが大きく、かつ微細な凹凸を形成させることで、銅又は銅合金材と錫めっき皮膜との接触面積が増え、また銅の拡散方向が一方向とならずランダムにすることができる。銅又は銅合金材と錫めっき皮膜との接触面積が増えると、銅の拡散の駆動力が分散して、錫めっき皮膜の粒界への拡散が集中することを抑制させる、換言すると粒界への供給量を減少させる。また、銅の拡散が一方向ではなくランダムとなることで、より平滑化された均一な金属間化合物層が形成されることになる。その結果、錫めっき皮膜の内部に応力が生じ難くなり、ウィスカの発生を抑制することができると推測される。
本実施の形態に係るエッチング液には、さらに、第二鉄イオン源、亜鉛イオン源、及びニッケルイオン源のうちの何れか1種以上を含有させることもできる。
具体的に、第二鉄イオン源としては、例えば塩化鉄(III)、臭化鉄(III)、ヨウ化鉄(III)、硫酸鉄(III)、硝酸鉄(III)、酢酸鉄(III)、クエン酸鉄(III)アンモニウム等を用いることができる。また、亜鉛イオン源としては、塩化亜鉛(II)、臭化亜鉛(II)、ヨウ化亜鉛(II)、硫酸亜鉛(II)、硝酸亜鉛(II)、酢酸亜鉛(II)、ギ酸亜鉛(II)、シュウ酸亜鉛(II)等を用いることができる。また、ニッケルイオン源としては、塩化ニッケル(II)、臭化ニッケル(II)、ヨウ化ニッケル(II)、硫酸ニッケル(II)、硝酸ニッケル(II)、酢酸ニッケル(II)、ギ酸ニッケル(II)、スルファミン酸ニッケル(II)、シュウ酸ニッケル(II)等を用いることができる。
これらの第二鉄イオン源、亜鉛イオン源、及びニッケルイオン源は、1種単独で用いてもよく、又は2種以上を任意の割合で併用してもよい。なお、これらの化合物の含有量としては、0.00005~0.005g/L、好ましくは0.0001~0.002g/Lである。含有量が、0.00005g/L未満の場合では添加による効果が得られず、また0.005g/Lより多い場合では効果の向上が見られない。
このようにして、第二銅イオン源、ハロゲンイオン源、有機酸を主成分とするエッチング液に、さらに第二鉄イオン源、亜鉛イオン源、及びニッケルイオン源のうちの何れか1種以上をさらに含有させることによって、めっき液中の銅イオン濃度の変動によるエッチング速度の低下を抑制することができる。また、効率的なエッチング処理を行うことが可能となり、より効果的にウィスカの発生を抑制させることができる。
なお、本実施の形態に係るエッチング剤は、さらに種々の添加剤を含有させることができる。例えば、pHの変動を抑えて安定したエッチング処理を実施することができるように、公知のpH安定化剤を含有させることができる。なお、添加剤としては、これに限られるものではなく、その他種々の添加剤を含有させるようにしてもよい。
このような本実施の形態に係るエッチング液を用いてエッチング処理を施すことにより、リードフレーム等の銅又は銅合金材の表面に、表面粗さが大きく、かつ微細な凹凸形状(表面粗さ)を形成させることができる。そして、これにより銅又は銅合金材と錫及び錫合金めっき皮膜との間に形成される銅-錫金属間化合物層を界面全体に略均一に形成させ、応力が局部的な集中することを防止して、局部的な応力集中を緩和させるために発生するウィスカを効果的に抑制させることができる。
次に、上述したエッチング液を用いたエッチング処理方法について説明する。本実施の形態においては、銅又は銅合金材に対して錫及び錫合金めっき処理を施す前に、めっき前処理として上述したエッチング液を用い、銅又は銅合金材の表面を粗化するエッチング処理を施すようにしている。
すなわち、銅又は銅合金材に対して、公知の脱脂処理、酸洗処理等の所定のクリーニング処理を行った後に、上述した銅又は銅合金材用エッチング液を用いて、錫及び錫合金めっき前処理としてのエッチング処理を施して、表面粗さが大きく、かつ微細な凹凸形状を銅又は銅合金材の表面に形成する。その後、エッチング処理によって表面が粗化された銅又は銅合金材に対して、錫及び錫合金めっき処理を施す。
このエッチング処理としては、公知の方法を用いて行うことができ、例えば銅又は銅合金材を上述したエッチング液に浸漬させて、又はそのエッチング液をスプレー方式により接触させることによって、エッチング処理を行う。また、通電可能な銅又は銅合金材の場合には電解処理による電解エッチングも可能である。
エッチング処理の処理時間は、特に限定されないが、例えば、1~300秒、好ましくは5~200秒で処理する。
また、エッチング液の温度条件としては、特に限定されないが、例えば、10~80℃、好ましくは25~50℃とする。
このエッチング処理によって、銅又は銅合金材の表面に、表面粗さが大きく、かつ微細な凹凸形状を形成させる。具体的には、銅又は銅合金材の表面に、Ra値で0.2μm以上の凹凸を形成させることが好ましい。なお、本説明における平均粗さRaとは、JIS B 0601-1994によって定義される「算術平均粗さRa」と同様のものであり、具体的には、粗さ曲線からその平均線の方向に一定の基準長さを抜き取り、この抜き取り部分の平均線から粗さ曲線までの偏差の絶対値を合計し、平均することにより求められる。
このように、本実施の形態においては、錫及び錫合金めっき前処理として、上述したエッチング液を用いて銅又は銅合金材の表面にRa値0.2μm以上の大きく、かつ微細な凹凸形状を形成させる。これによって、その後のめっき処理によって形成される錫めっき皮膜と銅又は銅合金材の界面に生じる金属間化合物層を、その界面全体に略均一に形成させ、応力の局部的な集中を抑制することができる。その結果、応力の集中的な発生によって形成されるウィスカを抑制することができる。
また、錫及び錫合金めっき前処理としてのエッチング処理において、銅又は銅合金材の表面に、表面粗さが大きくかつ微細な凹凸形状を形成させてウィスカの発生を抑制しているので、その後のめっき処理によって形成させた錫及び錫合金めっき皮膜のはんだ濡れ性や、銅又は銅合金材と錫及び錫合金めっき皮膜との密着性に影響を及ぼすことがない。このように、錫及び錫合金めっき皮膜の性能を低下させずに、効果的にウィスカの発生を抑制することができる。
このようにして、上述したエッチング液を用いてめっき前処理としてのエッチング処理を施し、表面に表面粗さが大きく微細な凹凸形状が形成させると、次にその銅又は銅合金表面に錫及び錫合金めっき処理を施す。この錫及び錫合金めっき処理は、公知のめっき方法・条件を適用することができ、特に限定はされるものではない。
錫及び錫合金めっき処理条件としては、特に限定されるものではないが、例えば、めっき液の温度としては、15~55℃とし、めっき時間としては所望とするめっき膜厚により変化させることが好ましい。
本実施の形態においては、上述したように、銅又は銅合金材の表面に第二銅イオン源、ハロゲンイオン源、有機酸を主成分とするエッチング液を用いて、めっき前処理としてのエッチング処理を行い、銅又は銅合金材の表面に凹凸形状を形成させる。そしてその後、錫及び錫合金めっき処理によって錫めっき皮膜を形成することによって、電子部品用部材を形成させる。このようにして形成された電子部品用部材は、短絡等の原因となるウィスカの発生がなく、またはんだ濡れ性等のめっき皮膜の性能を維持した状態となっている。
以上、詳細に説明したように、本実施の形態に係るエッチング液は、第二銅イオン源、ハロゲンイオン源、有機酸を主成分とし、このエッチング液を用いて錫及び錫合金めっき処理の前処理として銅又は銅合金表面に対してエッチング処理を施す。このエッチング処理により、銅又は銅合金材に形成される凹凸形状(表面粗さ)を大きく、かつ微細に形成させることが可能となり、ウィスカの発生をより効果的に抑制させることができる。
すなわち、このエッチング処理により形成される、表面粗さが大きく、微細な凹凸形状により、銅素材と錫及び錫合金めっき皮膜との界面に生じる金属間化合物層を界面全体に略均一に形成させることで、錫めっき皮膜内の応力が局部的に集中することを抑制することができる。その結果、この錫及び錫合金めっき皮膜に発生した応力を緩和させるために発生するウィスカを抑制させることができる。
また、従来のように、めっき皮膜に対して熱処理やリフロー処理を施してウィスカの発生を抑制するのではなく、めっき前処理として上述したエッチング液を用いたエッチング処理により、ウィスカの発生を抑制させているので、熱処理やリフロー処理の実施によって生じるはんだ濡れ性の低下等の錫及び錫合金めっき皮膜の劣化を防止し、電子部品用部材の性能を維持することができる。そして、このように、はんだ濡れ性を劣化させることがないため、リードフレーム上に錫又は錫合金めっき皮膜を形成させるような、基体上の被はんだ接合部に錫又は錫合金めっき皮膜を形成させる場合においても、効果的に適用することができる。
さらに、錫及び錫合金めっき処理の前処理工程にてエッチング処理を行うのみで効果的にウィスカを抑制することができることから、処理工程数の増加や特別な設備の増設の必要がなく、容易にかつ効果的にウィスカの発生を抑制させるとともに、接続不良等のない信頼性の向上した良好な電子部品用部材を形成することができる。
なお、本発明は、上述した実施の形態に限られるものではなく、発明の要旨を逸脱しない範囲での設計変更等があっても本発明に含まれる。また、上述した本実施の形態に係るエッチング液に含有される種々の化合物は、適用することができる一例を示したものであり、上記列挙したものに限られるものでない。
実施例
以下、本発明の実施例について説明する。なお、本発明に係る銅又は銅合金用のエッチング液、並びにそのエッチング液を用いたエッチング処理方法は、下記の実施例に限定されるものではない。
(実施例1~8)
実施例として、銅合金材(C194)リードフレーム(表面積:0.245dm2)を、下記表1の示す実施例1~8の組成からなるエッチング液を用いて浸漬方法でエッチング処理した後、下記に示す組成からなる錫めっき浴を用いて錫めっき処理を施して評価試料とした。
処理を施した評価試料は、30℃-60%RHに保持した恒温槽内に保管し、4000時間経過後に走査電子顕微鏡(SEM)により、形成した錫めっき皮膜上のウィスカを観察した。
また、評価試験においては、エッチング処理後の表面粗さ(Ra)及び凹凸平均間隔(Sm)についてもレーザー顕微鏡観察により測定した。測定方法としては、超深度形状測定顕微鏡(株式会社キーエンス製 VK-8550)を用い、エッチング処理後の銅合金材の各試料あたり3点を測定し、平均値を測定した。なお、本実施例において測定した凹凸平均間隔(Sm)とは、JIS B 0601-1994によって規定されている「凹凸の平均間隔」であり、具体的には、粗さ曲線から、その平均線の方向に一定の基準長さだけ抜き取り、1つの山及びそれに隣り合う1つの谷に対応する平均線の長さの和を求め、平均値を表したものである。Smが小さいと凹凸の目が細かいと判断される。
<処理工程>
電解脱脂(2分)→水洗(15秒)×3回→酸洗(20秒)→水洗(15秒)×3回→エッチング(浸漬処理)→水洗(15秒)×3回→酸洗(20秒)→錫めっき(下記条件)→水洗(15秒)×3回→中和→水洗(15秒)×3回→イオン交換水洗→乾燥
<錫めっき浴の組成>
メタンスルホン酸錫(II):90g/L(Snとして50g/L)
70%メタンスルホン酸:135g/L
界面活性剤;ポリオキシエチレンノニルフェニルエーテル(EO付加モル数9):6g/L
<錫めっき処理条件>
陰極電流密度:10A/dm2
めっき時間:35秒
液温:45℃
めっき膜厚:2.5μm
(比較例1)
また、比較例1として、実施例で用いたものと同様の銅合金材(C194)リードフレーム(表面積:0.245dm2)に対し、錫めっき処理前にエッチング処理を行わずに、実施例と同様の上記錫めっき浴を用いて錫めっき処理を行った。
そして、実施例と同様にして、錫めっき処理を施した試料を30℃-60%RHに保持した恒温槽内に保管し、4000時間経過後に走査電子顕微鏡(SEM)により、形成した錫めっき皮膜上のウィスカを観察した。
(比較例2~8)
また、比較例2~8として、銅合金材(C194)リードフレーム(表面積:0.245dm2)に対し、下記表2の示す比較例2~8の組成からなるエッチング液を用いて、実施例と同様にして浸漬方法でエッチング処理した後、上記と同様の組成からなる錫めっき浴を用いて錫めっき処理を施して評価試料とした。
そして、実施例と同様にして、処理を施した評価試料は、30℃-60%RHに保持した恒温槽内に保管し、4000時間経過後に走査電子顕微鏡(SEM)により、形成した錫めっき皮膜上のウィスカを観察した。また、エッチング処理後の表面粗さ(Ra)及び凹凸平均間隔(Sm)についても、超深度形状測定顕微鏡(株式会社キーエンス製 VK-8550)を用い、エッチング処理後の銅又は銅合金材の各試料あたり3点を測定し、平均値を測定した。なお、この表面粗さ(Ra)及び凹凸平均間隔(Sm)に関しては、錫めっき処理前の比較例1におけるリードフレームについても測定した。
(測定結果)
下記の表1及び表2に、実施例及び比較例の測定結果を示す。なお、表1及び表2において、ウィスカ評価結果の欄に記してある『○』、『△』、『×』は以下のことを意味する。
○:ウィスカの発生ゼロ
△:ウィスカは観察されたが、その長さが10μm未満
×:ウィスカが観察され、その長さは10μm以上
また、図1に、実施例1及び実施例3の処理において、リードフレームに対してエッチング処理を施して凹凸形状を形成させたときの表面状態の示すSEM像を示し(図1A:実施例1、図1B:実施例3)、さらに図2に、比較例2及び比較例3の処理において、リードフレームに対してエッチング処理を施して凹凸形状を形成させたときの表面状態の示すSEM像を示す(図2A:比較例2、図2B:比較例3)。
(実施例1~8) Hereinafter, the copper or copper alloy etching solution for suppressing whiskers generated on the tin and tin alloy plating film and the plating pretreatment method using the etching solution according to the present embodiment will be described in detail.
The etching solution for copper or copper alloy material according to the present invention is an etching solution used for etching treatment before plating treatment for the purpose of suppressing whiskers generated with the formation of tin and tin alloy plating film. . Copper or copper alloy material such as a lead frame that is a member for electronic parts is subjected to usual predetermined surface treatment such as electrolytic degreasing treatment or pickling treatment, and then the surface of copper or copper alloy material using this etching solution Is etched to form fine irregularities with a large surface roughness. Then, a plating film is formed by performing a tin and tin alloy plating treatment, and an electronic component member is formed.
Here, as the copper and copper alloy material according to the present embodiment, at least the surface thereof is formed of copper or a copper alloy, or the whole is formed of copper or a copper alloy such as a lead frame. The thing that is. Moreover, what has copper (copper alloy) laminated | stacked on the surface of an insulating resin is also included as what the surface is formed with copper or a copper alloy.
First, the etching solution for copper or copper alloy material used for the pre-plating etching surface treatment according to the present embodiment will be described. This etching solution contains a cupric ion source, a halogen ion source, and an organic acid as main components.
As the cupric ion source, copper salts of organic acids such as copper (II) chloride, copper (II) bromide, copper hydroxide (II), copper acetate (II), copper formate (II) and the like are used. These cupric ion sources may be used alone or in combination of two or more at any ratio.
The content of the cupric ion source is 2 to 50 g / L, preferably 5 to 25 g / L. When the content of the cupric ion source is less than 2 g / L, the etching rate is reduced, and when it is more than 50 g / L, no improvement in whisker suppression effect is observed.
The halogen ion source is an ion source such as chloride ion or bromide ion, for example, hydrochloric acid, sodium chloride, potassium chloride, calcium chloride, ammonium chloride, potassium bromide, hydrobromic acid, copper chloride, zinc chloride, iron chloride. , Iron bromide, tin bromide, copper bromide, and the like can be used. These halogen ion sources may be used individually by 1 type, or may use 2 or more types together in arbitrary ratios. Note that, for example, copper (II) chloride can be used as having both functions of the halogen ion source and the above-described cupric ion source.
The content of the halogen ion source is 5 to 200 g / L, preferably 10 to 150 g / L. When the content of the halogen ion source is less than 5 g / L, the etching rate decreases, and when it is more than 200 g / L, no improvement in whisker suppression effect is observed.
Examples of organic acids include saturated aliphatic monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, and stearic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and sebacic acid. Saturated aliphatic dicarboxylic acid, acrylic acid, propiolic acid, crotonic acid, oleic acid, methacrylic acid and other unsaturated aliphatic monocarboxylic acids, maleic acid, fumaric acid and other unsaturated aliphatic dicarboxylic acids, benzoic acid, phthalic acid, Carboxylic carboxylic acids such as cinnamic acid, heterocyclic carboxylic acids such as thiophene carboxylic acid and nicotinic acid, aliphatic hydroxy acids such as glycolic acid, lactic acid, leucine acid, malic acid, tartaric acid, gluconic acid and citric acid, salicylic acid and vanillin Aromatic hydroxy acids such as acid and gallic acid can be mentioned. These organic acids may be used individually by 1 type, or may use 2 or more types together by arbitrary ratios.
The organic acid content is 5 to 300 g / L, preferably 10 to 200 g / L. When the content of the organic acid is less than 5 g / L, the etching rate is reduced, and when it is more than 300 g / L, no further improvement in the whisker suppressing effect is observed, which is uneconomical.
As described above, the copper and copper alloy material etching solution according to the present embodiment is mainly composed of a cupric ion source, a halogen ion source, and an organic acid, and tin and tin alloy plating treatment is performed using this etching solution. As a pretreatment, an etching process is performed on the copper or copper alloy surface. As a result, it is possible to make the uneven shape (surface roughness) formed on the copper or copper alloy material larger and finer than the etching solution that has been used in the past, and the generation of whiskers is effective. Can be suppressed.
That is, in the tin and tin alloy plating film etched using a conventional etching solution, a copper-tin intermetallic compound layer is locally formed along the grain boundary of the plating film. In contrast, in the tin and tin alloy plating film that has been etched using the etching solution according to the present embodiment described above, the surface roughness is large and fine on the copper or copper alloy material by this etching process. Thus, an uneven shape is formed, and the intermetallic compound layer is formed almost uniformly over the entire interface. Thereby, the stress in a tin plating film is disperse | distributed the whole interface, and it does not concentrate locally, As a result, generation | occurrence | production of a whisker is suppressed.
Moreover, the etching liquid which concerns on this Embodiment can further contain any 1 or more types of a polyamine compound and a polyvinyl compound. Specifically, as the polyamine compound, for example, polyethyleneimine, polyalkylene polyamine, or the like can be used. Moreover, as a polyvinyl compound, polyvinyl pyrrolidone, polyvinyl alcohol, etc. can be used, for example. In addition, these polyamine compounds and polyvinyl compounds may be used individually by 1 type, or may use 2 or more types together in arbitrary ratios.
The content of these polyamine compounds and polyvinyl compounds is 0.0001 to 10 g / L, preferably 0.0005 to 5 g / L. When the content is less than 0.0001 g / L, the effect of suppressing whisker by addition cannot be obtained, and when the content is more than 10 g / L, not only the improvement of whisker suppression effect by addition is not seen, but also the etching rate decreases. To do.
In this way, copper or copper can be obtained by further containing any one or more of a polyamine compound and a polyvinyl compound in an etching solution mainly composed of a cupric ion source, a halogen ion source, and an organic acid. With respect to the alloy material, it is possible to form a fine uneven shape with a larger surface roughness. And thereby, the local gathering of stress can be prevented and generation | occurrence | production of a whisker can be suppressed more effectively.
That is, it is thought that by containing a polyamine compound or a polyvinyl compound, these compounds adsorb discontinuously on the surface of the copper or copper alloy material to create a pitting corrosion state. And it is estimated that there is a difference in the etching amount between the portion where the polyamine compound or polyvinyl compound is adsorbed and the portion where the polyamine compound or polyvinyl compound is not adsorbed, which appears as irregularities. Thereby, the surface roughness of copper or a copper alloy material can be made larger and fine irregularities can be formed.
When not etched or treated with a conventional etching solution, as described above, copper diffuses in one direction toward the surface of the tin plating film and concentrates on the grain boundaries of the tin plating film. A non-uniform intermetallic compound layer is formed at the interface between the copper or copper alloy material and the tin plating film. The formation of this non-uniform intermetallic compound layer causes stress in the tin plating film, resulting in the generation of whiskers.
However, as in this embodiment, the contact area between the copper or copper alloy material and the tin plating film is increased by including polyamine compound or polyvinyl compound, forming a larger unevenness with finer surface roughness. In addition, the copper diffusion direction does not become one direction but can be made random. When the contact area between the copper or copper alloy material and the tin plating film increases, the driving force of the copper diffusion is dispersed and the diffusion of the tin plating film to the grain boundary is suppressed, in other words, to the grain boundary. Reduce the amount of supply. Further, since copper diffusion is random rather than unidirectional, a smoother and uniform intermetallic compound layer is formed. As a result, it is presumed that stress is less likely to occur inside the tin plating film, and the occurrence of whiskers can be suppressed.
The etching solution according to the present embodiment may further contain any one or more of a ferric ion source, a zinc ion source, and a nickel ion source.
Specifically, as the ferric ion source, for example, iron (III) chloride, iron (III) bromide, iron (III) iodide, iron (III) sulfate, iron (III) nitrate, iron (III) acetate Further, iron (III) ammonium citrate and the like can be used. The zinc ion source includes zinc chloride (II), zinc bromide (II), zinc iodide (II), zinc sulfate (II), zinc nitrate (II), zinc acetate (II), zinc formate (II ), Zinc oxalate (II) and the like can be used. Nickel ion sources include nickel chloride (II), nickel bromide (II), nickel iodide (II), nickel sulfate (II), nickel nitrate (II), nickel acetate (II), nickel formate (II). ), Nickel sulfamate (II), nickel oxalate (II), and the like.
These ferric ion sources, zinc ion sources, and nickel ion sources may be used singly or in combination of two or more at any ratio. The content of these compounds is 0.00005 to 0.005 g / L, preferably 0.0001 to 0.002 g / L. When the content is less than 0.00005 g / L, the effect of addition cannot be obtained, and when the content is more than 0.005 g / L, no improvement in effect is observed.
In this way, any one or more of a ferric ion source, a zinc ion source, and a nickel ion source is added to the etching liquid mainly composed of a cupric ion source, a halogen ion source, and an organic acid. Furthermore, by making it contain, the fall of the etching rate by the fluctuation | variation of the copper ion concentration in a plating solution can be suppressed. In addition, an efficient etching process can be performed, and the generation of whiskers can be more effectively suppressed.
Note that the etching agent according to the present embodiment can further contain various additives. For example, a known pH stabilizer can be contained so that a stable etching process can be performed while suppressing fluctuations in pH. In addition, as an additive, it is not restricted to this, You may make it contain other various additives.
By performing an etching process using the etching solution according to this embodiment, the surface of a copper or copper alloy material such as a lead frame has a large surface roughness and a fine uneven shape (surface roughness). Can be formed. As a result, a copper-tin intermetallic compound layer formed between the copper or copper alloy material and the tin and tin alloy plating film is formed substantially uniformly over the entire interface, thereby preventing stress from being concentrated locally. Thus, it is possible to effectively suppress whiskers generated to alleviate local stress concentration.
Next, an etching method using the above-described etching solution will be described. In this embodiment, before performing tin and tin alloy plating treatment on copper or copper alloy material, the etching solution described above is used as a pretreatment for plating, and the etching treatment for roughening the surface of copper or copper alloy material. To give.
That is, after performing a predetermined cleaning process such as a known degreasing process or pickling process on copper or a copper alloy material, before the tin or tin alloy plating using the above-described etching solution for copper or copper alloy material Etching treatment as a treatment is performed to form a fine uneven shape on the surface of the copper or copper alloy material with a large surface roughness. Thereafter, tin or a tin alloy plating process is performed on the copper or copper alloy material whose surface is roughened by the etching process.
This etching process can be performed using a known method. For example, the etching process is performed by immersing copper or a copper alloy material in the above-described etching solution or by bringing the etching solution into contact with a spray method. . In the case of a copper or copper alloy material that can be energized, electrolytic etching by electrolytic treatment is also possible.
The processing time of the etching process is not particularly limited, but for example, the processing is performed for 1 to 300 seconds, preferably 5 to 200 seconds.
The temperature condition of the etching solution is not particularly limited, but is 10 to 80 ° C., preferably 25 to 50 ° C., for example.
By this etching treatment, a fine uneven shape with a large surface roughness is formed on the surface of the copper or copper alloy material. Specifically, it is preferable to form irregularities having a Ra value of 0.2 μm or more on the surface of the copper or copper alloy material. The average roughness Ra in this description is the same as the “arithmetic average roughness Ra” defined by JIS B 0601-1994. Specifically, the average roughness Ra in the direction of the average line from the roughness curve. A predetermined reference length is extracted, and the absolute values of deviations from the average line of the extracted portion to the roughness curve are summed and averaged.
As described above, in the present embodiment, as a pretreatment for tin and tin alloy plating, a large and fine uneven shape with a Ra value of 0.2 μm or more is formed on the surface of copper or a copper alloy material using the above-described etching solution. Let it form. As a result, the intermetallic compound layer generated at the interface between the tin plating film and the copper or copper alloy material formed by the subsequent plating process is formed substantially uniformly over the entire interface, thereby suppressing the local concentration of stress. Can do. As a result, whiskers formed due to the intensive generation of stress can be suppressed.
In addition, in the etching treatment as a pretreatment for tin and tin alloy plating, the surface of the copper or copper alloy material has a large surface roughness and a fine uneven shape to suppress the occurrence of whiskers. It does not affect the solder wettability of the tin and tin alloy plating film formed by the plating process and the adhesion between the copper or copper alloy material and the tin and tin alloy plating film. Thus, whisker generation can be effectively suppressed without degrading the performance of the tin and tin alloy plating film.
Thus, when the etching treatment as the pre-plating treatment is performed using the above-described etching solution, and a fine uneven shape with a large surface roughness is formed on the surface, then tin and tin are formed on the surface of the copper or copper alloy. Alloy plating treatment is performed. For this tin and tin alloy plating treatment, known plating methods and conditions can be applied, and there is no particular limitation.
The tin and tin alloy plating treatment conditions are not particularly limited. For example, the temperature of the plating solution is preferably 15 to 55 ° C., and the plating time is preferably changed depending on the desired plating film thickness. .
In the present embodiment, as described above, an etching process as a pretreatment for plating is performed using an etchant mainly composed of a cupric ion source, a halogen ion source, and an organic acid on the surface of copper or a copper alloy material. To form an uneven shape on the surface of the copper or copper alloy material. Then, a member for electronic component is formed by forming a tin plating film by a tin and tin alloy plating treatment. The member for electronic parts formed in this way is in a state in which whisker causing a short circuit or the like does not occur or the performance of the plating film such as wettability is maintained.
As described above in detail, the etching solution according to the present embodiment is mainly composed of a cupric ion source, a halogen ion source, and an organic acid, and this etching solution is used before tin and tin alloy plating treatment. Etching is performed on the copper or copper alloy surface as a treatment. By this etching treatment, the uneven shape (surface roughness) formed on the copper or copper alloy material can be made large and fine, and the generation of whiskers can be more effectively suppressed.
That is, the intermetallic compound layer formed at the interface between the copper material and the tin and tin alloy plating film is formed substantially uniformly over the entire interface due to the large surface roughness and fine uneven shape formed by this etching process. Thus, local concentration of stress in the tin plating film can be suppressed. As a result, whiskers generated to relieve the stress generated in the tin and tin alloy plating film can be suppressed.
In addition, as in the past, heat treatment or reflow treatment is not performed on the plating film to suppress the generation of whiskers, but the generation of whiskers is suppressed by the etching process using the above-described etching solution as the plating pretreatment. Therefore, the deterioration of tin and tin alloy plating film such as a decrease in solder wettability caused by the heat treatment and the reflow treatment can be prevented, and the performance of the electronic component member can be maintained. In this way, since the solder wettability is not deteriorated, a tin or tin alloy plating film is formed on a soldered joint portion on the substrate, such that a tin or tin alloy plating film is formed on the lead frame. Even in the case, it can be applied effectively.
In addition, whisker can be effectively suppressed only by performing an etching process in the pre-treatment process of the tin and tin alloy plating process, so there is no need for an increase in the number of process steps and the addition of special equipment. In addition, it is possible to effectively suppress the generation of whiskers and to form a good electronic component member with improved reliability without connection failure.
It should be noted that the present invention is not limited to the above-described embodiment, and any design change or the like within a range not departing from the gist of the invention is included in the present invention. Further, the various compounds contained in the etching solution according to the above-described embodiment are examples that can be applied, and are not limited to those listed above.
Examples Hereinafter, examples of the present invention will be described. The etching solution for copper or copper alloy according to the present invention and the etching treatment method using the etching solution are not limited to the following examples.
(Examples 1 to 8)
As an example, a copper alloy material (C194) lead frame (surface area: 0.245 dm 2 ) was etched by an immersion method using an etching solution having the composition of Examples 1 to 8 shown in Table 1 below. Using the tin plating bath having the composition shown in FIG.
The treated evaluation sample was stored in a thermostat kept at 30 ° C.-60% RH, and after 4000 hours, whiskers on the formed tin plating film were observed with a scanning electron microscope (SEM).
In the evaluation test, the surface roughness (Ra) and the unevenness average interval (Sm) after the etching treatment were also measured by laser microscope observation. As a measuring method, using an ultra-deep shape measuring microscope (VK-8550 manufactured by Keyence Corporation), three points were measured for each sample of the copper alloy material after the etching treatment, and an average value was measured. The uneven average interval (Sm) measured in this example is the “average uneven interval” defined by JIS B 0601-1994. Specifically, from the roughness curve, the average line A certain reference length is extracted in the direction, and the sum of the lengths of the average lines corresponding to one peak and one valley adjacent to the peak is obtained to represent the average value. If Sm is small, it is determined that the uneven surface is fine.
<Processing process>
Electrolytic degreasing (2 minutes) → Washing (15 seconds) × 3 times → Pickling (20 seconds) → Washing (15 seconds) × 3 times → Etching (dipping treatment) → Washing (15 seconds) × 3 times → Pickling 20 seconds) → tin plating (conditions below) → water washing (15 seconds) × 3 times → neutralization → water washing (15 seconds) × 3 times → ion exchange water washing → drying <composition of tin plating bath>
Tin (II) methanesulfonate: 90 g / L (50 g / L as Sn)
70% methanesulfonic acid: 135 g / L
Surfactant; polyoxyethylene nonyl phenyl ether (EO addition mole number 9): 6 g / L
<Tin plating treatment conditions>
Cathode current density: 10 A / dm 2
Plating time: 35 seconds Liquid temperature: 45 ° C
Plating film thickness: 2.5 μm
(Comparative Example 1)
Further, as Comparative Example 1, the same copper alloy material (C194) lead frame as used in the example (surface area: 0.245 dm 2 ) was not subjected to the etching process before the tin plating process. The same tin plating bath was used for tin plating.
Then, in the same manner as in the examples, the tin-plated sample was stored in a thermostatic bath maintained at 30 ° C.-60% RH, and formed with a scanning electron microscope (SEM) after lapse of 4000 hours. The upper whisker was observed.
(Comparative Examples 2 to 8)
Further, as Comparative Examples 2 to 8, Examples were made using an etching solution having the composition of Comparative Examples 2 to 8 shown in Table 2 below with respect to a copper alloy material (C194) lead frame (surface area: 0.245 dm 2 ). In the same manner as above, etching was performed by an immersion method, and then tin plating was performed using a tin plating bath having the same composition as described above to obtain an evaluation sample.
Then, in the same manner as in the examples, the treated evaluation samples were stored in a thermostatic bath maintained at 30 ° C.-60% RH, and formed with a scanning electron microscope (SEM) after lapse of 4000 hours. The upper whisker was observed. Moreover, also about the surface roughness (Ra) after an etching process, and uneven | corrugated average space | interval (Sm), each of copper or copper alloy material after an etching process is measured using an ultra-deep shape measuring microscope (Keyence Co., Ltd. VK-8550). Three points were measured per sample, and the average value was measured. In addition, regarding this surface roughness (Ra) and uneven | corrugated average space | interval (Sm), it measured also about the lead frame in the comparative example 1 before a tin plating process.
(Measurement result)
Tables 1 and 2 below show the measurement results of Examples and Comparative Examples. In Tables 1 and 2, “◯”, “Δ”, and “x” written in the whisker evaluation result column mean the following.
○: No whisker generation Δ: Whisker is observed, but its length is less than 10 μm ×: Whisker is observed, its length is 10 μm or more In addition, in the processing of Example 1 and Example 3, FIG. FIGS. 1A and 1B show SEM images showing the surface state when the lead frame is etched to form a concavo-convex shape (FIG. 1A: Example 1, FIG. 1B: Example 3), and FIG. 2 shows a comparative example. 2 and Comparative Example 3 show SEM images showing the surface state when the lead frame is etched to form a concavo-convex shape (FIG. 2A: Comparative Example 2, FIG. 2B: Comparative Example 3). .
(Examples 1 to 8)
本発明に係る銅又は銅合金材用エッチング液は、錫及び錫合金めっき皮膜の形成に伴って発生するウィスカを抑制させることを目的として、めっき処理前のエッチング処理に使用されるエッチング液である。電子部品用部材であるリードフレーム等の銅又は銅合金材に対し、電解脱脂処理や酸洗処理等の通常の所定の表面処理を施した後に、このエッチング液を用いて銅又は銅合金材表面をエッチング処理し、表面粗さが大きくかつ微細な凹凸を形成させる。そして、その後、錫及び錫合金めっき処理を施すことによってめっき皮膜を形成し、電子部品用部材を形成させる。
ここで、本実施の形態に係る銅及び銅合金材料としては、少なくともその表面が銅又は銅合金で形成されているものや、又はリードフレーム等のように全体が銅又は銅合金で形成されているものが挙げられる。また、少なくともその表面が銅又は銅合金で形成されているものとしては、絶縁樹脂表面に銅(銅合金)が積層されているものも含む。
先ず、本実施の形態に係る、めっき前エッチング表面処理に使用される銅又は銅合金材用エッチング液について説明する。このエッチング液は、第二銅イオン源、ハロゲンイオン源、有機酸を主成分としている。
第二銅イオン源としては、塩化銅(II)、臭化銅(II)、水酸化銅(II)や、酢酸銅(II)、ギ酸銅(II)等の有機酸の銅塩等を用いることができ、これらの第二銅イオン源は、1種単独で用いてもよく、又は2種以上を任意の割合で併用してもよい。
この第二銅イオン源の含有量としては、2~50g/L、好ましくは、5~25g/Lである。第二銅イオン源の含有量が、2g/L未満の場合ではエッチング速度が低下してしまい、また50g/Lより多い場合ではウィスカ抑制の効果の向上が見られない。
ハロゲンイオン源としては、塩素イオン、臭素イオン等のイオン源であり、例えば塩酸、塩化ナトリウム、塩化カリウム、塩化カルシウム、塩化アンモニウム、臭化カリウム、臭化水素酸、塩化銅、塩化亜鉛、塩化鉄、臭化鉄、臭化錫、臭化銅等の、溶液中でハロゲンイオンを解離し得る化合物を用いることができる。これらのハロゲンイオン源は、1種単独で用いてもよく、又は2種以上を任意の割合で併用してもよい。なお、例えば塩化銅(II)は、ハロゲンイオン源と、上述した第二銅イオン源の両方の作用を有するものとして使用することができる。
このハロゲンイオン源の含有量としては、5~200g/L、好ましくは10~150g/Lである。ハロゲンイオン源の含有量が、5g/L未満の場合ではエッチング速度が低下してしまい、また200g/Lより多い場合ではウィスカ抑制の効果の向上が見られない。
有機酸としては、ギ酸、酢酸、プロピオン酸、酪酸、吉草酸、カプロン酸、ステアリン酸等の飽和脂肪族モノカルボン酸、シュウ酸、マロン酸、コハク酸、グルタル酸、アジピン酸、セバシン酸等の飽和脂肪族ジカルボン酸、アクリル酸、プロピオール酸、クロトン酸、オレイン酸、メタクリル酸等の不飽和脂肪族モノカルボン酸、マレイン酸、フマル酸等の不飽和脂肪族ジカルボン酸、安息香酸、フタル酸、桂皮酸等の炭素環カルボン酸、チオフェンカルボン酸、ニコチン酸等の複素環カルボン酸、グリコール酸、乳酸、ロイシン酸、リンゴ酸、酒石酸、グルコン酸、クエン酸等の脂肪族ヒドロキシ酸、サリチル酸、バニリン酸、没食子酸等の芳香族ヒドロキシ酸が挙げられる。これらの有機酸は、1種単独で用いてもよく、又は2種以上を任意の割合で併用してもよい。
有機酸の含有量としては、5~300g/L、好ましくは10~200g/Lである。有機酸の含有量が、5g/L未満の場合ではエッチング速度が低下してしまい、また300g/Lより多い場合では、ウィスカ抑制効果の更なる向上は認められず、不経済である。
このように、本実施の形態に係る銅及び銅合金材用エッチング液は、第二銅イオン源、ハロゲンイオン源、有機酸を主成分としており、このエッチング液を用いて錫及び錫合金めっき処理の前処理として銅又は銅合金表面に対してエッチング処理を施す。これにより、従来から使用されていたエッチング液に比べて、銅又は銅合金材に形成される凹凸形状(表面粗さ)を大きく、かつ微細に形成させることが可能となり、ウィスカの発生を効果的に抑制させることができる。
すなわち、これまでの通常のエッチング液を用いてエッチング処理した錫及び錫合金めっき皮膜では、そのめっき皮膜の粒界に沿って局部的に銅-錫金属間化合物層が形成されていた。これに対し、上述した本実施の形態に係るエッチング液を使用してエッチング処理を施した錫及び錫合金めっき皮膜では、このエッチング処理によって、銅又は銅合金材上に表面粗さが大きくかつ微細な凹凸形状が形成されることになり、金属間化合物層が界面全面にほぼ均一に形成されるようになる。これにより、錫めっき皮膜内の応力が界面全体分散され、局部的に集中することがなくなり、その結果、ウィスカの発生が抑制される。
また、本実施の形態に係るエッチング液には、ポリアミン化合物、及びポリビニル化合物のうちの何れか1種以上をさらに含有させることができる。具体的には、ポリアミン化合物としては、例えばポリエチレンイミン、ポリアルキレンポリアミン等を用いることができる。また、ポリビニル化合物としては、例えばポリビニルピロリドン、ポリビニルアルコール等を用いることができる。なお、これらのポリアミン化合物、及びポリビニル化合物は、1種単独で用いてもよく、又は2種以上を任意の割合で併用してもよい。
これらのポリアミン化合物、及びポリビニル化合物の含有量としては、0.0001~10g/L、好ましくは0.0005~5g/Lである。含有量が、0.0001g/L未満の場合では添加によるウィスカ抑制効果が得られず、また10g/Lより多い場合では添加によるウィスカ抑制効果の向上が見られないだけでなく、エッチング速度が低下する。
このようにして、第二銅イオン源、ハロゲンイオン源、有機酸を主成分とするエッチング液に、ポリアミン化合物、及びポリビニル化合物のうちの何れか1種以上をさらに含有させることによって、銅又は銅合金材に対して、より表面粗さの大きく、かつ微細な凹凸形状を形成させることができる。そして、これにより、応力の局部的な集まりを防止して、より効果的にウィスカの発生を抑制させることができる。
すなわち、ポリアミン化合物やポリビニル化合物を含有させることにより、これらの化合物が銅又は銅合金材の表面に不連続に吸着して孔食状態を作りだすものと考えられる。そして、ポリアミン化合物やポリビニル化合物が吸着した部位と吸着しなかった部位とで、エッチング量に差が生じ、それが凹凸となって表れるものと推測される。これによって、銅又は銅合金材の表面に、より表面粗さが大きく、かつ微細な凹凸を形成させることができることになる。
エッチング未処理の場合や従来のエッチング液で処理した場合には、上述したように、銅が錫めっき皮膜の表面に向かって一方向に拡散するとともに、錫めっき皮膜の粒界に集中するため、銅又は銅合金材と錫めっき皮膜との界面に不均一な金属間化合物層を形成させる。そして、この不均一な金属間化合物層が形成されることにより、錫めっき皮膜の内部に応力を生じさせる結果、ウィスカが発生することとなっていた。
しかしながら、本実施の形態のように、ポリアミン化合物やポリビニル化合物を含有させ、より表面粗さが大きく、かつ微細な凹凸を形成させることで、銅又は銅合金材と錫めっき皮膜との接触面積が増え、また銅の拡散方向が一方向とならずランダムにすることができる。銅又は銅合金材と錫めっき皮膜との接触面積が増えると、銅の拡散の駆動力が分散して、錫めっき皮膜の粒界への拡散が集中することを抑制させる、換言すると粒界への供給量を減少させる。また、銅の拡散が一方向ではなくランダムとなることで、より平滑化された均一な金属間化合物層が形成されることになる。その結果、錫めっき皮膜の内部に応力が生じ難くなり、ウィスカの発生を抑制することができると推測される。
本実施の形態に係るエッチング液には、さらに、第二鉄イオン源、亜鉛イオン源、及びニッケルイオン源のうちの何れか1種以上を含有させることもできる。
具体的に、第二鉄イオン源としては、例えば塩化鉄(III)、臭化鉄(III)、ヨウ化鉄(III)、硫酸鉄(III)、硝酸鉄(III)、酢酸鉄(III)、クエン酸鉄(III)アンモニウム等を用いることができる。また、亜鉛イオン源としては、塩化亜鉛(II)、臭化亜鉛(II)、ヨウ化亜鉛(II)、硫酸亜鉛(II)、硝酸亜鉛(II)、酢酸亜鉛(II)、ギ酸亜鉛(II)、シュウ酸亜鉛(II)等を用いることができる。また、ニッケルイオン源としては、塩化ニッケル(II)、臭化ニッケル(II)、ヨウ化ニッケル(II)、硫酸ニッケル(II)、硝酸ニッケル(II)、酢酸ニッケル(II)、ギ酸ニッケル(II)、スルファミン酸ニッケル(II)、シュウ酸ニッケル(II)等を用いることができる。
これらの第二鉄イオン源、亜鉛イオン源、及びニッケルイオン源は、1種単独で用いてもよく、又は2種以上を任意の割合で併用してもよい。なお、これらの化合物の含有量としては、0.00005~0.005g/L、好ましくは0.0001~0.002g/Lである。含有量が、0.00005g/L未満の場合では添加による効果が得られず、また0.005g/Lより多い場合では効果の向上が見られない。
このようにして、第二銅イオン源、ハロゲンイオン源、有機酸を主成分とするエッチング液に、さらに第二鉄イオン源、亜鉛イオン源、及びニッケルイオン源のうちの何れか1種以上をさらに含有させることによって、めっき液中の銅イオン濃度の変動によるエッチング速度の低下を抑制することができる。また、効率的なエッチング処理を行うことが可能となり、より効果的にウィスカの発生を抑制させることができる。
なお、本実施の形態に係るエッチング剤は、さらに種々の添加剤を含有させることができる。例えば、pHの変動を抑えて安定したエッチング処理を実施することができるように、公知のpH安定化剤を含有させることができる。なお、添加剤としては、これに限られるものではなく、その他種々の添加剤を含有させるようにしてもよい。
このような本実施の形態に係るエッチング液を用いてエッチング処理を施すことにより、リードフレーム等の銅又は銅合金材の表面に、表面粗さが大きく、かつ微細な凹凸形状(表面粗さ)を形成させることができる。そして、これにより銅又は銅合金材と錫及び錫合金めっき皮膜との間に形成される銅-錫金属間化合物層を界面全体に略均一に形成させ、応力が局部的な集中することを防止して、局部的な応力集中を緩和させるために発生するウィスカを効果的に抑制させることができる。
次に、上述したエッチング液を用いたエッチング処理方法について説明する。本実施の形態においては、銅又は銅合金材に対して錫及び錫合金めっき処理を施す前に、めっき前処理として上述したエッチング液を用い、銅又は銅合金材の表面を粗化するエッチング処理を施すようにしている。
すなわち、銅又は銅合金材に対して、公知の脱脂処理、酸洗処理等の所定のクリーニング処理を行った後に、上述した銅又は銅合金材用エッチング液を用いて、錫及び錫合金めっき前処理としてのエッチング処理を施して、表面粗さが大きく、かつ微細な凹凸形状を銅又は銅合金材の表面に形成する。その後、エッチング処理によって表面が粗化された銅又は銅合金材に対して、錫及び錫合金めっき処理を施す。
このエッチング処理としては、公知の方法を用いて行うことができ、例えば銅又は銅合金材を上述したエッチング液に浸漬させて、又はそのエッチング液をスプレー方式により接触させることによって、エッチング処理を行う。また、通電可能な銅又は銅合金材の場合には電解処理による電解エッチングも可能である。
エッチング処理の処理時間は、特に限定されないが、例えば、1~300秒、好ましくは5~200秒で処理する。
また、エッチング液の温度条件としては、特に限定されないが、例えば、10~80℃、好ましくは25~50℃とする。
このエッチング処理によって、銅又は銅合金材の表面に、表面粗さが大きく、かつ微細な凹凸形状を形成させる。具体的には、銅又は銅合金材の表面に、Ra値で0.2μm以上の凹凸を形成させることが好ましい。なお、本説明における平均粗さRaとは、JIS B 0601-1994によって定義される「算術平均粗さRa」と同様のものであり、具体的には、粗さ曲線からその平均線の方向に一定の基準長さを抜き取り、この抜き取り部分の平均線から粗さ曲線までの偏差の絶対値を合計し、平均することにより求められる。
このように、本実施の形態においては、錫及び錫合金めっき前処理として、上述したエッチング液を用いて銅又は銅合金材の表面にRa値0.2μm以上の大きく、かつ微細な凹凸形状を形成させる。これによって、その後のめっき処理によって形成される錫めっき皮膜と銅又は銅合金材の界面に生じる金属間化合物層を、その界面全体に略均一に形成させ、応力の局部的な集中を抑制することができる。その結果、応力の集中的な発生によって形成されるウィスカを抑制することができる。
また、錫及び錫合金めっき前処理としてのエッチング処理において、銅又は銅合金材の表面に、表面粗さが大きくかつ微細な凹凸形状を形成させてウィスカの発生を抑制しているので、その後のめっき処理によって形成させた錫及び錫合金めっき皮膜のはんだ濡れ性や、銅又は銅合金材と錫及び錫合金めっき皮膜との密着性に影響を及ぼすことがない。このように、錫及び錫合金めっき皮膜の性能を低下させずに、効果的にウィスカの発生を抑制することができる。
このようにして、上述したエッチング液を用いてめっき前処理としてのエッチング処理を施し、表面に表面粗さが大きく微細な凹凸形状が形成させると、次にその銅又は銅合金表面に錫及び錫合金めっき処理を施す。この錫及び錫合金めっき処理は、公知のめっき方法・条件を適用することができ、特に限定はされるものではない。
錫及び錫合金めっき処理条件としては、特に限定されるものではないが、例えば、めっき液の温度としては、15~55℃とし、めっき時間としては所望とするめっき膜厚により変化させることが好ましい。
本実施の形態においては、上述したように、銅又は銅合金材の表面に第二銅イオン源、ハロゲンイオン源、有機酸を主成分とするエッチング液を用いて、めっき前処理としてのエッチング処理を行い、銅又は銅合金材の表面に凹凸形状を形成させる。そしてその後、錫及び錫合金めっき処理によって錫めっき皮膜を形成することによって、電子部品用部材を形成させる。このようにして形成された電子部品用部材は、短絡等の原因となるウィスカの発生がなく、またはんだ濡れ性等のめっき皮膜の性能を維持した状態となっている。
以上、詳細に説明したように、本実施の形態に係るエッチング液は、第二銅イオン源、ハロゲンイオン源、有機酸を主成分とし、このエッチング液を用いて錫及び錫合金めっき処理の前処理として銅又は銅合金表面に対してエッチング処理を施す。このエッチング処理により、銅又は銅合金材に形成される凹凸形状(表面粗さ)を大きく、かつ微細に形成させることが可能となり、ウィスカの発生をより効果的に抑制させることができる。
すなわち、このエッチング処理により形成される、表面粗さが大きく、微細な凹凸形状により、銅素材と錫及び錫合金めっき皮膜との界面に生じる金属間化合物層を界面全体に略均一に形成させることで、錫めっき皮膜内の応力が局部的に集中することを抑制することができる。その結果、この錫及び錫合金めっき皮膜に発生した応力を緩和させるために発生するウィスカを抑制させることができる。
また、従来のように、めっき皮膜に対して熱処理やリフロー処理を施してウィスカの発生を抑制するのではなく、めっき前処理として上述したエッチング液を用いたエッチング処理により、ウィスカの発生を抑制させているので、熱処理やリフロー処理の実施によって生じるはんだ濡れ性の低下等の錫及び錫合金めっき皮膜の劣化を防止し、電子部品用部材の性能を維持することができる。そして、このように、はんだ濡れ性を劣化させることがないため、リードフレーム上に錫又は錫合金めっき皮膜を形成させるような、基体上の被はんだ接合部に錫又は錫合金めっき皮膜を形成させる場合においても、効果的に適用することができる。
さらに、錫及び錫合金めっき処理の前処理工程にてエッチング処理を行うのみで効果的にウィスカを抑制することができることから、処理工程数の増加や特別な設備の増設の必要がなく、容易にかつ効果的にウィスカの発生を抑制させるとともに、接続不良等のない信頼性の向上した良好な電子部品用部材を形成することができる。
なお、本発明は、上述した実施の形態に限られるものではなく、発明の要旨を逸脱しない範囲での設計変更等があっても本発明に含まれる。また、上述した本実施の形態に係るエッチング液に含有される種々の化合物は、適用することができる一例を示したものであり、上記列挙したものに限られるものでない。
実施例
以下、本発明の実施例について説明する。なお、本発明に係る銅又は銅合金用のエッチング液、並びにそのエッチング液を用いたエッチング処理方法は、下記の実施例に限定されるものではない。
(実施例1~8)
実施例として、銅合金材(C194)リードフレーム(表面積:0.245dm2)を、下記表1の示す実施例1~8の組成からなるエッチング液を用いて浸漬方法でエッチング処理した後、下記に示す組成からなる錫めっき浴を用いて錫めっき処理を施して評価試料とした。
処理を施した評価試料は、30℃-60%RHに保持した恒温槽内に保管し、4000時間経過後に走査電子顕微鏡(SEM)により、形成した錫めっき皮膜上のウィスカを観察した。
また、評価試験においては、エッチング処理後の表面粗さ(Ra)及び凹凸平均間隔(Sm)についてもレーザー顕微鏡観察により測定した。測定方法としては、超深度形状測定顕微鏡(株式会社キーエンス製 VK-8550)を用い、エッチング処理後の銅合金材の各試料あたり3点を測定し、平均値を測定した。なお、本実施例において測定した凹凸平均間隔(Sm)とは、JIS B 0601-1994によって規定されている「凹凸の平均間隔」であり、具体的には、粗さ曲線から、その平均線の方向に一定の基準長さだけ抜き取り、1つの山及びそれに隣り合う1つの谷に対応する平均線の長さの和を求め、平均値を表したものである。Smが小さいと凹凸の目が細かいと判断される。
<処理工程>
電解脱脂(2分)→水洗(15秒)×3回→酸洗(20秒)→水洗(15秒)×3回→エッチング(浸漬処理)→水洗(15秒)×3回→酸洗(20秒)→錫めっき(下記条件)→水洗(15秒)×3回→中和→水洗(15秒)×3回→イオン交換水洗→乾燥
<錫めっき浴の組成>
メタンスルホン酸錫(II):90g/L(Snとして50g/L)
70%メタンスルホン酸:135g/L
界面活性剤;ポリオキシエチレンノニルフェニルエーテル(EO付加モル数9):6g/L
<錫めっき処理条件>
陰極電流密度:10A/dm2
めっき時間:35秒
液温:45℃
めっき膜厚:2.5μm
(比較例1)
また、比較例1として、実施例で用いたものと同様の銅合金材(C194)リードフレーム(表面積:0.245dm2)に対し、錫めっき処理前にエッチング処理を行わずに、実施例と同様の上記錫めっき浴を用いて錫めっき処理を行った。
そして、実施例と同様にして、錫めっき処理を施した試料を30℃-60%RHに保持した恒温槽内に保管し、4000時間経過後に走査電子顕微鏡(SEM)により、形成した錫めっき皮膜上のウィスカを観察した。
(比較例2~8)
また、比較例2~8として、銅合金材(C194)リードフレーム(表面積:0.245dm2)に対し、下記表2の示す比較例2~8の組成からなるエッチング液を用いて、実施例と同様にして浸漬方法でエッチング処理した後、上記と同様の組成からなる錫めっき浴を用いて錫めっき処理を施して評価試料とした。
そして、実施例と同様にして、処理を施した評価試料は、30℃-60%RHに保持した恒温槽内に保管し、4000時間経過後に走査電子顕微鏡(SEM)により、形成した錫めっき皮膜上のウィスカを観察した。また、エッチング処理後の表面粗さ(Ra)及び凹凸平均間隔(Sm)についても、超深度形状測定顕微鏡(株式会社キーエンス製 VK-8550)を用い、エッチング処理後の銅又は銅合金材の各試料あたり3点を測定し、平均値を測定した。なお、この表面粗さ(Ra)及び凹凸平均間隔(Sm)に関しては、錫めっき処理前の比較例1におけるリードフレームについても測定した。
(測定結果)
下記の表1及び表2に、実施例及び比較例の測定結果を示す。なお、表1及び表2において、ウィスカ評価結果の欄に記してある『○』、『△』、『×』は以下のことを意味する。
○:ウィスカの発生ゼロ
△:ウィスカは観察されたが、その長さが10μm未満
×:ウィスカが観察され、その長さは10μm以上
また、図1に、実施例1及び実施例3の処理において、リードフレームに対してエッチング処理を施して凹凸形状を形成させたときの表面状態の示すSEM像を示し(図1A:実施例1、図1B:実施例3)、さらに図2に、比較例2及び比較例3の処理において、リードフレームに対してエッチング処理を施して凹凸形状を形成させたときの表面状態の示すSEM像を示す(図2A:比較例2、図2B:比較例3)。
(実施例1~8) Hereinafter, the copper or copper alloy etching solution for suppressing whiskers generated on the tin and tin alloy plating film and the plating pretreatment method using the etching solution according to the present embodiment will be described in detail.
The etching solution for copper or copper alloy material according to the present invention is an etching solution used for etching treatment before plating treatment for the purpose of suppressing whiskers generated with the formation of tin and tin alloy plating film. . Copper or copper alloy material such as a lead frame that is a member for electronic parts is subjected to usual predetermined surface treatment such as electrolytic degreasing treatment or pickling treatment, and then the surface of copper or copper alloy material using this etching solution Is etched to form fine irregularities with a large surface roughness. Then, a plating film is formed by performing a tin and tin alloy plating treatment, and an electronic component member is formed.
Here, as the copper and copper alloy material according to the present embodiment, at least the surface thereof is formed of copper or a copper alloy, or the whole is formed of copper or a copper alloy such as a lead frame. The thing that is. Moreover, what has copper (copper alloy) laminated | stacked on the surface of an insulating resin is also included as what the surface is formed with copper or a copper alloy.
First, the etching solution for copper or copper alloy material used for the pre-plating etching surface treatment according to the present embodiment will be described. This etching solution contains a cupric ion source, a halogen ion source, and an organic acid as main components.
As the cupric ion source, copper salts of organic acids such as copper (II) chloride, copper (II) bromide, copper hydroxide (II), copper acetate (II), copper formate (II) and the like are used. These cupric ion sources may be used alone or in combination of two or more at any ratio.
The content of the cupric ion source is 2 to 50 g / L, preferably 5 to 25 g / L. When the content of the cupric ion source is less than 2 g / L, the etching rate is reduced, and when it is more than 50 g / L, no improvement in whisker suppression effect is observed.
The halogen ion source is an ion source such as chloride ion or bromide ion, for example, hydrochloric acid, sodium chloride, potassium chloride, calcium chloride, ammonium chloride, potassium bromide, hydrobromic acid, copper chloride, zinc chloride, iron chloride. , Iron bromide, tin bromide, copper bromide, and the like can be used. These halogen ion sources may be used individually by 1 type, or may use 2 or more types together in arbitrary ratios. Note that, for example, copper (II) chloride can be used as having both functions of the halogen ion source and the above-described cupric ion source.
The content of the halogen ion source is 5 to 200 g / L, preferably 10 to 150 g / L. When the content of the halogen ion source is less than 5 g / L, the etching rate decreases, and when it is more than 200 g / L, no improvement in whisker suppression effect is observed.
Examples of organic acids include saturated aliphatic monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, and stearic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and sebacic acid. Saturated aliphatic dicarboxylic acid, acrylic acid, propiolic acid, crotonic acid, oleic acid, methacrylic acid and other unsaturated aliphatic monocarboxylic acids, maleic acid, fumaric acid and other unsaturated aliphatic dicarboxylic acids, benzoic acid, phthalic acid, Carboxylic carboxylic acids such as cinnamic acid, heterocyclic carboxylic acids such as thiophene carboxylic acid and nicotinic acid, aliphatic hydroxy acids such as glycolic acid, lactic acid, leucine acid, malic acid, tartaric acid, gluconic acid and citric acid, salicylic acid and vanillin Aromatic hydroxy acids such as acid and gallic acid can be mentioned. These organic acids may be used individually by 1 type, or may use 2 or more types together by arbitrary ratios.
The organic acid content is 5 to 300 g / L, preferably 10 to 200 g / L. When the content of the organic acid is less than 5 g / L, the etching rate is reduced, and when it is more than 300 g / L, no further improvement in the whisker suppressing effect is observed, which is uneconomical.
As described above, the copper and copper alloy material etching solution according to the present embodiment is mainly composed of a cupric ion source, a halogen ion source, and an organic acid, and tin and tin alloy plating treatment is performed using this etching solution. As a pretreatment, an etching process is performed on the copper or copper alloy surface. As a result, it is possible to make the uneven shape (surface roughness) formed on the copper or copper alloy material larger and finer than the etching solution that has been used in the past, and the generation of whiskers is effective. Can be suppressed.
That is, in the tin and tin alloy plating film etched using a conventional etching solution, a copper-tin intermetallic compound layer is locally formed along the grain boundary of the plating film. In contrast, in the tin and tin alloy plating film that has been etched using the etching solution according to the present embodiment described above, the surface roughness is large and fine on the copper or copper alloy material by this etching process. Thus, an uneven shape is formed, and the intermetallic compound layer is formed almost uniformly over the entire interface. Thereby, the stress in a tin plating film is disperse | distributed the whole interface, and it does not concentrate locally, As a result, generation | occurrence | production of a whisker is suppressed.
Moreover, the etching liquid which concerns on this Embodiment can further contain any 1 or more types of a polyamine compound and a polyvinyl compound. Specifically, as the polyamine compound, for example, polyethyleneimine, polyalkylene polyamine, or the like can be used. Moreover, as a polyvinyl compound, polyvinyl pyrrolidone, polyvinyl alcohol, etc. can be used, for example. In addition, these polyamine compounds and polyvinyl compounds may be used individually by 1 type, or may use 2 or more types together in arbitrary ratios.
The content of these polyamine compounds and polyvinyl compounds is 0.0001 to 10 g / L, preferably 0.0005 to 5 g / L. When the content is less than 0.0001 g / L, the effect of suppressing whisker by addition cannot be obtained, and when the content is more than 10 g / L, not only the improvement of whisker suppression effect by addition is not seen, but also the etching rate decreases. To do.
In this way, copper or copper can be obtained by further containing any one or more of a polyamine compound and a polyvinyl compound in an etching solution mainly composed of a cupric ion source, a halogen ion source, and an organic acid. With respect to the alloy material, it is possible to form a fine uneven shape with a larger surface roughness. And thereby, the local gathering of stress can be prevented and generation | occurrence | production of a whisker can be suppressed more effectively.
That is, it is thought that by containing a polyamine compound or a polyvinyl compound, these compounds adsorb discontinuously on the surface of the copper or copper alloy material to create a pitting corrosion state. And it is estimated that there is a difference in the etching amount between the portion where the polyamine compound or polyvinyl compound is adsorbed and the portion where the polyamine compound or polyvinyl compound is not adsorbed, which appears as irregularities. Thereby, the surface roughness of copper or a copper alloy material can be made larger and fine irregularities can be formed.
When not etched or treated with a conventional etching solution, as described above, copper diffuses in one direction toward the surface of the tin plating film and concentrates on the grain boundaries of the tin plating film. A non-uniform intermetallic compound layer is formed at the interface between the copper or copper alloy material and the tin plating film. The formation of this non-uniform intermetallic compound layer causes stress in the tin plating film, resulting in the generation of whiskers.
However, as in this embodiment, the contact area between the copper or copper alloy material and the tin plating film is increased by including polyamine compound or polyvinyl compound, forming a larger unevenness with finer surface roughness. In addition, the copper diffusion direction does not become one direction but can be made random. When the contact area between the copper or copper alloy material and the tin plating film increases, the driving force of the copper diffusion is dispersed and the diffusion of the tin plating film to the grain boundary is suppressed, in other words, to the grain boundary. Reduce the amount of supply. Further, since copper diffusion is random rather than unidirectional, a smoother and uniform intermetallic compound layer is formed. As a result, it is presumed that stress is less likely to occur inside the tin plating film, and the occurrence of whiskers can be suppressed.
The etching solution according to the present embodiment may further contain any one or more of a ferric ion source, a zinc ion source, and a nickel ion source.
Specifically, as the ferric ion source, for example, iron (III) chloride, iron (III) bromide, iron (III) iodide, iron (III) sulfate, iron (III) nitrate, iron (III) acetate Further, iron (III) ammonium citrate and the like can be used. The zinc ion source includes zinc chloride (II), zinc bromide (II), zinc iodide (II), zinc sulfate (II), zinc nitrate (II), zinc acetate (II), zinc formate (II ), Zinc oxalate (II) and the like can be used. Nickel ion sources include nickel chloride (II), nickel bromide (II), nickel iodide (II), nickel sulfate (II), nickel nitrate (II), nickel acetate (II), nickel formate (II). ), Nickel sulfamate (II), nickel oxalate (II), and the like.
These ferric ion sources, zinc ion sources, and nickel ion sources may be used singly or in combination of two or more at any ratio. The content of these compounds is 0.00005 to 0.005 g / L, preferably 0.0001 to 0.002 g / L. When the content is less than 0.00005 g / L, the effect of addition cannot be obtained, and when the content is more than 0.005 g / L, no improvement in effect is observed.
In this way, any one or more of a ferric ion source, a zinc ion source, and a nickel ion source is added to the etching liquid mainly composed of a cupric ion source, a halogen ion source, and an organic acid. Furthermore, by making it contain, the fall of the etching rate by the fluctuation | variation of the copper ion concentration in a plating solution can be suppressed. In addition, an efficient etching process can be performed, and the generation of whiskers can be more effectively suppressed.
Note that the etching agent according to the present embodiment can further contain various additives. For example, a known pH stabilizer can be contained so that a stable etching process can be performed while suppressing fluctuations in pH. In addition, as an additive, it is not restricted to this, You may make it contain other various additives.
By performing an etching process using the etching solution according to this embodiment, the surface of a copper or copper alloy material such as a lead frame has a large surface roughness and a fine uneven shape (surface roughness). Can be formed. As a result, a copper-tin intermetallic compound layer formed between the copper or copper alloy material and the tin and tin alloy plating film is formed substantially uniformly over the entire interface, thereby preventing stress from being concentrated locally. Thus, it is possible to effectively suppress whiskers generated to alleviate local stress concentration.
Next, an etching method using the above-described etching solution will be described. In this embodiment, before performing tin and tin alloy plating treatment on copper or copper alloy material, the etching solution described above is used as a pretreatment for plating, and the etching treatment for roughening the surface of copper or copper alloy material. To give.
That is, after performing a predetermined cleaning process such as a known degreasing process or pickling process on copper or a copper alloy material, before the tin or tin alloy plating using the above-described etching solution for copper or copper alloy material Etching treatment as a treatment is performed to form a fine uneven shape on the surface of the copper or copper alloy material with a large surface roughness. Thereafter, tin or a tin alloy plating process is performed on the copper or copper alloy material whose surface is roughened by the etching process.
This etching process can be performed using a known method. For example, the etching process is performed by immersing copper or a copper alloy material in the above-described etching solution or by bringing the etching solution into contact with a spray method. . In the case of a copper or copper alloy material that can be energized, electrolytic etching by electrolytic treatment is also possible.
The processing time of the etching process is not particularly limited, but for example, the processing is performed for 1 to 300 seconds, preferably 5 to 200 seconds.
The temperature condition of the etching solution is not particularly limited, but is 10 to 80 ° C., preferably 25 to 50 ° C., for example.
By this etching treatment, a fine uneven shape with a large surface roughness is formed on the surface of the copper or copper alloy material. Specifically, it is preferable to form irregularities having a Ra value of 0.2 μm or more on the surface of the copper or copper alloy material. The average roughness Ra in this description is the same as the “arithmetic average roughness Ra” defined by JIS B 0601-1994. Specifically, the average roughness Ra in the direction of the average line from the roughness curve. A predetermined reference length is extracted, and the absolute values of deviations from the average line of the extracted portion to the roughness curve are summed and averaged.
As described above, in the present embodiment, as a pretreatment for tin and tin alloy plating, a large and fine uneven shape with a Ra value of 0.2 μm or more is formed on the surface of copper or a copper alloy material using the above-described etching solution. Let it form. As a result, the intermetallic compound layer generated at the interface between the tin plating film and the copper or copper alloy material formed by the subsequent plating process is formed substantially uniformly over the entire interface, thereby suppressing the local concentration of stress. Can do. As a result, whiskers formed due to the intensive generation of stress can be suppressed.
In addition, in the etching treatment as a pretreatment for tin and tin alloy plating, the surface of the copper or copper alloy material has a large surface roughness and a fine uneven shape to suppress the occurrence of whiskers. It does not affect the solder wettability of the tin and tin alloy plating film formed by the plating process and the adhesion between the copper or copper alloy material and the tin and tin alloy plating film. Thus, whisker generation can be effectively suppressed without degrading the performance of the tin and tin alloy plating film.
Thus, when the etching treatment as the pre-plating treatment is performed using the above-described etching solution, and a fine uneven shape with a large surface roughness is formed on the surface, then tin and tin are formed on the surface of the copper or copper alloy. Alloy plating treatment is performed. For this tin and tin alloy plating treatment, known plating methods and conditions can be applied, and there is no particular limitation.
The tin and tin alloy plating treatment conditions are not particularly limited. For example, the temperature of the plating solution is preferably 15 to 55 ° C., and the plating time is preferably changed depending on the desired plating film thickness. .
In the present embodiment, as described above, an etching process as a pretreatment for plating is performed using an etchant mainly composed of a cupric ion source, a halogen ion source, and an organic acid on the surface of copper or a copper alloy material. To form an uneven shape on the surface of the copper or copper alloy material. Then, a member for electronic component is formed by forming a tin plating film by a tin and tin alloy plating treatment. The member for electronic parts formed in this way is in a state in which whisker causing a short circuit or the like does not occur or the performance of the plating film such as wettability is maintained.
As described above in detail, the etching solution according to the present embodiment is mainly composed of a cupric ion source, a halogen ion source, and an organic acid, and this etching solution is used before tin and tin alloy plating treatment. Etching is performed on the copper or copper alloy surface as a treatment. By this etching treatment, the uneven shape (surface roughness) formed on the copper or copper alloy material can be made large and fine, and the generation of whiskers can be more effectively suppressed.
That is, the intermetallic compound layer formed at the interface between the copper material and the tin and tin alloy plating film is formed substantially uniformly over the entire interface due to the large surface roughness and fine uneven shape formed by this etching process. Thus, local concentration of stress in the tin plating film can be suppressed. As a result, whiskers generated to relieve the stress generated in the tin and tin alloy plating film can be suppressed.
In addition, as in the past, heat treatment or reflow treatment is not performed on the plating film to suppress the generation of whiskers, but the generation of whiskers is suppressed by the etching process using the above-described etching solution as the plating pretreatment. Therefore, the deterioration of tin and tin alloy plating film such as a decrease in solder wettability caused by the heat treatment and the reflow treatment can be prevented, and the performance of the electronic component member can be maintained. In this way, since the solder wettability is not deteriorated, a tin or tin alloy plating film is formed on a soldered joint portion on the substrate, such that a tin or tin alloy plating film is formed on the lead frame. Even in the case, it can be applied effectively.
In addition, whisker can be effectively suppressed only by performing an etching process in the pre-treatment process of the tin and tin alloy plating process, so there is no need for an increase in the number of process steps and the addition of special equipment. In addition, it is possible to effectively suppress the generation of whiskers and to form a good electronic component member with improved reliability without connection failure.
It should be noted that the present invention is not limited to the above-described embodiment, and any design change or the like within a range not departing from the gist of the invention is included in the present invention. Further, the various compounds contained in the etching solution according to the above-described embodiment are examples that can be applied, and are not limited to those listed above.
Examples Hereinafter, examples of the present invention will be described. The etching solution for copper or copper alloy according to the present invention and the etching treatment method using the etching solution are not limited to the following examples.
(Examples 1 to 8)
As an example, a copper alloy material (C194) lead frame (surface area: 0.245 dm 2 ) was etched by an immersion method using an etching solution having the composition of Examples 1 to 8 shown in Table 1 below. Using the tin plating bath having the composition shown in FIG.
The treated evaluation sample was stored in a thermostat kept at 30 ° C.-60% RH, and after 4000 hours, whiskers on the formed tin plating film were observed with a scanning electron microscope (SEM).
In the evaluation test, the surface roughness (Ra) and the unevenness average interval (Sm) after the etching treatment were also measured by laser microscope observation. As a measuring method, using an ultra-deep shape measuring microscope (VK-8550 manufactured by Keyence Corporation), three points were measured for each sample of the copper alloy material after the etching treatment, and an average value was measured. The uneven average interval (Sm) measured in this example is the “average uneven interval” defined by JIS B 0601-1994. Specifically, from the roughness curve, the average line A certain reference length is extracted in the direction, and the sum of the lengths of the average lines corresponding to one peak and one valley adjacent to the peak is obtained to represent the average value. If Sm is small, it is determined that the uneven surface is fine.
<Processing process>
Electrolytic degreasing (2 minutes) → Washing (15 seconds) × 3 times → Pickling (20 seconds) → Washing (15 seconds) × 3 times → Etching (dipping treatment) → Washing (15 seconds) × 3 times → Pickling 20 seconds) → tin plating (conditions below) → water washing (15 seconds) × 3 times → neutralization → water washing (15 seconds) × 3 times → ion exchange water washing → drying <composition of tin plating bath>
Tin (II) methanesulfonate: 90 g / L (50 g / L as Sn)
70% methanesulfonic acid: 135 g / L
Surfactant; polyoxyethylene nonyl phenyl ether (EO addition mole number 9): 6 g / L
<Tin plating treatment conditions>
Cathode current density: 10 A / dm 2
Plating time: 35 seconds Liquid temperature: 45 ° C
Plating film thickness: 2.5 μm
(Comparative Example 1)
Further, as Comparative Example 1, the same copper alloy material (C194) lead frame as used in the example (surface area: 0.245 dm 2 ) was not subjected to the etching process before the tin plating process. The same tin plating bath was used for tin plating.
Then, in the same manner as in the examples, the tin-plated sample was stored in a thermostatic bath maintained at 30 ° C.-60% RH, and formed with a scanning electron microscope (SEM) after lapse of 4000 hours. The upper whisker was observed.
(Comparative Examples 2 to 8)
Further, as Comparative Examples 2 to 8, Examples were made using an etching solution having the composition of Comparative Examples 2 to 8 shown in Table 2 below with respect to a copper alloy material (C194) lead frame (surface area: 0.245 dm 2 ). In the same manner as above, etching was performed by an immersion method, and then tin plating was performed using a tin plating bath having the same composition as described above to obtain an evaluation sample.
Then, in the same manner as in the examples, the treated evaluation samples were stored in a thermostatic bath maintained at 30 ° C.-60% RH, and formed with a scanning electron microscope (SEM) after lapse of 4000 hours. The upper whisker was observed. Moreover, also about the surface roughness (Ra) after an etching process, and uneven | corrugated average space | interval (Sm), each of copper or copper alloy material after an etching process is measured using an ultra-deep shape measuring microscope (Keyence Co., Ltd. VK-8550). Three points were measured per sample, and the average value was measured. In addition, regarding this surface roughness (Ra) and uneven | corrugated average space | interval (Sm), it measured also about the lead frame in the comparative example 1 before a tin plating process.
(Measurement result)
Tables 1 and 2 below show the measurement results of Examples and Comparative Examples. In Tables 1 and 2, “◯”, “Δ”, and “x” written in the whisker evaluation result column mean the following.
○: No whisker generation Δ: Whisker is observed, but its length is less than 10 μm ×: Whisker is observed, its length is 10 μm or more In addition, in the processing of Example 1 and Example 3, FIG. FIGS. 1A and 1B show SEM images showing the surface state when the lead frame is etched to form a concavo-convex shape (FIG. 1A: Example 1, FIG. 1B: Example 3), and FIG. 2 shows a comparative example. 2 and Comparative Example 3 show SEM images showing the surface state when the lead frame is etched to form a concavo-convex shape (FIG. 2A: Comparative Example 2, FIG. 2B: Comparative Example 3). .
(Examples 1 to 8)
また、実施例2では、第二鉄イオン源としての塩化第二鉄(III)をさらに含有させたことにより、第二銅イオン源である塩化銅(II)の含有量を20g/Lとした場合においても、実施例1と同様にリードフレーム表面に凹凸形状を形成させることができ、ウィスカの発生を抑制させることができた。
さらに、第二銅イオン源と、有機酸と、ハロゲンイオン源とを主成分とするエッチング液に、さらに種々のポリアミン化合物、又はポリビニル化合物を含有させた実施例3~8では、ウィスカの発生が全く確認されず、ウィスカの発生を完全に防止することができた。このことは、これらの実施例3~8のリードフレームにおける表面粗さがRa値で0.27~0.43μmとなったことからも判断できるように、実施例1及び2と比べて、より表面粗さを大きくし、微細な凹凸形状をリードフレームの表面に形成させることができ、金属間化合物層を界面全体により一層均一に形成させて、応力が局部的に集中することを抑制することできたためと考えられる。
一方、これらの実施例の結果に対し、表2に示した比較例について検討すると、錫めっき処理の前工程としてリードフレームをエッチング処理しなかった比較例1では、10μm以上の長さを有するウィスカの発生が多数確認された。これは、リードフレームの表面の粗さがRa値で0.08μmであったことからも判るように、エッチング処理を行わなかったことによりリードフレームと錫めっき皮膜との接触面に凹凸形状が形成されず、その結果、金属間化合物層が局部的に形成され、めっき皮膜の応力が分散されなかったためであると考えられる。
また、めっき前処理工程としてリードフレームに対してエッチング処理を施した比較例2~8においても、10μm以上の長さを有するウィスカの発生が確認された。これらの比較例のうち、比較例2、3、5~8では、表2にそれぞれ示すようにエッチング処理後のリードフレーム表面の粗さはRa値で0.22~0.37μmとなり、表面粗さは大きくはないものの、実施例1~8の結果に示した表面粗さとの差は僅かであった。しかしながら、上述のように実施例1~8では10μm以上の長さを有するウィスカが発生しなかったのに対し、これらの比較例2、3、5~8では10μm以上の長さを有するウィスカが発生した。このことは、ウィスカの発生を効果的に抑制させるものは、エッチング処理による表面粗さの大きさだけでなく、その形成される凹凸形状にも依存することを示唆している。
ここで、実施例の結果を示す表1と、比較例の結果を示す表2における、エッチング処理後の凹凸形状の平均間隔Sm(μm)を調べると、実施例1~8では、エッチング処理によってリードフレーム表面に形成された凹凸形状の平均間隔は、Sm値で2.36μm~2.98μmであり、特に種々のポリアミン化合物、又はポリビニル化合物を含有させた実施例3~8においては、Sm値で2.36μm~2.75μmであった。このように、実施例1~8では、表面粗さが大きく、かつ微細な凹凸形状をリードフレーム表面に形成することができたことがわかる。
一方、比較例では、エッチング処理を施した比較例2~8の全てにおいて、リードフレーム表面に形成された凹凸形状の平均間隔は、Sm値で3.60μm~4.55μmであり、上述した実施例1~8に比べて、凹凸形状の平均間隔Smは大きいものであった。
このエッチング処理後の凹凸形状の平均間隔Smの測定結果から判るように、表面粗さRa値が0.2μm以上の凹凸形状であっても、微細な凹凸形状が形成されなければ、ウィスカ抑制効果は発揮されないことが明確に判る。
上述の実施例において、表面粗さが大きく、さらに微細な凹凸形状が形成されたことは、図1A及びBに示すSEM像からも明確に判断することができる。これに対して比較例においては、比較例2及び3におけるエッチング処理後の表面状態を観察した図2A及びBに示すSEM像から明確に判るように、凹凸形状は形成されていると判断できるものの、その形状は微細なものではない。
このようなことから、ウィスカの発生を効果的に抑制させるものは、エッチング処理による表面粗さの大きさだけでなく、その形成される凹凸形状にも依存し、実施例1~8におけるエッチング処理のように、表面粗さが大きく、かつより微細な凹凸形状を形成させることによって、効果的にウィスカの発生を抑制することができることがわかる。
また、エッチング液の組成の観点からも評価を加えると、比較例2の過酸化ソーダと硫酸を主成分とするエッチング液や、比較例3、5、6の過酸化水素水と硫酸を主成分とするエッチング液では、表面粗さはRa値で0.22~0.37μmとなり、凹凸形状は形成させることはできたものの、上述したように、凹凸形状の平均間隔Sm値や図2から判断して、微細な凹凸形状を形成させることはできなかった。
そして、さらに比較例2、3、5、6では、Ra値で0.22~0.37μmの表面粗さとすることはできたものの、エッチング量は79.1~87.0mgと多く、一方で比較例3と同様の組成からなるエッチング液でエッチング量を45.3mgに減らして処理した比較例4においては、表面粗さがRa値で0.16μmであった。このことから、実施例1乃至8と比較して、エッチング量を大きくしなければRa値で0.22~0.37μmの表面粗さを形成させることができなかったことがわかる。これに対し、実施例1乃至8におけるエッチング処理では、50mg以下のエッチング量で、大きな表面粗さの凹凸形状を形成することができたとともに、上述のように微細な凹凸形状を形成することができた。
エッチング処理において、エッチング量を多くした場合には、部材のサイズを変化させてしまい、さらに電気特性等の性能劣化を生じさせてしまうことになる。このような点も鑑みると、実施例1乃至8においては、少ないエッチング量で電気特性等の劣化等を生じさせることなく、表面粗さが大きく、かつ微細な凹凸形状を形成させることができることがわかる。
また、実施例1乃至8においてエッチング液の主成分としていた第二銅イオン源と、有機酸と、ハロゲンイオン源のうち、ハロゲンイオン源を含有していないエッチング液を用いて処理した比較例7と、有機酸を含有していないエッチング液を用いて処理した比較例8では、上述のように、大きな表面粗さを有する凹凸形状は形成させることはできたものの、微細な凹凸形状を形成させることはできず、ウィスカ抑制効果はなかった。この結果から、第二銅イオン源と、有機酸と、ハロゲンイオン源を主成分とするエッチング液を用いて処理することによって、表面粗さが大きく、かつ微細な凹凸形状をリードフレーム等の表面に形成させることが可能となり、その結果、効果的にウィスカを抑制することができることがわかる。
以上の実施例及び比較例の結果から、錫めっき処理の前処理として、めっき皮膜を形成させるリードフレーム等の銅及び銅合金材の表面を、第二銅イオン源と、有機酸と、ハロゲンイオン源を主成分とするエッチング液によってエッチング処理し、その表面に、表面粗さが大きく、かつ微細な凹凸形状を形成させることによって、効果的にウィスカを抑制させることができることが判明した。
産業上の利用可能性
上述した本発明によれば、錫及び錫合金めっき処理の前処理において、第二銅イオン源、ハロゲンイオン源、有機酸を主成分とするエッチング液を用い、銅又は銅合金材の表面を粗化して表面粗さが大きくかつ微細な凹凸形状を形成させているので、錫及び錫合金めっき皮膜に局部的に応力が生じることを防止し、ウィスカの発生を効果的に抑制させることができる。
また、錫及び錫合金めっき処理の前処理工程にてエッチング処理によって凹凸形状を形成させるようにしているので、めっき皮膜のはんだ濡れ性の低下等の性能の低下を生じさせることなく、めっき皮膜に対して熱処理やリフロー処理を実施しなくてもウィスカの発生を抑制することができる。さらに、処理工程数の増加や特別な設備の増設の必要がない。
Moreover, in Example 2, the content of copper (II) chloride as the cupric ion source was 20 g / L by further containing ferric chloride (III) as the ferric ion source. Even in the case, it was possible to form an uneven shape on the surface of the lead frame as in Example 1, and to suppress the generation of whiskers.
Furthermore, in Examples 3 to 8 in which various polyamine compounds or polyvinyl compounds were further contained in the etching solution mainly composed of a cupric ion source, an organic acid, and a halogen ion source, generation of whiskers occurred. It was not confirmed at all, and the occurrence of whiskers could be completely prevented. This can be judged from the fact that the surface roughness in the lead frames of Examples 3 to 8 is 0.27 to 0.43 μm in Ra value, as compared with Examples 1 and 2. The surface roughness can be increased, fine irregularities can be formed on the surface of the lead frame, and the intermetallic compound layer can be formed more uniformly over the entire interface, suppressing the concentration of stress locally. It is thought that it was made.
On the other hand, when the comparative examples shown in Table 2 are examined with respect to the results of these examples, the whisker having a length of 10 μm or more is obtained in the comparative example 1 in which the lead frame was not etched as a pre-process of the tin plating process. A number of occurrences were confirmed. As can be seen from the fact that the roughness of the surface of the lead frame was 0.08 μm in Ra value, an uneven shape was formed on the contact surface between the lead frame and the tin plating film because the etching process was not performed. As a result, it is considered that the intermetallic compound layer was locally formed and the stress of the plating film was not dispersed.
In Comparative Examples 2 to 8 where the lead frame was etched as a pre-plating process, the generation of whiskers having a length of 10 μm or more was confirmed. Among these comparative examples, in Comparative Examples 2, 3, 5 to 8, as shown in Table 2, the roughness of the lead frame surface after the etching treatment is 0.22 to 0.37 μm in terms of Ra value. Although the thickness was not large, the difference from the surface roughness shown in the results of Examples 1 to 8 was slight. However, whiskers having a length of 10 μm or more were not generated in Examples 1 to 8 as described above, whereas whiskers having a length of 10 μm or more were obtained in Comparative Examples 2, 3, and 5 to 8. Occurred. This suggests that what effectively suppresses the generation of whiskers depends not only on the size of the surface roughness by the etching process but also on the uneven shape formed.
Here, when the average interval Sm (μm) of the concavo-convex shape after the etching process in Table 1 showing the results of the examples and Table 2 showing the results of the comparative examples is examined, in Examples 1 to 8, the etching process is performed. The average spacing of the irregularities formed on the surface of the lead frame is 2.36 μm to 2.98 μm in terms of Sm value. Particularly in Examples 3 to 8 containing various polyamine compounds or polyvinyl compounds, the Sm value 2.36 μm to 2.75 μm. Thus, it can be seen that in Examples 1 to 8, the surface roughness was large and fine irregularities could be formed on the lead frame surface.
On the other hand, in the comparative examples, in all of the comparative examples 2 to 8 subjected to the etching treatment, the average interval of the concavo-convex shape formed on the lead frame surface is 3.60 μm to 4.55 μm in Sm value. Compared with Examples 1 to 8, the average interval Sm of the concavo-convex shape was large.
As can be seen from the measurement result of the average interval Sm of the concavo-convex shape after the etching treatment, even if the concavo-convex shape has a surface roughness Ra value of 0.2 μm or more, if the fine concavo-convex shape is not formed, the whisker suppressing effect It can be clearly seen that is not exhibited.
In the above-described embodiment, it can be clearly determined from the SEM images shown in FIGS. 1A and 1B that the surface roughness is large and a fine uneven shape is formed. On the other hand, in the comparative example, it can be determined that the uneven shape is formed as clearly seen from the SEM images shown in FIGS. 2A and 2B in which the surface state after the etching process in the comparative examples 2 and 3 is observed. The shape is not fine.
Therefore, what effectively suppresses the generation of whiskers depends not only on the size of the surface roughness by the etching process but also on the uneven shape to be formed, and the etching process in Examples 1 to 8 Thus, it can be seen that the formation of whiskers can be effectively suppressed by forming a finer concavo-convex shape having a large surface roughness.
Further, when evaluated from the viewpoint of the composition of the etching solution, the etching solution mainly containing sodium peroxide and sulfuric acid of Comparative Example 2 and the hydrogen peroxide solution and sulfuric acid of Comparative Examples 3, 5, and 6 are mainly used. In the etching solution, the surface roughness is 0.22 to 0.37 μm in Ra value, and an uneven shape can be formed. However, as described above, it is judged from the average interval Sm value of the uneven shape and FIG. Thus, it was not possible to form a fine uneven shape.
Further, in Comparative Examples 2, 3, 5, and 6, although the surface roughness Ra was 0.22 to 0.37 μm, the etching amount was as large as 79.1 to 87.0 mg, In Comparative Example 4 where the etching amount was reduced to 45.3 mg with an etching solution having the same composition as Comparative Example 3, the surface roughness was 0.16 μm in terms of Ra value. From this, it can be seen that a surface roughness of 0.22 to 0.37 μm in Ra value could not be formed unless the etching amount was increased as compared with Examples 1 to 8. On the other hand, in the etching treatments in Examples 1 to 8, it was possible to form an uneven shape with a large surface roughness with an etching amount of 50 mg or less, and to form a fine uneven shape as described above. did it.
In the etching process, when the etching amount is increased, the size of the member is changed, and further performance deterioration such as electrical characteristics is caused. In view of this point, in Examples 1 to 8, it is possible to form a fine concavo-convex shape with a large surface roughness without causing deterioration of electrical characteristics or the like with a small etching amount. Recognize.
Moreover, the comparative example 7 processed using the etching liquid which does not contain the halogen ion source among the cupric ion source which was the main components of the etching liquid in Examples 1 thru | or 8, an organic acid, and a halogen ion source. In Comparative Example 8 processed using an etching solution not containing an organic acid, as described above, an uneven shape having a large surface roughness could be formed, but a fine uneven shape was formed. The whisker suppression effect was not possible. From this result, the surface roughness of the lead frame or the like is increased by processing with an etchant containing a cupric ion source, an organic acid, and a halogen ion source as a main component and having a fine surface roughness. As a result, it can be seen that whiskers can be effectively suppressed.
From the results of the above examples and comparative examples, as a pretreatment of the tin plating process, the surface of the copper and copper alloy material such as a lead frame for forming the plating film is formed by using a second copper ion source, an organic acid, and a halogen ion. It has been found that whiskers can be effectively suppressed by etching with an etchant containing a source as a main component and forming a fine uneven shape on the surface with a large surface roughness.
INDUSTRIAL APPLICABILITY According to the above-described present invention, copper or copper is used in the pretreatment of the tin and tin alloy plating treatment by using an etching solution mainly composed of a cupric ion source, a halogen ion source, and an organic acid. Since the surface of the alloy material is roughened to form a rough surface with a large surface roughness and fine irregularities, local stress is prevented from occurring in the tin and tin alloy plating film, and whisker generation is effectively prevented. Can be suppressed.
In addition, since the concavo-convex shape is formed by the etching process in the pretreatment process of the tin and tin alloy plating process, the plating film can be formed without causing the performance deterioration such as the solder wettability of the plating film. On the other hand, the occurrence of whiskers can be suppressed without performing heat treatment or reflow treatment. Furthermore, there is no need to increase the number of processing steps or add special equipment.
Claims (11)
- 1.錫及び錫合金めっき皮膜上に発生するウィスカを抑制するために、銅又は銅合金材の表面に使用されるエッチング液であって、
第二銅イオン源と、ハロゲンイオン源と、有機酸とを主成分とする銅又は銅合金材用エッチング液。 1. In order to suppress whiskers generated on tin and tin alloy plating film, an etching solution used on the surface of copper or copper alloy material,
Etching solution for copper or copper alloy material mainly composed of cupric ion source, halogen ion source and organic acid. - 2.ポリアミン化合物、及びポリビニル化合物のうちの何れか1種以上をさらに含有する請求の範囲第1項記載の銅又は銅合金材用エッチング液。 2. The etching solution for copper or copper alloy material according to claim 1, further comprising at least one of a polyamine compound and a polyvinyl compound.
- 3.第二鉄イオン源、亜鉛イオン源、及びニッケルイオン源のうちの何れか1種以上をさらに含有する請求の範囲第1項又は第2項記載の銅又は銅合金材用エッチング液。 3. The etching solution for copper or copper alloy material according to claim 1 or 2, further comprising at least one of a ferric ion source, a zinc ion source, and a nickel ion source.
- 4.錫及び錫合金めっき皮膜上に発生するウィスカを抑制させるための銅又は銅合金材表面のめっき前処理方法であって、
第二銅イオン源と、ハロゲンイオン源と、有機酸とを主成分とする銅又は銅合金材用エッチング液を用いて、上記銅又は銅合金材の表面をエッチング処理して粗化するめっき前処理方法。 4). A plating pretreatment method for copper or copper alloy material surface for suppressing whisker generated on a tin and tin alloy plating film,
Before plating, the surface of the copper or copper alloy material is etched and roughened using an etching solution for copper or copper alloy material mainly composed of a cupric ion source, a halogen ion source, and an organic acid. Processing method. - 5.上記銅又は銅合金材用エッチング液は、さらにポリアミン化合物、及びポリビニル化合物のうちの何れか1種以上を含有する請求の範囲第4項記載のめっき前処理方法。 5. The plating pretreatment method according to claim 4, wherein the etching solution for copper or copper alloy material further contains any one or more of a polyamine compound and a polyvinyl compound.
- 6.上記銅又は銅合金材用エッチング液は、さらに第二鉄イオン源、亜鉛イオン源、及びニッケルイオン源のうちの何れか1種以上を含有する請求の範囲第5項記載のめっき前処理方法。 6). The plating pretreatment method according to claim 5, wherein the etching solution for copper or copper alloy material further contains any one or more of a ferric ion source, a zinc ion source, and a nickel ion source.
- 7.銅又は銅合金材の表面粗さRa値が、0.2μm以上となるようにエッチング処理する請求の範囲第4項乃至第6項のうち何れか1項記載のめっき前処理方法。 7. The plating pretreatment method according to any one of claims 4 to 6, wherein the etching treatment is performed so that the surface roughness Ra value of the copper or copper alloy material is 0.2 µm or more.
- 8.銅又は銅合金材の表面の凹凸形状の平均間隔Sm値が、3.5μm以下となるようにエッチング処理する請求の範囲第7項記載のめっき前処理方法。 8). The plating pretreatment method according to claim 7, wherein the etching treatment is performed so that an average interval Sm value of the uneven shape on the surface of the copper or copper alloy material is 3.5 μm or less.
- 9.請求項1乃至3のうちの何れか1項記載の銅又は銅合金材用エッチング液を用いてエッチングするエッチング処理工程と、
上記エッチング処理工程にて粗化された銅又は銅合金材に対して錫及び錫合金めっき皮膜を形成させるめっき処理工程と
を有する電子部品用部材の形成方法。 9. Etching treatment step of etching using the copper or copper alloy material etching solution according to any one of claims 1 to 3,
A plating treatment step of forming tin and a tin alloy plating film on the copper or copper alloy material roughened in the etching treatment step. - 10.上記エッチング処理工程では、銅又は銅合金材の表面粗さRa値が0.2μm以上となるように処理する請求の範囲第9項記載の電子部品用部材の形成方法。 10. The method for forming an electronic component member according to claim 9, wherein in the etching treatment step, the surface roughness Ra value of the copper or copper alloy material is 0.2 μm or more.
- 11.上記エッチング処理工程では、銅又は銅合金材の表面の凹凸形状の平均間隔Sm値が3.5μm以下となるようにエッチング処理する請求の範囲第10項記載の電子部品用部材の形成方法。 11. 11. The method for forming a member for an electronic component according to claim 10, wherein in the etching treatment step, the etching treatment is performed so that the average interval Sm value of the uneven shape on the surface of the copper or copper alloy material is 3.5 μm or less.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2010523893A JP5789375B2 (en) | 2008-08-08 | 2009-08-07 | Pre-plating method |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2008-205851 | 2008-08-08 | ||
JP2008205851 | 2008-08-08 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2010016562A1 true WO2010016562A1 (en) | 2010-02-11 |
Family
ID=41663774
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2009/063986 WO2010016562A1 (en) | 2008-08-08 | 2009-08-07 | Etchant for copper or copper alloy material, pre-plating treatment method, and method for forming member for electronic component |
Country Status (3)
Country | Link |
---|---|
JP (1) | JP5789375B2 (en) |
TW (1) | TW201012970A (en) |
WO (1) | WO2010016562A1 (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2011179085A (en) * | 2010-03-02 | 2011-09-15 | C Uyemura & Co Ltd | Pretreatment agent and pretreatment method for electroplating and electroplating method |
JP2013527323A (en) * | 2010-05-26 | 2013-06-27 | アトテツク・ドイチユラント・ゲゼルシヤフト・ミツト・ベシユレンクテル・ハフツング | Compositions and methods for microetching of copper and copper alloys |
JP2015185582A (en) * | 2014-03-20 | 2015-10-22 | 三菱電機株式会社 | Method for manufacturing electronic component |
EP3184669A1 (en) | 2015-12-23 | 2017-06-28 | ATOTECH Deutschland GmbH | Etching solution for copper and copper alloy surfaces |
US10266959B2 (en) * | 2012-11-08 | 2019-04-23 | Monnaie Royale Canadienne / Royal Canadian Mint | Enhanced techniques for production of golden bronze by inter-diffusion of tin and copper under controlled conditions |
CN114540818A (en) * | 2022-02-15 | 2022-05-27 | 江西省科学院应用物理研究所 | Copper-magnesium-silicon alloy metallographic corrosive agent and metallographic structure display method thereof |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
TWI639730B (en) * | 2015-02-13 | 2018-11-01 | 關東鑫林科技股份有限公司 | Etching liquid composition and etching method using the same |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2000109981A (en) * | 1998-10-05 | 2000-04-18 | Ishihara Chem Co Ltd | Abnormal crystallization preventive agent in plating film on copper-foil substrate and its prevention method |
JP2004339605A (en) * | 2003-05-12 | 2004-12-02 | Rohm & Haas Electronic Materials Llc | Improved tin-plating method |
JP2005068524A (en) * | 2003-08-27 | 2005-03-17 | C Uyemura & Co Ltd | Etching solution |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP3458023B2 (en) * | 1995-08-01 | 2003-10-20 | メック株式会社 | Copper and copper alloy microetchants |
JP2000328256A (en) * | 1999-03-17 | 2000-11-28 | Ibiden Co Ltd | Electroless plating liquid and production of printed wiring board using the same |
-
2009
- 2009-08-04 TW TW98126271A patent/TW201012970A/en unknown
- 2009-08-07 WO PCT/JP2009/063986 patent/WO2010016562A1/en active Application Filing
- 2009-08-07 JP JP2010523893A patent/JP5789375B2/en not_active Expired - Fee Related
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2000109981A (en) * | 1998-10-05 | 2000-04-18 | Ishihara Chem Co Ltd | Abnormal crystallization preventive agent in plating film on copper-foil substrate and its prevention method |
JP2004339605A (en) * | 2003-05-12 | 2004-12-02 | Rohm & Haas Electronic Materials Llc | Improved tin-plating method |
JP2005068524A (en) * | 2003-08-27 | 2005-03-17 | C Uyemura & Co Ltd | Etching solution |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2011179085A (en) * | 2010-03-02 | 2011-09-15 | C Uyemura & Co Ltd | Pretreatment agent and pretreatment method for electroplating and electroplating method |
JP2013527323A (en) * | 2010-05-26 | 2013-06-27 | アトテツク・ドイチユラント・ゲゼルシヤフト・ミツト・ベシユレンクテル・ハフツング | Compositions and methods for microetching of copper and copper alloys |
US10266959B2 (en) * | 2012-11-08 | 2019-04-23 | Monnaie Royale Canadienne / Royal Canadian Mint | Enhanced techniques for production of golden bronze by inter-diffusion of tin and copper under controlled conditions |
JP2015185582A (en) * | 2014-03-20 | 2015-10-22 | 三菱電機株式会社 | Method for manufacturing electronic component |
EP3184669A1 (en) | 2015-12-23 | 2017-06-28 | ATOTECH Deutschland GmbH | Etching solution for copper and copper alloy surfaces |
JP2019502824A (en) * | 2015-12-23 | 2019-01-31 | アトテツク・ドイチユラント・ゲゼルシヤフト・ミツト・ベシユレンクテル・ハフツングAtotech Deutschland GmbH | Etching solutions for copper and copper alloy surfaces |
US10619251B2 (en) | 2015-12-23 | 2020-04-14 | Atotech Deutschland Gmbh | Etching solution for copper and copper alloy surfaces |
CN114540818A (en) * | 2022-02-15 | 2022-05-27 | 江西省科学院应用物理研究所 | Copper-magnesium-silicon alloy metallographic corrosive agent and metallographic structure display method thereof |
CN114540818B (en) * | 2022-02-15 | 2023-11-10 | 江西省科学院应用物理研究所 | Copper magnesium silicon alloy metallographic corrosive and metallographic structure display method thereof |
Also Published As
Publication number | Publication date |
---|---|
JPWO2010016562A1 (en) | 2012-01-26 |
JP5789375B2 (en) | 2015-10-07 |
TW201012970A (en) | 2010-04-01 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP5789375B2 (en) | Pre-plating method | |
KR100964063B1 (en) | Aqueous antioxidant for tin or tin alloy | |
JP2008174817A (en) | Method for forming displacement tin alloy plated film, displacement tin alloy plating bath, and method for maintaining plating performance | |
JP6078525B2 (en) | Cleaning solution for surface of electroless tin plating film, replenisher thereof, and method for forming tin plating layer | |
JP2007056286A (en) | Aqueous solution for treating metal surface and method for preventing metal surface from discoloring | |
JP6538671B2 (en) | Method of selectively treating copper in the presence of additional metals | |
JP4518507B2 (en) | Metal surface treatment agent | |
JP6114770B2 (en) | Tin plating method for copper alloy material | |
JP2010070838A (en) | Aqueous solution for surface treatment of metal and method for reducing whisker on metal surface | |
JP5337760B2 (en) | Metal surface treatment aqueous solution and method for preventing discoloration of metal surface | |
WO2012073783A1 (en) | Surface treatment agent for pd or alloy mainly composed of pd, and surface coating layer structure of copper surface | |
JP4453443B2 (en) | Tin plating film and method for producing plating film | |
JP5317099B2 (en) | Adhesive layer forming solution | |
JP2002513090A (en) | Method for covering copper or copper alloy surface with tin film or tin alloy film | |
JP5363142B2 (en) | Method for forming tin plating film | |
JP2023069841A (en) | Metal replacement process liquid, surface treatment method for aluminum or aluminum alloy | |
US10774425B2 (en) | Elimination of H2S in immersion tin plating solution | |
JP2005206859A (en) | Method of producing member for electronic component | |
JP2023184437A (en) | Etching treatment liquid and method for surface treatment of aluminum or aluminum alloy | |
JP2006118001A (en) | METHOD FOR FORMING THIN FILM OF Sn-Ag-Cu TERNARY ALLOY | |
JP5458198B2 (en) | Metal surface treatment aqueous solution and method for preventing discoloration of metal surface | |
CN117248215A (en) | Etching treatment liquid, aluminum or aluminum alloy surface treatment method | |
JP2013144835A (en) | ELECTROLESS Ni-P-Sn PLATING SOLUTION | |
JP2009167437A (en) | Plated layer and method for forming the same | |
JP2005325385A (en) | Bright plated film with tin-bismuth alloy for electronic parts such as connector and semiconductor parts, and bright plating bath of tin-bismuth alloy for electronic parts such as connector and semiconductor parts |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 09805044 Country of ref document: EP Kind code of ref document: A1 |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2010523893 Country of ref document: JP |
|
NENP | Non-entry into the national phase |
Ref country code: DE |