CN113151812B - Tin activating solution, preparation method thereof and chemical nickel plating method - Google Patents
Tin activating solution, preparation method thereof and chemical nickel plating method Download PDFInfo
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- CN113151812B CN113151812B CN202110424692.2A CN202110424692A CN113151812B CN 113151812 B CN113151812 B CN 113151812B CN 202110424692 A CN202110424692 A CN 202110424692A CN 113151812 B CN113151812 B CN 113151812B
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- 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
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/18—Pretreatment of the material to be coated
- C23C18/1803—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces
- C23C18/1824—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces by chemical pretreatment
- C23C18/1827—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces by chemical pretreatment only one step pretreatment
- C23C18/1831—Use of metal, e.g. activation, sensitisation with noble metals
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- 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
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/31—Coating with metals
- C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
Abstract
The invention provides a tin activating solution, a preparation method thereof and a chemical nickel plating method. The tin activating solution comprises the following components in parts by weight: 4-9 parts of tin salt, 15-35 parts of strong acid, 10-25 parts of reducing agent, 15-30 parts of complexing agent and 20-35 parts of stabilizing agent; the preparation and the activation treatment process of the tin activation liquid are easy to regulate and control, and the stability of the activation liquid is good. When the method is applied to the chemical nickel plating process, the chemical nickel plating process can be successfully initiated by introducing the tin metal layer on the copper surface, so that a nickel plating layer with good smoothness and strong binding force is obtained; particularly, the copper-clad laminate shows excellent anti-seepage plating capability in the aspect of circuit board fine line metallization. Compared with the traditional palladium activation process, the method can greatly reduce the production cost.
Description
Technical Field
The invention relates to the technical field of chemical nickel plating, and particularly relates to a tin activation solution, a preparation method thereof and a chemical nickel plating method.
Background
The chemical nickel plating is a method for depositing metal ions on a plated workpiece to obtain a functional plating layer by generating an electron transfer process under the action of a reducing agent based on the principle of redox reaction. For precision parts with complex shapes or blind hole structures and the like, when the operation conditions that the surface of a plated part is in full contact with the plating solution and the fluidity of the plating solution is strong are met, the chemical plating layer with uniform thickness can be formed. Common chemical nickel plating technology is generally applied in the industries of electronics, national defense, aerospace and the like, and the plating layer can continuously complete the deposition process on metal materials and non-metal materials mainly by adjusting the proportion of plating solution components and providing an effective connection mode for ensuring the catalytic activity in the industry, and the plating layer has the characteristics of uniform luster, strong compactness and high corrosion resistance.
The metal substrate-copper and its alloy material in the printed circuit board do not have catalytic activity, if the substrate lacks the active center which initiates the chemical nickel plating process, the deposition process of the chemical nickel plating of sodium hypophosphite which is the reducing system can not be successfully realized. At present, the mainstream activation method is a noble metal palladium solution immersion method, but the increasingly rising cost problem and the phenomena of easy occurrence of diffusion plating and plating leakage are not completely improved. In the doctor's paper "copper surface displacement nickel plating and plating performance research" drafted by Tiandong, the apparent difference of the order of magnitude of the stability constant of the complex between thiourea and monovalent copper ions and nickel ions is utilized to replace the palladium activation method with the displacement nickel plating method, thereby successfully initiating the deposition process of chemical nickel on the PCB circuit. However, the chemical nickel plating process is accompanied by the problem of thiourea accumulation, and the growth of the nickel layer is greatly hindered. Chinese patent CN107868947A provides a preparation method of an activation solution for chemical nickel plating with high stability, which uses amine borane compound as a reducing agent to generate a thinner nickel activation layer on the surface of a copper substrate, and further initiates a subsequent chemical nickel plating process, but when plating is carried out under a high temperature condition, dimethylamino borane has the disadvantage of too fast consumption, the utilization rate of raw materials is not high, and part of the production cost is increased. In chinese patent CN111778496A, aiming at the problem of nickel plating layer deposition in LDS mobile phone antenna technology, a combination of tin salt and molybdenum/cobalt/tungsten/iron metal salt is used as an activator, thereby realizing chemical nickel plating process, but still phenomena such as plating leakage caused by insufficient catalytic activity occur.
Therefore, the method has the advantages of high stability, simple preparation process and more economic production cost, can avoid the problem of diffusion plating, effectively initiates chemical nickel plating, and quickly obtains various functional nickel coatings, and has important practical significance.
Disclosure of Invention
Based on the problems of low raw material utilization rate, high production cost, high fluctuation of coating quality and the like in the existing chemical nickel plating technology, the invention aims to provide a tin activating solution. The preparation and activation treatment processes of the tin activation liquid are easy to regulate and control, and the stability of the activation liquid is good. Under strong acid condition, a tin metal layer with catalytic activity is pre-plated on the surface of copper, and tin activation sites are introduced to obtain a smooth plating layer without a naked matrix, strong binding force and good corrosion resistance; while leakage in the thin line can be effectively prevented.
The invention also aims to provide an electroless nickel plating method.
In order to realize the purpose, the technical scheme of the invention is as follows:
a tin activating solution comprises the following components in parts by weight: 4 to 9 parts of tin salt, 15 to 35 parts of strong acid, 10 to 25 parts of reducing agent, 15 to 30 parts of complexing agent and 20 to 35 parts of stabilizing agent.
Tin is a high-hydrogen over-potential metal, and the addition of a reducing agent can provide electrons required for the deposition of a tin layer on the surface of copper, so that a stable tin layer can be successfully obtained in an acidic plating solution. The acid condition increases the solubility of the tin salt, and can further maintain the stability of the plating solution; the complexing agent may form [ Cu (NH) ] with the copper substrate 2 CSNH 2 ) 4 ] 2+ The complex compound further reduces the potential difference between the copper layer and the tin layer and promotes the process of activating the tin layer required by the rapid growth of the surface of the base material. The stabilizer can inhibit the hydrolysis of divalent tin ions in the activating solution and maintain the uniformity of the plating solution; in addition, the stabilizer is also one of auxiliary complexing agents of copper ions, can accelerate the negative shift process of the electrode potential of copper, and synergistically improves the speed of obtaining the tin activated layer.
According to the technical scheme, under the strong acid condition, a tin metal layer with catalytic activity is pre-plated on the surface of copper, a tin activation site is introduced, and the purpose of initiating nickel plating is achieved through a chemical tin plating route.
Tin salts, strong acids, reducing agents, complexing agents, stabilizers, which are commonly used in the art, may be used in the present invention.
Preferably, the tin salt is one or more of stannous sulfate, stannous chloride or stannic methylsulfonate.
Preferably, the strong acid is one or more of sulfuric acid, hydrochloric acid, an organic sulfonic acid, or an organic carboxylic acid.
Preferably, the reducing agent is one or more of potassium hypophosphite, sodium hypophosphite, ammonium hypophosphite, sodium borohydride or sodium formate.
Preferably, the complexing agent is a sulphur-containing compound, such as one or more of sodium sulphide, thiourea, thiol or thioether.
Preferably, the stabilizer is a substance capable of generating a chelating reaction with copper, and specifically is one or more of malic acid, gluconic acid, tartaric acid, ethylenediaminetetraacetic acid, sodium alginate, citric acid or sodium citrate.
Preferably, the pH of the tin activation solution is 1 to 3.
After the tin metal layer is attached to the surface of the copper substrate, in the environment of high-temperature acid chemical plating, the movement and transfer processes of electrons in the plating solution are facilitated, hydrogen free radicals are released by the breakage of P-H bonds in hypophosphite molecules, nickel ions in the plating solution and atomic hydrogen adsorbed on the surface of an active metal layer are subjected to replacement reaction, the nickel ions adsorbed on the surface of a substrate are further aggregated to form nickel particles with autocatalytic activity, and the purpose of chemical nickel plating on a copper wire is achieved through the process of introducing tin activation sites.
A preparation method of an anti-seepage plating tin activating solution comprises the steps of fully mixing and uniformly stirring tin salt, strong acid, a reducing agent, a complexing agent and a stabilizing agent to obtain the tin activating solution.
In order to realize the aim, the invention also provides a chemical nickel plating method, which mainly comprises the following steps:
s1, pretreatment of a base material: firstly, carrying out oil removal and microetching treatment on the surface of a copper substrate to obtain a fresh clean copper surface which is tightly combined with a subsequent plating layer;
s2, activation: immersing the treated copper substrate in the tin activation solution of any one of claims 1 to 7, wherein the activation operation temperature is 0-60 ℃, and the activation time is 5-100 s;
s3, chemical nickel plating: and (3) washing the activated workpiece with deionized water, immersing the workpiece in chemical nickel plating solution at the temperature of 75-90 ℃, and reacting for 5-30 min to finish the chemical nickel plating process.
Electroless nickel plating solutions conventional in the art may be used in the present invention. The invention also provides a superior plating solution system, which is combined according to the following steps: the chemical nickel plating solution is prepared from 15g/L of nickel salt, 25g/L of sodium hypophosphite, 10g/L of sodium acetate, 10g/L of sodium succinate, 5g/L of citric acid, 8g/L of malic acid, 3mL/L of lactic acid and 0.001g/L of thiourea, and one of sodium hydroxide, potassium hydroxide, ammonium chloride and ammonia is used for adjusting the pH value of the plating solution to 4.8.
Preferably, the activation temperature in step S2 is 10 to 40 ℃ and the activation time is 10 to 60S.
Preferably, the electroless nickel plating reaction time in step S3 is 15min.
Compared with the prior art, the invention has the following beneficial effects:
(1) The activating solution with higher economical efficiency is used for replacing a palladium activating mode, the purpose of chemical nickel plating on the copper wire is realized by introducing a tin activating site, the manufacturing cost of the wire can be gradually reduced, and the production flow is optimized.
(2) The chemical nickel plating method of the tin activation liquid has obvious effect, and obtains a smooth plating layer without a naked matrix, strong binding force and good corrosion resistance; while effectively preventing leakage problems in thin lines.
(3) The preparation and activation treatment processes of the tin activation solution are easy to regulate, and the activation solution has good stability and is suitable for large-scale production in the fields of electronic products and the like.
Drawings
FIG. 1 is a photograph showing the appearance of a plated article after electroless nickel plating in example 1;
FIG. 2 is an SEM photograph of the surface of a plated article after electroless nickel plating of example 1;
FIG. 3 is a graph of the open circuit potential monitored in the electroless nickel plating solution of example 1;
FIG. 4 is a Tafel plot obtained after electroless nickel plating of example 1 and comparative example 1, tested in a 3.5% sodium chloride solution;
FIG. 5 is a schematic diagram showing the phenomenon of diffusion plating on a workpiece having a fine line after electroless nickel plating using a palladium activation process in comparative example 1;
FIG. 6 is a graph showing the distribution of nickel grain growth on a workpiece having fine lines after electroless nickel plating in example 1.
Detailed Description
The present invention will be further described with reference to specific embodiments, but the present invention is not limited to the examples in any way. The starting reagents used in the examples of the present invention are those conventionally purchased, unless otherwise specified. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without inventive step, shall fall within the scope of protection of the present invention.
Example 1
(1) A tin activating solution:
dissolving 10mL of concentrated sulfuric acid in 300mL of deionized water, and adding 3g of stannous sulfate medicine in batches in the heat release process to uniformly disperse the stannous sulfate medicine in the solution to obtain a solution a; dissolving 10g of sodium hypophosphite in 100mL of deionized water to obtain a solution b; dissolving 2g of gluconic acid, 5g of citric acid, 2g of sodium alginate, 1g of potassium sodium tartrate and 10g of thiourea in 200mL of deionized water to obtain a solution c; and (3) uniformly mixing the solution c and the solution b, adding the mixture into the solution a, fully stirring and mixing the mixture, and performing constant volume to prepare 1L of tin activation solution with the pH value of 2.4.
(2) An electroless nickel plating method mainly comprises the following steps:
s1, pretreatment of a base material: the copper substrate is placed in deoiling liquid containing 8g/L of sodium hydroxide, 5g/L of sodium carbonate and 2g/L of sodium silicate for first washing, the operation temperature is 50 ℃, and the time is 2min. And immersing the copper sheet washed by the deionized water into a microetching solution containing 20g/L of sodium persulfate and 50mL/L of concentrated sulfuric acid for secondary washing, washing for 30s at normal temperature, and then washing by using the deionized water for later use.
S2, activation: keeping the temperature of the tin activating solution prepared in the step (1) constant to 10 ℃, transferring the cleaned clean copper substrate, immersing the cleaned clean copper substrate in the activating solution, keeping the temperature for 20s, observing that the copper surface is completely covered by the tin layer after reaction, and quickly cleaning the sample in flowing deionized water for multiple times;
s3, chemical nickel plating: and (3) drying the copper substrate activated in the step (S2), and then putting the dried copper substrate into a chemical nickel plating solution, heating the copper substrate into the chemical nickel plating solution to 85 ℃, and plating for 15min to finish the chemical nickel plating process.
The chemical nickel plating solution comprises: respectively dissolving 15g/L nickel sulfate and 25g/L sodium hypophosphite into 100mL deionized water, and sequentially marking as W1 and W2 solutions; then dissolving 10g/L sodium acetate, 5g/L citric acid, 8g/L malic acid and 10g/L sodium succinate in 300mL deionized water, and marking as a W3 solution; fully mixing the W1 solution and the W3 solution, adding 3mL/L lactic acid into the mixed solution, and marking as a W4 solution after uniformly stirring; and finally, adding 0.001g/L of thiourea and the W2 solution into the W4 solution, and adjusting the pH value of the plating solution to 4.8 by using an ammonia solution after constant volume.
Example 2
(1) A tin activating solution:
dissolving 2g of stannous chloride in a hydrochloric acid solution with the mass fraction of 10% to obtain a solution a; 4g of ammonium hypophosphite is dissolved in 100mL of deionized water to obtain a solution b; dissolving 3g of citric acid, 5g of malic acid, 2g of gluconic acid and 5g of thiourea in 100mL of deionized water to obtain a solution c; and (3) uniformly mixing the solution c and the solution b, adding the mixture into the solution a, fully stirring and mixing the mixture, and performing constant volume to prepare 1L of tin activation solution with the pH value of 1.9.
(2) An electroless nickel plating method mainly comprises the following steps:
s1, pretreatment of a base material: putting the copper substrate into deoiling liquid containing 10g/L of sodium hydroxide, 5g/L of sodium carbonate and 1g/L of sodium silicate for first washing, wherein the operation temperature is 50 ℃, and the operation time is 2min;
immersing the copper sheet washed by the deionized water into a microetching solution containing 20g/L of sodium persulfate and 50mL/L of concentrated sulfuric acid for secondary washing, washing for 30s at normal temperature, and then washing with the deionized water for later use;
s2, activation: keeping the temperature of the tin activation solution prepared in the step (1) at 20 ℃, moving the cleaned clean copper substrate to immerse the cleaned clean copper substrate in the activation solution, keeping the temperature for 35s, observing that the copper surface is completely covered by a tin layer after reaction, and quickly cleaning the sample in flowing deionized water for multiple times;
s3, chemical nickel plating: and (3) drying the activated copper substrate in the S2, and then putting the dried copper substrate into a chemical nickel plating solution, heating the copper substrate into the chemical nickel plating solution to 88 ℃ for plating for 15min, thereby completing the chemical nickel plating process.
The electroless nickel plating solution used was the same as in example 1.
Example 3
(1) A tin activating solution:
dissolving 2g of stannous chloride in a hydrochloric acid solution with the mass fraction of 10% to obtain a solution a; 5g of ammonium hypophosphite is dissolved in 100mL of deionized water to obtain a solution b; dissolving 7g of citric acid, 1g of ethylenediamine tetraacetic acid, 2g of gluconic acid and 10g of thiourea in 100mL of deionized water to obtain a solution c; and (3) uniformly mixing the solution c and the solution b, adding the mixture into the solution a, fully stirring and mixing the mixture, and fixing the volume to prepare 1L of tin activation solution with the pH value of 2.7.
(2) An electroless nickel plating method mainly comprises the following steps:
s1, pretreatment of a base material: putting the copper substrate into deoiling liquid containing 8g/L of sodium hydroxide, 5g/L of sodium carbonate and 2g/L of sodium silicate for first washing, wherein the operation temperature is 50 ℃, and the operation time is 2min; immersing the copper sheet washed by the deionized water into a microetching solution containing 20g/L of sodium persulfate and 50mL/L of concentrated sulfuric acid for secondary washing, washing for 30s at normal temperature, and then washing with the deionized water for later use;
s2, activation: keeping the temperature of the tin activating solution prepared in the step (1) to 40 ℃, moving the cleaned clean copper substrate to immerse the cleaned clean copper substrate in the activating solution, keeping for 45s, observing that the copper surface is completely covered by a tin layer after reaction, and quickly cleaning the sample in flowing deionized water for many times;
s3, chemical nickel plating: and (3) drying the activated copper substrate in the step (S2), and then putting the dried copper substrate into a chemical nickel plating solution, heating the copper substrate into the chemical nickel plating solution to 82 ℃ for plating for 15min, thereby completing the chemical nickel plating process.
The electroless nickel plating solution used was the same as in example 1.
Example 4
(1) A tin activating solution:
dissolving 5g of stannous chloride in a hydrochloric acid solution with the mass fraction of 10% to obtain a solution a; dissolving 12g of sodium hypophosphite into 100mL of deionized water to obtain a solution b; dissolving 10g of sodium citrate, 5g of malic acid, 1g of sodium alginate and 15g of thiourea in 100mL of deionized water to obtain a solution c; and (3) uniformly mixing the solution c and the solution b, adding the mixture into the solution a, fully stirring and mixing the mixture, and fixing the volume to prepare 1L of tin activation solution with the pH value of 1.5.
(2) An electroless nickel plating method mainly comprises the following steps:
s1, pretreatment of a base material: putting the copper substrate into deoiling liquid containing 6g/L of sodium hydroxide, 4g/L of sodium carbonate and 5g/L of sodium silicate for first washing, wherein the operation temperature is 50 ℃, and the operation time is 2min; immersing the copper sheet washed by the deionized water into a microetching solution containing 20g/L of sodium persulfate and 50mL/L of concentrated sulfuric acid for secondary washing, washing for 30s at normal temperature, and then washing with the deionized water for later use;
s2, activation: keeping the temperature of the tin activating solution prepared in the step (1) to 25 ℃, moving the cleaned clean copper substrate to immerse the cleaned clean copper substrate in the activating solution, keeping the temperature for 60s, observing that the copper surface is completely covered by a tin layer after reaction, and quickly cleaning the sample in flowing deionized water for multiple times;
s3, chemical nickel plating: and (3) drying the activated copper substrate in the S2, and then putting the dried copper substrate into a chemical nickel plating solution, heating the copper substrate into the chemical nickel plating solution to 88 ℃ for plating for 15min, thereby completing the chemical nickel plating process.
The electroless nickel plating solution used was the same as in example 1.
As can be seen from the appearance data results, FIG. 1 and FIG. 2 are the appearance photograph and surface SEM image of the electroless nickel plated article of example 1, respectively. As can be seen from the appearance diagram, the obtained plated part has flat, smooth and glossy appearance; from SEM pictures, the obtained electroless nickel plating layer has a typical cellular nickel-phosphorus structure, and nickel particles are uniformly distributed. The appearance effect of the electroless nickel plated layers obtained in examples 2 to 4 was similar to that in example 1.
According to the results of the examples 1 to 4, the conclusion that the palladium-free activation mode provided by the invention can successfully initiate electroless nickel plating is verified, and a plating layer which is good in flatness, strong in binding force and easy to prepare is obtained. The bonding force performance of the plating layer is evaluated by using a scratch test method, a bending test method and a thermal shock test method, and the nickel layer has no phenomena of falling, bubbling, peeling and the like, so that the obtained nickel plating layer has good bonding force. Meanwhile, the activation process is convenient to regulate and control, the activation solution has good stability, and the method has outstanding practical significance for simplifying the current line production flow and reducing the process cost.
Comparative example 1
And (3) carrying out an electroless nickel plating experiment by using palladium activation treatment, wherein the palladium activation solution is prepared according to the composition ratio in a conventional experiment. The experiment provides a conventional palladium activating solution, which comprises the following components in percentage by weight: 0.05g/L of palladium chloride and 10mL/L of concentrated hydrochloric acid with the mass fraction of 36.5 percent. The specific process is as follows:
s1, pretreatment of a base material: the substrate pretreatment process was the same as in example 1;
s2, activation: and (3) placing the obtained clean material in a palladium activation solution for 20s, keeping the operation temperature at 20 ℃, and cleaning and drying the clean material by using deionized water after the activation is finished.
S3, chemical nickel plating: the conditions were kept the same as in example 1, and a nickel-plated sample after palladium activation was obtained.
Analysis of Performance test results
Open circuit potential and Tafel test experiments were performed using the Shanghai Hua CHI760E electrochemical workstation measurement system, respectively.
(1) As can be seen from the open circuit potential curve in FIG. 3, the potential decreases in a stepwise manner during the electroless nickel plating process. After the tin metal layer is attached to the surface of the base material, the movement and transfer processes of electrons in the plating solution are facilitated under the environment of high-temperature acid chemical plating, hydrogen free radicals are released by the breakage of P-H bonds in hypophosphite molecules, nickel ions are combined with the hydrogen free radicals and adsorbed on the surface of the base body to further aggregate to form nickel particles with autocatalytic activity, when the nickel particles completely cover the surface of a plated part, the potential enters a stable platform area, the potential value is basically maintained to be-0.63V-0.67V, the deposition potential of nickel is in the area of-0.7V-0.6V, and the applied activation mode successfully initiates the chemical nickel plating reaction.
(2) As can be seen from the results of the Tafel test in FIG. 4 and Table 1, the corrosion potentials of the electroless nickel layers obtained in example 1 were-0.442V, respectively, and example 1 after activation with tin had a greater value of corrosion potential than the corrosion potentials of the nickel layers obtained after activation with palladium (i.e., comparative examples 1, -0.556V); and its corrosion current (1.386X 10) -7 A) Is obviously less than the corrosion current (2.976 multiplied by 10) of the electroless nickel coating obtained by the traditional palladium activation (namely, the comparative example 1) -7 A) In that respect Therefore, the chemical nickel-plating layer obtained in the example 1 has smaller corrosion current and higher corrosion resistance than the nickel layer obtained after palladium activation,is more suitable for the large-scale production in the electronic circuit industry.
TABLE 1 statistics for corrosion current and corrosion potential in FIG. 4Tafel curves
(3) Fig. 5 is a schematic diagram of the diffusion plating phenomenon on a workpiece having a fine line after chemical nickel plating is performed by a palladium activation process in comparative example 1, which reflects the diffusion plating phenomenon on the fine line of the chemical nickel plating layer obtained by the palladium activation process adopted in the industry at present. This is because in the palladium activation process, palladium particles are deposited and attached on the metal substrate and the adjacent position of the metal substrate, and the palladium component is difficult to remove by the conventional cleaning step, so that the subsequent nickel plating process is caused to generate diffusion plating.
FIG. 6 is a schematic diagram showing the distribution of nickel grain growth on a workpiece having fine lines after electroless nickel plating using tin activation in example 1. As can be seen from the figure, the surface of the line is smooth and flat without the phenomenon of diffusion plating when observed under a metallographic microscope. The method for chemically plating nickel by using the tin activating solution can effectively solve the problem of diffusion plating of the thin line workpiece in the nickel plating process.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (4)
1. The tin activating solution is characterized by comprising the following components in parts by weight: 4-9 parts of tin salt, 15-35 parts of strong acid, 10-25 parts of reducing agent, 15-30 parts of complexing agent and 20-35 parts of stabilizer;
the tin salt is one or more of stannous sulfate, stannous chloride or tin methanesulfonate;
the strong acid is one or more of sulfuric acid, hydrochloric acid, organic sulfonic acid or organic carboxylic acid;
the reducing agent is one or more of potassium hypophosphite, sodium hypophosphite, ammonium hypophosphite, sodium borohydride or sodium formate;
the complexing agent is one or more of sodium sulfide, thiourea, mercaptan or thioether;
the stabilizer is one or more of malic acid, gluconic acid, tartaric acid, ethylenediamine tetraacetic acid, sodium alginate, citric acid or citric acid sodium salt;
the pH value of the tin activation liquid is 1 to 3.
2. The method for preparing the tin activating solution according to claim 1, wherein the tin activating solution is obtained by sufficiently and uniformly mixing a tin salt, a strong acid, a reducing agent, a complexing agent and a stabilizer.
3. An electroless nickel plating method is characterized by comprising the following steps:
s1 activation: immersing the copper substrate subjected to oil removal and microetching in the tin activation solution of claim 1, wherein the operation temperature is 0-60 ℃, and the activation time is 5-100s;
s2, chemical nickel plating: and (3) washing the activated workpiece with deionized water, and immersing the workpiece in chemical nickel plating solution at 75-90 ℃ for reaction for 5-30min.
4. An electroless nickel plating method according to claim 3, wherein the activation temperature in step S1 is 10 to 40 ℃, and the activation time is 20 to 60s.
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| CN104152874B (en) * | 2014-07-20 | 2017-06-09 | 珠海伟华化工有限公司 | A kind of printed wiring board electroless copper activating solution |
| CN104928658B (en) * | 2015-05-13 | 2017-10-17 | 电子科技大学 | A kind of method that activation PCB circuit surfaces realize chemical nickel plating |
| CN109023316A (en) * | 2018-07-31 | 2018-12-18 | 广东利尔化学有限公司 | A kind of wiring board activating solution and its activation method |
| CN111778496B (en) * | 2020-07-14 | 2022-04-19 | 赤壁市聚茂新材料科技有限公司 | Activating agent for nickel plating of tin alloy activated copper layer and nickel plating method |
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2021
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