KR101638827B1

KR101638827B1 - Method for activating pretreatment of electroless palladium plating and composition of activating solution

Info

Publication number: KR101638827B1
Application number: KR1020150110905A
Authority: KR
Inventors: 한덕곤; 이태호; 권혁석
Original assignee: (주)엠케이켐앤텍
Priority date: 2015-08-06
Filing date: 2015-08-06
Publication date: 2016-07-13

Abstract

The present invention relates to a pretreatment activating liquid composition for electroless palladium plating, which uses a stabilizer and a copper ion elution inhibitor to form a completely fine metal layer of the activator palladium on the copper surface, thereby continuously controlling the palladium plating rate in the electroless palladium plating bath To ensure a constant plating thickness and to maintain the stability of the plating bath. Electrolytic palladium plating on copper surface for ultra-fine circuit line / space (20 μm / 20 μm) providing excellent soldering bonding and wire bondability by preventing voids and pinholes between copper surface and palladium plating layer .

Description

TECHNICAL FIELD The present invention relates to an electroless palladium plating pretreatment activating method and a composition of an activating liquid,

The present invention relates to the electroless palladium plating on electroless nickel plating on the copper circuit surface of ultrafine circuit line / space (20 탆 / 20 탆).

Specifically, before the electroless palladium plating, a very thin palladium film is formed on the copper surface through a separate pretreatment activation process to prevent the copper elution, thereby allowing the electroless palladium plating to be normally performed in the electroless palladium plating bath, And a pretreatment activation process for preventing formation of voids and pinholes between electroless palladium plating layers.

In the case of printed circuit boards (PCB) requiring high reliability, electroless nickel electroless gold plating has been used on the copper surface. This is called Electroless Nickel / Immersion Gold (ENIG) method.

Recently, the use of Sn / Pb solder is prohibited and lead-free solder is used, so that a high melting point solder such as Sn / Ag or Sn / Ag / Cu is used. Nickel is diffused on the surface of the gold-plated film to deteriorate the wire bonding property.

In order to solve the above problem, a method of plating electroless palladium between electroless nickel plating and electroless gold plating has been studied, and this is called ENEPIG (Electroless Nickel / Electroless Palladium / Immersion Gold) method. Palladium plating is very dense and inhibits local corrosion of nickel plating and provides excellent solder jointability and wire bondability. In the ENEPIG process, much research has been done on electroless palladium plating, and in fact, it has been applied to highly reliable products of microcircuits. References related to this are as follows.

Reference literature JP 2007-092092

JP-A-2008-291348

JP-A-2009-113655

US Patent Publication No. US 8,562,727

U.S. Patent Publication No. 7,678,183

Korean Patent Publication No. KR 10-2008-0015936

Korean Patent Publication No. KR 10-2008-0055888

Korean Patent Publication No. KR 10-0994579

Korean Patent Publication No. 10-1023306

The ENEPIG method is very suitable for line / space of 100 μm / 100 μm to 50 μm / 50 μm. Recently, however, ultra-fine circuits have been required for printed circuit boards (PCBs) to meet the trend of miniaturization and high integration of electronic parts, and line / space is required to be 20 탆 / 20 탆. 20 μm / 20 μm processing technology is required for semiconductor bumps, semiconductor package substrates, COF, and flexible substrates. The thickness of the electroless nickel in the ENEPIG method is usually 3 to 8 μm or more. Therefore, when the ENEPIG method is applied to an ultra-fine circuit of 20 탆 / 20 탆, a short circuit occurs due to a bridge phenomenon. In order to solve this problem, the necessity of electroless palladium plating without electroless nickel plating on the copper surface has been strongly demanded since the plating thickness has to be reduced. That is, EPIG (Electroless Palladium / Immersion Gold) method. However, when the electroless palladium plating is performed on the copper surface, the palladium plating is not formed properly due to the increasing copper ions in the plating tank, and many voids and pinholes are generated, and the electroless palladium plating bath is easily decomposed. Electroless palladium plating does not occur at all when copper ions dissolved in the copper surface of the printed circuit board (PCB) reach 5 ppm in the electroless palladium plating bath. References related to this are as follows.

Reference US U.S. Patent No. 8,888,903

U.S. Patent No. 3,285,754

German Published Patent BC 054201129

As printed circuit boards (PCBs) of ultrafine circuits (20 μm / 20 μm) are required, the EPIG method of maintaining the thickness of electroless palladium and electroless gold plating at 0.2 ~ 0.3 μm should be implemented. Separately, pre-treatment activation processes have been newly studied. Related technology for solving such a problem is as follows.

Korean Patent Publication No. 10-2014-0091548

The electroless palladium pretreatment activating solution used palladium salt and 1.2.3 tertiary amines, acid (nitric acid, sulfuric acid, metal sulfonic acid) as a complexing agent, nitrate ion, perchlorate ion and chlorate ion as an oxidizing agent and palladium plating bath Discloses the use of a nitriding complexing agent not containing phosphorus and an organic stabilizing agent containing 1 to 5 phosphonates.

Korean Patent Laid-Open No. 10-2011-0116994

As an electroless palladium pretreatment activating solution, palladium salt and a reducing agent such as hypophosphite, dimethyamine borane, phosphite, and formate salt are disclosed.

Korean Patent No. 10-0712033

Electroless palladium plating is firstly performed on the surface of the printed circuit board copper by palladium plating, and secondarily electroless palladium plating is performed after the porous palladium plating is formed by 0.01 to 1 탆. In addition, it is disclosed that palladium salt is used for the first porous palladium plating, boric acid is used as a buffering agent, polyethylene glycol as a wetting agent, and sulfuric acid, hydrochloric acid and nitric acid as pH adjusting agents.

U.S. Published Patent Application 2013-0288475A1

A method of using palladium sulfate, sulfuric acid, and phosphoric acid as a method of forming a thin metal seed layer of an Angstrom unit on the surface of copper in an activation process as an electroless palladium pretreatment step has been disclosed have.

Both of the above related technologies disclose the necessity and activation method of the pretreatment activation step for plating palladium on the copper surface in the electroless palladium plating method. However, in any case, in the electroless palladium plating bath, Since the elution phenomenon can not be completely blocked, the stability of the plating bath is largely lacked, which causes pinholes and voids between the copper surface and the palladium plating, and the thickness of the electroless palladium plating is not constant. It can be seen that the final reliability of the product, such as final bonding properties, component mounting properties, bonding strength, thermal fatigue properties, and impact properties, is not guaranteed.

In the electroless palladium plating tank, copper ions are eluted from the copper surface of the printed circuit board, thereby causing a rapid reduction in the electroless palladium plating rate and disassembling of the plating bath, which can not be applied to production.

In order to solve these problems, the present invention researched a pretreatment activating liquid composition and a pretreatment activating method which completely cover the copper surface without forming voids and pinholes between the copper surface and the palladium plating layer, and found that there is no copper ion generation in the electroless palladium bath It is possible to maintain the thickness of the palladium plating and obtain the stability of the plating bath which can be used for a long time.

In contrast to the prior art, the inventors of the present invention found that, in the EPIG process, the copper surface is completely covered with the palladium coating in the range of 0.01 to 0.03 μm in the pretreatment activation process for the electroless palladium plating on the copper surface of the ultra fine circuit (20 μm / The present invention has been accomplished on the basis of these findings.

Since the existing activated liquid compositions such as palladium salts, reducing agents, acids and the like can not completely prevent formation of pinholes and pinholes, it is possible to further prevent the dissolution of copper ions on the surface of copper and, at the same time, And a copper ion dissolution inhibitor which inhibits copper ionization by forming a chemical bond with copper on the surface.

Specifically, the present invention has the following embodiments.

An embodiment of the present invention is a pretreatment activating liquid for electroless palladium plating comprising a palladium compound, an ammonium salt, a pH adjusting agent, a copper ion elution inhibitor, a stabilizer and deionized water, wherein the stabilizing agent is EO / PO copolymer (a copolymer of ethylene oxide and propylene oxide), wherein the ratio of EO: PO is from 7: 3 to 6: 4 and the molecular weight is from 4,000 to 8,000 .

[Chemical Formula 1]

(Wherein R represents monohydroxyalkyl or dihydroxyalkyl of 1 to 10 carbon atoms, m represents 50 to 120, and n represents 30 to 70).

In another embodiment of the present invention, the copper ion elution inhibitor is selected from the group consisting of 3-amino-1,2,4-triazole, 1,2,4-triazole, 1,2,3-benzotriazole, 5-methyl-1H-tetrazole, imidazole compounds such as 2-phenylimidazole, 1-vinylimidazole, benzimidazole, 2-butylbenzimidazole, 2- The present invention relates to a pretreatment activating solution using at least one compound selected from the group consisting of imidazole.

Another embodiment of the present invention is a process for preparing a pretreatment activating liquid by adding a palladium compound, an ammonium salt, a pH adjuster, a copper ion elution inhibitor and a stabilizer to deionized water, and the pretreatment activator is heated at a temperature of 20 to 50 ° C for 2 minutes To 7 minutes, comprising the step of using an EO / PO copolymer (a copolymer of ethylene oxide and propylene oxide) represented by the following formula (1) as the stabilizer, in an electroless palladium plating pre- The present invention relates to a method for activating an electroless palladium plating pretreatment.

[Chemical Formula 1]

In another embodiment of the present invention, the palladium compound is at least one selected from the group consisting of palladium chloride, palladium sulfate, palladium oxide, palladium nitrate, palladium acetate, tetraamine palladium chloride, dinitrodiamine palladium and dichlorodiethyleneamine palladium A pretreatment activating solution using two or more compounds, and a pretreatment activating method.

Another embodiment of the present invention relates to a pretreatment activating solution and a pretreatment activating method further comprising one or more acid compounds selected from the group consisting of hydrochloric acid, sulfuric acid and nitric acid.

Another embodiment of the present invention relates to a pretreatment activating liquid and a pretreatment activating method using one or more compounds selected from the group consisting of ammonium chloride, ammonium sulfate and ammonium nitrate.

Another embodiment of the present invention relates to a pretreatment activating liquid and a pretreatment activating method wherein the palladium compound is contained at a palladium concentration of 20 to 100 mg / L.

Another embodiment of the present invention relates to a pretreatment activating liquid and a pretreatment activating method, wherein the copper ion elution inhibitor is 0.01 to 2.00 mmol (mmol) / L.

Another embodiment of the present invention relates to a pretreatment activating liquid and a pretreatment activating method for treating the activator at a temperature of 20 to 50 ° C for 2 to 7 minutes.

Another embodiment of the present invention is a pretreatment activating liquid for electroless nickel plating or electroless silver plating comprising a palladium compound, an ammonium salt, a pH adjuster, a copper ion elution inhibitor, a stabilizer and deionized water, Wherein the ratio of EO: PO is from 7: 3 to 6: 4 and the molecular weight is from 4,000 to 8,000, wherein the EO / PO copolymer (ethylene oxide and propylene oxide copolymer) An activation liquid and a pretreatment activation method.

[Chemical Formula 1]

In the pretreatment of the electroless palladium plating according to the present invention, when the activated solution of the present invention is treated with the activating solution of the present invention, the electroless palladium plating bath can maintain a constant palladium plating rate since there is no copper elution on the copper surface of the substrate, (20 탆 / 20 탆) can be formed by forming voids and pinholes between the copper surface and the palladium plating layer. Thus, it is possible to prevent blurring between circuits, The bonding property and the wire bonding property can be greatly improved.

Fig. 1 shows the results of a line / space plating on a plating substrate for an evaluation substrate of Example 1, a polarizing microscope photograph
Fig. 2 is a graph showing the results of a polarization microscope photograph on the upper surface of the substrate after Line / Space plating on the plating substrate for evaluation substrate of Example 2
Fig. 3 is a graph showing the results of a polarization microscope photograph on the upper surface of the substrate after Line / Space plating in the plating substrate for evaluation substrate of Example 3
Fig. 4 is a graph showing the results of a polarization microscope photograph on the upper surface of the substrate after Line / Space plating on the plating substrate for evaluation substrate of Comparative Example 1. Fig.
Fig. 5 is a graph showing the results of a polarization microscope photograph on the upper surface of the substrate after Line / Space plating on the plating substrate for evaluation substrate of Comparative Example 2. Fig.

Hereinafter, a pretreatment activation method and composition for treating electroless palladium plating on a copper surface according to the present invention will be described in detail.

The pretreatment composition according to the present invention comprises a palladium compound, an acid, an ammonium salt, a stabilizer and a copper ion elution inhibitor.

As the palladium compound used in the present invention, one or two or more species selected from the group consisting of palladium chloride, palladium sulfate, palladium oxide, palladium nitrate, palladium acetate, tetraamine palladium chloride, dinitrodiamine palladium and dichlorodiethyleneamine palladium The above compounds can be used. In one embodiment of the present invention, the palladium compound may include a palladium concentration of 20 to 100 mg / L. When the palladium compound is contained in the composition of the pre-treatment activating liquid of the present invention at a concentration of less than 20 mg / L, there may arise a problem of unplating. When the palladium compound is contained at a concentration exceeding 100 mg / L, There is a problem in that the cost is increased.

As the acid used in the present invention, one or more compounds selected from the group consisting of hydrochloric acid, sulfuric acid and nitric acid can be used. In one embodiment of the present invention, the acid may be included in an amount of 20 to 120 g / L. If the acid is contained in an amount of less than 20 g / L in the pretreatment activating liquid composition of the present invention, there may arise a problem of plating spreading, and when the acid is contained at a concentration exceeding 120 g / L, .

As the ammonium salt used in the present invention, one or a mixture of two or more selected from the group consisting of ammonium chloride, ammonium sulfate and ammonium nitrate may be used. In one embodiment of the present invention, the ammonium salt may be contained at 100 to 2,000 mg / L. When the ammonium salt is included in the pretreatment activating liquid composition of the present invention at a concentration of less than 100 mg / L, the liquid stability may be poor. When the ammonium salt is contained at a concentration exceeding 2,000 mg / L, There may arise a problem of increase.

The stabilizer used in the present invention is an EO / PO copolymer (copolymer of ethylene oxide and propylene oxide) represented by the following formula (1), wherein the ratio of EO: PO is from 7: 3 to 6: 4 And a molecular weight of 4,000 to 8,000.

[Chemical Formula 1]

Here, the ratio of EO: PO is preferably 7: 3 to 6: 4. The molecular weight of the stabilizer is preferably 4,000 to 8,000. Further, m is more preferably in the range of 60 to 110, and most preferably in the range of 70 to 100. Further, n is more preferably in the range of 40 to 60, and most preferably in the range of 44 to 55.

By using the above range, it is possible to form a completely fine metal layer of the activator palladium on the copper surface, to maintain the palladium plating rate in the electroless palladium plating tank constantly to ensure a constant plating thickness and to maintain the stability of the plating bath to be.

The present invention is characterized by the use of a " heliodoxy period " rather than the commonly used EO / PO. By using a " hydroxyl group " rather than a commonly used EO / PO, a uniform plating can be obtained. This is an effect obtained by introducing the substituent into EO / PO. Further, R is monohydroxyisopropyl in view of the voids, spreading and uniformity among the alkylamines.

In one embodiment of the present invention, the stabilizer may contain 2 mg to 10 mg / L. In the pretreatment activating liquid composition of the present invention, when the stabilizer is less than 2 mg / L, voids and pinholes may be generated, and when the stabilizer is more than 10 mg / L, the activator may not be adsorbed.

The copper ion elution inhibitor used in the present invention may be 1,2,4-triazole, 3-amino-1,2,4-triazole, 1,2,3-benzotriazole and 5-methyl- Solvate containing an azole compound comprising a sol and a compound selected from the group consisting of 2-phenylimidazole, 1-vinylimidazole, benzoimidazole, 2-butylbenzimidazole, 2-phenylethylbenzoimidazole, Or a mixture of two or more selected from the above-mentioned compounds. In one embodiment of the present invention, the copper ion elution inhibitor may be contained in an amount of 0.01 to 2.00 mmol (mmol) / L. When the pretreatment activating liquid composition of the present invention contains the copper ion elution inhibitor in a content of less than 0.01 mmol (millimole) / L, there may arise a problem that the copper surface is eroded, and the copper ion elution inhibitor is 2.00 mmol (Millimole) / L, it may interfere with the adsorption of palladium and cause a problem of unplating.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The terms or words used in the present specification and claims should not be construed as limited to ordinary or preliminary meaning and should be construed in accordance with the meaning and concept of the present invention.

The embodiments and drawings described in this specification are preferred embodiments of the present invention and do not represent all the technical ideas of the present invention, so that various equivalents and modifications can be substituted for them at the time of application of the present invention.

Example One

L of palladium sulfate, 70 g / L of sulfuric acid, 0.3 g / L of ammonium sulfate, and 2 mg / L of 1,2,4 triazole in the deionized water were added to the deionized water in accordance with the ingredient contents and conditions shown in [Table 1] And 2 mg / L of EO / PO represented by the following formula (2) to prepare a pretreatment activating solution according to the present invention. Then, the test substrate was treated for 5 minutes at a temperature of 30 ° C in the pretreatment activator bath, Plated.

(2)

In the formula (2), n is 48 and m is 72.

* Test board used

The PCB substrate used in this embodiment was a 0.4 mm thick substrate of SMD (solder mask defined) type. The pitch of the circuits formed on the substrate was 20 μm to 40 μm and the line / space was formed as shown in the figure, and the coating layer interface, circuit and circuit blurring were evaluated, and the cross section was cut with FIB (Focused Ion Beam) Respectively.

Example 2

According to the ingredient contents and conditions shown in Table 1, deionized water was added with 50 mg / L of palladium in palladium chloride, 100 g / L of hydrochloric acid (35%), 0.5 g / L of ammonium chloride, 5 mg / L of 4-triazole and 5 mg / L of EO / PO represented by the formula 2 to prepare a pretreatment activating solution according to the present invention, and then the test substrate was treated for 5 minutes at a temperature of 30 ° C in the pretreatment activator bath Followed by a known electroless palladium plating.

Example 3

According to the ingredient contents and conditions shown in Table 1, 50 mg / L of palladium in palladium sulfate, 70 g / L of sulfuric acid, 0.15 g / L of ammonium sulfate and 3-amino-1,2,4-triazole 5 mg / L of EO / PO represented by Formula 2 was added to prepare a pretreatment activating liquid according to the present invention. After the test substrate was treated at a temperature of 30 ° C. for 5 minutes in the pretreatment activator bath, Electroless nickel plating was performed.

Comparative Example One

According to the contents and conditions shown in Table 1, 50 mg / L of palladium in terms of palladium sulfate, 70 g / L of sulfuric acid and 0.3 g / L of ammonium sulfate were added to deionized water to prepare a pretreatment activating liquid After pretreatment was activated, the test substrate was treated at a temperature of 30 ° C for 5 minutes and then electroless palladium plating was performed.

Comparative Example 2

The pretreatment activating solution was prepared by adding 50 mg / L of palladium sulfate, 70 g / L of sulfuric acid and 0.15 g / L of ammonium sulfate to deionized water in the deionized water according to the contents and conditions shown in Table 1 After the pretreatment was performed, the test substrate was treated at a temperature of 30 ° C for 5 minutes and then subjected to electroless nickel plating known in the art.

compound unit Example Comparative Example One 2 3 One 2 Pd metal (palladium chloride) mg / L 50 Pd metal (palladium sulfate) mg / L 50 50 50 50 Hydrochloric acid (35%) g / L 100 Sulfuric acid g / L 70 70 70 70 Ammonium chloride g / L 0.5 Ammonium sulfate g / L 0.3 0.15 0.3 0.15 1,2,4-triazole mg / L 2 3-amino-1,2,4-triazole mg / L 5 5 EO / PO represented by the formula (2) mg / L 2 5 5 Temperature ℃ 30 30 30 30 50 Processing time minute 5 5 5 5 5 Boyd none none none has exist has exist Smear none none none none has exist Plating uniformity Good Good Good Unplated Good

[Table 1]

FIG. 1 is a photograph showing a polarizing microscope photograph on the upper surface of a substrate after Line / Space plating on a plating substrate for evaluation substrate in Example 1, FIG. 2, Example 2, and FIG. 4 is a photograph showing Comparative Example 1, and FIG. 5 is a photograph showing Comparative Example 2.

[Table 1] and Figs. 1 to 3 are graphs showing the results of the measurement of the electroluminescence spectra of the electroluminescent devices of Examples 1, 2 and 3, as shown in the polarizing microscope photographs on the upper surface of the substrate after Line / Space plating, 2], there was no void between copper and palladium layers as a base metal, and a uniform and excellent plating result was obtained in which no bleeding occurred in a circuit with a line of 20 μm / space of 20 μm.

[Table 1] and Figs. 4 to 5 show the results of a conventional general liquid without using a stabilizer in Comparative Examples 1 and 2 as shown in a polarizing microscope photograph on a substrate upper surface after Line / Space plating on a plating substrate for an evaluation substrate However, the results showed that the voids between the copper and palladium layers as the base metals were severe and the palladium layer was partially not sufficiently uniform after the activator.

The above description is merely illustrative of the technical idea of the present invention and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents thereof should be construed as being included in the scope of the present invention.

Claims

A pretreatment activating liquid for electroless palladium plating comprising a palladium compound, an ammonium salt, a pH adjuster, a copper ion elution inhibitor, a stabilizer and deionized water,
Characterized in that an EO / PO copolymer (a copolymer of ethylene oxide and propylene oxide) represented by the following formula (1) is used as the stabilizer.
[Chemical Formula 1]

The method according to claim 1,
The copper ion elution inhibitor may be at least one selected from the group consisting of 3-amino-1,2,4-triazole, 1,2,4-triazole, 1,2,3-benzotriazole, Solvate and imidazole compounds selected from the group consisting of 2-phenylimidazole, 1-vinylimidazole, benzimidazole, 2-butylbenzimidazole, 2-phenylethylbenzimidazole, 2-aminobenzoimidazole Or a mixture of two or more of these compounds.

The method according to claim 1,
Wherein the palladium compound is at least one compound selected from the group consisting of palladium chloride, palladium sulfate, palladium oxide, palladium nitrate, palladium acetate, tetraamine palladium chloride, dinitrodiamine palladium and dichlorodiethyleneamine palladium Wherein the pretreatment activating liquid is a pretreatment activating liquid.

The method according to claim 1,
Further comprising one or more acid compounds selected from the group consisting of hydrochloric acid, sulfuric acid and nitric acid.

The method according to claim 1,
Wherein the ammonium salt is one or more compounds selected from the group consisting of ammonium chloride, ammonium sulfate and ammonium nitrate.

The method according to claim 1,
Wherein the palladium compound has a palladium concentration of 20 to 100 mg / L.

The method according to claim 1,
Wherein the copper ion elution inhibitor is contained in an amount of 0.01 to 2.00 mmol (mmol) / L.

Preparing a pretreatment activating liquid by adding a palladium compound, an ammonium salt, a pH adjuster, a copper ion elution inhibitor, and a stabilizer to deionized water,
Treating the substrate with the pretreatment activating liquid at a temperature of 20 to 50 ° C for 2 to 7 minutes, the method comprising the steps of:
Characterized in that an EO / PO copolymer (a copolymer of ethylene oxide and propylene oxide) represented by the following formula (1) is used as the stabilizer.
[Chemical Formula 1]

As a pretreatment activating solution for electroless nickel plating or electroless plating including a palladium compound, an ammonium salt, a pH adjuster, a copper ion elution inhibitor, a stabilizer and deionized water,
Characterized in that an EO / PO copolymer (a copolymer of ethylene oxide and propylene oxide) represented by the following formula (1) is used as the stabilizer.
[Chemical Formula 1]