JPH04314870A - Substitution electroless gold plating liquid - Google Patents

Abstract

PURPOSE:To provide a substitution electroless gold plating liquid which contains no cyanide, can be used under neutral plating conditions, does not dissolve a resist, causes deposition of a gold film having good adhesiveness and no appearance defect such as inhomogeneous state, causes no decomposition of itself, causes no precipitation of gold or gold salt even when copper, nickel, or the like in a base body dissolve in the gold plating liquid, and can be used stably for a long time. CONSTITUTION:Ths substitution electroless gold plating liquid contains a water- soluble gold sulfite compd., sulfite, water-soluble polyaminopolycarboxylic acid or its salt, and water-soluble amine or its deriv. This liquid further contains at least one compd, selected from arsenic compds., thallium compds., and lead compds.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substitution electroless gold plating solution which has low toxicity and is capable of providing thin gold film substitution plating with good adhesion stably for a long period of time near neutrality.

0002

[Prior Art] Conventional substitution electroless gold plating solutions often contain cyanide compounds, which are highly toxic. The development of gold plating liquid is desired.

[0003] Autocatalytic thick electroless gold plating has poor adhesion to the underlying base metal, so when performing thick electroless gold plating on base metal, it is necessary to use substitution electroless gold plating on the base metal. After forming the gold film, thick electroless gold plating must be performed. That is, displacement electroless gold plating has become indispensable when performing autocatalytic thick electroless gold plating on base metals.

0004

[Problems to be Solved by the Invention] When gold plating is performed using a substitute electroless gold plating solution on a microcircuit board on which a circuit is formed using a resist, the microcircuit is formed by dissolving the resist in the gold plating solution. The following characteristics are required: no breakage (good patternability), no appearance defects such as unevenness in the deposited gold film, and good adhesion to the underlying metal.

In particular, when displacement gold plating is performed as a base for autocatalytic thick electroless gold plating, a material with good adhesion is required. In addition, the gold plating solution does not self-decompose, and can be used stably for a long time without causing gold or gold salt precipitation even when the base copper, nickel, etc. dissolve in the gold plating solution. A gold plating solution with low toxicity is desirable.

Many conventional substitutional electroless gold plating solutions are highly toxic because they contain cyanide compounds, which poses a safety problem during work, waste liquid treatment, and the like. Furthermore, in a substituted electroless gold plating solution containing cyanide, adhesion deteriorates due to the dissolution of impurities such as copper and nickel. Furthermore, if the glare solution is highly alkaline with a pH of 11.0 or higher, it has the disadvantage that the resist dissolves and the fine circuitry is destroyed. Therefore, if a substituted electroless gold plating solution does not contain cyanide and can be used under neutral plating conditions, such a plating solution can deposit gold with good patternability without dissolving the resist. It is possible to obtain good adhesion without being affected by impurities, and during work,
This is advantageous in terms of safety when treating waste liquid.

The present invention is a substitution electroless gold plating solution developed to solve the above-mentioned problems in conventional substitution electroless gold plating solutions. In other words, the present invention does not contain cyanide compounds, can be used under neutral plating conditions, does not dissolve the resist, and deposits a gold film with good adhesion and patternability without any appearance defects such as unevenness. In addition, the gold plating solution does not self-decompose, and can be used stably for a long time without causing gold or gold salt precipitation even when the base copper, nickel, etc. dissolves in the gold plating solution. The purpose is to provide a replacement electroless gold plating solution.

[0008]

[Means for Solving the Problems] In order to achieve the above objects, the substitutional electroless gold plating solution of the present invention does not contain cyanide compounds, can be used under neutral plating conditions, and can remove resists. It deposits a gold film with good adhesion and patternability without dissolving and without appearance defects such as unevenness, and there is no self-decomposition of the gold plating solution, making it suitable for gold plating solutions on substrates such as copper and nickel. This was developed as a result of research and study to develop a displacement electroless gold plating solution that can be used stably for a long time without causing precipitation of gold or gold salts due to dissolution.

The present invention provides a substituted electroless gold plating solution characterized by containing a water-soluble gold sulfite compound, a sulfite, a water-soluble polyaminopolycarboxylic acid or its salt, and a water-soluble amine or its derivative. It is.

The present invention also provides a substituted electroless gold plating solution, characterized in that the above-mentioned substituted electroless gold plating solution further contains at least one of an arsenic compound, a thallium compound, and a lead compound. .

[0011] The substituted electroless gold plating solution of the present invention will be explained in detail below.

The substituted electroless gold plating solution of the present invention contains a water-soluble gold sulfite compound. Examples of water-soluble gold sulfite compounds include ammonium gold sulfite, potassium gold sulfite,
Examples include sodium gold sulfite. The substituted electroless gold plating solution of the present invention contains 0.5 to 10 g/l, preferably 1 g/l of these water-soluble gold sulfite compounds as gold ions.
It contains ~5g/l. If the content of these water-soluble gold sulfite compounds is less than 0.5 g/l as gold ions, the plating reaction progresses slowly or hardly occurs;
If it is 10 g/l or more, not only will self-decomposition easily occur, but also the adhesion to the base metal will decrease.

The substituted electroless gold plating solution of the present invention contains sulfite. Examples of sulfites include ammonium sulfite, potassium sulfite, and sodium sulfite. The substituted electroless gold plating solution of the present invention contains these sulfites in an amount of 10 g/l to 150 g/l, preferably 30 g/l to 100 g/l. If the content of these sulfites is less than 10 g/l, the gold plating solution will self-decompose and cannot be used stably for a long time, and even if it is more than 150 g/l, almost no commensurate effect will be obtained. There are many cases and it is not economical.

The substituted electroless gold plating solution of the present invention contains a water-soluble polyaminopolycarboxylic acid or a salt thereof. Examples of water-soluble polyaminopolycarboxylic acids or salts thereof include ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, dipotassium ethylenediaminetetraacetate, diammonium ethylenediaminetetraacetate, and nitrotriacetic acid. The substituted electroless gold plating solution of the present invention contains 5 g/l to 80 g/l, preferably 20 g/l to 5 g/l of these water-soluble polyaminopolycarboxylic acids or salts thereof.
Contains 0g/l. If the content of these water-soluble polyaminopolycarboxylic acids or their salts is less than 5 g/l, the gold plating solution becomes susceptible to the effects of impurities such as copper and nickel, resulting in decreased adhesion and self-reflection of the gold plating solution. Decomposition occurs. On the other hand, even if the content of these water-soluble polyaminopolycarboxylic acids or their salts is 80 g/l or more, hardly any commensurate effects are often obtained, which is not economical.

The substituted electroless gold plating solution of the present invention contains a water-soluble amine or a derivative thereof. Examples of water-soluble amines or derivatives thereof include triethanolamine, triethylenetetramine, ethylenediamine, dimethylamine, trimethanolamine, and hydroxylamine hydrochloride. The substituted electroless gold plating solution of the present invention contains these water-soluble amines or their derivatives at 1 g/l.
~10g/l, preferably 2g/l~6g/l. If the content of these water-soluble amines or their derivatives is less than 1 g/l, unevenness tends to occur;
If it is more than l, the appearance of the plated object tends to deteriorate.

The substituted electroless gold plating solution of the present invention may further contain at least one of an arsenic compound, a thallium compound, and a lead compound in addition to the above-mentioned components. Arsenic compounds, thallium compounds and lead compounds include, for example, arsenous acid, arsenic acid or thallium acetate, thallium sulfate, thallium nitrate, thallium chloride or lead acetate, lead nitrate,
Examples include lead chloride. The substitution electroless gold plating solution of the present invention contains at least one of these arsenic compounds, thallium compounds, and lead compounds in a total amount of 1 mg/
l~100mg/l, preferably 2mg/l~50mg
Contains /l. If the total amount of these arsenic compounds, thallium compounds, and lead compounds is less than 1 mg/l, there is little or no effect in suppressing unevenness of the plated material, and 100 mg
/l or more, the appearance of the plated object tends to deteriorate.

The substituted electroless gold plating solution of the present invention has a pH of 5
．． It can be used at pH 6.0 to 8.0.
It is preferable to use 0. If the pH is lower than 5.0 or higher than 10.0, the plating solution not only tends to self-decompose, but also tends to have poor adhesion. Furthermore, if the pH is higher than 10.0, the gold plating solution will dissolve the resist. In addition, as a pH adjuster, sodium hydroxide, potassium hydroxide, ammonium hydroxide, sulfite water, etc. can be used.

The substituted electroless gold plating solution of the present invention has a solution temperature of 4
Although it can be used at 0°C to 95°C, it is preferably used at 50°C to 95°C. If the temperature of the gold plating solution is lower than 40°C, the plating reaction will hardly proceed, and the temperature of 95
Precipitation occurs due to self-decomposition of the plating solution at temperatures higher than ℃, and pattern properties tend to deteriorate.

The substituted electroless gold plating solution of the present invention does not contain cyanide and contains a water-soluble gold sulfite compound, so it has low toxicity and is advantageous for safety during work and waste liquid treatment. Since it can be used under plating conditions, plating with good patterning and adhesion can be achieved without dissolving the resist.

[0020] Furthermore, the substituted electroless gold plating solution of the present invention is
Since it contains a sulfite, a water-soluble polyaminopolycarboxylic acid or its salt, and a water-soluble amine or its derivative, self-decomposition of the water-soluble gold sulfite compound in the plating solution is suppressed. The above-mentioned water-soluble polyaminopolycarboxylic acid or its salt and water-soluble amine or its derivative hide metal impurities due to dissolution of copper, nickel, etc. in the base material, so the substitution electroless gold plating solution of the present invention causes precipitation. It is possible to deposit gold with good adhesion and good appearance without any problems, and to use it stably for a long time.

Furthermore, the substituted electroless gold plating solution of the present invention further improves the appearance of the gold film by containing at least one of an arsenic compound, a thallium compound, and a lead compound.

[0022]

【Example】

[0023]

[Example 1] Line width 50 to 1000μ using resist
A nickel film with a thickness of 5 μm was formed by electroless plating on a 5×5 cm copper-based microcircuit board on which a circuit of m was formed. Hereinafter, the substrate to which this electroless nickel plating was applied will be referred to as a sample.

3g of sodium gold sulfite as gold ion
A substituted electroless gold plating solution containing 30 g/l of ammonium sulfite, 30 g/l of dipotassium ethylenediaminetetraacetate, and 5 g/l of triethanolamine was prepared. The pH of this substituted electroless gold plating solution was adjusted to 7.0 using a pH adjusting reagent, and the sample was immersed in the solution at a temperature of 85° C. for 10 minutes. After 10 minutes, the sample was taken out and the thickness of the deposited film was measured using a fluorescent X-ray film thickness meter. The thickness of the deposited film after 10 minutes was 0.05 μm. When observed visually and using a stereomicroscope, no discoloration of the resist was observed, and the deposited gold film had good adhesion and a lemon yellow color tone.
The appearance was good with no unevenness. Furthermore, the substituted electroless gold plating solution could be used stably for a long time without self-decomposition until the gold ion content in the solution was 0.5 g/l.

[0025]

[Example 2] Gold ammonium sulfite as gold ion 5
A substitution electroless gold plating solution containing 50 g/l of sodium sulfite, 50 g/l of disodium ethylenediaminetetraacetate, 3 g/l of ethylenediamine, and 10 mg/l of lead acetate was prepared. The pH of this substituted electroless gold plating solution was adjusted to 6.0 using a pH adjusting reagent, and the temperature was adjusted to 9.
A sample prepared in the same manner as in Example 1 above was immersed in a temperature of 0° C. for 10 minutes. After 10 minutes, remove the sample and
The deposited film thickness was measured using a line film thickness measuring device. The thickness of the deposited film after 10 minutes was 0.04 μm. When observed visually and using a stereomicroscope, no discoloration of the resist was observed, and the deposited gold film had good adhesion, a lemon yellow color, and a good appearance with no unevenness. Furthermore, the substituted electroless gold plating solution could be stably used for a long time without self-decomposition until the gold ion content in the solution was 0.5 g/l.

[0026]

[Example 3] Gold potassium sulfite as gold ion 2g/
l, potassium sulfite 80g/l, ethylenediamine 4
15g/l of acetic acid, 5g/l of hydroxylamine hydrochloride
A substituted electroless gold plating solution containing 4 mg/l of arsenous acid was prepared. The pH of this substituted electroless gold plating solution was adjusted to 8.0 using a pH adjusting reagent, and the sample prepared in the same manner as in Example 1 was immersed in the solution at a temperature of 90° C. for 10 minutes. After 10 minutes, the sample was taken out and the thickness of the deposited film was measured using a fluorescent X-ray film thickness meter. The deposited film thickness after 10 minutes is 0.0
It was 5 μm. When observed visually and using a stereomicroscope, no discoloration of the resist was observed, and the deposited gold film had good adhesion, a lemon yellow color, and a good appearance with no unevenness. Furthermore, the substituted electroless gold plating solution could be stably used for a long time without self-decomposition until the gold ion content in the solution was 0.5 g/l.

[0027]

[Example 4] Gold ammonium sulfite as gold ion 4
A substitution electroless gold plating solution containing 40 g/l of sodium sulfite, 45 g/l of dipotassium ethylenediaminetetraacetate, 4 g/l of ethylenediamine, and 15 mg/l of thallium nitrate was prepared. The pH of this substituted electroless gold plating solution was adjusted to 7.0 using a pH adjusting reagent, and the sample prepared in the same manner as in Example 1 was immersed in the solution at a temperature of 75° C. for 10 minutes. After 10 minutes, the sample was taken out and the thickness of the deposited film was measured using a fluorescent X-ray film thickness meter. The thickness of the deposited film after 10 minutes was 0.04 μm. When observed visually and using a stereomicroscope, no discoloration of the resist was observed, and the deposited gold film had good adhesion, a lemon yellow color, and a good appearance with no unevenness. Furthermore, the substituted electroless gold plating solution could be stably used for a long time without self-decomposition until the gold ion content in the solution was 0.5 g/l.

Separately, gold ammonium sulfite was added as gold ion at 4 g/l, sodium sulfite was added at 50 g/l, ethylenediaminetetraacetic acid disodium was added at 80 g/l, ammonium thiosulfate was added at 20 g/l, and ethylenediamine was added at 3 g/l.
An autocatalytic electroless gold plating solution containing 25 g/l of hydrazine hydrochloride was prepared. The pH of this autocatalytic gold plating solution was adjusted to 7.0 using a pH adjusting reagent, and the temperature was adjusted to 7.0.
Samples that had been subjected to displacement gold plating using the displacement electroless gold plating solutions and methods shown in Examples 1 to 4 were immersed at 5° C. for 2 hours. After 2 hours, the sample was taken out and the thickness of the deposited film was measured using a fluorescent X-ray film thickness meter. The thickness of the deposited film after 2 hours was about 2.4 μm. The adhesion of each sample was tested by peeling with a tape, and the results showed good adhesion.

Furthermore, in Examples 1 to 4, copper sulfate (2 g/l as copper) was added to the substituted electroless gold plating solution shown in each example.
) or nickel sulfate (2 g/l as nickel), and by the method shown in each example, the gold ion in the liquid was reduced to 0.5 g.
I continued to test until it reached /l. In each of the examples, no significant difference was observed in the dissolution, appearance, stability, and adhesion of the resist compared to the solution to which copper sulfate or nickel sulfate was not added.

[0030]

[Comparative Example 1] 3g of sodium gold sulfite as gold ion
A substituted electroless gold plating solution containing 30 g/l of ammonium sulfite and 5 g/l of triethanolamine was prepared. The pH of this substituted electroless gold plating solution was adjusted to 7.0 using a pH adjusting reagent, and the sample prepared in the same manner as in Example 1 was immersed in the solution at a temperature of 85° C. for 10 minutes. After 10 minutes, the sample was taken out and the thickness of the deposited film was measured using a fluorescent X-ray film thickness meter. The deposited film thickness after 10 minutes is 0.05μ
It was m. When observed visually and using a stereomicroscope, no discoloration of the resist was observed, and the deposited gold film had good adhesion, a lemon yellow color, and a good appearance with no unevenness. However, with the replacement electroless gold plating solution, when plating was repeated, the base copper and nickel dissolved and self-decomposition occurred. Moreover, the appearance and adhesion deteriorated with repeated plating.

[0031] Also, copper sulfate (2 g/l as copper) or nickel sulfate (2 g/l as nickel) was added to the substituted electroless gold plating solution prepared in the same manner as above, and the method shown in Comparative Example 1 was carried out. I did the plating over and over again. As a result, the plating solution self-decomposed after several platings, making it impossible to use it stably for a long period of time.

[0032]

[Comparative Example 2] 3g of sodium gold sulfite as gold ion
A substitution electroless gold plating solution containing 30 g/l of ammonium sulfite and 30 g/l of dipotassium ethylenediaminetetraacetate was prepared. The pH of this substituted electroless gold plating solution was adjusted to 7.0 using a pH adjusting reagent, and the temperature was adjusted to 85.
A sample prepared in the same manner as in Example 1 was immersed for 10 minutes at a temperature of .degree. After 10 minutes, the sample was taken out and the thickness of the deposited film was measured using a fluorescent X-ray film thickness meter. The thickness of the deposited film after 10 minutes was 0.05 μm. When observed visually and using a stereomicroscope, no discoloration of the resist was observed, and the deposited gold film had good adhesion. However, the appearance was uneven. Furthermore, the substituted electroless gold plating solution could be stably used for a long time without self-decomposition until the gold ion content in the solution was 0.5 g/l.

In addition, copper sulfate (2 g/l as copper) or nickel sulfate (2 g/l as nickel) was added to the replacement electroless gold plating solution prepared in the same manner as above, and the method shown in Comparative Example 2 was carried out. I went over and over again. As a result, it could be used stably for a long time without self-decomposition until the gold ion content in the liquid was 0.5 g/l.

[0034]

[Comparative Example 3] 3g of sodium gold sulfite as gold ion
A substituted electroless gold plating solution containing 30 g/l of ammonium sulfite, 30 g/l of dipotassium ethylenediaminetetraacetate, and 5 g/l of triethanolamine was prepared. The pH of this substituted electroless gold plating solution was adjusted to 11.0 using a pH adjusting reagent, and the sample prepared in the same manner as in Example 1 was immersed in the solution at a temperature of 85° C. for 10 minutes. After 10 minutes, the sample was taken out and the thickness of the deposited film was measured using a fluorescent X-ray film thickness meter. The deposited film thickness after 10 minutes is 0.10
It was μm. As a result of visual observation and observation using a stereomicroscope, the resist was slightly dissolved. The deposited gold film had a good appearance with no unevenness, but its adhesion was poor. In addition, in the substitution electroless gold plating solution, the gold ions in the solution are about 1.
Autolysis occurred when the concentration reached 5 g/l.

In addition, copper sulfate (2 g/l as copper) or nickel sulfate (2 g/l as nickel) was added to the replacement electroless gold plating solution prepared in the same manner as above, and the method shown in Comparative Example 3 was carried out. I went over and over again. As a result, the plating solution self-decomposed after several platings, making it impossible to use it stably for a long period of time.

[0036]

[Comparative Example 4] 3g of sodium gold sulfite as gold ion
A substituted electroless gold plating solution containing 30 g/l of ammonium sulfite, 30 g/l of dipotassium ethylenediaminetetraacetate, and 20 g/l of triethanolamine was prepared. The pH of this substituted electroless gold plating solution was adjusted to 7.0 using a pH adjusting reagent, and the sample prepared in the same manner as in Example 1 was immersed in the solution at a temperature of 85° C. for 10 minutes. After 10 minutes, the sample was taken out and the thickness of the deposited film was measured using a fluorescent X-ray film thickness meter. The deposited film thickness after 10 minutes is 0.04
It was μm. Observed visually and using a stereomicroscope,
No discoloration of the resist was observed, and a gold film with good adhesion was deposited, but the color tone was brown and the appearance was uneven, resulting in poor appearance. Furthermore, the substituted electroless gold plating solution could be used stably for a long time without self-decomposition until the gold ion content in the solution was 0.5 g/l.

[0037]

[Effects of the Invention] As explained above, the substitution electroless gold plating solution of the present invention does not contain cyanide compounds, so it has low toxicity and is advantageous in terms of safety.It can be used under neutral plating conditions, so it It is possible to deposit a gold film with good adhesion and no appearance defects such as unevenness without dissolving the resist on the substrate. In addition, the substitutional electroless gold plating solution of the present invention does not self-decompose, and is stable for a long time without causing precipitation of gold or its salts even when it dissolves in the gold plating solution of copper, nickel, etc. It is possible to use.

Therefore, the substitution electroless gold plating solution of the present invention can be used for gold plating on products that require gold plating on microcircuits such as IC frames, printed circuit boards, ceramic substrates, and glass substrates using resists. Ideal for applying glazing.

Claims (2)

[Claims] 1. A substituted electroless gold plating solution comprising a water-soluble gold sulfite compound, a sulfite, a water-soluble polyaminopolycarboxylic acid or a salt thereof, and a water-soluble amine or a derivative thereof. 2. The displacement electroless gold plating solution according to claim 1, which contains at least one of an arsenic compound, a thallium compound, and a lead compound.