JP2005105318A - Electroless gold-plating liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an autocatalyst type electroless gold-plating liquid excellent in liquid stability and having a high plating rate. <P>SOLUTION: The electroless gold-plating liquid comprises the salt of gold sulfite, a complexing agent and a reducing agent, and further comprises one or more selected from glycolic acid, diglycolic acid and their salts. As the complexing agent, e.g., water-soluble aminocarboxylic acid or water-soluble amine is used. As the reducing agent, at least one selected from a hydrazine compound, hydroquinone, its derivative, pyrogallol and its derivative is used. Further, at least one selected from an arsenic compound, a thallium compound and a lead compound, and a benzotriazole compound as a base metal elution inhibitor are preferably incorporated therein. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electroless gold plating solution capable of performing thick gold plating stably for a long time on a fine wiring board or the like of a copper substrate and having a high deposition rate.

  Gold is widely used for plating electronic parts because it has good electrical conductivity, is soft, and has very stable chemical properties.

  Conventionally, electroplating has been used for the surface treatment of wiring on circuit boards. However, due to the recent increase in circuit design density, it is difficult to route plating current wiring. The electroless plating method is indispensable because of problems such as noise generation. The electroless gold plating method is also widely used as a method for performing gold plating on an independent circuit pattern.

  The plating of wiring on the circuit board requires a gold film thickness of 0.2 μm or more from the viewpoint of connection reliability when wire bonding is performed. The autocatalytic plating method is suitable for obtaining a gold film thickness of 0.2 μm or more by the electroless plating method. The autocatalytic plating method utilizes the action of reducing the gold salt of the reducing agent using a gold plating solution containing a gold salt and a reducing agent. In the autocatalytic plating method, the thickness of the gold film continues to increase with the progress of the oxidizing reaction of the reducing agent even after the gold has completely covered the base metal, so that thick gold plating is possible.

  Many autocatalytic electroless gold plating solutions have been developed so far, but there are many plating solutions that use gold cyanide as a gold ion source and perform plating with high alkalinity. A plating solution containing a gold cyanide salt has a problem of high toxicity and low durability of the resist.

  On the other hand, as an electroless plating solution not containing a cyanide compound, for example, there is a plating solution described in Japanese Patent No. 3030114 (Patent Document 1). Since this electroless plating solution does not contain a cyanide compound, its toxicity is low and its pH is neutral, so that the durability of the resist is excellent.

  However, the plating solution described in Japanese Patent No. 3030114 uses ethylenediaminetetraacetic acid as the water-soluble polyaminocarboxylic acid. The use of ethylenediaminetetraacetic acid is aimed at complexing metal impurities, but because the complexing power is too strong, not only the metal impurities are complexed but also adsorbed on the surface of the plating material, greatly hindering gold deposition. Reduce the deposition rate of the plating. If ethylenediaminetetraacetic acid is removed from the plating solution, the deposition rate can be expected to increase, but gold particles are deposited during heating or during plating, resulting in liquid decomposition, resulting in a drastic decrease in solution stability and plating solution. It does not hold as. Thus, while ethylenediaminetetraacetic acid contributes to the stability of the plating solution, it slows down the gold deposition rate, making it very difficult to satisfy both high-speed plating and maintenance of solution stability. is there.

As described above, ethylenediaminetetraacetic acid is indispensable as a stabilizer for gold sulfite complex and a complexing agent for metal impurities, so that it is used in many non-cyanide autocatalytic plating solutions. However, in recent years, it has been revealed that ethylenediaminetetraacetic acid is poorly degradable by microorganisms, stays in the environment for a long time, and adversely affects the aqueous environment. In addition, it falls under the scope of chemical substances management promotion law (PRTR law) and its use is restricted in various fields. For this reason, development of a plating solution that does not use ethylenediaminetetraacetic acid is also required in electroless gold plating.
Japanese Patent No. 3030114 (Claim 1)

  The object of the present invention is to provide a self-catalyzed electroless gold plating solution that does not contain highly toxic gold cyanide salt and has excellent solution stability and high plating speed without using ethylenediaminetetraacetic acid, which has a high environmental load. There is to get.

  As a result of earnest research, the present inventor has added gold cyanide salt by adding one or more selected from glycolic acid, diglycolic acid and salts thereof to a plating solution containing gold sulfite, a complexing agent and a reducing agent. In addition, the present inventors have found that a plating solution having excellent liquid stability and a high plating rate can be obtained without using ethylenediaminetetraacetic acid.

  [1] An electroless gold plating solution containing gold sulfite, a complexing agent and a reducing agent, wherein the electroless gold plating solution contains at least one selected from glycolic acid, diglycolic acid and salts thereof Plating solution.

  [2] The electroless gold plating solution according to [1], wherein the complexing agent is a water-soluble aminocarboxylic acid or water-soluble amine excluding ethylenediaminetetraacetic acid (EDTA).

  [3] The electroless gold plating solution according to [1] or [2], wherein at least one of a hydrazine compound, hydroquinone and a derivative thereof, pyrogallol and a derivative thereof is used as a reducing agent.

  [4] The electroless gold plating solution according to any one of [1] to [3], which contains at least one of an arsenic compound, a thallium compound, and a lead compound.

  [5] The electroless gold plating solution according to any one of [1] to [4], which contains a benzotriazole-based compound as a base metal elution inhibitor.

  Since the electroless plating solution of the present invention uses gold sulfite instead of gold cyanide, it has low toxicity and is advantageous in terms of safety. Since gold cyanide salt is not used, it can be used under neutral plating conditions. Therefore, gold is deposited with good pattern formation without dissolving the resist on the fine circuit board. Furthermore, by using one or more selected from glycolic acid, diglycolic acid and salts thereof, liquid stability can be maintained without using ethylenediaminetetraacetic acid, which is a target substance of the PRTR method, and the environmental load is reduced. Can be reduced. In addition, when ethylenediaminetetraacetic acid is used, it is possible to improve the decrease in the deposition rate of the plating, which was conventionally unavoidable, and to increase the plating rate.

  In addition, if the electroless plating solution of the present invention is used, since there is no dissolution of the base material such as copper and nickel into the plating solution, unevenness, gas pits, etc. occur without causing partial abnormal precipitation of gold or deterioration of pattern formation. It is possible to obtain a gold film having no appearance defects. Furthermore, since there is no penetration of copper that degrades the liquid stability of the gold plating solution, the plating solution can be used stably for a long time without causing self-decomposition.

  The electroless gold plating solution of the present invention is optimal for gold plating on a fine circuit such as an IC frame, a printed circuit board, a ceramic substrate, or a wafer not using a resist using a copper base resist.

  Hereinafter, the electroless gold plating solution of the present invention will be described in detail.

  The electroless gold plating solution of the present invention uses gold sulfite as a gold ion source. Examples of the gold sulfite include gold ammonium sulfite, gold potassium sulfite, and sodium gold sulfite. The gold ion concentration of the electroless gold plating solution of the present invention is preferably 1 to 8 g / L, and more preferably 2 to 5 g / L. When the gold ion concentration is less than 1 g / L, the plating reaction proceeds slowly or hardly occurs. On the other hand, if it exceeds 8 g / L, the stability of the gold ions is lowered, and gold particles are generated and precipitated in the gold plating solution, which easily leads to self-decomposition.

  It is preferable to use a water-soluble aminocarboxylic acid or a water-soluble amine as a complexing agent in the electroless gold plating solution of the present invention. By using a water-soluble aminocarboxylic acid or a water-soluble amine as a complexing agent, autolysis of gold sulfite in the plating solution is suppressed. In addition, when these complexing agents are used, the plating solution does not cause precipitation because it conceals metal impurities caused by the penetration of the base metals such as copper and nickel. It can be deposited.

  Examples of the water-soluble aminocarboxylic acid and water-soluble amine used as a complexing agent include water-soluble aminocarboxylic acids such as nitrilotriacetic acid, iminodicarboxylic acid, glycine, glutamic acid, and aspartic acid, and salts thereof; Examples thereof include water-soluble amines such as ethylenetetramine, ethylenediamine, dimethylamine, hydroxyamine, methylglycine diacetate (manufactured by BASF, Trilon M) and salts thereof.

  Although it is possible to use ethylenediaminetetraacetic acid (EDTA), which is a water-soluble aminocarboxylic acid, as the complexing agent, it is preferable not to use EDTA because of the large environmental burden as described above.

  When the electroless gold plating solution of the present invention uses a water-soluble aminocarboxylic acid as a complexing agent, the content is preferably 10 to 150 g / L, more preferably 10 to 100 g / L. . If the content of the water-soluble aminocarboxylic acid is less than 10 g / L, the gold plating solution is easily affected by metal impurities such as nickel, and the solution stability is lowered. If it exceeds 150 g / L, it is difficult to obtain an effect corresponding to it, and it is not economical. When a water-soluble amine is used as the complexing agent, the content is preferably 1 to 10 g / L, and more preferably 2 to 6 g / L. When the content of the water-soluble amine is less than 1 g / L, there is no gas pit suppressing effect, and when it exceeds 10 g / L, the appearance of the plated product tends to be deteriorated.

  The electroless gold plating solution of the present invention preferably uses at least one of a hydrazine compound, hydroquinone and a derivative thereof, pyrogallol and a derivative thereof as a reducing agent. In addition to hydrazine, hydroquinone and pyrogallol, specifically, hydrazine compounds such as hydrazine chloride, hydrazine sulfate, hydrazine monochloride and hydrazine dichloride; hydroquinone derivatives such as methylhydroquinone; pyrogallol monomethyl ether, pyrogallol-4-carboxylic acid, pyrogallol Examples include pyrogallol derivatives such as 4,6-dicarboxylic acid and gallic acid. The electroless plating solution of the present invention preferably has a reducing agent content of 5 to 50 g / L, and more preferably 10 to 30 g / L. When the content of the reducing agent is less than 5 g / L, the plating reaction hardly occurs. When the content exceeds 50 g / L, the liquid stability is lowered and self-decomposition tends to occur.

  The electroless gold plating solution of the present invention uses one or more selected from glycolic acid, diglycolic acid and salts thereof in addition to the above components. Specific examples include glycolic acid and diglycolic acid, as well as potassium glycolate and sodium glycolate; potassium diglycolate and sodium diglycolate. The content of glycolic acid, diglycolic acid and salts thereof is preferably 1 to 200 g / L, and more preferably 5 to 150 g / L. If the content is less than 1 g / L, the liquid stability tends to decrease, and if it exceeds 200 g / L, an effect commensurate with it cannot be obtained and it is not economical.

  The electroless gold plating solution of the present invention preferably contains the following components in addition to the above essential components.

(1) Thiosulfate Examples of the thiosulfate include ammonium thiosulfate, potassium thiosulfate, sodium thiosulfate, and the like. The content of thiosulfate is preferably 1 to 50 g / L, and more preferably 5 to 30 g / L. When the content of thiosulfate is less than 1 g / L or exceeds 50 g / L, the stability of the plating solution tends to decrease.

(2) Sulfite Examples of the sulfite include ammonium sulfite, potassium sulfite, and sodium sulfite. The content of sulfite is preferably 5 to 150 g / L, and more preferably 30 to 100 g / L. If the sulfite content is less than 5 g / L, the liquid stability tends to decrease, and if it exceeds 150 g / L, the plating reaction rate tends to be slow.

(3) Arsenic compounds, thallium compounds, lead compounds As arsenic compounds, arsenic acid, arsenic acid, etc., as thallium compounds, thallium acetate, thallium nitrate, thallium chloride, etc., as lead compounds, lead acetate, nitric acid Lead, lead chloride and the like can be mentioned. The electroless gold plating solution of the present invention preferably contains at least one of these compounds. By containing these compounds, the appearance of the gold film, the pattern forming property, and the self-decomposition suppressing property are further improved. The content of these compounds is preferably 1.0 to 10.0 mg / L, more preferably 3.0 to 7.0 mg / L. If the content is less than 1.0 mg / L, the plating rate is lowered and the plating solution tends to self-decompose. On the other hand, if it exceeds 10.0 mg / L, an effect commensurate with the added amount cannot be obtained.

(4) Benzotriazole compound When the electroless gold plating of the present invention contains a benzotriazole compound, the base copper does not dissolve in the plating solution because the benzotriazole compound acts as a base metal elution inhibitor. For this reason, the partial abnormal precipitation of plating accompanying the dissolution of copper does not occur, and the film thickness variation is small, and a gold film having good pattern formability can be obtained.

  Examples of the benzotriazole-based compound include benzotriazole sodium, benzotriazole potassium, tetrahydrobenzotriazole, methylbenzotriazole, and nitrobenzotriazole. The content of the benzotriazole-based compound is preferably 1 to 20 g / L, and more preferably 3 to 10 g / L. If the content of the benzotriazole compound is less than 1 g / L, there is no effect in suppressing the dissolution of copper into the plating solution, and partial abnormal precipitation due to the dissolution of copper results in poor pattern formation and liquid stability. Tend to decrease. If it exceeds 20 g / L, the progress of the plating reaction tends to be extremely slow.

(5) pH adjuster The electroless gold plating solution of the present invention can be used at pH 5.0 to 10.0, but is preferably used at pH 6.0 to 8.0. When the pH is lower than 5.0, the plating reaction hardly proceeds, and when the pH is higher than 10.0, the plating solution is easily decomposed. On the other hand, when the pH is higher than 10.0, the gold plating solution easily dissolves the resist. As the pH adjuster, sodium hydroxide, potassium hydroxide, ammonium hydroxide, aqueous sulfite, or the like can be used.

  The electroless gold plating solution of the present invention can be used at a solution temperature of 30 to 90 ° C, but is preferably used at 50 to 80 ° C. When the temperature of the plating solution is lower than 30 ° C., the plating reaction hardly occurs. When the temperature is higher than 90 ° C., the solution stability is lowered and the plating solution tends to be decomposed.

Example 1
A circuit having a line width of 50 to 1000 μm was formed using a resist. A nickel film is formed on a copper substrate microcircuit board with a size of 5 x 5 cm using a commercially available electroless nickel plating solution with a thickness of 3 μm (NEC Chemcat Co., Ltd. Supernic 100), and then a commercially available replacement gold plating. It was immersed in a liquid (N Chemchem ATOMEX) and plated. After 10 minutes, the substrate was taken out, and the deposited film thickness was measured with a fluorescent X-ray film thickness measuring instrument. The thickness of the displacement gold plating was 0.05 μm. Hereinafter, the substrate subjected to the displacement plating is referred to as a sample.
Sodium gold sulfite: 4 g / L (as Au)
Glycolic acid: 52 g / L
Ethylenediamine: 3.0g / L
Sodium thiosulfate: 20 g / L
Sodium sulfite: 50 g / L
Hydrazine sulfate: 25 g / L
Benzotriazole: 4.0 g / L
Thallium sulfate: 5mg / L
The plating solution containing the above components was adjusted to pH 7.0, and the sample was immersed for 1 hour at a solution temperature of 70 ° C. A sample was taken out after 1 hour, and the deposited film thickness was measured with a fluorescent X-ray film thickness measuring instrument. The gold film thickness after 1 hour was 0.50 μm. When confirmed by visual observation and a stereoscopic microscope, discoloration of the resist was not recognized, and gold was deposited on the fine circuit with good pattern formation. The deposited gold film had a lemon-yellow color tone, had no uneven appearance and no gas pits, and had a good appearance. Moreover, decomposition of the plating solution was not observed.

Example 2
Sodium gold sulfite: 4 g / L (as Au)
Glycolic acid: 52 g / L
Ethylenediamine: 3.0g / L
Sodium thiosulfate: 20 g / L
Sodium sulfite: 50 g / L
Hydroquinone: 10g / L
Benzotriazole: 4.0 g / L
Thallium sulfate: 5mg / L
The plating solution containing the above components was adjusted to pH 7.0, and the sample was immersed for 1 hour at a solution temperature of 70 ° C. A sample was taken out after 1 hour, and the deposited film thickness was measured with a fluorescent X-ray film thickness measuring instrument. The gold film thickness after 1 hour was 1.20 μm. When confirmed by visual observation and a stereoscopic microscope, discoloration of the resist was not recognized, and gold was deposited on the fine circuit with good pattern formation. The deposited gold film had a lemon-yellow color tone, had no uneven appearance and no gas pits, and had a good appearance. Moreover, decomposition of the plating solution was not observed.

Example 3
Sodium gold sulfite: 4 g / L (as Au)
Glycolic acid: 52 g / L
Iminodiacetic acid: 23 g / L
Ethylenediamine: 3.0g / L
Sodium thiosulfate: 20 g / L
Sodium sulfite: 50 g / L
Hydroquinone: 10g / L
Benzotriazole: 4.0 g / L
Thallium sulfate: 5mg / L
The plating solution containing the above components was adjusted to pH 7.0, and the sample was immersed for 1 hour at a solution temperature of 70 ° C. A sample was taken out after 1 hour, and the deposited film thickness was measured with a fluorescent X-ray film thickness measuring instrument. The gold film thickness after 1 hour was 0.80 μm. When confirmed by visual observation and a stereoscopic microscope, discoloration of the resist was not recognized, and gold was deposited on the fine circuit with good pattern formation. The deposited gold film had a lemon-yellow color tone, had no uneven appearance and no gas pits, and had a good appearance. Moreover, decomposition of the plating solution was not observed.

Example 4
Sodium gold sulfite: 4 g / L (as Au)
Glycolic acid: 52 g / L
Nitrilotriacetic acid: 33 g / L
Ethylenediamine: 3.0g / L
Sodium thiosulfate: 20 g / L
Sodium sulfite: 50 g / L
Hydroquinone: 10g / L
Benzotriazole: 4.0 g / L
Thallium sulfate: 5mg / L
The plating solution containing the above components was adjusted to pH 7.0, and the sample was immersed for 1 hour at a solution temperature of 70 ° C. A sample was taken out after 1 hour, and the deposited film thickness was measured with a fluorescent X-ray film thickness measuring instrument. The gold film thickness after 1 hour was 0.73 μm. When confirmed by visual observation and a stereoscopic microscope, discoloration of the resist was not recognized, and gold was deposited on the fine circuit with good pattern formation. The deposited gold film had a lemon-yellow color tone, had no uneven appearance and no gas pits, and had a good appearance. Moreover, decomposition of the plating solution was not observed.

Example 5
Sodium gold sulfite: 4 g / L (as Au)
Glycolic acid: 52 g / L
Methylglycine diacetate: 30g / L
Ethylenediamine: 3.0g / L
Sodium thiosulfate: 20 g / L
Sodium sulfite: 50 g / L
Hydroquinone: 10g / L
Benzotriazole: 4.0 g / L
Thallium sulfate: 5mg / L
The plating solution containing the above components was adjusted to pH 7.0, and the sample was immersed for 1 hour at a solution temperature of 70 ° C. A sample was taken out after 1 hour, and the deposited film thickness was measured with a fluorescent X-ray film thickness measuring instrument. The gold film thickness after 1 hour was 1.15 μm. When confirmed by visual observation and a stereoscopic microscope, discoloration of the resist was not recognized, and gold was deposited on the fine circuit with good pattern formation. The deposited gold film had a lemon-yellow color tone, had no uneven appearance and no gas pits, and had a good appearance. Moreover, decomposition of the plating solution was not observed.

Example 6
Sodium gold sulfite: 4 g / L (as Au)
Glycolic acid: 52 g / L
Ethylenediamine: 3.0g / L
Sodium thiosulfate: 20 g / L
Sodium sulfite: 50 g / L
Pyrogallol: 12g / L
Benzotriazole: 4.0 g / L
Thallium sulfate: 5mg / L
The plating solution containing the above components was adjusted to pH 7.0, and the sample was immersed for 1 hour at a solution temperature of 70 ° C. A sample was taken out after 1 hour, and the deposited film thickness was measured with a fluorescent X-ray film thickness measuring instrument. The gold film thickness after 1 hour was 1.49 μm. When confirmed by visual observation and a stereoscopic microscope, discoloration of the resist was not recognized, and gold was deposited on the fine circuit with good pattern formation. The deposited gold film had a lemon-yellow color tone, had no uneven appearance and no gas pits, and had a good appearance. Moreover, decomposition of the plating solution was not observed.

Example 7
Sodium gold sulfite: 4 g / L (as Au)
Diglycolic acid: 46g / L
Ethylenediamine: 3.0g / L
Sodium thiosulfate: 20 g / L
Sodium sulfite: 50 g / L
Pyrogallol: 10g / L
Benzotriazole: 4.0 g / L
Thallium sulfate: 5mg / L
The plating solution containing the above components was adjusted to pH 7.0, and the sample was immersed for 1 hour at a solution temperature of 70 ° C. A sample was taken out after 1 hour, and the deposited film thickness was measured with a fluorescent X-ray film thickness measuring instrument. The gold film thickness after 1 hour was 1.21 μm. When confirmed by visual observation and a stereoscopic microscope, discoloration of the resist was not recognized, and gold was deposited on the fine circuit with good pattern formation. The deposited gold film had a lemon-yellow color tone, had no uneven appearance and no gas pits, and had a good appearance. Moreover, decomposition of the plating solution was not observed.

Comparative Example 1
Sodium gold sulfite: 4 g / L (as Au)
Ethylenediamine: 3.0g / L
Sodium thiosulfate: 20 g / L
Sodium sulfite: 50 g / L
Hydrazine sulfate: 25 g / L
Benzotriazole: 4.0 g / L
Thallium sulfate: 5mg / L
The plating solution containing the above components was adjusted to pH 7.0, and the sample was immersed for 1 hour at a solution temperature of 70 ° C. Since the plating solution was decomposed during immersion of the sample and the immersion was interrupted, the deposited film thickness could not be measured. As a result of visual observation and confirmation with a stereomicroscope, no discoloration of the resist was observed, but the pattern formation was poor and gold was deposited not only on the fine circuit. The deposited gold film had a red-yellow appearance.

Comparative Example 2
Sodium gold sulfite: 4 g / L (as Au)
Ethylenediaminetetraacetic acid: 100g / L
Ethylenediamine: 3.0g / L
Sodium thiosulfate: 20 g / L
Sodium sulfite: 50 g / L
Hydrazine sulfate: 25 g / L
Benzotriazole: 4.0 g / L
Thallium sulfate: 5mg / L
The plating solution containing the above components was adjusted to pH 7.0, and the sample was immersed for 1 hour at a solution temperature of 70 ° C. A sample was taken out after 1 hour, and the deposited film thickness was measured with a fluorescent X-ray film thickness measuring instrument. The gold film thickness after 1 hour was 0.28 μm. When confirmed by visual observation and a stereoscopic microscope, discoloration of the resist was not recognized, and gold was deposited on the fine circuit with good pattern formation. The deposited gold film had a lemon-yellow color tone, had no uneven appearance and no gas pits, and had a good appearance. Moreover, decomposition of the plating solution was not observed.

Comparative Example 3
Sodium gold sulfite: 4 g / L (as Au)
Ethylenediamine: 3.0g / L
Sodium thiosulfate: 20 g / L
Sodium sulfite: 50 g / L
Hydroquinone: 10g / L
Benzotriazole: 4.0 g / L
Thallium sulfate: 5mg / L
The plating solution containing the above components was adjusted to pH 7.0, and the sample was immersed for 1 hour at a solution temperature of 70 ° C. Since the plating solution was decomposed during immersion of the sample and the immersion was interrupted, the deposited film thickness could not be measured. As a result of visual observation and confirmation with a stereomicroscope, no discoloration of the resist was observed, but the pattern formation was poor and gold was deposited not only on the fine circuit. The deposited gold film had a red-yellow appearance.

Comparative Example 4
Sodium gold sulfite: 4 g / L (as Au)
Ethylenediaminetetraacetic acid: 100g / L
Ethylenediamine: 3.0g / L
Sodium thiosulfate: 20 g / L
Sodium sulfite: 50 g / L
Hydroquinone: 10g / L
Benzotriazole: 4.0 g / L
Thallium sulfate: 5mg / L
The plating solution containing the above components was adjusted to pH 7.0, and the sample was immersed for 1 hour at a solution temperature of 70 ° C. A sample was taken out after 1 hour, and the deposited film thickness was measured with a fluorescent X-ray film thickness measuring instrument. The gold film thickness after 1 hour was 0.59 μm. When confirmed by visual observation and a stereoscopic microscope, discoloration of the resist was not recognized, and gold was deposited on the fine circuit with good pattern formation. The deposited gold film had a lemon-yellow color tone, had no uneven appearance and no gas pits, and had a good appearance. Moreover, decomposition of the plating solution was not observed.

Comparative Example 5
Sodium gold sulfite: 4 g / L (as Au)
Ethylenediamine: 3.0g / L
Sodium thiosulfate: 20 g / L
Sodium sulfite: 50 g / L
Pyrogallol: 12g / L
Benzotriazole: 4.0 g / L
Thallium sulfate: 5mg / L
The plating solution containing the above components was adjusted to pH 7.0, and the sample was immersed for 1 hour at a solution temperature of 70 ° C. Since the plating solution was decomposed during immersion of the sample and the immersion was interrupted, the deposited film thickness could not be measured. As a result of visual observation and confirmation with a stereomicroscope, no discoloration of the resist was observed, but the pattern formation was poor and gold was deposited not only on the fine circuit. The deposited gold film had a red-yellow appearance.

Comparative Example 6
Sodium gold sulfite: 4 g / L (as Au)
Ethylenediaminetetraacetic acid: 100g / L
Ethylenediamine: 3.0g / L
Sodium thiosulfate: 20 g / L
Sodium sulfite: 50 g / L
Pyrogallol: 12g / L
Benzotriazole: 4.0 g / L
Thallium sulfate: 5mg / L
The plating solution containing the above components was adjusted to pH 7.0, and the sample was immersed for 1 hour at a solution temperature of 70 ° C. A sample was taken out after 1 hour, and the deposited film thickness was measured with a fluorescent X-ray film thickness measuring instrument. The gold film thickness after 1 hour was 0.88 μm. When confirmed by visual observation and a stereoscopic microscope, discoloration of the resist was not recognized, and gold was deposited on the fine circuit with good pattern formation. The deposited gold film had a lemon-yellow color tone, had no uneven appearance and no gas pits, and had a good appearance. Moreover, decomposition of the plating solution was not observed.

Claims (5)

An electroless gold plating solution containing gold sulfite, a complexing agent and a reducing agent, wherein the electroless gold plating solution contains at least one selected from glycolic acid, diglycolic acid and salts thereof. The electroless gold plating solution according to claim 1, wherein the complexing agent is a water-soluble aminocarboxylic acid or water-soluble amine excluding ethylenediaminetetraacetic acid (EDTA). The electroless gold plating solution according to claim 1 or 2, wherein at least one of a hydrazine compound, hydroquinone and a derivative thereof, pyrogallol and a derivative thereof is used as the reducing agent. The electroless gold plating solution according to any one of claims 1 to 3, comprising at least one of an arsenic compound, a thallium compound, and a lead compound. The electroless gold plating solution according to any one of claims 1 to 4, comprising a benzotriazole-based compound as a base metal elution inhibitor.