JP4320606B2 - Gold plating bath - Google Patents

Description

  The present invention relates to a non-cyanide gold plating bath (electrogold plating bath, electroless gold plating bath) containing sulfurous acid or a salt thereof. More specifically, the air decomposition of sulfite ions is suppressed, and the stability is excellent. It relates to a non-cyanide gold plating bath.

  In the field of electrical components, a gold plating film is formed as a surface treatment on electrical contacts and joint surfaces by utilizing the property that gold does not oxidize. In recent years, the toxicity of cyan has been regarded as a problem, and a non-cyanide type gold plating bath has been developed. As this non-cyanide gold plating bath, a gold plating bath using gold thiosulfate, gold sulfite, and chloroaurate as a gold source has been proposed (Patent Documents 1 to 3: JP 2003-129270 A). No. 2,866,676 and No. 3,148,427).

  In these non-cyanide gold plating baths, sulfite ions are supplied for the purpose of complexing agents and stabilizers. However, conventional gold plating baths containing sulfite or salts thereof have problems in plating bath stability. there were.

  That is, the above-mentioned publication describes that an aromatic compound is contained as a stabilizer. For example, JP-A 2003-129270 discloses hydroquinone and naphthalene compounds for the purpose of suppressing consumption of additives. In Japanese Patent No. 2866676, a hydroquinone is added to a gold sulfite plating bath using thiourea as a reducing agent to reduce and regenerate the oxide of thiourea used as the reducing agent for a long-term bath. Stabilization is disclosed. Japanese Patent No. 3148427 discloses that bath stability can be improved by adding mercaptobenzothiazole or the like to a gold sulfite plating bath using ascorbic acid as a reducing agent.

  However, these aromatic compounds cannot sufficiently suppress the air decomposition of sulfite ions or sulfite complex ions supplied into the plating bath.

JP 2003-129270 A Japanese Patent No. 2866676 Japanese Patent No. 3148427

  An object of the present invention is to overcome the above-mentioned problems of conventional baths, and to provide a gold plating bath having improved bath stability by suppressing air decomposition of sulfite ions.

  In order to achieve the above object, the present inventor has studied the cause of destabilizing a gold plating bath using sulfite, and as a result, sulfite, which is a complexing agent of gold, is oxidized by air so that the gold sulfite compound is obtained. It turned out to be caused by decomposition. As a result of considering and examining that the stability of the bath can be improved by preventing the air oxidation of this sulfite, it was found that the addition of the quinoline compound can prevent the air oxidation of the sulfite and consequently the bath becomes stable. did.

  In particular, in an electroless gold plating bath containing gold sulfite, sulfurous acid or a salt thereof, thiosulfuric acid or a salt thereof, and ascorbic acid or a salt thereof, both a gold sulfite complex ion and a gold thiosulfate complex ion are generated in the plating bath. The balance of the gold complex ions is determined by the concentration ratio of sulfurous acid or its salt to thiosulfuric acid or its salt. When ascorbic acid or a salt thereof is used as the reducing agent, it is important to maintain the balance of the gold complex ions in the plating bath because the reducing ability is weak. If the balance of the gold complex ions in the plating bath is lost, the appearance of the gold plating film may be deteriorated or the film may not be formed. Therefore, it is highly important to suppress the air decomposition of sulfite ions supplied to the plating bath, but as described above, the addition of a quinoline compound such as quinoline sulfonic acid or a salt thereof can solve such a problem. I found it.

  In the above non-cyanide gold plating bath, a mercapto compound is used as a stabilizer or a reducing agent. For example, Japanese Patent No. 2866676 discloses a gold sulfite plating bath using thiourea as a reducing agent, and Japanese Patent No. 3148427 includes a mercaptobenzothiazole in a gold sulfite plating bath using ascorbic acid as a reducing agent. It is disclosed that the bath stability can be improved by adding, for example. However, compounds having SH groups (thiourea, mercaptobenzothiazole, etc.) have strong properties of adsorbing to the gold film surface because of their strong bonding strength with gold. As a result, it has been found that a gold-plated film having good wire bonding properties can be obtained without adding such a compound having an SH group, although it affects the properties of the deposited film and adversely affects the wire bonding properties.

（Ｒ¹〜Ｒ⁷はそれぞれＨ，ＯＨ，ＣＯＯＨ，ＳＯ₃Ｈ，ＣＨ₃基のいずれかであるが、Ｒ¹〜Ｒ⁷の全てが同時にＨとはならない。）
請求項２：
亜硫酸又はその塩を含有する非シアン化金めっき浴であって、前記非シアン化金めっき浴が、亜硫酸金塩、亜硫酸又はその塩、チオ硫酸又はその塩、上記式で表されるキノリン化合物、アスコルビン酸又はその塩、及びアミノチアゾール誘導体を含有する無電解金めっき浴であることを特徴とする金めっき浴。
請求項３：
前記キノリン化合物がキノリンスルホン酸又はその塩である請求項１又は２記載の金めっき浴。
請求項４：
メルカプト基含有化合物を含有しない請求項１乃至３のいずれか１項記載の金めっき浴。 Accordingly, the present invention provides the following gold plating bath.
Claim 1:
A non-cyanide gold plating bath containing sulfurous acid or a salt thereof, wherein the non -cyanide gold plating bath contains gold sulfite, sulfurous acid or a salt thereof, and a quinoline compound represented by the following formula: A gold plating bath characterized by being an electrogold plating bath containing no sulfuric acid or a salt thereof .

(R ^{1 to} R ⁷ are each an H, OH, COOH, SO ₃ H, or CH ₃ group, but all of R ^{1 to} R ⁷ do not become H at the same time.)
Claim 2:
A non-cyanide gold plating bath containing sulfurous acid or a salt thereof, wherein the non-cyanide gold plating bath comprises gold sulfite, sulfurous acid or a salt thereof, thiosulfuric acid or a salt thereof, a quinoline compound represented by the above formula, A gold plating bath, which is an electroless gold plating bath containing ascorbic acid or a salt thereof and an aminothiazole derivative .
Claim 3:
The gold plating bath according to claim 1 or 2, wherein the quinoline compound is quinoline sulfonic acid or a salt thereof.
Claim 4 :
The gold plating bath according to any one of claims 1 to 3, which does not contain a mercapto group-containing compound.

  The gold plating bath of the present invention has improved bath stability without affecting the properties of the deposited gold film. In this case, a gold plating film having excellent wire bonding characteristics can be obtained by not adding a mercapto group-containing compound.

The non-cyanide gold plating bath of the present invention contains sulfurous acid or a salt thereof.
In this case, as sulfurous acid or a salt thereof, it is supplied for the purpose of a gold source, a complexing agent, a stabilizer, etc. in the plating bath, sulfurous acid, sodium sulfite, potassium sulfite, sodium gold sulfite, gold potassium sulfite, Examples include gold ammonium sulfite.

  If the plating bath is a non-cyanide gold plating bath (a gold plating bath that does not contain free cyanide or a cyanide compound in the plating bath), it is an electroless plating bath that contains a reducing agent even if it is an electroplating bath. Also good.

For electroless gold plating bath, gold sulfite, sulfurous acid or salts thereof, Ru electroless gold Mekkidea containing thiosulfate or a salt thereof and ascorbic acid or a salt thereof,.

  Examples of the gold sulfite include sodium gold sulfite, potassium gold sulfite, and gold ammonium sulfite. A solution prepared by adding gold chloride to a sulfite solution may be used. The concentration in the plating bath is preferably 0.5 to 20 g / L, particularly 0.5 to 4 g / L as gold. If it is less than 0.5 g / L, the dissolution amount of the underlying nickel may increase and the solder joint characteristics may deteriorate. When the gold concentration is high, there is no problem in terms of characteristics, but there is a problem that the cost increases.

  Sulfurous acid or a salt thereof, thiosulfuric acid or a salt thereof mainly serves as a complexing agent, and ascorbic acid or a salt thereof acts as a reducing agent. Examples of the sulfurous acid or a salt thereof include sulfurous acid, sodium sulfite, potassium sulfite, ammonium sulfite, sodium bisulfite, potassium bisulfite, sodium disulfite, potassium disulfite and the like. The concentration in the plating bath is 1 to 40 g / L. If it is lower than 1 g / L, the bath stability may be inferior. If it is higher than 40 g / L, the deposition rate may decrease. Examples of thiosulfuric acid or a salt thereof include thiosulfuric acid, sodium salt of thiosulfuric acid, potassium salt, ammonium salt, and the like, and the concentration in the plating bath can be 1 to 20 g / L. If it is lower than 1 g / L, the bath stability may deteriorate.

  Examples of ascorbic acid or a salt thereof include ascorbic acid, L-ascorbic acid, a sodium salt, a potassium salt, and an ammonium salt thereof, and the concentration in the plating bath can be 1 to 20 g / L. If it is lower than 1 g / L, the deposition rate may be slow, and if it is higher than 20 g / L, the bath stability may be inferior.

  The pH is preferably 6 to 8, particularly 6.5 to 7.5. Moreover, it is preferable to set it as 45-60 degreeC as temperature of a plating bath.

  On the other hand, as the electrogold plating bath, an electrogold plating bath which contains gold sulfite as a water-soluble gold salt, sulfurous acid or a salt thereof as a complexing agent and does not contain thiosulfuric acid or a salt thereof is preferable.

  Examples of the gold sulfite include sodium gold sulfite, potassium gold sulfite, and gold ammonium sulfite. A solution prepared by adding gold chloride to a sulfite solution may be used. The concentration in the plating bath is preferably 0.5 to 20 g / L as gold. If it is less than 0.5 g / L, the dissolution amount of the underlying nickel may increase and the solder joint characteristics may deteriorate. When the gold concentration is high, there is no problem in terms of characteristics, but there is a problem that costs increase.

  Examples of sulfites include those described above. The concentration in the plating bath is preferably 30 to 180 g / L. Further, it does not contain thiosulfuric acid or a salt thereof usually used as a complexing agent in an electroless plating bath. If thiosulfuric acid or a salt thereof is contained, the film properties may be deteriorated.

In the case of an electroplating bath, the pH of the plating bath is preferably 6.5 to 11, the temperature is 25 to 65 ° C., and the cathode current density is preferably 0.05 to 1.5 A / dm ² .

  A quinoline compound is added to the plating bath of the present invention. In this case, examples of the quinoline compound include those represented by the following structural formula.

（Ｒ¹〜Ｒ⁷はそれぞれＨ，ＯＨ，ＣＯＯＨ，ＳＯ₃Ｈ，ＣＨ₃基のいずれかであるが、Ｒ¹〜Ｒ⁷の全てが同時にＨとはならない。）

(R ^{1 to} R ⁷ are each an H, OH, COOH, SO ₃ H, or CH ₃ group, but all of R ^{1 to} R ⁷ do not become H at the same time.)

  Specific examples include 8-hydroxyquinoline, 8-hydroxyquinoline sulfate, 2-hydroxyquinoline, 8-hydroxyquinolazine, 8-hydroxyquinoline-5-sulfonic acid, 4-hydroquinoline-2-carboxylic acid, and the like. In particular, quinoline sulfonic acid or a salt thereof is preferable. In this case, examples of the salt of quinoline sulfonic acid include sodium salt and potassium salt.

  The concentration of the quinoline compound in the plating bath is preferably 0.05 to 10 g / L, particularly preferably 0.5 to 5 g / L. If it is lower than 0.05 g / L, the bath stability may be inferior. If it is higher than 10 g / L, it may not be dissolved. This quinoline compound can suppress air decomposition of the sulfite ion or its complex ion supplied into the plating bath, whether it is an electrogold plating bath or an electroless gold plating bath, and the stability of the plating bath is enhanced. The effect is particularly remarkable in the case of a non-cyanide electroless gold plating bath using ascorbic acid or a salt thereof as a reducing agent.

  Moreover, it is preferable that the electrogold plating bath or electroless gold plating bath of the present invention does not contain a mercapto group-containing compound in order to improve wire bonding properties. Examples of the mercapto group-containing compound include thiourea or a derivative thereof, mercaptosuccinic acid or a salt thereof, 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, thioacetic acid or a salt thereof, and the like. Absent.

  An aminothiazole derivative can be further blended in the gold plating bath of the present invention. In particular, in an electroless gold plating bath using ascorbic acid as a reducing agent, the use of the quinoline compound and aminothiazole in combination improves the appearance of the film for unknown reasons.

  As aminothiazole, 2-amino-3,5-dimethylthiazole which is an aminothiazole derivative, 2-amino-4-thiazoleacetic acid, 5-amino-3-methylisothiazole, 2-amino-4-methylthiazole, etc. 2-amino-6,5-dimethylbenzothiazole, 2-amino-6-ethoxybenzothiazole, 2-aminobenzothiazole, 2-amino-4-methoxybenzothiazole, 2-amino-4- which are benzoaminothiazole derivatives And methylbenzothiazole.

  The concentration in the plating bath is preferably 1 to 1,000 mg / L. If the upper limit is exceeded, gold deposition may be hindered. Below the lower limit, the effect of preventing precipitation on the resin may not be achieved. This aminothiazole can prevent gold deposition on the resin in both an electrogold plating bath and an electroless gold plating bath. In particular, in the case of a non-cyanide electroless gold plating bath using ascorbic acid or a salt thereof as a reducing agent, the effect is remarkable without inhibiting the gold precipitation reaction.

  In addition, the plating bath of the present invention may contain a known pH adjuster, pH buffer, and various additives. For example, as a pH adjuster, sulfuric acid, carboxylic acid, phosphoric acid, sodium hydroxide, ammonia and the like, as a pH buffer agent, boric acid, tetraboric acid and the like, crystal adjusters such as lead compounds and thallium, benzotriazole, An azole such as methylbenzotriazole, a metal ion concealing agent such as phenanthroline, bipyridyl, and salicylate, an aminocarboxylic acid such as EDTA, an ammonium salt, and an auxiliary complexing agent such as chloride may be added.

  The plating bath of the present invention is suitably used for circuit formation of electronic parts such as printed boards, wafers, and IC packages. More specifically, it is suitable for use in forming a thick gold plating film on the gold plating film after the cleaner or forming a thick gold plating film after performing substitution gold plating on the electroless nickel plating film. It is done.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[ Reference Examples 1 to 4, Comparative Example 1]
The electroless gold plating bath shown in Table 1 was prepared and left at 90 ° C., and the time until decomposition was measured. The results are shown in Table 1.

注：ｐＨは硫酸又は水酸化ナトリウムを用いて調整した。

Note: pH was adjusted using sulfuric acid or sodium hydroxide.

[Examples 1 to 4 , Comparative Example 2]
The electrogold plating bath shown in Table 2 was prepared, and the rate of reduction of sulfite was measured after leaving this at 50 ° C. with 5 mL / L of air per minute for 36 hours. The results are shown in Table 2.

注：ｐＨは硫酸又は水酸化ナトリウムを用いて調整した。

Note: pH was adjusted using sulfuric acid or sodium hydroxide.

[Examples 5 to 9, Reference Example 5, Comparative Examples 3 to 6]
Electroless gold plating baths shown in Tables 3, 4 and 5 were created, and electroless plating was performed on the printed circuit board (epoxy resin substrate) in which the circuit portion was plated with electroless nickel plating film by the following method. The presence or absence of gold deposition on the resin other than the circuit, bath stability, coating appearance, and wire bonding properties were evaluated. The results are shown in Tables 3, 4 and 5.
Electroless gold plating method Immersion at 55 ° C for 30 minutes
Presence / absence of gold deposition on resin Visual confirmation with a microscope (× 80)
Bath stability Plating bath at 55 ° C., “excellent” if it did not decompose for 48 hours, “good” if it did not decompose for 24 hours, “impossible” if decomposed for 3 hours. "
With observation of the film appearance microscope (× 50), pits and color tone were visually observed and evaluated comprehensively.
Using wire bonding KS4524A (manufactured by K & S), wire bonding strength was evaluated with a gold wire with a diameter of 25 μm. The strength was less than 6 g / L, “impossible”, 6 g / L or more was “good”, especially 9 g / L or more. Was “excellent”.

注：ｐＨは硫酸又は水酸化ナトリウムを用いて調整した。

Note: pH was adjusted using sulfuric acid or sodium hydroxide.

注：ｐＨは硫酸又は水酸化ナトリウムを用いて調整した。

Note: pH was adjusted using sulfuric acid or sodium hydroxide.

注：ｐＨは硫酸又は水酸化ナトリウムを用いて調整した。

Note: pH was adjusted using sulfuric acid or sodium hydroxide.

[ Reference Examples 6 to 10 ]
An electroless gold plating bath having the composition shown in Table 6 was constructed. Using this electroless gold plating bath, gold plating was performed in the same manner as described above. About the obtained gold plating film | membrane, wire-bonding property was evaluated by the said method. The results are shown in Table 6.

注：ｐＨは硫酸又は水酸化ナトリウムを用いて調整した。

Note: pH was adjusted using sulfuric acid or sodium hydroxide.

注：ｐＨは硫酸又は水酸化ナトリウムを用いて調整した。
[ Example 10, Comparative Example 7]
An electric gold plating bath having a composition shown in Table 7 was constructed, and a gold plating film was formed on a printed circuit board (epoxy resin substrate) having a gold plating on the circuit portion by the following method, and the wire bonding property was similarly evaluated. . The results are shown in Table 7.
Electroplating method Plating bath temperature 50 ℃
Cathode current density 0.2 A / dm ²
Energizing time 10 minutes

Note: pH was adjusted using sulfuric acid or sodium hydroxide.

Claims (4)

A non-cyanide gold plating bath containing sulfurous acid or a salt thereof, wherein the non -cyanide gold plating bath contains gold sulfite, sulfurous acid or a salt thereof, and a quinoline compound represented by the following formula: A gold plating bath characterized by being an electrogold plating bath containing no sulfuric acid or a salt thereof .

(R ^{1 to} R ⁷ are each an H, OH, COOH, SO ₃ H, or CH ₃ group, but all of R ^{1 to} R ⁷ do not become H at the same time.) A non-cyanide gold plating bath containing sulfurous acid or a salt thereof, wherein the non-cyanide gold plating bath is a gold sulfite, sulfurous acid or a salt thereof, thiosulfuric acid or a salt thereof, a quinoline compound represented by the following formula, A gold plating bath, which is an electroless gold plating bath containing ascorbic acid or a salt thereof and an aminothiazole derivative .

(R ^{1 to} R ⁷ are each an H, OH, COOH, SO ₃ H, or CH ₃ group, but all of R ^{1 to} R ⁷ do not become H at the same time.)   The gold plating bath according to claim 1 or 2, wherein the quinoline compound is quinoline sulfonic acid or a salt thereof. The gold plating bath according to any one of claims 1 to 3, which does not contain a mercapto group-containing compound.