TWI431155B - Maintain the management of electroless gold plating bath plating capacity of the method - Google Patents

Description

Method for maintaining the electroplating ability of an electroless gold plating bath

The present invention relates to a method of maintaining the electroplating ability of an electroless gold plating bath.

Gold has the least tendency to ionize in metals, that is, the most stable and less rustable metal. Moreover, since it is excellent in electrical conductivity, it is widely used in the field of the electronics industry. Instead of gold plating, the final surface treatment of a printed circuit board or a mounted portion or a terminal portion of an IC package is widely used. Specifically, there are the following methods, each having the following features.

(1) ENIG (Electroless Nickel Immersion Gold: Electroless Nickel / Substitute Gold) . A method of replacing the gold plating film is formed on the underlying electroless nickel plating film. . Prevents copper from diffusing, prevents nickel oxidation, and improves circuit or terminal/corrosion resistance. . Can be used for solder bonding.

. After ENIG treatment, thick gold is applied and can also be used for wire bonding.

. At the time of wire bonding, heat treatment was performed after the plating treatment, but nickel was diffused on the gold film. In order to prevent this, an electroless gold plating bath is applied to the nickel/substituted gold film to increase the thickness of the gold film in response to the diffusion of nickel.

(2) DIG (Direct Immersion Gold: Direct Replacement Gold) . On copper, a method of replacing the gold plating film is directly formed.

. Prevents copper oxidation, prevents copper from spreading, and improves the corrosion resistance of circuits or terminals.

. It can also be used for solder bonding and wire bonding.

. When compared with nickel/gold or nickel/palladium/gold, the long-term reliability is slightly inferior, but it is sufficient for use without excessive heat load conditions (low heat treatment temperature, low number of reflows, etc.).

. Because the steps are simple, the cost is low.

(3) ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold: Electroless Nickel/Electroless Palladium/Replacement Gold) . A method of providing an electroless palladium coating between the underlying electroless nickel plating film and the replacement gold plating film.

. Prevents copper from diffusing, prevents oxidation of nickel and prevents diffusion, and improves the corrosion resistance of circuits or terminals.

. It is most suitable for lead-free solder bonding in recent years. (Lead-free solder is less thermally bonded than tin-lead eutectic solder, and the bonding characteristics are reduced when nickel/gold is used).

. Suitable for wire bonding.

. Nickel diffusion does not occur even if the thickness of the gold film is not increased.

. Even if it is compatible with nickel/gold, it is suitable for the purpose of improving reliability.

In place of the gold plating, the difference between the underlying layer of nickel or the like and the oxidation-reduction potential in the plating bath is used to precipitate gold, which erodes nickel and causes corrosion points due to oxidation (dissolution). This corrosion point due to oxidation is a hindrance factor when the solder of the solder layer is connected to nickel, and there is a problem that the bonding characteristics such as strength are lowered.

In order to solve this problem, an electroless gold plating bath containing an aldehyde sulfite adduct is disclosed in JP-A-2004-137589 (Patent Document 1), and a gold-plated bath system containing a hydrocarbyl alkylsulfonic acid is disclosed in International Publication No. Handbook No. 2004/111287 (Patent Document 2). These techniques are aimed at inhibiting corrosion of the underlying metal.

However, in the case of the tri-ethyltetramine described in the handbook of International Publication No. 2004/111287 (Patent Document 2), when the amine compound of the amine group (-NH ₂ ) is present, the grain boundary of the nickel surface is eroded. The coating power of gold is lowered, and the appearance of the appearance of the film becomes red.

[Patent Document 1] JP-A-2004-137589 [Patent Document 2] International Publication No. 2004/111287 [Patent Document 3] JP-A-2002-226975 [Patent Document 4] Patent No. 2538461

Invention disclosure

In view of the above, the present invention provides an electroless gold plating bath which does not cause appearance defects due to grain boundary erosion of the nickel surface, and which maintains the electroless gold plating bath of a gold plating film which can obtain a good film appearance for a long period of time. In addition, the method of maintaining an electroless gold plating bath in which cyanide gold salt is consumed by electroplating treatment is stably maintained for a long period of time.

The present inventors have found that a formaldehyde bisulfite adduct containing a gold cyanide salt as a gold component, a reducing agent component, and the following general formula (1) or (2) R ₁ -NH-C ₂ H _{4 are used.} -NH-R ₂ (1) R ₃ -(CH ₂ -NH-C ₂ H ₄ -NH-CH ₂ ) _n -R ₄ (2) (in the formulae (1) and (2), R ₁ , R ₂ And R ₃ and R ₄ represent -OH, -CH ₃ , -CH ₂ OH, -C ₂ H ₄ OH, -CH ₂ N(CH ₃ ) ₂ , -CH ₂ NH(CH ₂ OH), -CH ₂ NH(C ₂ H ₄ OH), -C ₂ H ₄ NH(CH ₂ OH), -C ₂ H ₄ NH(C ₂ H ₄ OH), -CH ₂ N(CH ₂ OH) ₂ , -CH ₂ N (C ₂ H ₄ OH) ₂ , -C ₂ H ₄ N(CH ₂ OH) ₂ or -C ₂ H ₄ N(C ₂ H ₄ OH) ₂ , which may be the same or different, n is 1 to 4 An electroless gold plating bath of an amine compound represented by an integer) is less likely to cause grain boundary corrosion such as the above nickel surface, but it is known that such an electroplating bath system has a formaldehyde bisulfite addition of an amine and a reducing agent component regardless of the presence or absence of electroplating operation. The amine compound represented by the above formula (1) or (2) gradually disappears from the plating bath, and there is a problem that the electrolytic bath is decomposed. Therefore, it has been found that the above problems can be solved by replenishing these disappearing components in small amounts at appropriate correct concentration ratios.

That is, the present invention provides the following method for maintaining the electroplating ability of an electroless gold plating bath.

[1] in order to maintain a gold cyanide salt, a complexing agent, a formaldehyde bisulfite adduct, and the following general formula (1) or (2) R ₁ -NH-C ₂ H ₄ -NH-R ₂ (1) R ₃ -(CH ₂ -NH-C ₂ H ₄ -NH-CH ₂ ) _n -R ₄ (2) (in the formulae (1) and (2), R ₁ , R ₂ , R ₃ and R ₄ represents -OH, -CH ₃ , -CH ₂ OH, -C ₂ H ₄ OH, -CH ₂ N(CH ₃ ) ₂ , -CH ₂ NH(CH ₂ OH) , -CH ₂ NH(C ₂ H ₄ OH), -C ₂ H ₄ NH(CH ₂ OH), -C ₂ H ₄ NH(C ₂ H ₄ OH), -CH ₂ N(CH ₂ OH) ₂ , -CH ₂ N (C ₂ H ₄ OH) ₂ , -C ₂ H ₄ N(CH ₂ OH) ₂ or -C ₂ H ₄ N(C ₂ H ₄ OH) ₂ , which may be the same or different, n is an integer from 1 to 4) The electroless gold plating bath of the amine compound is maintained at a temperature of 70 to 90 ° C, and the method of managing the electroplating ability of the electroless gold plating bath is stably maintained, and the cyanide base as the first replenishing component and the above-mentioned formaldehyde bisulfite are periodically replenished. The composition and amine compound are methods for electroplating ability of an electroless gold plating bath.

[2] The replenishment ratio of the above cyanide base, formaldehyde bisulfite adduct and amine compound is replenished to cyanide base: formaldehyde bisulfite adduct: amine compound = 0.5~5:1:0.1~5 (Morby) is a method of maintaining the electroplating ability of an electroless gold plating bath as described in [1].

[3] The above-mentioned first replenishing component is characterized by adding 0.1 to 5 mol% of the concentration at the time of bathing, based on the formaldehyde bisulfite adduct, and replenishing the first replenishing component 1 to 20 times per hour [2] A method of maintaining the plating ability of an electroless gold plating bath is described.

[4] Further, the electroplating bath in which gold is consumed by the electroplating treatment is supplemented with the above-mentioned cyanide gold salt, formaldehyde bisulfite adduct and amine compound as the second replenishing component [1] to [3]. The method of maintaining the electroplating ability of the electroless gold plating bath is described.

[5] The replenishment ratio of the above-mentioned cyanide gold salt, formaldehyde bisulfite adduct and amine compound is replenished into a gold cyanide salt: formaldehyde bisulfite adduct: amine compound = 1: 0.1 to 5: 0.5 ~5 (Morby ratio) is a method described in [4] for maintaining the plating ability of an electroless gold plating bath.

[6] Based on the formaldehyde bisulfite adduct, the concentration of the bath is 0.1 to 5 mol%, and the second replenishment component is characterized by 1 to 20 times per hour. A method of maintaining the electroplating ability of an electroless gold plating bath.

[7] The primary reductive amount of the formaldehyde hydrogen sulfite adduct is characterized by maintaining the electroplating ability of the electroless gold plating bath described in [3] or [6] per 1 L of the electroplating bath. method.

[8] Substituting the above-mentioned formaldehyde hydrogen sulfite adduct, one or more of [1] to [7] characterized by replenishing part or all of the above-mentioned supplemental formaldehyde bisulfite adduct with a molar amount of formaldehyde A method for maintaining the electroplating ability of an electroless gold plating bath as described in the section.

According to the present invention, the appearance of the grain boundary of the nickel surface is not deteriorated, and the electroplating ability of the electroless gold plating bath for managing the gold plating film which forms a good film appearance can be stably maintained for a long period of time, and the plating ability can be stably maintained for a long period of time. An electroless gold plating bath that manages the consumption of cyanide gold salts due to electroplating treatment is maintained.

The best form for implementing the invention

Hereinafter, the present invention will be described in more detail.

The electroless gold plating bath of the present invention contains a gold cyanide salt, a complexing agent, a formaldehyde bisulfite adduct, and the following general formula (1) or (2) R ₁ -NH-C ₂ H ₄ -NH -R ₂ (1) R ₃ -(CH ₂ -NH-C ₂ H ₄ -NH-CH ₂ ) _n -R ₄ (2) (in the formulae (1) and (2), R ₁ , R ₂ , R ₃ and R ₄ represent -OH, -CH ₃ , -CH ₂ OH, -C ₂ H ₄ OH, -CH ₂ N(CH ₃ ) ₂ , -CH ₂ NH(CH ₂ OH), -CH ₂ NH ( C ₂ H ₄ OH), -C ₂ H ₄ NH(CH ₂ OH), -C ₂ H ₄ NH(C ₂ H ₄ OH), -CH ₂ N(CH ₂ OH) ₂ , -CH ₂ N (C ₂ H ₄ OH) ₂ , -C ₂ H ₄ N(CH ₂ OH) ₂ or -C ₂ H ₄ N(C ₂ H ₄ OH) ₂ , which may be the same or different, n is an integer from 1 to 4) Amine compound.

The electroless gold plating bath of the present invention is different from the conventional substituted gold plating bath in the same electroplating bath as the substitution-reduction type electroless gold plating bath which is carried out by both the reaction and the reduction reaction. In the gold plating bath, an amine compound containing a formaldehyde bisulfite adduct and a specific structure represented by the above general formula (1) or (2) is used, and the electroless gold plating bath of the present invention is used for copper, nickel, or the like. On the underlying metal, gold is precipitated by the substitution reaction, and gold is precipitated from the reducing agent by using the precipitated gold as a catalyst.

Since the electroless gold plating bath of the present invention suppresses the erosion of the underlying metal to a minimum, the underlying metal ions are dissolved in the electroplating bath, and the stable deposition rate can be maintained even after long-term use. For example, in the case of usual substitution plating, the amount of precipitated gold and the eluted underlying metal (for example, copper or nickel) is equal by the stoichiometric amount, and in the electroplating bath of the present invention, for example, when the ENIG step is performed, most of the precipitation occurs. The gold is displaced by the substitution plating to the reduction plating, and the precipitation of the eluted underlying nickel is very small with respect to the precipitated gold. In this case, it can be suppressed to about 1/8 of the conventional usual substitution gold plating.

Therefore, the corrosion of the underlying metal can be suppressed to a minimum, and Uniform dense gold-plated film. Further, since the reducing agent is contained, gold is continuously deposited on the precipitated gold. Therefore, gold plating for thickening is not additionally performed, and one plating bath can be thickened. In addition, the precipitation rate of gold can be stably maintained, and even if the film is thickened, the plating film is not reddish, and the gold-colored lemon yellow is maintained.

When the bottom layer is palladium, unlike nickel or copper, the potential difference between palladium and gold is small. Therefore, when a conventional substitution type gold plating bath is used for gold plating on palladium, a uniform film thickness cannot be obtained, and a sufficient film thickness cannot be obtained. On the other hand, in the electroless gold plating bath of the present invention, the surface of palladium is activated, palladium is used as a catalyst, gold can be precipitated from a reducing agent, and gold can be precipitated by using precipitated gold as a catalyst. Therefore, even on palladium, The gold-plated film can still be thickened.

Examples of the gold cyanide salt contained in the electroless gold plating bath of the present invention include gold cyanide, gold potassium cyanide, gold gold cyanide, gold ammonium cyanide, and the like, and potassium gold cyanide and sodium gold cyanide. Especially good.

The content of the cyanide gold salt during the construction of the bath and after the replenishment is preferably 0.0001 to 1 mol/L on a gold basis, and particularly preferably from 0.001 to 0.5 mol/L. When the above range is not satisfied, the precipitation rate is lowered, and if it exceeds the above range, it is economically disadvantageous.

As the complexing agent contained in the electroless gold plating bath of the present invention, a known complexing agent used in the electroless plating bath can be used, and examples thereof include phosphate, boric acid, citric acid, gluconic acid, tartaric acid, and lactic acid. Malic acid, ethyl diamine, triethanolamine, ethyldiaminetetraacetic acid, nitrilotriacetic acid, diethylidene triamine pentaacetic acid, hydrocarbon ethylethyldiaminetriacetic acid, triamethylenetetraamine Hexaacetic acid, 1,3-propanediaminetetraacetic acid, 1,3-diamino-2-hydrocarbylpropanetetraacetic acid, hydrocarbon ethylimidodiacetic acid, dihydroglycine, glycol ether diamine Tetraacetic acid, dicarboxymethylglutamic acid, hydrocarbyl ethylene diphosphate, ethyldiamine tetra(methylphosphoric acid), or alkali metal (such as sodium, potassium), alkaline earth metal salt, ammonium salt Wait.

The concentration of the complexing agent in the bath and after the replenishment is preferably 0.001 to 1 mol/L, and preferably 0.01 to 0.5 mol/L. When the range is less than the above range, the precipitation rate is lowered by the eluted metal, and if it exceeds the above range, it is economically disadvantageous.

The electroless gold plating bath of the present invention contains a formaldehyde bisulfite adduct. Specific examples of the formaldehyde hydrogen sulfite adduct include, for example, sodium formaldehyde sulfite, potassium formaldehyde sulfite, ammonium formaldehyde sulfite, and the like.

The concentration of such formaldehyde bisulfite adducts in the bath and after replenishment is preferably 0.0001 to 0.5 mol/L, and particularly preferably 0.001 to 0.3 mol/L. When the above range is not satisfied, the underlying nickel is corroded, and if it exceeds the above range, the plating bath becomes unstable.

The electroless gold plating bath of the present invention contains the following general formula (1) or (2) R ₁ -NH-C ₂ H ₄ -NH-R ₂ (1) R ₃ -(CH ₂ -NH-C ₂ H ₄ -NH-CH ₂ ) _n -R ₄ (2) (In the formulae (1) and (2), R ₁ , R ₂ , R ₃ and R ₄ represent -OH, -CH ₃ , -CH ₂ OH, - C ₂ H ₄ OH, -CH ₂ N(CH ₃ ) ₂ , -CH ₂ NH(CH ₂ OH), -CH ₂ NH(C ₂ H ₄ OH), -C ₂ H ₄ NH(CH ₂ OH), -C ₂ H ₄ NH(C ₂ H ₄ OH), -CH ₂ N(CH ₂ OH) ₂ , -CH ₂ N(C ₂ H ₄ OH) ₂ , -C ₂ H ₄ N(CH ₂ OH) ₂ Or -C ₂ H ₄ N(C ₂ H ₄ OH) ₂ , which may be the same or different, and n is an integer of 1 to 4). The formaldehyde hydrogen sulfite adduct of the present invention is only a formaldehyde hydrogen sulfite adduct which does not act as a reducing agent, and a reducing action occurs when it coexists with the amine compound.

The concentration of the amine compound in the bath and after the replenishment is preferably 0.001 to 3 m/L, and preferably 0.01 to 1 mol/L. When the above range is not satisfied, there is a possibility that the deposition rate is lowered, and if it exceeds the above range, the electrolytic bath may become unstable.

The electroless gold plating bath of the present invention may be added with a stabilizer which is known for electroless plating. Examples of the stabilizer include sulfides of 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, mercaptoacetic acid, mercaptosuccinic acid, thiosulfuric acid, thioglycol, thiourea, thiomalic acid, and the like. And a nitrogen compound such as triazole or 1,2,4-aminotriazole.

The concentration of stabilizer in Yujian bath and after replenishment is preferably 0.0000001~0.01 mol/L, especially 0.000001~0.005 mol/L. When the above range is not satisfied, the plating bath may become unstable, and if it exceeds the above range, the deposition rate may decrease.

The pH of the electroless gold plating bath of the present invention is preferably from 5 to 10. When the range is less than the above range, the deposition rate is lowered, and if it exceeds the above range, the plating bath may become unstable. As the pH adjuster, sodium hydroxide, potassium hydroxide, ammonia, sulfuric acid, phosphoric acid, boric acid or the like which is used in a known plating bath can be used.

Further, the use temperature of the electroless gold plating bath of the present invention is preferably 70 to 90 °C. When the above range is not satisfied, there is a possibility that the deposition rate is lowered, and if it exceeds the above range, the plating bath may become unstable.

In the present invention, the above electroless gold plating bath continuously maintains the bath temperature at 70. When the temperature is ~90 ° C, especially 80 ° C or higher, the above-mentioned formaldehyde hydrogen sulfite adduct as an electroless gold plating bath component is periodically replenished by a cyanide base such as sodium hydroxide or potassium hydroxide as a first replenishing component. And amine compounds, can maintain the electroplating ability of electroless gold plating bath.

At this time, the replenishment ratio of the cyanide base, the formaldehyde bisulfite adduct and the amine compound is supplemented with these components to form a cyanide base: formaldehyde bisulfite adduct: amine compound = 0.5 to 5: 1: 0.1 ~5 (Morbi) is appropriate. When the ratio of the supply exceeds this, when the cyanide base is excessive, the coating power of gold is lowered, and the nickel is corroded, and when it is too small, the decomposition of the electrolytic bath is accelerated. When the formaldehyde bisulfite adduct is excessive, there is an increase in the decomposition of the electrolytic bath. When the amount is too small, the reducing power is lowered, the nickel is corroded, and the coating power of gold is lowered. When the amine compound is excessive, there is an increase in the decomposition of the electrolytic bath. When the amount is too small, the reducing power is lowered, the nickel is corroded, and the coating power of gold is lowered. At this time, the balance between the formaldehyde bisulfite adduct and the amine compound is particularly important.

Further, in the present invention, the cyanide gold salt, the formaldehyde hydrogen sulfite adduct, and the amine compound which are added to the electroless gold plating bath component may be added to the electroplating bath in which the gold is consumed by the electroplating treatment. 2 supply ingredients.

At this time, the replenishment ratio of the gold cyanide salt, the formaldehyde bisulfite adduct and the amine compound is replenished to the cyanide gold salt: formaldehyde bisulfite adduct: amine compound=1: 0.1~5 : 0.5~5 (Morbi) is appropriate. When the replenishment ratio is exceeded, when the gold cyanide salt is excessive, the cost is unfavorable, and when the amount is too small, the gold concentration is lowered, and the gold film characteristics are deteriorated. When the formaldehyde bisulfite adduct is excessive, there is an increase in the decomposition of the electrolytic bath. When the amount is too small, the reducing power is lowered, the nickel is corroded, and the coating power of gold is lowered. Amination When the compound is excessive, there is an increase in the decomposition of the electrolytic bath. When the amount is too small, the reducing power is lowered, the nickel is corroded, and the coating power of gold is lowered. At this time, the balance between the formaldehyde bisulfite adduct and the amine compound is particularly important.

In addition, in the respective replenishment of the first and second replenishing components, the concentration of the bath is 0.1 to 5 mol% based on the formaldehyde bisulfite adduct, and is 1 to 20 per hour. In this case, it is preferred to replenish at equal intervals, and the amount of replenishment of the formaldehyde bisulfite adduct is preferably 2 mmol or less per 1 L of the plating bath. If the replenishment interval is too long, the composition change in the plating bath becomes large, and the film characteristics may be irregular. Further, when the amount of replenishment is too large, the composition change in the plating bath becomes large, and the film characteristics are not uniform.

Further, in the present invention, part or all of the formaldehyde hydrogen sulfite adduct is supplied, and the formaldehyde hydrogen sulfite adduct is replaced, and the formaldehyde hydrogen sulfite adduct is supplied in the same molar amount as the formaldehyde. The formaldehyde bisulfite adduct is produced by the temperature rise of the electroplating bath or by electroplating to produce sulfurous acid, and the produced sulfurous acid is deposited in the electroplating bath. In the electroplating bath, sulfurous acid suppresses the reaction by the reducing agent, so it acts as a so-called stabilizer for preventing decomposition of the plating bath, but when it is excessive, sulfurous acid suppresses the reaction by the reducing agent, and the substitution reaction ratio increases, and the underlying nickel is present. Corrosion. If the underlying nickel is corroded, due to defects such as reduced solder jointability, some or all of the formaldehyde bisulfite adduct is replaced by the formaldehyde bisulfite adduct, and the hydrogen peroxide is replenished. The salt adduct is the same as the molar amount of formaldehyde, which can suppress the above-mentioned adverse conditions due to excess sulfite. In particular, the formaldehyde bisulfite adduct in the first replenishing component and the formaldehyde in the second replenishing component are also used. Since it is easy to manage the replenishing component, the concentration of sulfurous acid in the plating bath can be appropriately maintained, and the electrolytic bath stability and solder jointability are all good, so it is suitable.

In particular, in the replenishment of the second replenishing component, the total amount of gold supplied by the second replenishing component to the plating bath is 0.2 g/L or more, and preferably 0.1 g/L or more, instead of formaldehyde sulfurous acid. The hydrogen salt adduct is replenished with formaldehyde formaldehyde bisulfite adduct with the molar amount of formaldehyde.

In the electroless gold plating bath of the present invention, the bisulfite adduct of formaldehyde in the bath coexists with the amine compound, and it is considered that a formaldehyde-amine complex represented by the following formula is produced as a reducing agent component.

Formaldehyde bisulfite adduct + amine compound →Reducing agent component (formaldehyde-amine complex) + sulfurous acid

This reducing agent component (formaldehyde-amine complex) is consumed in the bath, that is, the bisulfite adduct of formaldehyde and the amine compound are consumed. At this time, it is necessary to supply the consumed bisulfite adduct of formaldehyde and the amine compound, but it is also possible to supply formaldehyde to replace the bisulfite adduct of formaldehyde. At the time of replenishment, if the replenishment balance of each component is not considered, the replenishment ratio must be considered because of a problem such as bath decomposition, nickel corrosion, and reduction in the gold coating power. That is, the bisulfite adduct of formaldehyde: an amine compound, a formaldehyde: an amine compound or a bisulfite adduct of formaldehyde, and a formaldehyde: an amine compound, which are important in a certain ratio at a molar ratio.

The electroless gold plating bath of the present invention can be used as a material of a metal surface (plated surface) of the substrate during the plating treatment, and may be made of copper, a copper alloy, nickel, a nickel alloy, palladium or a palladium alloy. Examples of the nickel alloy include a nickel-phosphorus alloy and a nickel-boron alloy. Examples of the palladium alloy include palladium-phosphorus. Alloys, etc. Such a metal surface is itself a surface of a metal (alloy), and may be a surface of the film formed by a metal film on the surface of the substrate. The metal film may be formed by electroplating, and may be formed by electroless plating. However, when it is nickel, a nickel alloy, palladium or a palladium alloy, it is generally formed by electroless plating. In addition, the surface of the palladium or palladium alloy film formed on the substrate via a nickel or nickel alloy film is also suitable for electroless gold plating.

The electroless gold plating bath of the present invention can be used for ENIG (Electroless Nickel Immersion Gold), that is, a method of forming a gold-plated film on a bottom electroless nickel plating film formed on copper, DIG (Direct Immersion Gold), That is, a method of directly forming a gold-plated film on copper, ENEPIG (Electroless Nickel Ekectroless Palladium Immersion Gold), that is, on a bottom electroless nickel plating film (formed on copper), forming a gold plating through an electroless palladium coating film A gold-plated film of any of the methods of the film is formed.

The electroless gold plating bath of the present invention and the electroless gold plating method using the same are suitably used, for example, when a wiring circuit mounting portion or a terminal portion of an electronic component such as a printed wiring board or an IC package is subjected to gold plating treatment. The gold plating treatment can be suitably applied to the method of maintaining the electroplating ability of the electroless gold plating bath of the present invention.

Further, in the plating bath of the present invention, even when the metal surface (electroplated surface) is copper, a good film can be obtained, and when the underlayer is copper, good solder bonding properties for suppressing oxidation and diffusion of copper can be obtained. In addition, thick film formation can also be used for wire bonding. In addition, because the electroplating bath of the present invention is still on palladium A good gold film can be deposited, which is most suitable for lead-free solder bonding or wire bonding.

When the bottom layer is palladium, unlike the case of nickel or copper, the potential difference between palladium and gold is small. Therefore, when a conventional substitution type gold plating bath is used for gold plating on palladium, a uniform film thickness cannot be obtained, and a sufficient film thickness cannot be obtained. On the other hand, in the electroless gold plating bath of the present invention, the surface of palladium is activated, palladium is used as a catalyst, gold can be precipitated by a reducing agent, and gold is precipitated by using precipitated gold as a catalyst, so that even if On the palladium, the gold plating film can still be thickened.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples and comparative examples, but the present invention is not limited to the following examples.

[Examples 1, 2 and Comparative Example 1]

The gold plating bath shown in Table 1 was used as an electroplating bath at the time of bathing, and this temperature was maintained at 80 ° C, and the first supply of the ratio shown in Table 2 was not periodically replenished (Example 1, 2) or not supplied (Comparative Example 1). Ingredients, keep it for 100 hours. By visually checking the state of the plating solution, it was confirmed whether or not the gold was precipitated in the container, and when it was not deposited, the treatment shown in Table 6 as a nickel/gold step was applied to the copper-plated printed substrate, and immersed in each gold-plated bath. The results of gold plating and confirming the appearance of plating are shown in Table 3. The replenishment amount of potassium cyanide per hour is 15 mg/L, and the replenishment component is replenished every 12 minutes at the above ratio every 5 hours.

[Examples 3, 4]

The operation was carried out under the conditions of Example 1, and the first replenishing component shown in Example 1 was added, and the second replenishing component shown in Table 4 was used, and each time the gold was consumed, 0.1 g/L of gold was used. Potassium replenishment is 0.15g/L, The above ratio is replenished. Each of 0.5 g/L of gold was supplied to the copper-clad printed substrate as shown in Table 6 of the nickel/gold step, and immersed in each gold plating bath to be gold-plated. The obtained gold-plated film was peeled off from gold by the Kokumura Industrial Gold Stripping Agent COPKIA RIP, and the presence or absence of corrosion of the nickel surface after peeling off the gold is shown in Table 5.

In Example 3, instead of sodium formaldehyde sulfite, it was replenished with formaldehyde in the same molar amount. Since the sulfurous acid was not produced excessively, the nickel surface after peeling gold was not corroded well, but on the other hand, in Example 4, it was considered that gold was supplied. The total amount exceeds 1g/L, the excess production of sulfite is excessive, and the surface of nickel after corrosion is corroded. .

Claims (9)

A method for maintaining the electroplating ability of an electroless gold plating bath, in order to maintain a gold cyanide salt, a complexing agent, a formaldehyde bisulfite adduct, and a general formula (1) or (2) R ₁ -NH- C ₂ H ₄ -NH-R ₂ (1) R ₃ -(CH ₂ -NH-C ₂ H ₄ -NH-CH ₂ ) _n -R ₄ (2) (in the formulae (1) and (2), R ₁ , R ₂ , R ₃ and R ₄ represent -OH, -CH ₃ , -CH ₂ OH, -C ₂ H ₄ OH, -CH ₂ N(CH ₃ ) ₂ , -CH ₂ NH(CH ₂ OH) , -CH ₂ NH(C ₂ H ₄ OH), -C ₂ H ₄ NH(CH ₂ OH), -C ₂ H ₄ NH(C ₂ H ₄ OH), -CH ₂ N(CH ₂ OH) ₂ , -CH ₂ N(C ₂ H ₄ OH) ₂ , -C ₂ H ₄ N(CH ₂ OH) ₂ or -C ₂ H ₄ N(C ₂ H ₄ OH) ₂ , which may be the same or different, n is The electroless gold plating bath of the amine compound represented by the integer of 1 to 4 is in a state of 70 to 90 ° C, and the method of managing the electroplating ability of the electroless gold plating bath is stably maintained, and is characterized in that it is periodically replenished as the first replenishing component. The cyanide base and the formaldehyde hydrogen sulfite adduct and the amine compound. The method for maintaining the electroplating ability of an electroless gold plating bath according to the first aspect of the patent application, wherein the supply ratio of the cyanide base, the formaldehyde bisulfite adduct and the amine compound is replenished to a cyanide base: formaldehyde sulfurous acid Hydrogen salt adduct: amine compound = 0.5~5:1:0.1~5 (mole ratio). For example, in the method of claim 2, the method for maintaining the electroplating ability of the electroless gold plating bath, wherein the concentration of the bath is 0.1 to 5 mol% per hour, based on the formaldehyde bisulfite adduct. The first supply component is replenished in 1 to 20 times. For example, the maintenance management of electroless gold plating bath in the first application of patent scope In the method of electroplating ability, the cyanide gold salt, the formaldehyde hydrogensulfite adduct, and the amine compound as the second replenishing component are further supplied to the electroplating bath in which the gold is consumed by the electroplating treatment. For example, in the method of claim 4, the method for maintaining the electroplating ability of the electroless gold plating bath, wherein the supply ratio of the cyanide gold salt, the formaldehyde bisulfite adduct and the amine compound is replenished into a gold cyanide salt: formaldehyde Bisulfite adduct: amine compound = 1: 0.1 ~ 5: 0.5 ~ 5 (mole ratio). For example, in the method of claim 5, the method for maintaining the electroplating ability of the electroless gold plating bath, wherein the concentration of the bath is 0.1 to 5 mol% per hour, based on the formaldehyde bisulfite adduct. The second supply component is replenished in 1 to 20 times. The method for maintaining the electroplating ability of an electroless gold plating bath according to the third or sixth aspect of the patent application, wherein the first supply of the formaldehyde bisulfite adduct is less than 2 millimoles per 1 L of the electroplating bath. . A method for maintaining the electroplating ability of an electroless gold plating bath according to any one of the first to third aspects of the patent application, wherein the formaldehyde bisulfite adduct is replaced by a formaldehyde replenishing portion with a molar amount Or all of the supplemental formaldehyde bisulfite adduct. A method for maintaining the electroplating ability of an electroless gold plating bath according to the first aspect of the patent application, wherein in the general formulas (1) and (2) of the amine compound, R ₁ and R ₃ represent -OH, -CH ₂ OH , -C ₂ H ₄ OH, -CH ₂ N(CH ₃ ) ₂ , -CH ₂ NH(CH ₂ OH), -CH ₂ NH(C ₂ H ₄ OH), -C ₂ H ₄ NH(CH ₂ OH ), -C ₂ H ₄ NH(C ₂ H ₄ OH), -CH ₂ N(CH ₂ OH) ₂ , -CH ₂ N(C ₂ H ₄ OH) ₂ , -C ₂ H ₄ N(CH ₂ OH ₂ or -C ₂ H ₄ N(C ₂ H ₄ OH) ₂ , R ₂ and R ₄ represent -OH, -CH ₃ , -CH ₂ OH, -C ₂ H ₄ OH, -CH ₂ N (CH _{3 2} , -CH ₂ NH(CH ₂ OH), -CH ₂ NH(C ₂ H ₄ OH), -C ₂ H ₄ NH(CH ₂ OH), -C ₂ H ₄ NH(C ₂ H ₄ OH) , -CH ₂ N(CH ₂ OH) ₂ , -CH ₂ N(C ₂ H ₄ OH) ₂ , -C ₂ H ₄ N(CH ₂ OH) ₂ or -C ₂ H ₄ N (C ₂ H ₄ OH ) ₂ .