JP2008169425A - Plating ability maintenance management method of electroless gold plating bath - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for maintaining the plating capability of an electroless gold-plating bath stably for a long period of time, which can provide the plated film of gold showing excellent appearance without causing a poor appearance due to a progress of the intergranular corrosion of a nickel surface, and to further provide a method for maintaining the electroless gold-plating bath in which a gold cyanide salt has been consumed due to plating treatment, stably for a long period of time. <P>SOLUTION: The method for stably maintaining the plating capability of the electroless gold-plating bath containing a gold cyanide salt, a complexing agent, a formaldehyde bisulfite adduct and an amine compound in a state of having kept the bath at 70 to 90°C includes periodically supplying an alkali cyanide, a formaldehyde bisulfite adduct and an amine compound as first supply components to the plating bath, and further supplying only a gold cyanide salt, a formaldehyde bisulfite adduct and an amine compound as second supply components to the plating bath in which the gold has been consumed due to the plating treatment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  Gold is the metal with the smallest ionization tendency, that is, the most stable and rust-resistant metal. In addition, it is also widely used in the electronics industry because of its excellent electrical conductivity. Displacement gold plating is widely used as a final surface treatment for printed circuit boards, IC package mounting parts, terminal parts, and the like. Specifically, for example, there are the following methods, each having the following characteristics.

(1) ENIG (Electroless Nickel Immersion Gold)
-This is a method of forming a displacement gold plating film on a base electroless nickel plating film.
・ Can prevent copper diffusion, prevent nickel oxidation, and improve the corrosion resistance of circuits and terminals.
・ Can be used for solder joints.
-It can also be used for wire bonding by applying thickening after ENIG processing.
In the case of wire bonding, heat treatment is performed after the plating treatment, which causes nickel to diffuse on the gold film. In order to prevent this, electroless gold plating is further applied on the nickel / substituted gold film, and the gold film thickness is increased to cope with nickel diffusion.

(2) DIG (Direct Immersion Gold)
-This is a method of forming a displacement gold plating film directly on copper.
-It can prevent copper oxidation, prevent copper diffusion, and improve the corrosion resistance of circuits and terminals.
・ Can also be used for solder bonding and wire bonding.
-Compared to nickel / gold or nickel / palladium / gold, the long-term reliability is slightly inferior, but it can be used satisfactorily under conditions where the heat load is not so high (conditions such as low heat treatment temperature and few reflows).
・ Since it is a simple process, it is low cost.

(3) ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold)
This is a method of providing an electroless palladium plating film between the base electroless nickel plating film and the displacement gold plating film.
-Prevents copper diffusion, prevents nickel oxidation and diffusion, and improves corrosion resistance of circuits and terminals.
・ It is most suitable for lead-free solder joints that have been promoted in recent years (lead-free solder is subject to a thermal load during solder joining compared to tin-lead eutectic solder, and the joint characteristics of nickel / gold are reduced).
・ Suitable for wire bonding.
-Nickel diffusion does not occur even if the gold film thickness is not increased.
-Even if nickel / gold can be used, it is suitable for higher reliability.

  In displacement gold plating, gold is deposited by utilizing the difference in oxidation-reduction potential in a plating bath with a base such as nickel. Therefore, corrosion points due to oxidation (elution) occur when gold erodes nickel. This corrosion point due to oxidation becomes a hindrance when connecting tin and nickel of the solder layer during the subsequent solder reflow, and there is a problem that joint characteristics such as strength are deteriorated.

  In order to solve this problem, an electroless gold plating bath containing a sulfite adduct of an aldehyde is disclosed in Japanese Patent Application Laid-Open No. 2004-137589 (Patent Document 1), wherein a gold plating bath containing a hydroxyalkylsulfonic acid is Each is disclosed in International Publication No. 2004/111287 pamphlet (Patent Document 2). These techniques are intended to suppress corrosion of the base metal.

However, when a primary amine compound having an amino group (—NH ₂ ) such as triethylenetetramine described in International Publication No. 2004/111287 pamphlet (Patent Document 2) is used, grain boundaries on the nickel surface are used. As the erosion progresses, the covering power of gold is reduced, and the film appearance becomes red.

JP 2004-137589 A International Publication No. 2004/111287 Pamphlet JP 2002-226975 A Japanese Patent No. 2538461

  The present invention has been made in view of the above circumstances, and does not cause poor appearance due to the progress of grain boundary erosion on the nickel surface, and the plating ability of an electroless gold plating bath that provides a gold-plated film having a good film appearance. And a method for stably maintaining and managing an electroless gold plating bath in which gold cyanide salt has been consumed by plating treatment for a long period of time. .

The present inventor made gold cyanide as a gold component, formaldehyde bisulfite adduct as a reducing agent component, 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 formulas (1) and (2), R ₁ , R ₂ , R ₃ and R ₄ are —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 represents the same or different, and n is an integer of 1 to 4.)
By using an electroless gold plating bath containing an amine compound represented by the above, it was found that the intergranular corrosion of the nickel surface as described above is less likely to occur. Regardless of, the formaldehyde bisulfite adduct, which is a component of cyanide and reducing agent, and the amine compound represented by the above general formula (1) or (2) gradually disappear from the plating bath, thereby causing bath decomposition. I found out there was a problem. Therefore, it has been found that the above problem can be solved by replenishing these disappearing components in small amounts at an appropriate concentration ratio.

That is, this invention provides the plating ability maintenance management method of the following electroless gold plating baths.
[1] Gold cyanide salt, complexing agent, 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 formulas (1) and (2), R ₁ , R ₂ , R ₃ and R ₄ are —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 represents the same or different, and n is an integer of 1 to 4.)
A method for stably maintaining and managing the plating performance of the electroless gold plating bath in a state where the electroless gold plating bath containing the amine compound represented by the formula is maintained at 70 to 90 ° C., comprising alkali cyanide and formaldehyde A plating capacity maintenance and management method for an electroless gold plating bath, wherein a bisulfite adduct and an amine compound are periodically replenished as a first replenishing component.
[2] The supply ratio of the alkali cyanide, formaldehyde bisulfite adduct, and amine compound is alkali cyanide: formaldehyde bisulfite adduct: amine compound = 0.5 to 5: 1: 0.1 to 5 ( The plating ability maintenance and management method for the electroless gold plating bath according to [1], wherein the molar ratio is replenished.
[3] The above-mentioned first replenishing component is replenished in an amount of 0.1 to 5 mol% of the concentration at the time of building bath in 1 to 20 times per hour on the basis of the formaldehyde bisulfite adduct. [2] The plating ability maintenance and management method of the electroless gold plating bath according to [2].
[4] Further, the gold cyanide salt, formaldehyde bisulfite adduct and amine compound are replenished as a second replenishing component to the plating bath in which gold is consumed by the plating treatment [1] The plating ability maintenance management method of the electroless gold-plating bath in any one of thru | or [3].
[5] The replenishment ratio of the gold cyanide salt, formaldehyde bisulfite adduct and amine compound is as follows: gold cyanide salt: formaldehyde bisulfite adduct: amine compound = 1: 0.1 to 5: 0.5 to 5. The plating ability maintenance and management method for an electroless gold plating bath according to [4], wherein replenishment is performed so as to be 5 (molar ratio).
[6] The above-mentioned second replenishing component is replenished in an amount of 0.1 to 5 mol% of the concentration at the time of bathing on the basis of the formaldehyde bisulfite adduct, divided into 1 to 20 times per hour. [5] The plating ability maintenance and management method of the electroless gold plating bath according to [5].
[7] The plating capacity maintenance management of the electroless gold plating bath according to [3] or [6], wherein the amount of one-time replenishment of the formaldehyde bisulfite adduct is 2 mmol or less per liter of the plating bath Method.
[8] A part or all of the replenished formaldehyde bisulfite adduct is supplemented with the same molar amount of formaldehyde instead of the formaldehyde bisulfite adduct. The plating capacity maintenance management method of the electroless gold plating bath in any one.

  According to the present invention, the plating ability of an electroless gold plating bath that forms a gold plating film having a good film appearance is stably maintained for a long period of time without causing appearance defects due to the progress of grain boundary erosion on the nickel surface. The electroless gold plating bath in which the gold cyanide salt has been consumed by the plating treatment can be stably maintained for a long period of time.

The present invention will be described in detail below.
The electroless gold plating bath of the present invention comprises 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 formulas (1) and (2), R ₁ , R ₂ , R ₃ and R ₄ are —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 may be the same or different, and n is an integer of 1 to 4.)
The amine compound represented by these is contained.

  The electroless gold plating bath of the present invention is a substitution-reduction type electroless gold plating bath in which both a substitution reaction and a reduction reaction proceed in the same plating bath, unlike a conventional substitution gold plating bath. The electroless gold plating bath of the present invention contains a formaldehyde bisulfite adduct and an amine compound having a specific structure represented by the general formula (1) or (2) in the gold plating bath. Gold is deposited by a substitution reaction on a base metal such as copper or nickel, and gold is deposited by a reducing agent using the deposited gold as a catalyst.

  In the electroless gold plating bath of the present invention, since the erosion of the base metal is minimized, the dissolution of the base metal ions in the plating bath is small, and a stable deposition rate is maintained even when used over a long period of time. It is. For example, in the case of ordinary displacement plating, the amount of deposited gold and eluted base metal (for example, copper or nickel) is equivalent according to the stoichiometry, but in the plating bath of the present invention, for example, the ENIG process was performed. In this case, since most of the gold deposition shifts from displacement plating to reduction plating, the dissolution of the underlying nickel that elutes with respect to the deposited gold is very small. In this case, 1/8 of the conventional ordinary displacement gold plating. To a certain extent.

  As a result, it is possible to obtain a uniform and dense gold plating film while minimizing the erosion of the base metal. In addition, because it contains a reducing agent, gold continuously deposits on the deposited gold, so it is possible to increase the film thickness with one plating bath without separately performing gold plating for thickening. is there. In addition, the deposition rate of gold can be stably maintained, and even if the film thickness is increased, the plating film does not become reddish, and the lemon yellow color peculiar to gold can be maintained.

  When the base is palladium, unlike nickel and copper, palladium and gold have a small potential difference. Therefore, if gold plating is performed on palladium using a conventional substitutional gold plating bath, a uniform film thickness cannot be obtained, and a sufficient film thickness cannot be obtained. On the other hand, the electroless gold plating bath of the present invention can activate the palladium surface, deposit gold with a reducing agent using palladium as a catalyst, and further deposit gold using the deposited gold as a catalyst. Therefore, it is possible to increase the thickness of the gold plating film even on palladium.

  Examples of the gold cyanide salt contained in the electroless gold plating bath of the present invention include gold cyanide, potassium gold cyanide, sodium gold cyanide, ammonium gold cyanide and the like. Preferably it is sodium hydride.

  The content of the gold cyanide salt at the time of bathing and after replenishment is preferably 0.0001 to 1 mol / L, more preferably 0.001 to 0.5 mol / L, based on gold. If it is less than the above range, the deposition rate may be reduced, and if it exceeds the above range, it may be 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. For example, phosphoric acid, boric acid, citric acid, Gluconic acid, tartaric acid, lactic acid, malic acid, ethylenediamine, triethanolamine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid, triethylenetetraminehexaacetic acid, 1,3-propanediaminetetraacetic acid, 1 , 3-Diamino-2-hydroxypropanetetraacetic acid, hydroxyethyliminodiacetic acid, dihydroxylglycine, glycol ether diamine tetraacetic acid, dicarboxymethyl glutamic acid, hydroxyethylidene diphosphoric acid, ethylenediamine tetra (methylene phosphoric acid), or an alkali metal thereof (For example, Sodium, potassium) salts, alkaline earth metal salts, ammonium salts and the like.

  The concentration of the complexing agent during the bathing and after replenishment is preferably 0.001 to 1 mol / L, and more preferably 0.01 to 0.5 mol / L. If it is less than the above range, the elution metal may cause a decrease in the deposition rate, and if it exceeds the above range, it may be economically disadvantageous.

  The electroless gold plating bath of the present invention contains formaldehyde bisulfite adduct. Specific examples of the formaldehyde bisulfite adduct include sodium formaldehyde bisulfite, potassium formaldehyde bisulfite, and ammonium formaldehyde bisulfite.

  The concentration of these formaldehyde bisulfite adducts during the bath and after replenishment is preferably 0.0001 to 0.5 mol / L, more preferably 0.001 to 0.3 mol / L. . If it is less than the above range, the underlying nickel may corrode, and if it exceeds the above range, the bath may become unstable.

The electroless gold plating bath of the present invention has 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 formulas (1) and (2), R ₁ , R ₂ , R ₃ and R ₄ are —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 may be the same or different, and n is an integer of 1 to 4.)
The amine compound represented by these is contained. The formaldehyde bisulfite adduct of the present invention does not act as a reducing agent in the formaldehyde bisulfite adduct alone, and a reducing action occurs when it coexists with this amine compound.

  The concentration of these amine compounds at the time of bathing and after replenishment is preferably 0.001 to 3 mol / L, and more preferably 0.01 to 1 mol / L. If it is less than the above range, the deposition rate may be reduced, and if it exceeds the above range, the bath may be unstable.

  A stabilizer used in known electroless plating can be added to the electroless gold plating bath of the present invention. As this stabilizer, 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, mercaptoacetic acid, mercaptosuccinic acid, thiosulfuric acid, thioglycol, thiourea, thiomalic acid and other sulfur compounds, benzotriazole, 1,2,4- Examples thereof include nitrogen compounds such as aminotriazole.

  The concentration of the stabilizer during the bathing and after replenishment is preferably 0.0000001 to 0.01 mol / L, and more preferably 0.000001 to 0.005 mol / L. If it is less than the above range, the 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 5-10. If it is less than the above range, the deposition rate may be reduced, and if it exceeds the above range, the bath may be unstable. As the pH adjuster, sodium hydroxide, potassium hydroxide, ammonia, sulfuric acid, phosphoric acid, boric acid and the like used in known plating baths can be used.

  Moreover, it is preferable that the operating temperature of the electroless gold plating bath of this invention is 70-90 degreeC. If it is less than the above range, the deposition rate may be reduced, and if it exceeds the above range, the bath may be unstable.

  In the present invention, the electroless gold plating bath described above has an alkali cyanide such as sodium cyanide and potassium cyanide and electroless gold when the bath temperature is continuously maintained at 70 to 90 ° C., particularly 80 ° C. or higher. By periodically replenishing the above-mentioned formaldehyde bisulfite adduct and amine compound as the first replenishing component as components of the plating bath, the plating ability of the electroless gold plating bath can be maintained.

  In this case, the replenishment ratio of alkali cyanide, formaldehyde bisulfite adduct and amine compound was alkali cyanide: formaldehyde bisulfite adduct: amine compound = 0.5-5: 1: 0.1-5 (moles). It is preferable to replenish these components so that If the replenishment ratio is deviated, the covering power of gold decreases if the alkali cyanide is excessive, and nickel may corrode, and if it is too small, the bath decomposition may be accelerated. If the formaldehyde bisulfite adduct is excessive, bath decomposition may be accelerated, and if it is too small, the reducing power is reduced, nickel is corroded, and the gold covering power may be reduced. If the amine compound is excessive, the decomposition of the bath may be accelerated. If the amine compound is excessive, the reducing power is reduced, nickel is corroded, and the gold covering power may be reduced. In this case, the balance between the formaldehyde bisulfite adduct and the amine compound is particularly important.

  Further, in the present invention, the above-described gold cyanide salt, formaldehyde bisulfite adduct and amine compound are further added as components of the electroless gold plating bath to the plating bath in which gold is consumed by the plating treatment. It can be replenished as two replenishing components.

  In this case, the replenishment ratio of gold cyanide, formaldehyde bisulfite adduct and amine compound was gold cyanide: formaldehyde bisulfite adduct: amine compound = 1: 0.1 to 5: 0.5 to 5. It is preferable to replenish these components so that (molar ratio). If this replenishment ratio is deviated, an excessive amount of gold cyanide may be disadvantageous in terms of cost, and if it is too small, the gold concentration may decrease and the gold film characteristics may deteriorate. If the formaldehyde bisulfite adduct is excessive, bath decomposition may be accelerated, and if it is too small, the reducing power is reduced, nickel is corroded, and the gold covering power may be reduced. If the amine compound is excessive, the decomposition of the bath may be accelerated. If the amine compound is excessive, the reducing power is reduced, nickel is corroded, and the gold covering power may be reduced. Again, the balance between the formaldehyde bisulfite adduct and the amine compound is particularly important.

  Moreover, in each replenishment by these 1st and 2nd replenishment components, 0.1-5 mol% of the density | concentration at the time of a building bath is divided into 1-20 times per hour on the basis of formaldehyde bisulfite adduct. Preferably, it is preferably replenished at regular intervals, and the replenishing amount of the formaldehyde bisulfite adduct is preferably 2 mmol or less per liter of the plating bath. If the replenishment interval is too long, the composition change in the plating bath becomes large, and there is a possibility that variations in film characteristics may occur. Further, if the amount of replenishment at one time is too large, the composition change in the plating bath becomes large, and there is a possibility that variations in film characteristics may occur.

  In the present invention, part or all of the formaldehyde bisulfite adduct to be replenished can be supplemented with formaldehyde in the same molar amount as the formaldehyde bisulfite adduct instead of the formaldehyde bisulfite adduct. It is. The formaldehyde bisulfite adduct generates sulfite by increasing the temperature of the plating bath or by plating, and the generated sulfite accumulates in the plating bath. Since sulfurous acid suppresses the reaction caused by the reducing agent in the plating bath, it acts as a so-called stabilizer that prevents the decomposition of the plating bath. This may increase the corrosion of the underlying nickel. Corrosion of the underlying nickel causes problems such as a decrease in solderability, so part or all of the replenished formaldehyde bisulfite adduct is replaced with formaldehyde bisulfite adduct instead of formaldehyde bisulfite adduct. By using the same molar amount of formaldehyde, the above problems due to excessive sulfurous acid can be suppressed. In particular, by using formaldehyde bisulfite adduct in the first replenishing component and formaldehyde in the second replenishing component, it is easy to manage the replenishing component, and the sulfurous acid concentration in the plating bath can be suitably maintained. This is preferable because both bath stability and solderability are improved.

  In particular, in the replenishment of the second replenishing component, the total replenishment amount of gold from the time of building bath by the second replenishing component to the plating bath is 0.2 g / L or more, preferably 0.1 g / L or more. In this case, it is preferable to replenish with formaldehyde in the same molar amount as the formaldehyde bisulfite adduct instead of the formaldehyde bisulfite adduct.

In the electroless gold plating bath of the present invention, a formaldehyde-amine complex as shown in the following formula is formed by the coexistence of a bisulfite adduct of formaldehyde and an amine compound in the bath, and acts as a reducing agent component. It is thought that there is.
Formaldehyde bisulfite adduct + amine compound → reducing agent component (formaldehyde-amine complex) + this reducing agent component (formaldehyde-amine complex) is consumed in the sulfite bath, ie formaldehyde bisulfite adduct and amine compound Will be consumed. At this time, it is necessary to replenish the spent bisulfite adduct of formaldehyde and the amine compound, but formaldehyde may be replenished instead of the bisulfite adduct of formaldehyde. In this replenishment, if the replenishment balance of each component is not taken into consideration, problems such as bath decomposition, nickel corrosion, and decrease in gold covering power occur, so this replenishment ratio needs to be considered. That is, it is important to replenish formaldehyde bisulfite adduct: amine compound, formaldehyde: amine compound or formaldehyde bisulfite adduct and formaldehyde: amine compound at a fixed molar ratio.

  The material of the metal surface (surface to be plated) of the substrate when plating using the electroless gold plating bath of the present invention is intended for copper, copper alloy, nickel, nickel alloy, palladium, palladium alloy, etc. Can do. Examples of the nickel alloy include a nickel-phosphorus alloy and a nickel-boron alloy, and examples of the palladium alloy include a palladium-phosphorus alloy. Such a metal surface may be the surface of the film in which a metal film is formed on the surface of the substrate in addition to the surface of the substrate itself being a metal (alloy). The metal film may be either one formed by electroplating or one formed by electroless plating, but in the case of nickel, nickel alloy, palladium, palladium alloy, one formed by electroless plating is generally used. Is. Furthermore, it is also suitable when the surface of palladium or palladium alloy film formed on the substrate via nickel or nickel alloy film is subjected to electroless gold plating.

  The electroless gold plating bath of the present invention is, for example, ENIG (Electroless Nickel Immersion Gold), that is, a method of forming a gold plating film on a base electroless nickel plating film (formed on copper), DIG (Direct Immersion Gold), a method of forming a gold plating film directly on copper, ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold), ie, an electroless palladium plating film on a base electroless nickel plating film (formed on copper) It can be used for forming any gold plating film in the method of forming a gold plating film through the film.

  The electroless gold plating bath of the present invention and the electroless gold plating method using the same are suitable when, for example, 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, In such gold plating treatment, the method for maintaining and managing the plating ability of the electroless gold plating bath of the present invention can be suitably applied.

  The plating bath of the present invention provides a good film even when the metal surface (surface to be plated) is copper. When the base is copper, oxidation and diffusion of copper are suppressed and good solder joint characteristics are obtained. Further, by increasing the film thickness, it can be used for wire bonding. In addition, the plating bath of the present invention can deposit a good gold film on palladium, and is optimal for use in lead-free solder bonding and wire bonding.

  When the base is palladium, unlike nickel and copper, palladium and gold have a small potential difference. Therefore, if gold plating is performed on palladium using a conventional substitutional gold plating bath, a uniform film thickness cannot be obtained, and a sufficient film thickness cannot be obtained. On the other hand, the electroless gold plating bath of the present invention can activate the palladium surface, deposit gold with a reducing agent using palladium as a catalyst, and further deposit gold using the deposited gold as a catalyst. Therefore, it is possible to increase the thickness of the gold plating film even on palladium.

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

[Examples 1 and 2 and Comparative Example 1]
The gold plating bath shown in Table 1 is used as a plating bath during the building bath, and this is maintained at 80 ° C., and the first supplemental component in the ratio shown in Table 2 is periodically replenished (Examples 1 and 2). ) Or without replenishment (Comparative Example 1) and held for 100 hours. The state of the plating solution is visually checked for the presence or absence of gold deposition on the container, which is a sign of bath decomposition. If there is no deposition, the nickel / gold process is performed on a copper-clad printed board subjected to the treatment shown in Table 6 Table 3 shows the results of immersing in each gold plating bath, applying gold plating, and confirming the plating appearance. The replenishment amount was 15 mg / L per hour, and the replenishment component was replenished every 12 minutes by dividing the replenishment component into 5 times per hour at the above ratio.

○：浴は安定（金析出なし）で、皮膜外観も良好

○: The bath is stable (no gold deposition) and the film appearance is good

[Examples 3 and 4]
The running was performed under the conditions of Example 1, and in addition to the first supplemental component shown in Example 1, the second supplemental component shown in Table 4 was consumed every time 0.1 g / L of gold was consumed. The replenishment amount of potassium gold cyanide per time was set to 0.15 g / L and replenished at the above ratio. Each time gold was supplied at a rate of 0.5 g / L, it was immersed in each gold plating bath on a copper-clad printed board that had been subjected to the treatment shown in Table 6 as a nickel / gold process, and gold plating was performed. Table 5 shows the presence or absence of corrosion on the nickel surface after the gold was peeled off from the obtained gold plating film by Uemura Kogyo gold release agent Coppia Lip.

○：金剥離後のニッケル表面は良好（腐食なし）
△：金剥離後のニッケル表面に僅かに腐食あり
×：金剥離後のニッケル表面に明らかな腐食あり

○: Nickel surface after gold peeling is good (no corrosion)
Δ: Slight corrosion on the nickel surface after gold peeling ×: Clear corrosion on the nickel surface after gold peeling

  In Example 3, replenishment with the same molar amount of formaldehyde instead of formaldehyde sodium bisulfite, so that sulfurous acid is not excessively produced, so that the nickel surface after gold peeling has no corrosion and is good. In Example 4, the nickel surface after gold peeling, which is thought to be due to the excessive generation of sulfurous acid, occurs after the total amount of gold replenishment exceeds 1 g / L.

各工程間 水洗

Washing between processes

Claims (8)

Gold cyanide, complexing agent, 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 formulas (1) and (2), R ₁ , R ₂ , R ₃ and R ₄ are —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 represents the same or different, and n is an integer of 1 to 4.)
A method for stably maintaining and managing the plating performance of the electroless gold plating bath while maintaining the electroless gold plating bath containing the amine compound represented by A plating capacity maintenance and management method for an electroless gold plating bath, wherein a bisulfite adduct and an amine compound are periodically replenished as a first replenishing component.   The replenishment ratio of the above alkali cyanide, formaldehyde bisulfite adduct and amine compound was alkali cyanide: formaldehyde bisulfite adduct: amine compound = 0.5-5: 1: 0.1-5 (molar ratio). The plating capacity maintenance and management method for an electroless gold plating bath according to claim 1, wherein replenishment is performed so that   The first replenishing component is replenished in an amount of 0.1 to 5 mol% of the concentration at the time of building bath in 1 to 20 times per hour on the basis of the formaldehyde bisulfite adduct. The plating ability maintenance management method of the electroless gold plating bath as described.   Further, the gold cyanide salt, formaldehyde bisulfite adduct and amine compound are replenished as a second replenishing component to the plating bath in which gold is consumed by the plating treatment. The plating ability maintenance management method of the electroless gold plating bath of any one of Claims 1.   The replenishment ratio of the above gold cyanide salt, formaldehyde bisulfite adduct and amine compound is as follows: gold cyanide salt: formaldehyde bisulfite adduct: amine compound = 1: 0.1 to 5: 0.5 to 5 (mol) The plating capacity maintenance and management method for an electroless gold plating bath according to claim 4, wherein replenishment is performed so that   6. The second replenishing component is replenished in an amount of 0.1 to 5 mol% of the concentration at the time of building bath based on the formaldehyde bisulfite adduct, divided into 1 to 20 times per hour. The plating ability maintenance management method of the electroless gold plating bath as described.   The method for maintaining and managing the electroless gold plating bath according to claim 3 or 6, wherein the replenishment amount of the formaldehyde bisulfite adduct is 2 mmol or less per liter of the plating bath.   8. A part or all of the replenished formaldehyde bisulfite adduct is replenished with the same molar amount of formaldehyde instead of the formaldehyde bisulfite adduct. For maintaining the plating ability of electroless gold plating baths.