JP3146757B2 - Replacement gold plating solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a displacement gold plating solution.

[0002]

2. Description of the Related Art Conventionally, gold plating is widely used for decorative purposes or for reducing the contact resistance of electrical connection portions of electronic components. As a plating solution used for such gold plating, electrolytic plating is used when the base material is a material having continuous conductivity, but in the case of electronic components, particularly wiring boards and semiconductor devices, isolated conductive portions are used. In many cases, electroless plating is used.

In order to perform such electroless gold plating,
Conventionally, cyanide has been used as a replacement gold plating solution that precipitates gold by replacing the underlying metal. For example, “Practical Plating (I)” published by Maki Shoten in September 1984, edited by the Japan Plating Association includes gold potassium cyanide, nickel chloride, cobalt chloride, disodium ethylenediaminetetraacetate, triethanol It was disclosed that a substituted gold plating solution containing an amine and an ammonium chloride-ammonia buffer was used at a pH of 6 or 9 and a liquid temperature of 95 ° C., and was published by Maki Shoten in September 1984, edited by the Japan Plating Association. (III) "discloses a gold plating solution containing sodium gold cyanide, sodium cyanide, and soda ash.

Japanese Patent Application Laid-Open No. 4-314870 discloses a non-cyan gold-substituted solution containing a non-cyanide gold source, a sulfite, and a metal complexing agent containing a polyamine and an aminocarboxylic acid. The polyamine is used to improve the appearance of the deposited gold plating.

Further, a reduced gold plating solution which contains a reducing agent and deposits gold on a body to be plated by its reducing action is also known. As such materials, those using thiourea as a reducing agent are disclosed in JP-A-62-270779, JP-A-63-79976, and JP-A-2-107780.
And JP-A-4-32575, and those using hydrazine and its compound as a reducing agent are disclosed in JP-A-3-215677 and JP-A-4-314871, and borohydride is used as a reducing agent. Compounds using compounds, hypophosphorous acid, formalin, etc. are disclosed in JP-A-63-7997.
No. 6, JP-A-2-107780, and JP-A-1-125891. Of these, JP-A-62-270779 and JP-A-63-270779
-79976, JP-A-2-107780,
JP-A-3-215677 and JP-A-4-314
No. 871 discloses the use of thiosulfuric acid as a complexing agent for gold.

[0006]

In the case where a cyanide compound is used in displacement gold plating, the cyanide is highly toxic even in a very small amount, as is known by the name of potassium cyanide. Must be paid, which is not preferable as a working environment.

[0007] In addition, the conventional plating method which uses substitutional gold plating and does not use cyan has a weak ability to block metals other than gold in the plating solution, for example, copper and iron, and has low stability of the solution. Also, the adhesion between the deposited plating and nickel as the base metal is low.

Further, in the conventional reduced gold plating, a liquid stabilizer is used or the composition ratio of the liquid is adjusted so that the reaction with the reducing agent is performed only in the presence of the object to be plated. Must.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a non-cyanide-substituted gold plating solution having low toxicity without using a cyanide compound and having the same film properties as conventional cyan-based substitutional gold plating.

[0010]

The substituted gold plating solution of the present invention contains a non-cyanide gold source, a sulfite, and carboxylic acid or a salt thereof as a metal complexing agent , and contains ammonium ion as an impurity. Concentration is 0.02 mol / l or less, chloride ion concentration is 0.3 mol / l or less, sulfate ion concentration is 0.3 mol / l or less, bromine ion concentration is 0.03 mol / l or less, or iodine ion concentration Is 0.006 mol / l or less.

The non-cyanide gold source used in the present invention includes gold sodium sulfite, potassium gold sulfite, gold ammonium sulfite, chloroauric acid, sodium chloroaurate, potassium chloroaurate, sodium iodoaurate, and bromideaurate. One or more gold compounds that do not use a cyanide compound such as potassium can be used. The concentration of this non-cyanide gold source is 0.5 g /
and preferably 1 to 10 g / l. When the concentration is lower than 0.5 g / l, the substitution reaction rate is decreased. When the concentration is higher than 10 g / l, it is not economical, and impurities such as ammonium ion, chlorine ion, bromine ion and iodine ion increase, as described later. In addition, the characteristics as a plating solution are deteriorated.

Above all, it is preferable to use sodium gold sulfite or potassium gold sulfite which do not contain the above impurities. When other gold compounds are used, the ammonium ion concentration is 0.02 mol / l or less and the chlorine ion concentration Is 0.3 mol / l or less, and the bromine ion concentration is 0.1 mol / l.
03 mol / l or less, or an iodine ion concentration of 0.00
The plating solution must be adjusted so as to be 6 mol / l or less. Ammonium ion concentration of 0.02 mol /
1, the chloride ion concentration is 0.3 mol / l, the sulfate ion concentration is 0.3 mol / l, and the bromine ion concentration is 0.03 mol / l.
If the l or iodine ion concentration exceeds 0.006 mol / l, the plating solution may become unstable or self-decompose, and the adhesion to the base nickel may be reduced and the appearance of the plating film may be deteriorated. Sometimes. These impurity ions may be due to other components of the plating solution, and are preferably adjusted so as not to exceed the range shown here, in combination with the composition used for the non-cyanide gold source. Other compositions will be described below, but it is preferable that the other compositions do not include the impurity ions.

Carboxylic acid or a salt thereof as a metal complexing agent
The kind, salts of malonic acid and its, salts of oxalic acid and its, salts of glutaric acid and its, salts and its succinate, salts of and its maleic acid, salts of citraconic acid and its, and its itaconate possible salts, salts and its propionic acid, salts of and its formic acid, the use of those selected from salts of acetic acid and its. Carboxylic acid or its salt as the metal complexing agent
Preferably , the concentration of the class is in the range from 0.5 g / l to 100 g / l. If it is less than 0.5 g / l, the luster of the plating is lost, and the adhesion to the underlying metal, nickel or cobalt, may be reduced. If it exceeds 100 g / l, it loses gold luster and becomes brownish, which is not preferable.

The concentration of the sulfite is 7 g / l to 150 g / l
It is preferably in the range of l. If it is less than 7 g / l, the stability of the plating solution is lost, and if it exceeds 150 g / l, the substitution reaction is remarkably suppressed, and it is not economical and not preferable.

The displacement gold plating solution of the present invention has a pH of 5 to 5.
It is preferably in the range of 12, more preferably in the range of 6 to 11. If it is less than 5, sulfurous acid reacts with hydrogen ions, which are acids, to generate toxic sulfurous acid gas. If it exceeds 12, gold precipitates, but when the plating resist is used, the resist dissolves in the plating solution. It is not preferable because it cannot be used as a resist. Various acids and alkalis can be used to adjust the pH, but it is preferable not to increase the impurities. For example, it is preferable to use a sodium salt or a potassium salt rather than using an ammonium salt.

The working temperature of the displacement gold plating solution of the present invention is 3
The temperature is preferably 0 to 95 ° C., and nickel or cobalt is preferably used as a base metal for plating.

[0017]

According to the present invention, as a result of intensive studies, the present inventors have found that when non-cyanide gold source, sulfite, and carboxylic acid or its salts are used as metal complexing agents , Ion concentration of 0.02 mol / l or less, chloride ion concentration of 0.3 mol / l or less, sulfate ion concentration of 0.3 mol / l
Hereinafter, if the bromine ion concentration is 0.03 mol / l or less, or the iodine ion concentration is 0.006 mol / l or less,
It has been made based on the finding that it is possible to obtain plating properties equivalent to those of a conventional gold plating solution using a cyanide compound while reducing toxicity.

[0018]

[Example] Glass cloth-epoxy resin copper clad laminate MCL-E-67 (trade name, manufactured by Hitachi Chemical Co., Ltd.)
Unnecessary portions of the copper foil that do not form a circuit are removed by etching, washed with water to form a wiring pattern, immersed in an aqueous solution of 200 g / l ammonium persulfate for 90 seconds to roughen the surface of the wiring pattern, washed with water, and washed with 10% Immersed in sulfuric acid for 60 seconds, washed with water, immersed in Melplate Activator 350 (manufactured by Meltex Corporation, trade name), which is a catalyst for electroless nickel plating, for 5 minutes to apply the catalyst to the wiring pattern surface, and washed with water, 3 at 85 ° C on Blue Schumer (product name, manufactured by Nippon Kanigen Co., Ltd.)
After immersion for 0 minutes, the surface of the wiring pattern was plated with nickel, washed with water, and then subjected to displacement plating according to the composition and conditions shown in Table 1. Conditions not described in the table were adjusted using sodium hydroxide or hydrochloric acid so that the solution temperature was 85 ° C., the immersion time was 30 minutes, and the pH was 7.0. Plating area as one cycle 5 dm ² / l, was evaluated by continuously plating to 30dm ² / l. Table 1 shows the results.

[0019]

[Table 1]

[0020] As can be seen from the table, non-cyanide gold source, sulfites, and carboxylic acids as metal complexing agent of the present invention
Alternatively , those using salts thereof are excellent in plating appearance, adhesion and plating solution stability. On the contrary,
In Comparative Example 1, a carboxylic acid or a salt thereof was used as a metal complexing agent.
The appearance of the plating is poor because no metal is used. The reason for this is that, as a result of detailed analysis by ESCA, copper and nickel generated by the substitution reaction of gold are taken into the gold plating film, and therefore, a dense gold film is not formed. Further, Comparative Examples 2 to 6 have the same configuration as the present invention, but further contain ammonium ions, chloride ions, sulfate ions, bromine ions, or iodine ions, which are impurities, at a specific value or more. Yes, suppress the effect of metal complexing agent to improve plating appearance,
The appearance deteriorates. Furthermore, in Comparative Example 7, thiosulfuric acid as a gold complexing agent used in a conventional example of a gold plating solution not using cyan was used in place of the carboxylic acids of the present invention. It is understood that the adhesiveness is low and the characteristics are not sufficient when used for a printed wiring board or the like.

[0021]

As described above, according to the present invention, the toxicity is low, and the stability of plating solution, plating appearance, and adhesion to the underlying metal are low as in the case of conventional displacement gold plating using cyan. A non-cyanide gold plating solution having excellent plating film properties such as force can be provided.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-330333 (JP, A) JP-A-6-228761 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 18/00-18/54

Claims (5)

(57) [Claims] 1. A non-cyanide gold source, a sulfite, and a metal complexing agent.
As a carboxylic acid or a salt thereof, as an impurity,
The ammonium ion concentration is 0.02 mol / l or less, the chloride ion concentration is 0.3 mol / l or less, the sulfate ion concentration is 0.3 mol / l or less, and the bromine ion concentration is 0.03 mol / l.
l or less, or the iodine ion concentration is 0.006 mol / l
A displacement gold plating solution characterized by the following. 2. A carboxylic acid or a salt thereof as a metal complexing agent
S is, salts of malonic acid and its, salts of oxalic acid and its, salts of glutaric acid and its, salts and its succinate, and maleic acid
Their salts, salts of citraconic acid and its, salts of itaconic acid and its, salts and its propionic acid, salts of and its formic acid, acetic acid
Displacement gold plating solution according to claim 1, characterized in that the salts of and its those chosen. 3. A sulfite having a concentration of 7 g / l to 150 g / l.
The displacement gold plating solution according to claim 1 or 2, wherein the value is in the range of l. 4. A carboxylic acid or a salt thereof as a metal complexing agent
The replacement gold plating solution according to any one of claims 1 to 3 , wherein the concentration of the compound is in the range of 0.5 g / l to 100 g / l. 5. The replacement gold plating solution according to claim 1, wherein the pH is in the range of 5 to 12.