JPH05287541A - Substitution gold plating liquid - Google Patents

Abstract

PURPOSE:To form a gold layer exhibiting good adhesion to a nickel layer by adding a buffer consisting of alkali hydrogen phthalate and alkali hydroxide to a substitution gold plating liquid. CONSTITUTION:The substitution gold plating liquid is prepd. by adding potassium cyanide to a buffer soln. which is added with the water soluble buffer consisting of the alkali hydrogen phthalate, such as potassium hydrogen phthalate and the alkali hydroxide, such as potassium hydroxide, and is adjusted to 4 to 7. The water soluble buffer consisting of water soluble amino acid, alkali chloride and hydrochloric acid is otherwise added to the buffer soln. and its pH is adjusted to 4 to 7. The nickel layer formed on parts consisting of a nonconductive material is subjected to an annealing treatment, and thereafter, the substitution gold plating liquid is applied thereon by using this substitution gold plating liquid, by which the dense gold layer exhibiting the good adhesion to the nickel layer is formed.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a displacement gold plating solution,
More specifically, the present invention relates to a displacement gold plating solution capable of forming a gold layer which is dense and has good adhesion to a base plating layer by displacement gold plating.

[0002]

2. Description of the Related Art Conventionally, a gold layer having excellent conductivity and being chemically stable is formed by plating on terminals of electronic parts such as semiconductor devices and connectors. When gold plating is applied to such electronic parts and connectors, nickel plating (Ni-P or N) having good corrosion resistance and high hardness is usually used.
After i-B) is applied as a base plating, gold plating is applied. When such gold plating is applied, displacement gold plating is applied to the upper surface of the nickel layer formed by undercoating, as described in US Pat. No. 3,162,512. By the way, electroless nickel plating is adopted to form a nickel layer on an electronic component made of a non-conductive material such as plastic or ceramic by plating.

[0003]

By such electroless nickel plating, it is possible to apply nickel plating to electronic parts and the like made of a non-conductive material. However, when gold plating is applied to the upper surface of the nickel layer formed by electroless nickel plating, nickel forming the nickel layer diffuses into the gold layer. The diffusion of nickel into the gold layer is performed by annealing the nickel layer formed by electroless nickel plating, as previously proposed by one of the present inventors in Japanese Patent Application No. 62-268406. After that, it can be suppressed by performing displacement gold plating. However,
It was found that the gold layer obtained by subjecting the nickel layer to the annealing treatment and then the displacement gold plating was rough and had low adhesion to the nickel layer. Therefore, an object of the present invention is to perform a annealing treatment on a nickel layer formed by electroless nickel plating, and then form a dense gold layer exhibiting good adhesion to the nickel layer by displacement gold plating. To provide a displacement gold plating solution.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, by using a buffer solution that suppresses elution and oxidation of nickel underlayer, it is possible to perform precise and underlayer plating. On the other hand, they have found that a gold layer exhibiting good adhesion can be formed, and have reached the present invention. That is, according to the present invention, potassium gold cyanide is added to a buffer solution having a pH value adjusted to 4 to 7 by adding a water-soluble buffering agent consisting of alkali hydrogen phthalate and alkali hydroxide. It is a characteristic displacement gold plating solution. Further, the present invention is
Displacement gold plating solution, wherein potassium cyanide is added to a buffer solution having a pH value adjusted to 4 to 7 by adding a water-soluble buffering agent comprising water-soluble amino acid, alkali chloride and hydrochloric acid But also. In the present invention having such a constitution, the water-soluble buffering agent composed of potassium hydrogen phthalate and potassium hydroxide can be preferably used as a displacement gold plating solution for a semiconductor device. Furthermore, when the water-soluble amino acid is glycine, the cost required for the displacement gold plating can be reduced. In addition, the addition of a chelating agent such as ethylenediaminetetraacetic acid (EDTA) to the plating solution can complex a metal such as nickel that is eluted in the displacement plating solution and prolong the life of the displacement plating solution. it can.

[0005]

According to the present invention, as shown in Examples described later,
After the nickel layer formed by the displacement nickel plating is annealed, the displacement gold plating solution of the present invention is used to perform the displacement gold plating to provide a dense and good adhesion to the nickel layer. A gold layer can be formed.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The displacement plating solution of the present invention is a displacement plating solution to which a water-soluble buffering agent consisting of an alkali hydrogen phthalate and an alkali hydroxide is added. As the alkali hydrogen phthalate and the alkali hydroxide used as such a water-soluble buffer, any compound can be adopted as long as it is water-soluble, but a sodium compound or a potassium compound is preferable.
In particular, when a buffer composed of potassium hydrogen phthalate and potassium hydroxide is used as the buffer, it can be preferably used when performing displacement gold plating on the semiconductor device. The displacement plating solution of the present invention has a pH value of 4 to 4 with the addition of such a buffering agent.
The potassium gold cyanide is added to the buffer solution maintained at 7. If the pH value of the buffer solution is less than 4 or more than 7, it becomes difficult to form a dense gold layer having improved adhesion to the electroless nickel layer by displacement gold plating.

In the present invention, instead of the water-soluble buffering agent composed of alkali hydrogen phthalate and alkali hydroxide, a water-soluble buffering agent composed of a water-soluble amino acid, alkali chloride and hydrochloric acid may be used. Here, it is preferable to use glycine as the water-soluble amino acid because the cost of the displacement plating solution can be reduced. Further, NaCl can be preferably used as the alkali chloride. The displacement plating solution of the present invention also includes ethylenediaminetetraacetic acid (EDTA).
When a chelating agent such as is added, the metal such as nickel eluted during the displacement plating can be complexed, so that the life of the displacement plating solution can be extended. As this chelating agent,
In addition to EDTA, CyDTA, DTPA, EDTA-O
Mention may be made of H, GEDTA, TTHA and their alkali metal salts. The amount of these chelating agents added is preferably 0.1 to 100 g / liter.

The displacement plating solution of the present invention is used for electroless nickel plating on a member to be plated such as a package used in a semiconductor device made of a non-conductive material such as plastic or ceramic, and then a gold layer of nickel. One of the inventors of the present invention first disclosed in Japanese Patent Application No. 62-268
As proposed in Japanese Patent No. 406, it can be suitably used when further performing displacement gold plating on the annealed nickel layer. As the displacement gold plating conditions at this time, usual plating conditions can be adopted, and the displacement gold plating can be performed by immersing the member to be plated in a plating solution at 90 ° C. for 3 to 30 minutes. The member to be plated that has been subjected to the displacement gold plating may be further subjected to electroless gold plating to thicken the gold layer. The gold layer thus formed on the member to be plated is dense and has good adhesion to the nickel layer. The displacement plating solution of the present invention can be used not only for members such as packages used in semiconductor devices but also for gold plating of terminal portions such as connectors. When applying gold plating to connectors, etc., use a water-soluble buffer consisting of sodium hydrogen phthalate and sodium hydroxide as the water-soluble buffer consisting of alkali hydrogen phthalate and alkali hydroxide. You can also

[0009]

EXAMPLES The present invention will be described in more detail with reference to Examples. Example 1 A commercially available electroless nickel plating solution (manufactured by Uemura Kogyo Co., Ltd.) was used for a ceramic package to form a nickel layer having a thickness of 40 mμ. Then, the ceramic package on which the nickel layer is formed is annealed at 760 ° C. for 10 minutes in a reducing atmosphere, and then placed in a displacement gold plating solution at 90 ° C. for 4 minutes.
Substitution gold plating was performed by immersion for a minute. The displacement gold plating solution used at this time uses a water-soluble buffer consisting of potassium hydrogen phthalate and sodium hydroxide and has a pH value of 5.
In the buffer solution adjusted to 5, 1.5 g of potassium gold cyanide
/ Liter is added. The amount of potassium hydrogen phthalate added was 40.8 g / liter, and the amount of sodium hydroxide added was 4.0 g / liter. As a result of visual observation of the surface of the ceramic package plated with the displacement gold as described above, a dense displacement gold plating layer was formed. In addition, when scratches were formed on the ceramic package surface with a wire brush and the scratched portion was observed under a microscope to observe the adhesion of the replacement gold plating layer to the nickel layer, peeling of the replacement gold plating layer was observed. There wasn't.

Example 2 In Example 1, glycine 3 was used as the water-soluble buffer.
5.5 g / liter, NaCl 27.5 g / liter,
And a displacement plating solution prepared by adding potassium gold cyanide (1.5 g / liter) to a buffer solution in which 0.25 ml / liter of hydrochloric acid (0.1N) was added to adjust the pH value to 4.5. The displacement gold plating was performed in the same manner as in Example 1. Visual observation of the surface of the ceramic package plated with the displacement gold plating revealed that a dense displacement gold plating layer was formed. In addition, when scratches were formed on the ceramic package surface with a wire brush and the scratched portion was observed under a microscope to observe the adhesion of the replacement gold plating layer to the nickel layer, peeling of the replacement gold plating layer was observed. There wasn't.

Example 3 The displacement gold plating was performed in the same manner as in Example 1 except that 20 g / liter of EDTA.2Na as a chelating agent was added to the displacement gold plating solution. A dense substitutional gold plating layer is formed on the surface of the substitutional gold-plated ceramic package, and even in the adhesion test between the substitutional gold plating layer and the nickel layer by the wire brush on the ceramic package surface, No peeling was observed and it was good. Moreover, the displacement gold plating solution of this example was able to extend the life of the displacement gold plating solution as compared with the displacement gold plating solution of Example 1.

Comparative Example In Example 1, the substitution of the following composition described in US Pat. No. 3,162,512 as a substitution gold plating solution for forming a substitution gold plating layer exhibiting good adhesion to a nickel layer. The displacement gold plating was performed in the same manner as in Example 1 except that the gold plating solution was used. Composition of displacement gold plating solution Ammonium citrate 20 g / liter Potassium cyanide 5 g / liter EDTA.2Na 25 g / liter The displacement gold plating solution used in this comparative example was adjusted to a pH value of 6.0 to 6.5 with ammonia water. Has been done. Visual observation of the surface of the ceramic package plated with the displacement gold plating revealed that the formed displacement gold plating layer was rough. In addition, scratches were formed on the ceramic package surface with a wire brush, and the scratched portion was observed under a microscope to observe the adhesion of the replacement gold plating layer to the nickel layer. There were parts that were doing in places.

[0013]

According to the present invention, it is possible to form a gold plating layer, which is dense and has good adhesion to the undercoat, on an electronic component or the like made of a non-conductive material by displacement gold plating.

Claims (5)

[Claims] 1. Potassium cyanide is added to a buffer solution having a pH value adjusted to 4 to 7 by adding a water-soluble buffering agent comprising alkali hydrogen phthalate and alkali hydroxide. Replacement gold plating solution. 2. The displacement gold plating solution according to claim 1, wherein the water-soluble buffer comprises potassium hydrogen phthalate and potassium hydroxide. 3. A potassium gold cyanide is added to a buffer solution having a pH value adjusted to 4 to 7 by adding a water-soluble buffering agent comprising a water-soluble amino acid, alkali chloride and hydrochloric acid. Replacement gold plating solution. 4. The substituted gold plating solution according to claim 3, wherein the water-soluble amino acid is glycine. 5. A chelating agent such as ethylenediaminetetraacetic acid (EDTA) is added to the plating solution.
Alternatively, the displacement gold plating solution according to claim 3.