JP2589324B2 - Electroless gold plating method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for electroless gold plating on a metallized pattern on an insulator made of ceramic, glass or the like.

(Prior Art) In a package for a semiconductor device such as a pin grid array or a chip carrier, a conductor circuit portion such as a wiring portion is formed by a metallized pattern formed of a metallized layer and the like. Plating and gold plating are performed. The nickel plating and the gold plating are generally performed by electrolytic plating, and the metallized patterns are all formed into a short-circuited shape in order to secure conduction for plating.

Therefore, in a package for a semiconductor device such as a pin grid array or a chip carrier which is subjected to a plating process by electrolytic plating, unnecessary portions short-circuited due to plating of a conductive pattern are removed by grinding after plating, and the conductive circuit portion is removed. Etc. must be separated independently.

(Problems to be Solved by the Invention) As described above, in the case of the conventional electrolytic plating, since the conductive pattern must be formed in a short-circuited shape in advance, a space for forming the short-circuit pattern is required. In addition, there is a problem that extra paste is required to form a short-circuited conductive pattern, and that gold plating in a portion removed by grinding or the like in a later process is wasted.

As for gold plating, an electroless gold plating method has also been tried, but at present there is no suitable gold plating bath. A material satisfying the required heat resistance, die bonding property, and wire bonding property cannot be obtained.

Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to provide a semiconductor device package having sufficient heat resistance, die bonding property, and wire bonding property by an electroless gold plating method. An object of the present invention is to provide an electroless gold plating method capable of obtaining a package having the following.

(Means for Solving the Problems) The present invention has the following configuration to achieve the above object.

That is, in the electroless gold plating method of the metallized pattern provided on the surface of the insulator, after performing the replacement gold plating process on the metallized pattern, performing an annealing process and an acid process, and further performing the replacement gold plating process, Then, an electroless gold plating process is performed.

(Summary of the Invention) In the present invention, nickel plating and gold plating are performed by electroless nickel plating and electroless gold plating on a semiconductor device package provided with a metallized pattern. In the case of electroless gold plating, simply performing electroless gold plating after performing displacement gold plating can provide a semiconductor device package having sufficient heat resistance, die bonding property, and wire bonding property as described above. Therefore, in the present invention, a sample subjected to a predetermined treatment such as nickel plating is subjected to displacement gold plating, and then subjected to a heat treatment at 760 ° C. for 10 minutes in a hydrogen reducing atmosphere, and then immersed in nitric acid (1: 1). Thus, nickel excessively diffused on the surface of the sample is removed, and replacement gold plating and electroless gold plating are performed again.

Through these steps, a gold-plated semiconductor device package having good heat resistance, die bonding property, and wire bonding property can be obtained.

(Example) Hereinafter, an example in which the gold plating method of the present invention is applied to a pin grid array will be described.

The 64-pin pin grid array completed up to the lead pin brazing step was subjected to electroless gold nickel plating and electroless gold plating by the following steps.

Degreasing treatment (okite, 60 ° C, 5 minutes) → acid treatment (1:10 sulfuric acid, normal temperature 5 minutes) → activation treatment (palladium active solution, 65 ° C, 20 minutes) → acid treatment (1: 1 hydrochloric acid, normal temperature 30) Sec) → Electroless nickel plating (Ni-B process, 65 ℃, 20
Min) → displacement gold plating (IM-Gold: manufactured by Nippon Kojundo Chemical, 90 ℃, 30
Minutes) → Annealing treatment (hydrogen atmosphere, 760 ° C, 10 minutes) → Acid treatment (1: 1 nitric acid, normal temperature 5 minutes) → Displacement gold plating (IM-Gold, 90 ° C, 20 minutes) → Electroless gold plating (cyan 5.8 g / l potassium potassium cyanide, 1.3 g / l potassium cyanide, 45 g / l potassium hydroxide, 23.6 g / l dimethylamine borane, 2 ppm lead, 85 ° C, 2 hours) Has the effect of enhancing the adhesion of the gold plating layer,
The subsequent acid treatment with nitric acid is performed to expose a portion having a higher gold content on the surface of the substituted gold plating layer after annealing.

Hereinafter, Tables 1 and 2 show the results of comparing the heat resistance and the wire bonding property of each of the pin grid array plated with gold in the above-described process and the one obtained by simply performing electroless gold plating on the replacement gold plating.

Table 1 shows the heat resistance determined by the degree of discoloration of the gold plating when the sample was kept at 450 ° C.

In Table 1, the No. 1 sample was obtained by simply applying electroless gold plating after replacement gold plating, and the No. 2 sample was obtained by using the above-described replacement gold plating, annealing, acid treatment, replacement gold plating, and electroless gold plating. It was done. In the table, ○ indicates that the gold plating did not change color within the designated time, X indicates that the color changed, Δ
The mark indicates a slightly discolored one.

From the results shown in Table 1, the gold plating obtained by performing the above-described substitutional gold plating, annealing treatment, acid treatment, and substitutional gold plating before the electroless gold plating is stable against heating. It can be seen that the heat resistance is much improved as compared with the heat treatment.

Table 2 shows the above No. 1 and No. 2 with wire bonding.
For each of 50 samples, the number of peeled wires after aging treatment at 200 ° C. for 60 hours was examined.

Table 2 shows that no wire peeling was observed even after aging for the No. 2 sample that had been subjected to the acid treatment, displacement gold plating, and electroless gold plating after the annealing treatment. A remarkable improvement in the wire bonding property was observed.

Next, Tables 3 and 4 show the results of similar tests performed on a 44-pin chip carrier. In Tables 3 and 4, the sample of No. 3 was subjected to displacement gold plating and electroless gold plating, and the sample of No. 4 was completely the same as the process of processing the sample of No. 2 in the above-mentioned pin grid array. The gold plating was performed in the same processing step. Here, since the electroless gold plating method is used, a chip carrier divided into individual chip carriers is used.

The number of samples used for testing the wire bonding property was 30, and the aging conditions were 200 ° C. and 60 hours.

From these results, it can be seen that the heat resistance and the wire bonding property of the chip carrier which has been subjected to the acid treatment, the substitutional gold plating and the electroless gold plating after the annealing treatment are extremely improved.

As can be seen from the above results, the heat resistance and the wire bonding property of the gold plating could be significantly improved by performing the annealing treatment, the acid treatment and the like at the time of the gold plating. As for the die bonding property, the same good properties as the wire bonding property were obtained. As a result, by using the electroless gold plating method, it is possible to obtain a product that sufficiently satisfies the conditions required for the semiconductor package.

(Effects of the Invention) According to the electroless gold plating method of the present invention, as described above, after performing substitutional gold plating, annealing treatment and acid treatment are performed to stabilize the substitutional gold plating.
By performing electroless gold plating after performing displacement gold plating, a gold plating film having excellent heat resistance, die bonding property, and wire bonding property can be obtained. A highly reliable semiconductor device package that satisfies the die bonding property and the wire bonding property can be provided.

In addition, since these semiconductor device packages are obtained by electroless plating, there is no need to provide a short-circuit portion for plating on the metallized pattern, which is advantageous in that the space can be effectively utilized, and is removed by metallizing paste and grinding. This saves the amount of gold plating to be performed and eliminates the need for a grinding step for separating metallized patterns independently.

As described above, the present invention has been described variously with reference to the preferred embodiments. However, the present invention is not limited to these embodiments, and it goes without saying that many modifications can be made without departing from the spirit of the invention. That is.

Claims (1)

(57) [Claims] In a method of electroless gold plating of a metallized pattern provided on the surface of an insulator, after the metallized pattern is subjected to substitutional gold plating, an annealing treatment and an acid treatment are performed, and then the substitutional gold plating treatment is performed again. And then performing an electroless gold plating process.