JPS6220878A - Electroless nickel plating solution - Google Patents

Abstract

PURPOSE:To obtain the titled plating soln. having superior stability and a high rate of deposition by adding specified amount of copper ions to an electroless nickel plating soln. contg. a soluble nickel salt, a hypophosphite and a pH buffer as essential components. CONSTITUTION:This plating soln. having superior stability is obtd. by adding 0.1-4ppm copper ions to an electroless nickel plating soln. contg. about 10-60g/l soluble nickel salt such as nickel sulfate, about 10-30g/l hypophosphite such as sodium hypophosphite and about 1-50g/l pH buffer such as acetic acid as essential components. When plating is carried out with the resulting plating soln. while the soln. is kept at about 6-4 pH and about 50-30 deg.C, a thin nickel film can be uniformly formed on the surface of plastics or glass without requiring surface roughening.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an electroless nickel plating solution for forming a nickel film on an insulating material such as glass or plastic, and particularly relates to a uniform Ni-Nokel film. The present invention relates to an electroless nickel plating solution composition that is flexible and has excellent solution stability.

(Prior art) Generally, the plating solution used for electroless Ni-Kel plating consists of soluble 2.7 Kel salt, hypophosphite, and pH buffer solution as main components. It can be used by increasing the precipitation rate by heating it. In order to prevent decomposition of the plating solution and obtain a dense plating layer, it is effective to subject the plating solution to acidic conditions.

However, if the plating solution is placed under acidic conditions, the deposition rate decreases and the deposition does not start uniformly, making it impossible to form a plating layer with no uneven plating.

This becomes a serious problem especially when a thin mesh layer of about 1,000 to 2,000 A is uniformly formed.

In particular, when di-Sokel chloride is used as the soluble di-7 Kel salt, a uniform nickel coating can be obtained from the initial stage of plating, but when nickel sulfate is used, a uniform nickel coating cannot be obtained. The reason for this is unknown, but the special grade reagent nickel sulfate used contains about 2 ppm or more of Co, which is thought to have an adverse effect on the formation of a uniform nickel film.

That is, the impurity concentration (ppm) in the bath prepared from nickel sulfate and nickel chloride is as follows as a result of atomic absorption spectrometry.

A nickel sulfate bath is preferable because it has better stability than a nickel chloride bath, but due to the presence of impurity Co, a uniform plating layer cannot be formed from the time of bath preparation when a nickel sulfate bath is used. . That is, 2.8p of CO
In the case of a sulfuric acid di-Sokel bath containing 100 pm, only 15 to 20 layers of the plated area can be electrolessly plated at the time of bath construction, and the CO is consumed by repeating the plating 20 times, and the Co content becomes 0. 8 ppm or less, electroless plating could only be performed on 90% of the coating area, which was uneconomical.

(Objectives of the Invention) Therefore, one object of the present invention is to provide an electroless nickel plating solution that has excellent solution stability, a high deposition rate, and is capable of uniformly starting deposition.

A further object of the present invention is to enable use of nickel sulfate with a high Co content in electroless nickel plating.

(Structure of the Invention) The electroless nickel plating solution according to the present invention mainly contains a soluble nickel salt, hypophosphite, and a pH buffer, and contains 0.1 to 4 ppm of copper ions in the plating solution. It is characterized by the addition of

As the soluble nickel salt, inorganic salts such as sulfates, hydrochlorides, nitrates, etc. are generally used. The above-mentioned hypophosphite is a reducing agent, and sodium salt is generally used. above p
Organic acids such as acetic acid, citric acid, and co-phosphoric acid and/or their salts and ammonium salts of inorganic acids such as sulfuric acid and hydrochloric acid are used as buffering agents, and lactic acid and boric acid are used as pH adjusters. etc. are used.

In the present invention, in order to maintain liquid stability, prevent environmental pollution due to evaporation of the bath liquid, and prevent alkaline corrosion of the material to be plated, the pH of the bath is maintained at an acidic condition, for example, pH = 6 to 4, and the bottom temperature is relatively low. For example, it is preferable to carry out at 60°C or lower, preferably 50 to 30°C. In this respect, the present invention is essentially different from conventional plating methods.

Soluble nickel to which the present invention can be applied naturally includes nickel chloride, but it is effective to apply the present invention to nickel sulfate with a high Co content.

The amount of the above nickel salt is 10 to 10% in terms of metal salt per 1 ton of bath.
60? /l, preferably from 20 to 509/l, and hypophosphite from 10 to 3 oy/l, preferably from 15 to 20
? /l, and the pH buffer is the amount necessary to stabilize the bath at a predetermined pH, generally 1 to 50? /l.

The feature of the present invention is that a trace amount of copper ions is added to the conventional plating solution whose main components are the above-mentioned nickel salt, phosphite, and pH buffer, and the amount of copper ions added is 0.1 to 1.
4 ppm, preferably 0.1 to 3 ppm. This amount is 0. If it is less than 1 ppm, a uniform plating layer will not be formed, and if it exceeds 4 ppm, a uniform adhesion layer will not be obtained.

The electroless nickel plating solution of the present invention can generally be used to form a thin nickel film on the surface of plastic or glass that has not been subjected to surface roughening treatment such as etching treatment. In carrying out electroless nickel plating, commonly used pretreatment steps are carried out: sensitization, water washing, activation, and water washing. Sensitization is generally carried out by immersion in an aqueous solution of a volatile metal salt, such as stannous chloride and hydrochloric acid. Activation is also carried out by immersion in an aqueous solution of a noble metal salt, such as palladium chloride and hydrochloric acid. When performing electroless plating using the electroless plating solution according to the present invention on a nonconductor plated material that has been subjected to these pretreatments, it is preferable to perform electroless plating while stirring the bath.

The present invention will be explained below using examples.

Example An acrylic test piece (76 x 26 x 1,5 mm) was immersed in a known degreasing solution manufactured by Okuno Pharmaceutical Co., Ltd. at room temperature for 5 minutes, and after washing, it was washed with a sensitizing solution (based on Sn ctt and HcL, manufactured by Okuno Pharmaceutical Co., Ltd.). After soaking for 1 minute and washing.

Pretreatment was performed by immersing it in an activation solution (based on pd C2* and Hct, manufactured by Okuno Pharmaceutical Co., Ltd.) for 1 minute and washing it.

Next, a plating bath (-I) with the following composition was prepared: Nickel sulfate (using special grade reagent) 269/L Sodium hypophosphite
21 Ammonium chloride
3 tt Sodium acetate 5
〃Boric acid 12〃
pH 5.5 The impurity metal content of this bath solution immediately after bath preparation was as follows as a result of atomic absorption spectrometry: Fe below the detection limit (0.0 ppm) Zn O, 1 ppm Co 2.8 // Cu Below the detection limit After adding Cu in the form of Cu cm to this plating bath (I) at the concentration shown in Table 1, while stirring with a stirrer,
The above acrylic test piece was heated at 5°C while maintaining the bath temperature at 3°C.
Soaked for minutes. The thickness of the obtained electroless nickel plating film was 1,200-1.50 OA.

The results are shown in Table 1.

The plating efficiency and uniformity in Table 1 are based on the following evaluation method: 1) Plating efficiency Deposition rate without adding each additive ion (film thickness 400
Relative value when ~500λ) is set as 100 2) Uniformity Acrylic test piece (76 x 26
The ratio of the area of the plating formation layer to the total surface area of - As an example, Figure 1 shows the surface condition of an acrylic test piece when the amount added in Table 1 is 0, and the uniformity in this case is 20. ．．
This is a diagram for the case of 1st section, and the uniformity is 100chi.

Table 1 As can be seen from Table 1, the addition of Cu ions according to the present invention greatly improves the properties of the electroless coating, making it possible to obtain a uniform plating film immediately after bath preparation.

Furthermore, in order to investigate the relationship between the effect of Cu ions of the present invention and CO ion concentration, C was added at the time of bath preparation.

When the same experiment as above was carried out by adding ctt to increase the CO concentration, it was possible to achieve a uniformity of 100 cm during bath preparation by adding Cu ions of the present invention until the CO concentration was about 8 ppm.

In addition, in order to investigate the reason for the effect of adding Cu ions according to the present invention, Ag whose ionization series is lower than Cu was
It was added in the form of 1O in place of CuO, but it had little effect.

[Brief explanation of drawings]

Figures 11 and 2 are examples of the uniformity evaluation method shown in Table 1, and Figure 1 is a reproduction of a photograph showing the state of the electroless nickel surface when no Cu ions are added using the conventional method. Ha・
The Sochi portion represents the plating layer, and the uniformity in this case is 20 inches. FIG. 2 is a diagram similar to FIG. 1 in the case of adding Cu ions according to the present invention, and the uniformity in this case is 100 mm. Patent applicant: Daicel Chemical Industries, Ltd. Figure 1
Figure 2

Claims (1)

[Claims] 1) An electroless nickel plating solution containing a soluble nickel salt, hypophosphite, and a pH buffer as main components,
An electroless nickel plating solution characterized in that 0.1 to 4 ppm of copper ions are added to the plating solution. 2) The plating solution according to claim 1, wherein the pH is in an acidic range. 3) The plating solution according to claim 1 or 2, wherein the bath temperature is 60° C. or lower. 4) The plating solution according to any one of claims 1 to 3, wherein the soluble nickel salt is nickel sulfate.