JPH0699831B2 - Sn-Ni alloy or Sn-Co alloy plating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a Sn-Ni alloy or Sn-Co alloy plating method capable of stably obtaining Sn-Ni alloy or Sn-Co alloy plating.

<Prior art> Sn-Ni alloy plating or Sn-Co alloy plating is decorative and has excellent corrosion resistance, so it requires corrosion resistance and chemical resistance such as friction parts of various electric appliances and audio equipment. It is widely used in parts where

Generally, Sn-Ni alloy plating or Sn-Co alloy plating is obtained from a fluoride bath or pyrophosphoric acid bath, and in particular, the same number of Sn and Ni or Sn and Co can be electrodeposited from the fluoride bath at the same time. Therefore, the composition of the obtained plated alloy is Sn: 67 wt% and Ni: 33 wt% in the case of Sn-Ni alloy plating due to the relation of atomic weight. It is said that this Sn-Ni alloy plating layer is electrodeposited in a quasi-stable phase represented by the chemical formula NiSn of plating. This metastable phase has the property of exhibiting excellent corrosion resistance and discoloration resistance. Here, the Sn-Ni alloy and the Sn-Co alloy can be obtained from almost the same bath composition, so the Sn-Ni alloy plating will be representatively described below.

Table 1 shows the bath composition of a typical fluoride bath among the Sn-Ni alloy plating baths.

From the plating baths A, B and C shown in Table 1, the alloy composition of Sn: 67 wt% and Ni: 33 wt% (Sn: Ni atomic ratio = 1: 1) as described above can be obtained. This is because the Sn ions are complexed in the fluoride bath and the electrode potentials of Sn and Ni are close to each other, so that a plating layer having a stable composition can be obtained. And with Sn
Since the electrode potential of Ni does not approach unless the bath temperature is 50 ° C or higher, plating is generally performed at a bath temperature of 60 ° C or higher.

Thus, Sn-Ni alloy plating obtained from the fluoride bath consists of an approximation of the electrode potentials of both metals due to the complexing action, so that the inclusion of a trace amount of organic matter, especially a surfactant, may cause the electrode potential, especially Ni. Strongly influences the deposition potential of.
Therefore, the addition of brighteners to the bath is difficult and not usually done.

By the way, pure Sn plating using an acid bath or an alkaline bath, or Sn-containing Sn such as Sn-Zn, Sn-Cu, Sn-Pb
When performing system alloy plating, Sn present in the plating solution
The fluctuation of the valence of Sn ions due to the oxidation of ions becomes a problem.

This also applies to the Sn-Ni alloy plating bath made of fluoride. That is, in an acidic plating solution, divalent Sn comes into contact with air and is oxidized to form tetravalent Sn.
Ions are deposited from divalent Sn on the object to be plated, and tetravalent
Since it does not precipitate from Sn ions, tetravalent Sn is an unnecessary existence, and when tetravalent Sn increases in the bath, fluoride is consumed and the fluoride in the plating solution becomes insufficient, resulting in plating. Inhibits bath stability.

Therefore, in order to suppress the oxidation of Sn (increasing the amount of tetravalent Sn) in the plating bath, in acidic Sn plating baths, in general, the stirring of the plating solution is suppressed as much as possible and the circulation of the plating solution is reduced. However, in the case of Sn-Ni alloy plating, since the bath temperature is as high as 60 ° C or higher as described above, the oxidation of Sn tends to be promoted, and Sn plating or other Sn-based alloy plating Compared with the case of oxidized Sn in the bath
At present, it is difficult to reduce the amount.

<Problems to be Solved by the Invention> An object of the present invention is to solve the above-mentioned drawbacks of the prior art by using Sn.
An object of the present invention is to provide a Sn-Ni alloy or Sn-Co alloy plating method capable of significantly improving the stability of a -Ni alloy or Sn-Co alloy plating bath.

<Means for Solving Problems> In Sn-Ni alloy or Sn-Co alloy plating, as described above, it has been found that when tetravalent Sn increases in the plating solution, the stability of the plating bath is hindered. However, as a result of further studies, the present inventors have found that when the amount of tetravalent Sn in the plating solution is large, the corrosion resistance of the plating decreases.

Therefore, in the Sn-Ni alloy or Sn-Co alloy plating solution,
As a result of extensive studies on a method for preventing Sn from being oxidized to tetravalent Sn, it was found that at least one of hydroquinone and pyrocatechol was added as a predetermined reducing agent to the plating solution. Came to.

That is, the present invention, Sn-Ni alloy or Sn-Co alloy plating bath,
The present invention provides a Sn-Ni alloy or Sn-Co alloy plating method, characterized in that at least one salt of hydroquinone and porocatechol is added for plating.

Hereinafter, the Sn-Ni alloy or Sn-Co alloy plating method of the present invention will be described in detail. In addition, Sn-Ni alloy plating and Sn-Co
Since the properties of the alloy plating are similar to those of the alloy plating, Sn-Ni alloy plating will be representatively described below unless otherwise specified.

The plating bath in the present invention may be a fluoride bath, a borofluoride bath, a pyrophosphoric acid bath, or the like.

The reducing agent added to the plating bath is at least one of hydroquinone and pyrocatechol. By adding these reducing agents, divalent Sn in the plating solution can be prevented from becoming tetravalent Sn.

The total amount of the reducing agent added is preferably about 0.01 to 1 g / l. The reason is that if it is less than 0.01 g / l, the antioxidant effect of divalent Sn will be insufficient, and if it exceeds 1 g / l, the quality of the alloy plating film due to organic matter will be deteriorated. The reducing agent may be replenished at any time with the progress of plating.

In addition, as the object to be plated to which the method of the present invention is applied,
Copper, copper-based alloys (C151, C505, etc.), iron, iron-based alloys (stainless steel, 42 alloys, etc.), or composite materials of these (for example,
Cu / 42 alloy clad material), and the form thereof may be any material such as a plate material, a strip material, a pipe material, and a long strip.

The form of plating according to the present invention may be either electrolytic plating or electroless plating.

<Example> (Experiment 1) In the bath A shown in Table 1, hydrazine hydrate was added as a reducing agent in an amount of 0.
Add at a concentration of 3g / l, bath temperature 60 ℃, pH = 2.5, current density 1A /
A copper plate was continuously electroplated with a Sn—Ni alloy having a thickness of 2 μm under conditions of dm ² and a current of 15 A. 200 during plating
Replenishment of 0.2 g / l hydrazine hydrate (reducing agent) was performed every time.

On the other hand, as a conventional method, Sn-Ni alloy electroplating was performed under the same conditions as above except that no reducing agent was added to the bath A.

With respect to each of these plating solutions, the total Sn concentration and the Sn ^{4 +} concentration in the plating solution were measured after a predetermined time, and the ratio of the Sn ^{4 +} amount in the total Sn amount was obtained. The results are shown in Table 2.

In this case, at any time the divalent value in the plating solution
Sn concentration in the range of 12~30g / l, Ni ^{+ +} concentrations 60~80g / l
Adjusted to fall within the range.

The Sn-Ni obtained at each time-lapse step thus obtained
The corrosion resistance of the alloy plating was investigated. The method is to boil 6N hydrochloric acid, immerse each test piece in the boiling liquid, and Sn-Ni
The evaluation was performed by the time until the alloy plating layer was melted and the copper substrate was exposed. The results are shown in Table 2.

The corrosion resistance was judged as the one having a longer dissolution time of the Sn-Ni alloy plating layer was more excellent in corrosion resistance, and was classified into ◯: 10 minutes or more, Δ: 6 minutes or more and less than 10 minutes, and ×: less than 6 minutes.

As can be seen from the results in Table 2, in the present experiment in which the reducing agent (hydrazine hydrate) was added to the Sn-Ni alloy plating solution, the oxidation reaction of divalent Sn to tetravalent Sn in the plating solution was remarkable. It was confirmed that the life of the plating solution was suppressed (extended by 4 times or more), and as a result, the corrosion resistance of the Sn-Ni alloy plating was stable and good.

(Experiment 2-Example 1 of the present invention) Sn-Ni alloy electroplating was carried out under the same conditions as in Experiment 1 except that the reducing agents added to the plating solution were changed to
By the same method, the ratio of Sn ^{4 +} content in the plating solution and the corrosion resistance of Sn-Ni alloy plating were investigated.

Hydroquinone (addition amount: 0.2 g / l) Pyrocatechol (addition amount: 0.2 g / l) When any of the above reducing agents (1) to (4) was added, the same results as those in Table 2 were obtained.

(Experiment 3) Hydrazine hydrate was added as a reducing agent to the plating bath D having the following composition.
Add at a concentration of 0.3g / l, bath temperature 60 ℃, pH = 2.5, current density 1
A copper plate was continuously electroplated with a thickness of 2 μm of Sn—Co alloy under the condition of A / dm ² . Every 200 hours during continuous plating
Replenishment of 0.2 g / l hydrazine hydrate (reducing agent) was performed.

[Plating bath D]

Stannous chloride _{(SnCl 2 .2H 2 O):} 50g / l of cobalt chloride _{(CoCl 2 .6H 2 O):} 300g / l sodium fluoride (NaF): 28g / l ammonium bifluoride (NH ₄ F · HF ): 35 g / l On the other hand, as a conventional method, Sn-Co alloy electroplating was performed under the same conditions as above except that no reducing agent was added to the D bath.

In the same manner as in Experiment 1, the Sn ^{4 +} amount ratio and Sn in the plating solution
-The corrosion resistance of Co alloy plating was investigated. However, the same results as those in Table 2 were obtained.

(Experiment 4-Example 2 of the present invention) Sn-Co alloy electroplating was performed under the same conditions as in Experiment 3 except that the reducing agents added to the plating solution were changed to
By the same method, the ratio of Sn ^{4 +} amount in the plating solution and the corrosion resistance of Sn-Co alloy plating were investigated.

Hydroquinone (addition amount: 0.2 g / l) Pyrocatechol (addition amount: 0.2 g / l) When any of the above reducing agents (1) to (4) was added, the same results as those in Table 2 were obtained.

<Effects of the Invention> According to the Sn-Ni alloy or Sn-Co alloy plating method of the present invention, by adding a predetermined reducing agent to the plating solution,
The divalent Sn present in the plating solution was suppressed from changing to tetravalent Sn, so that stable plating could be performed, and further, the life of the plating solution could be significantly extended and obtained. The corrosion resistance of plating is significantly improved.

As a result, the consumption of the plating solution is saved, the plating cost can be reduced, and the quality of the product plated with Sn-Ni alloy or Sn-Co alloy is improved.

Claims (1)

[Claims] 1. At least one of hydroquinone and pyrocatechol in a Sn-Ni alloy or Sn-Co alloy plating bath.
Sn-Ni characterized by adding various kinds of salts for plating
Alloy or Sn-Co alloy plating method.