JPS58151487A - Tin electroplating bath made acidic with hydrochloric aicd - Google Patents

Abstract

PURPOSE:To provide a titled plating bath by which dense electrodeposited surfaces having good appearance are obtained under high-speed conditions, by adding an electrodeposited crystal control agent contg. alkylpyridinum salts and unsatd. carbonyl compds. in a basic plating soln. consisting esentially of stannous salt and hydrochloric acid. CONSTITUTION:An electrodeposited crystal control agent contg. alkylpyridinium salts such as laurylpyridinium chloride and unsatd. carbonyl compds. such as benzalacetone is added in a basic plating soln. consisting essentially of stannous salt such as stannous chloride and hydrochloric acid, whereby an acidic tin electroplating bath with hydrochloric acid which has low degrees of danger in operation, permits easy treatment of waste water, and by which dense and good electrodeposited surfaces are obtained without the formation of acicular crystals under high speed conditions such as high current density, high concn. of tin and high temp. is obtd. The laurylpyridinium chloride, etc. in the above- mentioned electrodeposited crystal control agent are enough at about 1-5g/l and the benzalacetone, etc. at about 0.01-0.1g/l in the acidic bath.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydrochloric acid electrotin plating bath, and more particularly to a hydrochloric acid electrotin plating bath that has a good appearance without forming needles under conditions of high current density, high tin concentration, high temperature and high speed. This invention relates to a hydrochloric acid acidic electrolytic tin plating bath that can provide a deposited surface.

Traditionally, tin plating baths have been limited to acidic baths such as sulfuric acid baths, borofluoride baths, or alkaline baths such as sodium stannate.
It has been mainly used for rack plating and barrel plating.

However, the tin salt that can be dissolved in these baths has a metal tin concentration of 30 to 40 g/(at most), which is the limit, and the high concentration necessary to obtain a high plating rate cannot be obtained. Use at high temperatures and -
However, in the acidic bath described in -, under high temperature and strong dq, divalent tin ions are oxidized to tetravalent tin ions, a precipitate is also formed, and the bath life is reached. On the other hand, in the case of an alkaline bath, reduction electrodeposition is performed from tetravalent tin ions, so even if plating is performed at the same current density, the plating speed is inevitably halved compared to an acidic bath, making it unsuitable as a high-speed bath. be. In addition, borofluoride baths can be used for special purposes.
Although it is said to have a high speed close to that of Dm, there are problems with worker safety and fluoride wastewater treatment, and it is highly corrosive to various materials, making it difficult to select materials for plating equipment. There are drawbacks.

In view of these drawbacks of conventional tin plating baths, the inventors
We decided to consider a hydrochloric acid bath, which is less dangerous during work and easier to treat wastewater. However, in the conventional hydrochloric acid acid bath, the electrodeposited surface was rough and acicular crystals were likely to form, and it was difficult to obtain an electrodeposited surface with a good appearance, so that it was not suitable for industrial use.

The purpose of the present invention is to provide a method with low operational risk, easy wastewater treatment, and the ability to obtain an electrodeposited surface that is dense and has a good appearance without forming needle crystals. The objective is to provide a hydrochloric acid acidic electrolytic tin plating bath that achieves this goal by adding an alkylpyridinium salt such as laurylpyridinium chloride to a basic plating solution containing stannous tin and hydrochloric acid as main components. This is due to the addition of an electrodeposition crystal regulator containing an unsaturated carbonyl compound such as benzalacetone.

In a hydrochloric acid bath, laurylpyridinium chloride has the effect of suppressing dendrite-like precipitation, and a sufficient effect is obtained in the range of 1 to 5 g/l. However, when performing high-speed flow plating with only laurylpyridinium chloride,
Only a blackish and rough surface can be obtained on the electrodeposited surface, and high speed cannot be achieved. Benzalacetone enables this high-speed flow plating, ranging from 0.01 g/l to 0.1 g/l
Performs sufficient leveling work within the range of .

Note that benzalacetone itself is insoluble in water, so
It is necessary to mix and dissolve it in a surfactant such as laurylpyridinium chloride before use.

A benzalacetone-free bath (Example 1) and a benzalacetone-added bath (Example 2) are shown below.

Example 1 Stannous chloride 70 g/L hydrochloric acid
0.5N hydrazine sulfate 10 g Laurylpyridinium tetrachloride 2 g //! jet flow velocity
A photograph of the plating surface condition in a bath of 3 m/B e is shown in FIG.

Example 2 Stannous chloride 70g/hydrochloric acid
0.5N hydrazine sulfate 10g/l laurylpyridinium chloride 2g/! benzalacetone
0.05g/l jet flow velocity 3'm/
Figure 2 shows a photograph of the plating surface condition of this bath.

As is clear from Figures 1 and 2, the plating surface of the benzalacetone-free bath is rough and rugged, but the plating surface of the benzalacetone-added bath is dense and smooth, giving it a good appearance. .

Hydrazine sulfate has the effect of stabilizing the bath at high temperatures (50°, 60°C or higher). In other words, at high temperatures, tin changes from divalent to tetravalent tin, lowering its specific gravity and impairing the adhesion of plating, but hydrazine sulfate acts as a reducing agent to reduce tetravalent tin to divalent tin. Therefore, the bath can be stabilized.

Concentrations of hydrazine sulfate ranging from 2 to 50'g/l are effective. In addition to hydrazine sulfate, reducing agents such as hydroquinone, hypophosphorous acid, and sulfite are also effective in stabilizing the bath, and these may be used alone or in combination.

Example 3 Stannous chloride 70g/l hydrochloric acid
0.5N hydrazine sulfate 10g/laurylpyraurylpyridinium chloride,,/l benzalacetone
0.05g//l Triton X-10
03'm/l jet flow velocity 3
m/sec However, Triton X-100 (trade name): E.

Liethylene glycol alkyl phenyl ether.

A photograph of the plating surface condition of this bath is shown in FIG. 3G.

Further, FIG. 4 shows photographs of the plating surface condition when the concentration of Triton X-100 is 1ml/g and 10m/g.

TRITON

Furthermore, Triton X-100 suppresses the rapid growth of crystals;
It also plays a role as a high-speed fL agent, and as shown in Table 1, the maximum current density range that provides a good plating surface changes depending on the presence or absence of additive IJ11.

Table 1 Example 4 Stannous chloride 70g/hydrochloric acid
0.5N Hydroquinone 5g/Laurylpyridinium Nochloride 2g/Nocinnamaldehyde
0.05g/.

Tween 80 3 ml/1 Jet flow rate 3 m/sec Bath temperature
. ,o.

Tween 80- (Product Name): (Polyoxyethylene Sorbitanmo This Example 6. Hey, 5 □ Actual m% 3 (!: @Yu.

7 plating speed and 2-ply appearance were obtained.

As described above, according to the present invention, by adding an electrodeposited crystal modifier such as laurylpyridinium chloride or benzalacetone, even in a hydrochloric acid acidic tin plating bath, where a rough appearance could not be obtained conventionally, smooth and line-deposited crystals can be obtained. It has the remarkable effect of being able to obtain a plated surface at high speed.

In addition, metal tin can be dissolved in a plating bath at a higher concentration than before (30 to 100 g/), and it can be used at high temperatures without oxidizing tin ions from divalent to tetravalent. By adding polyoxyethylene surfactants such as Triton 10-20 A/d at most
Considering that the plating time was m', the plating time can be shortened to 1/6 or less, and it is possible to incorporate the method into the same plating line as spot silver plating, which is performed in an extremely short time.

Furthermore, the present invention is applicable not only to high-speed flow plating equipment, but also to ordinary bath plating.
A high current density of about A/d'm can be adopted, and the plating time can also be shortened to 1/6 or less of the conventional plating time.

Although the present invention has been variously explained above with reference to preferred embodiments, the present invention is not limited to the above embodiments. For example, by adding other metal salts such as lead chloride and zinc chloride, these alloy baths It goes without saying that many modifications can be made without departing from the spirit of the invention, such as allowing it to function as a.

[Brief explanation of the drawing]

Figure 1 shows the bath without benzalacetone added, Figure 2 shows the bath with benzalacetone added, Figure 3 shows the bath with Triton X-100 added, and Figure 4 shows the bath with varying concentrations of Triton X-100. These are SEM photographs showing the plating surface condition in each case. Patent applicant Shinko Electric Industry Co., Ltd. Article 5, -, 2C\ q, ' q\゛, ゝ・n, \, Pemi\ Akuwa, ゞ1▗6゜3rd layer Ptsu0rvXo 8'7 times

Claims (1)

[Claims] 1o A deposited crystal modifier containing an alkylpyridinium salt such as laurylpyridinium chloride and an unsaturated carbonyl compound such as benzalacetone is added to a basic plating solution containing stannous salt and hydrochloric acid as main components. Hydrochloric acid acid electrolytic tin plating bath.