JPS5848689A - White copper-tin alloy plating bath - Google Patents

Abstract

PURPOSE:To obtain silver-gray lustrous thick plating by adding sodium thiocyanate, polyethyleneimine and a nickel salt other than chloride to a copper cyanide- alkali stannate type Cu-Sn alloy plating soln. CONSTITUTION:A copper cyanide-alkali stannate type Cu-Sn alloy plating soln. contg. sodium stannate, sodium cyanide, copper cyanide, sodium hydroxide, etc. is prepared. To the plating soln. are added sodium thiocyanate, polyethyleneimine and a nickel salt other than chloride such as nickel sulfate. Electrolysis is carried out in the resulting plating soln. under stirring with air at a prescribed current density using an insoluble plate as an anode. Thus, silver-gray lustrous thick plating is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to white steel - a tin alloy plating bath, and particularly white steel that can be silvery white and shiny and can be plated thickly.
This relates to a tin alloy plating bath.

Brighteners conventionally used in copper-tin alloy plating baths containing alkali pre-copper-stannate as main components include organic acids such as tartaric acid, citric acid, and salicylic acid, ethylene glycol, phenol, II-t phthol, and hydroxyl. hmm,
8-Hydroxyquinoline, phenols, ethylenetriamine, more adenine nitrogen compounds such as pyridine, quinolamine, triethanolamine, benzenesulfonic acid,! -F luenesulfonic acid, 2.7-
pe/zene sulfonate derivatives such as Naf I disulfonic acid, 2-mercaptobenzthiazole,
Sulfur-containing heterocyclic compounds such as 2-mercaptobenzimidazole, surfactants, and metal compounds such as silver, lead, bismuth, anti-silver, sulfur, and tellurium are known, but these Regarding white steel-tin alloy 911, both single additives and composite additives have problems such as a semi-gloss or matte finish and a narrow usable current density l[IiI. ),
Furthermore, even if gloss can be obtained over a fairly wide current density range, thick polishing tends to result in semi-gloss or matte polish, making thick polishing practically impossible. Based on the results of numerous experiments and research conducted in order to improve the above-mentioned problems, Dekuhonmima has made it possible to produce copper-tin alloy plating with a silvery white luster. The object of the present invention is to provide a cyanized steel-alkali stannate copper-tin alloy plating bath containing a special brightener that is characterized by thick plating. A system copper-tin alloy plating bath characterized by adding sodium thiocyanate polyethyleneimine and lh salt other than chloride,
This will be explained in detail below.

Thiocyanates have heretofore been known as brightening agents for the bath of the present invention, and potassium thiocyanate has been particularly effective. As a result of various studies conducted by the present inventors, it was found that sodium thiocyanate has a higher effect than potassium thiocyanate, although there is no brightening effect when added alone. However, when used alone, the usable gloss current density range is narrow, so that thick plating is impossible and only extremely thin plating on simple-shaped items is possible. However, the present inventors further investigated this sodium thiocyanate (by repeating the Hull cell test, observing the gloss state, etc., and examining the gloss effect of combining with a huge number of other additives). It has been discovered that by using polyethyleneimine and a nickel salt other than chloride in combination, the usable gloss current density range can be significantly expanded, and the gloss current density range can be increased to a level that allows thick eyelashes to be applied for 114 hours.

The polyethyleneimine referred to here is not a complete linear polymer, but a polyethyleneimine. Second. It has a branched structure containing tertiary amine nitrogen tubes. The compound has a molecular form in which the ratio of nitrogen atoms of each tertiary class is approximately 1:2=1 (To), and is represented by the molecular formula of the following form.

MH, (OH, OK, -1-)
! , -MTI-) y -OH,011,M<MW"=40.000-50.000 When this polyethyleneimine is added alone, it has some gloss effect, but the effect in the high current density area is As the amount of addition increases, deposition tends to worsen in areas with low current density, which are easy to see with matte plating. This is what we have.

The inventors also conducted various studies on nickel salts, but they found that they were not very effective when added alone, and only when they were added in combination to a bath containing sodium thiocyanate and polyethyleneimine, tests were carried out in a cell test tube at a total current of 1 µm. It has been found that when using the same method, gloss can be obtained over the entire surface. However, although nickel chloride does not have the above effects, the range of addition is about half narrower than that of nickel sulfate, nickel acetate, nitrous citrate, nickel potassium cyanide, nickel nitrate, nickel sulfamate, etc. It has the disadvantage that it tends to have uneven gloss and poor adhesion. In addition, by including chlorine in the plating bath, concentration control such as J/K(
It also has some drawbacks, which makes it undesirable.

The amount of thiocyanate added to the bath of the present invention is 10
~601/L”t: Preferably, 10II/L
If it is less than
If the amount of 017 exceeds the above, it will cause sludge in the high and low current density areas, and the range of gloss electric R1fif will become narrow.The most preferable addition amount is 30 to 50 II/L.

The amount of polyethyleneimine added is 0.03~Q,
It is 61/l. 0.031/L If it is not rowed, the gloss effect will be poor and the groove *0.61/l'! If the amount of addition is too high, not only can no gloss effect be expected, but also the precipitation in the low current density area becomes worse, resulting in thick and slow coating (the most preferable addition amount is 0.1
~ o, sy/z, and the amount of nickel salt added is preferably 20 to 1 s O#/l as a nickel salt, and if it is less than d/L, the gloss effect will be poor;
If it exceeds 150 m#/l, uneven gloss will occur and the cathode current efficiency will be significantly lowered, resulting in poor tin precipitation.The most preferable addition amount of this nickel salt is 30 to 100 tnl/l. be.

Next, as the plating operation conditions in the copper bronide-alkaline stannate copper-tin alloy plating bath according to the present invention, the bath temperature is 45 to 6
The temperature is preferably about 5°C. The anode is preferably an insoluble anode, preferably a carbon plate, and air agitation is used for better effects.

EXAMPLES The present invention will be explained in more detail below with reference to Examples.

Example-1 Sodium stannate 10051/ Sodium cyanide 28.5 fl/ Copper cyanide 1
1.5jl/ of sodium hydroxide 10II/
/.

Sodium thiocyanate 4011/l Polyethyleneimine (30% aqueous solution) 0.4 t7 as nickel salt in nickel sulfate) Prepare a plating bath as above, bath temperature 60°C, 7111
3゜5, When plating is performed using air agitation using a carbon plate as an anode, a silvery white glossy plating occurs at a rate of 0.5 to 5 μm/d.
A” current density range was obtained.

When plated at 2 mm/d-, a film of about 8 mm thick was obtained and maintained a glossy silvery white appearance.

Example-2 Sodium stannate 10011/A Nasylium cyanide 3011/L Copper cyanide
121/ Sodium hydroxide 1
01/L Sodium thiosyfunate 3511/L polyethyleneimy (30ts aqueous solution) 0.3-/L nickel potassium cyanide as nickel) 70 d
A plating bath was prepared as described above, and the bath temperature was 65°C.
, 5. Using a carbon plate as an anode and stirring the air,
When carried out, a silvery white bright plating was obtained at a current density range of 0.5 to 5.5 μm/μm. When plating for I minutes at 2 μm/dth”, a film of approximately 10 microns was obtained.
1. Maintained a shiny silvery white appearance.

As described above, according to the present invention, it is possible to produce an extremely excellent white tone tin alloy plating bath with a wide gloss current density range, excellent gloss thickening properties, long-term stability, and excellent plating uniformity. Therefore, it will be fully usable for industrial use.

The present invention can be applied to a copper plating bath based on copper stannate and sodium stannate as described in the Examples (although it can be practiced in other baths as well, and the four brighteners may be combined as appropriate within the scope of the present invention). Needless to say, it can be used as well.

that's all

Claims (1)

[Claims] A white steel-tin alloy plating bath in which sodium thiocyanate, polyethyleneimine and nickel salts other than chlorides are slightly added in a copper cyanide-alkaline stannate white copper-tin alloy plating bath.