JPH0254792A - Ruthenium plating solution - Google Patents

Abstract

PURPOSE:To obtain a ruthenium plating soln. capable of giving lustrous thick plating without cracking by using an inorg. ruthenium salt and an acid as essential components and adding a salt of a group III metal. CONSTITUTION:An inorg. ruthenium salt and an acid are used as essential components and at least one kind of salt of a group III metal is added to obtain a ruthenium plating soln. Ruthenium sulfate, ruthenium chloride or other inorg. salt is used as the ruthenium salt but ruthenium sulfate is preferably used. The proper concn. of ruthenium in the plating soln. is about 0.5-50g/l. Sulfuric acid, hydrochloric acid or other inorg. acid is used as the acid according to the kind of the used ruthenium salt and the concn. is regulated to about 1-100g/l. The salt of a group III metal may be the sulfate, chloride or sulfamate of Sc, Y, In or Ga and the concn. is regulated to 0.1-10g/l (expressed in terms of the metal). When electroplating is carried out with the plating soln., plating of about >=2mum thickness is obtd. without cracking.

Description

[Detailed description of the invention] Peel and fruit! Light! The present invention relates to the composition of a ruthenium electroplating solution.

Ruthenium plating is useful for coating the surfaces of electrical contacts or mechanical parts that require wear resistance, and is also used for decorative items due to its color tone and hardness.

Conventionally proposed plating solutions include (RuzN(I)
IzO)zYa)ff-(Y=CI or Br) and sulfamic acid (Japanese Patent Publication No. 47-4122), (
NH4) 1 (RuJ(llzO) ZCII+) to G
a, containing at least one metal selected from In and TI (Japanese Patent Publication No. 49-26175), (NH
a) zcRuzN(llzO)zcIa) containing In and at least one type of platinum metal (Special Publication No. 55
-44157) and a complex salt of ruthenium metal and sulfamic acid containing Ni, Go, Fe, Sn, Pb and M
containing a small amount of metal selected from
-1081) etc. are known.

The compositional feature of these plating solutions is that ruthenium is in the form of organic complexes such as acochlore complexes.
Although a thick film can be obtained by increasing the plating time with such a plating solution, if the film thickness exceeds 2 μm, cracks will occur, resulting in poor appearance, the solution is likely to deteriorate, and the deposition rate will be slow. There was a problem.

The present invention was developed in view of the problems seen in the conventional ruthenium plating solution described above, and it does not cause cranking even when plating with a thickness of 2 μm or more. An object of the present invention is to provide a ruthenium plating solution that provides a glossy film.

The present invention will be explained in detail below.

As a result of intensive research in order to solve the above problems, the present inventors used ruthenium salt in the form of an inorganic salt such as ruthenium sulfate, and added additives containing compounds from the periodic table. By adding at least one type of metal salt of group ■,
The present invention was achieved based on the knowledge that a crack-free plating film can be obtained even when the plating film thickness is 2 μm or more.

As mentioned above, the ruthenium salt used in the present invention may be any inorganic salt such as ruthenium sulfate or ruthenium chloride, and ruthenium sulfate is particularly preferred.

The ruthenium concentration in the plating solution is 0.5 to 50 g.
/l, preferably 3 to log/7! It is. 0.
If it is less than 5 g/12, it will not be possible to obtain a plated film of 2 μm or more without cranks, while if it exceeds 50 g/l, thick coating will be possible but cranks will easily occur.

Further, the acid may be any inorganic acid such as sulfuric acid or hydrochloric acid, but it is preferably selected according to the type of ruthenium salt used. That is, when using ruthenium sulfate as the ruthenium salt, sulfuric acid is used as the acid.

The acid concentration is 1 to 100g/I! ,, preferably 6 to 20 g/l. If Ig/ is less than 1, a precipitate that is thought to be hydroxide will be formed in the plating solution, and if it is less than 100 g/
I! If it exceeds this, cracks are likely to occur.

Next, the metal salts of group Ⅰ used in the present invention include Sc,
Examples include metal salts such as YSIn and Ga. Taking In as an example, indium sulfate, indium chloride, indium sulfamate, etc. are preferable.

The concentration of the metal salt is 0.1 to Log/l, preferably 0.5 to 3 g/(!0.1 g/A) in terms of metal.
If it is less than 10g/7, cracks are likely to occur. If it exceeds this, clouding will occur and poor adhesion will occur.

The important point of the present invention is to add this group Ⅰ metal salt, thereby suppressing the occurrence of cracks due to internal stress in the plating film, and obtaining a glossy plating film with no cracks of 2 μm or more. I can do it.

The effects of these additive metals are not clearly known, but since at is detected in the plating film, it is assumed that they somehow alleviate the internal stress of the plating film by eutectoiding with ruthenium. Conceivable.

When performing plating using the ruthenium plating solution of the present invention, it is desirable that the temperature of the plating solution be 30 to 80°C, preferably 50 to 70°C. If the temperature is less than 30°C, the deposition rate is slow; if it exceeds 80°C, evaporation from the plating solution becomes a problem, and water needs to be replenished to keep the concentration of the plating solution constant.

Further, it is preferable to stir the liquid in order to promote mass transfer, but when a static bath is used in the present invention, it may be sufficient to stir the object to be plated.

On the other hand, when plating using jet plating equipment,
The liquid flow rate is preferably 1 to 4 m/s. If it is less than 1 m/s, the deposition speed will be slow, and if it exceeds 4 m/s, cracks and cracks will easily occur.

The current density is preferably 2 to 10 A/dm'' in the case of a static bath, and 10 to 12 OA/dmz in the case of a jet type. In either case, if it is less than the lower limit, the deposition rate is slow, and if it exceeds the upper limit, cranking is likely to occur. Become.

On the other hand, the metals to be used in the plating solution of the present invention are not particularly limited, but include nickel, stainless steel, copper, brass, titanium,
Examples include gold and silver.

The present invention will be specifically explained below using Examples.

Example 1 A 20m+s x 25+am brass plate was used, the anode was a platinum plate, and the ruthenium concentration was 3 to 5 g/ff.
, H2SO4 concentration = 6-10g/l, additive concentration: 0-2g#! , current density: 2-5 A/dm! A plating test was conducted in a static bath (liquid temperature: 50°C) with a plating time of 30 to 80 minutes.

The results are shown in Table 1.

Example 2 A 20m+*×25mm brass plate was used, the anode was a platinum plate, and the ruthenium concentration was 10 to 15 g/N.
pfl: 2.5, additive concentration: 0-3g/β, current density: 40-608/dn+", plating time: 5-2
The plating test was conducted in a jet type (liquid flow rate: 2m8, temperature near 0°C) for 0 minutes.

The results are shown in Table 2.

As explained above, by using the ruthenium plating solution of the present invention, even if the plating thickness is 2 μM or more, a shiny film without cranking can be obtained, so it can be applied as an electrical contact material, etc. This results in a long-lasting and reliable product.

Claims (3)

[Claims] (1) Main ingredients are ruthenium inorganic salt and acid, and
A ruthenium plating solution comprising at least one metal salt selected from Group III metal salts. (2) The ruthenium plating solution according to claim 1, wherein the Group III metal salt is a salt of a metal selected from the group consisting of Sc, Y, In, and Ga. (3) The ruthenium plating solution according to claim (1), wherein the ruthenium inorganic salt is ruthenium sulfate.