JPS5939504B2 - Electroless plating bath for rhodium or rhodium alloys - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydrazine-type plating bath for electroless plating of rhodium or rhodium alloys onto metal or non-metallic surfaces, and in particular has excellent stability of the bath liquid and a high utilization rate of rhodium or rhodium alloys. This invention relates to a new plating bath with high plating speed and high plating speed.

Generally, chemical plating of rhodium or rhodium alloys is
A mixed solution of these metal salts, ethylenediamine (which forms an amine complex salt), ammonia, etc., to which hydrazine, sodium borohydride, or alkylamine borane is added as a reducing agent is used. However, if the above composition remains unchanged, the stability of the amine complex in the bath liquid is poor, and the reduction of rhodium or rhodium alloy proceeds too much, resulting in precipitation (
Therefore, it is common to add a stabilizer to suppress the reaction, but at present it is not possible to obtain a bath solution with sufficient stability even when a stabilizer is added. It has not been done. On the other hand, from a practical standpoint, since rhodium itself is expensive, it is desirable that it not only undergoes little self-decomposition in the bath solution but also has a high rate of precipitation from metal salts.

That is, it is ideal that the rhodium contained is almost completely utilized in each batch of plating operation. Furthermore, from the standpoint of operability, it is desirable that the precipitation time be fast.
The present inventors tried the known plating method in consideration of the above-mentioned requirements, namely, the stability of the 1st bath solution, the utilization rate of 20Dium, and the 3rd plating speed, but they were unable to find any bath solution that could satisfy the requirements. Ta.

That is, despite the use of a stabilizer, 1 and 2 are bad in baths that use borohydride salts as reducing agents, and 2 and 3 are bad in bath solutions that use alkylamine borane.

1 was unstable in the hydrazine bath. However, it has been found that while the former two baths have no room for improvement even when various bath liquid compositions are tried, an improvement of 1 degree can be expected in the hydrazine bath by improving the bath liquid. All methods of using hydrazine as a reducing agent for chemical plating of rhodium use a solution consisting of rhodium chloride or sulfate, ethylenediamine, and sodium hydroxide, and use a hydrazine salt alone or in combination with a borohydride salt as the reducing agent. In addition, potassium ferrocyanide (Chemical Abstracts Vol. 86, 94262n) and dimethylglyoxime (
Chemical Abstracts Volume 86, 46520y) Same 87
Volume, 27154m) etc. are used.

However, when rhodium is actually grown on the surface of metals, plastics, ion exchange membranes, etc. using these known bath solutions and plating conditions, any of the above 1, 2, and 3 is insufficient and cannot be satisfied. There was nothing.

In addition, ethylenediamine itself, which is present in the basic bath,
Rhodium plating, which is performed for the purpose of bonding a catalyst electrode to an ion exchange membrane, cannot be used because it may contaminate the membrane. In order to obtain a plating bath that is excellent in all of 1, 2, and 3 above, the present inventor has energetically studied reagents and coexisting stabilizers in a hydrazine type plating bath, and found that the The present invention was completed based on the discovery that the desired object can be achieved when the metals of the composition are used as an ammine complex salt solution and a hydroxylamine salt is used as a stabilizer.

That is, the present invention contains (a) an ammine complex salt of rhodium or a mixture thereof with an ammine complex salt of another metal, (b) a hydroxylamine salt, and (c) hydrazine, and contains PHL
The present invention relates to an electroless plating bath for rhodium or a rhodium alloy, characterized in that the plating bath is O~13.

The rhodium ammine complex salt in the present invention is, for example, a hexaammine salt obtained by putting a rhodium salt together with aqueous ammonia in an autoclave and reacting at a pressure of 10 to 301<g/d and a temperature of 110 to 160°C for 3 to 12 hours. It is preferable to use [Rh(NH3)6]X3 or pentaammine salt [Rh(NH3)5X]X2 (X is halogen, NO2, etc.), but rhodium salt is mixed with aqueous ammonia until the solution becomes light yellow. A solution obtained by boiling while adding aqueous ammonia can also be used.

When plating rhodium alloy, rhodium and platinum,
It is preferred that mixed salts with salts of ruthenium, iridium, nickel, cobalt, etc. are similarly treated with hot ammonia water under pressure and used as a stable mixed ammine salt complex solution. At that time, the molar ratio of the metal added to rhodium is 0.1 to 1.0 mol to 1 mol of rhodium, and even in the case of three or more elements, the added metal to 1 mol of rhodium. It is preferable that the total number of moles is 1 mole or less. For example, if two elements are used, for example, if platinum or iridium is used for 1 mole of rhodium, 0.
It is preferably 1 to 0.5 mol, and in the case of ruthenium, nickel or cobalt, 0.1 to 1 mol. As the hydroxylamine salt used in the present invention, water-soluble salts such as hydrochloride, sulfate, nitrate, etc. are preferable.

As the hydrazine in the present invention, hydrazine that becomes hydrazine in an aqueous solution state, such as hydrazine hydrate, hydrochloride, sulfate, etc., can be suitably used.

The bath solution composition of the present invention is 0.001 to 0.1 M/l (0.1 to 109/l in the case of rhodium) using ammine complex salt as rhodium or rhodium alloy, preferably 0.001
~0.05M/l (0.1-59/l for rhodium)
, hydroxylamine from 0.003 to 1.5 M/l (0
．． 1-50g/l) preferably 0.003-0.15M
/l (0.1-59) and hydrazine 0.003-1
．． 5M/l (0.15-75 for hydrazine monohydrate
g/l) is preferably 0.003 to 0.3 M/l (0.15 to 159/l in the case of hydrazine monohydrate). In the present invention, the bath solution having the above composition is mixed with aqueous ammonia or an alkaline...buffer solution to a pH of 13 to 13, preferably 1.
The number is adjusted to a range of 1 to 12 before use. When the pH is 13 or higher, the reduction rate becomes faster and self-decomposition increases, and when the pH is lower than 10, the growth rate is low and the plating time becomes long.

When hydroxylamine exceeds 509/l, growth is extremely suppressed and plating becomes difficult to proceed. The plating bath of the present invention has an ammine complex ion [Rh(NH3)6]3 in the bath liquid.
+, [Rh(NH3)5C1]2+[Rh(NH3)5
H20], etc. are rhodium ions (Rh3+, (RhCl6)3 [Rh(NH2C2H,
NH2)3]3+, etc.) (the same applies to rhodium alloys), and when a hydroxylamine salt is added, an even more stable complex is formed, and self-decomposition is almost suppressed.

Therefore, the plating bath of the present invention has extremely excellent stability without self-decomposition over a long period of time when the object to be plated is not immersed.

When the object to be plated is immersed, a catalytic reduction reaction starts and selective plating proceeds until rhodium or rhodium alloy in the bath liquid is consumed at a high rate of 95% or more.

The plating time is not constant because it depends on the shape of the object to be plated, but an example of obtaining a 3 μm plating layer is 1.5 μm.
It is a short time of ~2 hours. Table 1 shows a comparison of stability between an example of the plating bath of the present invention and a known hydrazine type plating bath.

As is clear from Table 1, it can be seen that the plating bath of the present invention has extremely excellent stability of the bath solution and selectivity to the objects to be plated.

The objects to which the plating bath of the present invention can be applied include metals such as copper, nickel, iron, alloys thereof, titanium, tantalum, etc., and industrial materials such as electronic parts and electrodes.

Furthermore, it can be applied to materials that can be conventionally electroless plated, such as synthetic polar resin, glass, and ceramics. Furthermore, since the plating bath of the present invention does not contain ion-active substances such as ethylenediamine and dimethylglyoxime, it is particularly excellent as a bath liquid for bonding rhodium or rhodium alloys to ion exchange membranes. It can be applied as a technology to create a composite in which electrodes are bonded to the membrane surface of a molecular electrolyte (ion exchange membrane). In either case,
It is preferable that the object to be plated be activated in advance.

In the case of metal, the surface is activated by immersing it in a salt solution of palladium, platinum, rhodium, etc., and if necessary, subsequently immersing it in an aqueous boron hydride salt solution, and then immersing it in the plating bath of the present invention.

In the case of polymers, glass, and ceramitus, the present invention is performed after surface hydrophilization, sensitization treatment, and activation treatment, which are usually used when chemically plating copper, nickel, etc., on the surfaces of these materials. Immerse yourself in the bath.

In the case of an ion exchange membrane, after roughening the surface, a metal salt (preferably ammine complex salt) solution is first adsorbed, and then reduced with a sodium borohydride solution to bond the first layer of 1 to 2 μm. It is grown by immersing it in the plating bath of the present invention.

The plating temperature is 50 to 90°C, preferably 60 to 75°C.

The plating thickness is determined by plating by pre-existing the amount of rhodium or rhodium alloy necessary for the surface area of the object to be plated in the bath liquid.

The utilization rate as rhodium or rhodium alloy in the bath liquid is 9
At a high rate of 5% or more, the small amount of rhodium remaining in the waste liquid can be recovered by adding a borohydride salt to precipitate it. The plating layer according to the present invention has electrical properties and mechanical strength equivalent to those of electroless plating, and can be used for plating objects with complex shapes that are characteristic of electroless plating, small electronic parts, electrical contacts, and non-magnetic materials. It is also suitable for plating magnetic rhodium alloys. Furthermore, as an industrial material, it can be used as a plating method when producing an ion exchange membrane-electrode assembly for aqueous electrolysis or fuel cells. Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Add 50ml of 28% NH4OH to 135g of RhC and heat at 20k9/CTL1150°C for 12 hours in an autoclave.
After treatment for a period of time, the solution was taken out, subjected to heat aging, and the concentrated solution was concentrated to crystallize hexaammine rhodium () chloride.

Using this, a plating bath of the present invention having the following composition was prepared. A copper plate was plated using the above bath solution.

After degreasing the sample copper plate (2×4c!RL) with alkali, hydrochloric acid (
3%) at room temperature for 10 to 20 seconds, then 5 (fl)
It was activated by immersing it in a 2H-HCI solution of PdCl2 at room temperature for 30 seconds.

After washing with water, it was immersed in the above plating bath solution for 2 hours to obtain rhodium plating with a thickness of about 2 μm. No precipitation was observed in the bath liquid or on the vessel wall, and the remaining amount of rhodium in the bath liquid after treatment was 1 Tr! 9 or less, the rhodium utilization rate was 98 (Ff) or more. Example 2 Ammine complex ions [Rh(NH3)5C1]2+ and [Rh(N
A bath solution having the following composition was prepared using the H3)0H20]3+ solution.

Rhodium plating was performed on ABS resin (3×3 (1 sample)) using the above solution.

For sample pretreatment, the following bath solution was used, as is commonly done in plastic plating.

etching bath ↓1ZV~Yamadeno Etching was performed at 65° C. for 20 minutes and washed with water.

Catalyst bath The sample was immersed in the above bath solution at 30°C for 3 minutes.

activation bath sodium borohydride 0,59 The activation bath was treated for 2 minutes at room temperature.

Subsequently, it was immersed in a rhodium plating bath for 30 minutes to obtain a shiny rhodium plating of about 0.5μ.

The rhodium plating bath was used repeatedly three times using the same type of sample, and the same rhodium plating was obtained for each sample. During this period, the bath liquid was stable and no decomposition occurred. Example 3 Perfluorinated sulfonic acid-based ion exchange membrane [manufactured by DuPont, Nafion 117 membrane, membrane thickness 7 mils (approximately 0.175 mm)
)] with a diameter of 80m77! rhodium was bonded to the circular membrane.

The pretreatment of the membrane is to first roughen it by sandblasting, and then to
It was deionized by boiling with N-HCI and washed with water.

Next, a rhodium amine complex salt prepared in the same manner as in Example 1 [
After immersing in Rh(NH3)6]3+ solution (room temperature, 5 hours) and washing with water, ammoniacal NaBH4O. A rhodium layer of 1 to 1.5 μm was deposited by reduction at 40 to 60° C. in an O 5% solution. A bath solution having the following composition was used to grow this rhodium layer. The plating process was carried out for 2 hours, and the rhodium layer after the process grew to a thickness of about 5 μm.

No decomposition was observed in the bath solution, and the utilization rate of rhodium was 99%. Example 4 RhC13 and Ptcl4 at a Pt/Rh molar ratio of 0.5
The ammine complex salt mixture was mixed at a ratio of /1.0 and put into an autotale with aqueous ammonia at 20 kg/~ and treated at 160°C for 10 hours to prepare an ammine complex salt mixture and use it.

A nickel sample plate (5 x 5 cTn) was degreased with alkali and R
Activation treatment was performed using a solution of hCl329, HCl1Oml, and water total amount 11, and after washing with water, it was immersed in the above plating bath for 70 minutes.
Plating treatment was carried out at ℃ for 2 hours. Approximately 3μ on the nickel surface
A thick rhodium-platinum alloy was obtained, and the utilization rate of rhodium and platinum was 95% or more.

Claims (1)

[Claims] 1. Rhodium or rhodium containing (a) an ammine complex salt of rhodium or a mixture thereof with an ammine complex salt of another metal, (b) a hydroxylamine salt, and (c) hydrazine, and having a pH of 10 to 13. Electroless plating bath for alloys.