DE2360834A1 - Bright, pore-free palladium electro-deposn - from baths contg. palladium amine complex, e.g. with tetraethylene pentamine - Google Patents

Abstract

Bright pore-free Pd layers are electrodeposited from baths contg. Pd as an amine complex, pref. with an amine of formula NH2(CH2CI'2NH)nCH2CH2NH2) (where n = 3). Thick pptes. can be obtd. The baths can be used for revolving drum- or supported devices, and they generate no unpleasant or toxic vapours, can be used without extractors, have stable pH and are easily controlled. Amine complexes can be prepd. by pptg. Pd as hydroxide from a Pd salt soln. e.g. of halide, and dissolving in amine, e.g. tetraethylene pentamine (I). Soln. can be admixed with conductivity-raising salts, and pref. 0.01-5 g/l thiourea (as brightener). Bath is pref. operated at pH 7-11, current intensity 0.1-2.5 A/dm2 and 20-95 degrees C.

Description

HANS TRAPPENBERG · PAYENTINGENiEUR · KARLSRUHE

4th December 1973 II 923

IÜTOVAIT-Stroebe KG., 7534 Birkenfeld, Industrie Strasse 44

Bath for the galvanic deposition of palladium layers

There are three types of palladium baths that differ from each other build up different types of palladium compounds:

a) Acid baths based on chloride, also with soluble palladium anodes operate,

b) alkaline baths based on the palladium hydroxo complex,

c) Baths based on the nitrate or nitrite complexes in neutral or ammonical medium '.

The palladium electrolytes belonging to the last group are in in practice preferred, using as insoluble anode material in general Platinum or platinum-coated titanium is used. However, there are disadvantages to the relatively good yield of such baths compared to that hardly any pore-free coatings. are achieved that the constantly evaporating ammonia unpleasant operating conditions creates and requires extensive suction devices, and that the pH of such baths is unstable and therefore only very difficult to keep constant.

In order to still achieve pore-free coatings, it is already has become known for the deposition of palladium coatings an aqueous neutral or alkaline solution with a palladium compound and an ammonium salt of a weak organic acid which does not form an insoluble compound of the palladium compound, to use. Although an improvement could be achieved in this way, it is not possible to achieve thick, completely pore-free To achieve coatings with palladium; also blejbb still the There is a need to extract the ammonia vapors.

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The acidic palladium baths are almost always aggressive and effective a range of base metals. This aggressiveness also results in rapid contamination by foreign metal ions brought about. Since they also mostly deposit powdery precipitates these palladium baths only meet subordinate requirements.

In general it can be said that the conventional baths only imperfect precipitation with more or less strong pores allow that are glossy only in relatively thin layers. In addition, as a result of the hydrogen uptake of the Palladium in the cathodic deposition from the known baths with a lower current yield, the hardness as well as the internal Precipitation tension is relatively high. Furthermore, various of the known types of bath are not used in suitable for the drum.

The object of the invention is a bath and a method of use this bath to indicate that

1. is suitable for both drum and rack goods,

2. supplies thick, pore-free and shiny palladium precipitates, J. no unpleasant or even harmful vapors developed

or that can be used without a suction device and 4. that has a stable pH value combined with a foolproof one Use of the bath or with simple bathing .

According to the invention, this object is achieved in that the bath contains palladium in the form of an amine complex, preferably using an amine of the general formula NHg (CHg CH ₂ NH) _n GH ₂ NH ₂ , where η is 3.

509824/0765

Such an amine complex of palladium is "for example obtained by precipitating the palladium as hydroxide from palladium chloride or another palladium salt solution and on ~ final dissolving in tetraethylene pentamine. This solution will be then soluble, conductivity-increasing salts are added in a manner known per se and in a manner according to the invention to add a To get shiny precipitate, add thiourea at a concentration of 0.01 Ms 5g / l.

If such a bath is used at a pH value between 7 · ..11 »with a Current density of 0.1 ... 2.5 A / dm and a temperature of 2O ... 95 ° C, completely pore-free, shiny deposits of palladium result.

The bath according to the invention has a very stable pH value and, associated therewith, a simple bath management. It evolves no unpleasant or even harmful vapors and it is, as corresponding tests have shown, both for drum and for & order goods suitable. Since thick precipitates can also be achieved without any pore formation, this is the one presented at the beginning Task completed.

The bath according to the invention and the method for its use will be explained using two examples. The PalladJun solution is obtained by precipitating the palladium as a hydroxide from palladium chloride and dissolving it in tetraethylene pentamine. In principle, all water-soluble, conductivity-increasing salts that do not form precipitates with other bath components can be used as the conductive substance, such as "for example citrates or phosphates. The amine can be used to correct the pH, as can any usable alkali. The bath temperature should be within der limits are between 20 ⁰ O and 95 ⁰ O.

509824/0765

example 1

Palladium (in the form of the amine complex mentioned) 10 g / l Disodium hydrogen phosphate (conductive salt) 50 g / l

Thiourea 0.5 g / l

Tetraethylene pentamine up to pH 10
Temperature approx. 55 ° C.

The bath results in a shiny, pore-free palladium deposit. The current intensity increases with increasing Semperaturj it is for example at 2O ⁰ C 0.4 A / dm ² while / dm increases at 70 ⁰ C at 1.5 A. The current yield is 100%.

Example. 2

Palladium (as amine complex) 10 g / l

Potassium citrate (conductive salt) 50 g / l

Thiourea 0.01 g / l

Tetraethylene pentamine up to pH 8.5

Temperature approx. 50 ⁰ C

The bath obtained at a current density of 0.5 A / dm etark a shiny palladium bodice shock is at a thickness of very ductile, and has a hardness of 200 kgf / mm.

509824/0765

Claims (4)

Patent claims (O bath for galvanic deposition of shiny, pore-free Palladium layers, characterized in that it contains palladium in the form of an amine complex. 2. Bath according to claim 1, characterized in that the amine complex is formed with an amine of the general formula UH ₂ (CH ₂ OH ₂ NH) _n CH ₂ OH ₂ HH ₂ with η £ 3. 3. Bath according to claim 1 or 2, characterized in that thiourea is added in a concentration of 0.01 ... 5 g / l. 4. A method for the galvanic deposition of palladium layers using a bath according to claims 1 to 3> characterized in that the pH is set between ^ ... 11, the current between 0.1 ... 2.5 A / dm and the temperature is kept between 20 ... 95 ⁰ C. 509824/0765