Thermally Stable Silver Alloy Coatings

Abstract

The present invention is directed to the electrolytic deposition of an alloy predominantly containing silver. Further constituents of the deposited alloy layer are palladium, tellurium and one or more of the metals Ce, Dy, Pb, Bi, Al, Ga, Ge, Fe, In, Co, Ni, Cu, Sn, Sb, Rh, Ru, Ir, Pt, Au. The present invention also relates to a method for the electrolytic deposition of a corresponding layer using a suitable electrolyte. The use of the electrolytically deposited alloy layer is also claimed.

Claims

1. An electrolytically deposited silver palladium alloy layer predominantly containing predominantly silver, and comprising less than or equal to 20 at % tellurium relative to the entire alloy layer, and one or more metals selected from the group consisting of Ce, Dy, Pb, Bi, AI, Ga, Ge, Fe, In, Co, Ni, Cu, Sn, Sb, Rh, Ru, Ir, Pt, and Au.

2. The alloy layer according to claim 1, wherein the additional metal or metals are present in an amount of less than or equal to 40 at % in the alloy layer.

3. The alloy layer according to claim 1, wherein silver is contained in the alloy layer in an amount greater than 60 at %.

4. The alloy layer according to claim 1, wherein palladium is present in an amount of 0.1-30 at % in the alloy layer.

5. The alloy layer according to claim 1, wherein tellurium is present in an amount of 0.1-10 at % in the alloy layer.

6. The alloy layer according to claim 1, wherein it has a hardness of >250 Hv.

7. A method for the electrolytic deposition of a silver-palladium alloy layer predominantly containing silver and having less than or equal to 20 at % tellurium relative to the entire alloy layer, wherein an aqueous, acidic and cyanide-free electrolyte having the following composition is used: a) a soluble silver salt b) a soluble palladium salt, c) a soluble tellurium salt in which tellurium has the oxidation state +4 or +6, d) a soluble salt of one or more of the metals selected from the group consisting of Ce, Dy, Pb, Bi, AI, Ga, Ge, Fe, In, Co, Ni, Cu, Sn, Sb, Rh, Ru, Ir, Pt, and Au e) at least one amino acid selected from the group consisting of: alanine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, lysine, leucine, methionine, phenylalanine, phenylglycine, proline, serine, tyrosine, and valine.

8. The method according to claim 7, wherein the pH value of the electrolyte during the electrolytic deposition is below 2.

9. The method according to claim 1, wherein the electrolyte density is between 1.0 and 1.5 at 23° C.

10. The method according to claim 1, wherein the current density during the electrolytic deposition is between 0.1 and 100 A/dm2, depending on the coating method and plant technology.

11. The method according to claim 1, wherein the electrolytic deposition is carried out at temperatures of 30° C. to 90° C.

12. A method of increasing corrosion resistance of an electrical contact material, which comprises applying the alloy layer according to claim 1 to the contact material.

13. The method according to claim 12, wherein the alloy layer is applied as an end layer or as an intermediate layer.

Description

EXAMPLES

[0039] Deposition conditions, beaker test, aqueous electrolyte according to DE102013215476B3:

[0040] 100 ml/l methanesulfonic acid 70%

[0041] 2 g/l amino acid

[0042] 20 g/l silver (as soluble silver salt)

[0043] 12 g/l palladium (as soluble palladium salt)

[0044] 500 mg/l tellurium (as salt of a tellurous acid)

[0045] 30 g/l methanesulfonate salt

[0046] 65° C./300 rpm 6 cm/PtTi anodes

[0047] Deposition conditions, beaker test, electrolyte according to the invention:

[0048] 100 ml/l methanesulfonic acid 70%

[0049] 2 g/l amino acid

[0050] 20 g/l silver (as soluble silver salt)

[0051] 12 g/l palladium (as soluble palladium salt)

[0052] 300 mg/l alloy metal (cerium, bismuth, lead, indium) (as soluble salt)

[0053] 500 mg/l tellurium (as salt of a tellurous acid)

[0054] 30 g/l of methanesulfonate salt

[0055] Both electrolytes with a pH of <1 were initially charged at 65° C. The stirring speed was 300 rpm with a 6 cm magnetic stirrer and a product movement at a speed of 6 cm/s was used. The experiments were carried out in a beaker on a 1I scale. PtTi anodes were used. The substrate used was a Cu substrate pre-coated with Ni and gold. The electrolyte density was 1.1 g/cm.sup.3 (23° C.). It was electrolyzed at various current densities (see Table 1).

[0056] Deposition results:

TABLE-US-00001 TABLE 1 Comparison of old and new electrolyte with respect to cracking and alloy composition at different current densities. i [%] [%] [%] [%] AZ R 180° C. Electrolyte [A/dm.sup.2] Ag Pd Te Bi cracks 120 min Old 1 87 9.5 3.5 X crack-free cracks Old 4 92.5 4.5 3.0 X crack-free cracks Old 6 93.5 4.0 2.5 X cracks cracks New 1 92.6 4.1 2.4 0.9 crack-free crack-free New 4 91.9 3.7 3.1 1.3 crack-free crack-free New 6 91.2 4.6 3.0 1.1 crack-free crack-free

[0057] By adding, for example, Bi, Ce, Pb, or In salts to an electrolyte for the deposition of AgPdTe alloys predominantly containing silver, the working range of the electrolyte is significantly increased. Crack-free deposits can be deposited under the same deposition conditions at significantly higher current densities and with significantly higher layer thicknesses. At the same time, the alloy composition of these layers is stable over a large operating range which is a significant advantage for high-speed deposition. Furthermore, the alloy according to the invention exhibits improved abrasion resistance and hardness properties. The hardness increases from 250 Hv to 300 Hv when adding, for example, 1.5 at % Bi.