DK157839B - PIPELINE ALLOWANCE FOR CONNECTING CONTACT MATERIALS - Google Patents

Description

DK 157839 B

The invention relates to the use of silver alloys for the direct application of oxide-containing silver contact materials, in particular of silver tin oxide, to contact carriers.

Precious metal-containing contact materials with metal oxide deposits, such as cadmium oxide, tin oxide or indium oxide, are usually soldered onto base carriers such as iron, nickel or copper. Since these composite materials are intended to ensure a long life during coupling operation, a solder solder connection between the materials is required.

In the art, such solder joints are usually made by providing the contacts to be soldered with fine silver or silver cadmium (tin) alloy layers which are easily solderable. Since these additional layers lead to increased costs in the manufacture of 15 contact coatings and have a high silver content, there are also methods in which the manufacture of a special solder layer is avoided and which leads to direct soldering.

It is e.g. from DE Specification No. 23 65 20 450 known to cast silver-copper alloys on the back of silver metal oxide materials and then solder on the support. It is also known to apply reactive solder based on copper-silver phosphorus to contact materials, e.g. from DE Publication No. 24 38 25 922.

DE Publication No. 30 11 821 discloses one of two parts of direct solder, in which a layer of AgP during soldering must react with a layer of AgCd to form a unit solder silver / copper / 30 cadmium / phosphorus. Also in DE publication no.

29 48 915 discloses a direct solder of silver-copper-cadmium-tin-indium for soldering oxide-containing silver contact materials on contact carriers. This solder? medium, the silver metal oxide materials moisturize fairly well without leading to brittle phases in the diffusion zone. DE Publication No. 31 23 357 also discloses a solder especially suitable for silver-tin tin.

DK 157839B

2 oxide materials and consists of the components silver-tin-indium-germanium.

Thus, quite a number of solder alloys are wetted, which moisten silver metal oxides and which do not form brittle reaction zones in the diffusion zones between the contact materials and the solder and between the support and the solder.

The known lot alloys admittedly have only limited use. Especially with silver tin oxide materials, there is the major disadvantage that the connection zone has, for the most part, a shorter life than the highly resistant contact materials for contact combustion.

The particular problem with regard to the contact soldered on carriers is due to the stresses that build up due to temperature differences. On the contact surface of the contact coating itself, temperatures above 1000 ° C are achieved due to the energy in the arc. On the opposite side of the welded component, temperatures that are not significantly above room temperature should prevail. This temperature difference is over a distance of e.g. 3 mm. This results in large shear and tensile stresses due to the constant temperature change at the coupling, which can cause the contact coating to peel off. In contact coatings with a fine silver intermediate layer, these stresses can to some extent be avoided by plastic deformation in this highly ductile layer. However, the life of these composite materials is limited by the low strength of silver or the association of silver with silver / metal oxide. In the case of directly welded contact coatings, such an intermediate layer may not be effective.

DE Publication No. 2840 415 discloses brazing agents of silver-copper alloys with 5% palladium, which are used together with thermoplastic materials as brazing pastes for brazing metallic materials such as 35 car parts, installations, jewelery and silver objects. However, soldering of oxide-containing contact materials is not mentioned in this document.

3

DK 157839 B

The invention aims at providing solder alloys for the direct soldering of oxide-containing silver contact materials, in particular silver tin oxide, onto contact carriers which wettable the silver metal oxide materials well and thus are suitable for soldering. In addition, the solder alloys must be ductile to prevent the formation of shear and tensile stresses by plastic deformation, and must have greater strength than silver, so that the tensile strength is not exceeded by the shear and tensile stresses produced by the coupling processes. In addition, to avoid further stresses, these solder alloys must be adapted to the thermal expansion coefficients of the other components.

To achieve this, the solder alloy used according to the invention is characterized in that it contains, in addition to silver, 20-35% by weight copper and 0.1-5% by weight palladium.

Such alloys surprisingly fully fulfill the desired purpose. These solder alloys outperform the conventional fine silver plating and the known direct solder with respect to the life of the solder compounds thus produced. Coupling experiments in several relay types, in particular in connection with the highly resistant silver / tin oxide contact materials, have shown a considerable superiority of the solder alloys of the invention with respect to the lifetime of the components. Furthermore, they moisturize the known silver / metal oxide materials very well without reaction to or with e.g. tin oxide to lead to brittle diffusion zones.

30 solder alloys containing, in addition to silver, 24-32 weight percent copper and 0.5-3 weight percent palladium, have proved particularly suitable.

By using solder alloys with 1% by weight palladium, particularly economical alloys can be obtained, 35 which furthermore have the advantage of a low working temperature and slightly increased service life.

Claims (3)

Use of alloys consisting of 20-35 20% by weight of copper, 0.1-5% by weight of palladium and the balance of silver, for the direct soldering of oxide-containing silver contact materials, especially of silver tin oxide, to contact carriers. 1. Small plates of Ag / SnC 2 (88/12) in the dimensions 9 x 9 x 1.25 mm were soldered under protective gas 5 to copper-plated steel carriers with a silver alloy of 26.6% copper and 5% palladium. The solder was applied over a soldered film. The coupling numbers in a 75A relay averaged 70,000 couplings in AC4 operation. For comparison 10, with conventional silver plated contacts, only 30,000 couplings were soldered. Use of alloys consisting of 24-32 25% by weight copper, 0.5-3% by weight palladium and the balance silver, according to claim 1. 2. Small sheets of AgSnC ^ (88/12) in the dimensions 14 x 14 x 2.3 mm were soldered to copper carriers under protective gas with a solder of the composition AgCu28Pdl. The coupling numbers in a 250A relay were 120,000 (Ag plated material 90,000). Use of alloys containing 20-35% by weight copper, 1% by weight palladium and the balance silver, according to claim 1. 30