Precious metals mainly refer to gold, silver, palladium, platinum, rhodium, iridium and other materials.They have good electrical conductivity, thermal conductivity, corrosion resistance and high temperature stability, much as functional materials and applications of precious metals in industry as contact material, their common characteristic is soldering area is small, requirement of brazing seam metal good shock resistance, high strength, has a certain antioxidant properties, and can withstand the electric arc, but does not change the properties of contact materials and electrical components.Because the brazing area of the contact is limited and overflow of the filler metal is not allowed, the welding parameters of brazing should be strictly controlled.

Most heating methods can be used for brazing precious metal contacts.Flame brazing is often used in larger contact components, induction brazing is suitable for mass production, with normal resistance welding machine also can undertake resistance brazing, but carbon blocks should be used as electrode, choose low current and longer brazing time, when at the same time it requires a substantial amount of brazing contactor components or on a component soldering multiple contacts, brazing furnace, can be used in order to obtain high quality of braze welding head, and guarantee the performance of the material itself will not be affected, had better use vacuum brazing.

Brazing gold and its alloy contacts mainly use silver base and copper base, which not only guarantees the conductivity of the brazing joint, but also is easy to be wetted.If the electrical conductivity of the joint can be met, a filler metal containing elements such as Ni, Pd, Pt can also be used for brazing nickel and cobalt alloys with good oxidation resistance.If ag-Cu-TI solder is used, the brazing temperature shall not be higher than 1000℃.

The silver oxide generated from the silver surface is not stable and is easily brazed.Silver can be brazed with tin-lead solder mixed with zinc chloride aqueous solution or rosin as brazing agent.In brazing, a silver filler metal is often used, with borax, boric acid or a mixture of them as the brazing agent.BAg61Culn, BAg59CuSn, BAg72Cu, etc. are mainly used for vacuum brazing of silver and its alloy contacts.

Brazing palladium contacts may be made of gold or nickel base brazing alloys, or silver, copper or manganese base brazing alloys, which easily form a solid solution.

Brazing platinum and its platinum alloy contacts, widely used silver base, copper base, gold base or palladium base solder, etc.BAu70Pt needle material is selected, which can effectively improve the remelting temperature of brazing joint and increase the strength and hardness of brazing joint without changing the color of platinum.B49 TiCuBe filler metal can be used if platinum contact is brazed directly on cutting alloy.In non-corrosive media, platinum contacts whose operating temperature does not exceed 400℃ shall be selected with low cost and good technical performance.