Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H1/00—Contacts
  • H01H1/02—Contacts characterised by the material thereof
  • H01H1/021—Composite material
  • H01H1/023—Composite material having a noble metal as the basic material

Definitions

• the invention relates to a material for electrical low-voltage contacts, in particular for plug connections and sliding contacts, consisting of a gold-silver-palladium alloy, which can contain small amounts of osmium, iridium, ruthenium and rhodium.
• Mating and sliding contacts especially if they are to be used for the smallest voltages and currents in modern electronic devices, usually consist of carriers made of base metals that are coated with precious metals or precious metal alloys.
• Three essential requirements are placed on the noble overlay materials. First, they should be as resistant as possible to aggressive atmospheres, so that a low and stable contact resistance is achieved when they are used. Secondly, they should be subject to as little wear as possible in the friction pairing with a contact counterpart and have a low coefficient of friction, so that there is no wear through of the contact layer and the contact actuation forces can be low. Thirdly, an adaptation of the mechanical properties to the carrier materials is required for plating the support materials. In the case of the mechanical roll cladding that is usually used, an approximately matching recrystallization temperature of the support and carrier is particularly important for producing a high-quality composite material.
• a contact material for low-voltage contacts in particular for telecommunications, which consists of an alloy of 25-35% palladium, 35-45% silver and 25-35% gold.
• alloys for electrical contacts containing indium, tin and other base metals as minor constituents are known from DE-PS 25 40 956 (20-30 wt.% Palladium, 15-25 wt.% Silver, 2, 5-5% by weight tin, 0.05-0.5% by weight iridium, 0.05-0.5% ruthenium, 0.05-0.5% by weight copper, 0.1-2% by weight indium , Balance gold), DE-PS 26 37 807 (10-40% silver, 2-25% palladium, 1-5% nickel, 0.1-10% indium, 0.1-3% tin, balance gold) and DE-PS 29 40 772 (35-55% gold, 18-33.5% silver, 30-40% palladium and 1-6% indium or 0.5-2% indium and 0.5-2% tin) are known .
• Alloys of gold-silver-palladium-iridium and / or osmium with additions of 0.5-5% lead or 0.5-3% lead and 0.5-3% tin are known from DE-OS 33 45 162. Similar alloys based on gold-silver-palladium-iridium and / or osmium with additions of 0-5 at% lead and / or 0-5 at% tin and / or 0-10% copper are in DE-OS 34 20 231 described.
• All of these known alloys either do not have very high mechanical wear resistance (at relatively low levels of base additives) or do not have very good corrosion resistance (at relatively high levels of base additives).
• most of these alloys require soft annealing temperatures of over 750 ° C, sometimes over 900 ° C, which is why they are suitable for processing by roll cladding on typical carrier materials, e.g. CuSn8, poorly suited.
• This object is achieved in that particles of an intermetallic palladium-zinc compound are embedded in the alloy.
• This intermetallic compound can also contain a few percent of the remaining alloy components and should have particle sizes of less than 10 ⁇ m.
• the average particle size of the intermetallic compound is advantageously less than 1 ⁇ m. It is also advantageous if the intermetallic compound consists of the PdZn phase.
• Alloys have proven to be suitable which are 15 to 50% gold, 15 to 50% silver, 10 to 70% palladium, a total of 0 to 1% iridium and / or osmium and / or ruthenium and / or rhodium and 1.5 to 6 % Contain zinc, with more than 0.5% zinc must be present in the form of the intermetallic compound. Alloys with 20 to 40% gold, 25 to 50% silver, 20 to 40% palladium, 0 to 0.2% iridium, osmium, ruthenium and / or rhodium and 2 to 4% zinc are particularly suitable.
• the composite material Since the intermetallic compound has a high hardness, the composite material also has a greatly improved friction and wear behavior compared to a gold-silver-palladium alloy.
• a microstructure with a particle size of the intermetallic compound of less than 1 ⁇ m in length or diameter and particle spacing of approximately 1 ⁇ m represents a sufficiently fine distribution to to get the favorable properties also as cladding of only a few ⁇ m thickness.
• the composite material according to the invention with such a fine distribution of hardening particles recrystallizes even at temperatures of approx. 700 ° C. and annealing times suitable for production of a few minutes, i.e. a previously introduced cold working degrades and gains ductility, but on the other hand there is no harmful coarsening of the fine particle structure under these annealing conditions.
• This composite material can therefore be produced with an optimal microstructure as a compact block, and alloys can be manufactured just as easily as previously customary by roll-cladding on a carrier material, preferably a copper alloy, into a semi-finished product for contact parts.
• the processing steps can be based on the requirements of the copper alloy, so that the finished semifinished product has optimal properties with regard to the carrier and support material.
• the contact materials according to the invention can be produced by powder metallurgy or melt metallurgy, in which case a subsequent heat treatment is required.
• the formation of the intermetallic phase begins with the slow cooling in the casting and is optimized for 1 to 4 hours by heat treatment at temperatures from about 500 ° C. to about 50 ° C. below the solidus temperature of the respective alloy.
• the following table shows some alloys according to the invention (1 to 8) and for comparison some known alloys (10 to 12) and an alloy with a zinc content outside the claimed range (alloy 9).
• the increase in contact resistance (84% value of the total frequency) was determined on sheet metal samples before and after exposure in a three-component noxious gas at 30 ° C by measurement with a gold rivet as the counter body.
• the harmful gas consisted of air with 200 ppb NO2, 100 ppb H2S and 10 ppb C ⁇ 2 at 75% relative humidity.
• the contact force during the measurement was 0.1 N.
• the friction behavior was determined in tribometer measurements as a pair of round rivets against sheet metal with a contact force of 0.75 N.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Composite Materials (AREA)
• Materials Engineering (AREA)
• Contacts (AREA)
• Conductive Materials (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (3)

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ID=6303968

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Cited By (1)

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• 1986
  • 1986-06-28 DE DE19863621779 patent/DE3621779A1/de active Granted
• 1987
  • 1987-06-10 AT AT87108367T patent/ATE67894T1/de active
  • 1987-06-10 DE DE8787108367T patent/DE3773274D1/de not_active Expired - Lifetime
  • 1987-06-10 EP EP87108367A patent/EP0250958B1/fr not_active Expired - Lifetime
  • 1987-06-23 JP JP62154611A patent/JPS6311632A/ja active Pending

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