Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
  • H01R13/00—Details of coupling devices of the kinds covered by groups H01R12/70 or H01R24/00 - H01R33/00
  • H01R13/02—Contact members
  • H01R13/03—Contact members characterised by the material, e.g. plating, or coating materials

Definitions

• the present invention is concerned with electrical connectors or contacts and, more particularly, with electrical connectors useful in carrying substantial currents at voltages in excess of, perhaps, 10 volts.
• the electronic contacts tend to degrade if exposed to temperatures elevated above 25°C even as low as 100°C.
• Gradually atoms of copper and silver migrate to the gold surface.
• Migrated copper makes the contact surface subject to sulfidation and oxidation while migrated silver is particularly detrimental when the contact surface is used in sulfidizing atmospheres as mild as ordinary room air.
• the present invention contemplates an electric power connector adapted to provide an interruptible conductive path for electrical current (for example, current of at least about 0.1 ampere) comprising at least two components adapted to be placed in surface contact one with another. At least one of the components has a fayable surface of contact made of an alloy of gold and nickel. At the fayable contact surface the alloy contains about 1 to about 10% by weight of nickel. The amount of nickel in the gold generally increases with distance from the fayable contact surface to an underlying metallurgically bonded layer preferably of essentially pure nickel. However, the alloy which is made by diffusing nickel from an underlayer into a gold overlayer usually exhibits a particular structure when examined by sputtering and Auger analysis.
• the immediate surface exhibits a relatively high nickel content.
• the nickel content falls somewhat and remains relatively constant for perhaps up to two-thirds of the thickness of the gold layer which ranges from 0.3 to 2 micrometers. Over the remaining thickness of the gold-containing layer, the nickel content rises rapidly to the nickel content of the underlying metal.
• Auger analysis some­times produces results at the surface of an object being examined which may be surface artifacts and may not represent or be signifi­cant with respect to properties of the bulk material. Accordingly, it appears safe to say that in the gold layer of the contact structure of the present invention, the nickel content near the outer surface is at a relatively low level. It remains at that low level until, at some point remote from the surface the nickel con­tent of the gold rapidly increases.
• the electrical power connector can be in any conventional contact form such as male and female plug components, pins, threaded structures or the like.
• the connectors are of such configuration that they can be made from composite, electrical contact material in strip form.
• Such contact material which is also within the contemplation of the present invention comprises a strip-­form structural base of electrically conductive material, e.g. metal having at least one major surface comprised of nickel or nickel-rich alloy underlying a layer of gold about 0.1 to 2 micrometers thick metallurgically bonded to the nickel or nickel-rich alloy. This diffusion is such as to provide about 1 to about 10% by weight of nickel at the outer major surface.
• nickel-rich alloy means an alloy containing at least about 90% nickel advantageously at least 95% or 99% nickel and includes commercially pure nickel and nickel-cobalt alloys.
• contact materials of the present invention include copper, copper-base alloys such as brass, cupro-­nickel, beryllium copper, copper-nickel-tin alloy and copper-nickel-­aluminium alloy, nickel, cobalt or nickel-cobalt alloy particularly in strip form.
• copper, copper-base alloys and cobalt the basic metal has an electrodeposited layer of nickel about 3 to 10 micrometers thick on at least one major surface.
• the outer portion of that at least one major surface comprises a layer of electroplated gold or a gold alloy containing up to about 1% total nickel and/or cobalt about 0.1 to about 2 micrometers thick which layer of elec­troplated gold or gold alloy is heat bonded to the nickel so as to provide diffusion of nickel to the gold surface in an amount at or near the surface of about 1% to about 10% total nickel.
• the strip can be faced on all surfaces with gold or, on the two major surfaces, i.e. the top and bottom or on one major surface.
• Nickel and nickel-rich alloy strip can be made by conventional metallurgical melt technology wherein a charge of metal is melted, then cast and then hot- and/or cold-worked to strip form.
• a particularly advantageous method of making nickel, cobalt or nickel-rich alloy strip is to roll compact metal powder, sinter bond and interdiffuse the roll-compacted metal powder and thereafter or simultaneously roll the bonded powder product to strip form and thickness.
• Strip of metal other than nickel or nickel-rich alloy which can form the principal structural element of the connectors of the present invention is generally made in a conventional manner and is commercially available from many sources.
• the present invention contemplates use of commercially available strip of copper, brass, aluminium bronze, cupro-nickel, beryllium copper, copper-nickel-tin alloy and any other metal or other electrically conductive material useful in the electrical contact art.
• This strip is thoroughly cleaned by conventional means such as alkaline cleaning baths, solvent and vapor degreasing, etc. and then electroplated to provide a layer of nickel about 5 to about 10 micrometers thick.
• One of the electroplating baths set forth in Electroplating Engineering Handbook, 3rd Ed., A. Kenneth Graham, Van Nostrand Reinhold Company, Copyright, 1971 at page 247 can be used to electroplate nickel.
• Gold is electrodeposited over either the nickel strip or plated nickel from a cyanide-type, citrate-type or other type of bath adapted to produce a pure soft gold electro-deposit.
• the strip is then heat treated at about 350°C to 600°C for times ranging from 2 hours to 10 seconds so as to diffuse nickel into the gold to reach a level of from 1 to 10% nickel at the gold outer surface.
• the electrical connector materials and electrical contacts made therefrom as contemplated in the present invention are advantageous with respect to contacts made of base metals in that they are and remain through their useful lives essentially free of corrosion products and thus give reliable, stable contact service.
• the contacts and contact materials of the present invention are advantageous when the contact must be broken periodically. In these situations, a pure gold surface becomes galled or roughened, gold-on-­gold contacting surfaces tend to sinter or fuse together and the contact cannot readily be separated.
• the present invention is based upon the discovery that when gold contacting surfaces contain 1 to 10% nickel such modified gold-on-modified gold contacts do not exhibit the fusing or sintering character of pure gold and thus the contacts can always be easily broken, provided of course, that the circuit including the contact has not been over­loaded beyond design capacity.
• heat treatment time will normally vary with temperatures such that longer times will be used at lower temperatures and vice versa with a given thickness of gold. Lower temperatures and shorter times at a given temperature will be employed with thinner gold layers than with thicker gold layers.
• diffusion of nickel into gold can be carried out simul­taneously with age-hardening of an age-hardenable substrate. Normally, this age-hardening of, for example, copper-base-­alloys such as beryllium copper or a copper-nickel-tin alloy or a copper-nickel aluminium alloy will be carried out after the contact material is in final form as an electrical contact.
• strip form of beryllium copper is blanked and shaped to contact con­figuration.
• the thus shaped contacts are then electroplated sequen­tially with nickel and gold and then heat treated at a temperature and time combination selected in consideration of the thickness of electroplated gold so as to achieve both age-hardening of the substrate and proper gold-nickel interdiffusion at the same time.
• contacts may be blanked out of composite gold-nickel-­copper beryllium strip, formed and then heat treated.
• the annealing heat treatment which produces diffusion of nickel and gold can be carried out simultaneously with hot rerolling of plated strip material.
• nickel strip made by roll compacting and then sintering and rolling nickel powder can be electroplated with gold and then rerolled at a temperature in the range of 350°C to 500°C to enhance the metallurgical bond between the nickel and gold and effectuate the diffusion of the nickel.
• the metallurgical bond and diffusion can be accomplished by the annealing heat treatment as described herein­before and the composite can be cold rolled either before or after annealing so as to enhance mechanical characteristics.
• a nickel strip made from roll compacted and sintered nickel powder about 0.5 mm thick, about 30 mm wide and about 70 meters long is thoroughly cleaned, mildly etched and electroplated with gold from a citrate-base electroplating bath to provide a uniform, pure gold deposit about 0.5 micrometer thick.
• the plated strip is thoroughly rinsed to remove any trace of electrolyte, dried and then heat treated by being passed through a furnace.
• the furnace is held at 480°C and contains an atmosphere of 10 volume percent hydrogen, balance nitrogen. Cool strip is fed to the furnace and passes through with a residence time of six minutes. As the strip exits the furnace it is cooled under the same reducing conditions and then coiled.
• the composite nickel-gold contact material made in this way gives excellent results in electric contact service composite material to composite material.
• the contacts exhibit essentially no detrimental behavior over time when exposed to normal service.
• the contacts do not corrode, gall or pit in service and can be disconnected hundreds of times without difficulty even when exposed in use to temperatures up to about 200°C.

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• 1987
  • 1987-12-02 CA CA000553333A patent/CA1331325C/en not_active Expired - Fee Related
• 1988
  • 1988-11-24 ES ES198888119564T patent/ES2034127T3/es not_active Expired - Lifetime
  • 1988-11-24 DE DE8888119564T patent/DE3874492T2/de not_active Expired - Fee Related
  • 1988-11-24 EP EP88119564A patent/EP0318831B1/de not_active Expired - Lifetime
  • 1988-11-24 AT AT88119564T patent/ATE80501T1/de not_active IP Right Cessation
  • 1988-12-01 JP JP63305126A patent/JPH067452B2/ja not_active Expired - Fee Related
• 1992
  • 1992-09-17 GR GR920402051T patent/GR3005728T3/el unknown

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