Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D7/00—Electroplating characterised by the article coated
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/10—Electroplating with more than one layer of the same or of different metals
  • C25D5/12—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/60—Electroplating characterised by the structure or texture of the layers
  • C25D5/623—Porosity of the layers
• • 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

• This invention relates to an electrical contact surface coating. It relates particularly to a process for providing a surface coating on an electrical contact body which will have good corrosion and wear resistance properties.
• contact bodies which are capable of making good electrical contact with one another and will be able to do this even after the contact surfaces have been exposed to atmospheric conditions likely to cause surface corrosion of the bodies.
• the products of any surface corrosion are likely to include the formation of an electrically insulating film on the contact body and the occurence of this will cause an unacceptably high electrical resistance between a pair of the contact surfaces.
• the contact bodies may need to be brought into contact with one another very many times over the lifetime of the equipment so that the contact-making surface will need to be resistant to mechanical wear.
• a process for forming an electrically conductive surface coating on an electrical contact body comprising the steps of depositing upon the body surface in sequence (a) a nickel layer, (b) a first gold layer, (c) a palladium/nickel alloy layer which may be an alloy containing nickel up to a proportion of 50% by weight, and (d) a second gold layer.
• the separate layers are laid down by an electro-deposition process such as electroplating.
• the nickel layer may be laid down so as to give a deposit of pure, soft, low stress nickel.
• the relevant plating bath should be free of organic impurities and traces of metals other than nickel.
• the first gold layer may be deposited from a conventional commercially available gold plating solution. A gold thickness of between 0.05 to 0.1 micrometres is laid down.
• the palladium/nickel alloy layer may be deposited from a conventional commercial electroplating solution. The composition of the layer is satisfactory with palladium in the range of 50 to 100% by weight, balance nickel.
• the second gold layer may be a pure gold metal or one containing metal hardening additives, such as cobalt, nickel
• One preferred composition for the second gold layer is similar to that used for the said first gold layer.
• the invention also comprises an electrical contact body when manufactured with an electrically conductive surface coating having layers deposited in sequence of nickel, gold, palladium/nickel alloy and gold.
• the electrical contact body may be intended for use in applications such as electrical and electronic connector contacts, sliding contacts for electrical slip-rings and for printed circuit boards.
• an electrical contact body 1 after suitable cleaning and possibly a surface smoothing treatment is passed through a first electroplating bath 2 where it is given a coating of a pure, soft, low stress nickel deposit.
• the nickel plating solution composition should be free of organic impurities and traces of metals other than nickel.
• the nickel plating solution may have been given a preliminary carbon treatment to remove organic impurities and been subject to a low current plating-out stage to remove any metal
• the nickel plating solution should therefore preferably contain only nickel salts and possibly an additive such as boric acid.
• the thickness of nickel deposited is within the range of 0.5 to 3.0 micrometres.
• the contact body After deposition of the nickel layer, the contact body is washed and it is then passed through a second electroplating bath 3 for the formation of a gold layer.
• the gold plating solution was a conventional commercial gold plating solution and a thickness of gold of between 0.05 and 0.1 micrometres was formed.
• One gold plating solution that was found to be particularly suitable was that produced by Degussa (West Germany) under the name of "Auruna 553 Solution".
• the object of the nickel coating followed by the gold coating was partly to promote the formation of a low porosity coating in the palladium/nickel alloy layer that was to be applied subsequently and thus the gold enhanced the eventual corrosion resistance.
• the nickel and gold coatings served to reduce the possibility of a chemical contamination of the palladium/nickel electroplating solution used in the next stage by the accidental dissolution of metals such as copper, zinc or lead from the substrate material.
• the contact body 1 is washed and it is then passed through a third electroplating bath 4 for the formation of a palladium/nickel alloy layer.
• the palladium/nickel alloy deposition bath was a commercially available bath selected from a group comprising: Degussa (West Germany) - "Palladium Nickel 462 Solution”, Englehard Industries - “Palnic Solution”, Lea Ronal - “Pallamet 30 Solution” and Sel-Rex (Oxymetal Industries) - "Palladex Solution”.
• the conditions of deposition used were those recommended by the supplier of the relevant electroplating solution.
• the composition of the palladium/nickel alloy layer was found to be satisfactory with palladium in the range of 50 to 100% by weight, balance nickel.
• the contact body is washed and it is then passed through a fourth electroplating bath 5 to be given a thin plating of gold.
• the object of this step was to give a satisfactory wear resistance to the completed contact body and the type of gold deposit laid down was not found to be critical.
• the type of gold used may be either a pure gold metal or one containing metal-hardening additives, such as cobalt, nickel or iron in an amount of approximately 0.2 to 0.5% by weight.
• a particularly suitable gold deposition bath 5 for the second gold layer is a similar bath to that used for the first gold layer.
• the coating was found to have improved corrosion resistance and good wear resistance properties as compared with an electrical contact body having a conventional surface coating.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating Methods And Accessories (AREA)
• Contacts (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (3)

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• 1986
  • 1986-02-17 GB GB8603900A patent/GB2186597B/en not_active Expired - Lifetime
• 1987
  • 1987-02-17 EP EP87901534A patent/EP0258365A1/de not_active Ceased
  • 1987-02-17 WO PCT/GB1987/000114 patent/WO1987005057A1/en not_active Application Discontinuation

Non-Patent Citations (1)

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