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
• • 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
  • C25D5/48—After-treatment of electroplated surfaces
  • C25D5/50—After-treatment of electroplated surfaces by heat-treatment
• • 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 invention is concerned with electrical contact pieces for lifting contacts, plug contacts and sliding or sliding contacts which are coated with noble metal over a 0.1 ⁇ m to 10 ⁇ m thick intermediate layer made of chrome on a metallic contact piece blank melting below approximately 2000 ° C., and with processes for their manufacture.
• the coating of contact pieces at least on their contacting side with precious metals or precious metal alloys is known and is carried out for various reasons, namely to reduce the contact resistance and / or to protect the contact surface against oxidation and corrosion and / or to improve the wear behavior compared to the base base material etc.
• the thinnest possible coating is desirable, but the thickness of the precious metal should not be less than a certain minimum, because otherwise the sufficiently low contact resistance and the oxidation and corrosion resistance of the carrier material are not guaranteed.
• the noble metal layers are a few ⁇ m up to about 10 ⁇ m thick.
• the mechanical properties of the noble metal layers are by no means always up to the demands made per se; Rather have a lack of hardness and lack Verschle 'ißfesttechnik, also lack in sliding and plug contacts abrasion resistance, in many cases a relatively short service life.
• a disadvantage of a coating of contact pieces with chrome is that high and, above all, fluctuating contact resistances are then recorded, which preclude its general use. These fluctuating contact resistances of chromium are probably due to surface oxidation processes that occur randomly and irregularly - especially under the influence of heat - and cannot be influenced in a targeted manner. The high and fluctuating contact resistances are particularly observed when the chromium is electrodeposited, but cannot be avoided even when the chromium is vapor-deposited. In addition, a cumbersome and considerably more expensive method must be used for a coating by vapor deposition. The advantage of chromium, which is cheaper than the precious metal, is more than offset by the inefficiency of vapor deposition. For the reasons mentioned above, chromium as a coating material has so far not been used in practice and has not been able to replace the usual thicker precious metal layers.
• the object of the invention is to reduce the high need for noble metal in the coating of electrical contact pieces of the type mentioned, while maintaining and combining the favorable contact resistance, the good adhesive strength and the known other advantages of the noble metals with improved wear resistance of the contact layer, but also to avoid the above-mentioned disadvantages of other materials and processes, such as mechanical sensitivity, fluctuating contact resistance or inefficiency.
• the noble metal is applied in a layer thickness of only 0.02 to 1.0 ⁇ m, preferably approximately 0.1 ⁇ m.
• the layer sequence despite the small amount of noble metal, has excellent etching resistance to nitric acid, hydrofluoric acid, acetic acid and phosphoric acid and mixtures thereof, so that the contact pieces can also be used where good etching resistance is important.
• the choice of basic materials for contact There are practically no limits to the number of pieces, since the usual contact materials that melt lower than at 2000 ° C can all be coated with chrome, if necessary after prior nickel plating, using the preferred method of galvanic coating for reasons of cost.
• the chrome layer should be chosen so thick that i.w. is tight. In the case of electrodeposited chrome layers, this is achieved with layer thicknesses from approx. 2 ⁇ m, with vapor-deposited chrome layers already with layer thicknesses from approx. 1 ⁇ m.
• the base materials for the contact pieces according to the invention are, above all, copper and alloys of Copper with silver, beryllium, tin (CuSn6), zinc (CuZn37) and others in question.
• Gold and gold alloys in particular high-quality gold alloys, also with smaller contents (up to 4 atom%) of nickel and / or cobalt, but also silver, platinum, palladium, rhodium and ruthenium, are suitable as precious metals.
• Contact pieces are preferably used in which the noble metal is distributed both on the surface of the chrome layer and to a substantial extent in the surface layer of the chrome layer.
• the latter is achieved through a targeted heat treatment, which allows the noble metal to diffuse partially into the chromium. This has a particularly favorable effect on the properties of the contact pieces according to the invention.
• the diffusion of the noble metal into the chrome surface presumably stabilizes it against undesired oxidation processes.
• the contact resistance is also reduced.
• the abrasion resistance of the precious metal layer is significantly improved.
• process step b) has proven beneficial to the process step b) at a current density of about 5-20 A / dm 2 at room temperature for a period of about 30 s and process step d) in solutions of sulfuric acid and nitric acid with or without the addition of phosphoric acid at room temperature for a period of time from 5 s to 60 s, preferably from 15 s. Furthermore, it is expedient in process step h) to surface the Cu-Be blank in hydrochloric acid at room temperature for a period of about 15 s to 2 min.
• the activated Cu-Be blank with chrome in a bath of 400 g Cr0 3 and 4 g H 2 S0 4 per liter at a current density of 15 A / dm 2 and at a temperature of 50 + 5 ° C during a Duration from 5 to 20 min.
• the chromium layer in 1- to 15% sulfuric acid, preferably 8% sulfuric acid, at a current density of 2 to 40 A / dm ', preferably 20 A / dm 2 , at room temperature for a period of 2 to 60 s, preferably 20s, to activate cathodically; according to n) to coat the activated chromium layer with gold in a weakly acidic to neutral gold bath at a covering current density of approximately 3 A / dm 2 at a temperature of approximately 25 ° C.
• the tempering also brings about a desired hardening of the copper-beryllium material.

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

Applications Claiming Priority (2)

Publications (2)

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Cited By (6)

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• 1982
  • 1982-04-22 DE DE19823214989 patent/DE3214989A1/de not_active Withdrawn
• 1983
  • 1983-04-16 EP EP83103703A patent/EP0092754A3/fr not_active Withdrawn

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