EP0082647A2 - Korrosionsbeständige Schwachstromkontakte - Google Patents

Korrosionsbeständige Schwachstromkontakte Download PDF

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Publication number
EP0082647A2
EP0082647A2 EP82306608A EP82306608A EP0082647A2 EP 0082647 A2 EP0082647 A2 EP 0082647A2 EP 82306608 A EP82306608 A EP 82306608A EP 82306608 A EP82306608 A EP 82306608A EP 0082647 A2 EP0082647 A2 EP 0082647A2
Authority
EP
European Patent Office
Prior art keywords
inlay
alloy
inlays
base metal
body according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP82306608A
Other languages
English (en)
French (fr)
Other versions
EP0082647A3 (de
Inventor
David James Anderton
Stephen Munn
John Whitmarsh
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Johnson Matthey PLC
Original Assignee
Johnson Matthey PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Johnson Matthey PLC filed Critical Johnson Matthey PLC
Publication of EP0082647A2 publication Critical patent/EP0082647A2/de
Publication of EP0082647A3 publication Critical patent/EP0082647A3/de
Ceased legal-status Critical Current

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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

  • This invention relates to metal or alloy bodies comprising one or more corrosion resistant inlays.
  • the invention is particularly concerned with bodies of this type from which corrosion resistant electrical contact elements may be fabricated, and with electrical contact elements fabricated from such bodies.
  • electrical contact element both here and throughout the remainder of this specification is meant an electrically conductive body which carries at least one layer of electrically conductive material and/or which embodies at least one region of such material, the or each layer and/or region constituting an electrical contact zone.
  • electrically conductive body is formed from a sheet of lamina of metal or alloy by pressing or stamping.
  • the said sheet or lamina may be inlaid with the metal or alloy which will constitute the electrical contact zon(s).
  • the surface of the sheet or lamina or one or more regions thereof may be coated with contact zone metal or alloy.
  • electrical contact zone both here and throughout' the remainder of this specification is meant a part of the said electrically conductive body which is mechanically adapted to make contact with and thereby establish electrical connection with a similar zone of another electrical contact element or with some other electrically conductive body of suitable configuration.
  • corrosion resistant electrical contact elements both here and throughout the remainder of this specification is meant electrical contact elements as herein defined in which at least the electrical contact zones are corrosion resistant.
  • electrical contact elements are sometimes referred to as “contact elements” and even, on occasions, simply as “contacts”.
  • electrical contact zones are sometimes referred to as “contact zones” and also, on occasions, simply as “contacts”.
  • the electrically conductive body referred to in the above definition of an electrical contact element is frequently in the form of a resilient, elongate arm, and, in one fairly common form of electrical contact element, the arm is of phosphor bronze with, towards the end, a contact zone comprising a layer of electrically conductive, corrosion resistant metal or alloy applied to the material of the arm.
  • the arm is slightly deformed at the contact zone end so that the effective part of the contact zone is a portion of a hemispherical or part spherical hollow bulge in the arm.
  • the contact zone end of the arm is deformed into a hollow semi-cylindrical or part cylindrical shape so that the effective part of the contact zone lies on the outer curved surface of the cylindrical or part cylindrical portion.
  • Two contact elements of the type just described are often joined together to form an opposed contact pair and electrical connection is established between them and, for example, a metal tongue by sliding the tongue between the contacts so that each arm is displaced slightly with the result that each contact bears against the tongue.
  • the two arms are formed from a single piece of metal or alloy.
  • the two arms with their associated contact zon:s may together be taken as constituting a single electrical contact element.
  • the actual degree of corrosion resistance, on the one hand, and resistance to mechanical wear, on the other, which contact zones may be required to exhibit, will depend 5upon such factors as the atmosphere in which the contacts operate, the contact pressure, the frequency of make and break and the nature of the contact action, that is, whether the contacts concerned make sliding or butting contact.
  • the present invention is especially concerned with light duty contacts or, more particularly, with contact elements for use in such applications as light duty, high reliability "professional" connectors of the type that are employed in computers and similar equipment, although the invention is, of course, by no means so limited.
  • Such contacts carry currents of less than 1 amp and under these conditions the effects of corrosion can be very marked indeed. It is therefore important to make light duty contacts of the type just referred to as corrosion resistant as is economically practicable. At the same time. such contacts are often required to remain in service for long periods, sometimes for as long as 30 years. It is therefore equally important that they should also be made as wear resistant as possible.
  • contacts subject to stringent corrosion resistance and mechanical wear requirements are those for use, inter alia, in edge connectors for printed circuit boards and in pushbutton and keyboard switches.
  • Contacts of the above type or, more specifically, the contact zone of contact elements for use in equipment of the above type have often, in the past, been made corrosion resistant by applying to them a layer of about 5 microns thick of a gold alloy such as a 98% gold/cobalt alloy.
  • German Patent specification 1089491 proposes alleys containing 5 - 65% palladium, 15-55% silver and 15-70% gold for use as contact material in low current electrical contacts. These alloys are said to be highly resistant to surface corrosion in sulphur containing atmospheres and upon exposure to atmospheric components and chemicals present in equipment in which switchings installations are located whereby low contact resistance can be maintained.
  • Alloys which have been used for inlays include a 75 Au/25 Ag alloy. This ally, however, is still rather expensive in view of its relatively high gold content. Further, inlays of this alloy in base metal bodies such as those made from phosphor bronze and other copper containing alloys, for example, are prone to an effect known as "edge creep". This is a corrosion effect in which a thin layer or film of corrosion products creeps over the surface of the precious metal inlay from the boundary between the material of the inlay and that of the inlaid body. This seems to be a self-stabilising process in that the developing film of corrosion products tends progressively to inhibit the passage of further corrosion products from the boundary and thus progressively to slow down the development of the film until its development comes practically to a stop.
  • Edge creep i.e. the corrosion effect arising as a result of the intimate juxtaposition of the inlay and the base metal or alloy body and at the boundary thereof, is unrelated to the more usual atmospheric corrosion affecting the contact resistance of a contact surface.
  • metals or alloys which exhibit good intrinsic anti-corrosive properties are often unsuitable or unsatisfactory for use as inlays in that they are prone to edge creep.
  • One prime example of this is pure gold which has excellent intrinsic anti-corrosive properties.
  • One object of the present invention is to provide inlaid bodies from which contact elements comprising inlaid contact zones may be fabricated, the resulting contact elements being less expensive than known contact elements in which the contact zones are provided by inlaid alloys having a relatively high gold content (such as 75 Au/25.Ag) and having contact zones which are less prone to edge creep effects and at least as resistant to mechanical wear and surface corrosion as the contact zones )f known contact elements.
  • inlaid alloys having a relatively high gold content (such as 75 Au/25.Ag) and having contact zones which are less prone to edge creep effects and at least as resistant to mechanical wear and surface corrosion as the contact zones )f known contact elements.
  • an inlaid base metal or base metal alloy body from which may be fabricated electrical contact elements (as herein defined) in which the contact zones (as herein defined) are constituted by the inlay or inlays or portions thereof, the said inlay or inlays being formed from one or more alloys consisting of, apart from im p urites, gold, silver and one or more platinum group metals, with, optionally minor proportions of one or more of the metals copper, nickel and indium and of any platinum group metals which are not otherwise present.
  • the surfaces of the recess or recesses may be coated with nickel prior to insertion of the inlay bodies.
  • the invention also includes electrical contact elements fabricated from one or more inlaid bodies of the type just referred to.
  • Tests will now be described which we have carried out to determine the resistance of the inlaid portions of bodies according to the invention - (a) to corrosion, (b) to the edge creep effect,and (c) to mechanical wear.
  • the tests have also been carried out on similar bodies in which the inlaid portions are formed from the 75 Au/25 Ag alloy which is used to form the inlaid contact zones in certain prior art electrical contact elements. As will be seen, the results of the tests clearly illustrate the effectiveness of our invention.
  • one or more inlaid phosphor bronze bodies were first prepared and subjected to accelerated environmental tests for periods of 2-6 weeks in steps of 2 weeks.- On completion of each test, or of one or more of the 2 weeks stages of each test, an indication of the resulting corrosion of the inlay surface was obtained by measuring the contact resistance of each inlay under controlled conditions. The extent of the edge creep corrosion was then determined by direct measurement. Finally, the wear resistance of the alloys used for the inlays cf selected bodies was estimated by a method which is described laser.
  • test procedures Details of the test procedures are as follows. Alloys from which inlays were to be produced were induction melted and cold rolled to produce fine-grained homogeneous material from which test coupons were prepared. The surface of each alloy sample was highly polished to give maximum initial values of contact resistance of less than 5m ⁇ .Inlaid bodies were then produced by hot bonding the test alloy coupons into pre-grooved phosphor bronze strips and cold rolling the composites to around 60% reduction.
  • Accelerated corrosion tests were next carried out by exposing the inlaid bodies either to an atmosphere containing 100 ppb SO 2 , 20 ppb C1 2 and 150 ppb N0 2 or to an atmosphere containing 100 ppb H Z S, 100 ppb SO 2 , 20 ppb Cl 2 and 150 ppb N0 2 .
  • the second atmosphere is the first atmosphere with the addition of 100 ppb H Z S, the two atmospheres representing different levels of severity in corrosion tests.
  • the exposures were carried out at temperatures and relative humidities of 30+1 C and 75+3% respectively and the inlaid bodies were exposed for one of more periods of 2 weeks up to a maximum of 6 weeks.
  • the contact resistance of each inlay after the exposure of the inlaid body in the test chamber was determined at 100 equidistant points along the inlay by means of computer controlled contact resistance apparatus which automatically calculated and displayed the resistant values.
  • a polished, hemispherical gold probe 1.5 mm in diameter was pressed onto each inlay with a force of 100 grams weight and a current of 10 mA was then passed between the probe and the inlay in each direction consecutively.
  • the contact resistance was determined from the voltage drop between the probe end the inlay.
  • the wear resistances of two alloys which were used to form the inlays of bodies according to the invention and of the 75 Au/25 Ag alloy which is used to form the inlaid contact zones of certain prior art contact elements were determined by measuring the dimensions of the wear tracks produced by a rotating alloy disc rubbing against a flat sheet of the same material.
  • edge creep results in the accompanying Figure show that most of the Au/Ag/Pd alloys tested as well as those with minor additions of copper, indium or nickel, offered edge creep resistance superior to those of the prior art 75 Au/25 Ag alloy inlays.
  • Electrical contact elements suitable for use in edge connectors and the like may be fabricated from the inlaid bodies of the type used for the foregoing tests by, for example, rolling the bodies down to the required thickness, with intermediate appeals if necessary, and then stamping out from the resulting sheets either the contact elements per se or blanks from which the contact elements may be formed by one or more additional operations.
  • the invention is in no way limited to bodies with corrosion resistant inlays from which contact elemerts of the type just described may be made. Indeed, inlaid bodies according to the invention may be used to form articles other than contact elements for use in applications in which the corrosion resistance of the inlays is a desirable feature. Alternatively, the bodies may themselves be used unchanged in such applications.
EP82306608A 1981-12-10 1982-12-10 Korrosionsbeständige Schwachstromkontakte Ceased EP0082647A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8137209 1981-12-10
GB8137209 1981-12-10

Publications (2)

Publication Number Publication Date
EP0082647A2 true EP0082647A2 (de) 1983-06-29
EP0082647A3 EP0082647A3 (de) 1983-07-27

Family

ID=10526505

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82306608A Ceased EP0082647A3 (de) 1981-12-10 1982-12-10 Korrosionsbeständige Schwachstromkontakte

Country Status (3)

Country Link
EP (1) EP0082647A3 (de)
JP (1) JPS58502154A (de)
WO (1) WO1983002195A1 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3420231C1 (de) * 1984-05-30 1985-01-03 Degussa Ag, 6000 Frankfurt Silberreiche Werkstoffe fuer Schwachstromkontakte
EP1041591A2 (de) * 1999-03-29 2000-10-04 Nec Corporation Verbesserte elektrische Kontaktstruktur und diesen verwendende Relais oder Schalter

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2226944A (en) * 1938-10-27 1940-12-31 Bell Telephone Labor Inc Method of bonding dissimilar metals
DE1078774B (de) * 1954-03-02 1960-03-31 Western Electric Co Elektrischer Kontakt
DE2540956A1 (de) * 1975-09-13 1977-04-07 Heraeus Gmbh W C Goldlegierung als werkstoff fuer elektrische kontakte
DE2637807A1 (de) * 1976-08-21 1978-02-23 Heraeus Gmbh W C Gold-legierung fuer elektrische kontakte
EP0027520A1 (de) * 1979-10-08 1981-04-29 W.C. Heraeus GmbH Elektrischer Schwachstromkontakt

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2226944A (en) * 1938-10-27 1940-12-31 Bell Telephone Labor Inc Method of bonding dissimilar metals
DE1078774B (de) * 1954-03-02 1960-03-31 Western Electric Co Elektrischer Kontakt
DE2540956A1 (de) * 1975-09-13 1977-04-07 Heraeus Gmbh W C Goldlegierung als werkstoff fuer elektrische kontakte
DE2637807A1 (de) * 1976-08-21 1978-02-23 Heraeus Gmbh W C Gold-legierung fuer elektrische kontakte
EP0027520A1 (de) * 1979-10-08 1981-04-29 W.C. Heraeus GmbH Elektrischer Schwachstromkontakt

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3420231C1 (de) * 1984-05-30 1985-01-03 Degussa Ag, 6000 Frankfurt Silberreiche Werkstoffe fuer Schwachstromkontakte
EP0163904A2 (de) * 1984-05-30 1985-12-11 INOVAN GmbH & Co. KG Metalle und Bauelemente Silberreiche Werkstoffe für Schwachstromkontakte
EP0163904A3 (en) * 1984-05-30 1986-12-30 Degussa Aktiengesellschaft Argentiferous material for weak current contacts
EP1041591A2 (de) * 1999-03-29 2000-10-04 Nec Corporation Verbesserte elektrische Kontaktstruktur und diesen verwendende Relais oder Schalter
EP1041591A3 (de) * 1999-03-29 2002-07-10 Nec Corporation Verbesserte elektrische Kontaktstruktur und diesen verwendende Relais oder Schalter

Also Published As

Publication number Publication date
EP0082647A3 (de) 1983-07-27
WO1983002195A1 (en) 1983-06-23
JPS58502154A (ja) 1983-12-15

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Inventor name: ANDERTON, DAVID JAMES

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Inventor name: MUNN, STEPHEN