GB2169748A - Electrical contacts - Google Patents

Electrical contacts Download PDF

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Publication number
GB2169748A
GB2169748A GB08500723A GB8500723A GB2169748A GB 2169748 A GB2169748 A GB 2169748A GB 08500723 A GB08500723 A GB 08500723A GB 8500723 A GB8500723 A GB 8500723A GB 2169748 A GB2169748 A GB 2169748A
Authority
GB
United Kingdom
Prior art keywords
contact
base metal
ruthenium
powder
ruthenium powder
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.)
Granted
Application number
GB08500723A
Other versions
GB8500723D0 (en
GB2169748B (en
Inventor
Wilbert Ridd George
Kenneth George Snowdon
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.)
STC PLC
Original Assignee
STC 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 STC PLC filed Critical STC PLC
Priority to GB08500723A priority Critical patent/GB2169748B/en
Publication of GB8500723D0 publication Critical patent/GB8500723D0/en
Publication of GB2169748A publication Critical patent/GB2169748A/en
Application granted granted Critical
Publication of GB2169748B publication Critical patent/GB2169748B/en
Expired legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C26/00—Coating not provided for in groups C23C2/00 - C23C24/00
    • C23C26/02—Coating not provided for in groups C23C2/00 - C23C24/00 applying molten material to the substrate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/24—Selection of soldering or welding materials proper
    • B23K35/32—Selection of soldering or welding materials proper with the principal constituent melting at more than 1550 degrees C
    • B23K35/322—Selection of soldering or welding materials proper with the principal constituent melting at more than 1550 degrees C a Pt-group metal as principal constituent
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/02—Contacts characterised by the material thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H11/00—Apparatus or processes specially adapted for the manufacture of electric switches
    • H01H11/04—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts
    • H01H11/041—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts by bonding of a contact marking face to a contact body portion

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Contacts (AREA)
  • Manufacture Of Switches (AREA)

Abstract

Ruthenium powder 13 is applied to the surface of a base metal electrical contact 11. The contact is exposed to laser radiation to fuse the base metal surface and adhere the ruthenium power thereto. <IMAGE>

Description

SPECIFICATION Electrical contacts This invention relates to electrical contacts, e.g. for switches or relays.
Electrical contacts generally suffer a reduction in performance with extensive use. Thus, for example, a large number of switching operations can result in contact burning or erosion leading to a high contact resistance. Attempts have been made to overcome this problem by the use of precious metals to form the contacts but this is of course relatively costly. In particular ruthenium has the combined properties of high electrical conductivity and high wear resistance. However, ruthenium has a low natural solubility in the base metals, typically copper, conventionally employed in contact manufacture. It has been proposed to manufacture ruthenium containing contacts by pressing and sintering a mixture of copper and ruthenium powders followed by surface etching to remove some of the copper and expose the ruthenium.Such a contact however is relatively costly both in materials and in manufacture.
The object of the present invention is to minimise or to overcome this disadvantage.
According to one aspect of the invention there is provided a switch or relay contact comprising a base metal contact, the contact surface of which is provided with an adherent ruthenium powder coating.
According to another aspect of the invention there is provided a method of manufacturing an electrical contact, the method including providing a base metal contact surface, applying ruthenium powder to the surface, and fusing the base metal surface by exposure to laser radiation, thereby adhering the ruthenium powder to the surface.
An embodiment of the invention will now be described with reference to the accompanying drawing in which the single figure is a cross-sectional view of an electrical contact assembly.
Referring to the drawing, a base metal contact billet 11 supported e.g. on a contact carrier spring 12 is provided with a surface coating of ruthenium powder 13. Typically the powder is applied as a paste in an organic vehicle, e.g. methanol. At least the contact area of the coated contact is exposed to laser radiation to heat the ruthenium powder 13 and to fuse the base metal surface. When the surface resolidifies the ruthenium powder is adhered thereto. The low mutual solubility of ruthenium and base metals, e.g. copper, confines the precious metal to the surface. Any excess powder is readily removed to leave the finished contact. Since the ruthenium is confined to the contact surface only a small quantity of the precious metal is required and the materials cost is thus relatively low.
For the fusion process we prefer to employ a neodymium YAG laser operated in its welding mode. We have found that a combination of a spot diameter of 0.5 to 1 mm and a power output of 5 to 10 joules is adequate to effect fusion of the base metal surface. Typi cally we employ a laser pulse length of 1 to 10 ms.
It will be appreciated that other laser systems may also be employed. In each case it will of couse be necessary to choose a suitable combination of output power, spot diameter and pulse length to provide the optimum conditions required for fusing the base metal surface to effect adherence of the ruthenium powder. These conditions may readily be found by experiment and/or by calculation.
To prevent the risk of oxidation of the base metal surface during the fusion process we prefer to surround the contact during processing with an inert or reducing atmosphere. Typically forming gas (5% hydrogen, 95% nitrogen by volume) is used for this purpose.
The technique is not of course limited to carrier-mounted contacts but may also be employed with advantage on reed contact units.
1. A switch or relay contact comprising a base metal contact, the contact surface of which is provided with an adherent ruthenium powder coating.
2. A contact as claimed in claim 1, and comprising a base metal billet mounted on a contact carrier spring.
3. A contact as claimed in claim 1, and comprising a reed contact.
4. A switch or relay contact substantially as described herein with reference to the accompanying drawings.
5. A method of manufacturing an electrical contact, the method including providing a base metal contact surface, applying ruthenium powder to the surface, and fusing the base metal surface by exposure to laser radiation, thereby adhering the ruthenium powder to the surface.
6. A method as claimed in claim 5, wherein the base metal is copper.
7. A method as claimed in claim 5 or 6, wherein the ruthenium powder is applied to the base metal surface as a paste in an organic vehicle.
8. A method as claimed in claim 7, wherein the organic vehicle is methanol.
9. A method as claimed in any one of claims 5 to 8, wherein the base metal surface is surrounded by an inert or reducing atmosphere.
10. A method as claimed in claim 9, wherein the atmosphere comprises forming gas.
11. A method or manufacturing an electrical contact substantially as described herein with reference to the accompanying drawings.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Electrical contacts This invention relates to electrical contacts, e.g. for switches or relays. Electrical contacts generally suffer a reduction in performance with extensive use. Thus, for example, a large number of switching operations can result in contact burning or erosion leading to a high contact resistance. Attempts have been made to overcome this problem by the use of precious metals to form the contacts but this is of course relatively costly. In particular ruthenium has the combined properties of high electrical conductivity and high wear resistance. However, ruthenium has a low natural solubility in the base metals, typically copper, conventionally employed in contact manufacture. It has been proposed to manufacture ruthenium containing contacts by pressing and sintering a mixture of copper and ruthenium powders followed by surface etching to remove some of the copper and expose the ruthenium.Such a contact however is relatively costly both in materials and in manufacture. The object of the present invention is to minimise or to overcome this disadvantage. According to one aspect of the invention there is provided a switch or relay contact comprising a base metal contact, the contact surface of which is provided with an adherent ruthenium powder coating. According to another aspect of the invention there is provided a method of manufacturing an electrical contact, the method including providing a base metal contact surface, applying ruthenium powder to the surface, and fusing the base metal surface by exposure to laser radiation, thereby adhering the ruthenium powder to the surface. An embodiment of the invention will now be described with reference to the accompanying drawing in which the single figure is a cross-sectional view of an electrical contact assembly. Referring to the drawing, a base metal contact billet 11 supported e.g. on a contact carrier spring 12 is provided with a surface coating of ruthenium powder 13. Typically the powder is applied as a paste in an organic vehicle, e.g. methanol. At least the contact area of the coated contact is exposed to laser radiation to heat the ruthenium powder 13 and to fuse the base metal surface. When the surface resolidifies the ruthenium powder is adhered thereto. The low mutual solubility of ruthenium and base metals, e.g. copper, confines the precious metal to the surface. Any excess powder is readily removed to leave the finished contact. Since the ruthenium is confined to the contact surface only a small quantity of the precious metal is required and the materials cost is thus relatively low. For the fusion process we prefer to employ a neodymium YAG laser operated in its welding mode. We have found that a combination of a spot diameter of 0.5 to 1 mm and a power output of 5 to 10 joules is adequate to effect fusion of the base metal surface. Typi cally we employ a laser pulse length of 1 to 10 ms. It will be appreciated that other laser systems may also be employed. In each case it will of couse be necessary to choose a suitable combination of output power, spot diameter and pulse length to provide the optimum conditions required for fusing the base metal surface to effect adherence of the ruthenium powder. These conditions may readily be found by experiment and/or by calculation. To prevent the risk of oxidation of the base metal surface during the fusion process we prefer to surround the contact during processing with an inert or reducing atmosphere. Typically forming gas (5% hydrogen, 95% nitrogen by volume) is used for this purpose. The technique is not of course limited to carrier-mounted contacts but may also be employed with advantage on reed contact units. CLAIMS
1. A switch or relay contact comprising a base metal contact, the contact surface of which is provided with an adherent ruthenium powder coating.
2. A contact as claimed in claim 1, and comprising a base metal billet mounted on a contact carrier spring.
3. A contact as claimed in claim 1, and comprising a reed contact.
4. A switch or relay contact substantially as described herein with reference to the accompanying drawings.
5. A method of manufacturing an electrical contact, the method including providing a base metal contact surface, applying ruthenium powder to the surface, and fusing the base metal surface by exposure to laser radiation, thereby adhering the ruthenium powder to the surface.
6. A method as claimed in claim 5, wherein the base metal is copper.
7. A method as claimed in claim 5 or 6, wherein the ruthenium powder is applied to the base metal surface as a paste in an organic vehicle.
8. A method as claimed in claim 7, wherein the organic vehicle is methanol.
9. A method as claimed in any one of claims 5 to 8, wherein the base metal surface is surrounded by an inert or reducing atmosphere.
10. A method as claimed in claim 9, wherein the atmosphere comprises forming gas.
11. A method or manufacturing an electrical contact substantially as described herein with reference to the accompanying drawings.
GB08500723A 1985-01-11 1985-01-11 Electrical contacts Expired GB2169748B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08500723A GB2169748B (en) 1985-01-11 1985-01-11 Electrical contacts

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB08500723A GB2169748B (en) 1985-01-11 1985-01-11 Electrical contacts

Publications (3)

Publication Number Publication Date
GB8500723D0 GB8500723D0 (en) 1985-02-13
GB2169748A true GB2169748A (en) 1986-07-16
GB2169748B GB2169748B (en) 1988-07-27

Family

ID=10572721

Family Applications (1)

Application Number Title Priority Date Filing Date
GB08500723A Expired GB2169748B (en) 1985-01-11 1985-01-11 Electrical contacts

Country Status (1)

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GB (1) GB2169748B (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5315758A (en) * 1990-10-31 1994-05-31 Alps Electric Co., Ltd. Method for manufacturing slide electrical contact
EP2260966A1 (en) * 2009-06-12 2010-12-15 Sitec Industrietechnologie GmbH Method for partial connection using laser beam of components with pasty meltable materials

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2094570A (en) * 1936-07-01 1937-09-28 Western Union Telegraph Co Electric contact
GB501379A (en) * 1937-11-06 1939-02-27 Frederick Richard Simms Improvements in or relating to composite metals, more particularly for electric contacts, and processes of making them
GB893365A (en) * 1958-12-31 1962-04-11 Ericsson Telephones Ltd Improvements in or relating to contact electrodes
GB1451124A (en) * 1973-05-09 1976-09-29 Philips Electronic Associated Electric switching device having contacts
GB1457835A (en) * 1974-01-07 1976-12-08 Avco Everett Res Lab Inc Formation of surface layer casings on articles
GB2071703A (en) * 1980-02-15 1981-09-23 Rau Gmbh G Contact element and process for producing the same
EP0036226A1 (en) * 1980-03-17 1981-09-23 Koninklijke Philips Electronics N.V. Electric connecting means
GB2113720A (en) * 1982-01-07 1983-08-10 Standard Telephones Cables Ltd Fabricating solder tracks

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2094570A (en) * 1936-07-01 1937-09-28 Western Union Telegraph Co Electric contact
GB501379A (en) * 1937-11-06 1939-02-27 Frederick Richard Simms Improvements in or relating to composite metals, more particularly for electric contacts, and processes of making them
GB893365A (en) * 1958-12-31 1962-04-11 Ericsson Telephones Ltd Improvements in or relating to contact electrodes
GB1451124A (en) * 1973-05-09 1976-09-29 Philips Electronic Associated Electric switching device having contacts
GB1457835A (en) * 1974-01-07 1976-12-08 Avco Everett Res Lab Inc Formation of surface layer casings on articles
GB2071703A (en) * 1980-02-15 1981-09-23 Rau Gmbh G Contact element and process for producing the same
EP0036226A1 (en) * 1980-03-17 1981-09-23 Koninklijke Philips Electronics N.V. Electric connecting means
GB2113720A (en) * 1982-01-07 1983-08-10 Standard Telephones Cables Ltd Fabricating solder tracks

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5315758A (en) * 1990-10-31 1994-05-31 Alps Electric Co., Ltd. Method for manufacturing slide electrical contact
EP2260966A1 (en) * 2009-06-12 2010-12-15 Sitec Industrietechnologie GmbH Method for partial connection using laser beam of components with pasty meltable materials

Also Published As

Publication number Publication date
GB8500723D0 (en) 1985-02-13
GB2169748B (en) 1988-07-27

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PCNP Patent ceased through non-payment of renewal fee