WO2005057732A1 - Tin alloy coating for contact purposes - Google Patents

Tin alloy coating for contact purposes Download PDF

Info

Publication number
WO2005057732A1
WO2005057732A1 PCT/FI2004/000745 FI2004000745W WO2005057732A1 WO 2005057732 A1 WO2005057732 A1 WO 2005057732A1 FI 2004000745 W FI2004000745 W FI 2004000745W WO 2005057732 A1 WO2005057732 A1 WO 2005057732A1
Authority
WO
WIPO (PCT)
Prior art keywords
tin
alloy
tin alloy
silver
alloy coating
Prior art date
Application number
PCT/FI2004/000745
Other languages
French (fr)
Inventor
Tag Hammam
Thomas Clark
Original Assignee
Outokumpu Copper Products Oy
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 Outokumpu Copper Products Oy filed Critical Outokumpu Copper Products Oy
Publication of WO2005057732A1 publication Critical patent/WO2005057732A1/en

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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
    • 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
    • B23K35/26—Selection of soldering or welding materials proper with the principal constituent melting at less than 400 degrees C
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C13/00—Alloys based on tin
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/02—Contacts characterised by the material thereof

Definitions

  • the invention relates to a tin alloy coating with at least one reducing agent to achieve an essentially oxide free metal-to-metal contact in electric contact purposes, such as in contact terminals.
  • a cold welded spot will restrict detrimental microsliding and wear during vibration. Moreover, a cold welded contact spot will prevent the ingress of air or moisture, which could cause corrosion. Provided that a cold-welded contact spot can be maintained the contact resistance will be low and stable during a long-term operation.
  • a reduced insertion force is achieved by using a low contact force in combination with a soft thin coating. It is desirable to increase the hardness of the coating by adding for instance silver in order to further reduce the insertion force and to extend the number of insertion and withdrawal before the coating is wear off.
  • the US patent application 2002096662 describes an electrically conducting metal strip comprising a base material made from copper or a copper alloy with a coating made from a tin-silver alloy containing 1 - 3,8 weight % silver. When manufacturing this strip an intermetallic phase is formed between the base material and the coating. Also the US patent application 2001055697 relates to a similar tin-silver alloy for coating of a base material from copper or a copper alloy. In this case the tin-silver alloy contains in addition to silver also 0,1 - 5 weight % indium. The addition of silver and indium achieves a higher hardness in a thinner coating.
  • the object of the present invention is to eliminate some drawbacks of the prior art and to achieve an improved tin alloy coating to achieve an essentially oxide free metal-to-metal contact in electric contact purposes by adding at least one reducing agent to the tin alloy coating.
  • the essential features of the invention are enlisted in the appended claims.
  • At least one reducing agent is added to a tin alloy coating of a connector to be used in electric contact purposes in order to achieve an essentially oxide free metal-to-metal contact in electric contact purposes.
  • This addition of the reducing agent improves the life-length of the connector because an oxide free metal-to-metal contact during the insertion is achieved.
  • the reducing agent will react with the possible residual oxygen, which is left at the contact interface.
  • the reducing agent also reduces an eventually formed surface oxide on the surface of the connector. Thus a thin oxide film is prevented to form at the interface during the insertion.
  • the reducing agent in accordance with the invention is preferably phosphorus and the amount of the added phosphorus is between 50 to 1000 ppm, preferably 100 to 250 ppm. Also other elements having a reducing effect as phosphorus for the tin alloy coating of the connector is used. Other possible elements as a reducing agent in the tin alloy coating of the invention are for instance lithium and boron. These reducing agents are added as such in the tin coating, but these reducing agents can be used as reducing agents with phosphorus.
  • the tin alloys which are suitable for the coating of the invention, are for instance tin-copper alloys, tin-bismuth alloys and tin-silver alloys.
  • One or two more metallic components can be advantageously added to the tin-silver alloys in addition with the reducing agent in order to achieve the reducing effect during the insertion of the contact between conductors.
  • the tin-silver alloys having one or two more metallic components are suitable for the coating of the invention.
  • the tin-silver alloys with one more component have a component from the group of bismuth, copper, indium and lead.
  • the desired alloys are thus tin-silver-bismuth, tin-silver-copper, tin-silver-indium and tin-silver-lead, which are also added by the reducing agent.
  • the tin-silver-bismuth alloy can further be advantageously alloyed by indium.
  • the alloy can further be advantageously alloyed by one of the elements from the group of bismuth, cobalt, indium and antimony.
  • the amount of silver in the tin-silver alloys for the invention is between 2 to 10 weight % silver, while the amount of copper in the tin-copper alloys for the invention is between 0,5 to 5 % by weight copper.
  • compositions of the tin silver alloys for the coating in accordance with the invention are for instance tin with 3,5 % by weight silver, tin with 3,2 % by weight silver and 0,8 % by weight copper as well as tin with 2,5 % by weight silver, 0,8 % by weight copper and 0,5 % by weight antimony.
  • reducing agent as phosphorus
  • a thin oxide film is prevented in a contact where a thin and harder coating can be used in combination with a low contact force. This can be done without affecting the possibility to achieve a good cold-welded contact spot.
  • Fig. 1 shows the contact voltage drop in fretting tests as a function of time.
  • the present invention to use phosphorus as a reducing doped additive in the tin - silver coating was tested in the fretting tests in a test bench, which consists of an electronic controlled shaker and a measurement system. Before the fretting tests all contacts were subjected to one long sliding stroke to wipe off the initial surface layer. During the fretting tests, the contacts were subjected to a vibration displacement stroke of 20 micrometer at a frequency of 100 Hz, and also a current loads of 2 A DC. The contact geometry was crossed cylinders with a diameter of 10 mm.
  • Fig. 1 the contact voltage drop was tested in fretting tests as a function of time. A normal load 13.9 N was applied. As shown the phosphorus added to the tin-silver restricts significant the increase in contact voltage drop. The observed enhanced performance of the phosphorus doped tin-silver sample was caused by the formation of a cold-welded contact spot.

Abstract

The invention relates to a tin alloy coating in a connector for electric contact purposes, such as in contact terminals. The tin alloy coating of the invention is alloyed with at least one reducing agent to achieve an essentially oxide free metal-to-metal contact.

Description

TIN ALLOY COATING FOR CONTACT PURPOSES
The invention relates to a tin alloy coating with at least one reducing agent to achieve an essentially oxide free metal-to-metal contact in electric contact purposes, such as in contact terminals.
The ultimate connection between two conductors is a welded joint. A cold welded spot will restrict detrimental microsliding and wear during vibration. Moreover, a cold welded contact spot will prevent the ingress of air or moisture, which could cause corrosion. Provided that a cold-welded contact spot can be maintained the contact resistance will be low and stable during a long-term operation.
With a soft coating such as tin, tin alloys or silver coatings, it is possible to achieve a cold welded contact spot during insertion. In order to achieve a cold welded contact spot it is of decisive importance to achieve an oxide-free metal- to-metal contact at the interface during insertion. A high contact force and a thick and soft coating will in general promote a cold welded contact spot, since any free space at the interface is restricted, and subsequently a gas-tight joint contact spot is achieved during insertion.
The trend with increasing number of contact terminals in a connector requires a reduced insertion force for each contact terminal. A reduced insertion force is achieved by using a low contact force in combination with a soft thin coating. It is desirable to increase the hardness of the coating by adding for instance silver in order to further reduce the insertion force and to extend the number of insertion and withdrawal before the coating is wear off.
The US patent application 2002096662 describes an electrically conducting metal strip comprising a base material made from copper or a copper alloy with a coating made from a tin-silver alloy containing 1 - 3,8 weight % silver. When manufacturing this strip an intermetallic phase is formed between the base material and the coating. Also the US patent application 2001055697 relates to a similar tin-silver alloy for coating of a base material from copper or a copper alloy. In this case the tin-silver alloy contains in addition to silver also 0,1 - 5 weight % indium. The addition of silver and indium achieves a higher hardness in a thinner coating.
With the higher hardness of the thin coating in combination with a low contact force will result in infinitesimal small spaces at the contact interface containing oxygen. This results oxides in a thin surface at parts of the contact interface, with a subsequently mechanical weak cold welded contact spot. This cold welded contact spot will easily be ruptured when subjected to cyclic mechanical stress, such as vibration.
The object of the present invention is to eliminate some drawbacks of the prior art and to achieve an improved tin alloy coating to achieve an essentially oxide free metal-to-metal contact in electric contact purposes by adding at least one reducing agent to the tin alloy coating. The essential features of the invention are enlisted in the appended claims.
According to the invention at least one reducing agent is added to a tin alloy coating of a connector to be used in electric contact purposes in order to achieve an essentially oxide free metal-to-metal contact in electric contact purposes. This addition of the reducing agent improves the life-length of the connector because an oxide free metal-to-metal contact during the insertion is achieved. The reducing agent will react with the possible residual oxygen, which is left at the contact interface. The reducing agent also reduces an eventually formed surface oxide on the surface of the connector. Thus a thin oxide film is prevented to form at the interface during the insertion.
The reducing agent in accordance with the invention is preferably phosphorus and the amount of the added phosphorus is between 50 to 1000 ppm, preferably 100 to 250 ppm. Also other elements having a reducing effect as phosphorus for the tin alloy coating of the connector is used. Other possible elements as a reducing agent in the tin alloy coating of the invention are for instance lithium and boron. These reducing agents are added as such in the tin coating, but these reducing agents can be used as reducing agents with phosphorus.
The tin alloys, which are suitable for the coating of the invention, are for instance tin-copper alloys, tin-bismuth alloys and tin-silver alloys. One or two more metallic components can be advantageously added to the tin-silver alloys in addition with the reducing agent in order to achieve the reducing effect during the insertion of the contact between conductors.
The tin-silver alloys having one or two more metallic components are suitable for the coating of the invention. The tin-silver alloys with one more component have a component from the group of bismuth, copper, indium and lead. The desired alloys are thus tin-silver-bismuth, tin-silver-copper, tin-silver-indium and tin-silver-lead, which are also added by the reducing agent.
The tin-silver-bismuth alloy can further be advantageously alloyed by indium. In case of the tin-silver-copper alloy the alloy can further be advantageously alloyed by one of the elements from the group of bismuth, cobalt, indium and antimony.
The amount of silver in the tin-silver alloys for the invention is between 2 to 10 weight % silver, while the amount of copper in the tin-copper alloys for the invention is between 0,5 to 5 % by weight copper.
The advantageous compositions of the tin silver alloys for the coating in accordance with the invention are for instance tin with 3,5 % by weight silver, tin with 3,2 % by weight silver and 0,8 % by weight copper as well as tin with 2,5 % by weight silver, 0,8 % by weight copper and 0,5 % by weight antimony. When using the reducing agent, as phosphorus, in the tin alloy coating for contact purposes a thin oxide film is prevented in a contact where a thin and harder coating can be used in combination with a low contact force. This can be done without affecting the possibility to achieve a good cold-welded contact spot.
The present invention will be illustrated in more details referring to the attached drawing, where
Fig. 1 shows the contact voltage drop in fretting tests as a function of time.
The present invention to use phosphorus as a reducing doped additive in the tin - silver coating was tested in the fretting tests in a test bench, which consists of an electronic controlled shaker and a measurement system. Before the fretting tests all contacts were subjected to one long sliding stroke to wipe off the initial surface layer. During the fretting tests, the contacts were subjected to a vibration displacement stroke of 20 micrometer at a frequency of 100 Hz, and also a current loads of 2 A DC. The contact geometry was crossed cylinders with a diameter of 10 mm.
In the test the samples constituted of solid rods of the present tin alloys, in order to avoid uncontrolled influence of the substrate material during fretting. Tin with 5% by weight silver with and without phosphorus were tested. The amount of phosphorus added to the tin-silver-phosphorus alloy was 0.025 % by weight.
According to Fig. 1 the contact voltage drop was tested in fretting tests as a function of time. A normal load 13.9 N was applied. As shown the phosphorus added to the tin-silver restricts significant the increase in contact voltage drop. The observed enhanced performance of the phosphorus doped tin-silver sample was caused by the formation of a cold-welded contact spot.

Claims

1. Tin alloy coating in a connector for electric contact purposes, such as in contact terminals, characterized in that the tin alloy coating is alloyed with at least one reducing agent to achieve an essentially oxide free metal-to-metal contact.
2. Tin alloy coating according to the claim 1 , characterized in that the reducing agent is phosphorus.
3. Tin alloy coating according to the claim 2, characterized in that the amount of phosphorus in the tin alloy is between 50 to 1000 ppm, preferably between 100 and 250 ppm.
4. Tin alloy coating according to the claim 1 , characterized in that the reducing agent is lithium.
5. Tin alloy coating according to the claim 1 , characterized in that the reducing agent is boron.
6. Tin alloy coating according to any of the preceding claims, characterized in that the tin alloy is a tin-silver alloy.
7. Tin alloy coating according to the claim 6, characterized in that the tin-silver alloy contains 2 to 10 % by weight silver.
8. Tin alloy coating according to the claim 6 or 7, characterized in that the tin alloy is a tin-silver-bismuth alloy.
9. Tin alloy coating according to the claim 6 or 7, characterized in that the tin alloy is a tin-silver-copper alloy.
10. Tin alloy coating according to the claim 6 or 7, characterized in that the tin alloy is a tin-silver-indium alloy.
11. Tin alloy coating according to the claim 6 or 7, characterized in that the tin alloy is a tin-silver-lead alloy.
12. Tin alloy coating according to any of the preceding claims 1 - 5, characterized in that the tin alloy is a tin-copper alloy.
13. Tin alloy coating according to the claims 12, characterized in that the tin- copper alloy contains 0,5 to 5 % by weight copper.
14. Tin alloy coating according to any of the preceding claims 1 - 5, characterized in that the tin alloy is a tin-bismuth alloy.
PCT/FI2004/000745 2003-12-09 2004-12-08 Tin alloy coating for contact purposes WO2005057732A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20031790A FI118873B (en) 2003-12-09 2003-12-09 Tin alloy coating for contact purposes
FI20031790 2003-12-09

Publications (1)

Publication Number Publication Date
WO2005057732A1 true WO2005057732A1 (en) 2005-06-23

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2528167A1 (en) * 2011-05-25 2012-11-28 Tyco Electronics AMP GmbH Electrical contact element with a cover layer having a chemical reducing agent, electrical contact arrangement and methods for manufacturing an electrical contact element and for reducing oxidization of a contact section of an electrical contact element
US8501088B2 (en) * 2007-07-25 2013-08-06 Nippon Steel & Sumikin Materials Co., Ltd. Solder alloy, solder ball and electronic member having solder bump

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5075176A (en) * 1990-02-23 1991-12-24 Stolberger Metallwerke Gmbh & Co. Kg Electrical connector pair
WO2003050920A1 (en) * 2001-12-13 2003-06-19 Outokumpu Oyj Contact terminal with doped coating

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5075176A (en) * 1990-02-23 1991-12-24 Stolberger Metallwerke Gmbh & Co. Kg Electrical connector pair
WO2003050920A1 (en) * 2001-12-13 2003-06-19 Outokumpu Oyj Contact terminal with doped coating

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8501088B2 (en) * 2007-07-25 2013-08-06 Nippon Steel & Sumikin Materials Co., Ltd. Solder alloy, solder ball and electronic member having solder bump
EP2528167A1 (en) * 2011-05-25 2012-11-28 Tyco Electronics AMP GmbH Electrical contact element with a cover layer having a chemical reducing agent, electrical contact arrangement and methods for manufacturing an electrical contact element and for reducing oxidization of a contact section of an electrical contact element
WO2012159917A1 (en) * 2011-05-25 2012-11-29 Tyco Electronics Amp Gmbh Electrical contact element with a cover layer having a chemical reducing agent, electrical contact arrangement and methods for manufacturing an electrical contact element and for reducing oxidization of a contact section of an electrical contact element
CN103563180A (en) * 2011-05-25 2014-02-05 泰科电子Amp有限责任公司 Electrical contact element with cover layer having chemical reducing agent, electrical contact arrangement and methods for manufacturing electrical contact element and for reducing oxidization of contact section of electrical contact element
US9312049B2 (en) 2011-05-25 2016-04-12 Te Connectivity Germany Gmbh Electrical contact element with a cover layer having a chemical reducing agent, electrical contact arrangement and methods for manufacturing an electrical contact element and for reducing oxidization of a contact section of an electrical contact element
CN103563180B (en) * 2011-05-25 2016-06-01 泰连德国有限公司 Have the electrical contact member of the cover layer with chemical reducing agent, electrical contact is arranged and for manufacturing electrical contact member and reducing the method that the contact site of electrical contact member aoxidizes

Also Published As

Publication number Publication date
FI20031790A0 (en) 2003-12-09
FI118873B (en) 2008-04-15
FI20031790A (en) 2005-08-31

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