EP0133817A2 - Membranschalter - Google Patents

Membranschalter Download PDF

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Publication number
EP0133817A2
EP0133817A2 EP84305404A EP84305404A EP0133817A2 EP 0133817 A2 EP0133817 A2 EP 0133817A2 EP 84305404 A EP84305404 A EP 84305404A EP 84305404 A EP84305404 A EP 84305404A EP 0133817 A2 EP0133817 A2 EP 0133817A2
Authority
EP
European Patent Office
Prior art keywords
switch
contacts
laminar
base member
contact resistance
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.)
Withdrawn
Application number
EP84305404A
Other languages
English (en)
French (fr)
Other versions
EP0133817A3 (de
Inventor
Geoffrey Thomas Hilton
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.)
British Telecommunications PLC
Original Assignee
British Telecommunications 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 British Telecommunications PLC filed Critical British Telecommunications PLC
Publication of EP0133817A2 publication Critical patent/EP0133817A2/de
Publication of EP0133817A3 publication Critical patent/EP0133817A3/de
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H13/00—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch
    • H01H13/70—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard
    • H01H13/78—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard characterised by the contacts or the contact sites
    • H01H13/785—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard characterised by the contacts or the contact sites characterised by the material of the contacts, e.g. conductive polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H13/00—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch
    • H01H13/70—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard
    • H01H13/702—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard with contacts carried by or formed from layers in a multilayer structure, e.g. membrane switches
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2201/00—Contacts
    • H01H2201/022—Material
    • H01H2201/026—Material non precious
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2201/00—Contacts
    • H01H2201/022—Material
    • H01H2201/03—Composite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2207/00—Connections
    • H01H2207/02—Solder
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2209/00—Layers
    • H01H2209/024—Properties of the substrate
    • H01H2209/032—Properties of the substrate non elastomeric
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2209/00—Layers
    • H01H2209/068—Properties of the membrane
    • H01H2209/076—Properties of the membrane non elastomeric
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2229/00—Manufacturing
    • H01H2229/002—Screen printing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2229/00—Manufacturing
    • H01H2229/008—Die stamping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2229/00—Manufacturing
    • H01H2229/016—Selective etching
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2229/00—Manufacturing
    • H01H2229/024—Packing between substrate and membrane
    • H01H2229/028—Adhesive
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2229/00—Manufacturing
    • H01H2229/038—Folding of flexible printed circuit
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2239/00—Miscellaneous
    • H01H2239/008—Static electricity considerations

Definitions

  • the present invention relates to membrane switches.
  • Previously proposed membrane switch panels include a rigid printed circuit board carrying a printed circuit having switch contacts.
  • a single elastomer membrane covers the printed circuit board but is held spaced from the printed circuitry thereon.
  • the membrane which may be rubber or silicone, is rendered electrically conductive by impregnation with an electrically conductive component.
  • the membrane is depressed in the area of a pair of contacts on the panel to bridge the contacts and so close the switch.
  • the whole membrane may be rendered selectively electrically conductive in discrete areas corresponding to the pairs of switch contacts on the printed circuit board.
  • the switch contacts and conductive circuitry patterns are formed on the membranes by squeezing (squeegeeing) thixotropic electrically conductive ink paste through an appropriately stencilled mesh screen onto the membranes. The ink is then dried to leave the conductive contacts and circuitry.
  • the ink compositions used contain precious metals such as silver, palladium and gold or combinations of such metals.
  • a disadvantage of such membrane switches is that they are expensive to produce because of the materials used and the need to use an additive process to form both the conductive circuitry and switch contacts on the membrane.
  • the present invention is based upon our surprising discovery that it is possible to achieve and maintain low contact resistance with bare copper contacts in membrane switch assemblies despite their not being fully hermetically sealed (that is, where the membrane material is incapable of providing a truly hermetic seal).
  • a membrane switch comprising a base member, a flexible laminar member sealed to the base member, and an electrically insulating separator separating at least one portion of the laminar member from a corresponding portion of the base member, said portions each carrying a respective one of a pair of mutually engageable contacts of copper having a low contact resistance, sealed in an environment of limited tarnishing ability.
  • a membrane switch panel comprising a pair of laminar members separated by an electrically insulating spacer, at least one of the members being flexible, the two members carrying mating contacts of copper having a low contact resistance, the spacer having one or more openings each allowing access of one or more of said contacts to one or more others, and means sealing the space between the two enembers and enclosing an enviroment for the contacts which has a limited tarnishing ability.
  • a method of manufacturing a membrane switch comprising processing a copper foil clad laminar member by a subtractive process to form at least one electrical contact, providing a base member carrying a mating contact, said contacts having a low contact resistance, inserting a perforated electrically insulating separator between the base member and the laminar member and sealing an atmosphere of limited tarnishing ability in the space between the base member and laminar member enclosing said mating contacts.
  • the switch panel in Figure 1 includes upper and lower foil clad non-elastomer membranes 2 and 4.
  • the membranes are advantageously polyester or polyimide, while the foil cladding is advantageously of annealed electrolytic copper.
  • the foil cladding is subjected to screen printing or photo-imaging with an etch resistant material and subsequently corrosively etched away to leave conductive patterns 5 and 6 and switch contacts 8 and 10 respectively on the upper and low membranes 2 and 4.
  • the conductor pattern is formed by a die stamping process.
  • the two membranes 2 and 4 are separated by an electrically insulating perforated layer 12 of polyester.
  • the perforations or openings in the layer 12 are large enough and so positioned that they allow mating contacts 8 and 10 on the upper and lower layers access to one another.
  • the lower layer 4 is adhesively mounted on a rigid board 14.
  • the two layers 2 and 4 are sealed together around their edges with an adhesive.
  • a marked area on the upper layer 2 is depressed by an operator to cause a contact 8 on the underside of the upper layer to engage a contact 10 on the lower layer 4 and so close the switch (see Figure 2).
  • the resilience of the upper layer 2 will enable the two contacts 8 and 10 to separate upon release by the operator.
  • the space between the two sets of membranes may be filled with dry nitrogen or any other generally inert atmosphere.
  • the present invention can thus provide membrane switches having low contact resistances which are preferably less than 10 ohms more preferably less than 1 ohm and can be made lower than 0.3 ohm.
  • Known membrane switches have contact resistances of as much as several hundred ohms (with carbon loaded contacts), with anything less than about a hundred ohms (less than 100 ohms is attainable with silver/palladium inks; contact resistances of 1 ohm or less only being achievable with very heavily loaded silver inks) being considered to be a low contact resistance.
  • the term low contact resistance is taken to mean a contact resistance of less than 100 ohms when measured using a conventional four pole measurement technique with a maximum applied potential of 200 millivolts and a current of 50 microamps.
  • the switch panel shown in Figure 3 has a rigid printed circuit board 20 carrying printed circuitry including pairs of contacts 26 and 28.
  • a flexible membrane 22 of polyester overlies the printed circuit board 20 and carries on its underside contacts 24.
  • a perforated layer 30 of electrically insulating material separates the membrane 22 from the board.
  • the contacts 24, 26 and 28 are all of copper and formed by an etching or other subtractive process.
  • the environment between the board 20 and the layer 22 is such that the contacts are not significantly subjected to tarnishing.
  • both the printed circuit board 20 and the flexible layer 22 carry electrical circuitry 40 as well as contacts 42.
  • the flexible layer 22 carries both contacts 50 and electrical circuitry 52, while the printed circuit board carries only contacts 54.
  • a further advantage of the above described panels is that they can readily be given protection against the well known problem of static discharges.
  • static electricity is both generated and carried by the equipment user.
  • the equipment user touches a membrane switch the static charge which he is carrying can be discharged via the switch (particularly if the contact gaps within the switch are small) damaging circuitry associated with the switch.
  • Switches according to the invention can readily be given appreciable protection against this damaging problem by providing the upper layer (or whichever of the layers is to be the outermost or touched surface) with an additional layer of copper foil on the outside of the assembly, ie the outer layer is made from a flexible membrane having a copper foil layer on each side. The extra copper layer then being connected to earth.
  • the present invention makes it possible for membrane switch panels to be made cheaply and easily using conventional printed circuit board technology, without the need for the more expensive elastomers and conductive polymers or inks.
  • membrane switch panels from just two pieces (or even from one piece) by the simple expedient of folding a single membrane which carries both the upper and the lower conductors and contacts (the one piece switch panel has its perforated layer 12 made integrally with the upper and lower layers, so there are two folds). Care should be taken if adopting this folded construction to ensure that an effective seal is achieved adjacent to the fold(s).
  • the membrane material will exhibit some 'memory' effects, and unless a sufficiently strong bond is created adjacent to the fold, the membrane parts will separate and destroy the seal, with consequent loss of low contact resistance.
EP84305404A 1983-08-11 1984-08-08 Membranschalter Withdrawn EP0133817A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8321689 1983-08-11
GB838321689A GB8321689D0 (en) 1983-08-11 1983-08-11 Membrane switches

Publications (2)

Publication Number Publication Date
EP0133817A2 true EP0133817A2 (de) 1985-03-06
EP0133817A3 EP0133817A3 (de) 1985-04-10

Family

ID=10547180

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84305404A Withdrawn EP0133817A3 (de) 1983-08-11 1984-08-08 Membranschalter

Country Status (3)

Country Link
EP (1) EP0133817A3 (de)
GB (2) GB8321689D0 (de)
WO (1) WO1985000923A1 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2610470A1 (fr) * 1987-01-30 1988-08-05 Meliconi Srl Gaine de protection resistant aux chocs pour telecommandes, notamment de televiseurs
FR2881091A1 (fr) * 2005-01-24 2006-07-28 Cera Composant de garnissage comprenant une couche mince de commande formant interrupteur
US11222757B2 (en) 2018-02-01 2022-01-11 Razer (Asia-Pacific) Pte. Ltd. Key switch mechanisms, user input devices and methods of fabricating a key switch mechanism

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4713534A (en) * 1986-02-18 1987-12-15 Carroll Touch Inc. Phototransistor apparatus with current injection ambient compensation
US6958183B2 (en) * 2001-02-20 2005-10-25 Teikoku Tsushin Kogyo Co., Ltd. Key top plate and a method for manufacturing the same
GB2421635B (en) * 2004-12-24 2007-12-05 In2Connect Ltd A switch
CN106994924A (zh) * 2017-05-18 2017-08-01 上海安闻汽车电子有限公司 一种人体压力传感器及汽车座椅

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3862381A (en) * 1973-10-29 1975-01-21 Chomerics Inc Keyboard switch assembly with multilayer, coextensive contactor means
US4314114A (en) * 1980-02-04 1982-02-02 Oak Industries Laminated membrane switch
US4338502A (en) * 1978-04-27 1982-07-06 Sharp Kabushiki Kaisha Metallic housing for an electronic apparatus with a flat keyboard
AT370912B (de) * 1980-09-17 1983-05-10 Electrovac Vorrichtung zum schalten eines oder mehrerer elektrischer stromkreise

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3862381A (en) * 1973-10-29 1975-01-21 Chomerics Inc Keyboard switch assembly with multilayer, coextensive contactor means
US4338502A (en) * 1978-04-27 1982-07-06 Sharp Kabushiki Kaisha Metallic housing for an electronic apparatus with a flat keyboard
US4314114A (en) * 1980-02-04 1982-02-02 Oak Industries Laminated membrane switch
AT370912B (de) * 1980-09-17 1983-05-10 Electrovac Vorrichtung zum schalten eines oder mehrerer elektrischer stromkreise

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
L.B. HUNT et al.: "Electrical contacts", 1946, pages 74,85,86, Johnson, Matthey & Co. Ltd., London, GB; *
RADIO FERNSEHEN ELEKTRONIK, vol. 32, no. 6, June 1983, page 341, Berlin, DD; "Folienmembranschalter" *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2610470A1 (fr) * 1987-01-30 1988-08-05 Meliconi Srl Gaine de protection resistant aux chocs pour telecommandes, notamment de televiseurs
BE1003249A3 (fr) * 1987-01-30 1992-02-11 Meliconi Srl Gaine de protection resistant aux chocs pour telecommandes, notamment de televiseurs.
FR2881091A1 (fr) * 2005-01-24 2006-07-28 Cera Composant de garnissage comprenant une couche mince de commande formant interrupteur
US11222757B2 (en) 2018-02-01 2022-01-11 Razer (Asia-Pacific) Pte. Ltd. Key switch mechanisms, user input devices and methods of fabricating a key switch mechanism

Also Published As

Publication number Publication date
GB8420140D0 (en) 1984-09-12
GB8321689D0 (en) 1983-09-14
GB2144917A (en) 1985-03-13
WO1985000923A1 (en) 1985-02-28
EP0133817A3 (de) 1985-04-10

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

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PUAL Search report despatched

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AK Designated contracting states

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STAA Information on the status of an ep patent application or granted ep patent

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18D Application deemed to be withdrawn

Effective date: 19851210

R18D Application deemed to be withdrawn (corrected)

Effective date: 19851211

RIN1 Information on inventor provided before grant (corrected)

Inventor name: HILTON, GEOFFREY THOMAS