Patent CA-2245413-C (CA)
Title: Conductive elastomer for grafting to an elastic substrate
Inventor: HANRAHAN MARK G
IPC: H05K9/00
Filed: 1998-08-24
Granted: 2001-09-18
Abstract: The  present  invention  contemplates  an  electrically conductive elastomer for grafting to a substrate.   The conductive  elastomer  comprises  a  non-conductive  elastic material having a quantity of conductive flakes interspersed therein.   The conductive elastomer may further comprise a quantity of conductive particles interspersed in the non-conductive elastic material.  Alternatively, a quantity of conductive particles may be imbedded in an outer surface of the  conductive  elastomer.   The  conductive  elastomer  is typically grafted to the substrate by a thermal process.     In one application, the conductive elastomer is grafted to an elastic substrate to form electrically conductive circuit traces.   In another application,  the conductive elastomer is grafted to an elastic substrate which is used as a telephone, computer, or calculator keypad.   In still another application, the conductive elastomer is grafted to an elastic substrate to form a shield against unwanted electric and magnetic fields.  Additionally,  the present  invention contemplates an electrically   conductive   elastomer   for   grafting   to thermoplastic,  thermoset  and metal  substrates.    If  the substrate  is  a  thermoset  substrate,  the  electrically conductive  elastomer comprises  a mixture  of  an elastic material, a quantity of electrically conductive flakes, a thermoplastic elastomer material, and a thermoset material. If  the  substrate  is  a  thermoplastic  substrate,  the electrically conductive elastomer comprises a mixture of an elastic material,  a quantity of  electrically conductive flakes,   a  thermoplastic  elastomer  material,   and  a thermoplastic  material.     The  electrically  conductive elastomer may further comprise a quantity of electrically conductive  particles  interspersed within  the  mixture. Alternatively,   a  quantity  of  electrically  conductive particles  may be  imbedded  in  an  outer  surface  of  the electrically  conductive  elastomer.     The  electrically conductive elastomer is typically grafted to the substrate by a thermal process.     In  one  application,   the  electrically  conductive elastomer is grafted to an thermoset circuit board to form electrically conductive contact pads and circuit traces.  In another application, the electrically conductive elastomer is grafted to a thermoplastic flex film to form electrically conductive contact pads and circuit traces.     Additionally,  the  electrically conductive  elastomer comprises a mixture of an elastic material, a quantity of electrically conductive flakes, a thermoplastic elastomer material, a conductive thermoplastic polymer material, and a noble metal  or noble metal  composite material.   The electrically conductive elastomer may further comprise a quantity of electrically conductive particles interspersed within  the  mixture.     Alternatively,   a  quantity  of electrically conductive particles may be imbedded in an outer surface  of  the  electrically conductive  elastomer.    The electrically conductive elastomer is typically grafted to the substrate by a thermal process.