Attaching wire coil to plastic sheet for use in transponder assembly in chip card involves passing current through coil to heat it so that coil sinks into thermoplastic sheet

摘要

A wire is embedded in a thermoplastic sheet (1) to form a coil (2), which is later joined (7, 8) to a chip (6), by passing a current through it. This heats it sufficiently, either by resistance heating or induction heating, to soften the sheet (1) so that the wire sinks into it and is embedded. The process can be assisted by applied pressure or subsequent flattening with the application of heat and pressure. An independent claim is included for producing a transponder coil, especially by this method, in which the coil is wound round a carrier with an adhesive layer on one side. During winding a solvent for the wire insulation is applied so that adjacent insulating layers are joined when the solvent has evaporated. Five to eight turns of copper wire are suitable.