Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
1997-09-16
2001-01-30
Lam, Cathy F. (Department: 1775)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C428S308400, C428S316600, C428S319100, C428S320200, C521S092000, C521S123000
Reexamination Certificate
active
06180221
ABSTRACT:
FIELD OF INVENTION
The present invention relates generally to electrically conductive devices and, more particularly, to an electrically conductive elastomer for grafting to thermoplastic and thermoset substrates.
BACKGROUND OF THE INVENTION
The electronic circuitry for most present day electronic products is typically provided on circuit boards. Most circuit boards are fabricated of thermoset materials such as, for example, FR4™, which contains epoxy and glass fibers. It is because of these constituent elements that thermoset materials have rigid properties. Such rigid properties are required for many applications wherein electronic circuitry is utilized.
A circuit board typically has electrically conductive traces formed thereon for making electrical connections between electronic devices mounted on the circuit board. These electrically conductive traces are typically formed by an etching process wherein a copper alloy material is applied to a surface of the circuit board, and then portions of the copper alloy material is etched away, thereby leaving the remaining copper alloy material to act as the electrically conductive traces. This etching process is typically time and labor intensive. Also, the electrically conductive traces often break when the circuit board is flexed or becomes warped due to changing thermal and/or moisture conditions. Thus, it would be beneficial to provide a material which may be used to form electrically conductive traces on a circuit board that is easily applied and can flexibly withstand most environmental conditions.
Electronic circuitry can also be provided on flex film circuits. Such flex film circuits are typically fabricated of thermoplastic materials such as, for example, KAPTON™, which contains resin fibers. These resin fibers give the flex film circuits their flexible qualities.
A flex film circuit is typically fabricated by laminating at least one electrically conductive copper alloy trace between two sheets of a thermoplastic film such as, for example, KAPTON™. An adhesive is often used to insure that the two sheets of the film remain secured together. This lamination process involves several steps and requires precise alignment of the sheets of thermoplastic film and the electrically conductive copper alloy traces as there are typically openings in the sheets of thermoplastic film to allow access to the electrically conductive copper alloy traces. Also, it is often the case that the electrically conductive traces will fracture after repeated flexing of the flex film circuit. Thus, it would be beneficial to provide a material which may be used to form electrically conductive traces on a flex film circuit that is easily applied and can withstand repeated flexing of the flex film circuit.
SUMMARY OF THE INVENTION
The present invention contemplates an electrically conductive elastomer for grafting to thermoplastic and thermoset 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.
In view of the foregoing, it is readily apparent that the primary object of the present invention is to provide an electrically conductive elastomer for grafting to thermoplastic and thermoset substrates.
The above-stated primary object, as well as other objects, features, and advantages, of the present invention will become more readily apparent from the following detailed description which is to be read in conjunction with the appended drawings.
REFERENCES:
patent: 3971610 (1976-07-01), Buchoff et al.
patent: 4145317 (1979-03-01), Sado et al.
patent: 4231901 (1980-11-01), Berbeco
patent: 4301040 (1981-11-01), Berbeco
patent: 4731282 (1988-03-01), Tsukagoshi et al.
patent: 4853277 (1989-08-01), Chant
patent: 5306558 (1994-04-01), Takahashi et al.
patent: 5431571 (1995-07-01), Hanrahan et al.
Crotzer David R.
Hanrahan Mark G.
Silva Neill N.
Lam Cathy F.
Thomas & Betts International Inc.
Weingarten, Schurgin Gagnebin & Hayes LLP
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