Method for forming an EMI shielding gasket

A process for forming a bead of fluent polymeric material carrying electrically conductive particles on a substrate, which bead acts to provide an EMI shielding gasket, said fluent polymeric material being extruded from an extruder head through an orifice by exerting pressure on the fluent polymeric material, said process comprising the steps of:

• supplying said fluent polymeric material to said extrusion head,
• forming a bead of said polymeric material on said substrate by increasing pressure on said fluent polymeric material to cause said fluent polymeric material to flow out the extrusion head while simultaneously moving said extrusion head relative to said substrate, and varying the amount of pressure while varying the speed of the relative motion between the extrusion head and the substrate to maintain a desired cross-section bead formation, and
• reducing the pressure to a negative gauge pressure to discontinue the bead formation.

A process of forming an electrically conductive shielding gasket having a cross sectional area of from about 0.0002 in.sup.2 to about 0.01563 in.sup.2 by extruding fluent polymeric material having electrically conductive particles therein through an extrusion head having an extrusion orifice with the use of air pressure variation applied to a surface of said fluent polymeric material within said extrusion head said process comprising:

• selecting said fluent polymeric material having a viscosity between 100,000 and 10,000,000 centipoise and positioning said fluent polymeric material on a first side of said extrusion orifice,
• extruding said fluent polymeric material from said extrusion head by applying gas pressure thereto to cause a bead of said fluent polymeric material to be extruded onto a substrate while moving said substrate with respect to said extrusion head at a speed of from 0.5 in/sec to 6.0 in/sec said bead being formed having an accuracy of about .+-.0.002 in., and,
• varying said air from a positive gauge pressure to a negative gauge pressure, on said fluent polymeric material to alternately start and stop the bead being extruded.