Membrane switch construction and method for making same

A membrane switch, comprising:

• a substrate;
• a first set of electrical conductors applied to the substrate and forming a plurality of switch sites;
• a single flexible membrane having a second set of electrical conductors formed thereon including at least an upper and lower tier of conductors, each tier having a plurality of switch sites, the tiers being separated by an isolation layer of insulative material, the isolation layer having holes in register with the upper tier switch sites to permit access thereto, the switch sites of the second set of conductors being in facing relation with the switch sites of the first set of conductors;
• a non-conductive spacing means disposed between the first and second conductors, said spacing means having holes in register with the switch sites such that the conductors can contact each other in response to pressure on the exterior of said membrane, the spacing means otherwise maintaining the conductors in spaced, non-contacting relation.

The method of manufacturing a membrane switch, comprising the steps of:

• (a) forming a substrate;
• (b) applying a lower tier of conductors including switch sites to the substrate;
• (c) applying an isolation layer in liquid form over the lower tier of conductors, said isolation layer have holes at the switch sites to provide access thereto;
• (d) drying the isolation layer;
• (e) applying an upper tier of conductors, including switch sites on the isolation layer;
• (f) preparing a spacing means having holes in register with the switch sites;
• (g) preparing a flexible membrane and forming a set of conductors thereon including a plurality of switch sites in facing relation with the switch sites of the upper and lower tiers;
• and
• (h) assembling said substrate, spacing means and membrane in composite form to complete the keyboard.

The method of manufacturing a membrane switch, comprising the steps of:

• (a) forming a substrate;
• (b) applying a first set of conductors to the substrate, said conductors including a plurality of switch sites;
• (c) preparing a spacing means having holes in register with the switch sites of the first set of conductors;
• (d) preparing a flexible membrane;
• (e) applying an upper tier of conductors including switch sites to the underside of the membrane;
• (f) applying an isolation layer in liquid form over the upper tier of conductors, said isolation layer having holes at the switch sites to provide access thereto;
• (g) drying the isolation layer;
• (h) applying a lower tier of conductors, including switch sites to the isolation layer, the switch sites of both the upper and lower tiers being in register with the holes of the spacing means;
• (i) assembling said substrate, spacing means and membrane in composite form to complete the keyboard.

A membrane switch, comprising:

• a substantially rigid plate;
• a cover layer of insulative material applied in liquid form to the plate;
• a first set of electrical conductors applied to the cover layer and forming a plurality of switch sites, the first set of conductors having at least an upper and lower tier of conductors, each tier having a plurality of switch sites, the tiers being separated by an isolation layer of insulative material which is applied in liquid form, the isolation layer having holes in register with the lower tier switch sites to permit access thereto;
• a flexible membrane having a second set of electrical conductors formed thereon including a plurality of switch sites in facing relation with the switch sites of the first set of conductors;
• a non-conductive spacing means disposed between the first and second conductors, said spacing means having holes in register with the switch sites such that the conductors can contact each other in response to pressure on the exterior of said membrane, the spacing means otherwise maintaining the conductors in spaced, non-contacting relation;
• and
• at least one crossover conductor lying on the spacing means, the spacing means having interconnect holes at selected points which permit the crossover conductor to electrically connect selected upper tier conductors.

A membrane switch, comprising:

• a substantially rigid plate;
• a cover layer of insulative material applied in liquid form to the plate;
• a first set of electrical conductors applied to the cover layer and forming a plurality of switch sites;
• a flexible membrane having a second set of electrical conductors formed thereon including a plurality of switch sites in facing relation with the switch sites of the first set of conductors, said second set of conductors comprising at least an upper and lower tier of conductors, each tier having a plurality of switch sites, the tiers being separated by an isolation layer of insulative material which is applied in liquid form, the isolation layer having holes in register with the upper tier switch sites to permit access thereto by the first set of conductors;
• a non-conductive spacing means disposed between the first and second conductors, said spacing means having holes in register with the switch sites such that the conductors can contact each other in response to pressure on the exterior of said membrane, the spacing means otherwise maintaining the conductors in spaced, non-contacting relation;
• and
• at least one crossover conductor lying under the spacing means, the spacing means having interconnect holes at selected points which permit the crossover conductor to electrically connect selected lower tier conductors.

In a membrane switch keyboard of the type having a substrate, a first set of conductors on the substrate and having a plurality of switch sites, a flexible membrane, a second set of conductors on the underside of the membrane and having a plurality of switch sites in facing relation with the switch sites of the first set of conductors, a non-conductive spacing means disposed between the first and second conductors, said spacing means having holes in register with the switch sites such that the conductors can contact each other in response to pressure on the exterior of said membrane, the spacing means otherwise maintaining the conductors in spaced, non-contacting relation, an improved method of manufacturing the keyboard, comprising the step of:

• (a) forming a plate of substantially rigid material;
• (b) applying a cover layer of insulative material in liquid form to said plate and then drying the cover layer;
• (c) applying said first set of conductors to said cover layer;
• (d) preparing said spacing means;
• (e) preparing a flexible membrane and forming said second set of conductors thereon;
• and
• (f) assembling said plate, spacing means and membrane in composite form to complete the keyboard.