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Low Cost Touch Sensor on the Underside of a Casing

IP.com Disclosure Number: IPCOM000031866D
Publication Date: 2004-Oct-14
Document File: 4 page(s) / 151K

Publishing Venue

The IP.com Prior Art Database

Related People

Shawn Day: INVENTOR

Abstract

This invention describes a family of very low cost capacitive touch sensors that can be fabricated on the underside of a plastic casing or other insulating member. These touch sensors can be simple capacitive touch buttons, single-dimensional capacitive position sensors, 2-dimensional capacitive touch pads, or other types of capacitive controls. Applications include a wide variety of user interface controls on devices such as notebook PCs, computer mice, computer keyboards, mobile phones, portable music players, PDAs, pagers, cameras, camcorders, etc.

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Low Cost Touch Sensor on the Underside of a Casing Shawn Day

Low Cost Touch Sensor on the Underside of a Casing

1. Inventor(s): Shawn Day

2. Synaptics Incorporated, San Jose, CA, USA

3. Short Summary

This invention describes a family of very low cost capacitive touch sensors that can be fabricated on the underside of a plastic casing or other insulating member. These touch sensors can be simple capacitive touch buttons, single-dimensional capacitive position sensors, 2-dimensional capacitive touch pads, or other types of capacitive controls. Applications include a wide variety of user interface controls on devices such as notebook PCs, computer mice, computer keyboards, mobile phones, portable music players, PDAs, pagers, cameras, camcorders, etc.

4. General Description

Figure 1 shows the construction of a 2-dimensional touch pad, where the underside of the plastic casing is shown face-up with a recessed area behind the touch sensitive surface. In use, a finger or other conductive object would be sensed through the plastic layer, on the face opposed to the recessed area.

Figure 1: Example General Construction

Within the recessed area, conductive electrodes are formed on the surface. One method for forming these electrodes is via conductive paint (or similar conductive material) that can be sprayed through a

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Low Cost Touch Sensor on the Underside of a Casing Shawn Day

masking template or otherwise deposited onto the surface. Figure 1 shows a 2-dimensional touch sensor requiring 2 sets of electrodes running perpendicularly to each other, where the electrodes must be electrically separated at the crossover points. A method for forming the required electrical separation would be to apply one set of parallel electrodes by a method such as spraying conductive paint through a masking template. Then an insulating layer could be applied over the entire area, and the second set of parallel electrodes (perpendicular to the first set) could be formed by a method such as again spraying conductive paint onto the insulator through another masking template.

Next, a circuit board containing the sensor electronics (for example, in the form of an integrated circuit) can be applied to the plastic casing. The underside of the circuit board shown in Figure 1 would contain a pattern of electrodes that lines up with the ends of the painted electrodes on the plastic casing. A suitable connector, such as an elastomeric electronic connector, between the circuit board and the plastic casing ensures electrical contact between the electrodes on the circuit board and the painted electrodes on the plastic casing. A screw or other mechanical fastener holds the circuit board to the plastic casing, compressing the elastomeric electronic connector and ensuring reliable electrical contact. An example of an elastomeric electron...