Pattern for Force Sensor Layer with Membrane
Publication Date: 2014-Jun-27
The IP.com Prior Art Database
Proximity sensor devices (also commonly called touch sensor devices) are widely used in a variety of electronic systems. A proximity sensor device typically includes a sensing region, often demarked by a surface in which input objects can be detected. The proximity sensor can be used to enable control of an associated electronic system. Some proximity sensors have been implemented with additional ability to detect and determine force applied to a surface of the sensor. For example, a capacitive sensor having several arrays of sensor electrodes may provide force information about user input in response to a change in capacitance between a layer receiver electrodes and transmitter electrodes. The layers of receiver and transmitter electrodes may be separated by a compressible medium. Touch and force sensing are achieved by splitting up the receivers in two layers. One layer of receivers is located above the transmitters and senses capacitive touch, as is the case with other traditional sensors. The second layer of receivers is located below the transmitters. A compressible medium is placed between the transmitters and the second layer of receivers. When the sensor is pressed, the deformation and/or compression occur causing the capacitance between receivers and transmitters changes, thusly allowing capacitive force sensing. While the medium itself may be compressible, deflection also occurs due to the design of the membrane, i.e., pressure on the dots in the membrane design causes cutouts in the membrane to be primarily deflected downward rather than compress. The type and design of the compressible medium used can have a significant effect on performance and cost of the system. A compressible medium comprising a membrane with periodic cutouts and spacer dots on both sides is designed to utilize the flexural rigidity of the material to drive the restoring force upon compression. While in some sense compression, the membrane design is deflected by a vertical force causing the membrane to deform as illustrated in Figure 3.