Force sensing resistor (FSR) with polyimide substrate, systems, and methods thereof
A force sensing resistor (FSR) that is constructed with a first substrate made of polyimide disposed underneath a second substrate that is resistive and flexible. A handheld controller for an electronic system may include the FSR having a first substrate made of polyimide. The FSR may be mounted on a planar surface of a structure within the controller body, such as a structure mounted within a handle of the controller body, and/or a structure that is mounted underneath at least one thumb-operated control that is included on a head of the controller body. The FSR may be configured to measure a resistance value that corresponds to an amount of force applied to an outer surface of the handle and/or an amount of force applied to the at least one thumb-operated control.
1. A handheld controller comprising:
a controller body; and
a force sensing resistor (FSR) mounted within the controller body, the FSR comprising:
a first substrate made of polyimide and having conductive material disposed on a front surface of the first substrate;
a second substrate that is flexible and having resistive material disposed on a back surface of the second substrate, wherein the second substrate is disposed on the first substrate; and
one or more spacer layers interposed between the first substrate and the second substrate.
2. The handheld controller of claim 1 , further comprising an actuator disposed on the second substrate and configured to convey a force onto a front surface of the second substrate.
3. The handheld controller of claim 1 , wherein:
the controller body includes a handle;
the FSR is mounted on a planar surface of a structure that is mounted within the handle; and
the FSR is configured to measure a resistance value that corresponds to an amount of a force applied to an outer surface of the handle.
4. The handheld controller of claim 1 , wherein:
the controller body includes at least one thumb-operated control;
the FSR is mounted on a planar surface of a structure that is mounted underneath the at least one thumb-operated control; and
the FSR is configured to measure a resistance value that corresponds to an amount of a force applied to the at least one thumb-operated control.
5. The handheld controller of claim 1 , wherein:
the conductive material comprises a plurality of interdigitated metal fingers disposed on the front surface of the first substrate;
the plurality of interdigitated metal fingers are made of gold-plated copper including a base copper material and gold material atop the base copper material; and
the gold material is in direct contact with the base copper material.
6. The handheld controller of claim 1 , wherein the one or more spacer layers include:
a coverlay of polyimide disposed on the first substrate at a periphery of the first substrate, the coverlay covering a peripheral portion of the conductive material, and leaving a remaining portion of the conductive material uncovered by the coverlay; and
a layer of adhesive disposed on the coverlay, the layer of adhesive leaving the remaining portion of the conductive material uncovered by the layer of adhesive, and leaving a section of the coverlay uncovered by the layer of adhesive to create an air gap that allows air to ingress or egress from a space between the first substrate and the second substrate.
7. The handheld controller of claim 6 , further comprising an actuator disposed on the second substrate and configured to convey a force onto a front surface of the second substrate, wherein:
an area of the remaining portion of the conductive material that is uncovered by the coverlay and by the layer of adhesive corresponds to an active area of the FSR; and
the actuator covers 80% of the active area, the actuator being concentric with a center of the active area of the FSR.
8. A force sensing resistor (FSR) comprising:
a first substrate made of polyimide and having conductive material disposed on a front surface of the first substrate;
a second substrate that is flexible and having resistive material disposed on a back surface of the second substrate, wherein the second substrate is disposed on the first substrate;
one or more spacer layers interposed between the first substrate and the second substrate; and
output terminals including a first output terminal and a second output terminal, wherein a resistance across the output terminals varies in response to variable force applied to the FSR.
9. The FSR of claim 8 , further comprising an actuator disposed on the second substrate and configured to convey a force onto a front surface of the second substrate.
10. The FSR of claim 8 , wherein:
the conductive material comprises a plurality of interdigitated metal fingers disposed on the front surface of the first substrate;
the plurality of interdigitated metal fingers are made of gold-plated copper including a base copper material and gold material atop the base copper material; and
the gold material is in direct contact with the base copper material.
11. The FSR of claim 8 , wherein the one or more spacer layers include:
a coverlay of polyimide disposed on the first substrate at a periphery of the first substrate, the coverlay covering a peripheral portion of the conductive material, and leaving a remaining portion of the conductive material uncovered by the coverlay; and
a layer of adhesive disposed on the coverlay, the layer of adhesive leaving the remaining portion of the conductive material uncovered by the layer of adhesive, and leaving a section of the coverlay uncovered by the layer of adhesive to create an air gap that allows air to ingress or egress from a space between the first substrate and the second substrate.
12. The FSR of claim 11 , further comprising an actuator disposed on the second substrate and configured to convey a force onto a front surface of the second substrate, wherein:
an area of the remaining portion of the conductive material that is uncovered by the coverlay and by the layer of adhesive corresponds to an active area of the FSR; and
the actuator covers 80% of the active area, the actuator being concentric with a center of the active area of the FSR.
13. The FSR of claim 11 , wherein the layer of adhesive has a thickness of 50 microns.
14. The FSR of claim 8 , wherein:
the conductive material comprises a plurality of interdigitated metal fingers disposed on the front surface of the first substrate;
a distance between pairs of adjacent metal fingers among the plurality of interdigitated metal fingers is 0.2 millimeters (mm); and
a width of each metal finger of the plurality of interdigitated metal fingers is 0.2 mm.
15. The FSR of claim 8 , further comprising an actuator disposed on the second substrate and configured to convey a force onto a front surface of the second substrate, wherein the actuator is made of a compliant material that deforms when subjected to the force.
16. The FSR of claim 8 , wherein the FSR is mounted on a planar surface of a structure within a handheld controller.
17. The FSR of claim 16 , wherein:
the structure is mounted within a handle of the handheld controller; and
the FSR is configured to measure a resistance value that corresponds to an amount of a force applied to an outer surface of the handle.
18. The FSR of claim 16 , wherein:
the structure is mounted underneath a thumb-operated control of the handheld controller; and
the FSR is configured to measure a resistance value that corresponds to an amount of a force applied to the thumb-operated control.
19. A force sensing resistor (FSR) comprising:
a first substrate made of polyimide and having conductive material disposed on a front surface of the first substrate;
a second substrate that is flexible and having resistive material disposed on a back surface of the second substrate, wherein the second substrate is disposed on the first substrate, and wherein a center portion of the second substrate is suspended over the first substrate; and
output terminals including a first output terminal and a second output terminal,
wherein a resistance across the output terminals varies in response to variable force applied to the FSR.
20. The FSR of claim 19 , wherein:
the conductive material comprises a plurality of interdigitated metal fingers disposed on the front surface of the first substrate; and
the plurality of interdigitated metal fingers comprise a first set of metal fingers coupled to the first output terminal and a second set of metal fingers coupled to the second output terminal.
21. The FSR of claim 19 , wherein:
the conductive material comprises a plurality of interdigitated metal fingers disposed on the front surface of the first substrate; and
a distance between pairs of adjacent metal fingers among the plurality of interdigitated metal fingers is equal to a width of each metal finger of the plurality of interdigitated metal fingers.
22. The FSR of claim 19 , wherein the FSR is mounted on a planar surface of a structure within a handheld controller.
23. The FSR of claim 22 , wherein:
the structure is mounted:
within a handle of the handheld controller; or
underneath a thumb-operated control of the handheld controller; and
the FSR is configured to measure a resistance value that corresponds to an amount of a force applied to:
an outer surface of the handle; or
the thumb-operated control.