Methods and apparatus for a capacitive pressure sensor

• US 10,268,328 B2
• Filed: 07/12/2017
• Issued: 04/23/2019
• Est. Priority Date: 07/12/2017
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: Otagaki, Takayasu, Goto, Kensuke
• Primary Examiner(s): Mehmood, Jennifer
• Assistant Examiner(s): Subedi, Deeprose
• Application Number:
  US15/647,438
• Publication Number:
  US 20190018513A1
• Time in Patent Office: 650 Days
• Field of Search: 73724, 345173-174
• CPC Class Codes: G06F 2203/04103 Manufacturing, i.e. details related to manufacturing processes specially suited for touch sensitive devices
• CPC Class Codes: G06F 2203/04105 Pressure sensors for measuring the pressure or force exerted on the touch surface without providing the touch position
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: G06F 3/0447 Position sensing using the local deformation of sensor cells
• CPC Class Codes: H03K 17/955 using a capacitive detector
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 17/975 using a capacitive movable element
• CPC Class Codes: H03K 2217/9651 the moving element acting on a force, e.g. pressure sensitive element

Abstract

Various embodiments of the present technology may comprise methods and apparatus for a capacitive pressure sensor configured to detect firm pressure to a sensing surface. The capacitive pressure sensor may comprise a first substrate and a second substrate, wherein at least one of the first and second substrate is configured to deform when firm pressure is applied. The deformation of the sensor may either create a gap between the substrates or eliminate a gap between the substrates. The deformation may be interpreted as firm pressure to the sensing surface.

Claims

1. A capacitive sensor, comprising:

a first substrate, having a first surface, comprising a protective material; and

a second substrate, having a first surface adjacent to the first surface of the first substrate, comprising;

a capacitor comprising;

a first electrode; and

a second electrode positioned substantially coplanar with the first electrode;

wherein the first electrode and the second electrode form a capacitance;

wherein;

a gap is disposed between the first and second substrates;

the first substrate deforms under the applied pressure to a second surface of the first substrate and reduces at least a portion of the gap between the first and second substrates; and

the second substrate maintains its shape under the applied pressure.

2. The capacitive sensor according to claim 1, wherein the first surface of the first substrate abuts the first surface of the second substrate.

3. The capacitive sensor according to claim 2, wherein:

each of the first and second substrates comprise a second surface opposite the respective first surfaces; and

both the first and second substrates deform in response to the applied pressure to create a gap between at least a portion of the first and second substrates.

4. The capacitive sensor according to claim 1, wherein the protective material, comprises:

a flexible portion disposed along an outer edge of the capacitive sensor; and

a rigid portion within an interior region formed by the flexible portion; and

wherein the rigid and flexible portions are coplanar with each other.

5. The capacitive sensor according to claim 1, wherein the at least one of the first substrate and the second substrate deforms in response to a pressure greater than 861 Pascals.

6. A method for detecting an applied pressure, comprising:

providing a capacitive sensor comprising;

a first substrate; and

a second substrate;

wherein;

the second substrate comprises a first electrode coplanar with a second electrode;

the first and second electrodes form a capacitance; and

the first substrate deforms under the applied pressure to a second surface of the first substrate and reduces at least a portion of a gap between the first and second substrates; and

the second substrate maintains its shape under the applied pressure;

generating an electric field between the first and second electrodes;

measuring a change in the capacitance of the capacitive sensor in response to at least one of;

a change in the electric field; and

a change in distance between the first and second substrates;

utilizing the measured change in the capacitance to determine;

a first applied pressure; and

a second applied pressure.

7. The method of according to claim 6, wherein:

the second substrate comprises a first electrode and a second electrode;

the first and second electrodes are substantially coplanar with each other; and

generating the electric field comprises creating a voltage difference between the first electrode and the second electrode.

8. The method according to claim 6, wherein utilizing the measured change in capacitance to determine the first and second applied pressures comprises:

converting the change in capacitance to a digital value;

comparing the digital value to a first threshold;

generating a first signal based on the comparison of the digital value to the first threshold, wherein the first signal indicates the first applied pressure;

comparing the digital value to a second threshold; and

generating a second signal based on the comparison of the digital value to the second threshold, wherein the second signal indicates the second applied pressure.

9. The method according to claim 8, wherein:

the first applied pressure corresponds to a zero distance change between the first and second substrates; and

the second applied pressure corresponds to one of;

creating a gap between the first and second substrates; and

eliminating at least a portion of a gap between the first and second substrates.

10. A system for detecting proximity, touch, and pressure, comprising:

a capacitive sensor, comprising;

a first substrate having a first surface and comprising a protective material; and

a second substrate having a first surface adjacent to the first surface of the first substrate and comprising;

a capacitor comprising;

a first electrode; and

a second electrode positioned substantially coplanar with the first electrode;

wherein the first and second electrodes form a capacitance;

wherein;

a gap is disposed between the first and second substrates;

the first substrate deforms under the applied pressure to a second surface of the first substrate and reduces at least a portion of the gap between the first and second substrates; and

the second substrate maintains its shape under the applied pressure;

a measurement circuit coupled to the capacitive sensor and configured to;

measure a capacitance of the capacitor; and

output a digital value according to the measured capacitance; and

a logic unit coupled to the measurement circuit and configured to;

compare the digital value to;

a first threshold; and

a second threshold; and

output a signal according to the comparison.

11. The system according to claim 10, wherein:

the first threshold corresponds to a touch on one of the first and second substrates; and

the second threshold corresponds to a deformation of one of the first and second substrates.

12. The system according to claim 10, wherein the first surface of the first substrate abuts the first surface of the second substrate.

13. The system according to claim 12, wherein:

each of the first and second substrates comprise a second surface opposite the respective first surfaces; and

both the first and second substrates deform in response to the applied pressure to create a gap between at least a portion of the first and second substrates.

14. The system according to claim 10, wherein the protective material, comprises:

a flexible portion disposed along an outer edge of the capacitive sensor; and

a rigid portion within an interior region formed by the flexible portion; and

wherein the rigid and flexible portions are coplanar with each other.