Integrated force sensing element

Patent metadata

Field	Value
Publication number	US-10353503-B2
Application number	US-201514926265-A
Country	US
Kind code	B2
Filing date	Oct 29, 2015
Priority date	Oct 29, 2015
Publication date	Jul 16, 2019
Grant date	Jul 16, 2019

Abstract

An integrated force sensing element includes a piezoelectric sensor formed in an integrated circuit (IC) chip and a strain gauge at least partially overlying the piezoelectric sensor, where the piezoelectric sensor is able to flex. A human-machine interface using the integrated force sensing element may include a conditioning circuit, temperature gauge, FRAM and a processor core.

First claim

What is claimed is:

1. An integrated force sensing element comprising:
a silicon layer having opposite first and second surfaces;
a first dielectric layer on the second surface;
a piezoelectric sensor including: a first electrode on the first dielectric layer, a piezoelectric material on the first electrode, and a second electrode on the piezoelectric material;
a second dielectric layer on the second electrode;
a strain gauge on the second dielectric layer, the strain gauge at least partially overlying the piezoelectric sensor, the strain gauge including four thin film resistors forming a Wheatstone bridge;
a printed circuit board: and
a lead frame mounted to the printed circuit board, the first surface of the silicon layer being attached to the lead frame, with a cavity interposed between the printed circuit board and the piezoelectric sensor.

2. The integrated force sensing element of claim 1 , wherein the silicon layer having a thickness of 75 microns or less.

3. The integrated force sensing element of claim 2 , wherein the silicon layer having a thickness of 50 microns or less.

4. The integrated force sensing element of claim 1 , wherein at least part of the cavity extends through the lead frame to the first surface.

5. The integrated force sensing element of claim 1 , wherein the cavity is interposed between the printed circuit board and the lead frame.

6. The integrated force sensing element of claim 1 , wherein at least part of the cavity is formed by etching the lead frame.

7. The integrated force sensing element of claim 1 , further comprising a mold compound encapsulating at least the second dielectric layer and the strain gauge.

8. The integrated force sensing element of claim 1 , wherein the piezoelectric sensor includes a ferroelectric material selected from a group consisting of: lead zirconate titanate (PZT), aluminum nitride (AlN), and zinc oxide (ZnO).

9. The integrated force sensing element of claim 1 , wherein the strain gauge includes silicon chromium (SiCr).

10. The integrated force sensing element of claim 1 , wherein the silicon layer includes a signal conditioning circuit, the signal conditioning circuit including: a first input coupled to the piezoelectric sensor; a second input coupled to the strain gauge; and a conditioned signal output.

11. A human machine interface (HMI) comprising:
an integrated force sensor including:
a silicon layer having opposite first and second surfaces;
a first dielectric layer on the second surface;
a piezoelectric sensor including a first electrode on the first dielectric layer, a piezoelectric material on the first electrode, and a second electrode on the piezoelectric material;
a second dielectric layer on the second electrode; and
a strain gauge on the second dielectric layer, the strain gauge at least partially overlying the piezoelectric sensor, the strain gauge including four thin film resistors forming a Wheatstone bridge;
a printed circuit board; and
a lead frame mounted to the printed circuit board, the first surface of the silicon layer being attached to the lead frame, with a cavity interposed between the printed circuit board and the piezoelectric sensor;
a processor core; and
a conditioning circuit including: a first input coupled to the piezoelectric sensor; a second input coupled to the strain gauge and a conditioned signal output counted to the processor core.

12. The HMI of claim 11 , wherein the silicon layer having a thickness of 75 microns or less.

13. The HMI of claim 11 , wherein at least part of the cavity extends through the lead frame to the first surface.

14. The HMI of claim 11 , wherein the cavity is interposed between the printed circuit board and the lead frame.

15. The HMI of claim 11 , wherein at least part of the cavity is formed by etching the lead frame.

16. The HMI of claim 11 , further comprising a mold compound encapsulating at least the second dielectric layer and the strain gauge.

17. The HMI of claim 11 , wherein the piezoelectric sensor includes a ferroelectric material selected from a group consisting of: lead zirconate titanate (PZT), aluminum nitride (AlN), and zinc oxide.

18. The HMI of claim 11 , wherein the strain gauge includes silicon chromium (SiCr).

19. The HMI of claim 11 , wherein at least one of the processor core, the conditioning circuit, a random access memory (RAM), a temperature sensor or a communications interface is formed in the silicon layer.

Assignees

• Texas Instruments Inc

Inventors

• Shih Wei-Yan
• Kummerl Steve
• Toth Mark Stephen
• Lohia Alok
• Sculley Terry Lee
• Lee Seung Bae
• Summerfelt Scott Robert

Classifications

• G06F3/0414 Primary

  using force sensing means to determine a position · CPC title

• G06F3/0416 Primary

  Control or interface arrangements specially adapted for digitisers · CPC title

• G06F3/045

  using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact · CPC title

• G06F3/044

  by capacitive means · CPC title

• G01L1/22

  using resistance strain gauges · CPC title