Apparatus and method for protecting fingerprint sensing circuitry from electrostatic discharge

• US 20080267462A1
• Filed: 04/30/2007
• Published: 10/30/2008
• Est. Priority Date: 04/30/2007
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Validity Sensors Incorporated (Synaptics Incorporated)
• Inventors: Erhart, Richard Alexander, Nelson, Richard Brian, Perezselsky, Armando
• Granted Patent: US 8,107,212 B2
• Time in Patent Office: Days
• US Class Current: 382/124
• CPC Class Codes: G06V 40/1329 Protecting the fingerprint sensor against damage caused by the finger

Abstract

A fingerprint sensor in accordance with the invention includes a non-conductive substrate providing a first surface onto which a user can apply a fingerprint to be sensed. A sensor circuit is applied to a second surface of the non-conductive substrate opposite the first surface to sense a fingerprint when juxtaposed proximally thereto. An electrostatic discharge conductor is applied to the non-conductive surface and is located between an area where a fingerprint is swiped and the sensor circuit. The electrostatic discharge conductor discharges electrostatic charge resulting from a user swiping a fingerprint across the first surface.

Claims

1. A fingerprint sensor comprising:

a non-conductive substrate providing a first surface onto which a user can apply a fingerprint to be sensed;

a sensor circuit applied to a second surface of the non-conductive substrate opposite the first surface to sense a fingerprint when juxtaposed proximally thereto;

an electrostatic discharge conductor applied to the non-conductive surface and located between an area where a fingerprint is swiped and the sensor circuit, the electrostatic discharge conductor discharging electrostatic charge resulting from a user swiping a fingerprint across the first surface.

2. The sensor according to claim 1, wherein the electrostatic discharge conductor is applied to the first surface.

3. The sensor according to claim 2, wherein the electrostatic discharge conductor encircles or partially encircles the sensor circuit.

4. The sensor according to claim 1, wherein the electrostatic discharge conductor is applied to the second surface.

5. The sensor according to claim 4, wherein the electrostatic discharge conductor encircles the area where a fingerprint is swiped.

6. The sensor according to claim 1, wherein the electrostatic discharge conductor is applied to an edge of the non-conductive substrate.

7. The sensor according to claim 1, wherein the sensor circuit and non-conductive substrate together are selected from the group consisting chip on flex (COF), a flexible circuit board, a printed circuit board (PCB), and an integrated circuit (IC).

8. The sensor according to claim 1, further comprising a processor operably coupled to the sensor circuit to process fingerprint data received therefrom.

9. The sensor according to claim 1, wherein the electrostatic discharge conductor is made of the same material as conductive traces of the sensor circuit.

10. The sensor according to claim 1, wherein the sensor circuit comprises at least one of an image sensor, a velocity sensor, and a sensor IC.

11. An ESD-protected circuit comprising:

a non-conductive surface onto which an electrostatic charge can accumulate;

a circuit coupled to the non-conductive surface and sensitive to electrostatic discharge; and

an electrostatic discharge conductor coupled to the non-conductive surface and positioned to discharge an electrostatic charge from the non-conductive surface and thereby protect the circuit.

12. The ESD-protected circuit according to claim 11, wherein the circuit is a fingerprint sensing circuit.

13. The ESD-protected circuit according to claim 12, wherein the non-conductive surface is flexible.

14. The ESD-protected circuit according to claim 13, wherein the non-conductive surface comprises polyimide.

15. The ESD-protected circuit according to claim 11, wherein the electrostatic discharge conductor encircles or partially encircles the circuit.

16. The ESD-protected circuit according to claim 11, wherein the sensor circuit and non-conductive surface together are selected from the group consisting chip on flex (COF), a flexible circuit board, a printed circuit board (PCB), and an integrated circuit (IC).

17. The ESD-protected circuit according to claim 11, further comprising a processor operably coupled to the circuit.

18. The ESD-protected circuit according to claim 11, wherein the electrostatic discharge conductor is made of the same material as conductive traces of the circuit.

19. The ESD-protected circuit according to claim 11, wherein the circuit comprises at least one column driver.

20. The ESD-protected circuit according to claim 11, wherein the circuit is associated with at least one of a touch pad, touch screen, touch panel, keyboard, keypad, mouse, joystick, and trackball.

21. A fingerprint sensor comprising:

a first non-conductive substrate;

a fingerprint sensor circuit applied to the first non-conductive substrate;

a second non-conductive substrate applied to the first non-conductive substrate to cover the fingerprint sensor circuit, the second non-conductive substrate also providing an area onto which a user can apply a fingerprint;

an electrostatic discharge conductor located between the area and the sensor circuit, the electrostatic discharge conductor discharging electrostatic charge resulting from a user applying a fingerprint to the area.

22. The sensor according to claim 21, wherein the electrostatic discharge conductor is applied to the first non-conductive substrate.

23. The sensor according to claim 21, wherein the electrostatic discharge conductor is applied to the second non-conductive substrate.

24. The sensor according to claim 21, wherein the electrostatic discharge conductor encircles the fingerprint sensor circuit.

25. The sensor according to claim 21, wherein the electrostatic discharge conductor only partially surrounds the fingerprint sensor circuit.

26. The sensor according to claim 21, wherein the second non-conductive substrate comprises polyimide.