Fingerprint sensing device with heterogeneous coating structure comprising a dielectric material

• US 10,043,049 B2
• Filed: 07/20/2017
• Issued: 08/07/2018
• Est. Priority Date: 06/08/2015
• Status: Active Grant

• Current Assignee: Fingerprint Cards AB
• Original Assignee: Fingerprint Cards AB
• Inventors: Lundahl, Karl, Nilsson, Hanna
• Primary Examiner(s): WOLDEMARIAM, AKLILU K
• Application Number:
  US15/654,798
• Publication Number:
  US 20170316247A1
• Time in Patent Office: 383 Days
• Field of Search: 382124, 382312, 345173, 345174, 345207, 235493, 235449, 257341, 257342, 257350, 257226, 257233, 257207
• CPC Class Codes: G06F 18/00 Pattern recognition
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: G06V 40/1329 Protecting the fingerprint sensor against damage caused by the finger
• CPC Class Codes: G06V 40/1365 Matching; Classification

Abstract

The invention relates to a fingerprint sensing device comprising a sensing chip comprising an array of capacitive sensing elements. The sensing device comprises a coating material arranged in a layer on top of the array of sensing elements and comprising a plurality of cavities filled with a dielectric material. The dielectric material comprises reduced graphene oxide. Locations of the cavities correspond to locations of the sensing elements such that a cross-section area of a cavity covers at least a portion of an area of a corresponding sensing element. A dielectric constant of the dielectric material is higher than a dielectric constant of the coating material. The invention also relates to a sensing device where the dielectric coating layer containing reduced graphene oxide comprises trenches corresponding to areas between the sensing pixels filled with a fill material, where the dielectric coating layer has a higher dielectric constant than the fill material.

Claims

1. A fingerprint sensing device comprising:

a sensing chip comprising an array of sensing elements, said sensing elements being configured to be connected to readout circuitry for detecting a capacitive coupling between each of said sensing elements and a finger placed on a sensing surface of said sensing device;

a coating material arranged in a layer on top of said array of sensing elements, said coating material comprising a plurality of cavities filled with a dielectric material, wherein locations of said cavities correspond to locations of said sensing elements, such that a cross-section area of a cavity covers at least a portion of an area of a corresponding sensing element; and

wherein said dielectric material comprises reduced graphene oxide such that a dielectric constant of said dielectric material is higher than a dielectric constant of said coating material, wherein the reduced graphene oxide comprises graphene oxide that has been subjected to a reduction process.

2. The device according to claim 1, wherein the dielectric material is a mold material.

3. The device according to claim 1, wherein the dielectric material is an adhesive material.

4. The device according to claim 3, further comprising a protective plate attached to said fingerprint sensing device by means of said adhesive.

5. The device according to claim 1, wherein a dielectric constant of said dielectric material is in the range of 5 to 100.

6. The device according to claim 1, wherein a dielectric constant of said dielectric material is in the range of 2 to 5.

7. The device according to claim 1, wherein a ratio between said dielectric constant of said dielectric material and said dielectric constant of said coating material is equal to or larger than 2:

1.

8. The device according to claim 1, wherein said dielectric material comprises filler particles comprising reduced graphene oxide, the filler particles having a dielectric constant higher than an average dielectric constant of said mold material.

9. The device according to claim 1, wherein said dielectric material comprises a weight/volume percentage of reduced graphene oxide in the range of 0.01 to 10 wt %.

10. The fingerprint sensing device according to claim 1, further comprising openings between adjacent cavities so that a liquid dielectric material can flow between adjacent cavities.

11. A fingerprint sensing device comprising:

a sensing chip comprising an array of sensing elements, said sensing elements being configured to be connected to readout circuitry for detecting a capacitive coupling between each of said sensing elements and a finger placed on a sensing surface of said sensing device;

a dielectric material arranged in a layer on top of said array of sensing elements, said dielectric material comprising reduced graphene oxide, said dielectric material further comprising a plurality of trenches filled with a fill material, wherein locations of said trenches correspond to areas between adjacent sensing elements;

wherein a dielectric constant of said fill material is lower than a dielectric constant of said dielectric material, wherein the reduced graphene oxide comprises graphene oxide that has been subjected to a reduction process.

12. The device according to claim 11, further comprising a protective plate attached to said fingerprint sensing device by means of an adhesive.

13. The device according to claim 11, wherein a dielectric constant of said dielectric material is in the range of 5 to 100.

14. The device according to claim 11, wherein a dielectric constant of said fill material is in the range of 2 to 5.

15. The device according to claim 11, wherein a ratio between said dielectric constant of said dielectric material and said dielectric constant of said fill material is equal to or larger than 2:

1.

16. The device according to claim 11, wherein said dielectric material comprises filler particles comprising reduced graphene oxide, the filler particles having a dielectric constant higher than an average dielectric constant of said fill material.

17. The device according to claim 11, wherein said dielectric material comprises a weight/volume percentage of reduced graphene oxide in the range of 0.01 to 10 wt %.

18. The device according to claim 11, wherein said fill material is an adhesive or a mold material.