Fingerprint sensing device with heterogeneous coating structure comprising an adhesive
View Patent ↗A fingerprint sensing device comprises 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, the coating material comprising a plurality of cavities filled with an adhesive; wherein 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; and wherein a dielectric constant of the adhesive is higher than a dielectric constant of the coating material; and a protective plate attached to the sensing chip by means of the adhesive. Another sensing device is disclosed, where the coating layer comprises trenches filled with an adhesive, and where the coating has a higher dielectric constant than the adhesive. Associated methods of manufacturing are also disclosed.
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 an adhesive; 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 a dielectric constant of said adhesive is higher than a dielectric constant of said coating material and a dielectric constant of said coating material is in the range of 2-5; and
a protective plate attached to said sensing chip by means of said adhesive.
2. The fingerprint sensing device according to claim 1 , wherein said coating material comprises one cavity for each sensing element.
3. The fingerprint sensing device according to claim 1 , wherein a dielectric constant of said adhesive is in the range of 5-100.
4. The fingerprint sensing device according to claim 1 , wherein a ratio between said dielectric constant of said adhesive and said dielectric constant of said coating material is equal to or larger than 2:1.
5. The fingerprint sensing device according to claim 1 , wherein said adhesive comprises filler particles having a dielectric constant higher than an average dielectric constant of said adhesive.
6. The fingerprint sensing device according to claim 5 , wherein said filler particles comprises a ferroelectric material, such as barium titanate (BaTiO3).
7. The fingerprint sensing device according to claim 1 , wherein each of said cavities comprises at least one lateral opening connecting said cavity to at least one adjacent cavity, enabling a flow of said adhesive between adjacent cavities when depositing said adhesive.
8. The fingerprint sensing device according to claim 1 , wherein said coating material is a photoresist.
9. A method for manufacturing a fingerprint sensing device, said 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 an adhesive; 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 a dielectric constant of said adhesive is higher than a dielectric constant of said coating material and a dielectric constant of said coating material is in the range of 2-5; and a protective plate attached to said sensing chip by means of said adhesive, said method comprising;
providing said sensing chip;
depositing said layer of said coating material covering said array of conductive sensing elements;
forming said plurality of cavities in said coating material;
providing said adhesives to fill said cavities; and
attaching said protective plate to said sensing device by means of said adhesive.
10. The method according to claim 9 , wherein said coating layer is deposited by spin coating or by spray coating.
11. The method according to claim 9 , further comprising plasma cleaning of said coating material prior to the step of providing said adhesive.
12. The method according to claim 9 , wherein providing said adhesive comprises dispensing a liquid adhesive on said layer of coating material and in said cavities.
13. The method according to claim 9 , wherein said coating material is a photoresist, and wherein forming a plurality of cavities in said coating material comprises patterning said layer of coating material by photolithography.
14. 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 trenches filled with an adhesive; wherein said trenches are aligned with areas between said sensing elements; and wherein a dielectric constant of said adhesive is lower than a dielectric constant of said coating material; and
a protective plate attached to said sensing chip by means of said adhesive.
15. A method for manufacturing a fingerprint sensing device, said 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 trenches filled with an adhesive; wherein said trenches are aligned with areas between said sensing elements; and wherein a dielectric constant of said adhesive is lower than a dielectric constant of said coating material; and a protective plate attached to said sensing chip by means of said adhesive, said method comprising;
providing said sensing chip;
depositing said layer of said coating material covering said array of sensing elements;
forming said plurality of trenches in said coating material;
providing said adhesive to fill said trenches; and
attaching said protective plate to said sensing device by means of said adhesive.
16. 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 an adhesive; 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 a dielectric constant of said adhesive is higher than a dielectric constant of said coating material and a ratio between said dielectric constant of said adhesive and said dielectric constant of said coating material is equal to or larger than 2:1; and
a protective plate attached to said sensing chip by means of said adhesive.
17. The fingerprint sensing device according to claim 16 , wherein said coating material comprises one cavity for each sensing element.
18. The fingerprint sensing device according to claim 16 , wherein a dielectric constant of said adhesive is in the range of 5-100.
19. The fingerprint sensing device according claim 16 , wherein a dielectric constant of said coating material is in the range of 2-5.
20. The fingerprint sensing device according to claim 16 , wherein said adhesive comprises filler particles having a dielectric constant higher than an average dielectric constant of said adhesive.
21. The fingerprint sensing device according to claim 20 , wherein said filler particles comprises a ferroelectric material, such as barium titanate (BaTiO3).
22. The fingerprint sensing device according to claim 16 , wherein each of said cavities comprises at least one lateral opening connecting said cavity to at least one adjacent cavity, enabling a flow of said adhesive between adjacent cavities when depositing said adhesive.
23. The fingerprint sensing device according to claim 16 , wherein said coating material is a photoresist.
24. A method for manufacturing a fingerprint sensing device, said 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 an adhesive; 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 a dielectric constant of said adhesive is higher than a dielectric constant of said coating material and a ratio between said dielectric constant of said adhesive and said dielectric constant of said coating material is equal to or larger than 2:1; and a protective plate attached to said sensing chip by means of said adhesive, said method comprising;
providing said sensing chip;
depositing said layer of said coating material covering said array of conductive sensing elements;
forming said plurality of cavities in said coating material;
providing an said adhesive to fill said cavities; and
attaching said protective plate to said sensing device by means of said adhesive.
25. The method according to claim 24 , wherein said coating layer is deposited by spin coating or by spray coating.
26. The method according to claim 24 , further comprising plasma cleaning of said coating material prior to the step of providing said adhesive.
27. The method according to claim 24 , wherein providing said adhesive comprises dispensing a liquid adhesive on said layer of coating material and in said cavities.
28. The method according to claim 24 , wherein said coating material is a photoresist, and wherein forming a plurality of cavities in said coating material comprises patterning said layer of coating material by photolithography.