Reinforcement panel for fingerprint sensor cover
A fingerprint sensor assembly includes a capacitive fingerprint sensor disposed beneath a thin layer of glass and a reinforcement layer of a material of relatively high dielectric constant bonded to the glass between the glass layer and the sensor.
1. A fingerprint sensor assembly for incorporation in a through opening in a cover glass comprising:
a capacitive fingerprint sensor;
a cover layer disposed above the fingerprint sensor, wherein the cover layer is a discrete panel that is separate from the cover glass; and
a reinforcement layer between the fingerprint sensor and the cover layer and bonded or molded to the cover layer.
2. The fingerprint sensor assembly of claim 1 , wherein the reinforcement layer comprises a material selected from the group consisting of: titanium dioxide (TiO 2 ), barium strontium titanate, zirconia, and barium titanate+epoxy based systems.
3. The fingerprint sensor assembly of claim 1 , wherein the reinforcement layer comprises a reinforcement panel bonded to the cover layer by an adhesive, and wherein the adhesive comprises one or more materials selected from the group consisting of: pressure sensitive adhesive, B-staged sheet adhesive, bond ply adhesive, acrylic-based thermoset adhesives, high modulus of elasticity/highly cross-linked, epoxy-type thermoset adhesives, adhesive with particle fillers to increase the modulus of elasticity of the adhesive, and adhesives with filler materials having high dielectric constants.
4. The fingerprint sensor assembly of claim 1 , wherein the reinforcement layer is bonded to the fingerprint sensor, and wherein the adhesive comprises one or more materials selected from the group consisting of: pressure sensitive adhesive, B-staged sheet adhesive, bond ply adhesive, acrylic-based thermoset adhesives, high modulus of elasticity/highly cross-linked, epoxy-type thermoset adhesives, adhesive with particle fillers to increase the modulus of elasticity of the adhesive, and adhesives with filler materials having high dielectric constants.
5. The fingerprint sensor assembly of claim 1 , wherein the cover layer comprises a glass cover.
6. The fingerprint sensor assembly of claim 1 , wherein the cover layer thickness is in the range of 50 to 200 μm and the reinforcement layer thickness is at least 50 μm.
7. The fingerprint sensor assembly of claim 1 , wherein the reinforcement layer comprises a material having flexural strength of at least 400 to 1500 Mpa.
8. The fingerprint sensor assembly of claim 7 , wherein the reinforcement layer comprises a material having flexural strength greater than 1500 Mpa.
9. The fingerprint sensor assembly of claim 1 , wherein the reinforcement layer comprises a material having a fracture toughness of 3.5 to 15 MPam 1/2 .
10. The fingerprint sensor assembly of claim 1 , wherein the reinforcement layer and the cover layer comprise materials having substantially the same coefficient of thermal expansion.
11. The fingerprint sensor assembly of claim 3 , wherein the reinforcement layer is bonded to the fingerprint sensor, and wherein the adhesive comprises one or more materials selected from the group consisting of: pressure sensitive adhesive, B-staged sheet adhesive, bond ply adhesive, acrylic-based thermoset adhesives, high modulus of elasticity/highly cross-linked, epoxy-type thermoset adhesives, adhesive with particle fillers to increase the modulus of elasticity of the adhesive, and adhesives with filler materials having high dielectric constants.
12. The fingerprint sensor assembly of claim 11 , wherein the cover layer comprises a glass cover.
13. The fingerprint sensor assembly of claim 2 , wherein the cover layer thickness is in the range of 50 to 200 μm and the reinforcement layer thickness is at least 50 μm.
14. The fingerprint sensor assembly of claim 6 , wherein the reinforcement layer comprises a material having flexural strength of at least 400 to 1500 Mpa.
15. The fingerprint sensor assembly of claim 7 , wherein the reinforcement layer comprises a material having a fracture toughness of 3.5 to 15 MPam 1/2 .
16. The fingerprint sensor assembly of claim 5 , wherein the reinforcement layer and the cover layer comprise materials having substantially the same coefficient of thermal expansion.
17. The fingerprint sensor assembly of claim 2 , wherein the reinforcement layer comprises a reinforcement panel bonded to the cover layer by an adhesive, and wherein the adhesive comprises one or more materials selected from the group consisting of: pressure sensitive adhesive, B-staged sheet adhesive, bond ply adhesive, acrylic-based thermoset adhesives, high modulus of elasticity/highly cross-linked, epoxy-type thermoset adhesives, adhesive with particle fillers to increase the modulus of elasticity of the adhesive, and adhesives with filler materials having high dielectric constants.
18. The fingerprint sensor assembly of claim 17 , wherein the reinforcement layer is bonded to the fingerprint sensor, and wherein the adhesive comprises one or more materials selected from the group consisting of: pressure sensitive adhesive, B-staged sheet adhesive, bond ply adhesive, acrylic-based thermoset adhesives, high modulus of elasticity/highly cross-linked, epoxy-type thermoset adhesives, adhesive with particle fillers to increase the modulus of elasticity of the adhesive, and adhesives with filler materials having high dielectric constants.
19. The fingerprint sensor assembly of claim 5 , wherein the cover layer thickness is in the range of 50 to 200 μm and the reinforcement layer thickness is at least 50 μm.
20. The fingerprint sensor assembly of claim 1 , wherein the cover layer comprises a material having a dielectric constant of less than 10 and a thickness in the range of 50 to 300 μm.
21. The fingerprint sensor assembly of claim 1 , wherein the reinforcement layer comprises a material having a dielectric constant of at least 20 and having a thickness of 10% to 200% of the thickness of the cover layer.