Method of fabricating capacitive touch switch panel

• US 4,293,987 A
• Filed: 12/21/1979
• Issued: 10/13/1981
• Est. Priority Date: 03/16/1978
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Shepherd, Glen C., Gottbreht, Tom L.
• Primary Examiner(s): Hall, Carl E.
• Application Number:
  US06/106,294
• Time in Patent Office: 662 Days
• Field of Search: 29/25.42, 29/830, 219/10.55 R, 219/10.55 B, 219/10.55 C, 219/10.55 M, 219/506, 200/52 R, 200/DIG. 1, 200/5 A, 200/268, 200/269, 200/292, 361/280, 361/306, 361/313
• US Class Current: 29/25.42
• CPC Class Codes: H01H 2207/004 Printed circuit tail
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 2017/9613 using two electrodes per touch switch
• CPC Class Codes: H03K 2217/96023 Details of electro-mechanic connections between different elements, e.g.: sensing plate and integrated circuit containing electronics
• CPC Class Codes: H05B 6/6435 Aspects relating to the user interface of the microwave heating apparatus
• CPC Class Codes: Y10T 29/435 Solid dielectric type
• CPC Class Codes: Y10T 29/49126 Assembling bases

Abstract

An improved technique for the manufacture of capacitive touch switch panel assemblies, utilized to control appliances and the like, provides simplified construction and manufacture. The technique involves the formation of conductive touch pads on one major surface of a dielectric panel and the formation of pairs of spaced-apart conductive pads and conductive lead members to the conductive pads on a separate flexible synthetic resin sheet. The synthetic resin is bonded to the opposite major surface of the dielectric panel with each pair of conductive pads on the synthetic resin sheet in registry with a corresponding touch pad on the one major surface of the dielectric panel. The synthetic resin sheet includes a portion having a conductive lead pattern formed thereon which is not bonded to the dielectric panel; this portion serves as a flexible connector for connection of the touch panel to a circuit board or the like. In one embodiment, the conductive lead pattern includes an interconnection pattern for circuit elements such as integrated circuits or display elements mounted on the synthetic resin sheet or the dielectric panel. The conductive lead pattern on the synthetic resin sheet may be a single-layer or a multi-layer pattern and the conductor may be formed from a single material or different materials having predetermined resistive characteristics whereby external resistors to the capacitive touch switches and/or circuit elements may be eliminated from the circuit.

Claims

1. A method of fabricating a capacitive touch switch panel comprising the steps of:

(a) forming conductive touch pads on one major surface of a rigid dielectric panel;

(b) forming pairs of spaced-apart conductive pads and conductive leads extending to said conductive pads on one of two opposite major surfaces of a flexible synthetic resin sheet; and

(c) bonding the second of the said two opposite surfaces of said flexible synthetic resin sheet to the opposite major surface of said rigid dielectric panel with each of said pairs of conductive pads in registered alignment with a respective one of said conductive touch pads.

2. The method according to claim 1 wherein said flexible sheet is bonded to said dielectric panel by applying an adhesive between said panel and said sheet.

3. The method according to claim 1 including the step of cutting said flexible synthetic resin sheet essentially to the shape of said dielectric panel plus an extension portion, said extension portion having at least some of said conductive leads formed thereon for external connection of said capacitive touch switch panel.

4. The method according to claim 1 wherein said conductive touch pads are formed by vapor deposition of a conductive material.

5. The method according to claim 4 wherein said dielectric panel is comprised of glass and wherein tin oxide conductive touch pads are formed on said one major surface by forming a mask on said glass panel and spraying stannous fluoride over said glass panel and mask at about 1250°

F.

6. The method according to claim 1 wherein said conductive touch pads are formed by painting a conductive material on said dielectric panel.

7. The method according to claim 1 wherein said conductive touch pads are formed on said dielectric panel by silk screening a conductive material on said dielectric panel.

8. The method according to claim 1 including the steps of mounting a circuit element on said flexible synthetic resin sheet and connecting said circuit element to said conductive lead members.

9. The method according to claim 8 wherein said circuit element is a semiconductor integrated circuit.

10. The method according to claim 8 wherein said circuit element is a display element.

11. The method according to claim 1 including the steps of mounting a circuit element on said opposite major surface of said dielectric panel and connecting said circuit element to said conductive lead members.

12. The method according to claim 11 wherein said circuit element is a semiconductor integrated circuit.

13. The method according to claim 11 wherein said circuit element is a display element.

14. The method according to claim 1 wherein said synthetic resin sheet is comprised of a polyester material.

15. The method according to claim 1 wherein said synthetic resin sheet is comprised of a polycarbonate material.

16. The method according to claim 1 wherein said synthetic resin sheet is comprised of a polyimide material.

17. The method according to claim 1 wherein said pairs of spaced-apart conductive pads are formed by silk screening a conductive material on said flexible sheet.

18. The method according to claim 17 wherein said conductive material is comprised of silver.

19. The method according to claim 1 wherein said pairs of conductive pads are formed by vapor depositing a conductive material on said sheet.

20. The method according to claim 19 wherein said material is comprised of silver.

21. The method according to claim 19 wherein said material is comprised of aluminum.

22. The method according to claim 1 wherein said pairs of spaced-apart conductive pads are formed by painting a conductive material on said sheet.

23. The method according to claim 22 wherein said material is comprised of silver.

24. The method according to claim 22 wherein the material is comprised of resistive carbon.

25. The method according to claim 1 including the step of folding a portion of said flexible sheet over another portion thereof to provide multi-layers of said conductive lead members with insulation provided by said flexible sheet therebetween.

26. A method of fabricating a capacitive touch switch panel assembly comprising the steps of:

(a) forming conductive touch pads on one major surface of a rigid dielectric panel;

(b) forming pairs of spaced-apart conductive pads and conductive leads extending to said conductive pads on a major surface of a flexible synthetic resin sheet;

(c) cutting said flexible sheet essentially to the shape of said dielectric panel leaving an extra flexible extension portion, said extension portion having at least some of said conductive leads formed thereon;

(d) bonding said flexible sheet to the opposite major surface of said rigid dielectric panel with each of said pairs of spaced-apart conductive pads in registration with a respective one of said conductive touch pads;

(e) mounting said rigid dielectric panel and a circuit board in fixed relation with respect to each other; and

(f) connecting the conductive leads formed on said flexible extension portion to respective conductors located on said printed circuit board.

27. The method according to claim 26 wherein said printed circuit board includes a socket member mounted thereon and said extension portion is plugged into said socket member to provide electrical connection therebetween.

28. The method according to claim 26 wherein said dielectric panel is comprised of glass and wherein tin oxide conductive touch pads are formed on said one major surface by:

forming a mask on said glass panel, spraying stannous fluoride over said glass panel and mask at about 1250°

F. and removing said mask.

29. The method according to claim 26 wherein said spaced-apart conductive pads are formed on said flexible sheet by silk screening a silver comprising material on said flexible sheet.

30. The method according to claim 26 wherein said synthetic resin sheet is comprised of a polyester material.

31. The method according to claim 26 wherein at least some of said conductive leads are formed of resistive carbon to provide a path of predetermined resistance to said at least some conductors.

32. The method according to claim 26 wherein said flexible sheet is bonded to said dielectric panel by applying an adhesive between said panel and said sheet.