CONDUCTIVE STIFFENER, METHOD OF MAKING A CONDUCTIVE STIFFENER, AND CONDUCTIVE ADHESIVE AND ENCAPSULATION LAYERS

• US 20170019988A1
• Filed: 07/12/2016
• Published: 01/19/2017
• Est. Priority Date: 07/17/2015
• Status: Active Grant

• Current Assignee: Medidata Solutions Incorporated (Dassault Systemes SA)
• Original Assignee: MC10, Inc.
• Inventors: McGrane, Bryan, Raj, Milan, Wei, PingHung, Lin, Monica, Morey, Briana, Ghaffari, Roozbeh, Model, Jeffrey, Wang, Xianyan, Keen, Bryan, Lee, Stephen
• Granted Patent: US 10,653,332 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2562/164 the sensor is mounted in or on a conformable substrate or carrier
• CPC Class Codes: A61B 2562/166 the sensor is mounted on a specially adapted printed circuit board
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/25 Bioelectric electrodes therefor
• CPC Class Codes: A61B 5/291 for electroencephalography [EEG]
• CPC Class Codes: A61B 5/296 for electromyography [EMG]
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16
• CPC Class Codes: A61B 5/389 Electromyography [EMG]
• CPC Class Codes: A61B 5/398 Electrooculography [EOG], e.g. detecting nystagmus; Electroretinography [ERG]
• CPC Class Codes: A61B 5/6801 specially adapted to be attached to or worn on the body surface
• CPC Class Codes: H05K 1/0209 External configuration of printed circuit board adapted for heat dissipation, e.g. lay-out of conductors, coatings
• CPC Class Codes: H05K 1/0283 Stretchable printed circuits
• CPC Class Codes: H05K 1/189 characterised by the use of a flexible or folded printed circuit H05K3/326 takes precedence
• CPC Class Codes: H05K 2201/0969 Apertured conductors
• CPC Class Codes: H05K 2201/10106 Light emitting diode [LED]
• CPC Class Codes: H05K 2201/10151 Sensor
• CPC Class Codes: H05K 2201/10401 Eyelets, i.e. rings inserted into a hole through a circuit board
• CPC Class Codes: H05K 2201/2009 Reinforced areas, e.g. for a specific part of a flexible printed circuit
• CPC Class Codes: H05K 2203/1327 : Moulding over PCB locally or completely applying non-metallic protective coatings for encapsulating mounted components H05K3/284

Abstract

A wearable device includes a flexible printed circuit board and one or more conductive stiffeners. The conductive stiffeners include a conductive surface that can be electrically or thermally connected to contact pads on the flexible printed circuit board. The wearable device can further include an adhesive layer or an encapsulation layer. The adhesive layer and the encapsulation layer can include conductive portions surrounded by non-conductive portions. The conductive portions can be aligned with the conductive stiffeners and together transmit electrical and/or thermal energy to the contact pads of the flexible printed circuit board.

Claims

1. A device comprising:

a flexible printed circuit board having a plurality of discrete operative devices electrically interconnected and one or more contact pads on a backside of the flexible printed circuit board; and

a plurality of conductive stiffeners affixed to the backside of the flexible printed circuit board, wherein each conductive stiffener electrically connects at least one contact pad of the flexible printed circuit board to a bottom surface of the conductive stiffener.

2. The device of claim 1, further comprising an encapsulation layer encapsulating the flexible printed circuit board and the plurality of conductive stiffeners.

3. The device of claim 2, wherein the encapsulation layer comprises non-conductive areas surrounding conductive areas, and the conductive areas are aligned with the bottom surfaces of the conductive stiffeners.

4. The device of claim 2, wherein a bottom surface of each conductive stiffener includes one or more indentations that interface with the encapsulation layer to mechanically couple the encapsulation layer to the plurality of conductive stiffeners.

5. The device of claim 4, wherein the one or more indentations are vertical interconnects accesses.

6. The device of claim 2, wherein a bottom surface of the flexible printed circuit board includes one or more indentations that interface with the encapsulation layer to mechanically couple the encapsulation layer to the flexible printed circuit board.

7. The device of claim 2, wherein at least one end of the flexible printed circuit board is folded creating a pocket, and the pocket is filled with encapsulation material forming the encapsulation layer to mechanically couple the encapsulation layer to the flexible printed circuit board.

8. The device of claim 7, wherein the at least one end of the flexible printed circuit board includes one or more vertical interconnect accesses, and the encapsulation material fills the one or more vertical interconnect accesses from the pocket through the at least one end to mechanically couple the encapsulation layer to the flexible printed circuit board.

9. The device of claim 1, wherein each of the conductive stiffeners includes a vertical interconnect access (VIA) through which the conductive stiffeners attach to the corresponding discrete operative device.

10. The device of claim 1, wherein each conductive stiffener comprises:

a non-conductive substrate sheet;

a hole through the non-conductive substrate sheet; and

a conductive material forming a pad on a bottom surface of the non-conductive substrate sheet and lining the hole, wherein the pad of conductive material is electrically connected to a top surface of the non-conductive substrate sheet through the conductive material lining the hole.

11. The device of claim 10, wherein the non-conductive substrate sheet is comprised of at least two FR-4 glass-reinforced epoxy laminate sheets.

12. The device stiffener of claim 11, wherein each sheet of the at least two sheets is 0.002 inches thick.

13. The device of claim 11, wherein the at least two sheets are adhered together with an adhesive layer.

14. The device of claim 13, wherein the adhesive layer is 0.002 inches thick.

15. The device of claim 10, wherein the conductive material is selected from a group consisting of copper, tin, nickel, silver, and gold.

16. The device of claim 10, wherein the pad of conductive material on the bottom surface is 0.0014 inches thick.

17. The device of claim 10, wherein the conductive material forms a pad on the top surface of the non-conductive substrate sheet.

18. The device of claim 17, wherein the pad of conductive material on the top surface comprises a thermal relief pattern in the conductive material surrounding the hole.

19. The device of claim 17, wherein the pad of conductive material on the top surface is 0.0014 inches thick.

20. A conductive stiffener comprising:

a non-conductive substrate sheet;

a hole through the non-conductive substrate sheet; and

a conductive material forming a pad on a bottom surface of the non-conductive substrate sheet and lining the hole, wherein the pad of conductive material is electrically connected to a top surface of the non-conductive substrate sheet through the conductive material lining the hole.

21. The conductive stiffener of claim 20, wherein the non-conductive substrate sheet is comprised of at least two FR-4 glass-reinforced epoxy laminate sheets.

22. The conductive stiffener of claim 21, wherein each sheet of the at least two sheets is 0.002 inches thick.

23. The conductive stiffener of claim 21, wherein the at least two sheets are adhered together with an adhesive layer.

24. The conductive stiffener of claim 23, wherein the adhesive layer is 0.002 inches thick.

25. The conductive stiffener of claim 20, wherein the conductive material is selected from a group consisting of copper, tin, nickel, silver, and gold.

26. The conductive stiffener of claim 20, wherein the pad of conductive material on the bottom surface is 0.0014 inches thick.

27. The conductive stiffener of claim 20, wherein the conductive material forms a pad on the top surface of the non-conductive substrate sheet.

28. The conductive stiffener of claim 27, wherein the pad of conductive material on the top surface comprises a thermal relief pattern in the conductive material surrounding the hole.

29. The conductive stiffener of claim 27, wherein the pad of conductive material on the top surface is 0.0014 inches thick.

30. A method of forming a conductive stiffener comprising:

adhering at least two non-conductive substrate sheets together with an adhesive to form a stiffener;

forming a hole through the stiffener;

forming a layer of conductive material on the stiffener, wherein the conductive material is formed within the hole and electrically connects pads of the conductive material formed on opposite surfaces of the stiffener;

forming a resist on the pad of conductive material on a top surface of the stiffener according to a thermal relief pattern surrounding the hole; and

removing conductive material exposed by the resist to form the thermal relief pattern in the pad of conductive material on the top surface.

31. The method of claim 30, further comprising forming an additional layer of the conductive material above remaining portions of the conductive material after removing the exposed conductive material.

32. The method of claim 31, further comprising plating the stiffener according to an electroless nickel immersion gold process after forming the additional layer.

33. The method of claim 30, wherein the at least two non-conductive substrate sheets comprise FR-4 glass-reinforced epoxy laminate sheets.

34. The method of claim 30, wherein the conductive material is selected from a group consisting of copper, tin, nickel, silver, and gold.

35. The method of claim 30, wherein the resist material is an ultraviolet light resist material, and the conductive material is copper.

36. A method of stiffening a flexible printed circuit board comprising:

adhering non-conductive substrate sheets together with an adhesive to form a stiffener;

forming a hole through the stiffener;

forming a layer of conductive material on the stiffener, wherein the conductive material is formed within the hole and electrically connects pads of the conductive material formed on opposite surfaces of the stiffener;

forming a resist layer on the pad of conductive material on a top surface of the stiffener according to a thermal relief pattern surrounding the hole;

removing conductive material exposed by the resist to form the thermal relief pattern in the pad of conductive material on the top surface;

applying an adhesive to the top surface;

adhering the stiffener to a bottom surface of the flexible printed circuit board with the hole aligned with a contact pad on the bottom surface of the flexible printed circuit board; and

filling the hole with a lead free solder to attach the stiffener to the bottom surface of the flexible printed circuit board,

wherein the conductive material on a bottom surface of the stiffener is electrically connected to the contact pad on the bottom surface of the flexible printed circuit board.

37. The method of claim 36, wherein the non-conductive substrate sheets comprise FR-4 glass-reinforced epoxy laminate sheets.

38. The method of claim 36, wherein the conductive material is selected from a group consisting of copper, silver, and gold.

39. The method of claim 36, wherein the resist material is an ultraviolet photoresist material, and the conductive material is copper.

40. The method of claim 36, further comprising forming an additional layer of the conductive material above remaining portions of the conductive material after removing the conductive material exposed by the resist.

41. The method of claim 40, further comprising plating the stiffener according to an electroless-nickel immersion gold process after forming the additional layer.

42. The method of claim 36, further comprising encapsulating the flexible printed circuit board and the stiffener with an encapsulation material.

43. The method of claim 42, wherein the encapsulation material is non-conductive with a conductive portion aligned with the bottom surface of the stiffener.