Flexible circuit board and method of fabricating

• US 9,661,743 B1
• Filed: 12/09/2014
• Issued: 05/23/2017
• Est. Priority Date: 12/09/2013
• Status: Active Grant

• Current Assignee: Multek Technologies Limited
• Original Assignee: Multek Technologies Limited
• Inventors: Bergman, Mark, Vrtis, Joan K.
• Primary Examiner(s): Nguyen, Chau
• Assistant Examiner(s): Varghese, Roshn
• Application Number:
  US14/565,247
• Time in Patent Office: 896 Days
• CPC Class Codes: A41D 1/002 adapted to accommodate electronic equipment patients' garments for medical monitoring A41D13/1281; luminous ornaments A41D27/085
• CPC Class Codes: A41D 1/005 with embedded cable or connector
• CPC Class Codes: D05B 17/00 Sewing machines for concurrently making thread and welded seams for making non-welded fluid-tight seams D05B1/26
• CPC Class Codes: H01M 10/0436 Small-sized flat cells or batteries for portable equipment
• CPC Class Codes: H01M 6/12 with flat electrodes
• CPC Class Codes: H01M 6/40 Printed batteries , e.g. thin film batteries
• CPC Class Codes: H01R 4/00 Electrically-conductive connections between two or more conductive members in direct contact, i.e. touching one another; Means for effecting or maintaining such contact; Electrically-conductive connections having two or more spaced connecting locations for conductors and using contact members penetrating insulation
• CPC Class Codes: H01R 4/02 Soldered or welded connections H01R4/625, H01R4/723, H01R12/59 take precedence
• CPC Class Codes: H01R 4/029 Welded connections H01R4/021 - H01R4/028 take precedence
• CPC Class Codes: H01R 43/005 for making dustproof, splashproof, drip-proof, waterproof, or flameproof connection, coupling, or casing
• CPC Class Codes: H01R 43/02 for soldered or welded connections
• CPC Class Codes: H01R 43/0235 for applying solder H01R43/0228 takes precedence
• CPC Class Codes: H05K 1/0271 Arrangements for reducing stress or warp in rigid printed circuit boards, e.g. caused by loads, vibrations or differences in thermal expansion
• CPC Class Codes: H05K 1/0296 Conductive pattern lay-out details not covered by sub groups H05K1/02 - H05K1/0295 H05K1/11 takes precedence; lay-out adapted to mounted component configuration H05K1/18
• CPC Class Codes: H05K 1/0298 Multilayer circuits
• CPC Class Codes: H05K 1/0306 Inorganic insulating substrates, e.g. ceramic, glass
• CPC Class Codes: H05K 1/0366 reinforced, e.g. by fibres, fabrics H05K1/036 takes precedence
• CPC Class Codes: H05K 1/0373 containing additives, e.g. fillers H05K1/036 takes precedence
• CPC Class Codes: H05K 1/038 Textiles used as reinforcing materials for organic insulating substrates H05K1/0366
• CPC Class Codes: H05K 1/0393 Flexible materials H05K1/038 takes precedence; specific organic compositions are classified in H05K1/0313 and subgroups
• CPC Class Codes: H05K 1/09 : Use of materials for the conductive, e.g. metallic pattern
• CPC Class Codes: H05K 1/11 : Printed elements for providing electric connections to or between printed circuits
• CPC Class Codes: H05K 1/111 : Pads for surface mounting, e.g. lay-out
• CPC Class Codes: H05K 1/112 : directly combined with via connections
• CPC Class Codes: H05K 1/115 : Via connections; Lands around holes or via connections H05K1/112 takes precedence
• CPC Class Codes: H05K 1/18 : Printed circuits structurally associated with non-printed electric components H05K1/0201, H05K1/023, H05K1/0243, and H05K1/16 take precedence
• CPC Class Codes: H05K 1/181 : associated with surface mounted components
• 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 13/04 : Mounting of components , e.g. of leadless components
• CPC Class Codes: H05K 2201/0154 : Polyimide
• CPC Class Codes: H05K 2201/0158 : Polyalkene or polyolefin, e.g. polyethylene [PE], polypropylene [PP]
• CPC Class Codes: H05K 2201/0162 : Silicon containing polymer, e.g. silicone
• CPC Class Codes: H05K 2201/0287 : Unidirectional or parallel fibers
• CPC Class Codes: H05K 2201/05 : Flexible printed circuits [FPCs]
• CPC Class Codes: H05K 2201/09418 : Special orientation of pads, lands or terminals of component, e.g. radial or polygonal orientation
• CPC Class Codes: H05K 3/284 : for encapsulating mounted components H05K1/185 takes precedence
• CPC Class Codes: H05K 3/30 : Assembling printed circuits with electric components, e.g. with resistor
• CPC Class Codes: H05K 3/305 : Affixing by adhesive
• CPC Class Codes: H05K 3/32 : electrically connecting electric components or wires to printed circuits
• CPC Class Codes: H05K 3/4015 : using auxiliary conductive elements, e.g. pieces of metal foil, metallic spheres
• CPC Class Codes: H05K 3/42 : Plated through-holes or plated via connections
• CPC Class Codes: H05K 3/4644 : by building the multilayer layer by layer, i.e. build-up multilayer circuits making via holes in the insulating layers H05K3/0011; special circuit boards as base or core whereon the multilayer is built H05K3/4602
• CPC Class Codes: H05K 7/02 : Arrangements of circuit components or wiring on supporting structure
• CPC Class Codes: H05K 9/009 : comprising electro-conductive fibres, e.g. metal fibres, carbon fibres, metallised textile fibres, electro-conductive mesh, woven, non-woven mat, fleece, cross-linked
• CPC Class Codes: Y02E 60/10 : Energy storage using batteries
• CPC Class Codes: Y02P 70/50 : Manufacturing or production processes characterised by the final manufactured product

Abstract

A flexible circuit board includes a center “rigid” section, such as a printed circuit stack, and an adjoining flexible multi-layer body that are fabricated from a common interconnect layer. A transition material is included at the interface between the center rigid section and the flexible multi-layer body to minimize ripping and cracking of the interconnect layer. The transition material can also be added at stress areas not related to the interface. The transition material is attached at the interface and stress areas of the flexible circuit board in order to strengthen the flexible circuit board in general and in particular the transition material included therein. The transition material layer is formed and deposited at one or more locations on or within the flexible circuit board in order to minimize, reduce, if not prevent cracking and ripping of the flexible circuit board as it is bent, flexed and/or twisted.

Claims

1. A flexible circuit board comprising:

a. a flexible multi-layer body comprising an interconnect layer, a first flexible insulating layer and a second flexible insulating layer, wherein the interconnect layer comprises a first surface and a second surface opposite the first surface, further wherein the first flexible insulating layer is in contact with the first surface of the interconnect layer and the second flexible insulating layer is in contact with the second surface of the interconnect layer;

b. a center section that is more rigid than the flexible multi-layer body, wherein the center section comprises the interconnect layer such that the interconnect layer extends as a common layer to both the flexible multi-layer body and the center section, further wherein the center section further comprises a first printed circuit stack stacked on the first surface of the interconnect layer and a second printed circuit stack stacked on the second surface of the interconnect layer, the first printed circuit stack and the second printed circuit stack each comprising one or more rigid or flexible layers and one or more pre-preg or adhesive layers; and

c. a transition material positioned at one or more transition locations between the flexible multi-layer body and the center section in order to provide structural support, wherein the transition material has a lower elasticity than first and second flexible insulating layers of the flexible multi-layer body and a higher elasticity than the center section, further wherein a first portion of the transition material extends partially into the center section such that the first portion is positioned between the first surface of the interconnect layer and the first printed circuit stack, and a second portion of the transition material extends partially into the flexible multi-layer body such that the second portion is positioned between the first surface of the interconnect layer and the first flexible insulating layer, wherein the transition material occupies a position overlapping a first portion of the center section adjacent to the flexible multi-layer body while a remaining second portion of the center section is unoccupied by the transition material, further wherein the transition material further occupies a position overlapping a first portion of the flexible multi-layer body adjacent to the first portion of the center section while a remaining second portion of the flexible multi-layer body is unoccupied by the transition material.

2. The flexible circuit board of claim 1 wherein the transition material is configured to minimize, reduce, if not prevent the flexible multi-layer body from cracking as the flexible multi-layer body is flexed, bent or twisted.

3. The flexible circuit board of claim 1 wherein the transition material has a lower elasticity than the first and second flexible insulating layers of the flexible multi-layer body, but a higher elasticity than the center section.

4. The flexible circuit board of claim 1 wherein the transition material is positioned at a high stress location of the flexible circuit board.

5. The flexible circuit board of claim 1 wherein the transition material comprises an open weave interlocking fabric.

6. The flexible circuit board of claim 1 wherein the rigid sections comprise one of glass-filled material, pre-preg or foil laminates.

7. The flexible circuit board of claim 1 wherein the flexible sections comprise one of polyimide, polyethylene teraphthalate (PET), polyethylene nitride (PEN) or polyurethane.

8. The flexible circuit board of claim 1 wherein the first and second flexible insulating layers comprise one of silicone or polyurethane.

9. The flexible circuit board of claim 1 wherein the interconnect layer comprises a copper foil patterned to form one or more interconnects.

10. The flexible circuit board of claim 1 wherein a remaining portion of the first surface of the interconnect layer is unoccupied by the transition material.

11. The flexible circuit board of claim 1 further comprising a second transition material wherein a first portion of the second transition material extends partially into the center section such that the first portion of the second transition material is positioned between the second surface of the interconnect layer and the second printed circuit stack, and a second portion of the second transition material extends partially into the flexible multi-layer body such that the second portion of the second transition material is positioned between the second surface of the interconnect layer and the second flexible insulating layer.

12. A flexible circuit board comprising:

a. a flexible multi-layer body comprising an interconnect layer, a first stretchable insulating layer and a second stretchable insulating layer, wherein the interconnect layer comprises a first surface and a second surface opposite the first surface, further wherein the first stretchable insulating layer is in contact with the first surface of the interconnect layer and the second stretchable insulating layer is in contact with the second surface of the interconnect layer, wherein

the interconnect layer includes interconnects formed in a non-linear pattern to allow the interconnect layer to be stretched;

b. a center section that is more rigid than the flexible multi-layer body, wherein the center section comprises the interconnect layer such that the interconnect layer extends as a common layer to both the flexible multi-layer body and the center section, further wherein the center section further comprises a first printed circuit stack stacked on the first surface of the interconnect layer and a second printed circuit stack stacked on the second surface of the interconnect layer, the first printed circuit stack and the second printed circuit stack each comprising one or more rigid or flexible layers and one or more pre-preg or adhesive layers; and

c. a transition material positioned at one or more transition locations between the flexible multi-layer body and the center section in order to provide structural support, wherein the transition material has a lower elasticity than the first and second stretchable insulating layers of the flexible multi-layer body and a higher elasticity than the center section, further wherein a first portion of the transition material extends partially into the center section such that the first portion is positioned between the first surface of the interconnect layer and the first printed circuit stack, and a second portion of the transition material extends partially into the flexible multi-layer body such that the second portion is positioned between the first surface of the interconnect layer and the first stretchable insulating layer, wherein the transition material occupies a position overlapping a first portion of the center section adjacent to the flexible multi-layer body while a remaining second portion of the center section is unoccupied by the transition material, further wherein the transition material further occupies a position overlapping a first portion of the flexible multi-layer body adjacent to the first portion of the center section while a remaining second portion of the flexible multi-layer body is unoccupied by the transition material.

13. The flexible circuit board of claim 12 wherein the non-linear pattern of the interconnects forms an S-shape or a zig-zap shape.

14. The flexible circuit board of claim 12 wherein the transition material is configured to minimize, reduce, if not prevent the flexible multi-layer body from cracking as the flexible multi-layer body is flexed, bent or twisted.

15. The flexible circuit board of claim 12 wherein the transition material has a lower elasticity than the first and second stretchable insulating layers of the flexible multi-layer body, but a higher elasticity than the center section.

16. The flexible circuit board of claim 12 wherein the transition material is positioned at a high stress location of the flexible circuit board.

17. The flexible circuit board of claim 12 wherein the transition material comprises an open weave interlocking fabric.

18. The flexible circuit board of claim 12 wherein the rigid sections comprise one of glass-filled material, pre-preg or foil laminates.

19. The flexible circuit board of claim 12 wherein the flexible sections comprise one of polyimide, polyethylene teraphthalate (PET), polyethylene nitride (PEN) or polyurethane.

20. The flexible circuit board of claim 12 wherein the first and second stretchable insulating layers comprise one of silicone or polyurethane.