Flexible circuit board assembly and method

• US 5,434,362 A
• Filed: 09/06/1994
• Issued: 07/18/1995
• Est. Priority Date: 09/06/1994
• Status: Expired due to Term

• Current Assignee: Continental Automotive Systems, Inc. (Continental AG)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Klosowiak, Tomasz L., Mui, Gary K., Currier, David W.
• Primary Examiner(s): Picard, Leo P.
• Assistant Examiner(s): Thomas, L.
• Application Number:
  US08/300,762
• Time in Patent Office: 315 Days
• Field of Search: 174/254, 361/748, 439/67, 439/77
• US Class Current: 174/254
• CPC Class Codes: H05K 1/028 Bending or folding regions of flexible printed circuits H05K1/0283 takes precedence
• CPC Class Codes: H05K 1/0281 Reinforcement details thereof
• 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 2201/09063 Holes or slots in insulating substrate not used for electrical connections
• CPC Class Codes: H05K 2201/09109 Locally detached layers, e.g. in multilayer
• CPC Class Codes: H05K 2201/09745 Recess in conductor, e.g. in pad or in metallic substrate
• CPC Class Codes: H05K 2201/09781 Dummy conductors, i.e. not used for normal transport of current; Dummy electrodes of components
• CPC Class Codes: H05K 2201/2009 Reinforced areas, e.g. for a specific part of a flexible printed circuit
• CPC Class Codes: H05K 3/0061 onto a metallic substrate, e.g. a heat sink heat sinks for electric apparatus H05K7/20
• CPC Class Codes: H05K 5/003 having an integrally preformed housing

Abstract

A flexible circuit board assembly (10) includes a flexible substrate (11) having first and second end portions (14,15) and an intermediate portion (16). Conductive metalization interconnect paths (17) extend between the substrate end portions (14, 15) and across the intermediate portion (16). The substrate first and second end portions are mounted to first and second end portions (21, 22) of a rigidizer plate (20). Stiffening material (35) is provided on the flexible substrate intermediate portion (16) to define stiff (36, 37, 38) and less stiff (39, 40) paths that extend across the interconnect paths (17) and the substrate intermediate portion (16) and define desired bend curvature characteristics for the flexible substrate intermediate portion (16). A method utilizes this structure to provide a flexible circuit board assembly (10), preferably with a bent rigidizer plate (20).

Claims

1. Flexible circuit board assembly comprising:

flexible substrate of electrically insulating material having a predetermined thickness and a top surface extending between first and second end portions of said flexible substrate with an intermediate portion of said flexible substrate located therebetween;

a plurality of conductive metalization interconnect paths fixed to said flexible substrate, each of said interconnect paths extending from at least said substrate first end portion, across said substrate intermediate portion, to said substrate second end portion;

first and second end portions of a rigidizer plate, said first and second flexible substrate end portions mounted to said first and second end portions of said rigidizer plate, respectively, with said substrate intermediate portion comprising an unmounted portion of said flexible substrate between said first and second end portions of said rigidizer plate; and

stiffening material selectively provided on said flexible substrate intermediate portion to define varying areas of stiffness for the flexible substrate intermediate portion which varying areas of stiffness define at least 2 stiff paths for the flexible substrate intermediate portion, with a less stiff path for the flexible substrate intermediate portion between the stiff paths, said stiff and less stiff paths extending across the flexible substrate intermediate portion and across the conductive metalization interconnect paths, said stiff and less stiff paths defining desired bend curvature characteristics for the flexible substrate intermediate portion.

2. Flexible circuit board assembly according to claim 1 wherein first and second rigidizer plate end portions are bonded to said first and second substrate end portions, respectively, by a bonding material positioned therebetween, with said substrate intermediate portion comprising an unbonded portion of said flexible substrate between said first and second rigidizer plate portions.

3. Flexible circuit board assembly according to claim 1 wherein said stiffening material comprises added metalization areas provided on said intermediate substrate portion.

4. Flexible circuit board assembly according to claim 3 wherein said added metalization areas are separate from said conductive metalization interconnect paths.

5. Flexible circuit board assembly according to claim 3 wherein said added metalization areas are extensions of and are connected to said conductive metalization interconnect paths.

6. Flexible circuit board assembly according to claim 1 wherein said at least 2 stiff paths define two substantially parallel stiff paths across said intermediate portion of said flexible substrate.

7. Flexible circuit board assembly according to claim 6 wherein said rigidizer plate is preformed to define at least two parallel preferential bend axes extending across said interconnect paths of said intermediate portion of said flexible substrate.

8. Flexible circuit board assembly according to claim 7 wherein said bend axes are substantially parallel to said stiff paths.

9. Flexible circuit board assembly according to claim 7 wherein said rigidizer plate is formed with a pair of channels therein, each channel corresponding to one of said bend axes.

10. Flexible circuit board assembly according to claim 1 wherein said first and second rigidizer plate end portions are portions of a single rigidizer plate which has been bent along at least one bend axis which extends across said interconnect paths of said intermediate portion of said flexible substrate such that said first and second rigidizer plate portions are non coplanar.

11. Flexible circuit board assembly according to claim 1 wherein first and second rigidizer plate end portions are bonded to said first and second substrate end portions, respectively, by bonding material positioned therebetween, with said substrate intermediate portion comprising an unbonded portion of said flexible substrate between said first and second rigidizer plate end portions.

12. Flexible circuit board assembly according to claim 11 wherein said stiffening material comprises added metalization areas provided on said intermediate substrate portion.

13. Flexible circuit board assembly according to claim 12 wherein said added metalization areas are separate from said conductive metalization interconnect paths.

14. Flexible circuit board assembly according to claim 12 wherein said added metalization areas are extensions of and are connected to said conductive metalization interconnect paths.

15. Flexible circuit board assembly according to claim 10 wherein said at least 2 stiff paths define two parallel stiff paths across said intermediate portion of said flexible substrate.

16. Flexible circuit board assembly according to claim 15 wherein said rigidizer plate is preformed to define at least two substantially parallel preferential bend axes extending across said interconnect paths of said intermediate portion of said flexible substrate, said rigidizer plate being bent along said axes such that said first and second rigidizer plate end portions are substantially parallel to each other while being located in different planes.

17. Flexible circuit board assembly according to claim 16 wherein said bend axes are substantially parallel to said stiff paths.

18. Flexible circuit board assembly according to claim 17 wherein said rigidizer plate has a pair of channels former therein, each channel corresponding to one of said bend axes.

19. A method for providing a flexible circuit board assembly comprising the steps of:

providing a flexible substrate of electrically insulating material having a predetermined thickness and a top surface extending between first and second end portions of said flexible substrate with an intermediate portion of said flexible substrate located therebetween;

providing a plurality of conductive metalization interconnect paths, fixed to said flexible substrate, each of said interconnect paths extending from at least said substrate first end portion, across said substrate intermediate portion, to said substrate second end portion;

providing first and second end portions of a rigidizer plate;

mounting said first and second substrate end portions to said first and second end portions of said rigidizer plate, respectively, with said substrate intermediate portion comprising an unmounted portion of said flexible substrate between said first and second end portions of said rigidizer plate; and

selectively providing stiffening material on said substrate intermediate portion to define varying areas of stiffness for the flexible substrate intermediate portion which varying areas of stiffness define at least 2 stiff paths for the flexible substrate intermediate portion, with a less stiff path for the flexible substrate intermediate portion between the stiff paths, said stiff and less stiff paths extending across the flexible substrate intermediate portion and across the conductive metalization interconnect paths, said stiff and less stiff paths defining desired bend curvature characteristics for the flexible substrate intermediate portion.

20. A method according to claim 19 which includes the step of bending said rigidizer plate along at least one bend axis which extends across said interconnect paths of said intermediate portion of said flexible substrate such that said first and second rigidizer plate end portions are non coplanar, said first and second rigidizer plate end portions being coplanar prior to said bending step.

21. A method according to claim 20 wherein said mounting step comprises bonding said first and second rigidizer plate end portions to said first and second substrate end portions, respectively, by bonding material positioned therebetween, with said substrate intermediate portion comprising an unbonded portion of said flexible substrate between said first and second rigidizer plate portions.

22. A method according to claim 21 wherein said step of providing stiffening material comprises the step of adding metalization areas on said intermediate substrate portion.

23. A method according to claim 22 wherein said added metalization areas are separate from said conductive metalization interconnect paths.

24. A method according to claim 22 wherein said added metalization areas are extensions of and are connected to said conductive metalization interconnection paths.

25. A method according to claim 20 wherein said bending step comprises bending said rigidizer plate along two axes extending across said interconnect paths of said intermediate portion of said flexible substrate, said rigidizer plate being bent along said axes such that said first and second rigidizer end portions are substantially parallel to each other while being located in different planes.

26. A method according to claim 25 wherein said bend axes are substantially parallel to said stiff paths.

27. A method according to claim 26 wherein said step of providing said rigidizer plate comprises forming said rigidizer plate with a pair of channels therein, each channel corresponding to one of said bend axes.