Flex Circuit with Single Sided Routing and Double Sided Attach

• US 20090283300A1
• Filed: 05/16/2008
• Published: 11/19/2009
• Est. Priority Date: 05/16/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: GRUNTHANER, Martin Paul
• Granted Patent: US 8,456,851 B2
• Time in Patent Office: Days
• US Class Current: 174/254
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: H05K 1/118 specially for flexible printed circuits, e.g. using folded portions
• CPC Class Codes: H05K 1/147 at least one of the printed circuits being bent or folded, e.g. by using a flexible printed circuit H05K1/148 takes precedence
• CPC Class Codes: H05K 2201/053 Tails
• 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 2203/1572 Processing both sides of a PCB by the same process; Providing a similar arrangement of components on both sides; Making interlayer connections from two sides
• CPC Class Codes: H05K 3/323 by applying an anisotropic conductive adhesive layer over an array of pads
• CPC Class Codes: H05K 3/361 Assembling flexible printed circuits with other printed circuits
• CPC Class Codes: Y10T 156/10 Methods of surface bonding and/or assembly therefor
• CPC Class Codes: Y10T 156/1052 with cutting, punching, tearing or severing
• CPC Class Codes: Y10T 29/49124 On flat or curved insulated base, e.g., printed circuit, etc.
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base

Abstract

A flex circuit having conductive traces formed on only one side of a base film for attaching to both sides of a DITO touch sensor panel is disclosed. By having conductive traces formed on only one side of the base film, the number of process steps and fabrication cost can be reduced because only a single etching step is needed. Furthermore, because the flex circuit is thinner, the resultant space savings can be utilized for other features in a device without enlarging the overall device package.

Claims

1. A flex circuit for connecting to both sides of a touch sensor panel, comprising:

a base film shaped to form first and second attachment areas;

a layer of conductive traces formed on a single surface of the base film and terminating with conductors in the first and second attachment areas, the conductors shaped and located for making electrical connections with first and second sides of the touch sensor panel; and

an insulator formed over the conductive traces and conductors;

wherein the base film, conductive traces and insulator form a flexible stackup capable of being folded for attachment to the top and bottom sides of the touch sensor panel.

2. The flex circuit of claim 1, further comprising active and dummy conductors on the first attachment area and lower conductors on the second attachment area, the lower conductors arranged in conjunction with the active and dummy conductors so that when the flex circuit is folded and attached to the touch sensor panel, the lower conductors and the active and dummy conductors are not on directly opposing sides of the touch sensor panel.

3. The flex circuit of claim 1, further comprising a tail integrally formed with the flex circuit, the tail containing tail conductors for connecting to a logic board.

4. The flex circuit of claim 1, further comprising active and dummy conductors on the first attachment area, one or more dummy conductors placed between each active conductor, the active and dummy conductors spaced to substantially contain conductive bonding material used to bond the first attachment area to the touch sensor panel.

5. The flex circuit of claim 1, further comprising:

lower conductors on the second attachment area, the insulator configured for exposing the lower conductors at each distal end of the second attachment area; and

a stiffener formed at each distal end of the second attachment area, the stiffeners and the exposed lower conductors located on directly opposing sides of the distal ends of the second attachment area.

6. The flex circuit of claim 1, further comprising a top conductive film formed on a top side of the flex circuit and connected to one or more conductive traces for holding the top conductive film at a fixed potential.

7. The flex circuit of claim 6, further comprising a first opening formed in the insulator for providing a connection from the top conductive film to the one or more conductive traces.

8. The flex circuit of claim 7, further comprising a bottom conductive film formed on a bottom side of the flex circuit and connected to one or more conductive traces for holding the bottom conductive film at a fixed potential.

9. The flex circuit of claim 8, further comprising a second opening formed in the base film and the insulator for providing a connection from the bottom conductive film to the top conductive film.

10. The flex circuit of claim 9, wherein either or both of the first and second openings are notches.

11. The flex circuit of claim 6, further comprising a bottom conductive film formed on a bottom side of the flex circuit, the top and bottom conductive films overhanging the flex circuit and conductively bonded in an overhanging area.

12. The flex circuit of claim 1, the flex circuit incorporated within a computing system and connected between the touch sensor panel and a panel subsystem.

13. A method for providing electrical connections to both sides of a touch sensor panel, comprising:

forming conductive traces on a single surface of a base film; and

shaping the base film to form first and second attachment areas capable of aligning with pads on first and second sides of the touch sensor panel when the base film and conductive traces are folded.

14. The method of claim 13, further comprising forming an insulator over the conductive traces.

15. The method of claim 13, further comprising forming active and dummy conductors on the first attachment area and lower conductors on the second attachment area, the lower conductors arranged in conjunction with the active and dummy conductors so that when the flex circuit is folded and attached to the touch sensor panel, the lower conductors and the active and dummy conductors are not on directly opposing sides of the touch sensor panel.

16. The method of claim 13, further comprising integrally forming a tail with the flex circuit, the tail containing tail conductors for connecting to a logic board.

17. The method of claim 13, further comprising:

forming active and dummy conductors on the first attachment area, with one or more dummy conductors placed between each active conductor; and

spacing the active and dummy conductors to substantially contain conductive bonding material used to bond the first attachment area to the touch sensor panel.

18. The method of claim 14, further comprising:

forming lower conductors on the second attachment area;

limiting the insulator to expose the lower conductors at each distal end of the second attachment area; and

adding a stiffener at each distal end of the second attachment area, the stiffeners and the exposed lower conductors located on directly opposing sides of the distal ends of the second attachment area.

19. The method of claim 14, further comprising:

forming a top conductive film on a top side of the flex circuit; and

connecting the top conductive film to one or more conductive traces for holding the top conductive film at a fixed potential.

20. The method of claim 19, further comprising forming a first opening in the insulator for providing a connection from the top conductive film to the one or more conductive traces.

21. The method of claim 20, further comprising:

forming a bottom conductive film on a bottom side of the flex circuit; and

connecting the bottom conductive film to one or more conductive traces for holding the bottom conductive film at a fixed potential.

22. The method of claim 21, further comprising forming a second opening in the base film and the insulator for providing a connection from the bottom conductive film to the top conductive film.

23. The method of claim 22, wherein either or both of the first and second openings are notches.

24. The method of claim 20, further comprising:

forming a bottom conductive film on a bottom side of the flex circuit;

overhanging the top and bottom conductive films beyond the flex circuit; and

conductively bonding the top and bottom conductive films in the overhanging area.

25. A mobile telephone containing a flex circuit connecting a touch sensor panel and a panel subsystem, the flex circuit for connecting to both sides of the touch sensor panel, the flex circuit comprising:

a base film shaped to form first and second attachment areas;

a layer of conductive traces formed on a single surface of the base film and terminating with conductors in the first and second attachment areas, the conductors shaped and located for making electrical connections with first and second sides of the touch sensor panel; and

an insulator formed over the conductive traces and conductors;

wherein the base film, conductive traces and insulator form a flexible stackup capable of being folded for attachment to the top and bottom sides of the touch sensor panel.

26. A media player containing a flex circuit connecting a touch sensor panel and a panel subsystem, the flex circuit for connecting to both sides of the touch sensor panel, the flex circuit comprising:

a base film shaped to form first and second attachment areas;

a layer of conductive traces formed on a single surface of the base film and terminating with conductors in the first and second attachment areas, the conductors shaped and located for making electrical connections with first and second sides of the touch sensor panel; and

an insulator formed over the conductive traces and conductors;

wherein the base film, conductive traces and insulator form a flexible stackup capable of being folded for attachment to the top and bottom sides of the touch sensor panel.