Flexible circuit electrode array and method of manufacturing the same

• US 8,322,027 B1
• Filed: 10/29/2007
• Issued: 12/04/2012
• Est. Priority Date: 10/26/2005
• Status: Active Grant

• Current Assignee: Cortigent Incorporated
• Original Assignee: Second Sight Medical Products, Inc.
• Inventors: Greenberg, Robert J., Talbot, Neil Hamilton, Neysmith, Jordan Matthew, Ok, Jerry
• Primary Examiner(s): ANGWIN, DAVID PATRICK
• Application Number:
  US11/926,498
• Time in Patent Office: 1,863 Days
• Field of Search: 298/29, 298/25, 298/46, 298/47, 298/49, 174/254, 174/256, 439/67
• US Class Current: 29/829
• CPC Class Codes: A61N 1/0543 Retinal electrodes
• CPC Class Codes: H05K 1/0346 containing N
• 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 1/118 specially for flexible printed circuits, e.g. using folded portions
• CPC Class Codes: H05K 2201/0154 Polyimide
• CPC Class Codes: H05K 2201/0317 Thin film conductor layer; Thin film passive component
• CPC Class Codes: H05K 2203/0554 Metal used as mask for etching vias, e.g. by laser ablation
• CPC Class Codes: H05K 2203/0789 Aqueous acid solution, e.g. for cleaning or etching
• CPC Class Codes: H05K 2203/0793 Aqueous alkaline solution, e.g. for cleaning or etching
• CPC Class Codes: H05K 2203/095 Plasma, e.g. for treating a substrate to improve adhesion with a conductor or for cleaning holes
• CPC Class Codes: H05K 2203/1163 Chemical reaction, e.g. heating solder by exothermic reaction oxidising metal H05K2203/0315
• CPC Class Codes: H05K 3/0041 by plasma etching
• CPC Class Codes: H05K 3/06 the conductive material being removed chemically or electrolytically, e.g. by photo-etch process semi-additive methods H05K3/108
• CPC Class Codes: H05K 3/28 Applying non-metallic protective coatings H05K3/0091 takes precedence; methods for intermediate insulating layers for build-up multilayer circuits H05K3/4673
• CPC Class Codes: H05K 3/381 by special treatment of the substrate
• CPC Class Codes: H05K 3/388 by the use of a metallic or inorganic thin film adhesion layer
• CPC Class Codes: Y10T 29/49124 On flat or curved insulated base, e.g., printed circuit, etc.
• CPC Class Codes: Y10T 29/49147 Assembling terminal to base
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base

Abstract

A method for manufacturing a flexible circuit electrode array, comprising:

• a) depositing a metal trace layer containing a base coating layer, a conducting layer and a top coating layer on said insulator polymer base layer;
• b) applying a layer of photoresist on said metal trace layer and patterning said metal trace layer and forming metal traces on said insulator polymer base layer;
• c) activating said insulator polymer base layer and depositing a top insulator polymer layer and forming one single insulating polymer layer with said base insulator polymer layer;
• d) applying a thin metal layer and a layer of photoresist on the surface of said insulator polymer layer and selective etching said insulator layer and said top coating layer to obtain at least one via; and
• e) filling said via with electrode material.

A layer of polymer is laid down. A layer of metal is applied to the polymer and patterned to create electrodes and leads for those electrodes. A second layer of polymer is applied over the metal layer and patterned to leave openings for the electrodes, or openings are created later by means such as laser ablation. Hence the array and its supply cable are formed of a single body. Alternatively, multiple alternating layers of metal and polymer may be applied to obtain more metal traces within a given width.

The method provides an excellent adhesion between the polymer base layer and the polymer top layer and insulation of the trace metals and electrodes.

Claims

1. A method of making a flexible circuit comprising:

providing a partially cured flexible base polymer layer;

depositing metal comprising platinum on said partially cured base polymer layer forming bond pads at an end of said partially cured flexible base polymer layer, electrodes at an opposite end of said partially cured flexible base polymer layer and traces connecting said bond pads to said electrodes;

depositing a flexible top polymer precursor layer on said partially cured flexible base polymer and said metal; and

curing said base polymer layer and said top polymer layer

wherein said flexible circuit is biocompatible and suitable for implantation within a human body.

2. The method according to claim 1, wherein said step of providing a partially cured base polymer layer comprises:

depositing a base polymer layer; and

partially curing said base polymer layer.

3. The method according to claim 1, wherein said step of providing a partially cured base polymer layer comprises;

depositing a base polymer layer;

curing said base polymer layer; and

deimidizing at least a portion of said base polymer layer.

4. The method according to claim 1, wherein said polymer base layer and said polymer top layer are deposited by vapor deposition.

5. The method according to claim 1, wherein said polymer base layer and said polymer top layer are applied by spin-coating as polyamic acid solution and the polyimide layer is obtained by curing the polyamic acid solution.

6. The method according to claim 1, wherein depositing of said metal trace layer on said insulator polymer base layer is carried out by sputtering, magnetron sputtering, evaporation techniques or liftoff.

7. The method according to claim 1, wherein depositing of said metal trace layer on said insulator polymer base layer is carried out by magnetron sputtering of base titanium, platinum and top titanium.

8. The method according to claim 1, wherein said photoresist is a positive photoresist.

9. The method according to claim 8, wherein said photoresist layer is radiated with UV or laser light and areas of said layer which have been exposed to radiation are removed with a solvent.

10. The method according to claim 1, wherein said metal trace layer is patterned by photolithography and wet etching.

11. The method according to claim 1, wherein activating of said insulator polymer base layer is carried out by etching the surface of said base polymer layer by RIE and deimidizing the surface of said base polymer layer.

12. The method according to claim 11, wherein deimidizing the surface of said base polymer layer is carried out by sequential treatments with KOH and HCl.

13. The method according to claim 1, wherein activating of said insulator polymer base layer is carried out by etching the surface of said base polymer layer by ME in a plasma containing 80% to 90% O₂ and 10% to 20% CF₄.

14. The method according to claim 1, wherein an aluminum containing thin layer is deposited on said top insulator polymer layer and the photoresist layer is applied on said aluminum containing thin layer and radiated with UV or laser light and areas of said layer which have been exposed to radiation were removed with a solvent.

15. The method according to claim 12, wherein said aluminum containing thin layer is removed in areas of which have been exposed due to the selective removal of the photoresist.

16. The method according to claim 14, wherein said top insulator polymer layer is removed by ME in areas of which have been exposed due to the selective removal of the photoresist and the aluminum containing thin layer.

17. The method according to claim 1, wherein said top titanium layer is removed by wet etch in areas of which have been exposed due to the selective removal of the photoresist, the aluminum containing thin layer, and the polyimide.

18. The method according to claim 1, wherein said vias are filled with electrode material containing platinum.

19. The method according to claim 18, wherein said vias are electroplated with platinum.

20. The method according to claim 1, wherein said vias are electroplated with platinum having a fractal configuration.