Biocompatible bonding method suitable for implantation
The invention is directed to a method of bonding a hermetically sealed electronics package to an electrode or a flexible circuit and the resulting electronics package, that is suitable for implantation in living tissue, such as for a retinal or cortical electrode array to enable restoration of sight to certain non-sighted individuals. The hermetically sealed electronics package is directly bonded to the flex circuit or electrode by electroplating a biocompatible material, such as platinum or gold, effectively forming a plated rivet-shaped connection, which bonds the flex circuit to the electronics package. The resulting electronic device is biocompatible and is suitable for long-term implantation in living tissue.
1. A method of making an implantable device comprising:
forming a substrate including an electrically non-conductive body and electrically conductive feedthroughs through the electrically non-conductive body;
forming first bond pads on a first side of the substrate electrically connected to the feedthroughs;
attaching electronics to a second side of the of the substrate and electrically connecting the electronics to the feedthroughs;
attaching a cover to the second side of the substrate forming a hermetic package enclosing the electronics;
forming a flexible circuit having a first polymer layer, conductive traces on the first polymer layer, and a second polymer layer on the conductive traces, the first polymer layer defining voids connecting second bond pads to the conductive traces; and
aligning the first bond pads with the second bond pads and bonding the flexible circuit to the substrate.
2. The method according to claim 1 , wherein bonding the flexible circuit to the substrate includes applying conductive adhesive between the first bond pads and the second bond pads.
3. The method according to claim 1 , wherein bonding the flexible circuit to the substrate includes:
studbumping the first bond pads with biocompatible materials;
studbumping the second bond pads with biocompatible materials; and
bonding the studbumps together by a thermomechanical process.
4. The method according to claim 3 , wherein the biocompatible materials comprise platinum.
5. The method according to claim 1 , wherein the first or second bond pads comprise platinum.
6. The method according to claim 1 , wherein the bond pads comprise platinum, iridium, titanium, platinum alloys, iridium alloys, or titanium alloys.
7. The method according to claim 1 , wherein the flexible circuit comprises polyimide.
8. The method according to claim 1 , wherein the substrate comprises biocompatible ceramic.
9. The method according to claim 8 , wherein the biocompatible ceramic comprises alumina.
10. The method according to claim 1 , wherein the substrate is rigid.
11. The method according to claim 1 , further comprising forming openings in at least one of the first polymer layer or the second polymer layer remote to the substrate.
12. The method according to claim 11 , further comprising forming electrodes in the openings.
13. The method according to claim 11 , wherein the step of forming openings is by laser cutting.
14. The method according to claim 11 , wherein the step of forming openings is by plasma etching.
15. The method according to claim 1 , wherein the electronics comprises an integrated circuit.
16. The method according to claim 1 , wherein the step of attaching electronics is by flip chip attach.
17. The method according to claim 1 , wherein the electronics comprises a\ hybrid circuit.