Method and apparatus for providing hermetic electrical feedthrough

• US 7,480,988 B2
• Filed: 03/30/2001
• Issued: 01/27/2009
• Est. Priority Date: 03/30/2001
• Status: Expired due to Fees

• Current Assignee: Second Sight Medical Products, Inc.
• Original Assignee: Second Sight Medical Products, Inc.
• Inventors: Ok, Jerry, Greenberg, Robert J.
• Primary Examiner(s): Thai; Xuan M.
• Assistant Examiner(s): NGUYEN, BINH AN DUC
• Application Number:
  US09/823,464
• Publication Number:
  US 20020139556A1
• Time in Patent Office: 2,860 Days
• Field of Search: 174/50.61, 174/152.GM, 174/50.5, 174/50.51, 174/50.52, 174/52.3, 429/181, 298/45, 298/25, 298/29, 298/30, 298/31, 298/32, 298/34, 298/35, 298/37, 298/38, 298/42, 298/44, 298/46, 298/43, 298/48, 298/41, 298/50, 298/51, 298/52, 264/614, 264/618, 264/272.14, 156/89.11, 156/89.12, 156/89.16, 156/145, 156/150, 156/153
• US Class Current: 29/837
• CPC Class Codes: H01L 21/486 Via connections through the substrate with or without pins
• CPC Class Codes: H01L 23/10 characterised by the material or arrangement of seals between parts, e.g. between cap and base of the container or between leads and walls of the container
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H05K 1/0306 Inorganic insulating substrates, e.g. ceramic, glass
• CPC Class Codes: H05K 2201/10287 Metal wires as connectors or conductors
• CPC Class Codes: H05K 2201/10416 Metallic blocks or heatsinks completely inserted in a PCB metallic supports H05K3/0061
• CPC Class Codes: H05K 3/4046 using auxiliary conductive elements, e.g. metallic spheres, eyelets, pieces of wire
• CPC Class Codes: Y10T 29/49139 by inserting component lead or terminal into base aperture
• CPC Class Codes: Y10T 29/49146 with encapsulating, e.g., potting, etc.
• CPC Class Codes: Y10T 29/49147 Assembling terminal to base
• CPC Class Codes: Y10T 29/49162 by using wire as conductive path
• CPC Class Codes: Y10T 29/49163 with sintering of base
• CPC Class Codes: Y10T 428/24926 including ceramic, glass, porcelain or quartz layer

Abstract

A method and apparatus suitable for forming hermetic electrical feedthroughs in a ceramic sheet having a thickness of ≦40 mils. More particularly, the method yields an apparatus including a hermetic electrical feedthrough which is both biocompatible and electrochemically stable and suitable for implantation in a patient'"'"'s body. The method involves:

• • (a) providing an unfired, ceramic sheet having a thickness of ≦40 mils and preferably comprising >99% aluminum oxide;
  • (b) forming multiple blind holes in said sheet;
  • (c) inserting solid wires, preferably of platinum, in said holes;
  • (d) firing the assembly of sheet and wires to a temperature sufficient to sinter the sheet material but insufficient to melt the wires; and
  • (e) removing sufficient material from the sheet lower surface so that the lower ends of said wires are flush with the finished sheet lower surface.

Claims

1. A method of fabricating a hermetic electrical feedthrough comprising:

providing an unfired ceramic sheet having upper and lower surfaces;

forming an intermediate blind hole in said ceramic sheet extending from said upper surface toward said lower surface;

inserting a wire into said blind hole;

firing said sheet and wire to a temperature sufficient to sinter the sheet material and cause it to form a hermetic compression seal around said wire; and

removing sufficient sheet material from said sheet lower surface to expose said wire thus forming a through hole containing said wire.

2. The method of claim 1 wherein said ceramic sheet is formed of material comprised of at least 99% aluminum oxide.

3. The method of claim 1 wherein said ceramic sheet after said firing and material removal steps is less than 40 mils thick.

4. The method of claim 1 wherein said ceramic sheet after said firing and material removal steps is less than 15 mils thick.

5. The method of claim 1 wherein said wire is formed platinum.

6. The method of claim 1 wherein said wire has a diameter of less than 20 mils.

7. The method of claim 1 wherein said wire has a diameter of less than 10 mils.

8. A method of forming multiple hermetic electrical feedthroughs comprising the sequential steps of:

forming multiple intermediate blind holes in an unfired sheet of ceramic material, each hole extending from an upper sheet surface to a hole floor spaced from the lower surface of said sheet;

inserting a wire into each hole so that the lower end of each wire is supported on a hole floor;

firing said sheet and wires to sinter and shrink said ceramic material to form a hermetic compression seal around each wire; and

removing ceramic material from said sheet lower surface to said hole floors to expose the lower ends of said wires thus forming through holes containing said wires.

9. The method of claim 8 including a further step of lapping a sheet surface so that the ends of said wires are flush with the surface.

10. The method of claim 8 including a further step of dicing said sheet to form multiple dies each including multiple hermetic electrical feedthroughs.

11. The method of claim 8 wherein said ceramic material is from the group comprised of aluminum oxide and zirconia.

12. The method of claim 8 wherein said ceramic material comprises at least 99% aluminum oxide.

13. The method of claim 8 wherein each of said wires is formed of a material from the group including platinum, titanium, gold, palladum, tantalum, niobium.

14. The method of claim 8 wherein said wires are formed of substantially pure platinum.

15. The method of claim 8 wherein said sheet after lapping has a thickness of less than 15 mils.

16. The method of claim 8 wherein at least some of said wires have a diameter of less than 10 mils.

17. The method of claim 8 wherein said firing step includes subjecting said sheet to a temperature sufficient to sinter the ceramic material.

18. A method of fabricating a hermetic electrical feedthrough comprising:

providing an unsintered ceramic sheet having upper and lower surfaces;

forming one or more intermediate blind holes in said ceramic sheet extending from said upper surface toward said lower surface;

inserting a wire in each of said one or more blind holes;

firing said sheet and wire to a temperature sufficient to sinter the sheet material and cause it to form a hermetic compression seal around said wire; and

removing sufficient sheet material from said sheet lower surface to expose said wire thus forming a through hole containing said wire,

wherein said firing occurs by ramping up to a first temperature at a first heating rate;

then ramping up to a second temperature higher than the first temperature at a second heating rate different from the first heating rate.

19. The method of claim 18, wherein the first temperature is 600 C, the second temperature is 1600 C, the first heating rate is 1 C/minute and the second heating rate is 5 C/minute.

20. The method of claim 18, wherein said ramping up to a second temperature is followed by a dwell interval and a cool-to-room-temperature interval.

21. The method of claim 18, wherein said wire is a platinum wire.