Method for Providing Hermetic Electrical Feedthrough

• US 20190313537A1
• Filed: 06/24/2019
• Published: 10/10/2019
• Est. Priority Date: 05/28/2008
• Status: Active Grant

• Current Assignee: Cortigent Incorporated
• Original Assignee: Second Sight Medical Products, Inc.
• Inventors: Ok, Jerry, Jiang, Honggang
• Granted Patent: US 10,952,332 B2
• Time in Patent Office: Days
• CPC Class Codes: B29K 2995/0056 Biocompatible, e.g. biopolymers or bioelastomers
• CPC Class Codes: B32B 2038/0016 Abrading
• CPC Class Codes: B32B 2038/047 Perforating
• CPC Class Codes: B32B 2307/202 Conductive
• CPC Class Codes: B32B 2309/60 In a particular environment
• CPC Class Codes: B32B 2309/66 Fluid other than air
• CPC Class Codes: B32B 2309/68 Vacuum
• CPC Class Codes: B32B 2310/0843 using laser
• CPC Class Codes: B32B 2315/02 Ceramics
• CPC Class Codes: B32B 2535/00 Medical equipment, e.g. bandage, prostheses, catheter medical patches B32B2556/00
• CPC Class Codes: B32B 37/02 characterised by a sequence of laminating steps, e.g. by adding new layers at consecutive laminating stations
• CPC Class Codes: B32B 37/14 characterised by the properties of the layers
• CPC Class Codes: B32B 37/144 using layers with different mechanical or chemical conditions or properties, e.g. layers with different thermal shrinkage, layers under tension during bonding constructional features for tensioning B32B38/1825
• CPC Class Codes: B32B 37/24 with at least one layer not being coherent before laminating, e.g. made up from granular material sprinkled onto a substrate B32B37/15 takes precedence
• CPC Class Codes: B32B 38/10 Removing layers, or parts of layers, mechanically or chemically
• CPC Class Codes: H05K 1/0306 Inorganic insulating substrates, e.g. ceramic, glass
• CPC Class Codes: H05K 2203/1147 Sealing or impregnating, e.g. of pores
• CPC Class Codes: H05K 2203/308 Sacrificial means, e.g. for temporarily filling a space for making a via or a cavity or for making rigid-flexible PCBs
• CPC Class Codes: H05K 3/1233 Methods or means for supplying the conductive material and for forcing it through the screen or stencil
• CPC Class Codes: H05K 3/4061 for via connections in inorganic insulating substrates
• CPC Class Codes: H05K 3/4614 : the electrical connections between the circuit boards being made during lamination
• CPC Class Codes: H05K 3/4623 : the circuit boards having internal via connections between two or more circuit layers before lamination, e.g. double-sided circuit boards H05K3/462 takes precedence
• CPC Class Codes: H05K 3/4629 : laminating inorganic sheets comprising printed circuits, e.g. green ceramic sheets
• CPC Class Codes: Y10T 156/10 : Methods of surface bonding and/or assembly therefor

Abstract

This invention provides methods for the processing of platinum metallized high temperature co-fired ceramic (HTCC) components with minimum deleterious reactions between platinum and the glass constituents of the ceramic-glass body. The process comprises co-firing a multilayer laminate green ceramic-glass body with via structures filled with a platinum powder-based material in a reducing atmosphere with a specified level of oxygen partial pressure. The oxygen partial pressure should be maintained above a minimum threshold value for a given temperature level.

Claims

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

providing a ceramic sheet, and having an upper surface and a lower surface, wherein said sheet includes silicon dioxide;

forming at least one via hole in said sheet extending from said upper surface to said lower surface;

inserting a conductive thickfilm paste, including platinum, into said via hole;

laminating said sheet with said conductive thick film paste in said via hole between an upper ceramic sheet, and a lower ceramic sheet, to form a laminated substrate wherein said via hole is encased in ceramic;

selecting an oxygen controlled environment, between 10<sup>−

38</sup> and 10<sup>−

3</sup> atmospheres of oxygen partial pressure, by introduction of other gasses selected from the group consisting of C0₂/CO, C0₂/NH₃, C0₂/H₂, H₂0/H₂, H₂0/NH₃, H₂0/CO, Nitrogen, or Argon, to balance platinum oxidation and silicon dioxide decomposition of said laminated substrate;

firing said laminated substrate in said oxygen controlled environment to a temperature to sinter said laminated substrate to form a single sintered structure and cause said conductive thick film paste in said via hole to form a metallized via, including platinum in contact with ceramic, and cause said laminated substrate to form a fired laminated substrate and a hermetic seal around said metallized via; and

removing said upper sheet material and said lower sheet material by lapping or grinding, to expose an upper and a lower surface of said metallized via.

2. The method according to claim 1, wherein said sheet is formed of material comprised of at least 90% aluminum oxide.

3. The method according to claim 1, wherein said fired laminated substrate after said firing and material removal steps is less than or equal to 40 mils thick.

4. The method according to claim 1, wherein said fired laminated substrate after said firing and material removal steps is less than 15 mils thick.

5. The method according to claim 1, wherein forming at least one via hole in said sheet comprises punching said via hole using a punch tool, etching said via hole using a solvent etching, using laser ablation or drilling said via hole.

6. The method according to claim 1, wherein inserting a conductive material into said via hole comprises:

disposing said sheet with said via hole between a stencil layer and a vacuum base, wherein said stencil layer includes at least one through hole that is aligned above said via hole;

rolling said conductive material across said stencil layer; and

pulling said conductive material into said via hole through said hole in said stencil layer with a vacuum created by said vacuum base.

7. The method according to claim 1, further comprising laminating said sheet with paste filled via holes between said upper sheet and said lower sheet to form said laminated substrate;

placing said sheet with paste filled via holes together with said upper ceramic sheet and said lower ceramic sheet in a heatpress; and

applying heat and pressure by said heatpress until said laminated substrate is formed.

8. The method according to claim 1, wherein said ceramic material comprises aluminum oxide, zirconium oxide or a mixture thereof.

9. The method according to claim 1, wherein said fired laminated substrate has a thickness of less than 20 mils after removing said upper ceramic sheet and said lower ceramic sheet material.

10. The method according to claim 1, wherein said fired laminated substrate has a thickness of 15-20 mils after removing said upper ceramic sheet and said lower ceramic sheet material.