Insulator for a feedthrough
A hermetic feedthrough for an implantable medical device includes an insulator, a conduit configured to conduct electricity through the insulator, and a ferrule coupled to the insulator. The insulator is formed from a ceramic material and the conduit and insulator have a co-fired bond therebetween, which hermetically seals the conduit with the insulator. The insulator is elongate and has opposing ends that include flat surfaces and the ferrule includes a frame for receiving the insulator.
1. A hermetic feedthrough for an implantable medical device, comprising:
an insulator formed from a ceramic material; and
a conduit configured to conduct electricity through the insulator, wherein the conduit and insulator have a co-fired bond therebetween, and wherein the co-fired bond hermetically seals the conduit with the insulator; and
a ferrule coupled to the insulator;
wherein the ceramic material is elongate and has opposing ends that comprise flat surfaces, and the ceramic material includes three cross-sections that are orthogonal to each other and that each have a periphery with four straight edges, each of the straight edges being oriented perpendicular to two of the other straight edges and having rounded, unground corners therebetween;
wherein the ferrule includes an opening for receiving the ceramic material, and the ferrule does not include a flange extending inward into the opening for supporting the insulator, and wherein the rounded corners between any two straight edges are polished.
2. The feedthrough of claim 1 , wherein the ceramic material is a rectangular solid.
3. The feedthrough of claim 1 , wherein the ceramic material includes sides extending between the opposing ends, and wherein each of the sides comprises a flat surface.
4. The feedthrough of claim 1 , wherein the ceramic material further comprises sides extending between the opposing ends and rounded corners between the ends and sides, thereby reducing stresses associated with the corners.
5. The hermetic feedthrough of claim 1 , wherein the ceramic material has a top, a bottom, two sides extending lengthwise along the ceramic material, and two sides on the opposing ends of the ceramic material; and
wherein the conduit is configured to conduct electricity through the ceramic material between the top and bottom of the ceramic material.
6. The feedthrough of claim 5 , wherein the flat surfaces are substantially the same size and shape as one another.
7. The feedthrough of claim 6 , wherein the flat surfaces of the two sides on the ends of the ceramic material are parallel to one another.
8. The feedthrough of claim 7 , wherein the top and bottom of the ceramic material comprise flat surfaces orthogonal to the flat surfaces of the two sides on the ends of the ceramic material.
9. The feedthrough of claim 8 , wherein the two sides extending lengthwise along the ceramic material comprise flat surfaces orthogonal to the flat surfaces of the two sides on the ends of the ceramic material.
10. The feedthrough of claim 9 , wherein the insulator further comprises corners between the two sides extending lengthwise along the ceramic material and the two sides on the ends of the ceramic material, and wherein the corners are rounded.
11. The feedthrough of claim 5 , wherein the ceramic material of the insulator comprises alumina.
12. The feedthrough of claim 11 , wherein the ceramic material of the insulator mostly consists of alumina.
13. The feedthrough of claim 12 , wherein the conduit comprises platinum and an additive that comprises alumina.
14. The feedthrough of claim 13 , further comprising a pad overlaying the conduit and coupled to the top of the ceramic material, wherein the pad comprises a layer consisting essentially of platinum.
15. The feedthrough of claim 14 , wherein the pad has a co-fired bond with the insulator and the conduit.
16. The feedthrough of claim 1 , wherein the rounded corners between any two intersecting edges have a radius that is no greater than 20% of a minimum dimension of any of the three cross-sections.
17. A method of manufacturing a feedthrough, comprising:
co-firing a structure comprising:
a ceramic material that is an electrical insulator; and
a conduit configured to conduct electricity through the ceramic material;
cutting the structure to form the feedthrough, wherein after cutting, the ceramic material is elongate and has opposing ends that comprise flat surfaces, and the ceramic material includes three cross-sections that are orthogonal to each other and that each have a periphery with four straight edges, each of the straight edges being oriented perpendicular to two of the other straight edges and having corners therebetween;
rounding all corners of the straight edges of each periphery without grinding;
inserting the ceramic material into an opening of a ferrule, and wherein the step of rounding all corners includes polishing the corners.
18. The method of claim 17 , further comprising filling holes in sheets of the material, wherein the holes are filled with a conductive paste used to form the conduit.
19. The method of claim 18 , further comprising stacking the sheets such that the holes are substantially aligned with one another.
20. The method of claim 19 , wherein the sheets comprise alumina, wherein the conductive paste comprises platinum and an additive that comprises alumina.
21. The method of claim 20 , further comprising printing a pad overlaying the conduit, wherein a layer of the pad consists essentially of platinum.
22. The method of claim 17 , wherein polishing the corners includes tumbling the ceramic material in an abrasive agent.