Metal injection molded titanium alloy housing for implantable medical devices

• US 20080269829A1
• Filed: 04/26/2007
• Published: 10/30/2008
• Est. Priority Date: 04/26/2007
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Kast, John E., Robinson, Reginald D., Li, Bernard
• Granted Patent: US 7,801,613 B2
• Time in Patent Office: Days
• US Class Current: 607/36
• CPC Class Codes: A61L 27/06 Titanium or titanium alloys
• CPC Class Codes: A61N 1/375 Constructional arrangements, e.g. casings
• CPC Class Codes: A61N 1/37512 Pacemakers
• CPC Class Codes: B22F 2003/244 Leaching
• CPC Class Codes: B22F 2998/10 Processes characterised by the sequence of their steps
• CPC Class Codes: B22F 3/1021 Removal of binder or filler removal of binder from ceramics C04B35/638
• CPC Class Codes: B22F 3/15 Hot isostatic pressing
• CPC Class Codes: B22F 3/225 by injection molding
• CPC Class Codes: B22F 3/24 After-treatment of workpieces or articles B22F3/1146 takes precedence
• CPC Class Codes: B22F 7/062 involving the connection or repairing of preformed parts
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

The housing of an implantable medical device is made of a titanium alloy that provides improved electrical performance, mechanical strength, and reduced MRI heating. The titanium alloy housing includes portions formed by metal injection molding and welded together. Wall thickness of at least a portion of one major face of the housing is reduced by chemical etching a metal injected molded housing portion.

Claims

1. A housing of an implantable medical device, the housing comprising:

a first housing portion of a titanium alloy having a resistivity of greater than about 100 μ

Ohm-cm formed by metal injection molding; and

a second housing portion joined to the first housing portion, the second housing portion being of the titanium alloy and formed by metal injection molding.

2. The housing of claim 1, wherein at least one of the housing portions has a region of reduced wall thickness formed by a chemical removal process.

3. The housing of claim 1, wherein the first housing portion includes a region having a wall thickness of less than about 0.015 inches.

4. The housing of claim 3, wherein the second housing portion includes a region having a wall thickness of less than about 0.015 inches.

5. The housing of claim 4, wherein the first housing portion includes a first rim and the second housing portion includes a second rim, and wherein the first and second rims are welded together.

6. The housing of claim 5, wherein the first and second rims have a wall thickness of greater than about 0.015 inches.

7. The housing of claim 1, wherein the titanium alloy includes at least one of aluminum, vanadium and molybdenum.

8. The housing of claim 7, wherein the titanium alloy includes titanium, aluminum and vanadium.

9. The housing of claim 1, wherein the titanium alloy comprises a one of:

a Ti6Al4V alloy, a Ti8AlMo—

IV alloy, a Ti6242 alloy, an SP-700 alloy, a Ti5Al2.5Sn alloy, and a Ti3Al2V alloy.

10. The housing of claim 1, wherein the titanium alloy includes ceramic particles.

11. The housing of claim 10, wherein the ceramic particles include at least one of titanium carbide, titanium dioxide and silicon carbide.

12. The housing of claim 1, wherein the titanium alloy has a tensile yield of strength of greater than about 500 Mpa.

13. The housing of claim 1, wherein the titanium alloy comprises an α

Ti or near α

Ti alloy.

14. The housing of claim 1, wherein the titanium alloy has a resistivity of about 100 μ

Ohm-cm to about 220 μ

Ohm-cm.

15. The housing of claim 14, wherein the titanium alloy has a resistivity of about 125 μ

Ohm-cm to about 190 μ

Ohm-cm.

16. A method for forming the housing of an implantable medical device, the method comprising:

forming a first housing portion by metal injection molding a titanium alloy;

selectively reducing the wall thickness of at least one region of the first housing portion;

forming a second housing portion by metal injection molding the titanium alloy; and

joining the first housing portion and the second housing portion by welding to produce the housing of the implantable medical device.

17. The method of claim 16, wherein forming the first housing portion comprises:

injecting a mixture of metal alloy constituent particles and a polymer into a mold to form the first housing portion;

heating the first housing portion to remove the polymer; and

sintering the first housing portion.

18. The method of claim 17, wherein the metal alloy constituent particles include titanium and at least one of aluminum, vanadium, and molybdenum.

19. The method of claim 17, wherein the mixture further includes ceramic particles.

20. The method of claim 16, wherein selectively reducing the wall thickness is by chemical removal.

21. An implantable medical device comprising:

a housing of a titanium alloy having a resistivity of greater than about 100 μ

Ohm-cm formed by metal injection molding;

a rechargeable power source within the housing; and

electronic circuitry within the housing and powered by the rechargeable power source.

22. The implantable medical device of claim 21, wherein the housing has a first face with a wall thickness of less than about 0.015 inches.

23. The implantable medical device of claim 22, wherein the first face has a wall thickness of about 0.008 to about 0.012 inches.

25. The implantable medical device of claim 21, and further comprising:

a coil for receiving electromagnetic energy to charge the rechargeable power source, the coil positioned within the housing adjacent the first face.

26. The implantable medical device of claim 21, wherein the housing is formed by metal injection molding.

27. The implantable medical device of claim 21, wherein the titanium alloy includes at least one of aluminum, vanadium and molybdenum.

28. The implantable medical device of claim 27, wherein the titanium alloy includes titanium, aluminum and vanadium.

29. The implantable medical device of claim 21, wherein the titanium alloy comprises a one of:

a Ti6Al4V alloy, a Ti8AlMo—

IV alloy, a Ti6242 alloy, an SP-700 alloy, a Ti5Al2.5Sn alloy, and a Ti3Al2V alloy.

30. The implantable medical device of claim 21, wherein the titanium alloy includes ceramic particles.

31. The implantable medical device of claim 30, wherein the ceramic particles include at least one of titanium carbide, titanium dioxide and silicon carbide.

32. The implantable medical device of claim 21, wherein the titanium alloy has a tensile yield strength of greater than about 500 Mpa.

33. The implantable medical device of claim 21, wherein the titanium alloy comprises an α

Ti or near α

Ti alloy.

34. The implantable medical device of claim 21, wherein the titanium alloy has a resistivity of about 100 μ

Ohm-cm to about 220 μ

Ohm-cm.

35. The implantable medical device of claim 34, wherein the titanium alloy has a resistivity of about 125 μ

Ohm-cm to about 190 μ

Ohm-cm.

24. The implantable medical device wherein the first face wall thickness is formed by a chemical removal process.