Implantable antenna assemblies

1. An implantable antenna assembly comprising:

a multilayer flexible printed circuit board comprising a first flexible substrate, second flexible substrate, and third flexible substrate;

an inductor comprising electrically conductive traces disposed on the first flexible substrate; and

a shield comprising electrically conductive traces disposed on the second flexible substrate and third flexible substrate, the shield surrounding the inductor.

2. The assembly of claim 1 , in which the electrically conductive traces comprise a noble metal disposed over a metal adhesion layer.

3. The assembly of claim 2 , in which the noble metal comprises at least one of: gold, a gold alloy, platinum, and a platinum alloy.

4. The assembly of claim 3 , in which the electrically conductive traces disposed on the first flexible substrate and electrically conductive traces disposed on the second and third flexible substrates comprise gold.

5. The assembly of claim 2 , in which the metallic adhesion layer comprises at least one of titanium and platinum.

6. The assembly of claim 1 , further comprising vias passing through the flexible substrates, the vias electrically connecting traces formed on different ones of the flexible substrates.

7. The assembly of claim 1 , in which the flexible substrates comprise an organic polymer.

8. The assembly of claim 7 , in which the flexible substrates comprise polyimide.

9. The assembly of claim 1 , further comprising an encapsulant, the encapsulant encapsulating the antenna assembly.

10. The assembly of claim 9 , in which the encapsulant comprises silicone.

11. The assembly of claim 9 , further comprising a pocket for retaining a magnet, the pocket formed in the encapsulant.

12. The assembly of claim 11 , further comprising an aperture in the flexible substrates, the aperture having a diameter larger than the magnet, in which the pocket is formed in the aperture such that the magnet, when placed in the pocket extends through the aperture.

13. The assembly of claim 1 , in which the shield extends around the inductor.

14. The assembly of claim 1 , further comprising adhesive disposed between the flexible substrates, the adhesive binding the flexible substrates together.

15. The assembly of claim 14 , in which the implantable antenna assembly before encapsulation has a thickness of less than 400 μm.

16. The assembly of claim 1 , in which the first flexible substrate is sandwiched between the second flexible substrate and third flexible substrate.

17. A cochlear implant comprising:

a processor;

an implantable antenna assembly electrically connected to the processor, the implantable antenna assembly comprising:

a multilayer flexible substrate; and

noble metal traces disposed on the multilayer flexible substrate; and

an encapsulant encapsulating the processor and implantable antenna assembly, wherein the encapsulant includes a pocket in which is removably contained a magnet, the magnet being removable from the implant without damage to the implant.

18. A method for forming an implantable antenna assembly comprises:

forming an inductor on a first flexible substrate;

forming a shield on at least one additional flexible substrate;

laminating the flexible substrates together;

forming vias between the substrates to complete electrical paths through the inductor and shield to form the antenna assembly;

attaching the antenna assembly to electronics;

encapsulating the antenna assembly; and

forming a pocket in an encapsulant when the antenna is encapsulated; and

placing a magnet in the pocket, wherein the magnet is removable from the pocket and replacable in the pocket without damage to the encapsulant.

19. The method of claim 18 , in which forming the inductor comprises:

forming an inductor coil on the first side of the first flexible substrate; and

forming a return trace on the second side of the first flexible substrate.

20. The method of claim 18 , in which forming shield comprises:

forming an upper portion of the shield on a second flexible substrate; and forming a lower portion of the shield on a third flexible substrate.

21. The method of claim 18 , in which forming the inductor and shield comprises:

depositing an adhesion metal on the substrates;

depositing a noble metal on the adhesion metal; and

etching away portions of the noble metal and adhesion metal to form traces of the inductor and shield.

22. The method of claim 18 , in which laminating the flexible substrates together comprises stacking the flexible substrates with the first flexible substrate sandwiched between the second and third flexible substrates.

23. The method of claim 22 , in which laminating the flexible substrates together further comprises:

depositing adhesive between the stacked flexible substrates; and

curing the adhesive.

24. The method of claim 23 , in which curing the adhesive comprises applying pressure and heat to the stacked flexible substrates.

25. The method of claim 18 , in which forming vias comprises:

forming holes through the flexible substrates; and

filling the holes with conductive material.

26. The method of claim 18 , in which encapsulating the antenna assembly comprises encapsulating the antenna assembly and electronics with silicone.

27. The method of claim 18 , further comprising forming an aperture in the antenna assembly with a diameter greater than the diameter of the magnet, in which the pocket is formed such that when a magnet placed in the pocket, at least a portion of the magnet is within the aperture.