High voltage and high efficiency polymer electrolytic capacitors
View Patent ↗A capacitor, and method of making a capacitor, is provided wherein the capacitor has exceptionally high break down voltage. The capacitor has a tantalum anode with an anode wire attached there to. A dielectric film is on the tantalum anode. A conductive polymer is on the dielectric film. An anode lead is in electrical contact with the anode wire. A cathode lead is in electrical contact with the conductive polymer and the capacitor has a break down voltage of at least 60 V.
1. A method for forming a capacitor comprising:
compressing tantalum powder into a tantalum anode wherein said tantalum anode comprises no more than 0.15 ppm/uC/g oxygen and no more than 50 ppm carbon;
anodizing said tantalum anode to form dielectric;
dipping said anodized anode into a slurry of conductive polymer;
drying said conductive polymer; and
providing a first external termination in electrical contact with said tantalum anode and a second external termination in electrical contact with said conductive polymer.
2. The method for forming a capacitor of claim 1 wherein said tantalum anode comprises no more than 0.1 ppm/uC/g oxygen.
3. The method for forming a capacitor of claim 1 wherein said tantalum anode comprises no more than 10 ppm carbon.
4. The method for forming a capacitor of claim 1 wherein said conductive polymer is selected from polyaniline, polypyrrole, polythiophene, and derivatives thereof.
5. The method for forming a capacitor of claim 4 wherein said conductive polymer is polyethyldioxythiophene.
6. The method for forming a capacitor of claim 1 wherein said slurry comprises polymeric particles with molecular weights of about 500 to about 10,000,000.
7. The method for forming a capacitor of claim 1 wherein said capacitor has a breakdown voltage of at least 60V.
8. The method for forming a capacitor of claim 7 wherein said capacitor has a breakdown voltage of at least 70V.
9. The method for forming a capacitor of claim 8 wherein said capacitor has a breakdown voltage of at least 100V.
10. The method for forming a capacitor of claim 9 wherein said capacitor has a breakdown voltage of at least 150V.
11. The method for forming a capacitor of claim 10 wherein said capacitor has a breakdown voltage of at least 200V.
12. The method for forming a capacitor of claim 1 wherein said capacitor has a ESR of no more than 150 mohms.
13. The method for forming a capacitor of claim 1 further comprising providing an anode wire in electrical contact with said anode.
14. The method for forming a capacitor of claim 13 wherein said anode wire is attached to said tantalum anode by welding in an inert atmosphere.
15. The method for forming a capacitor of claim 14 wherein said anode wire is tantalum.
16. The method for forming a capacitor of claim 1 further comprising applying a carbon layer between said conductive polymer and said second external termination.
17. The method for forming a capacitor of claim 1 further comprising applying a metallic coating between said carbon layer and said second external termination.
18. The method for forming a capacitor of claim 17 where the metallic coating comprises silver flake in an organic binder.
19. The method for forming a capacitor of claim 1 further comprising forming said dielectric to at least 100 V.
20. The method for forming a capacitor of claim 1 wherein said tantalum powder has a charge of no more than 30,000 CV/g.
21. The method for forming a capacitor of claim 1 further comprising at least partially encapsulating said capacitor in an organic molding.
22. The method for forming a capacitor of claim 1 further comprising hermetically sealing said capacitor in a metallic can.
23. The method for forming a capacitor of claim 22 wherein said second external termination is attached to said can.
24. The method for forming a capacitor of claim 1 wherein said dielectric is Ta 2 O 5 .
25. The method for forming a capacitor of claim 1 wherein said anode is sintered prior to said anodizing.