Solid electrolytic capacitor with high temperature leakage stability
A solid electrolytic capacitor and method for forming a solid electrolytic capacitor with high temperature leakage stability is described. The solid electrolytic capacitor has improved leakage current and is especially well suited for high temperature environments such as down-hole applications.
1. A method for forming a solid electrolytic capacitor comprising:
providing an anode;
forming a dielectric layer on said anode;
applying a cathode layer on said dielectric layer;
applying a transition layer on said cathode layer wherein said transition layer comprises a blocking layer wherein said blocking layer is hydrophobic and insulative;
plating a metal layer on said transition layer; and
electrically connecting a cathode termination to said cathode layer;
wherein said solid electrolytic capacitor has a leakage shift of no more than 50% after 500 hrs at 200° C. relative to the leakage after 500 hours at ambient temperature.
2. The method for forming a solid electrolytic capacitor of claim 1 wherein said solid electrolytic capacitor has a leakage shift of no more than 50% after 500hrs at 220° C. relative to the leakage after 500 hours at ambient temperature.
3. The method for forming a solid electrolytic capacitor of claim 1 wherein the median leakage shift at 200° C. for 500 hrs is less than 20% relative to the leakage after 500 hours at ambient temperature.
4. The method for forming a solid electrolytic capacitor of claim 1 wherein said solid electrolytic capacitor has a leakage of no more than 0.10 CV after 500 hrs at a temperature of at least 200° C.
5. The method for forming a solid electrolytic capacitor of claim 1 wherein said capacitor has a leakage of no more than 0.10 CV after 500 hrs at temperature greater than 220° C.
6. The method for forming a solid electrolytic capacitor of claim 1 wherein said metal layer does not contain silver or sulfur.
7. The method for forming a solid electrolytic capacitor of claim 1 wherein said plating a metal layer comprises plating a layer comprising nickel.
8. The method for forming a solid electrolytic capacitor of claim 7 wherein said plating a metal layer comprises plating a layer consisting essentially of nickel.
9. The method for forming a solid electrolytic capacitor of claim 1 wherein said cathode layer is MnO 2 .
10. The method for forming a solid electrolytic capacitor of claim 1 wherein said cathode layer has a thermal decomposition temperature of greater than 350° C.
11. The method for forming a solid electrolytic capacitor of claim 10 wherein said thermal decomposition temperature is greater than 500° C.
12. The method for forming a solid electrolytic capacitor of claim 1 wherein said capacitor is encapsulated.
13. The method for forming a solid electrolytic capacitor of claim 12 wherein said capacitor is encapsulated in a material selected from polymer, metal and ceramic.
14. The method for forming a solid electrolytic capacitor of claim 12 wherein said capacitor is encapsulated in a hermetic seal.
15. The method for forming a solid electrolytic capacitor of claim 12 wherein said capacitor is encapsulated in a material which does not form a hermetic seal.
16. The method for forming a solid electrolytic capacitor of claim 1 wherein said blocking layer has a thickness of less than 2 microns.
17. The method for forming a capacitor of claim 1 wherein said plating a metal layer is done by electroplating.