Solid electrolytic capacitor having a high capacitance
A solid electrolytic capacitor that comprises an anode that comprises a porous anode body and a dielectric layer is provided. The anode body is formed from a pressed and sintered valve metal powder having a specific charge of about 200,000 μF*V/g or more and a phosphorous content of about 150 parts per million or less. A solid electrolyte overlies the anode.
1. A solid electrolytic capacitor comprising:
an anode that comprises a porous anode body and a dielectric layer, wherein the anode body is formed from a pressed and sintered valve metal powder having a specific charge of about 200,000 μF*V/g or more and a phosphorous content of about 100 parts per million or less, and wherein the powder contains primary particles having a nodular or angular shape; and
a solid electrolyte overlying the anode.
2. The solid electrolytic capacitor of claim 1 , wherein the valve metal powder includes tantalum.
3. The solid electrolytic capacitor of claim 1 , wherein the powder is formed by reacting a tantalum salt with a reducing agent.
4. The solid electrolytic capacitor of claim 3 , wherein the reducing agent is hydrogen gas.
5. The solid electrolytic capacitor of claim 1 , wherein the powder is formed from agglomerated particles.
6. The solid electrolytic capacitor of claim 5 , wherein the powder is formed from primary particles having a median size of from about 5 to about 250 nanometers.
7. The solid electrolytic capacitor of claim 1 , wherein an anode lead is be connected to the anode body.
8. The solid electrolytic capacitor of claim 1 , further comprising:
an anode termination that is in electrical connection with the anode lead;
a cathode termination that is in electrical connection with the solid electrolyte; and
a casing that encapsulates the capacitor anode and the solid electrolyte and leaves exposed at least a portion of the anode termination and the cathode termination.
9. The solid electrolytic capacitor of claim 1 , wherein the solid electrolyte includes a conductive polymer.
10. The solid electrolytic capacitor of claim 9 , wherein the conductive polymer is poly(3,4-ethylenedioxythiophene) or a derivative thereof.
11. The solid electrolytic capacitor of claim 1 , wherein the solid electrolyte includes manganese dioxide.
12. The solid electrolytic capacitor of claim 1 , wherein the capacitor exhibits a wet-to-dry capacitance percentage of about 75% or more, as determined at a frequency of 120 Hz.
13. The solid electrolytic capacitor of claim 1 , wherein the capacitor exhibits an ESR of from about 0.05 to about 2.0 ohms, as determined at a frequency of 100 kHz.
14. The solid electrolytic capacitor of claim 1 , wherein the capacitor exhibits a leakage current of about 75 microamps or less, as determined at a voltage of 6.3 V per 60 seconds.
15. The solid electrolytic capacitor of claim 1 , wherein the capacitor exhibits a dissipation factor of about 65% or less, as determined at a frequency of 120 Hz.
16. The solid electrolytic capacitor of claim 1 , wherein the powder has a phosphorous content of about 50 parts per million or less.
17. A method of forming a solid electrolytic capacitor, the method comprising:
pressing a valve metal powder into an anode body, wherein the powder has a specific charge of about 200,000 μF*V/g or more and a phosphorous content of about 100 parts per million or less, and wherein the powder contains primary particles having a nodular or angular shape;
sintering the anode body;
forming a dielectric layer over the sintered anode body; and
applying a solid electrolyte over the dielectric layer.
18. The method of claim 17 , wherein the valve metal powder includes tantalum.
19. The method of claim 17 , wherein the powder is formed by reacting a tantalum salt with a reducing agent.
20. The method of claim 19 , wherein the reducing agent is hydrogen gas.
21. The method of claim 17 , wherein the powder is agglomerated at a temperature of from about 0° C. to about 40° C. in the presence of a binder.
22. The method of claim 17 , wherein the powder is formed from primary particles having a median size of from about 5 to about 250 nanometers.
23. The method of claim 17 , wherein the solid electrolyte includes a conductive polymer.
24. The method of claim 23 , wherein the conductive polymer is poly(3,4-ethylenedioxythiophene) or a derivative thereof.
25. The method of claim 17 , wherein the solid electrolyte includes manganese dioxide.