Solid electrolytic capacitor containing a sequential vapor-deposited interior conductive polymer film
A capacitor comprising a solid electrolytic capacitor element that a sintered porous anode body, a dielectric that overlies the anode body, and a solid electrolyte is provided. The solid electrolyte contains an interior conductive polymer film that overlies the dielectric, which may be formed by sequential vapor deposition. An exterior conductive polymer layer also overlies the interior conductive polymer film.
1. A method for forming a solid electrolytic capacitor element, the method comprising:
positioning a capacitor element with a reactor vessel, wherein the capacitor element comprises a sintered porous anode body and a dielectric overlying the anode body;
forming a film on the capacitor element by a sequential vapor deposition process, the process including subjecting the capacitor element to a reaction cycle that includes contacting the capacitor element with a gaseous precursor compound that bonds to a surface of the capacitor element and thereafter contacting the capacitor element with a gaseous oxidizing agent to oxidize and/or polymerize the precursor compound; and
applying an exterior conductive polymer layer over the film.
2. The method of claim 1 , wherein the precursor compound is a pyrrole, aniline, or a thiophene compound.
3. The method of claim 1 , wherein the precursor compound is 3,4-ethylenedioxythiophene.
4. The method of claim 1 , wherein the oxidizing agent has a boiling temperature of about 320° C. or less.
5. The method of claim 1 , wherein the oxidizing agent is MoCl 5 .
6. The method of claim 1 , wherein the capacitor element is heated to a temperature of about 200° C. or less during the reaction cycle.
7. The method of claim 1 , further comprising contacting the capacitor element with an inert gas prior to contact with the oxidizing agent.
8. The method of claim 1 , further comprising subjecting the capacitor element to one or more additional reaction cycles that include contacting the capacitor element with a gaseous precursor compound and thereafter contacting the capacitor element with a gaseous oxidizing agent.
9. The method of claim 1 , wherein the film has a thickness of about 10 nanometers or more.
10. The method of claim 1 , wherein the film has an intrinsic conductivity of about 100 S/cm or more as determined at a temperature of about 25° C.
11. The method of claim 1 , wherein the capacitor element further comprises a pre-coat overlying the dielectric.
12. The method of claim 1 , wherein the exterior conductive polymer layer is formed from a dispersion of conductive polymer particles.
13. The method of claim 1 , wherein the exterior conductive polymer layer is formed by solution phase polymerization.
14. The method of claim 1 , wherein the anode body includes tantalum and the dielectric includes tantalum pentoxide.