Conductive polymer dispersions for solid electrolytic capacitors
View Patent ↗A capacitor with an anode and a dielectric over the anode. A first conductive polymer layer is over the dielectric wherein the first conductive polymer layer comprises a polyanion and a first binder. A second conductive polymer layer is over the first conductive polymer layer wherein the second conductive polymer layer comprises a polyanion and a second binder and wherein the first binder is more hydrophilic than the second binder.
1. A method for forming a capacitor comprising:
providing an anode with a dielectric coating thereon;
applying a first dispersion over said dielectric coating thereby forming a first conductive polymer layer over said dielectric coating,
wherein said first conductive polymer layer comprises a dopant and a hydrophilic material,
wherein said hydrophilic material is selected from the group consisting of poly(ethylene oxide), poly(vinyl alcohol), polyethylene oxide-polyvinyl alcohol-cellulose, polyvinylpyrrolidone, poly(hydroxyethyl methacrylate), polyurethane, poly(ethylene glycol), poly(propylene glycol), xanthan, methyl cellulose, starch, poly(acrylic acid), carboxymethyl cellulose, hydroxypropyl methyl cellulose, acrylic acid, methacrylic acid, chitosan, αβ-glycerophosphate, polyphosphazenes, polypeptides, poly(vinyl methyl ether), and poly(N-isopropyl acrylamide), and
wherein said hydrophilic material is crosslinked with a conductive polymer of said first conductive polymer layer; and
applying a second dispersion over said first conductive polymer layer thereby forming a second conductive polymer layer over said first conductive polymer layer.
2. The method for forming a capacitor of claim 1 wherein said second conductive polymer layer comprises a hydrophobic material.
3. The method for forming a capacitor of claim 2 wherein said hydrophobic material is selected from the group consisting of thermosetting materials, fluoro-polymers and their copolymers, silicone polymers and their copolymers, silicone polyester, crosslinkable polyester, and crosslinkable epoxies.
4. The method for forming a capacitor of claim 3 wherein said hydrophobic material is polytetrafluoroethylene.
5. The method for forming a capacitor of claim 1 wherein said first conductive polymer layer has a moisture content of at least 21 wt %.
6. The method for forming a capacitor of claim 1 wherein said second conductive polymer layer has a moisture content of no more than 15 wt % at 125° C.
7. The method for forming a capacitor of claim 1 wherein said first conductive polymer layer comprises at least one hydrophilic material is selected from the group consisting of poly(ethylene oxide), and poly(vinyl alcohol).
8. The method for forming a capacitor of claim 1 wherein said hydrophilic material is crosslinked with a crosslinking agent.
9. The method for forming a capacitor of claim 8 wherein said crosslinking agent comprises functional groups selected from hydroxyl and carboxyl.
10. The method for forming a capacitor of claim 1 wherein at least one of said first conductive polymer or said second conductive polymer comprises a moisture retaining component.
11. The method for forming a capacitor of claim 1 wherein at least one of said first conductive polymer layer or said second conductive polymer layer has a moisture loss of no more than 5 wt % upon heating from 125° C. to 175° C.
12. The method for forming a capacitor of claim 11 wherein said moisture loss is no more than 3 wt %.
13. The method for forming a capacitor of claim 11 wherein said moisture loss is no more than 1 wt %.
14. The method for forming a capacitor of claim 1 wherein said first conductive polymer layer has a moisture content which is at least 110 wt % of a moisture content of said second conductive polymer layer.
15. The method for forming a capacitor of claim 14 wherein said first conductive polymer layer has a moisture content which is at least 150 wt % of the moisture content of said second conductive polymer layer.
16. The method for forming a capacitor of claim 15 wherein said first conductive polymer layer has a moisture content which is at least 200 wt % of the moisture content of said second conductive polymer layer.
17. A method for forming a capacitor comprising:
providing an anode with a dielectric coating thereon;
applying a first dispersion over said dielectric coating thereby forming a first conductive polymer layer over said dielectric coating,
wherein said first conductive polymer layer comprises a dopant and a hydrophilic material; and
applying a second dispersion over said first conductive polymer layer thereby forming a second conductive polymer layer over said first conductive polymer layer,
wherein at least one of said first conductive polymer or said second conductive polymer comprises a moisture retaining component, and
wherein said moisture retaining component is a material selected from the group consisting of a hydrogel, a molecular sieve, and a molecular container.
18. A method for forming a capacitor comprising:
providing an anode with a dielectric coating thereon;
applying a first dispersion over said dielectric coating thereby forming a first conductive polymer layer over said dielectric coating,
wherein said first conductive polymer layer comprises a dopant and a hydrophilic material; and
applying a second dispersion over said first conductive polymer layer thereby forming a second conductive polymer layer over said first conductive polymer layer,
wherein at least one of said first conductive polymer or said second conductive polymer comprises a moisture retaining component, and
wherein at least said moisture retaining component is encapsulated in a polymeric encapsulant.
19. The method for forming a capacitor of claim 18 wherein said polymeric encapsulant has a Tg of at least 100° C.
20. The method for forming a capacitor of claim 19 wherein said polymeric encapsulant has a Tg of at least 150° C.