Method of making thin-film capacitors on metal foil using thick top electrodes
Methods of making thin film capacitors formed on foil by forming onto a thin film dielectric in a single deposition event an integrally complete top electrode having a minimum thickness of at least 1 micron.
1. A method of forming a thick top electrode on a thin film dielectric formed on a metal foil comprising:
providing a metal foil;
forming a thin film dielectric on said metal foil;
depositing a conductive paste or a conductive tape or a conductive slurry onto said thin film dielectric formed on said metal foil, thereby forming a thick top electrode, wherein the depositing includes screen printing when the paste is used, laminating when the tape is used and casting when the slurry is used;
firing the conductive paste, conductive tape or conductive slurry and the dielectric at a temperature in the range between 500° C. and 900° C., thereby forming at least one thick top electrode directly on the thin film dielectric, wherein said thick top electrode has a thickness of from 1 to 30 microns, and wherein said metal foil, said thin film dielectric and said thick top electrode form a capacitor having a capacitance density of greater than 0.5 μF/cm 2 ; and further comprising: reoxidizing the dielectric in a reducing atmosphere having a partial pressure of oxygen from 10 −5 to 10 −6 atmospheres.
2. The method of claim 1 , further comprising:
patterning the thick top electrode by screen printing, thereby forming individual electrodes.
3. The method of claim 1 , wherein the depositing further comprises depositing the conductive paste, conductive tape or conductive slurry on an un-annealed dielectric;
co-firing the conductive paste, conductive tape or conductive slurry and the dielectric, whereby the dielectric is crystallized and the top electrode sintered.
4. The capacitor formed according to the method of claim 1 .
5. The capacitor formed according to the method of claim 1 .
6. The capacitor formed according to the method of claim 2 .
7. The capacitor formed according to the method of claim 3 .
8. The method of claim 1 wherein said thick top electrode comprises a plurality of individual electrodes formed directly on the thin film dielectric.
9. The method of claim 1 wherein the thin film dielectric is formed by a method selected from sputtering or chemical solution deposition.
10. The method of claim 1 wherein the thick top electrode is formed by screen printing a conductive paste on the thin film dielectric.
11. The method of claim 1 wherein the thick top electrode is formed by laminating a conductive tape on the thin film dielectric.
12. The method of claim 1 wherein the thick top electrode is formed by casting a conductive slurry on the thin film dielectric.
13. The method of claim 1 wherein forming the thin film dielectric on said metal foil includes depositing a thin film dielectric layer on said metal foil and annealing the thin film dielectric layer at a temperature in the range between 800° C. and 1400° C.
14. The method of claim 1 further comprising the step of cleaning and polishing a surface said metal foil, and wherein the thin film dielectric is formed on the cleaned and polished surface of said metal foil.