Thick-film dielectric and conductive compositions
Dielectric powder and thick-film paste compositions are formed having high dielectric constants, low loss tangents, and other desirable electrical and physical properties. Conductive powder and paste compositions are formed having desirable electrical and physical properties. The dielectric powder and thick-film paste compositions can be used in combination with the conductive powder and paste compositions to form capacitors and other fired-on-foil passive circuit components.
1. A thick-film dielectric fired on copper foil, wherein the dielectric comprises barium titanate, a glass comprising lead and germanium, a zinc source, and a lithium source, and
wherein the barium titanate in the fired dielectric exhibits grain sizes of at least 0.5 microns, and the Curie point of the fired dielectric is in the range of −35° C. to 45° C.
2. The thick-film dielectric on copper foil of claim 1 , wherein the dielectric has a thickness in the range of 10 to 60 microns.
3. The thick-film dielectric on copper foil of claim 1 , further comprising:
an underprint layer disposed between the dielectric and the copper foil.
4. The thick-film dielectric on copper foil of claim 1 , wherein the dielectric comprises barium titanate, zinc fluoride, lead germanate, and at least one of lithium carbonate and lithium fluoride.
5. A capacitor, comprising:
the thick-film dielectric on copper foil of claim 1 , wherein the copper foil forms a first electrode; and
a second electrode disposed over the dielectric.
6. The capacitor of claim 5 , wherein the second electrode comprises copper, cuprous oxide, and lead germanate.
7. An innerlayer panel comprising the capacitor of claim 5 .
8. A printed wiring board comprising the innerlayer panel of claim 7 .
9. A dielectric powder, comprising:
barium titanate powder;
a lithium source and at least one metal fluoride powder, wherein the metal fluoride powder includes a zinc fluoride powder; and
lead germanate glass powder.
10. The dielectric powder of claim 9 , wherein the dielectric powder comprises 73-88% by weight of the barium titanate powder.
11. The dielectric powder of claim 10 , wherein the dielectric powder comprises 1-5% by weight of a combination of the lithium source and the at least one metal fluoride powder.
12. The dielectric powder of claim 11 , wherein the lithium source comprises at least one of lithium carbonate and lithium fluoride.
13. The dielectric powder of claim 10 , wherein the dielectric powder comprises 8-25% by weight of the lead germanate glass powder.
14. The dielectric powder of claim 9 , further comprising:
glass powder comprising at least one of barium, strontium, calcium, zinc, magnesium and manganese.
15. The dielectric powder of claim 9 , further comprising:
glass powder comprising at least one of silicon, zirconium, titanium and tin.
16. The dielectric powder of claim 9 , further comprising:
zirconia powder in an amount that is between 1/25 and ⅓ of the weight of the lead germanate glass powder.
17. A screen-printing composition, comprising:
the dielectric powder composition of any of claims 9 through 16 dispersed in an organic vehicle; and
a solvent.
18. A method of making a thick-film capacitor, comprising:
providing a metallic foil;
forming a dielectric over the metallic foil using the dielectric powder of any of claims 9 - 16 ; and
in any order, firing the dielectric using a peak firing temperature of between 800° C. and 1050° C., and forming an electrode over the dielectric.
19. The method of claim 18 , wherein the dielectric and the electrode are formed by a single firing step in a nitrogen environment.
20. The method of claim 18 , wherein the foil is a copper foil.
21. The method of claim 20 , wherein:
the dielectric has a thickness in the range of 10 to 60 microns; and
the Curie point of the dielectric is in the range of −35° C. to 45° C.
22. The method of claim 18 , wherein the electrode is formed from a powder comprising:
copper powder;
cuprous oxide powder; and
lead germinate glass powder.