Thick film conductor compositions and the use thereof in LTCC circuits and devices
View Patent ↗The present invention is directed to a thick film composition for use in low temperature co-fired ceramic circuits comprising, based on weight percent total thick film composition: (a) 30-98 weight percent finely divided particles selected from noble metals, alloys of noble metals and mixtures thereof; (b) one or more selected inorganic binders and/or mixtures thereof, and dispersed in (c) organic medium, and wherein said glass compositions are immiscible or partially miscible with remnant glasses present in the low temperature co-fired ceramic substrate glasses at the firing conditions. The present invention is further directed to methods of forming multilayer circuits utilizing the above composition and the use of the composition in high frequency applications (including microwave applications).
1. A lead free thick film composition for use in low temperature co-fired ceramic circuits comprising, based on weight percent total thick film composition:
(a) 30-98 weight percent finely divided particles selected from noble metals, alloys of noble metals and mixtures thereof
(b) 0.2-20 weight percent of inorganic binder material containing one or more high-softening refractory glass compositions with a specific viscosity (log n) in the range of 6-7.6 at the firing temperature of said circuit, wherein said refractory glass compositions comprise, based on weight percent total glass composition, 40-60% SiO 2 , 10-20% Al 2 O 3 , 10-15% B 2 O 3 , 15-25% CaO, and 1-5% balance other network modifying ions; dispersed in
(c) organic medium; and
wherein said glass compositions are immiscible with remnant glasses present in the low temperature co-fired ceramic substrate glasses at the firing conditions, and said firing is at 300-600 degrees C. after a 5-20 minute period of firing at 800-950 degrees C.
2. The composition of claim 1 wherein said noble metals are selected from Au, Ag, Pd, and Pt.
3. The composition of claim 1 wherein said alloys of noble metals are alloys of metal selected from Au, Ag, Pd and Pt.
4. The composition of claim 1 wherein said noble metal is Au.
5. The composition of claim 1 , wherein the inorganic binder material further comprises 0.1-5 weight percent, based on weight percent total thick film composition, an additional inorganic binder selected from the group consisting of (i) metal oxides, (ii) precursors of metal oxides; (iii) non-oxide borides; (iv) non-oxide silicides; and (v) mixtures thereof.
6. The composition of claim 5 wherein said metal oxides are selected from oxides of Zn, Mg, Co, Al, Zr, Mn, Ni, Cu, Ta, W, La and mixtures thereof.
7. The composition of claim 5 wherein said precursors of metal oxides are precursors of Zn, Mg, Co, Al, Zr, Mn, Ni, Cu, Ta, W, La and mixtures thereof.