Patent ID: 7611645

Claim:
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.