New Plateable Thick Film Silver Conductors for DuPont™ Green Tape™ Low Temperature Co-Fired Ceramic (LTCC)

Low Temperature Co-fired Ceramic (LTCC) provides a technology option for designers that combine the benefits of HTCC and thick film technologies and is the technology of choice for many complex automotive, consumer, and military applications. Circuit cost is always a primary consideration. The traditional method employed to address cost has been the use of mixed metallurgies, rather than using all gold. Silver based conductors for signal and ground are used internally, with precious metal based transition via fill compositions that interconnect to gold conductors used for wire bonding or brazing, or other solderable conductors, externally.

Plating external silver based conductors with electroless Ni/Au offers a reliable and lower cost alternative to the mixed metals approach. Some advantages of plating include; elimination of precious metal containing transition via fill compositions and gold external conductors, the use of a single metallurgy throughout the circuit, all resulting in the additional cost reduction, and a smooth gold plated surface ideal for wire bond acceptance, or pin brazing.

This paper introduces three new silver based thick film conductor compositions that are plateable with electroless Ni/Au for use with Green Tape™ 951. Reliability and performance are discussed in detail and include; 25 micron Au wire bonding, pin grid array brazing, and soldering. Data include thermal cycle/thermal shock evaluations, environmental performance using 85%RH/85ºC, and thermal aging.