Volume resistivity solder replacement adhesives

Silver-filled epoxies and other electrically conductive adhesives are widely used to electrically connect chip devices or packaged components to interconnect substrates or printed-circuit boards. Chip capacitors, resistors, transistors, diodes, and magnetic components may be attached with silver-filled epoxies whose volume resistivities range from 1 x 10 " to 3 x 10 " ohm-cm or with gold-filled epoxies whose volume resistivities are approximately 8 x 10 ohm-cm. Conductive adhesives are also finding use as replacements for solder balls in flip-chip devices. In all cases, to achieve reliable connections, initially low-contact resistances or volume resistivities must remain low on aging and on exposure to operational stress conditions, such as humidity, temperature, vibration, shock, and power. 

Electrically conductive adhesives that are used as solder replacements are evaluated for material characteristics and contact resistance on solder surfaces. In one study, the requirement for volume resistivity is given as 0.001 Q-cm or less and for contact-resistance change as 20% or less after 500 hours of 85/85-exposure. ... 

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