Field-operable microconnections using automatically-triggered localized solder-bonding

This paper presents an approach to realizing high-density electrical and mechanical connections to delicate microstructures in the field. "Smart" pads automatically detect proper contact alignment and activate a local heating element to create solder bonds between the pads and the pre-soldered lead tabs of a miniature flexible cable. The bonds occur in 350 ms and result in less than 10 /spl Omega/ of series resistance between the cable and the pad. Connections have been demonstrated with lead-pitches as small as 100 /spl mu/m and connection areas of less than 0.375 mm/sup 2/ per pad. The pad areas are fabricated with a five-mask circuit-compatible process. The flexible ribbon cables are made of polyimide with copper conductors. This work represents the first use of localized solder-bonding for making connections between microstructures and silicon substrates.