A wafer-level burn-in technology using the contactor controlled thermal expansion

A new wafer-level burn-in (WLBI) technology is reported in this paper. By this, firm contacts on 2,756 bond pads provided on a 6" diameter wafer are made in a temperature range from room to 125°C. In order to establish the contacts, a polyimide membrane with nickel bumps (ASMAT^(R) manufactured by Nitto Denko Corp.) is used The polyimide membrane is fixed on a ring of ceramic having a thermal expansion coefficient similar to the silicon substrate so the entire membrane tracks the silicon during thermal changes. The other feature is the use of localized pressure-sensitive conductive rubber (PCR^TM manufactured by Japan Synthetic Rubber Co. Ltd.) establishing connections between the bumps provided on the polyimide membrane and the wiring substrate. The atmospheric pressure in the space between the bumps and the wafer is decreased in order to apply a uniform pressure in-between. By this, problems such as the thermal expansion difference and the thermal shrinkage of polyimide membrane are solved simultaneously. In addition to these, problems of the deviations of bump heights (±3 μm) and the warp of the wiring substrate (±6 μm) are solved by the use of localized pressure sensitive conductive rubber. This leads to a realization of a cost effective and reliable WLBI