Pan Pacific Symposium Conference Proceedings


Authors: Akira Ohuchi, Tomoo Murakami, and Tsutomu Kawata
Company: NEC Corporation
Date Published: 2/10/2004   Conference: Pan Pacific Symposium

Abstract: We have developed no-flow underfill technology for flip-chip bonding of large LSIs with fine-pitch connections. Thermal-cycle testing has shown that package reliability can be assured by using resin to which appropriate fillers have been added in order to prevent fillet cracks. When no-flow underfill technology is used, however, fillers in the resin interfere with the solder joints.

Exploring the trade-off relation between high reliability and good solder joints, we have improved the outlook for no-flow underfill technology by using a local reflow process and high-temperature or lead-free solder bumps. Reliability tests found no open-circuit or short-circuit failures after 1500 cycles between -40°C and 125°C, and we have also confirmed that this process can provide void-free packaging.

Key Words: flip-chip bonding, no-flow underfill , solder joint, void, fillet crack.

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