Single chip bumping and reliability for flip chip processes

Processes of bump deposition based on mechanical procedures together with t heir reliability data are summarized in this paper. The stud bumping of gol d, palladium, and solder is described and also a novel bumping approach for fine pitch solder deposition down to 100 mu m pitches using thermosonic bo nding on a modified wedge-wedge bonding machine. This wedge bumping doesn't require a wire flame-off process step. Because of this, no active atmosphe re is necessary. The minimum pad diameter which can be bumped using the sol der wedge bumping is 50 mu m, up to now, This bumping process is highly rep roducible and therefore well-suited for different flip chip soldering appli cations. Palladium stud bumps provide a solderable under bump metallization . Results from aging of lead/tin solder bumps on palladium are shown. The g rowth of intermetallics and its impact on the mechanical reliability are in vestigated. (C) 1999 Elsevier Science Ltd. All rights reserved.