Single chip bumping and reliability for flip chip processes
Processes of bump deposition based on mechanical procedures together with their reliability data are summarized in this paper. The stud bumping of gold, palladium, and solder is described and also a novel bumping approach for fine pitch solder deposition down to 100 ?m pitches using thermosonic bonding on a modified wedgewedge bonding machine. This wedge bumping doesnt require a wire flame-off process step. Because of this, no active atmosphere is necessary. The minimum pad diameter which can be bumped using the solder wedge bumping is 50 ?m, up to now. This bumping process is highly reproducible and therefore well-suited for different flip chip soldering applications. Palladium stud bumps provide a solderable under bump metallization. Results from aging of lead/tin solder bumps on palladium are shown. The growth of intermetallics and its impact on the mechanical reliability are investigated.
single chip bumping reliability flip chip stud bumping palladium wedge bumping