IMMERSION Sn/Pb PLATING BATH FOR TAB TAPE
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2002-Feb-11
The majority of ASIC packages that ar being planned for future generations of the 0.5pm BiCMOS technol- ogy are in the TAB format due to the high pincount requirements. The only hvo lead fmish options currently available are Sn and Au. Both of these lead finishes have liabilities. The Sn has a tendency to grow whiskers, a single mono!iIament crystal whose growth rate is a func- tion of time and temperature. Whiskers on any elec- tronic part can cause long term reliability problems because the whiskers eventually can grow to an adja- cent lead and short the device. The Au lead finish increases unit costs and requires higher bonding forces that can potentially jeopardize barrier integrity. If immer- sion solder were offered the costs would remain low and the whisker problem could be eliminated. Currently there is no immersion solder system available from plat- ing bath manufacturers that can operate in the thin thick- ness ranges required for TAB tape.