Wire bond development for high-pincount surface-mount

The continuous miniaturization of computers necessitates the use of new high pin count plastic packages such as TQFP (thin quad flat pack). These new package types, with 1.4-, 1.0-, or 0.8-mm plastic package body thickness, have very limited space for bond wire, specifically in the loop height dimension. This restriction imposes a challenge to the traditional wire bond technology, especially when long wire is needed for small die. The author reviews the constraints a thin plastic package imposes on wire bonding, and presents a statistical design of an experiment based on a response surface methodology to characterize wire loop profile control. Based on the regression equations generated, a mathematical model is established to guide the development of a predetermined loop profile suitable for thin plastic package assembly. The effects of major bonding parameters, such as wire length, kink-height, reverse loop, loop factor, bonding speeds, and wire tension, and their interactions on loop profile are analyzed