Fine pitch wire bonding development using a new multipurpose, multi-pad pitch test die

A multipurpose, multipad pitch test die with pad pitches ranging from 5 mil down to 3 mil, suitable for evaluating gold-ball bonding, aluminum wedge bonding, tape automated bonding (TAB), array bonding, wafer probes, and molding operations has been designed and manufactured. The author reviews the design features of this multipurpose, multipad pitch test die, and presents the statistical design of experiment strategy taken in developing a wire bond process for very-fine-pitch assembly based on this test die. The effect of major bonding parameters on bond ball size and ball shear force is discussed. A statistical method for predicting the ball shorting rate is compared with actual assembly yield data. The experimental results show that using a K&S 1484 bonder with a bottleneck capillary and 1.3-mil-diameter gold wire bonding down to 4.5-mil pad pitch has reasonably good yields. The projected ball shorting rate for 4.5-mil pad pitch is 0.02% for a 128-pad device, or 0.03% for a 160-pad or 208-pad device. The projected ball shorting rate for a 4.3-mil pad pitch die with 128 pads is 0.39%.<
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