High impact bonding to improve reliability of VLSI die in plastic packages

Tests performed to determine the critical thermosonic bond parameters and their impact on gold-wire ball bond reliability in large, high-pin-count, plastic-encapsulated integrated circuits are discussed. Bond-pad cratering, lifted metal, and lifted balls are recognized as a serious quality problem in the industry, resulting in assembly yield loss as well as potential reliability problems. It has been found that the strength of the silicon dioxide structure beneath the bond pads is greater for short-duration dynamic forces than for static force. The application of much higher bond forces during ball touchdown, combined with a reduction of static mash force, was found to reduce damage to the subsurface structure and improve reliability of ICs known to be sensitive to cratering problems