SILICONE DIE BOND ADHESIVE AND CLEAN IN-LINE CURE FOR COPPER LEAD FRAME

Applications of copper lead frames to plastic encapsulated VLSI's are increasing these days because of their high thermal conductivity and low cost. However, there is a potential for stress induced problems such as die warpage, cracking, and delamination from the lead frame when a large die is bonded. These failures are caused by the thermal mismatch between the silicon die and the copper lead frame. The purpose of this paper is to describe a stress free die bonding technology. Stress analysis by the finite element method (FEM) and a die bonding experiment were performed, and it was discovered that a die bond adhesive, having a very low Young's modulus, is effective in reducing the thermal stress. A new silicon elastomer adhesive and an in-line cure process named “clean cure process” were developed. In this process, the adhesive is cured quickly on a heat column and volatile organic species, which affect the yield and reliability of devices, which are reduced significantly during cure. By applying this technology, bonding of large dice to copper lead frames was successfully performed. © 1990 IEEE