A 2-BODY FORMULATION FOR SOLDER JOINT SHAPE PREDICTION

Solder shape prediction is essential for accurate fatigue life determi nation and joint design optimization. In the present paper, a new solu tion approach using the surface tension theory is developed to simulta neously predict standoff height wetted surface area, contact angles, a nd solder shape by including energy effects between a molten solder bo dy and an arbitrarily shaped solid body. Existing models for solder sh ape prediction do not appeal; to determine all characteristics includi ng joint standoff height, wetted surface area, and contact angles simu ltaneously. A general two-body axisymmetric finite element code is dev eloped and coupled with a constrained optimizer to solve four illustra tive examples. These examples include the shape of a sessile droplet o n a fixed pad, a flip-chip joint, a sessile droplet on a free surface, and a typical ceramic ball grid array solder joint. In all four examp les, the results predicted by the present approach compare favorably w ith available experimental and numerical results.