Study of low-modulus die attach adhesives and molding compounds on warpage and damage of PBGA

Numerical experiments based on the three-dimensional (3D) nonlinear finite element method (FEM) has been conducted to understand governing damage mechanisms during the die attachment for the ball grid array (BGA) packages. The parametric studies for various designs of the BGA package and material properties have been performed. A wide range of the modulus (1MPa~30GPa) and the coefficient of thermal expansion (CTE) (10ppm ~ 300ppm) were evaluated to see feasibility of a new class of material set in the die attach adhesive. Effects of thermo-mechanical properties, particularly glass transition temperature (Tg) of selected die attach adhesives on the damage and warpage of the die and substrate of BGA are analyzed. The warpage of substrate and Si die cracking due to the material properties of the die attach adhesive are demonstrated. Classification of modes of deformation in the BGA package with material sets will shed light on novel material development for better reliability. In addition, the optimum thermo-mechanical properties of die attachment materials and molding compounds will be selected based on the parametric studies