Comparative analysis of two heat spreader designs for a wire bond TBGA package

Thermal management is becoming increasingly significant in semiconductor devices because of greater functional densities and smaller devices. A critical factor in obtaining better heat transfer from cavity down devices is the proper choice of heat spreader design. In an earlier study Guttikonda, S.C. and Sammakia, B.G. [2001] presented a comparative basic analysis of two types of heat spreader design and also studied the effect of forced convection cooling for different velocities. It has been noted that the single piece type of heat spreader, with a cavity for the die, is superior to a design incorporating separate heat spreader and stiffeners. The adhesive between the stiffener and the heat spreader was identified as a major resistance in the heat flow path. In the present study a detailed parametric study of the effects of various factors that are responsible for the difference in performance of two designs, is presented. These factors include possible delamination between the die and cover plate/heat spreader and the thermal conductivity of the die attach. The authors also obtained trends to study the effects of heat spreader thickness. All results point towards better performance by the single piece design from a thermal standpoint.