Comprehensive Study on Die Shift with Ultra-Large Embedded Multi-Die Wafer Level Packaging

Abstract

Embedded wafer level packaging technology (eWLP) has gained interest for promoting multi -die packages in small volume with high performance [1]. Several factors such as thermal expansion, mold compound shrinkage and mold-flow will affects the die shift [2]. The eWLP package is getting larger and larger to accommodate multi -dies to further increase the functions of the package. Die with different sizes may experience different die shift magnitude as bigger die has stronger adhesion as compare to die with smaller dimension. Stronger adhesion helps to resist the impact of mold flow during the compression molding process. Ultra-large package indicated that the volume of mold compound inside the package is much higher than those packages with smaller dimension. As such, the impact of mold shrinkage and thermal expansion is greater for ultra large eWLP package. In this paper, we will evaluate the die shift for various die sizes for an ultra-large package of 32.05×26.7mm. And hence a method of optimizing the die shift for the various die size in an ultra-large package is developed in this study. The dies will be picked and placed on a taped carrier and then to be molded. After molding, each die position is measured by using Nikon Confocal tool. The die shift is then determined by subtracting the die position with the designated position. Die shift will be compensated based on graphical x-y plot. The outcome of the die shift will be analysed after compensation and fine tune the die shift if necessary. In summary, we had demonstrated the die shift is less than 15um for 3 different die sizes in an ultra-large eWLP package.