Low Warpage Molding Compound Development for Array Packages

Warpage after molding is a critical issue for array packages due to singulation and soldering requirement in subsequent assembly. Warpage is greatly affected by package geometries, such as dimensions of matrix block, pad, die, and passive components, as well as molding compound properties. One set of molding compound properties may generate very low warpage in one array package, but generate unacceptable warpage in another. To achieve minimum warpage in all geometry variations, molding compound properties have to be tuned for each package. In this paper, molding compounds with multifunctional epoxies and hardeners were developed. The curing shrinkage and Tg of the molding compounds were easily adjusted while other major properties kept consistent. Methodology taken to tackle the issue was discussed. Warpage of array blocks/strips built with modified molding compounds was measured by shadow Moiré method to correlate warpage with molding compound properties. Finite element analysis was also performed to predict and correlate effects of modulus, CTE, and shrinkage on warpage, as well as further compound modifications