Volume Shrinkage Characterization of Underfill Materials

In general, different coefficients of thermal expansion (CTE) values of constitutive materials are considered as the main cause of warpage for flip chip packages. Accordingly, during the past years, the cure-induced volume shrinkage in integrated circuit packages has been neglected in warpage simulation. However, in recent years, there are more and more evidences showing that it is not sufficient to predict the amount of warpage if considering only the CTE values of different component materials in a package especially after molding. There have been some reports about cure induced shrinkage for EMC materials. However, there is no cure induced volume shrinkage report about underfill materials. In this study, the behavioral evolution of volume shrinkage of underfill material during curing process was described by a pressure-volume-temperature-cure (P-V-T-C) equation. The P-V-T-C equation of the underfill material was developed by employing the thermal analyzer, dilatometer and statistical technique. Three successive procedures were conducted for the measurement of the P-V-T-C relation. First, the reaction kinetics and isothermal conversion of the underfill were determined by employing DSC and statistical technique. Second, isobaric and isothermal volume shrinkage of underfill was monitored with a pressure-temperature-controlled dilatometer. Third, the P-V-T-C equation was established by combining the data of volume shrinkage and conversion.