Characterizations of soft-gel thermal interface materials for flip chip package

During the thermal interface material development for flip chip packages, it was found that the shear modulus, G´, was a key parameter impacting the material processing and package thermal performance. If the G´ was too low, the thermal interface material was easy to be pumped out after curing; If the G´ was too high, delamination occurred at the interfaces between the thermal interface material and die or heat spreader, especially at the die corners. Due to the significant warpage caused by the large die size, the thermal interface material needs to be a soft gel. This will allow the material to maintain its interfacial adhesion at a large deformation. In this paper, we will discuss the shear modulus testing method for thermal interface materials development.