Development of reworkable underfills, materials, reliability and processing

The rework of packages is a standard practice in surface mount technology (SMT) assembly. The reasons for rework include process yields, failed parts, and field returns. The implementation of flipchip has been hindered by the lack of reworkability following underfill cure. Current commercial underfills do not allow for the rework of the flipchip. The development of a reworkable underfill is described in this paper. The materials selection process, information on the process for rework as well as pertinent reliability data are described.