This paper presents an understanding of a new mechanism of void formation in an epoxy-amine underfill system resulting only from interaction of the underfill with a decomposition product of residual chip attach flux formed during package assembly. This is possible since flux residues have been known to sometimes be retained between the die and substrate even after the deflux process. Differential Scanning Calorimetry (DSC) was used extensively to study the thermal properties of both flux and underfill and to simulate the heating processes that these materials undergo at assembly. Thermal Gravimetric Analysis (TGA) was used to confirm the mechanism. This study does not make any attempt to explain the other effects contributed by equipment, bump pitch, filler size or any mechanical aspect on the voiding process. [
The choice of epoxy mold compound (EMC) for an electronic package is based mostly on how much protection it provides to the active components in the package. But the choice is not a straightforward process. Rather it is mostly trial and error using different assembly parameters to find the most robust material while assembly defects are monitored. One such defect associated to EMC processing is wire sweep, and many studies have shown that it is mainly caused by viscosity changes in the EMC. In this study, samples of EMC in various stages of shelf life and staging times were analyzed for degree of cure using a method called differential scanning calorimetry (DSC). Samples are then processed at assembly for wire sweep measurement. It was found out that degree of cure increases with staging time at different rates for each shelf life. It was also found out that wire sweep did not only increase with degree of cure but it was also found to be predictable with respect to the latter. Using this information, the age and staging limit for each material was identified that would not cause wire sweep issues.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.