In this study, a real-time probe was developed for in-process measurement and recording of package deformation during simulated solder reflow. The objective was to obtain fundamental insights into the stresses seen by the package during reflow, to guide package design, modeling, material selection, and process improvement efforts.
Experiments were conducted to obtain temperature and time resolved deformation
signatures of packages due to the applied reflow profile. The occurrence
of delamination and cracking and the reflow parameters associated with
its initiation were identified using the deformation plots and the observations
were verified by post-reflow inspection using scanning acoustic microscopy.
Absorbed moisture in the package was found to play a role in package deformations
beyond 90 degrees Celsius, with an increased rate of deformations beyond
approximately 138 degrees Celsius. Partial reflow simulation experiments
revealed that these deformations were not caused by the initiation and
growth of interfacial delaminations, but rather to moisture-induced swelling
and thermal expansion effects.
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