In-situ measurements of surface mount IC package deformations during reflow soldering

In this study, a real-time probe was developed for in-process measurement and recording of package deformations 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/spl deg/C, with an increased rate of deformations beyond approximately 138/spl deg/C. 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.