Modeling BGA Solder Joint Distortion Due to Warpage

This video illustrates how corner balls on BGA packages tend to elongate into hourglass shapes during reflow soldering.  We use Surface Evolver TM to model the shape change and hope to further study instability that can lead to head-on-pillow defects. The center balls compress due to the same package warpage strain that elongates the corner balls.  In extreme cases, this can lead to shorted signals and flux entrapment near the center of the BGA.  Analysis of this type can help to prevent defects in production hardware.

Edward Hare, PhD and Stephanie Hare, PhD


How Much Is Too Much BGA Warpage?

At SEM Lab, we are interested in understanding deformations of solder joints that lead to failures in BGA packages. Using Surface Evolver TM software, we can model theoretical shape changes and calculate energy changes during these transformations. Discontinuities in the energy plots show us at what height a surface becomes unstable and separates into two droplets during reflow. We can then make predictions as to the amount of deformation that BGA packages can withstand before severe defects occur.

Edward Hare, PhD and Stephanie Hare, PhD


See also related work:
BGA assembly validation 
BGA solder joint microsections
Calculating BGA warpage