Simulation of void growth in molten solder bumps

This research studies the motion of void bubbles within molten solder bumps. Surface tension variation on the outer surface of the bump drives a flow that is transmitted to the interior by viscosity. Bubbles inside the bump grow by collisions with other bubbles. A computer model of this process has been formulated. In cases with the melting process from top to bottom, a ring of bubbles collected at the top outer rim of the solder bump. When the melting direction was reversed, the typical result was a single large bubble near the center with a few smaller recirculating bubbles.