Growth Rate
Reaction rates governing gas bubble behavior explain how empty spaces form within a solder joint. The study of voiding kinetics looks at the speed at which bubbles merge and move during the molten phase of reflow. This science helps engineers understand why certain alloys or pad finishes are more prone to defects.
It provides a mathematical way to predict the final density of the connection.
Surface Energy
Forces at the boundary of the molten metal determine if a gas bubble will stay trapped or escape. Voiding kinetics are influenced by the surface tension of the solder and the wetting properties of the flux. If the solder wets the pad quickly, it can push the air out before it becomes a void.
Such interactions are a primary focus for designers of high-power electronics.
Phase Change
Temperature changes throughout the reflow cycle alter the viscosity of the liquid metal and the behavior of the gas. Analyzing voiding kinetics allows manufacturers to optimize the cooling rate to minimize the size of the internal gaps. This research is essential for improving the thermal performance of heat sinks and power modules.
Small changes in the chemical composition of the solder paste can have a large effect on these outcomes. The data from these studies is used to refine the manufacturing standards for all high-reliability boards.
