Wetting Force
Solderability measurement quantifies the ability of a component lead or circuit board pad to be wetted by molten solder within a specific time. Wetting balance testing uses a sensitive force transducer to record the buoyancy and surface tension forces as a sample is dipped into a solder bath. The resulting curve shows the transition from non-wetting to full wetting by plotting force against time.
Surface Energy
Testing begins by immersing the cleaned and fluxed sample at a controlled rate and depth. During the initial contact, the solder pushes against the lead, but as wetting occurs, the solder climbs the surface and pulls the lead downward. This change in force is recorded in millinewtons and provides an objective measure of the surface energy.
Technicians compare the time to cross the zero-force line against industry standards to determine if the parts are suitable for assembly. The test also identifies the maximum wetting force, which indicates the final strength and stability of the bond that can be expected in a production environment.
Time Analysis
Quantitative data from this method is more reliable than visual inspection because it detects subtle contamination or oxidation that might not be visible under a microscope. While visual checks are subjective, wetting balance testing provides a repeatable pass or fail result based on the speed and strength of the wetting action. Standardized results from this methodology verify the shelf life of components in long-term storage.
