Solderability Tester
Analytical instruments designed to measure the dynamic capillary forces exerted by molten solder on a test specimen provide quantitative data on surface solderability. This apparatus, known as a wetting balance, measures the forces as a function of time during a controlled dipping cycle.
Force Transduction
Sensitive force transducers detect the transition from initial buoyancy to positive wetting force as the specimen is immersed. As the solder climbs the specimen surface, the balance records the vertical force exerted by the liquid meniscus. This transducer signal is converted into a continuous force-time curve.
Dynamic Profile
The resulting force-time curve provides several critical parameters including the wetting start time, the time to reach zero force, the wetting rate, and the maximum wetting force. When a surface is contaminated or oxidized, the curve displays a delayed start time or a low maximum force. This behavior contrasts with a highly solderable surface which reaches maximum force almost instantaneously.
These parameters allow engineers to compare the performance of different surface finishes or flux formulations.
Calibration Tolerance
Standardized test methods dictate the calibration of the balance using a reference weight of known mass. The transducer must resolve forces with milligram precision to ensure repeatable results across different laboratory locations. These procedures are executed at regular intervals.
