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JULY 2025 I SMT007 MAGAZINE 51 K N O C K I N G D OW N T H E B O N E P I L E Wetting Balance Test Method The wetting balance test method's foremost advantage is its precision in measuring the forces involved in wetting molten solder onto a test speci- men. Quantifying these forces as a function of time provides detailed, reproducible data on solderabil- ity that surpasses visual inspection methods, mak- ing it an invaluable tool for evaluating solderability in research and quality control environments, par- ticularly when assessing subtle differences or the effects of process variations. However, there are no established indus- try standard pass/fail criteria for wetting bal- ance analysis, so engineers use it primarily as a tool rather than a routine production monitor. To establish a definitive pass/fail criterion, engineers perform a dip-and-look test to confirm solder- ability visually, since an acceptable wetting force alone does not guarantee a defect-free joint. For instance, after converting a RoHS-compliant Figure 2: T he b efore and af ter of solderabilit y cur ves. ▼ device, such as a 20-mil pitch quad flat package (QFP) to tin-lead, a wetting balance test may show a bridge-free result (Figure 1). Inspectors must val- idate it visually. Another disadvantage is needing skilled per- sonnel to interpret the wetting curves accurately. The results can be easily misinterpreted if the sys- tem is not properly calibrated or if tests are per- formed improperly by untrained or inexperienced operators. For example, misreading the differences between the "before" and "after" solderability curves, such as those from a re-tinned component, can lead to incorrect conclusions about the com- ponent's performance or the effectiveness of the re-tinning process (Figure 2). This technique also demands a controlled labo- ratory environment to maintain consistent test con- ditions, including temperature stability and proper calibration of the testing equipment. Misalignment, improper specimen preparation, or inconsistent