Solderability Tests Toward Miniaturized Microelectronics: Applicability and Limitations of Micro-Wetting Balance Testing of SnAgCu and SnBi Solders

This study presents a comprehensive investigation of the micro-wetting behavior of SAC305 and SnBi58 solders on chip components. Micro-wetting balance tests, which employ small solder globules, enable direct evaluation of solder wettability on miniature electronic components such as 1206 chip resistors and 1206 and 0603 chip capacitors. Unlike conventional wetting tests that use large solder baths, the micro-wetting method suppresses excessive solder rise, making it suitable for testing small-scale components. The results demonstrate that micro-wetting testing is a reliable method for evaluating solder wettability on chip components when appropriate globule size, test temperature, and experimental parameters such as immersion depth and speed are carefully controlled. Among the tested conditions, 2 mm diameter solder globules are identified as the optimal choice because they offer improved thermal management and reduced surface oxidation. The wetting times measured for SnBi58 are comparable to those obtained for conventional SAC305 solder, whereas the maximum wetting forces are generally lower. However, micro-wetting curves exhibit noticeable fluctuations, which complicate the analysis of additional parameters, such as maximum wetting force and wetting rate, and limit direct comparison with standard reference values.