Conditions for the Measurement of Surface Tension of Solders with a Wetting Balance Tester(Materials, Metallurgy & Weldability)

概要

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A method for measuring the surface tension of solder alloys has been developed by using a wetting balance tester and the measuring conditions have been examined. A non-wetting rod was immersed into a molten solder bath at a fixed speed, and the surface tension was calculated by analyzing the measured force-immersion depth relationship. The theoretical model is based on the hypothesis that the meniscus configuration of molten solder gradually varies depending on the depth of the immersing rod and its radius, and the configuration shows a stable form when the depth reaches a critical value. After exceeding the critical depth, the force increases in proportion to the immersion depth of rod. Therefore, the surface tension can be measured by analyzing the force-time curve produced. It was found that the most suitable non-wetting material for measurement was Al_2O_3. It is important for obtaining an accurate surface tension to adopt a low immersion rate and to dry the rod after fluxing. Soldering flux reduced the surface tension of Sn-Pb solder and lead-free solders.
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