Brass has excellent ductility and workability. To comply with environmental regulations, such as water quality standards, Pb–free brass containing Bi and Si has been put into practical use. However, brass soldering using lead–free solder is required for actual use. In our laboratory, we conduct soldering and brazing experiments using pure copper and Pb–free brass. These experiments yield a large amount of data. However, the experimental results confirmed that the wetting spread was nonuniform when the brazing material penetrated. The reason for this nonuniform wetting has not yet been clarified. Therefore, this study aims to quantitatively clarify the cause of nonuniform wetting during soldering and brazing by comparing the data from previous studies using parallel two–plate test specimens. The experimental results using specimens with various modifications suggest that the nonuniform wetting is caused by the temperature distribution in the gap and the gap shape. The gap shape was found to have a greater effect on wetting than temperature distribution.
