2019 Volume 58 Issue 1 Pages 147-150
Traditionally, Pb has been added to brass to improve machinability, and it has been used for piping parts and mechanical parts. However, due to the revision of the Drinking Water Quality Standards , there was a limitation on the Pb content of the materials used for piping parts. Therefore, Pb–free brass and solder materials have been developed and put into practical use. In the previous study, a method to evaluate soldering ability of Pb – free solder to Pb – free brass using X – ray transmission image was established. In addition, it was possible to classify the voids generated in the soldered region into four types of “voids in invasion region”, “spherical voids”, “nonspherical voids”, and “shrinkage voids”. It was suggested that the generation of bubbles from the flux was confirmed during the previous research and the cause of the spherical void was caused by the generation of this bubble. Therefore, we focused on flux and conducted experiments. In–situ observation experiments were conducted to confirm the occurrence of bubbles in the flux. It was found that when the in situ observation experiment was carried out, it was possible to suppress the generation amount of bubbles by using the dry flux in which the solvent amount of the flux was reduced. Therefore, a soldering experiment using dry flux was carried out. A parallel two–plate test piece was used as a sample shape. Used flux was dry flux and regular flux. As a result, it was confirmed that when the drying flux is used, the amount of spherical voids can be reduced.
