Measurements of the solders surface tension values

The knowledge of actual value of surface tension is important for the understanding to several soldering aspects, such as wetting, joint shape, fluxing action and, particularly, for the quantification of solderability testing. High surface tension is required for wave soldering. Values of surface tension are mainly caused by measurement conditions (temperature, ambient — air, inert atmosphere of the different composition etc.). For our measurement we used one of the solderability evaluation methods known as the wetting balance method, which is used to measure wetting force. Wettability tester (sometimes called a meniscograph) was placed in the box with the possibility to reduce oxygen concentration. The measurement was carried out on two different types of solders (lead and lead free) and on non-wetting measurement specimen (teflon, nonstick cylinder). We have measured influence of the temperature and reduced oxygen concentration on the wetting force. The change of the wetting force is related to the change of the surface tension.