Soldering terminology

If you fill a fluid (liquid solder) into a tube, its surface bulges either upward (convex meniscus - Fig. a) if the liquid does not wet the tube wall or downward (concave meniscus - Fig. b) if wetting does take place. In this way, the wettability of a base material can be studied through a solder. However, it may happen during soldering that the molten flux climbs up the lead wire stuck in the contact hole and thus the hole filling is interrupted so that a cavity is formed. See also Capillary effect.