Capillary Effect
The capillary effect is based on the principle of surface tension. In the soldering process, it assures that the solder rises - because of this capillary force - into the cracks between the parts to be joined and up to the top side of the assembly to wet the land, and to finally form the solder joints and the fillets expected. In the desoldering process using a solder wick, the same principle is applied when removing excess solder from the joint and into the wick through capillary action.