Dewetting / Nonwetting

The terms de- or nonwetting are applied when a surface does not accept the liquid solder. In this case, no diffusional reaction between the liquid solder and the interface of the substrate takes place, and a diffusion layer in the form of an intermetallic zone is not formed. This can be observed in the soldering process when the surfaces to be soldered, be it the component lead or the pad, are excessively contaminated or oxidized. The solder will withdraw from the surface and form solder droplets or balls, instead of wetting the surface or the component. Application of a more aggressive flux or an abrasive cleaning of the surface can help to overcome wetting issues.