The Nature of White Residue on Printed Circuit Assemblies

The sudden appearance of white residue on circuit board assemblies after cleaning indicates that something in the soldering/cleaning process has gone out of control. The variety of chemicals, the similarity of materials (rosin vs. resin), the instability of solvents and changing heat could all enter into the creation of white residue. Reactions and stability of the rosin causes most of the residue, but board and component materials can also contribute to the problem. It is time consuming to evaluate all of the possibilities but quite often a quick chemical testor microscopic examination can determine the nature of the "residue" or in fact, if tit evenis a residue.