Conformal Coating Adhesion … To Stick or Not to Stick?

Increased sophistication in the manufacture of electronic circuits, together with the ever more widespread adoption of conformal coatings, has led to new problems which are frequently the result of an interaction between residual surface chemicals and the electronic circuits themselves. In some instances poor adhesion between the conformal coating and the substrate may be experienced. This paper intends to assist the engineer in identifying where the problem may lie which only through appropriate quality process control and testing can be suitably resolved. It is important for the reader to consider whether there is a problem, if a circuit assembly has been exposed to, and passed, the required environmental testing regime, yet upon subsequent examination the coating is found to have an unusually poor level of adhesion. It is also particularly relevant to appreciate that there are currently no formal standards of entirely suitable test methods to determine what is an acceptable level of adhesion.