Qualifying Methods of Conformal Coatings used on Assembled Printed Circuit Boards

Increased protection of printed circuit boards (PCB) is required in some fields of the electronic industry, because of the diverse climatic circumstances in which these devices are used. This increased protection is reached by the use of different conformal coatings. The article summarizes the temperature-related and the electric parameters of these materials, and classifies them from the viewpoint of their chemical resistance. Furthermore, it demonstrates the influences of two environment tests (thermal shock and thermal humidity tests) on the insulation resistance of two coatings (Dow Corning: 3-1953 silicone elastomer [1] and PETERS:TWIN-CURE DSL 1600 E-FLZ polyurethane-polyacrilate copolymer [2]), in function of the duration of exposing. After that, it demonstrates the formation of polycondensational cross-linking coatings in function of time and layer thickness, and it touches on the measurement of the dielectric strength as well.