Impact of Conformal Coating Material on the Long-Term Reliability of Ball Grid Array Solder Joints

Conformal coating is a protective chemical material, such as acrylic, silicon, parylene or urethane, that can be applied as a thin layer on printed circuit board assemblies. The purpose of conformal coating is to prevent moisture, corrosive chemicals and ionic particles from reaching the electrical components which, as a result, reduces the risk of electrical shorts and leakage currents. On the other hand, since conformal coating materials have different mechanical properties from electronic components, their use may induce additional mechanical stresses within the board. In this paper, an experiment was conducted to address the effect of a polyurethane conformal coating material on the reliability of ball grid array packages. Three samples of coated modules with different thicknesses in addition to one sample without the coating material were used to conduct thermal cycling testing. Failure rates are compared amongst the different samples. (C) 2019 The Authors. Published by Elsevier B.V.