UV curable conformal coating with moisture shadow cure

摘要

A conformal coating composition is made from a mixture of acrylamide functional polydimethylsiloxane, a methacrylate functional/dialkoxy polydiorganosiloxane, reactive diluent including isobornyl acrylate, cyclohexyl acrylate, and 2- ethylhexyl acrylate; a photoinitiator combination of 2-hydroxy- 2-methylphenylpropanone and 2- methyl-1-[4- (methylthio)phenyl]-2- morpholenopropanone, an amine including dimethylethanolamine and diisopropylethylamine, and an organic titantate. The composition has a viscosity of from 0.07 to 0.2 Pa.s at 25° C. and cures by exposure to ultraviolet radiation and to atmospheric moisture, i.e. a dual curing composition. This composition cures too fast by exposure to ultraviolet radiation in the presence of nitrogen resulting in a distorted surface and therefore for coating printed circuit boards it is recommended that it be cured in air so that the rate of cure is reduced and no surface distortions are formed.