Miscellaneous Dielectric Coatings and Adhesives

The performance of different kinds of solder masks (UV-cured acrylated, thermally cured epoxies and alkyd/amine systems and dry film solder masks) under humid conditions at elevated temperatures is described by Fox All systems suffer from serious reduction of insulation resistance. The soldering process partially restores the insulation resistance. 

Dual cure coatings, based on multifunctional acrylates to which a small quantity of a polythiol has been added, have been proposed as conformal coatings for completed printed circuit boards UV exposure causes a rapid setting of the coating, 

Polythiol/acrylate systems are reported to exhibit a reduced oxygen sensitivity, possibly caused by the rapid consumption of oxygen in a chain process of oxidation, hydrogen abstraction from the thiol and reinitiation 201.202) 

Dual functionality coatings differ from dual cure coatings in that they contain functional groups of different kinds. In the first step, partial crosslinking is accomplished through exposure to UV light, in the second step another component, for example an epoxide, is cured thermally through the activation of a latent catalyst. 

Another hybrid system has been proposed for resist applications the simultaneous chain polymerization of N-methylolacrylamide and the acid-catalyzed crosslinking of the resulting polymer with poly(vinyl alcohol) In dual cure plastisols, finally, a solid thermoplastic resin is dispersed in a multifunctional aciyrlate mixture which contains a thermal and a photoinitiator. These plastisols have been proposed for the encapsulation of integrated circuits 

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