PCB Conformal Coating Features Fast Tack-Free Cure

Moisture-curing silicone conformal coatings are suited as protective coatings for sensitive board components in demanding environments, but electronic manufacturers avoid using silicone coatings in electronic packaging due to their long cure schedule that does not allow rapid assembly. Master Bond has developed a rapid cure to tack-free, ready-to-use silicone conformal coating for printed circuit boards called Master Sil 773.

It is formulated to provide excellent protection to electronic circuitry in high humidity environments as well as upon exposure to shock and vibration. It cures quickly at ambient temperatures to a highly flexible, transparent, low hardness silicone coating. Adhesion to critical board components is outstanding. A most useful characteristic of this product is that it maintains its low modulus over the remarkably wide temperature range of -65 degrees Celsius to in excess of +200 degrees Celsius. This one part, ultra low viscosity silicone adhesive is ideal for application as a low stress coating affording optimal protection to sensitive board components in demanding environments.

Master Sil 773 is 100 percent reactive and cures by moisture. If needed, a UV tracer dye is also available with this system. The Master Sil 773 silicone conformal coating can be applied by dipping, spraying or brushing. It is suitable for either manual or automated coating techniques as its tack free time is less than five minutes. These cured silicone conformal coatings are very easy to repair. No solvents are required either for applying the material or repair procedures. Its electrical performance is exceptional with volume resistivity of 1 x 10¹⁴ ohm-cm, dielectric strength of 25 KV/mm, a dielectric constant of 3.3, 60Hz and a dissipation factor of 1 x 10^-4.