Curing Methods of Conformal Coatings

Curing Conformal Coatings

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Curing requires conformal coating to obtain complete hardness in order to achieve optimum electrical and mechanical properties for maximum performance protection of the circuit assembly. Depending on their type, thickness and curing method, conformal coatings can cure between seconds to days.

There are 4 methods of curing conformal coatings:

Evaporative Cure
The solvent or water-based carrier evaporates and the coating resin is left behind. It will take days to fully cure. Although solvents are easy to process, provide consistent coverage and have fast cure times, they are often flammable. Hence, sufficient ventilation and fume extraction methods are required. In contrast, water can eliminate flammability concern, but they have longer cure times and are very sensitive to ambient humidity.
Moisture Cure
The resin, which is mainly found in silicone and some urethane coatings, will react with ambient moisture to form the protective polymer coating. This method can also be combined with Evaporative Cure, where moisture reacts with resin to initiate final curing, as the solvent carrier evaporates. It will take days to fully cure.
UV Cure
With 100% solid and no carrier solvents, coatings cured by ultraviolet light offer very fast production throughputs. Since UV is a line-of-sight lightsource, secondary curing under components and shadow areas is necessary. Cure time is instantaneous when exposed to UV, but shadowed areas may take days to fully cure.
Heat Cure
Often used as a secondary cure if one curing method is insufficient to obtain the required cure properties. Although the added heat helps to speed up the curing process, the thermal sensitivity of the PCB and electronic components must still be taken into account.

In cases where printed circuit boards need repair or rework, conformal coatings must be removed. Find out more information about coatings removal here.