Conformal coating-methods-Wet film conformal
Wet film conformal coating measurement
The wet film conformal coating thickness method ensures quality control while the coating is still wet.
Applying too much coating can be expensive. Also, wet film measurements are useful for conformal coatings where the dry film thickness can only be measured destructively or over application of conformal coating could be problematic.
The wet film gauges are applied to the wet conformal coating and the teeth indicate the thickness of the conformal coating. The dry film thickness can then be calculated from the measurement.
Dry film conformal coating thickness measurement
An alternative method to wet film measurement is using a non contact technique using eddy currents. The system works by placing the test head on the surface of the conformal coating, the measurement is almost instantaneous and provides an immediate repeatable result for thickness measurement of conformal coating.
Test coupons are the ideal method for measuring the coating thickness, whether is it spraying or dipping, and can be kept as a physical record of the performance. Apply the coating to the test coupons at the same time as the circuit boards provides a permanent measurement and an accurate guide to the coating thickness.
Thicker coatings or better applied coatings may be required when liquid water is present due to potential microscopic pinhole formation in the coating or when the coating material is too thin on the sharp edges of components due to poor application techniques. This is considered a defect and can be eliminated with appropriate steps and training. These techniques effectively "pot" or "conform" to the components by completely covering them.