Ensure that the coating material in the container has been agitated thoroughly and has been allowed to stand for at least 2 hours for all the air bubbles to disperse.
Polyurethane Thinners (PTH) should be used to keep the PUC coating at a suitable viscosity for dipping (150- 300mPa s @ 20°C). PTH is added periodically as the solvent evaporates. The viscosity should be checked using a viscosity meter or “flow cup”.
The board assemblies should be immersed in the PUC dipping tank in the vertical position, or at an angle as close to the vertical as possible. Connectors should not be immersed in the liquid unless they are very carefully masked. Electrolube Peelable Coating Masks (PCM/PCS) are ideal for this application.
Leave submerged for approximately 10 seconds until the air bubbles have dispersed. The board or boards should then be withdrawn slowly (1 to 2s/mm) so that an even film covers the surface. After withdrawing, the boards should be left to drain over the tank or drip tray until the majority of residual coating has left the surface.
After the draining operation is complete, the boards should be placed in an air-circulating drying cabinet and left to dry.
Ensure that the coating material has been agitated thoroughly and has been allowed to settle for at least 2 hours. The coating should be kept at ambient temperature.
When the brushing operation is complete the boards should be placed in an air-circulating drying cabinet and left to dry.
PUC contains a UV trace, which allows inspection of the PCB after coating to ensure complete and even coverage. The stronger the reflected UV light, the thicker the coating layer is. UV light in the region of 375nm should be used for inspection.