Last time, we discussed the general requirements necessary to open a conformal coating facility. Now I will discuss the equipment that is required in order to have a properly operating facility.
A basic conformal coating facility could simply be a well ventilated area, a UV source, and coating. However, for setting up a spray coating facility that can produce high quality results regularly there are several options that will aid the operator and ensure that the best results are achieved. A basic setup could include:
Spray Booth For even, repeat application of the coatings using a spray gun.
Curing Cabinet For storage of drying PCBs after application
UV Inspection For inspection of the fluorescing coating under long wave UV
The spray booth should be primarily designed to extract the fumes efficiently while allowing coating to be applied easily and reliably.
Using a high quality spray gun is a must to give the best coating finishes repeatably over long time periods. Low cost guns do work reasonably well, they wear quicker and produce an inferior finish when compared with high quality guns.
While spraying, a UV light above the PCB aids the operator in visually ensuring good coating coverage. It also ensures that shadowing effects are avoided. A manual or automatic turntable further helps prevent shadowing effects.
After being coated, assemblies should be stored in a cabinet while they are waiting for the coating to cure.
There are four main reasons to use a curing cabinet:
- Extract the air from around the assemblies to aid drying and remove dangerous fumes.
- Ensure that the assembly is held still and coating does not flow
- Make sure the assemblies are not touched to damage the coating
- Prevent any particles in the atmosphere from sticking on the wet coating
UV INSPECTION BOOTH
To properly inspect to various conformal coating standards, the operator needs to use UV lighting. As part of a normal conformal coating process, hand touchup and final inspections need a dark, enclosed area to study the assembly with the UV lighting intensity maximized using a UV-transmitting plastic window in the ceiling. Also, ESD points need to be attached to prevent any ESD issues.