Most spray methods are based on the principle of atomizing the coating into a fine mist that is then directed to the part to be coated. Atomization is accomplished by using compressed air, pressurized volatile solvents, or a high velocity jetstream. With the proper technique, a thin continuous wet layer of coating may be deposited without drips, sags, “curtains,” “orange peel,” or other imperfections.
A skilled spray operator can apply a uniform coating and inspect and
touch up defective areas during the process. In coating substrates,
such as circuit boards, that have discrete components, the desired
thickness can be achieved by spraying from four different directions to
cover both the top and all sides of the components and force the
coating beneath the components. Avoiding pinholes, skips, and voids
should be a major consideration in applying environmental protective
coatings. Turntables, either hand or power rotated, are useful in
orienting the work for directional spraying. Conveyors may be utilized
to move parts past automatic sprayheads, as in fully-mechanized spray
lines. All spray coating should be done in a well-ventilated spray
booth that exhausts the overspray and solvent vapors, preferably to a
fume or solvent trap system. Fumes may be noxious, flammable, and even
toxic after prolonged inhalation.