CONFORMAL COATINGS

3-2 CAUTION THIS SECTION IS NOT, IN ANY WAY, TO BE USED BY YOU AS AUTHORIZATION TO ATTEMPT THESE TYPES OF REPAIRS WITHOUT OFFICIAL 2M CERTIFICATION. In the following sections, you will study the general procedures used in the repair, removal, and replacement of specific types of electronic components. By studying these procedures, you will become familiar with some of the more common types of repair work. Before repair work can be performed on a miniature or microminiature assembly, the technician must consider the type of specialized coating that usually covers the assembly. These coatings are referred to as CONFORMAL COATINGS. CONFORMAL COATINGS Conformal coatings are protective material applied to electronic assemblies to prevent damage from corrosion, moisture, and stress. These coatings include epoxy, parylene, silicone, polyurethane, varnish, and lacquer. Coatings are applied in a liquid form; when dry, they exhibit characteristics that improve reliability. These characteristics are: · Heat conductivity to carry heat away from components · Hardness and strength to support and protect components · Low moisture absorption · Electrical insulation Conformal Coating Removal Because of the characteristics that conformal coatings exhibit, they must be removed before any work can be done on printed circuit boards. The coating must be removed from all lead and pad/eyelet areas of the component. It should also be removed to or below the widest point of the component body. Complete removal of the coating from the board is not done. Methods of coating removal are thermal, mechanical, and chemical. The method of removal depends on the type of coating used. Table 3-1 shows suggested methods of removal of some types. Note that most of the methods are variations of mechanical removal.