Acrylic resin coating is intended for use where excellent electrical properties are required for a general purpose coating. This type of coating is intended to be used as a brush, spray, or dip-coat application on glass or paper epoxy laminates.

Epoxy resin coating is intended for use where the best electrical properties are required for a general purpose coating. This type of coating is intended to be used as a brush, spray, or dip-coat application on glass or paper epoxy laminates.

Silicone resin coating is intended where excellent dielectric and high arc resistance properties are required.

Polyurethane resin coating is intended for use where good resistance to moisture and abrasion is required.

Paraxylylene coatings are vacuum deposited polymers controlled by a proprietary patent (see 1.2). They may be applied in extremely thin films on printed circuit boards having closely packed units.

These coatings are normally useful at temperatures up to 125°C (200°C for type SR), but the useful life of the deposited coating can be extended by reducing the operating temperature. The effect of a humid environment is to reduce the useful life.

The selection of coating should be such that the curing process shall have no harmful effects on the parts or materials coated. Coatings covered by this specification are not suitable for use on boards fabricated from types GP, GR, GT, or GX (polytetrafluoroethylene resin) laminates in accordance with MIL-P-13949 or from FEP-Fluorocarbon material of MIL-P-27538.

The typical Q for uncoated type GF laminate at frequencies of 1, 50, and 100 megahertz (MHz) are 60, 80, and 85, respectively. It should be noted that when boards are coated more than 0.0020-inch thickness, the Q factor begins to drop rapidly; coating thickness in range of 0.001- to 0.002-inch range gives maximum protection of the electrical qualities of the circuit.