A Fluorochemical Coating Material for the Protection of Electronic Circuits Available to Purchase

There are many different types of protective coating available to the circuit manufacturer. Most are covered by United States Military Specification MIL‐I‐46058 and by British Standard Specification 5917 under such headings as acrylic, urethane, epoxide, silicone and paraxylylene. Whilst each of these coatings is effective for certain applications, all have limitations. Acrylics are easily applied but may have low resistance to abrasion and certain organic solvents. Urethanes may be applied only to very clean surfaces and usually have long cure times. Epoxides are strong with good abrasion resistance but exhibit high shrinkage and are very difficult to remove. Silicones have good electrical properties and temperature resistance but generally have poor adhesion to unprimed surfaces. Paraxylylene coatings have excellent abrasion resistance but are almost impossible to remove and expensive to apply (needing special equipment and the payment of royalties). This paper describes a new type of coating based upon fluoroacrylic polymers, developed in response to a US Mantech programme generated by Wright‐Patterson Air Force Base, which meets all the requirements of US MIL‐I‐46058 and is the only fluorocarbon coating included in the Qualified Products List for this specification.