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46 SMT007 MAGAZINE I OCTOBER 2021 Feature Article by Zsolt Pulai HZO, INC. Printed circuit boards (PCBs) are marvels of science and one of the most disruptive in- novations of the last 100 years. Since incep- tion, they have undergone numerous alter- ations, improvements, and transformations with the most profound being driven by the miniaturization of electronics. PCB manufac- turers are being pushed to create smaller and more densely packed boards with increased electronic capabilities. As amazing as they are, their Achilles heel is contamination. In this ar- ticle, we will review the history and applica- tions for thin-film conformal coatings, and in- troduce a new service for conformal coating application, potentially adding coating capa- bility without adding capital investment. Background Sensitive circuitry is affected by harsh envi- ronments. Extreme temperatures, dust, dirt, chemical vapors, and moisture from humidity, Perfecting the Application of Conformal Coatings Without a Capital Investment rain, and snow can have a detrimental effect on PCB health, thereby putting their end prod- ucts at risk of seizing and performance break- downs. in-film conformal coatings have a solid position as the protective coating of choice for protecting PCBs from external factors in oper- ating environments. ey provide a protective barrier or film, layered over the critical sub- strates. When applied accurately, conformal coatings prevent sources of moisture, vapors, and other contaminants from damaging or cor- roding interior circuitry. ere are five types of conformal coating available on the market today: parylene, acryl- ic, silicone, polyurethane, and epoxy. ey each possess a unique set of characteristics and properties. Of these, parylene is oen con- sidered the protective coating of choice for a PCB's challenging applications. Research chemist Michael Szwarc isolated the parylene polymer series in the late 1940s at the University of Manchester, England. He dis- covered the polymer as one of the thermal de-