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Epoxy vs Parylene Conformal Coating

What's Best for Your Project

Epoxy resins (ER), just like any other conformal coating, provides a thin protective film. Coating takes some expertise to apply. If the coating is too thick, problems could include shrinkage, cracking, bubbling or trapped solvent.

Many people consider parylene to be the gold standard of conformal coating owing to its plethora of desirable properties for applications ranging from printed-circuit boards (PCBs) to medical implants. Benefits of parylene conformal coating is that it:

  • Features high optical clarity
  • Offers excellent moisture and dielectric barrier properties
  • Possesses desirable mechanical properties
  • Is chemically and biologically inert
  • Adheres to a wide range of substrates and geometries
  • Remains bubble- and pinhole-free at a coating thickness greater than 0.5 micronsparylene uniformity
  • Boasts conformability and flexibility
  • Penetrates extremely small spaces and crevices
  • Contributes to tin whisker mitigation
  • Withstands the heat of an autoclave

Drawbacks of parylene conformal coating is that it:

  • Carries a higher price tag, generally, than other conformal coatings, which is attributed to higher costs of raw materials, labor, and lot volume
  • Requires an abrasion-based method for removal
  • Has limited throughput

Epoxy Benefits

Offered as a single- or two-part compound, epoxy resin (Type ER) conformal coating is defined by extreme hardness; however, that property is also its biggest drawback. Epoxy resin:

  • Exhibits rugged toughness and durability
  • Allows for ease of application
  • Resists abrasion, humidity, and chemicals
  • Possesses good dielectric and moisture barrier properties
  • Features relatively high glass transition (Tg) temperature

Like all conformal coating, epoxy resin has drawbacks as well. For example, epoxy coating:

  • Presents significant challenges for removal and rework because of its toughness and durability, which puts the coated product at risk of being damaged
  • Experiences shrinkage during polymerization
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