Types of Conformal Coating

Selecting the Right Conformal Coating

 

Conformal coating is a specialised polymeric film used to protect Printed Circuit Boards (PCBs) and electronic components against damage due to moisture, dust, chemical and temperature extremes. Additionally, it provides increased dielectric resistance and operational integrity.

With many types of conformal coating to choose from, how do you select the right option for your production line?

It mainly depends on the type of protection required, followed by application method and ease of removal. Below are 6 main types of conformal coatings, each with its distinct advantages and disadvantages.

Traditional Conformal Coatings

Acrylic
Resin
Silicone
Resin
Urethane
Resin

Specialized Conformal Coatings

Epoxy
Resin
Parylene Nano/Thin
Film

Acrylic coatings can be considered basic entry-level protection, because they are economical and protect against a broad-level of contamination, but not best-in-class for any characteristic except possibly dielectric strength. 

Pros Cons
  • Provides general protection
  • Fair elasticity
  • High dielectric strength
  • Fair moisture and abrasion resistance
  • Easily and quickly removed by a variety of solvents
  • Does not protect against solvents and solvent vapors

Silicone conformal coating provides excellent protection in a very wide temperature range and are commonly used in high humidity environments, like outdoor signages. Special formulations are available that can coat LED lights without color shift or reduction of intensity.

Pros Cons
  • Good chemical, moisture and salt spray resistance
  • Very flexible
  • Resilient against vibrational stresses
  • Not abrasion resistant due to its rubbery nature
  • Hard to remove - requires specialized solvents, long soak time, and agitation like from a brush or an ultrasonic bath

Urethane conformal coating is commonly specified for aerospace applications where exposure to fuel vapors is a common concern.

Pros Cons
  • Excellent moisture and chemical resistance
  • Abrasion resistant
  • Solvent resistant
  • Difficult to remove - full removal generally requires specialized solvents, long soak time, and agitation like from a brush or an ultrasonic bath.

Epoxy-based coatings are usually available as two‐part compounds and create a very hard coating. Epoxy coatings are common in potting compounds, which in contrast to conformal coatings, completely covers the electronics in a solid and level layer of material.

Pros Cons
  • Hard coating
  • Very good humidity resistance
  • High abrasion and chemical resistance
  • Non-permeable 
  • Not flexible compared to other coatings
  • Very difficult to remove

Parylene conformal coatings is a unique type of coating applied by vapor phase deposition. Because of the vapor deposition method, parylene coatings can be applied very thin and still provide excellent circuit board protection. However, removal for rework is very difficult, requiring abrasion techniques, and without access to vapor phase deposition equipment, recoating with parylene is impossible.

Pros  Cons
  • Excellent dielectric strength
  • Superior resistance to moisture, solvents and extreme temperatures
  • Very difficult to remove
  • Requires vapor phase deposition equipment

A coating is dissolved in a fluorocarbon‐based carrier solvent and applied with a spray or dip method to create a very thin coat

Pros Cons
  • Provides minimal amount of hydrophobicity (protects against shortage from quick exposures to water)
  • Does not offer as high of surface protection compared to other coating methods

Check out Techspray's conformal coatings here