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Protecting PCBs: Conformal coatings Vs. encapsulation resins

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Printed circuit boards or PCBs are a critical part of electronics systems that service domestic, industrial, automotive and military devices among others.

PCBs are exposed to various contaminants in different application environments causing damage and impacting system performance. Absorption of atmospheric moisture or electrostatic attraction of dust can cause electrical performance to deteriorate while exposure to corrosive atmospheres or harsh chemicals can cause reduced performance and even complete failure.

In order to ensure continued reliability of these critical devices, it is essential that the PCBs are protected to prevent reduced performance or complete failure. Conformal coatings as well as potting and encapsulation resins are some of the methods used to ensure protection to sensitive electronic equipment.

Potting and encapsulation resins

Offering an extremely high level of protection for PCBs, potting and encapsulating resins provide complete insulation for the unit by encapsulating the entire PCB, combining good electrical properties with excellent mechanical protection.

Mechanical protection can be identified in a number of ways, especially in applications involving prolonged exposure or immersion in harsh chemicals, or those exposed to vibrational, thermal or physical shock.

The mass of the resin surrounding the unit provides a high level of protection, providing a far more substantial covering than that offered by conformal coatings. Potting and encapsulation resins are commonly two-part systems, which when mixed together form a solid, fully cured material with no by-products.

The potting and encapsulation resin-protected PCB can be tested in an appropriate environment for its intended end use. The potting and encapsulation resins can also be tested separately in a number of environments, establishing their specifications and suitability for use.

Conformal coatings

Also utilised to protect PCBs in a variety of applications, conformal coatings ensure optimum performance even in harsh conditions. They are single-part materials applied as thin films, typically ranging from 25-75µm.

Conformal coatings protect by conforming to the contours of the board, providing maximum safeguard with minimal weight or dimensional change to the PCB, a key advantage of conformal coatings over potting and encapsulation resins.

The most common environment that a coating can be subjected to is standard atmospheric conditions wherein initial tests are conducted to evaluate both the electrical and mechanical performance of the cured film on substrates governed by each standard test method.

The surrounding environment can then be altered to assess the performance of the coating under more severe conditions such as salt mist, high humidity, high temperature and thermal changes, either as a gradual rise or decline in temperature or an immediate thermal shock.

After exposure to such environments the coating can then be re-tested for its electrical and mechanical properties, determining its suitability for various applications.

Conformal coatings Vs. encapsulation resins

There are several options available in the market for conformal coatings as well as encapsulation and potting resins. For standard atmospheric conditions, most conformal coatings and potting and encapsulation resins will provide the required level of protection and the final choice will depend on the application processes of the material. However, the choice may be more detailed for harsher environments.

Both conformal coatings and potting and encapsulation resins offer a full range of solutions for protecting PCBs in a variety of different applications with specific applications more applicable for each technology.

While potting and encapsulation resins provide full protection to the device throughout the duration of its use in extreme environments, conformal coatings aid in the ease and speed of processing.

Additionally, most conformal coatings are single part systems, which can be modified to cure rapidly in-line with minimal processing. They also provide a high level of protection through a thin cured film, assisting in the miniaturisation of electronics and reliability of portable devices.

Coatings and resins from the Electrolube range:

  • Acrylic coatings such as Electrolube IPC-CC-830B approved TFA offer good environmental protection with superior clarity and stability following prolonged exposure to UV light
  • Electrolube UL746 approved DCA or environment-friendly non-VOC coating (NVOC) protects against chemicals or high humidity environments where prolonged condensation or periodic immersion in water is likely
  • Potting and encapsulation resins provide superior protection and optimum performance of the device should the environment include greater mechanical stress or prolonged exposure to the extreme environment
  • Silicone resins such as the new SC3001 offer good clarity
  • Optically clear polyurethanes such as Electrolube UR5562 offer greater flexibility over epoxy based systems, causing less stress on delicate components particularly in low temperature environments
  • Polyurethane resins such as Electrolube UR5041 are ideal for marine applications where the device is immersed and continually operating in salt water
  • Epoxy resins such as Electrolube ER2188 are excellent general purpose resins offering cost effective, high level protection for the PCB including flame retardancy to UL94 V-0
  • Epoxy resins offer superior protection in environments involving immersion in harsh chemicals

Electrolube is a division of the HK Wentworth Group and global manufacturer of electro‐chemicals.

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