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Complete Guide to Polyurethane Conformal Coatings for Electronics

a can of polyurethane coating

Mallory McGuinness | June 23, 2020

Conformal coatings are protective films that conform to the topography of PCBAs, improving device reliability. With conformal coating protection, electronic products can dependably run in harsh environments, where they may face humidity, liquids, corrosive substances, and other contaminants that might otherwise hinder performance.

Conformal coatings are composed of polymeric materials, each with distinct characteristics, advantages, and disadvantages. Polyurethane is one such material.

What is Polyurethane Conformal Coating, and How Does it Work?

Urethane conformal coatings work as tough, hard protective coatings that offer excellent resistance to solvents and abrasion.

Polyurethane conformal coatings have the following attributes:

  • Moisture and oil resistant
  • Fungicidal
  • Good flexibility
  • Can be thinned to achieve a chosen viscosity
  • Class F temperature rating (160°C/320°F)

What are Polyurethane Conformal Coating Benefits?

The benefits of polyurethane conformal coatings are evident in areas where there is excessive exposure to chemicals. Urethane conformal coatings provide superior protection from organic solvents, excellent humidity resistance, and exceptional sturdiness and resistance to abrasion. The coatings are tough and resistant to mechanical wear. Polyurethane is also a good option for mitigating the growth of tin whiskers.

a printed circuit board (pcb) being coating in polyurethane

Polyurethane Conformal Coatings Applications

Urethane conformal coatings protect and insulate electronic units and assemblies, such as motors, generators, relays, and transformers.

Applications that entail direct mechanical wear against a coating may benefit from the use of polyurethane conformal coatings, because of the robustness of this protective layer. Other application examples may include the automotive and aerospace industries or environments where coatings need to protect against a myriad of threats (including chemicals, salt sprays, and temperature variations).

With conformal coating protection, electronic products can dependably run in harsh environments.

What Do Polyurethane Conformal Coatings Protect Against?

In applications like these, urethane coatings work as a barrier to air-borne contaminants, such as salt-spray, thermal shock, moisture, and harsh chemical solvents.

The Polyurethane Conformal Coating Process

Polyurethane conformal coating is applied by liquid deposition techniques such as dipping, spraying, and brushing, which can be simpler than other application methods. After the application, the coatings are cured to finalize the coating. The curing process takes anywhere from an hour to several days and requires an additional step during the polyurethane conformal coating process.

Why Choose Polyurethane Conformal Coatings to Protect Your Electronic Devices?

Polyurethane conformal coatings are a suitable choice for many applications, but like every other conformal coating material, it has its disadvantages. The curing process can be timely, and there is a long post-cure time required for the urethane conformal coatings to reach full potential. Additionally, moisture impacts the cure rate and cured properties. There is potential stress to components during temperature cycling, and the coating can yellow with age, which is undesirable. Polyurethane may not be an optimal choice for very moist environments, as it has a higher water absorption rate than some other conformal coatings, like Parylene.

Unlike polyurethane, Parylene conformal coating by HZO does not require curing and ensures that devices, even in mission-critical applications, perform more reliably, for longer. If you’d like to discover more of the advantages of Parylene, contact us today for a custom quote.

Parylene conformal coating by HZO does not require curing and ensures that devices, even in mission-critical applications, perform more reliably, for longer.

Mallory McGuinness

Mallory is an electronics protection evangelist who writes content for HZO. In her free time she is reading non-fiction, and hanging out with her beta fish, King Awesome.

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