How to Choose the Best Conformal Coating for Your PCB

Mallory McGuinness | July 21, 2020

Coating Selection: How to Decide Which Coating is Best for Your PCB

As electronics perform more complex tasks in numerous applications, the demand for conformal coatings, films that conform to the shape of a PCBA, has increased.

These coatings improve reliability; therefore, choosing the most suitable circuit board coating material is imperative. Variables affecting your decision include the product receiving conformal coating on the PCB, the selected application process, economic costs, and the desired result. However, these are only some factors you should consider when choosing a conformal coating.

Read a comparison between conformal coating and potting

Things to Consider When Choosing a Conformal Coating

An ideal PCB protective coating has low moisture permeability, excellent electrical properties, and adheres well to components. Along with these qualities, conformal coating products must meet additional engineering and manufacturing requirements.

Conformal Coating Engineering Considerations

Engineering requirements common to conformal coatings include:

• Low moisture vapor transmission rate
• Low water absorption
• Corrosion protection
• Good electrical properties, such as dielectric constant, insulation resistance, dissipation factor, and dielectric breakdown voltage
• Low outgassing
• Minimal coating defects

Manufacturing considerations

Naturally, manufacturers have different requirements, but some common desired attributes are listed below.

Learn how HZO integrates into your manufacturing process 

Conformal Coating Consistency

Since device coating provides critical protection, a coating application method that produces consistent protection with minimal defects is a quality that manufacturers and device designers should seek. Imperfections in the coating, like pinholes or de-wetting, may require coating removal and should be avoided.

Conformal Coating Repeatability

When considering which conformal coating material to use, be sure to use a material that is applied with a highly repeatable process that can deliver the kind of consistency you need time and again. Remember that the repeatability of some manual application methods will be contingent upon the skill and experience of the operator.  

Conformal Coating Scale

To meet mass production needs, manufacturers will also want to consider scalability. Some coatings, such as epoxy or urethane are applied via an assembly line, while others, like Parylene coating, are applied through a batch process. The type of equipment used can improve throughput. For example, at HZO, we have capital equipment with large, optimized coating chambers that can house multiple substrates simultaneously.  

Consider What You Need to Protect Against

There are five conformal coating materials (acrylic, epoxy, Parylene, polyurethane, and silicone), and each one has distinct characteristics, pros, and cons. The elements your electronics will be most frequently exposed to in the operating environment will invariably affect your decision. 

Conformal coating attributes to consider include salt protection, chemical protection, UV protection, and heat protection (can perform well in excessive heat or fluctuating temperatures).  

Conformal Coating Moisture Protection 

Liquid protection coatings are a valuable asset in many instances, as they provide splash protection, sweat protection, and conformal coating condensation protection. Some conformal coatings, such as Parylene, go as far as to provide liquid submersion protection, even for extended periods of time. In many cases, good electronic liquid protection is a necessity as devices will be subjected to liquid exposure, coming into contact with sweat, oils, rain, and saltwater. Additionally, moisture can penetrate the surface of some conformal coatings in humid environments, leading to damage, so you may want to choose a material that offers good humidity protection.  

Marketing considerations for your product 

In addition to manufacturing and engineering considerations, marketing concerns may factor into your evaluation. What claims have been made about your product?  

Which IPX Rating Do You Need?

IP ratings, or ingress protection rating, is a system created to systemize levels of protection from liquid or solid ingress. An IP rating is represented by the letter IP, followed by two digits. The first digit signifies how protected a device is from the intrusion of solid particles. The second digit represents the level of liquid protection a device has.  

Each standard represents an operating environment that a device should be able to run reliably in. So, for example, an IP rating of IP68 Enclosures will be “dust tight” and protected against submersion in water. 

 In general, high IP ratings afford more protection, meaning the device will be more reliable. That being said, highly rated electronic products are more sought out. If you need to meet one of these standardized levels of liquid resistance, you should choose a conformal coating that can reliably provide that type of protection. 

Are You Worried About Warranties?

When waterproofing electronic products, there are often warranties to back up waterproof claims. If you don‘t choose the correct waterproof material for electronics, and your product fails from a short circuit or corrosion, you will have to pay out numerous warranty claims. Therefore, selecting a reliable waterproof manufacturing process is critical. Select the right conformal coating material, and choose the best coating supplier.  

Contact HZO for Expert Coating Advice

As you can see, choosing the best conformal coating for your application is a complex decision with many variables. We invite you to contact us for expert coating advice from our engineers.   

At HZO, we know we can meet your standards of excellence with our coatings, making your device resilient despite any challenging environment. You‘ve got nothing to lose when you ask for a no-obligation quote, except for time spent wondering how to provide the reliability your device needs. Contact us today.