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How to Choose the Best Conformal Coating for Your PCB

a conformal coating engineer making sure there aren't any defects in the coating

Mallory McGuinness | July 21, 2020

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

As electronics perform more complex tasks in medical, automotive, IoT, consumer electronics, and industrial applications, the demand for conformal coatings has increased. These coatings conform to the shape of a PCB’s substrate, offering protection from external elements.

A device failure could lead to dire consequences. Therefore, the choice of circuit board coating material you use is imperative. To choose the best conformal coating, an analysis of the product that is going to receive conformal coating on the PCB, the application process selected, economic costs, and the desired result is in order. However, there are other factors you should consider when you choose a conformal coating.

Things to Consider When Choosing a Conformal Coating

An ideal PCB protective coating has characteristics like low moisture permeability, excellent electrical properties, and will adhere 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

Manufacturing considerations

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

Conformal Coating Consistency

Considering that 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 out. Imperfections in the coating like pinholes or de-wetting will require rework 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 are applied via assembly line, while other coatings, like Parylene, are applied through a batch process. Additionally, 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 at once.  

a printed circuit board experiencing dewetting

Consider What You Need to Protect Against 

There are five conformal coating materials (acrylicepoxy, Parylenepolyurethane, 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 protectionsweat 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 waterproof 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. 

Do You Want Your Device to be Completely Waterproof? 

If you would like your device to be impervious to water, this will influence your decision as well. Be sure not to confuse waterproofing with moisture protection. Most coatings are able to provide adequate moisture protection, provided that they are applied correctly. But if your PCB will be submerged in water while expected to work, that is an entirely different situation.  

To properly waterproof a PCB with conformal coating, you must evaluate how much water exposure the device will be subjected to. Will it have to be protected from an occasional splash or condensation? Or will it be fully submerged? Considering the amount of liquid exposure will allow you to approach the waterproofing production process correctly.

Are You Worried About Warranties?

When waterproofing electronic products, there are often warranties to back up waterproof claims. If you dont 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 waterproof coating manufacturer.  

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 reach out to us for expert coating advice from our engineers.   

At HZO, we know we can meet your standards of excellence with custom solutions from our Spectrum of Protection™, making your device resilient despite any type of challenging environment. Youve 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.   

 

What claims have regarding waterproofing have been made about your product?

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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