Tips for Choosing the Best Coating for Optimal PCB Performance

By
EN
Emily Newton
on June 23, 2022
Electronic circuit board with electronic components such as chips close up

Printed circuit boards (PCBs) are critical components in everything from laptops to car electronics. Aspects ranging from material properties to design dimensions can all affect PCB performance and influence how well a finished product meets expectations.

However, PCB coatings also have a significant impact on how well the component works in certain conditions or environments and whether it meets or exceeds an expected life span.

How Could a Coating Improve PCB Performance?

PCB coatings are also referred to as conformal coatings. They add a thinly applied layer to a PCB’s surface, helping protect its delicate parts. The specific performance benefits vary based on the type of coating a person selects.

However, conformal coatings are generally chosen to protect the PCB against unwanted elements. These include extreme temperatures, dust, moisture, and abrasion. Due to the extreme thinness of the additional layer, the conformal coating does not cause noticeable changes in the circuit board’s dimensions or weight.

Choosing the most appropriate coating could ensure the PCB continues to work in extreme environments. That’s important since people frequently deploy equipment containing PCBs in remote areas that don’t always have ongoing supervision.

Conformal coating of a pcb via spray technology

Credit: PCB Directory

Know the Characteristics of the Primary Types of PCB Coatings

Knowing how to choose the best PCB coatings starts with identifying the type and strength of safeguards required. No single option can provide the strongest protection against all risks.

PCB designers and manufacturers must consider a product’s end-use and the associated threats that could negatively impact PCB performance. Then, they’ll be in a better position to make informed decisions.

Acrylic

Acrylic conformal coatings are low-cost options that protect against a broad assortment of contaminants but don’t provide best-in-class results. One of their main advantages is the ease of removal, making them suitable when PCBs require rework. However, these PCB coatings do not provide robust chemical resistance.

A report from Grandview Research showed that acrylic coatings dominated the market in 2021. They comprised more than 47% of the overall revenue share within the sector.

Silicone

This type of coating is a popular choice for applications that must endure continual outdoor environments, such as digital signs. That’s because silicone can withstand moisture and salt spray. It’s also a good choice for PCBs that may encounter high temperatures. The coating holds up to temperatures of approximately 250°F.

However, because silicone has a tacky, rubbery feel once cured, it is not an optimal choice when PCBs need excellent abrasion resistance. On the other hand, silicone can act as a shock absorber, and some people choose this PCB coating to dampen vibrations. Another thing to know is that silicone typically adheres well to various substrates without a primer.

Spray coating of a PCB

Credit: EE Times

Urethane

Urethane is a frequently chosen option when excellent PCB performance depends on adequate protection from chemicals or abrasion. These coatings are also typically more economical than some other options.

However, one of the primary disadvantages is the long curing time. It can take up to 30 days to complete. Although people can buy specialized equipment to accelerate the process, some may find the extra expense not worthwhile. That’s especially true if they don’t use urethane coatings often.

Parylene

Parylene coatings provide excellent protection against moisture, solvents, and extreme temperatures. Parylene C, in particular, is often chosen to support PCB performance. That’s partially due to how its low permeability protects components from corrosive substances.

However, people must use a vapor-deposition method to apply it, which means buying specialized equipment. This coating also requires using batch processing.

Epoxy

Epoxy PCB coatings offer excellent protection against mechanical wear. They have a hard consistency once cured and are also good choices when abrasion is a concern.

However, exposure to vibrations or temperature extremes can cause consequences such as cracking and shrinking.

Realize That Correct Application Techniques Align With Better PCB Performance

The link between the appropriate coating and the resultant PCB performance is not only about the type selected. Getting the best outcomes also requires people to apply the correct amount to get the desired benefits. Failing to coat the surfaces thoroughly enough could mean the PCB does not receive the intended protective advantages.

However, applying the coating thicker than intended could cause it to bubble or wrinkle. A market research report about conformal coatings in the automotive industry also mentioned PCB miniaturization as a significant factor shaping the sector. It showed a decrease in the PCB coating volume per component due to overall reductions in board sizes.

Liquid conformal coatings get applied through brushing, spraying, or dipping. Brushing is often one of the most time-consuming methods, although it also offers excellent precision. In contrast, spraying can cover a comparatively larger surface area. Some people also automate dip applications for better consistency.

Take a Sustainable View of PCB Performance and Conformal Coatings

People are becoming more concerned about recycling their electronics so the items don’t end up in landfills. Making progress in this area could cut down on society’s e-waste issue, but there’s still a long way to go. Statistics showed that only 17.4% of 2019’s e-waste got recycled.

However, an inventor created the first fully recyclable PCB, which includes flax as one of its key components. Recycling is only one example of a sustainable action. Many PCB coating manufacturers have started offering eco-friendly options to consider.

In 2020, Dow introduced a silicone option that reduces energy usage by using an energy-efficient UV-curing process. The product also has a low enough viscosity for people to apply it via spraying, which further reduces overall production time.

An option that arrived on the market more recently is a solvent-free, bio-based conformal coating with 75% of its organic content taken from renewable sources. It also has a secondary chemical-curing mechanism that makes the coating harden fully in just a day, even on shadowed parts of the PCB.

The availability of eco-friendly conformal coatings gives people more possibilities for pursuing sustainability during PCB production. The fact that a product is kinder to the Earth than alternatives does not automatically make it the best choice for promoting reliable PCB performance.

However, decision-makers in the industry should at least research what’s available and see if the sustainable offerings render the other attributes needed to make using the coating worthwhile.

Stay Abreast of Industry Developments

Printed circuit boards play a critical and ongoing role in today’s high-tech society. People should expect engineers and manufacturers to keep investigating new formulas and methods that could forever change conformal coating usage.

As a case in point, researchers recently developed a copper conformal coating that covers all exposed surfaces of a component. They found that this approach eliminated the need to use a heat sink or a thermal interface material in devices.

Tarek Gebrael is a doctoral student in mechanical engineering and the lead author of a study on this innovation. He explained that lab tests indicated a 740% increase in power per unit volume and allowed the devices using this approach to be dramatically smaller than those with heat sinks. He also noted that the coating allows stacking more PCBs within the same volume. That could be especially useful as today’s electronics get both smaller and more advanced.

Maintaining an awareness of developments like these will help people continue to make the most appropriate decisions about PCB coatings. This knowledge should also encourage them to think outside the box and consider how pioneering approaches like the one described here could lead to device improvements.

Integrated circuit with epoxy glop-top coating over it

Careful PCB Coating Choices Support High Performance

The manufacture and design of printed circuit boards is a precise process, and conformal coating application choices are vital. When delicate components are well-protected with the best coatings, the parts are more likely to last at least through their expected life spans.

Additionally, reliable performance often has favorable effects on consumer perception, bolstering a company’s reputation. Being thoughtful and considering a product’s real-world use will help people choose well when surveying the available coatings for their PCBs.

 

Emily Newton, Revolutionized

Emily Newton is an industrial journalist with over four years of experience. As Editor-in-Chief of Revolutionized, she regularly covers this industry and how technology contributes to its evolution.

 

*This article is the work of the guest author shown above. The guest author is solely responsible for the accuracy and the legality of their content. The content of the article and the views expressed therein are solely those of this author and do not reflect the views of Matmatch or of any present or past employers, academic institutions, professional societies, or organizations the author is currently or was previously affiliated with.

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