What are the benefits and drawbacks of conformal coating for electronic components?

In addition to the conformal coating materials mentioned in the article, there is Fluoropolymer Nano-Coating. It is an ultra-thin film composed of fluorocarbons. This material offers good resistance to mold and high temperatures, along with excellent dielectric resistance and low process costs. However, it shows low resistance to abrasion and chemicals, and the tooling setup cost for this material is pretty high. Connect with me for more electronics updates!

In my experience at CERN, it is very important to consider the mechanical and RF characteristics of the components and circuit to be coated before choosing the right coating. All the coatings mentioned have their thermal expansion curve, surface tension, and volume expansion under thermal, radiation, and chemical exposures. Additionally, they have different dielectric permeabilities and loss tangents, making the choice very important when dealing with RF circuits. Another important factor in selection is the tendency of the coating to form bubbles and trap air, which would dramatically lower the dielectric breakage voltage, and potentially trap impurities from the environment that, in contact with the board, may cause corrosion.

Conformal coating for electronic components offers several benefits, including protection against environmental factors, moisture, and contaminants, enhancing reliability and longevity. It provides insulation, preventing short circuits and improving resistance to corrosion. However, drawbacks include the potential for masking defects during manufacturing, making inspections challenging. Coating thickness variations can affect component tolerances, impacting performance. Additionally, rework and repair become more intricate with conformal coatings in place.

Conformal coatings, are avaialble in application specific wider range. In Electronics primarily it can help in Thermal isolation, environmental protection, vibration absorption. For each property different mix of chemical compounds are available. The only con side is that applying conformal coatings need certain set up of instruments and need little skilled assistance in doing so.

Urethane and similar varieties may help to mitigate tin whisker growth. Otherwise it keep dust and salty fingerprints out from components that can harm them in a long runs.

An often not-so-discussed, and peculiar application of conformal coatings, lies in the protection of exposed bonding wires. This may seem rare in the consumer industry, but is a common requirement in state-of-the-art research laboratories and space agencies. Here coatings can provide also the benefit of incapsulation of ICs and exposed bonding wires, preventing failures from accidental mechanical damage and vibration, or shortage due to the accumulation of ionic-charged impurities on the board, while limiting corrosion of the aluminum wherever the bonding wire is made of such metal.

Conformal coatings can greatly reduce risk of premature failures in computerized equipment exposed to harsh environments. In many factories and automotive shops where there can be a lot of metallic dust for example. Most of these machines do not require high performance heat generating computer circuitry. So the benefits can greatly outweigh the cost.

Some electronic components are non-compliant with coating material. Conformity coating material can also affect the dependability of your product.

The most evident drawback of conformal coatings not mentioned is the change of the dielectric cross-section of the PCB. Although not important for boards running concentrated circuits and at low frequencies, it becomes critical in RF circuitry where usually PCBs show high-frequency tracks on the top layer, exposed without cover. This is done to avoid having a cover with a nonuniform cross-section which would change the impedance of RF traces and cause disruption of the high-frequency signals. In this case, a controlled vapor deposition of the coating, if needed, must be chosen to be able to carefully control the thickness of the coating to preserve the signal integrity of RF traces.

Added cost and process is indeed a drawback for non critical application and may be skipped, especially in event of shortage impacting more cost and delay. Clear coating make easy for inspection.

There are many ways to apply conformal coating, including brush coating, manual or automated spraying, coating dipping, selective coating by machine, and chemical vapor deposition. Each method has its own pros and cons, and the choice of the most suitable one depends directly on the desired volume of PCBs and the production yield. In a traditional conformal coating inspection, an inspector will manually inspect the conformal coatings using a lamp. However, a recent automated optical inspection (AOI) has begun to replace manual inspection. This system can be camera or scanner-based, hence the technology can be matched to the project.

Never apply conformal coating to untested pcb's. Probing boards while troubleshooting is very difficult and can produce false readings.

Conformal coatings should be applied only to fully electrical-tested boards as the electrical testing can become difficult or completely unfeasible after the coating is applied. The coating can be applied on boards that are not completely tested only if there are stable enough states of the electronics to demonstrate in a repeatable manner the working of the applied coating in a testing environment. The testing environments can be environmental chambers, water chambers (for submersible electronics), or chemical baths for industries where defenses against chemicals are needed (i.e. automotive to avoid damage from engine oil, transmission oil, and brake/clutch fluids).

Pcb must be washed and spotlessly clean. No direct handling by exposed skin or hand until after the coating applications. Salt is powerful reactant that harm pcb and components. It can leave fingerprints for Sherlock Holmes to jail you!!!

Refer to IPC CC-830 revision B and UL746E for conformal coating standards. IPC CC-830 revision B is a conformal coating qualification standard primarily used by board fabricators, OEM design engineers, and coatings suppliers. UL746E refers to the Underwriters Laboratories (UL) tests and certifications, which are commonly required for consumer goods.

I’ve used conformal coatings on a myriad of PCB applications where environmental conditions include high humidity or extremely high altitude operating environments. One drawback I’ve observed is the higher operating temps of conformal coated boards. Another is the increased complexity of performing SMT repairs.

An opportunity to consider, wherever the concealing of electronics is also needed, would be to choose potting instead of conformal coating. in this case, the board is completely submerged in a solution that once cured will be turned solid. The solution can be inert, hence not changing the performance of the board, or thermally conductive, to better remove heat from components and increase the thermal mass of the electronic system without paying for additional PCB surface.