In order to protect your PCB or printed circuit board effectively, you will need to choose the right conformal coating. This polymeric film shields your PCB from environmental conditions and corrosion, and depending on your device, conformal coating accounts for salt, chemical, UV, and heat protection.
Conformal coatings should also meet the basic engineering and manufacturing requirements such as low water absorption, corrosion resistance, low outgassing, and insulation resistance.
It’s important to choose the right conformal coating based on your operating environment, material needs, and the processing capabilities of your electronic components.
- Does your PCB need protection against dust and electric surges?
- Do you need to protect against fuel vapors, shocks, and road salts?
- How thin or thick does the film need to be?
- What kind of temperatures will your component be exposed to?
- Are you operating in places of high humidity or with corrosive gasses?
- Does your conformal coating need to be waterproof or have standard basic moisture protection?
Furthermore, you should look at the strengths and weaknesses of a conformal coating to determine if it’s the best fit for your PCB. You may want to also consider the costs of the coating process and if there is a warranty in place if your device fails or has a short circuit unexpectedly.
6 Types of Conformal Coating for PCBs
Each type of conformal coating has its strengths and weaknesses, and they serve specific needs. Let’s take a look at the 6 different types of conformal coating for PCBs and how they protect electronic components.
This coating is the most popular form due to its easy application and removal as well as the low cost. Acrylic works for mild environments, such as exposure to dust, fungus, humidity, and salt spray. Acrylic also doesn’t shrink during the curing process. However, this conformal coating struggles in harsh environments and high temperatures, and it doesn’t have chemical resistance.
Polyurethane is similar to acrylic as far as protection except it has chemical resistance and abrasion resistance, and it provides strong adhesion to low temperatures. The one disadvantage of polyurethane is its longer curing time.
In contrast to acrylic, silicone is resistant to high temperatures and chemicals. It has a low modulus, making it an ideal conformal coating for surface mount devices or electronic components that need harsh thermal recycling. Silicone is also resistant to humidity and corrosion. However, this conformal coating does not protect from oils and solvents, and it can be cost-prohibitive. Silicone can also be difficult to remove, and it is recommended to do localized repairs only.
Epoxy conformal coating has the best protection in comparison to silicone, polyurethane, and acrylic. It has moisture, abrasion, humidity, and chemical resistance, and it is durable in harsh environments. Much like silicone, however, it can be difficult to remove, and it requires a soldering iron for repairs. A big disadvantage is that epoxy can shrink in the curing process
5. UV Cure
UV cure coatings are unmatched in terms of curing time, as their materials only take seconds to cure. Therefore, this coating is ideal for large-volume projects. The downside to this conformal coating is the high costs involved, which can include curing lamps, spray equipment, and radiometers.
If you are needing homogeneous coating, maximum coverage, and extreme temperature resistance, parylene is the conformal coating for you. Parylene is processed through a chemical vapor deposition to where it forms a powder. This deposition method requires special equipment. It is known for providing superior electrical insulation, high strength, and durability. However, parylene coating is not ideal for long-term outdoor exposure, and it can be hard to remove.
Choose Parylene for Your PCB
Despite the cons of using parylene conformal coating, this type has the most dependability and the best protection for several types of devices across various industries, such as military, aerospace, medical, and high-risk electronics.