Wondering if your build could benefit from conformal coating? We’re often asked to explain the benefits to this process. But first, a refresher: conformal coating is the process of applying a thin layer of liquid, conforming material to a Printed Circuit Board Assembly (PCBA) to protect circuits and components from external and environmental factors.
In today’s environment, conformal coatings are being used more frequently due to minimization and the increased use of electronics in harsh environments. Oftentimes, they’re being used on products that didn’t previously require conformal coating. According to market research, the conformal coating industry is projected to be a $16 billion dollar industry by 2027, growing nearly $1 billion per year. The reasons for this exponential growth are the benefits provided by this added cost.
What Are The Pros To Conformal Coating?
- Water Protection
- Humidity Protection
- Improved Insulation
- Corrosion Resistance
- Mechanical Support and Shock Absorption
- Thermal Stability
- Foreign Object Debris (FOD) Protection
- Intellectual Property (IP) Protection
Water on your PCBA during operation will certainly lead to several issues, to put it lightly. If your product will be exposed to water regularly in its operational environment, it’s beneficial to provide an extra layer of protection. Water can create short circuits during operation, permanently damaging those assemblies that took so much time and effort to engineer, purchase, manufacture, and get into the hands of the end user.
Beyond the obvious water element, conformal coating can help you save money on the final assembly. For example, if your product needs a completely water-proof or water resistant enclosure, we can apply a thin conformal coating to the assembly – alleviating the need for the final assembly to be sealed extremely tight, reducing the required labor and parts costs. Further still, you may not want your product sealed up so tight as it makes it more difficult for the end user to replace batteries or operate the product. In this scenario, a thin coating can protect the assembly without increasing end-user frustration.
While this may sound redundant, high humidity environments pose their own threat to a working electrical assembly. Conformal coatings are specifically designed to prevent moisture from entering the board’s circuitry, while being breathable enough to allow moisture that has already penetrated the assembly to escape. This is beneficial when factors like corrosion and high MSL (Moisture Sensitivity Level) parts are considered. Any additional moisture in the assembly can cause it to fail, seemingly out of nowhere.
When talking about high-reliability or long-term products, this protection proves even more crucial. Due to minimization, fine pitch parts are becoming increasingly necessary. Especially when dealing with pitches under 1mm, dendritic growth is now a big concern – the three things required for these nasty, microscopic, metal growths are moisture, electrical current, and time. Without any one of the three, they cannot form. So, by introducing a moisture barrier, the product can effectively be sealed from a disastrous reliability failure.
Is conductor spacing an issue? Is there too much interference from nearby conductors? Conformal coating can help reduce your conductor spacing, allowing an assembly to get smaller without losing electrical quality. While some coatings, like silicone, offer greater insulation resistance, all conformal coatings offer some level of insulation by design.
With the improved insulation, the assembly gains some extra protection from typical electrical issues like arching and the ever-invisible ESD violation. While the insulation provided by coating is limited, they do help prevent minor issues from occurring. It’s important to note that Bottom Terminated Components (BTCs) are typically not protected or affected by the added insulation due the viscosity of the liquid when applied, but can be protected if specialized conformal coating, like thin-film nano coatings.
Corrosion of the circuits, components, and solder joints on an assembly can occur rapidly depending on the environment the build is used in. Chemicals, salt spray, and standard oxidation of metals can cause field failures if left exposed. To combat these harsher environments, urethane-based coatings can provide excellent chemical resistance. Even the harshest of chemicals have difficulty permeating the protective layer of conformal and can prevent deterioration or outright destruction of the circuit.
Salt spray from ocean environments and good old-fashioned oxidation can be prevented with a simple layer of protection. By protecting the metals on the PCBA from oxygen and moisture, no chemical reaction can take place, and the assembly will be able to survive much longer in the field.
Since an additional layer of material is being applied to the assembly and conforming to the shape of every component on the assembly, mechanical support is provided to the components, and subsequently, the circuits. Acrylic coatings are often used as a cost-effective mechanical support, as it cures hard and helps hold every component in place. Imagine a free-standing basketball hoop with water in the base. It’s designed to be stable enough exactly this way, and doesn’t require additional support. Now imagine dumping a bucket of concrete over the base and around the edges. Which one would hold if someone hung onto the rim?
To similar effect, silicone based conformal coatings provide excellent shock and vibration absorption. The naturally rubbery and flexible texture offers excellent support for heavily vibrating applications, like motors on vehicles and pumps. Over time, boards without vibration protection will inevitably have the solder joints crack. While many of these cracks are visible, they can also be microscopic, causing intermittent failures for no apparent reason.
Most active components have an ideal operating temperature, and many have a temperature range in which they cease functioning. While this is not a major concern for a wide variety of applications, those products being used in an outdoor environment may have to operate in conditions from Alaskan winters to Las Vegan summers. In order to stabilize operation temperatures, silicone coatings can be used to offer thermal insulation. As stated earlier, these coatings are designed to be breathable, so heat can still escape as intended, but the external temperatures do not as heavily affect operation and the assembly can perform consistently, regardless of environment.
Metal shavings, dirt, or even that sticky cheese dust from a technician’s favorite snack can cause contamination and field failure. Depending on how well sealed the final unit is and the intended environment for the end-user, this is often overlooked. If the assembly is used in a machine shop or in a windy desert, FOD can find its way onto the board and cause a critical short across several leads of the components. While this may not be the most compelling or likely reason to use conformal coating, it should be considered for your product and its use.
While potting typically beats out conformal coating when it comes to protecting the IP of your hardware, it can be very expensive and may cause more issues than it solves. Due to their difficult-to-remove nature, many types of conformal coating are now being offered in opaque, black coloring in order to shield part markings from prying eyes. Furthermore, epoxy-based coatings are emerging as an inexpensive alternative to potting compounds that don’t increase the footprint of the assembly by much, allowing for minimization and IP protection to co-exist.
To be fair, the information we’ve provided so far makes this process sound like a no-brainer. Why wouldn’t you coat your boards to increase longevity, reliability, and prevent critical failures in the field? Unfortunately, it isn’t all sunshine and rainbows. Conformal coating does have its drawbacks. You can read our blog post on the cons and costs to conformal coating. Or, contact us and we can tell you!