There are many embedded applications, particularly on the industrial side, where it makes sense to apply a conformal coating. A conformal coating is generally a thin polymeric film, measured in tenths of millimeters, that conforms to the contours of a printed circuit board. Its purpose is to protect the board’s components against moisture, dust, chemicals, and temperature extremes, as well as corrosion, short circuits, and chemical contamination.
In harsh environments, embedded systems, including those produced by WINSYSTEMS, often make use of conformal coatings. Quite often, it’s not a requirement, but it can add an extra layer of reliability and protection.
Another method of ensuring reliability of embedded computers in harsh environments is to employ a sealed enclosure, such as the WINSYSTEMS PPC12-427. The platform is a fanless, 12.1-in. panel PC that’s designed with the latest generation Intel Apollo Lake-I SoC processor. With its IP65 rating, small size, low power, and extended operational temperature, it’s suited for the harsh environments that often occur in the industrial control, transportation, energy, medical, MIL/COTS, and industrial IoT arenas.
When the sealed enclosure like the one used in the PPC12-427 is not practical, a conformal coating is the next best alternative. For maximum protection, combining the two strategies is a very viable option. At the end of the day, you need your system to be reliable enough to handle the environment dictated by its application.
When it comes to the different materials used for conformal coatings, the most popular include acrylic, urethane (polyurethane), silicone, epoxy, and parylene. Like most things in the engineering space, each material has its pluses and minuses, and those tradeoffs must be weighed and analyzed.
- Strengths: Good moisture and fungal resistance, ease of rework, cost effective, and flexible application methods via brush, dip or spray methods
- Weaknesses: limited solvent-resistance and low abrasion resistance
- Strengths: excellent dielectric properties, good moisture resistance, and solvent and abrasion resistance
- Weaknesses: bond-strength can be limited, difficult to repair, and long cure time
- Strengths: stable over wide temperature range (-40°C to +200°C), flexible with dampening and impact protection, and good moisture resistance
- Weaknesses: almost impossible to rework, expensive, difficult to apply
- Strengths: good moisture and fungal resistance, and good abrasion and chemical resistance
- Weakness: poor flexibility, difficult to rework, and expensive
- Strengths: excellent uniformity regardless of part geometry, chemical inertness, and minimal added mass and low outgassing
- Weaknesses: very expensive setup and process, and difficult to rework
At WINSYSTEMS, we try to stay conformal-coating agnostic. Rather than providing an off-the-shelf conformal coating solution, we work with clients individually to select the proper conformal coating for their environment and application. We help develop the conformal coating application and masking drawings for the connectors and features that are needed on the end product. Then we work with third parties that specialize in conformal coatings for the specific types of materials required. Finally, we provide testing after the conformal coatings are applied to ensure that all connectors and test points are masked properly.
A good example of a single-board computer (SBC) that’s a candidate for a conformal coating is the WINSYSTEMS EBC-C413. The EBX-compatible platform offers a rugged design and extended operational temperature range. It’s built with Intel’s Bay Trail E3845 or E3825 microprocessor.
The bottom line is that you should choose the protection method that works best for you, whether it’s a conformal coating, a sealed system, or a combination of the two.