In aerospace and military missions, many important functions rely on printed circuit boards (PCBs) to provide electricity. A malfunctioning PCB can jeopardize an entire flight, so it is important to make sure the PCB can withstand harsh situations. Environmental exposure can lead to issues such as corrosion, so PCBs are manufactured with a conformal coating to protect the exposed components on the surface of the board. A conformal coating is a thin, clear polymeric film that coats the board’s surface and ultimately ensures a longer working lifespan. Conformal coatings are used across many fields, but different environments demand different forms of protection. For this reason, it is important to make sure the correct material is chosen for the coating.
Most conformal coatings are made from solvent-based materials, for example acrylic, polyurethane, or silicone. Each material has its own beneficial properties dependent on its chemical composition, so each material has an ideal operating environment. Some significant environmental considerations include exposure to liquids, humidity, and extreme temperatures. One good option is an acrylic coating because it is inexpensive and easy to apply or remove. These coatings can withstand a large range of temperatures and exposure to humidity, however they are less durable than other options. Polyurethane coatings provide better protection from chemical exposure and low temperatures. A concern with the cold is that the coating may become rigid, but polyurethane remains flexible.
For more specific applications, using a hybrid coating can ensure protection from a greater range of environmental exposures. At Purchasing Efficiency we supply a selection of hybrid coatings manufactured by Electrolube. Electrolube products in the SCC3 range are polyurethane base resins modified with silicone. This makes these coating materials ideal for both high and low temperatures because of the resin without sacrificing the beneficial properties of solvent-based coatings. These complex materials are ideal for missions with an abundance of exposure to chemicals and extreme temperatures. Electrolube additionally manufactures coatings in the following categories: silicone, UV, water-based, and 2K coatings.
Making sure a particular conformal coating is adequate requires proper preparation and testing. First, it is important that the operator cures the coating after it has been applied to the PCB. Curing is the process of optimizing the chemical properties of the coating by exposing it to certain conditions. Common types of cures include heat cures for solvent based coatings, UV cures for immediate use, and moisture coating for coatings that operate in humid environments. An example of the benefits of curing is Electrolube’s hybrid DCA coating that becomes more chemically resistant when heat cured.
Military and aerospace applications of conformal coatings demand high standards of performance, so the coatings must withstand a series of tests and specifications, such as MIL-I-46058C. This standard requires laboratory testing before use. The main considerations of any conformal coating test are strengths in moisture resistance, electrical properties, and adhesion to PCB. Adhesion is tested through a cross-hatch test, where squares are cut into the surface and the tester uses tape to see if the squares will come off. Corrosive gas testing involves exposing PCBs to a mixed gas environment combining hydrogen sulfide and sulfur dioxide BS EN 60068-2-60,method 1. Humidity testing checks for corrosion, and dozens of other tests guarantee that coatings that military standards are safe for use.
Electrolube puts all of their coatings through basic and advanced testing. Purchasing Efficiency is owned and operated by ASAP Semiconductor LLC, an AS9120B, ISO 9001:2015, and FAA AC 0056B accredited distributor. We are your strategic purchasing partner, meaning you send us the RFQ and we will do the rest for you! While you focus on building, you can trust us to provide the best options in conformal coatings, aircraft bearings, aircraft fasteners parts, NSN parts, aviation parts, IT hardware parts possible.
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