September 28, 2017 - Updated
March 30, 2009 - Originally Posted
Alternative to Conformal Coating
Are there any reliable alternatives to the use of conformal coating to insulate solder joints and exposed conductors from condensing moisture? Are you aware of any form of die cut sheet material that can be applied to serve the purpose?
B.W.
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There are a number of UV/moisture dual cure and UV/heatdual cure materials that can be applied directly (jetted or needle) directlyonto leads or the edges of connectors. There are also epoxy-based thermallycured materials. These all have the benefits of adding mechanical reinforcementas well as moisture and fluid barrier protection.
Dr. Brian Toleno
Application Engineering, Henkel Electronics
Dr. Brian Toleno is the Application Engineering Team leader for Henkel Technologies. He is responsible for the technical service and application engineering for Henkel's electronics assembly materials, including solder paste, underfills, PCB protection materials, and underfills.
Not seen any precut sheet suited to this but a good chemical alternative is Rosin Lacquer as Rosin naturally repels water/moisture and is about the only material capable of locking away contaminants where as Conformal coatings generally only go over the top of them. Some liquid rosin fluxes offer this protection if left on the joint or PCB.
Greg York
Technical Sales Manager, BLT Circuit Services Ltd
Greg York has over thirty two years of service in Electronics industry. York has installed over 600 Lead Free Lines in Europe with Solder and flux systems as well as Technical Support on SMT lines and trouble shooting.
There are many types of conformal coating and many ways to apply them. I am not aware of any die cut materials that would work in this application. Some solder companies claimed that some specific high residue pastes would act as a protective barrier around component legs but this never became popular. If it is just local protection required on one specific part of a PCB then I suggest that you investigate selective application systems that can dispense, spray or jet the coatings onto specific parts of the PCB, or a paint brush! One other alternative would be a hot melt conformal coating applied locally with a heat gun as this is VOC free and cures within seconds. It is also important to make sure that you select the correct conformal coating and one that is compatible with all other chemistries on your PCB.
Chris Palin
European Manager, HumiSeal
Chris Palin is currently managing European sales and support for HumiSeal Conformal Coatings. His expertise is in test & reliability, solder technology, power die attach and conformal coating.
Some manufacturers use epoxy to pot their products to protect them from any environmental exposure. By creating a cavity and placing the board in the cavity and filling it with epoxy is one way to accomplish this task. After the potting process however there is no turning back, no rework, no nothing, if it works great and if it doesn't then it is scrapped. I'm mentioning this as this has to have some ROI analysis to compensate for yields and disposal cost. Die cut sheet metal, would have to be soldered in place such as with microwave components. The sections on the board would have to be designed to have a soldered shield to prevent moisture entrapment and prevent leakage. This would also require the plugging of all via holes to prevent moisture from coming through those openings. Best of luck
Leo Lambert
Vice President, Technical Director, EPTAC Corporation
At EPTAC Corporation, Mr. Lambert oversees content of course offerings, IPC Certification programs and provides customers with expert consultation in electronics manufacturing, including RoHS/WEEE and lead free issues. Leo is also the IPC General Chairman for the Assembly/Joining Process Committee.
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