Conformal Coating Questions & Answers
Conformal coatings are used to protect electronic components and circuitry on printed circuit boards from damaging environmental factors. There are many different types of materials on the market from epoxy to parylene, but users of light-cure coatings frequently ask similar questions about the technology. A few of the more common Q&As are summarized below:
Question: Does liquid resin that flows under a component (into a shadowed area) cure over time?
Answer: It depends on the formulation and its secondary cure mechanism. UV/moisture-cure coatings will cure over time without light exposure. Time alone does not cure UV/heat-cure conformal coatings. More information on shadow area curing can be found here.
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Question: If a small amount of conformal coating material goes into a shadowed area and a secondary heat cure is not used, what impact does the uncured conformal coating have on my board and components?
Answer: It depends on many variables including the amount of coating, board topography, and presence of contaminants on the board. Small quantities of uncured conformal coating alone have not been known to impact the long-term performance of boards. Dymax always recommends that measures be taken to eliminate the presence of uncured conformal coating through controlled dispensing methods, and, when necessary, multiple-cure mechanisms. All your questions about conformal coatings are answered in this comprehensive guide.
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Question: Why does the conformal coating have a tacky feel on the surface minutes after curing?
Answer: The coating was likely not exposed to enough UV light. A high-intensity lamp utilizing a bulb with maximum wavelength output at 365 nm (nanometers) is recommended. Dymax coatings should be tack free almost immediately after cooling. Read this blog post for more information.
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Question: How do you know if the conformal coating is cured?
Answer: When the coating has a surface free from tack, and the coating in contact with the board has solidified. All light-cure coatings feel tacky immediately after curing because they are still warm from the lamps and should be assessed after the coating has cooled, often seconds after leaving the light source. Very soft coatings feel like soft rubber. To judge whether the coating flush to a printed circuit board is cured, run a test specimen and try to pick the coating away from the PCB using a sharp tool. Additional information about curing is available in this conformal coating selector guide.
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Question: How do you know if the material is cured in a shadowed area after a secondary cure?
Answer: For UV/Visible light-cure coatings, this work may include destructive and performance testing of parts made with minimum and maximum amounts of coating, UV/Visible light intensity, and exposure time allowable by the process.
If you have a conformal coating project you are working through and have questions, contact one of our Application Engineers to discuss it in detail. They are available to help troubleshoot your most difficult challenges.
Dymax has additional educational materials available to assist you:
Case Histories:
* Improving the PCB conformal coating process by increasing production output. Find Out How!
* Increasing Production and Reducing Processing Time in PCB Assembly. Learn More!
EBook: Protect Printed Circuit Boards in Automotive Electronics.
Guide: Comprehensive Guide to Light-Cure Conformal Coatings.
Starter Kit: All the essential reading material you need to understand conformal coating technology.
White Papers: A selection of white papers are available in our Resource Library.
* Increase PCB Performance with Light-Cure Conformal Coatings & Maskants
* Light & Moisture Cure Automotive Conformal Coatings
* Very Low Viscosity Conformal Coatings