Conformal coating for marine environment - Page 1
Forum section: electronics / projects

author: Moriambar
author_rank: Unknown
timestamp: September 19, 2018, 07:56:23 am
content: Hi, I am looking around to understand how to choose a conformal coating for a pcb which is exposed to marine environment (well it has a case, but it is installed ~20m from the sea, facing it).I tried looking around but, being a beginner (and a total noob regarding this), I don't know what to choose. Is acrylic ok? Is something like MG 419C suitable or is there anything better?Most of all: how can I learn and understand how to select my conformal coating (for future projects too)?Thanks

author: Gyro
author_rank: Super Contributor
timestamp: September 19, 2018, 06:27:03 pm
content: You might want to consider some sort of protective soft wax type coating, I'm thinking that any defect in the conformal coat could allow salt ladened moisture to creep under it and cause corrosion - it's even been seen with electrolyte from burst electrolytic capacitors creeping under the PCB solder resist and destroying tracks.Maybe a combination of the two types? I'm sure there must be something automotive that would do the job.

author: SiliconWizard
author_rank: Super Contributor
timestamp: September 19, 2018, 06:53:18 pm
content: For a quick overview:https://www.electrolube.com/technical-articles/conformal-coating-vs-encapsulation-protecting-electronic-devices-which-do-i-choose/Acrylic coatings are easier to handle and "cleaner", but offer less protection than resin-based encapsulation.For a marine environment, I would tend to prefer a polyurethane encapsulation as Electrolube suggests, even though in your case there will probably never be any direct contact with water.

author: Moriambar
author_rank: Unknown
timestamp: September 19, 2018, 08:40:04 pm
content: Quote from: SiliconWizard on September 19, 2018, 06:53:18 pmnice, thanksQuoteOk, yes, there won't be any direct contact with water, only seaside moisture, which is kinda nasty by itself.Thanks

author: SiliconWizard
author_rank: Super Contributor
timestamp: September 19, 2018, 08:44:05 pm
content: Yes, salt-loaded moisture is very nasty.

author: helius
author_rank: Super Contributor
timestamp: September 19, 2018, 08:51:23 pm
content: Based on the technical criteria in this note, it looks like your choices are urethane resin or parylene for salt-moisture protection:https://blog.paryleneconformalcoating.com/best-conformal-coating-for-moisture-and-chemical-protection

author: iMo
author_rank: Super Contributor
timestamp: September 19, 2018, 08:52:45 pm
content: This is a video I like when talking conformal coating

author: Moriambar
author_rank: Unknown
timestamp: September 19, 2018, 08:54:40 pm
content: Quote from: helius on September 19, 2018, 08:51:23 pmOk, thanks

author: Zero999
author_rank: Super Contributor
timestamp: September 19, 2018, 09:56:09 pm
content: Quote from: Moriambar on September 19, 2018, 07:56:23 amDoes it have to be reworkable?How about simply potting the assembly or covering it with a layer of silicone rubber? If you go for the silicone rubber option, just make sure you get the type which doesn't produce acid whilst curing.

author: Moriambar
author_rank: Unknown
timestamp: September 20, 2018, 06:11:50 am
content: Quote from: Hero999 on September 19, 2018, 09:56:09 pmNopeQuoteBeing a noob any solution is ok to me, thanks!

author: Zero999
author_rank: Super Contributor
timestamp: September 20, 2018, 09:24:32 am
content: Quote from: Moriambar on September 20, 2018, 06:11:50 amWe use this at work for protecting PCBs. It's not cheap, but is highly resistant to oils and corrosive substances.https://uk.farnell.com/dowsil-formerly-dow-corning/3140-90ml/rtv-silicone-clear-tube-90ml/dp/101713?MER=sy-me-pd-mi-alte

author: Moriambar
author_rank: Unknown
timestamp: September 20, 2018, 09:37:08 am
content: Quote from: Hero999 on September 20, 2018, 09:24:32 amgreat thanks