Extremely durable epoxy/epoxy like material - Page 1
Forum section: electronics / projects

author: adjustttt
author_rank: Contributor
timestamp: December 29, 2017, 11:29:22 am
content: Thanks to everyone who replied to my previous question about an extremely long lasting battery/energy storage device.I am now asking if anyone on here knows of an epoxy/epoxy like material that can be used for potting electronics, but which does not UV degrade, degrade significantly with temperature cycles etc, extremely durable basically.Learning from my previous post I need to also include the application. I am looking for such a material to encapsulate multiple micro controllers which will be exposed to UV from the sun, and other weather effects, and last a very long time 80 years like specified in my previous post.I am currently think that this material does not exist but I thought I would ask anyway.Thanks

author: bd139
author_rank: Super Contributor
timestamp: December 29, 2017, 11:49:20 am
content: Thought: It's more cost effective to make something replaceable than make it reliable enough to never be replaced.

author: adjustttt
author_rank: Contributor
timestamp: December 29, 2017, 11:52:01 am
content: I agree 100% but in this case the system cannot be replaced

author: Rerouter
author_rank: Super Contributor
timestamp: December 29, 2017, 11:58:51 am
content: currently almost all materials over this time frame will suffer from differences in CTE or coefficient of expansion, e.g. there is a minute difference between the pins of a microcontroller and the package of one, its small, but its there, this will also be different to the FR4 pcb material and different again to the SMD passive packaging,In general these will be close, but over 80 years, things will slowly tear off there joints unless you get very specialized, to clarify, BGA and QFN / DFN are out, and cannot be used, even for passives, throughole may prove better so long as you follow correct lead forming,As for weatherproofing, you say durable, but fail to give an indication of to what extent, for this time frame I would be thinking sealed in glass with external connections welded to the pins, and have desiccant packets inside to reduce the very slow long term leakage the seals will face. the glass blower can use UV repelling glass, however I do not believe the coatings are expected to last beyond 20 years in direct exposure to sunlight.

author: Jeroen3
author_rank: Super Contributor
timestamp: December 29, 2017, 12:04:39 pm
content: The problem here is that the epoxy reaction will never stop.

author: LaserSteve
author_rank: Super Contributor
timestamp: December 29, 2017, 03:28:39 pm
content: Things that need to last that long are mounted in Aluminum or Steel blocks with glass to metal hermetic seals. Purged with high pressure argon or nitrogen, then sealed with a cold welded pinch seal used on a copper or nickel fill stem.Refrigerator grade 30$ pinch seal tools based on vice grip pliars will not work for this task.My pinch tool is not for sale or loan nor rental. They used to be 1100$, now ten years on they have risen to 3200$.Steve

author: David Hess
author_rank: Super Contributor
timestamp: December 29, 2017, 06:49:16 pm
content: Seems like a good application for a die cast aluminum box except for humidity intrusion. I am not convinced that potting the entire board is better than conformal coating but in both cases, I would thoroughly clean the board and use a vacuum. We used to use a lot of gel like silicon potting compounds from Dow Corning.

author: RES
author_rank: Regular Contributor
timestamp: December 29, 2017, 07:33:07 pm
content: Tree resin?https://usercontent2.hubstatic.com/8378791_f496.jpg

author: Richard Crowley
author_rank: Super Contributor
timestamp: December 29, 2017, 08:35:25 pm
content: We don't understand why you jumped to the conclusion thatpottingis the solution to "extremely durable" ("does not UV degrade, degrade significantly with temperature cycles etc") Perhaps you omitted details which might prove beneficial to responses you might collect from this question. Else it seems like a random question of limited real-world significance.Is this for an application like undersea, intercontinental cable (which isn't potted)? Or outer-space inter-galactic deployment (which isn't potted, either)? Potting (and especially what a hard material like epoxy) seems rather unsuitable for your stated goals.

author: texaspyro
author_rank: Super Contributor
timestamp: December 29, 2017, 11:38:43 pm
content: If you mount the thing in a metal box, UV won't be an issue.Maybe beeswax? I've seen 150 instruments, etc with beeswax seals that are still good. But beeswax, being a natural substance, can be of variable quality / properties... not all bee barf is the same. There are sources of purified scientific grade beeswax. I've also seen ancient devices that used pitch for seals.Your best modern substance might be electronic grade silicone. Urethanes tend to want to revert to their native state of promordial goo over time.

author: David Hess
author_rank: Super Contributor
timestamp: December 30, 2017, 12:10:52 am
content: Beeswax breaths through which is acceptable for something in a climate controlled location but not so good for preventing long term damage from electrolysis. Its long term dimensional stability is not the best either.

author: fcb
author_rank: Super Contributor
timestamp: December 30, 2017, 08:45:17 am
content: If you can lower the exposure to UV with a stainless steel enclosure then there are many more possible solutions.I’d be tempted to look at things that have a proven track record of surviving long periods - military gear from WWII has survived very nearly 80yrs, what seals have they used?Look at the potting compounds used on 1950’s TV’s LOPT’s??I like the beeswax, but what about using pitch? Could you use an oil? Does it have to be solid?

author: BrianHG
author_rank: Super Contributor
timestamp: December 30, 2017, 09:06:35 am
content: I once used 3M Scotch-Weld DP270. I can guarantee functionality with coating an CycloneIII 780 pin BGA with DDR2 ram at 500MHz, operating at a full 105 degree Celsius & 0 degree Celsius without cracking, or any capacitive or resistive load on the data lines or effect on the crystals or 0402 parts.Don't use any sealant for the seams around your fence enclosure reservoir other than captain or electrical tape if needed for large seams. Apply a tiny amount around the seams of your fence/enclosure reservoir. Use an SMT heat gun at around 150 degree Celsius on the epoxy coated in your seams and it will completely solidify in 2-3 minutes. This will seal all your seams... Then fill enclosure reservoir and wait overnight and you will have a black glass like brick.This stuff is too fluid without a fence/reservoir/enclosure.(There are cheaper places to get this stuff other than Amazon, at Amazon, you are buying from a re-seller.) As for the gun and Nozzles, when I requested the epoxy from my local distributor, he included 3 DP270 cartridges, 2 guns and a hand full of nozzles as free samples.Epoxyhttps://www.3mcanada.ca/3M/en_CA/company-ca/all-3m-products/~/3M-Scotch-Weld-Epoxy-Potting-Compound-DP270/?N=5002385+3293242430&rt=rudGunhttps://www.amazon.ca/3M-08190-Performance-Applicator-Cartridges/dp/B0058X1GG6/ref=pd_sim_328_2?_encoding=UTF8&psc=1&refRID=AJHM4YPG4YVXA2M2782RNozzlehttps://www.amazon.ca/3M-38191-Static-Cartridges-Nozzles/dp/B00596QVHG/ref=pd_sim_328_1?_encoding=UTF8&psc=1&refRID=AJHM4YPG4YVXA2M2782R

author: 3roomlab
author_rank: Frequent Contributor
timestamp: December 30, 2017, 09:10:12 am
content: http://www.opensourceinstruments.com/Electronics/A3013/Encapsulation.htmli remember reading this article ... great devices and great info*addition, i wonder if plastidip counts as protection but its non-epoxy

author: LaserSteve
author_rank: Super Contributor
timestamp: December 30, 2017, 05:14:28 pm
content: Pot your device, expect a lifetime of about 7 years based on my experience. Do what they do for aircraft, hermetic housing, gas fill, mil-spec conformal coating, after selecting parts that the coating will not egress into. I've opened forty year old avionics that looks like it was just made.Steve

author: BravoV
author_rank: Super Contributor
timestamp: December 30, 2017, 05:36:23 pm
content: Not sure if this fits in your requirement, result from one of the member here while ago, read carefully this particular post ->HERE 1stand then subsequent proof ->HERE, to me its quite convincing.