Are there inject-able epoxy for injecting into electronic devices? - Page 1
Forum section: electronics / beginners

author: engineheat
author_rank: Frequent Contributor
timestamp: June 26, 2019, 01:04:32 pm
content: I'd like find a type of transparent epoxy that I can inject into an electronic device (thru a drilled hole). The epoxy should cure and solidify all the internal components. Then, I'd like to saw it open. This is for quality inspection purposes.I guess the epoxy should have a low enough viscosity before curing so it can flow well, and it should be clear when cured. Are there anything out there suitable for this?Thanks

author: reboots
author_rank: Regular Contributor
timestamp: June 26, 2019, 02:54:24 pm
content: I have had very good results with 3M DP-270 clear epoxy. It's an injectable 2-part epoxy with very low viscosity and long working time. It cures clear and very hard. Unfortunately it's somewhat expensive.I use DP-270 to pot electronic sensor assemblies in machined polycarbonate rods. The rods have drilled channels to transfer epoxy to each sensor pocket, and I use a single injection point to flow epoxy throughout the assembly. You will ideally have gravity on your side, injecting from the lowest point and letting air escape from the top to minimize bubbles.https://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-Scotch-Weld-Epoxy-Potting-Compound-DP270/?N=5002385+3293242430&rt=rudAvailable from McMaster-Carr:https://www.mcmaster.com/7467a274-7467A17Requires dispensing gun:https://www.mcmaster.com/7467A41And mixer nozzle:https://www.mcmaster.com/7467A12If the 3M epoxy is out of your budget, MG Chemicals 832WC is a bulk electronics potting epoxy which appears to have good characteristics. I have not tried it myself. You would need to devise your own injection method, perhaps a plastic syringe.https://www.mgchemicals.com/products/potting-compounds/epoxy-potting-compounds/832wc-epoxy-encapsulating-potting-compound

author: engineheat
author_rank: Frequent Contributor
timestamp: June 26, 2019, 04:03:40 pm
content: Quote from: reboots on June 26, 2019, 02:54:24 pmThanks. If I use a plastic syringe, it's probably easier to inject from the top. Injecting from the bottom would require a good seal I assume. I'm tolerant of a little bubble in my application, as long as the part I'm interested in is bubble free. So I can probably get away with injecting from the top right?

author: rstofer
author_rank: Super Contributor
timestamp: June 26, 2019, 04:52:58 pm
content: Volume can be a problem. Curing is an exothermic reaction and with sufficient volume, things get real exciting. Depending on the volume being poured, injection isn't nearly as big a problem as cooling.

author: Gary350z
author_rank: Regular Contributor
timestamp: June 26, 2019, 05:08:17 pm
content: Use "casting resin". It is thin, clear, gets very hard, and is easy to use.Local craft stores carry it;https://www.hobbylobby.com/search/?text=casting+resinhttps://www.michaels.com/search?q=casting%20resinhttps://www.joann.com/search?q=casting+resinor google search;https://www.google.com/search?rlz=1C2NHXL_enUS691US728&source=hp&ei=X6UTXe3CI4rbtQbnuYj4BQ&q=casting+resin&oq=casting+resin&gs_l=psy-ab.1.0.0l10.2799.2799..4685...0.0..0.91.183.3......0....2j1..gws-wiz.....0.HM3LmS05v34

author: reboots
author_rank: Regular Contributor
timestamp: June 26, 2019, 06:08:57 pm
content: Quote from: engineheat on June 26, 2019, 04:03:40 pmSure, you can do that. If your device has any complex internal features, however, you probably want to minimize air trapped under those features so the epoxy can support them for sawing. I recommend injecting the epoxy, then tilting the device acutely on X and then Y axis for several minutes. This will encourage trapped air bubbles to move free and rise to the top.Another thought would be to saw upwards, against any air bubbles.I've also used a length of heat shrink tubing over the injector nozzle as a flexible extension to place epoxy directly at critical points with poor accessibility.

author: Mr. Scram
author_rank: Super Contributor
timestamp: June 26, 2019, 06:15:08 pm
content: To eliminate all air bubbles you could degass the thing with a vacuum.

author: Benta
author_rank: Super Contributor
timestamp: June 26, 2019, 07:50:59 pm
content: Clear Epoxy as normally used for lamination work (2:1 mix) is already pretty fluid, close to water.Doing the operation in vacuum is a very good idea, additionally heating the whole assembly after filling makes the epoxy thinner. 180 deg C is optimal, but probably not suitable here. But if you can heat the assembly to 80...100 deg C, it makes a big difference. It also accelerates curing time significantly, like from 24h to 4h. At least heat to 60 deg C (curing 10h).

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: June 26, 2019, 08:43:51 pm
content: QuoteIdeally what you want is two ports diagonally opposite each other with respect to the cavity you are trying to fill so that you can inject on one port and vacuum draw on the other . This is called resin transfer molding and it works well to eliminate voids.https://www.osborneindustries.com/news/resin-transfer-molding-process-works/https://en.wikipedia.org/wiki/Transfer_moldingYou can ignore the steps used by industry to insert fiber reinforcement in the open mold prior to the draw as it doesn't apply to you.The epoxies that are sold as casting resins tend to be lower viscosity than a general purpose epoxy like West systems. Benta confuses the meaning of viscous with the opposite, however his recommendation to warm the part is good.

author: Benta
author_rank: Super Contributor
timestamp: June 26, 2019, 08:56:17 pm
content: @chickenHeadKnobThanks for clearing up my misinterpretation of "viscous". I've edited my post accordingly.

author: engineheat
author_rank: Frequent Contributor
timestamp: July 19, 2019, 03:03:13 am
content: Quote from: reboots on June 26, 2019, 02:54:24 pmThis is for work. I tried buying the 832WC but my company won't let me due to a need for respirator according to the Material Safety Data Sheet. My employer is super big on health and safety.Same for the 3M one.Any other alternatives? This might sound ridiculous but would clear Elmer's glue work? I wonder if it can even dry completely into a solid. Or maybe JB Weld? But that might be too thick and solidifies too quickly, not to mention having to mix it.