best conformal coating for this project - Page 1
Forum section: electronics / general

author: RustyShackleford
author_rank: Regular Contributor
timestamp: November 07, 2021, 05:59:52 pm
content: I built this little widget - for the curious, it's a USB charger for a Palm Pilot Vx (yes, I still use one of those), which generates the required 4.2v charging voltage by reducing the 5v USB voltage with a MCP1826 low-dropout regulator.I'd like to protect it. I'm mostly concerned about the tiny wires from the cables that lead to the USB typeA plug and the Pilot connector - I'm worried about the solder joints on them being knocked loose, and also about the entire cable being pulled away. And the coating needs to be flexible enough to not crack as the cables flex.There seem to be some affordable MG Chemicals products at Amazon, but I'm not sure which one would be best, or if any are suitable:https://www.amazon.com/gp/product/B07B8RY7M6/ref=ox_sc_saved_title_2?smid=ATVPDKIKX0DER&psc=1https://www.amazon.com/MG-Chemicals-Silicone-Conformal-Coating/dp/B085G42TGS/ref=pd_bxgy_2/140-4287065-8416062?pd_rd_w=5mSMn&pf_rd_p=c64372fa-c41c-422e-990d-9e034f73989b&pf_rd_r=AF5MAH26249QCE9HH710&pd_rd_r=a6903996-f5c9-4291-b669-624d3e32d728&pd_rd_wg=R8JHU&pd_rd_i=B085G42TGS&psc=1

author: ataradov
author_rank: Super Contributor
timestamp: November 07, 2021, 06:36:55 pm
content: Conformal coating does not add strength. If this design works and you don't plan modifications, I'd just use epoxy to fix everything in place. Make small notches in the cable shroud, and it will be captured in the epoxy so that it will not pull out.

author: RustyShackleford
author_rank: Regular Contributor
timestamp: November 07, 2021, 10:11:29 pm
content: Yeah, I thought of epoxy - but if anything ever goes wrong, I'm SOL; but hey, it's less than $2 of parts. Regular silicon caulk might be more forgiving, except I've heard it's not healthy for electronics; though I wonder if that's true of GE Silicon II, which doesn't have the same acetic-acid cure process.

author: xavier60
author_rank: Super Contributor
timestamp: November 07, 2021, 10:31:54 pm
content: The only neutral cure Silicone I have ever found is Permatex 81730 Flowable Silicone. Beware, Permatex may still be using caps that self destruct causing any unused product to spoil in the tube.I use Threebond TB1530C, expensive though,https://www.aliexpress.com/item/1005002659183580.html?spm=a2g0o.productlist.0.0.32ef61ccL5pn4g&algo_pvid=08c5b103-43af-40e5-8661-86b40a690fba&algo_exp_id=08c5b103-43af-40e5-8661-86b40a690fba-0&pdp_ext_f=%7B"sku_id"%3A"12000021594511565"%7D

author: RustyShackleford
author_rank: Regular Contributor
timestamp: November 08, 2021, 04:14:46 am
content: What about Sugru ? They seem to say it's ok for electronics.

author: RustyShackleford
author_rank: Regular Contributor
timestamp: November 08, 2021, 04:27:13 am
content: I have a tube of this stuff lying around, bought for something else and never opened. Product info says nothing about electronics or dielectic strength though ...https://www.zoro.com/loctite-urethane-adhesive-dual-cartridge-169-oz-off-white-12-mix-ratio-3-hr-functional-cure-261797/i/G3159247/

author: xavier60
author_rank: Super Contributor
timestamp: November 08, 2021, 07:23:44 am
content: Quote from: RustyShackleford on November 08, 2021, 04:27:13 amIm sure it will be fine.

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: November 08, 2021, 04:28:00 pm
content: Quote from: ataradov on November 07, 2021, 06:36:55 pmYup. Epoxy pot that bad boy.

author: SL4P
author_rank: Super Contributor
timestamp: November 09, 2021, 05:57:38 am
content: To coat modules for environmental protection, I use a spray can of ‘electronics grade’ polyurethane.A couple of coats are fine, and you can peel or solder through it.Epoxy, or a shared is needed for physical protection.

author: RustyShackleford
author_rank: Regular Contributor
timestamp: November 11, 2021, 06:38:15 pm
content: Quote from: xavier60 on November 08, 2021, 07:23:44 amThe manufacturer recommended it too, so I gave it a try. Was sloppy, and didn't realize you needed a special applicator gun to mix the two parts as they came out, so didn't mix them properly. So now I've got a firm but gooey mess, though the circuit still works fine. I tried wrapping it with electrical tape, but the stuff is still oozing out between the wraps of tape. Maybe I've go over that with a coat of RTV silicon ... Shoulda tried the Sugru.