Mounting Circuit Board ? - Page 1
Forum section: electronics / projects

author: vidarr
author_rank: Frequent Contributor
timestamp: December 21, 2022, 05:44:03 pm
content: I need to mount these two, 5v charging circuits to a piece of acrylic plastic (see pics).There is almost no space on the edges of the boards to screw down, or fasten somehow.The easiest solution would be to epoxy the circuit boards directly to the plastic, but I have no idea how this would affect the circuit (will it short out?).Another idea I had was to put a strap across the top of them (one strap each) and screw it down.In the pics, you can see the bottoms of the circuit boards and how they would look attached to the acrylic. The other pic shows the top of one and the bottom of the other.Any ideas appreciated. I am really stuck here.THANKS!

author: mariush
author_rank: Super Contributor
timestamp: December 21, 2022, 07:19:40 pm
content: you could take advantage of those cuts in the circuit board to have a sort of |--| shape made of plastic with one | glued to the plexiglass (or ideally going through the acryllic plastic)The T would have to be made of something insulated (plastic or something insulated steel wire or something.See the ms paint picture i madeBut i do have to know it's really not great idea to have High voltage exposed like that, ideally the boards should be in some plastic box even if they have super thin walls.

author: vidarr
author_rank: Frequent Contributor
timestamp: December 21, 2022, 10:04:52 pm
content: That is a good idea. I only thought about screws going thru there, but that would be a total fail. A plastic T would work great. Then, I could screw into the T from the bottom side and not have any screws near the board at all. I'll play around with this tomorrow.This plastic housing thing (in the pics) goes into another plastic box that no fingers can get into. Only the USB plugs are exposed, to plug devices in (these are JBL speaker chargers, super good quality and fast charging.)edit: Yeah, "H" shape, like you first said, maybe not "T" shape.THANKS!

author: james_s
author_rank: Super Contributor
timestamp: December 21, 2022, 10:54:56 pm
content: A blob of hot glue would work, or silicone, or a piece of heatshrink tubing large enough to go around the whole thing. Or mount nylon standoffs and use nylon screws to hold the board by the edges.

author: inse
author_rank: Super Contributor
timestamp: December 22, 2022, 03:00:54 am
content: Or fix them with a cable tie or this foamy type of double sided tape

author: Ian.M
author_rank: Super Contributor
timestamp: December 22, 2022, 03:23:19 am
content: Hot glue is unreliable with a high voltage across it It tends to form conductive tracks across its surface or even through its bulk which then heat up, melting and carbonizing the hot glue around them - keep it well away from any mains voltage circuits on the PCB.Silicone mastic/adhesive needs to be neutral cure, electronics grade. If it isn't neutral cure it will corrode your PCB and if it isn't electronics grade it may give off conductive by-products from its curing reaction which may cause tracking across a mains voltage PCB destroying it.Avoid generic white foam double sided tape - it invariably lets go with time, and you don't want PCBs carrying mains voltage rattling around loose. 3M VHB tapes however will hold a clean PCB for life.

author: james_s
author_rank: Super Contributor
timestamp: December 22, 2022, 08:24:43 pm
content: I've heard people say that about silicone although I've used the regular clear silicone bathroom caulk on electronics lots of times and never had it corrode anything. YMMV

author: Ian.M
author_rank: Super Contributor
timestamp: December 22, 2022, 09:08:16 pm
content: At a pinch, you can get away with automotive grade 'Oxygen sensor safe' silicone for low voltage electronics use. I'd be a bit leery if it had 230VAC across it . . .The ones to avoid at all cost are Acetoxy Silicones. They give off Acetic acid when they cure, which is death on electronics. If it stinks of vinegar as it cures, it the bad stuff.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: December 22, 2022, 10:24:46 pm
content: If you do not want or are not able to machine the base material, look into the catalogues of Essentra (Skiffy) or Keystone components. They have such edge-holding angles and clips in literally hundreds of styles.

author: james_s
author_rank: Super Contributor
timestamp: December 23, 2022, 12:29:11 am
content: Quote from: Ian.M on December 22, 2022, 09:08:16 pmAgain, I've used it lots of times without any consequences that I noticed, even for HV stuff in the many kV. It cured out in the open though, not sealed inside a box.