Suggestions for glue to anchor PCB within an enclosure? - Page 1
Forum section: electronics / general

author: HwAoRrDk
author_rank: Super Contributor
timestamp: February 25, 2025, 10:00:30 pm
content: I have a board which goes into a plastic enclosure that doesn't have screw mounting but rather just sits on ribs in the bottom half and gets constrained vertically by ribs on the top half. However, to cope with manufacturing tolerances, etc. the fit of the board outline must necessarily be fairly loose. (I messed up with the first prototype and made the board dimensions too near those specified on the drawings for the enclosure's inside dimensions, and it inadvertently became a press-fit.) This unfortunately means the board rattles side-to-side inside the enclosure.I was thinking of applying some glue to secure the board; perhaps a small, discreet bead down one edge.Can anyone suggest a suitable glue?Some constraints:- I don't want to use hot-melt glue as the enclosure is translucent and big blobs will look ugly.- Preferably something that is serviceable - non-permanent and removable without damage to the PCB or enclosure.- Obviously I don't want to use anything that in case of overspill might degrade or interfere with circuitry long-term (e.g. the infamous white stuff that goes crusty, brown and conductive), because some components and traces are near the edge of the PCB.- Not 100% sure what kind of plastic the enclosure's made from - annoyingly the manufacturer doesn't specify on their datasheet.

author: Gyro
author_rank: Super Contributor
timestamp: February 25, 2025, 10:09:34 pm
content: A translucent enclosure and glue sounds like the perfect storm. I think I would go for some form of rubber self-adhesive pad, maybe wrapped over the end of the board for minimum visibility. At least that would look 'designed'.

author: langwadt
author_rank: Super Contributor
timestamp: February 25, 2025, 10:21:59 pm
content: how about some kind of split rubber sleeve on the edge of the board?

author: HwAoRrDk
author_rank: Super Contributor
timestamp: February 25, 2025, 11:01:40 pm
content: Quote from: Gyro on February 25, 2025, 10:09:34 pmYeah.But hopefully there's a solution. I chose a translucent enclosure so I can have indicator LEDs on the board and not have to make holes for them in the case.I don't really have room for any kind of pad or sleeve on the edge of the board. It's a small PCB and enclosure - about 60 x 30 mm. And there are components <1 mm near the edge of the board in several places.Would PVA glue work? Would it stick to plastic and PCB? That can usually be peeled off smooth surfaces.I've just recalled one time I took apart a USB memory stick and the board was stuck into the enclosure with some kind of stringy, flexible adhesive that was yellow-ish and semi-transparent. It looked like it had been applied with a brush around the edges (i.e. the PCB was placed in, then glue applied). I was able to peel/scrape it away. Would that have been some kind of contact cement?

author: b177
author_rank: Contributor
timestamp: February 26, 2025, 02:45:05 am
content: Loctite 4204Possibly overkill for the job, but almost guaranteed to work for a near permanent solution.this is a filled gel EA (ethyl cyanoacrylate), far superior to regular superglue

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 26, 2025, 03:07:09 am
content: You want sometime a bit flexible to accommodate differences in your board CTE and any changes in dimension due to humidity changes. Hot glue meets that requirement, as do most RTVs, rubber cement and a few others.All of these when casually applied can give the "big blobs" you want to avoid. But with appropriate application techniques all can give the results you want. Something like a solder stencil with a squeegee can work. There are other solutions.Some RTVs can be problematic because of emissions during curing, but there is an excellent chance that with the small bead that you want there won't be a problem.For an out of left field suggestion, have you thought of modeling clay, dental wax or other non-adhesive filler to keep the boards from rattling around?

author: xavier60
author_rank: Super Contributor
timestamp: February 27, 2025, 02:04:17 am
content: It's self-leveling.https://threebond-europe.com/products/tb1530/Too expensive for a one-off job.TB1530C is clear.

author: MarkF
author_rank: Super Contributor
timestamp: February 27, 2025, 03:13:33 am
content: How big is the gap?I've been using two different glues on my model railroadthat are clear and peel off if you want to remove it.Microscale Micro Krystal Klear. It's milky white in the bottle but dries clear.I use it for headlight lenses. It's a little like rubber cement to remove.Mod Podge. It also dries clear and works on plastic. Even my 3D printed PLA parts.They are both fairly thin and wouldn't fill a gap more than a millimeter.I would apply either with a small artist paint brush for a thin bead.

author: shabaz
author_rank: Frequent Contributor
timestamp: February 27, 2025, 08:12:02 am
content: I think I know the type of enclosure you mean; presuming your PCB is now (say) 0.5 mm or so smaller, you'll get the rattle. Maybe silicone could be applied; example is Loctite SI5980 (but there are plenty of other options) which is odorless/non-smelly, cheap (a toothpaste-tube sized quantity of it will last for hundreds of boards), and easy to wipe off the PCB if it accidentally smears onto the PCB faces while applying.I quickly gave it a shot on a scrap PCB; I think if the PCB was designed with a couple of very shallow notches on each edge (say 5 mm wide but only 0.5 or 1 mm deep, then applying a little silicone in the notch would look quite neat, and then once dry, the PCB could be assembled into the enclosure and the dried silicone would act as tiny rubber feet compressing against the enclosure.The attached photo shows just a rough smear on a board edge (and then any excess on the PCB face was wiped off with a tissue as mentioned). A syringe needle would allow a neater tiny dab since it wouldn't need to be applied along the entire edge.

author: HwAoRrDk
author_rank: Super Contributor
timestamp: February 28, 2025, 02:13:09 am
content: Hmm, I hadn't thought of using silicone. That would certainly be non-permanent and removable. Thinking about it more, as others have said, I don't really necessarily need something toadherethe board to the enclosure, just something to fill the gap and stop the board moving.I think I even have a small tube of clear silicone somewhere.Quote from: MarkF on February 27, 2025, 03:13:33 amHuh, I'd heard of Mod Podge, but I didn't think it was an actual brand name product, rather an American slang term for generic PVA-like glue!

author: Smokey
author_rank: Super Contributor
timestamp: February 28, 2025, 03:27:25 am
content: This sort of thing?

author: jpanhalt
author_rank: Super Contributor
timestamp: February 28, 2025, 04:42:54 am
content: Any gap filling adhesive can be applied to be ugly or neat.If the gap is several mm, I think you should reconsider a couple of neat dots of hot melt. It is easily removed with a drop of isopropyl alcohol. If the gap is small, consider credit card glue (aka fugitive glue). It holds well and releases relatively easily.

author: Poroit
author_rank: Frequent Contributor
timestamp: February 28, 2025, 06:45:27 am
content: Sika 11FC

author: Kean
author_rank: Unknown
timestamp: February 28, 2025, 01:34:23 pm
content: How about some narrow double sided adhesive tape that you put along the PCB edges?You can get it in 1mm, 1.5mm, and 2mm widths quite cheaplyhttps://vi.aliexpress.com/item/1005006624776989.html

author: spostma
author_rank: Regular Contributor
timestamp: February 28, 2025, 02:57:36 pm
content: You could take advantage of the fact that the walls of a plastic enclosure are more flexible in the middle of the side (and very stiff in the corners).Just make the PCB edge protrude +0.5mm in the middle of the longer sides could solve the rattling.

author: tooki
author_rank: Super Contributor
timestamp: February 28, 2025, 06:46:21 pm
content: Quote from: HwAoRrDk on February 25, 2025, 10:00:30 pmI would do one of the following:- hot melt (you don’t need “big blobs”, some tiny little droplets will do fine). This has the advantage, as jpanhalt said, that it is easily removed with a few drops of alcohol.- clear acrylic linerless double-stick tape like 3M VHB 4905 and 4910. It comes in two thicknesses and various widths, and releases cleanly without residue. It is water-clear if you keep it clean before and during assembly. I love this stuff.- clear building adhesive like UHU Poly Max (various versions sold under different names in different markets, like “crystal” or “transparent”). These are SMP adhesives (silyl-modified polymer) and cure with practically no odor, and releasing just a small amount of alcohol vapors, so should be safe for electronics. (At work, we have used SMP adhesive from Sika on many things, with no signs of incompatibility with electronics.) Unlike clear silicone, clear SMP really is totally transparent.- little foam buffers- self-stick felt or similar, just a little wrapped over the edge

author: jpanhalt
author_rank: Super Contributor
timestamp: February 28, 2025, 06:57:28 pm
content: A lot of us, myself included, seem to assume the bottom is smooth. That is, no TH components. TS has not said whether that is true.Are there TH components?

author: jfiresto
author_rank: Frequent Contributor
timestamp: February 28, 2025, 07:24:04 pm
content: Quote from: tooki on February 28, 2025, 06:46:21 pmI was waiting for someone to recommend SMP (modified silane polymer) adhesive which has pretty much displaced polyurethane adhesives, such as Silkaflex-11 FC, in these parts. You can also get it as a two-component adhesive if you are impatient or need to lay it on thick. The last one I used came in a coaxial dispenser feeding a twist-on static mixer.

author: jpanhalt
author_rank: Super Contributor
timestamp: February 28, 2025, 07:47:05 pm
content: The TS has indicated he wants something that is easily removable. Do SMP adhesives fit that need?

author: HwAoRrDk
author_rank: Super Contributor
timestamp: February 28, 2025, 07:47:42 pm
content: Quote from: tooki on February 28, 2025, 06:46:21 pmI've never used a hot glue gun that was capable of dispensing a controlled, small amount. Maybe I've just had the misfortune to use crappy glue guns.Quote from: tooki on February 28, 2025, 06:46:21 pmHmm, I think I have some UHU somewhere. Maybe I'll give it a try. Assuming it's not like the tube of silicone I previously mentioned. I found it, and even though it was unopened (i.e. tube still sealed), it'd dried out completely!Quote from: jpanhalt on February 28, 2025, 06:57:28 pmYes, there are through-hole components. The board does not sit on the bottom surface of the enclosure. Like I said before, it sits on some vertical standoff ribs around the edge (which are there precisely to give space for THT leads), of which there are a matching set on the top half of the enclosure. They constrain the board from moving up and down (the ribs effectively 'clamp' the board), but if the board is not an exact fit to the enclosure, there is room for the board to move side-to-side.

author: jpanhalt
author_rank: Super Contributor
timestamp: February 28, 2025, 08:20:13 pm
content: Since there are rails, double stick tape will work. I use it mainly for very temporary fastening (< 1week). Fugitive glue or small dots of hot melt would still be my recommendation. It's probably a toss up between the three. I have a tough time applying doublestick that lacks a support neatly.

author: thephil
author_rank: Regular Contributor
timestamp: March 01, 2025, 10:46:20 am
content: Not exactly what you are asking for, but I usually use plastic glue (the type that dissolves the plastic surface) to stick hollow plastic feet to the case in a convenient location and then screw the board to those feet-/standoffs.

author: Kasper
author_rank: Frequent Contributor
timestamp: March 01, 2025, 04:00:16 pm
content: Double sided foam tape, cut strips to size.Electronics grade RTV, applied with syringe.Draw your own case. FreeCAD is free and easy to learn.This might be ESD-phobic but I try to limit contact between case and PCB, particularly on any nets that aren't GND.

author: nali
author_rank: Frequent Contributor
timestamp: March 01, 2025, 05:37:52 pm
content: Quote from: HwAoRrDk on February 28, 2025, 07:47:42 pmDepending on availability of board space you could add a couple of slight bumps along the board outline (which correspond to the tolerance extremes and make it a press fit), with a slot cut in the PCB body just inside them and parallel to the edge giving them some spring if that makes sense.

author: 5U4GB
author_rank: Super Contributor
timestamp: March 03, 2025, 08:00:24 am
content: Quote from: HwAoRrDk on February 28, 2025, 02:13:09 amMod Podge is acrylic paint without colourant added. So it'll do the same things that acrylic paint does.For your use you could probably get away with a spot of clear fingernail varnish to lock the board in place while also making it removable later if required. In particular if it's a one-off and small scale you don't want to spend a small fortune on NASA-grade sealant.

author: coppercone2
author_rank: Super Contributor
timestamp: March 03, 2025, 08:02:15 am
content: does MSP smell like wintergreens ?IIRC Go2Glue was silane based. It smelled like wintergreens and was a totally kickass adhesive with a long cure time.I glued my horn antenna prototype with it, glued a HVAC duct into a wall with it, did sheet rock with it and a few more uses. And it outlasts most of the other shit in storage.I did notice home depot stopped carrying it, I always wondered why. With its performance, I thought it was some psychological thing that people thought "no way this stuff that does not smell like death is going to work" (dumbass burleymen?)I noticed gorilla glue outsells everything (and IMO it sucks ass), I always thought it was the marketing lol, ima big alpha like that stupid fucking gorilla