Glueing pcb to pcb - Page 1
Forum section: electronics / general

author: stoyanoff
author_rank: Contributor
timestamp: August 13, 2021, 03:12:07 pm
content: Greetings! Is it possible to glue a pcb to a pcb on 90 degree angle? I am aware there are metal angle brackets which I can use to mount the small pcb with a screw, but the problem is these brackets are made of metal(conducting current). These are high voltage pcbs and the metal bracket will break the minimum clearance I need. I don`t have space. So can I just use hot glue to mount them? I expect vibrations on the device and I want this joint to be servisable. Is this a good idea? What are the odds?Thanks!

author: TimFox
author_rank: Super Contributor
timestamp: August 13, 2021, 03:33:25 pm
content: Can you use cut pieces of plastic or fiberglass-composite right-angle stock epoxied to both boards?

author: Kleinstein
author_rank: Super Contributor
timestamp: August 13, 2021, 03:37:33 pm
content: Hot glue may not stick very well to the PCB. It can still be OK if the are slits / holes or similar so that it is more than just sticking to the surface.Surface adhesion is often tricky with plastics.There are also plastic (nylon) screws.

author: stoyanoff
author_rank: Contributor
timestamp: August 13, 2021, 03:57:55 pm
content: Ok, plastic clamps can do the trick, but how many should i use on a pcb? My pcbs are small 25x50mm. The biggest component I have is a 220nF X2 cap. How many clamps should I have 1,2,3? How do you determine that?

author: AaronD
author_rank: Frequent Contributor
timestamp: August 13, 2021, 06:02:43 pm
content: Would this be an option?:https://hackaday.com/2015/06/03/how-to-build-beautiful-enclosures-from-fr4-aka-pcbs/Essentially, you design your PCB's with large copper strips where they need to join, and then solder the strips together. Similar to the hot glue idea, except that your "glue" is actually solder.

author: Mario87
author_rank: Frequent Contributor
timestamp: August 13, 2021, 08:07:27 pm
content: You mentioned metal 90* angle brackets and the issue being that it will break you minimum clearances. Why not just use plastic or custom 3D printed 90* angle brackets? Will work better than any glue and will be easily serviceable.

author: TimFox
author_rank: Super Contributor
timestamp: August 13, 2021, 08:29:28 pm
content: "Right-angle stock" is available in G-10/FR4 composite and in smaller sizes in PVC and polycarbonate plastics. These should work for insulation and gluing/epoxy or nylon screws.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 13, 2021, 10:12:44 pm
content: How do you mean serviceable? If it has to be removable, it has to be locked in some way, or vibration will eventually remove it for you (depending on how much, and for how long, of course; you didn't give a magnitude). Which strongly suggests fasteners, or some kind of mechanism (snaps?). Especially if you need a rigid connection, this strongly suggests flanged attachment -- like using angle stock bolted to the riser and base boards. All of which can be done in plastic, though it kinda sucks (nylon bolts/nuts aren't very strong, and strip easily).As gluing goes, the best would be fiberglass or ceramic loaded epoxy, with the boards intersecting in a slot, glue filling the gaps, plus a fillet of glue around the joint (maybe with the assistance of braces or gussets, or additional filler material). Needless to say, this is not serviceable, they're bonded ideally as strong as the base material itself.Tim

author: floobydust
author_rank: Super Contributor
timestamp: August 14, 2021, 04:41:57 am
content: Quote from: stoyanoff on August 13, 2021, 03:57:55 pmOP if you have components with mains, then gluing pcb's is not a good idea. That cap/board getting loose you would not want to short to anything and cause a hazard.Formal tests are a bump and drop, it should withstand that, even years from now.Essentra(formerly Richco) might have ideas butKeystonedidn't have anything right-angle.

author: stoyanoff
author_rank: Contributor
timestamp: August 14, 2021, 07:20:29 pm
content: Thanks for the answers! I will try to increase the size of the board and use metal angle keystone connectors.What about the number of holders per PCB? What weight can one connector hold?Thanks!

author: TimFox
author_rank: Super Contributor
timestamp: August 14, 2021, 07:50:00 pm
content: I have had good luck with right-angle mounting with the 1/2-inch wide Keystone brackets. I usually use the ones with one clear hold and one 6-32 tapped hole. The metal can be soldered to, as well, but the screws or rivets are recommended.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 14, 2021, 08:51:51 pm
content: What is this doing, by the way, if not connecting electrically? If something like an insulating spacer, I might recommend plastic foil (modest thickness polyester sheet or whatever; other materials are also suitable, including fishpaper, rubberized fiber, etc.), bent into a suitable form to follow the isolation path (and provide some stability), with tabs cut to fit into slots in the board, and clinched or glued to secure it.If it's mounting components, then how shall they be connected, if not through the mounting?A typical use case, for intersecting PCBs, is to fit edge connectors into slots, making a right-angled solder joint to connect them. Which isn't too strong (there's very little overlapping material) so additional support is always a good idea, or use right-angle headers which can be solder-in or using sockets; but they can make nice compact and affordable assemblies.Here's kind of an example, though he doesn't go into detail of the design, and you kind of have to pause the video to get furtive glances at it from various angles...Anyway, the boards are intersecting a bit, making a box-like structure that's stiffer than a single joint would be; plus it's all stuffed inside a metal enclosure, with what looks like die-cast blocks for right-angle mounting.Example of headers, see the control board here:http://www.righto.com/2021/05/teardown-of-pc-power-supply.htmlI took apart a... oh hey I actually found the same one I think. So this guy's doing a repair on one, so you get a good view of everything:I seem to remember another perpendicular board for the terminal blocks, and don't remember a passive PFC choke, or whatever that is there; but I threw out the boards so I can't check. Anyway, another example of using headers. Notice the line isolation barrier appears across the right-angle board, so it's designed with two headers, and considerable distance inbetween.As for mounting strength/weight, it depends. Brackets are stronger in tension than bending. I'd expect one bracket to support a few kilos of weight, or the equivalent peak loading force, if applied in shear. But bending, how close is the mass to the bracket / how tall is the riser board? The bending moment is given by applied acceleration times moment of inertia. Best to outright prevent a bending moment, by constraining the board on the opposite side as well.From the above cases, the control board is simply light, and also the header provides some flexibility, and it's ultimately constrained by the components in front of it and the enclosure behind. The terminal block board is registered against the main board by two shoulders and one peg-in-slot, as well as (I think) slots in the enclosure. (Which is especially important, given the torquing expected on those terminal blocks.)Card guides can also be used, like these thingys,https://www.digikey.com/en/products/detail/bivar-inc/VG2-2/3102495or similar slots in the enclosure, or the version that snaps into the enclosure like these,https://www.digikey.com/en/products/detail/essentra-components/RSSHG-201-165/2203810Tim

author: DIYGUY Chris
author_rank: Contributor
timestamp: August 15, 2021, 09:54:25 pm
content: Since the boards are joined in a 90 degrees angle then the plastic joints is not a solution.I recommend this idea of making a large copper line all along the joining space and solder both boards to each other, make sure that on your PCB designs you use just copper areas without any connected net

author: AaronD
author_rank: Frequent Contributor
timestamp: August 16, 2021, 04:01:21 pm
content: Quote from: DIYGUY Chris on August 15, 2021, 09:54:25 pmOr you could connect/via-stitch them to your ground plane?(via-stitching would greatly help the mechanical strength too, even if it wasn't electrically connected...but then you'd need to reserve that space on multiple layers)

author: DIYGUY Chris
author_rank: Contributor
timestamp: August 16, 2021, 09:32:58 pm
content: I was repairing a circuit board that comes to my lab today and I saw such technique to attach two circuit boards in 90 degrees angle so maybe this could be a solution.please check the following images" alt="" class="bbc_img" />" alt="" class="bbc_img" />

author: Clif
author_rank: Newbie
timestamp: August 17, 2021, 03:01:39 am
content: the connection is not good, the soldered area is too small to provide enough mechanical strength because the plating hole was empty with solder

author: CatalinaWOW
author_rank: Super Contributor
timestamp: August 17, 2021, 04:48:33 am
content: I would suggest that doing this correctly requires a real mechanical analysis with loads and operating conditions. Anything less is kind of like posting a question on a board saying "Can I put super capacitor on my inputs to control transients. I don't have room for the normal ceramic capacitors."We don't ask mechanical engineers to do electronic design for a reason. When mechanical engineers do electronic design they either learn enough to be adequate electronic engineers, or they put belts, suspenders and any other kind of overdesign in and then cross their fingers hoping it will work. Electronic engineers should expect the same in reverse. (I'm speaking as an engineer that didn't decide which path to follow in engineering until close to my degree, and whose career has straddled both disciplines. One interpretation being that I am mediocre in both fields).That said, there are general rules that should guide your decision. The more area your joint has the lower the stress. Plastics are generally weaker that metals by an order or magnitude or more. So for equivalent strength they need to be larger in cross section. Your PWB is a plastic and will limit the strength of the assembly, which can guide you in how strong your joints need to be. Glues tend to be weaker than plastics, though the range of strengths overlaps plastics. And finally, adhesive joints depend heavily on surface preparation and sometimes on voodoo. If you really care whether your assembly stays together an adhesive joint requires a great deal of attention to process control. And a full mechanical analysis is a big job.