Bent PCB? - Page 1
Forum section: electronics / general

author: JonnyBadger
author_rank: Newbie
timestamp: July 08, 2018, 11:05:50 am
content: I have an interesting question to ask.Have any of you had success bending printed circuit boards?I am making a costume piece helmet out of salvaged PCBs from old laptops and I would love to be able to bend the edges at 90 degrees to make it easier to rivet them together. I'm thinking about heating the PCB up and working slowly (like bending acrylic or plexy) but I'm not sure how this would work with the fiberglass and metals that exist on a loaded up board. I should mention that I want to leave most of the components on there for the look of the thing.I have read some great advice in regards to cutting PCBs on this page and just thought I would also ask about bending.Thanks in advance gang.JBH

author: janoc
author_rank: Super Contributor
timestamp: July 08, 2018, 11:26:15 am
content: That will certainly not work.FR4 can be bent somewhat but certainly not 90 degrees. It will break instead. And heating it will not do you any good - it is not thermoplastic (unlike e.g. acrylic), so it will not get softer when you heat it. It will only scorch and delaminate.Also, if you somehow manage to bend the board, the stresses on the bend will make the board unusable as any sort of structural element because it will crack and fall apart at the bend after a while. The epoxy in the laminate is designed to be hard, it is not really possible to make it change shape once it has set during manufacturing.If you need 90 degrees for mounting, your best bet is to drill holes and put some mounting brackets or something similar on it. Or cut/break it and connect the pieces together at the angle you need using some mounting hardware.

author: Raj
author_rank: Frequent Contributor
timestamp: July 08, 2018, 03:35:26 pm
content: Here's a pcb forceps bent under high heat.I won't recommend bending them for decorative purposes unless you have a lot of them lying around to test your process.If I were to make a functional bent pcb again,I would use a process similar to CNLhor's glass pcb manufacturing.I would stick copper on a prebent acrylic board, then mask and etch it.

author: Corporate666
author_rank: Unknown
timestamp: July 09, 2018, 01:23:31 am
content: It depends on the PCB thickness and the bend radius.Since these are surplus/junk PCB's, I am guessing they are most likely standard 1.6mm/0.062", which will not bend at all, pretty much. 0.8mm won't really bend either. Once you start getting into 0.4mm, you can start to bend them quite well, but for a 90 degree bend, you would need some reasonable radius (something like perhaps an inch?).One thing that may work well is to score the PCB on the back side almost all the way through, then you should be able to bend it while preserving the visual appearance on the other side - this will only work if you are bending an area without components though, since obviously the components themselves will not bend.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: July 09, 2018, 01:39:30 am
content: These boards do get soft and easier to bend with heating. But my experience is that the temperature required to get that flexibility is close to/above the char point so the boards wouldn't be pretty afterwards. They also permanently lose strength. All around a bad plan.I know their are some solvents which will soften the epoxy. Might be worth an experiment, but the solvents are nasty and probably won't result in a cosmetic win.It would be much more work, but maybe you should experiment with making PWB looking boards of a thermoplastic material, shaping those to fit your design, and then glueing on parts salvaged from your PWB.

author: laneboysrc
author_rank: Contributor
timestamp: July 09, 2018, 05:56:09 am
content: No experience with bent PCBs.How about using flex PCBs? Some of the Chinese PCB houses offer prototyping services. Will be more than $2 for 10 though.In the old days equipment used multiple smaller PCBs, with simple wire links, to get a larger circuit fit into an irregular shape.

author: janoc
author_rank: Super Contributor
timestamp: July 09, 2018, 03:23:04 pm
content: Folks, do read what the OP posted before replying:Quote(emphasis mine).So no, flex PCBs are not a solution (he isn't building a new functional gadget but using the salvaged boards as essentially a decoration).Also bending an 8 (or more) layer laptop motherboard? Good luck with that, that's certainly thicker than 0.4mm ...

author: JonnyBadger
author_rank: Newbie
timestamp: July 10, 2018, 08:19:24 pm
content: Thanks all. I thought it would be a long shot hope fingers crossed maybe could be but probably not gon'na work. Would have been great to just use the boards themselves and not have to add an internal bracket of some kind, mostly to keep the weight down. With a costume piece that goes on the head every ounce counts.Some great advice up there though.Appreciate you guys giving me your time.

author: Raj
author_rank: Frequent Contributor
timestamp: July 11, 2018, 02:27:52 am
content: If it doesn't worktry mac book pcb,those are black,if they get burnt,no one will notice.if that too doesn't work, print a circuit like thing onto a paper and lacquer it to make it shiny.

author: buck converter
author_rank: Regular Contributor
timestamp: July 11, 2018, 02:36:13 am
content: iphone boards bend quite well

author: station240
author_rank: Unknown
timestamp: July 11, 2018, 03:02:29 am
content: You can find small sections of flex PCB inside dead hard drives, its what the heads are wired directly into.Main downside is flex PCB doesn't react well to the heat from soldering, it's a bit of a pain to solder to.Alternatives:a) Chop the PCB and glue back together with 2 part epoxy, the boards are made with epoxy anyway so should glue ok.b) Fake it by printing two shades of green onto paper, not sure if you'd want grey or metallic (silver/gold) look for the solder pads.c) Delaminate a multi layer PCB. A PCB with 4 or more layers, has the outer most layers glued on later, so those layers are very thin fibreglass. Heat is one way to de-laminate PCBs.

author: helius
author_rank: Super Contributor
timestamp: July 11, 2018, 03:54:30 am
content: It must be possible, because it has been done before. The famous "egg" in Mountain View, CA is made of bent circuit boards.(Not at 90 degrees!)

author: janoc
author_rank: Super Contributor
timestamp: July 11, 2018, 07:07:02 pm
content: Quote from: helius on July 11, 2018, 03:54:30 amThose are fairly small angles and that installation obviously has some internal structure the boards are screwed/riveted to that helps it to stay put despite the stresses on the boards. But that's nowhere near to what OP wanted to do.

author: jpanhalt
author_rank: Super Contributor
timestamp: July 11, 2018, 08:24:54 pm
content: I disagree with those who say epoxy is not a thermoplastic. It is and every single type has a Tg (glass transition temperature). It will melt before it decomposes. I believe FR4's Tg is around 140°C to 160°C. It is not worth looking up as there are different kinds. The TS can do that. The problem with FR4 is the fiberglass in it which has a much higher Tg. Thus, you can bend FR4 and heat facilitates doing that, but the angle of bend is limited by the glass fibers embedded in it.If you want to make an egg, no problem. If you want to make a box with bent edges, you will have a problem. However, you can make a box using freshly mixed epoxy for the edges.

author: KL27x
author_rank: Super Contributor
timestamp: July 11, 2018, 09:27:20 pm
content: To keep bulk and weight down, perhaps patch them from the back with a layer of fiberglass cloth and Bondo from the autoparts store.I could make 90 degree V groove just through the PCB on my tilting router table. For esthetic purposes, the PCB would match up perfectly around the 90 degree joint. If the bottom were flat/depopulated, anyhow.