Attaching 28g wire to PCB? - Page 1
Forum section: electronics / beginners

author: Tom18991
author_rank: Contributor
timestamp: May 06, 2025, 04:15:57 pm
content: I need to attach tiny little stranded wires -- I think 28 gauge -- to a printed circuit board. The wires come unterminated with component I'm incorporating into my project. For far, I've just been soldering them to pads on the PCB, but doing that makes them highly vulnerable to breaking off. The wires are so small, crimping tiny connector pins seems impractical without farming it out. Right? I plan to make about 100 of these boards (4 wires per board) so looking for a technique that won't be super time consuming (like soldering on a pigtail with machine-assembled connector). Any ideas? Thanks!

author: Grandchuck
author_rank: Super Contributor
timestamp: May 06, 2025, 04:26:30 pm
content: Heat shrink tubing might give a bit more strength.

author: edpalmer42
author_rank: Super Contributor
timestamp: May 06, 2025, 05:28:08 pm
content: More info required.How long are the wires? Is the component attached to the board? Is the component fixed or does it move relative to the point where the wires attach to the board? Picture?

author: tooki
author_rank: Super Contributor
timestamp: May 06, 2025, 06:05:15 pm
content: You have a few options, here's a selection:- solder, but provide strain relief. One way is to add one or two holes (2 is better) per wire on the PCB, so that you thread the wire through the holes, providing strain relief. I've done this so many times, I felt like I was a tailor at work, not an electronics technician!If you can't modify the PCB layout, you might be able to provide strain relief with a glob of silicone or similar adhesive, like SMP, or by carefully tacking a bit of the wire down with a strong adhesive, like the tough black superglue, epoxy, or some kind of UV-cure adhesive. In both cases, you still need to avoid heavy flexing.- crimp, but with a connector that isn't super tiny. For example, Molex Micro-Fit 3.0 goes down to 30AWG. With the correct crimp tool, it's easy. I've done plenty of 28AWG into standard 0.1" header contacts (Mini-PV, "Dupont", etc.).- use something like screw or spring/cage clamp terminals, using a wire-end ferrule. You can get some ferrule crimpers that do 28AWG. Otherwise, I'd strip the wire a bit more than double what's used for the ferrule, then fold the wire back to double its cross-section. (Doubling 28AWG gets you to just a bit thicker than 26AWG.)

author: tooki
author_rank: Super Contributor
timestamp: May 06, 2025, 06:07:02 pm
content: Quote from: Grandchuck on May 06, 2025, 04:26:30 pmThis can backfire horribly, by applying a ton more force onto the thin wire. It helps only if it can cover the entire solder joint, preventing flexing at the solder joint. Otherwise it just makes things worse.

author: tooki
author_rank: Super Contributor
timestamp: May 06, 2025, 06:08:42 pm
content: Also, if it's an off-the-shelf component that is available from Digikey, inquire whether they can simply crimp connectors for you. I seem to recall that they offer that service for some parts at minimum.

author: Grandchuck
author_rank: Super Contributor
timestamp: May 06, 2025, 07:14:51 pm
content: Quote from: tooki on May 06, 2025, 06:07:02 pmI disagree. Depending on the wire metal surface, there will be more or less wicking of the solder. If the tubing could cover the juncture where the wicking ends, it could add some strength. More info is needed.

author: Tom18991
author_rank: Contributor
timestamp: May 06, 2025, 10:17:51 pm
content: Quote from: tooki on May 06, 2025, 06:05:15 pmThank you -- this goes a long way toward validating my intuition. The wires and pcb will be fixed in place once the device is assembled, so it's not like the wires will be routinely moved/flexed. I tried screw terminals, but these are wires off a strain gauge being fed to a 24-bit ADC, and the ADC was able to pick up changes in resistance as the wire moved. Did not try a ferrule though, so that might help, although I wasn't keen on the space needed for the screw mounts. I thought about adding two holes in front of the solder pad and threading the wire under and up before soldering, but thought it was just another of my hillbilly ideas... If that's a thing, and works, that might be the ticket. My other thought was to add a little plank/tab on the board for the solder pads and then secure the whole tab with adhesive lined heat shrink such that the flexible part of the wire is encased by the glue in the heat shrink, but if the strain relief holes work, that sounds like a cleaner option with less PCB real estate wasted. Very much appreciate your post, thank you!

author: coppercone2
author_rank: Super Contributor
timestamp: May 06, 2025, 10:35:37 pm
content: 28 awg wire is fine to crimp if you have the right crimp tool if your hands are reasonably steady and I would recommend this is the strongest way because the crimp will bind to the insulation.You can do 100 of them by hand with a crimp tool (i.e. molex), thats not super bad. SO long its not weekly. It does not take long once you get the hang of it. 1 hours of work (or probobly much less) if its just crimping free wires. Cables are much harder because you can't mess up and its harder to work with (lets say if you strip a cable and have 0.5 inches of wire to work with before the crimp). But if its just loose wires then you will be fineBut I think its exhausting mentally from a strain/steadyness prospective so you don't want this to be regular work

author: tooki
author_rank: Super Contributor
timestamp: May 07, 2025, 07:01:18 am
content: Quote from: Grandchuck on May 06, 2025, 07:14:51 pmThat creates a longer lever acting on the solder joint. Not smart.

author: tszaboo
author_rank: Super Contributor
timestamp: May 07, 2025, 08:30:42 am
content: You can crimp AWG28, it would fit into any number of crimps for JST connectors.

author: Psi
author_rank: Super Contributor
timestamp: May 07, 2025, 08:33:51 am
content: You can do the thing where you have some extra NPTH on the pcb where you thread the wire through before soldering. That way it has some strain relief and doesn't flex right at the solder join.The downside is time required to thread each wire through.

author: Haenk
author_rank: Super Contributor
timestamp: May 07, 2025, 11:39:06 am
content: UV curing glue?

author: SteveThackery
author_rank: Super Contributor
timestamp: May 07, 2025, 12:33:28 pm
content: Crimping seems the way to go, but if I need to retain something: a wire connected to a PCB, a large electrolytic, I use a dab of hot melt glue. I think it is better than silicone sealant/adhesive in two ways: first, it sets much more quickly than silicone - just a few seconds; second, it is easy to soften when you need to remove the wire or component - a few seconds with a hot air gun. Silicone is trickier to deal with.