Quick and dirty strain relief for a wire soldered to a PCB 1

[Matt137]

Hi all,
I have a stranded wire soldered to a PCB, 22swg or thereabouts. The wire is likely to see a limited amount of moving around, because it is attached to a battery cover, so everytime the product's batteries are changed (maybe once every 6 months), the wire is going to get wiggled about. I'd like to put a bit of strain relief on it - but I'm wondering if anyone has any suggestions for a dirt-cheap strain relief option, suitable for manufacture, just to protect the soldered joint? At the moment I'm thinking hot-melt, but having a nice leaky hot glue gun in an assembly environment is not ideal. Black tack would be convenient, except it stays sticky. Bootleg ferrules are also an option, but that's more time and cost...

any tricks of the trade?

thanks,
Matt

 

[IRstuff]

If you are only concerned about the strain on the joint and not the wire, then just plain old epoxying the wire to the board should work; not clear it's any better or worse that hot glue, other than room temp processing. Alternately, you could add a couple of holes to the board and thread cable lacing through them to tie down the wire.

TTFN (ta ta for now)
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[MacGyverS2000]

Non-corrosive epoxy is the proper method for protecting the solder joint, though it won't do much for strain relief on the wire itself. I would use a drop of epoxy right at the solder joint, then some rubber-based compound on top for a small amount of strain relief.

Dan - Owner

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[LionelHutz]

I would suggest you just put another un-plated hole right beside the solder pad and then first pass the wire through that hole before soldering it to the board.

 

[btrueblood]

Better in some ways than epoxy would be a uv-cure adhesive (faster cure means less wait time, less mess from drips/runs). Downside is the risk of some idiot frying an eyeball from the uv lamp. Lionel's idea is a good one, but i've seen the wire insulation get worn through from the abrasive fibers in the pc board chewing through it - so again, a drop of adhesive there would be of help.

 

[itsmoked]

Hot Melt like is done a bazillion time a day in electronics production. Use a non-leaky gun. No expensive chemicals, no mixing, no waiting, intuitive. And, with a slight amount of give providing some wire protection.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LionelHutz]

The desire was for a dirt cheap and limited amount of movement strain relief and a hole will work for that.

 

[Matt137]

Thanks all. A hole would resolve things, but the PCB is laid out and we're quite a way down the road now, so I'm loath to re-open that wound.
I've also learned the phrase "glob top" . For now I've gone with hot melt, but thanks to you all I've got a few more options to consider.

Cheers!

 

[itsmoked]

I've done hole-in-the-board weaves several times. They are truly a slow PITA to assemble.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[arcadebench]

Do you have control over the box design? Maybe add a couple of gnarled posts and thread the wire between. Or add a hitch and a small zip tie?

 

[biff44]

no not hot melt glue. that will be rigid and just peel off the board.

use an RTV type of glue. make sure there is some RTV attached to the wire insulation AND the circuit board, or whatever you are soldering this wire too.

then, just as important, make sure the wire has some stress relief in it. you do not want it taut, as thermal contraction will then pull the RTV off the board.

Flexible copper wires can flex millions of times. but flexin that same wire right at a solder or crimp connection will work harden the copper metal and it will fail.

if this is a high vibration application, also make sure that wire is tied down along its length periodically too, so it does not resonate and tear itself off