Author Topic: Soldering stranded wire to a flat surface?  (Read 7171 times)

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Offline lpc32

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Soldering stranded wire to a flat surface?
« on: August 10, 2014, 11:55:04 am »
I have a powerstrip that needs fixing. Instead of using a decent mechanism to grip the wires, the stranded wire end was pressed in a metallic tube, and that was, maybe, brazed:


What's a good way to reattach a stranded wire to that flat golden strip?

Is the metallic clamp on the wire end supposed to help with solderability, or is it just to clamp the strands?
 

Offline SeanB

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Re: Soldering stranded wire to a flat surface?
« Reply #1 on: August 10, 2014, 12:05:56 pm »
Looks like the original method was to crimp the wire in a ferrule and then use a spot welder to weld the brass tube to the brass strip. Without acess to a spot welder the only method that will work is to use either a brazed joint or silver solder, as a soft soldered joint ( plumbers solder or ant electronics solder) will fatigue loose with time. There you need a hard solder joint for reliable life.

Best is to throw it away ( or scrap for the brass content as well) if you do not have brazing rod and flux, or silver solder rods, either self fluxing ( used for airconditioning) or with a flux coating. There you need a gas torch to provide the heat, as no soldering iron will get that hot, except possibly for the big 300W soldering guns with massive tips.
 

Offline grumpydoc

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Re: Soldering stranded wire to a flat surface?
« Reply #2 on: August 10, 2014, 01:10:21 pm »
Drill a hole in the strip, attach a solder tag to the wire and then attach to the strip with a short machine screw.
 

Offline SeanB

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Re: Soldering stranded wire to a flat surface?
« Reply #3 on: August 10, 2014, 01:41:12 pm »
Do not use a self tapping screw though, use a brass screw, star washer and a nut. A self tapping one will come loose with time and arc.
 

Offline romantronixlab

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Re: Soldering stranded wire to a flat surface?
« Reply #4 on: August 10, 2014, 04:21:18 pm »
I once had a problem similar, i did got it fixed by dremel drilling a small hole in the broken point, about the size of the wire, tinning it and inserting the wire. Soldering at high heat.
To this day it is still working and its been 4years fixed.
Good Luck on the repair project. :-+
Will think about it.
 

Offline rob77

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Re: Soldering stranded wire to a flat surface?
« Reply #5 on: August 10, 2014, 04:40:28 pm »
looks like a cheap power strip - probably the best way would be to replace it.
but if you need to repair it for whatever reason, then definitely drill a hole to the strip, crimp a ring terminal to the cable and use a bolt + nut + star washer to attach it. - such a crimped and bolted connection will last "forever".
 

Offline David Hess

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Re: Soldering stranded wire to a flat surface?
« Reply #6 on: August 10, 2014, 04:51:23 pm »
Drilling a hole just large enough for the stripped wire through the brass strip should work.  Use a really active flux before soldering and mechanically clean the brass.  If you have it, use low temperature silver solder which is much stronger that normal solder.

For low temperature soldering to brass, I like to use Kester's Copper-Nu as a flux but dilute hydrochloric acid is good also.

One risk of using low temperature solder besides its low mechanical strength is its low melting point.  That looks like part of a power socket so if a power plug was loose and the strip got hot enough, the solder could melt.
 

Offline rob77

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Re: Soldering stranded wire to a flat surface?
« Reply #7 on: August 10, 2014, 06:44:00 pm »
That looks like part of a power socket so if a power plug was loose and the strip got hot enough, the solder could melt.

and exactly that's the reason why you need a bolted/crimped/weld joint instead of a solder joint. in many countries it's even prohibited to have solder joints on mains installation/cables.
 

Offline VK5RC

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Re: Soldering stranded wire to a flat surface?
« Reply #8 on: August 11, 2014, 01:05:46 am »
I note the above comment re not soldering mains,  which I think is the case in my state,  the strange part is if the socket strip gets up to 200 C,  wouldn't all the plastic give way as well? I would solder it for use at home but not for use at work.
Whoah! Watch where that landed we might need it later.
 

Offline Psi

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Re: Soldering stranded wire to a flat surface?
« Reply #9 on: August 11, 2014, 06:20:04 am »
Personally, as far as safety and reliability goes, i would trust the generic lead 60/40 soldering skills of an electronic engineer more than i would trust china's spot welding skills on a $1 powerboard.

If it was me I would..
- Drill a small hole in the metal plate near an edge, eg 2.5mm (obviously don't compromise any structural part of the metal)
- Strip back a good amount of insulation off the wire, maybe 2cm.
- Use some flux and solder to tin the metal plate around the hole on both sides.
- Thread the wire through the hole and twist it around itself nice and tight.
- Solder the joint.

This may not be legal for some countries, but personally i would trust that joint more than the joins in a brand new china power strip.
The fact that it failed in the first place means it wasn't done right.
« Last Edit: August 11, 2014, 06:44:28 am by Psi »
Greek letter 'Psi' (not Pounds per Square Inch)
 

Offline george graves

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Re: Soldering stranded wire to a flat surface?
« Reply #10 on: August 11, 2014, 06:52:57 am »


And as someone mentioned a star washer, or maybe loctite?  Does anyone use loctite on in electronics?  Haven't heard it mentioned here much(at all).




Offline andtfoot

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Re: Soldering stranded wire to a flat surface?
« Reply #11 on: August 11, 2014, 07:10:00 am »
And as someone mentioned a star washer, or maybe loctite?  Does anyone use loctite on in electronics?  Haven't heard it mentioned here much(at all).
I use Loctite all the time on stuff.
I think the other reason for the star washer though is so it bites into the surface, past any oxidation, to make better contact.
 

Offline VK5RC

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Re: Soldering stranded wire to a flat surface?
« Reply #12 on: August 11, 2014, 09:22:31 am »
Use locktite or an equivalent (low strength) a lot of the time, the damage that a loose metallic nut can do to an electric circuit is worrying.
Whoah! Watch where that landed we might need it later.
 

Offline lpc32

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Re: Soldering stranded wire to a flat surface?
« Reply #13 on: August 11, 2014, 12:23:36 pm »
Thanks everyone!
 


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