The correct way to solder Litz wire

[dave]

Anyone know the proper way to solder Litz wire (used in eg quality headphones). My home-grown (but probably incorrect) method is to strip the outer conductor, expose the strands to a gas flame for fraction of a second to remove the varnish layer (or whatever it is), use a clean cloth soaked in alcohol to remove the soot (sometimes even very fine emery cloth!), and then solder. Even this though sometimes fails when a substantial woven cotton filler exists. Is there a "correct" or better way? Thanks

[Andrew Mawson]

Well that's the way I've always done it - and it seems to work !

AWEM

[Broadback]

I was an apprentice in the RAF before Pontius Pilot got his wings, we were taught to dip the wire in meths then set it alight, it worked.

[Dave Liquorice]

Crimp...

[Ian Stirling]

It's not Litz. Litz has a special 'weave', the copper in headphones has no particular arrangements.

You may find that in some cases, the filler is kevlar, which is rather hard to burn. I find that a relatively long period in a cool flame works.

[dave]

On some (many) connectors this is impossible.

[dave]

Reason for post is that I've had to make up some cables just recently and the amount of filler and the "fineness" of the strands are proving difficult to make a clean solder joint. I'll try the meths suggestion. Thanks.

[Dave Liquorice]

They are the wrong connectors for the wire then. B-)

You could of course crimp a ferrule onto the end and solder that.

[Tony Williams]

Our wiring shop, (mumble,mumble years ago), handled Litz wire daily. The approved stripping method was a meths lamp, then wipe away the carbon with isopropyl.

[Tom]

(Extract from Journal of Scientific Instruments 19, p79 1942) by D.A.Bell Bsc, AMIEE. The usual method of cleaning insulation off the end of a length of Litz wire is to make it red hot and then quench in alcohol; this removes both silk and enamel insulation from the individual strands, and leaves them all bright and in a condition to solder. This method becomes difficult, however, if the whole stranded cable is of a very small section (e,g. 3---46's), for two reasons: first, owing to the small ratio of thermal conductivity along the cable to surface exposed to the flame, the wire tends to reach a higher temperature than a thicker cable would, and it's temperature rises so rapidly that it is difficult to control, by choice of position in the flame; and secondly, owing to the small ratio of mass of copper to exposed surface, it is impossible to avoid cooling of the wire between the flame and the alcohol bath, and the oxide on the surface of the wire is then not reduced. The remedy is----?

To follow if really interested. :-)

Tom

[Rob Morley]

Go on then

[Ian White]

Hang on... all these methods involving alcohol and flames were intended for litz wire that used old-fashioned brown enamel.

The OP's litz wire is far more likely to be the modern pink stuff that uses a 'self-fluxing' polyurethane enamel. This can be stripped and tinned in a solder bath - or more likely, by holding it in a big drop of molten solder on the end of the bit. Let it stew for several seconds until the fumes have stopped (the fumes are toxic) and then feed in an extra bit of cored solder. The litz should come out with a bright, solidly tinned end.

Different again is tinsel wire, which uses a foil conductor supported on plastic fibre cord. Because the plastic melts very readily, tinsel wire can only be crimped into a tiny ferrule, or twisted into a copper wire that has already been soldered to the termination... nasty, fiddly stuff.

[Tom]

I did wonder whether it was relevant in this day and age, there have been so many advances in enamel and fabric type insulation, however, for the sake of completeness:

The remedy is to wrap the thin wire which is to be cleaned round a piece of solid copper wire, say, 26 or 30swg, and subject the combination to the usual treatment. The thicker wire provides the necessary thermal time constant and stability, and in practice does not prevent the cleaning of the side of the thin wire which is in contact with it. With this method it is possible to clean even a single strand of fine wire by the heat method. From the book-- Laboratory and Workshop Notes. Compiled and edited by Ruth Lang, PhD, A Inst P, for the Institute of Physics. pub 1949

[Andy Dingley]

Why would headphones need Litz wire ?

Anyway, you _must_ tin it first. After that it's easy. A solder pot is the best "production" way, but otherwise just apply any sort of gas flame briefly, then try tinning as usual.

Practice first, because it's hard to judge the length that gets stripped by the flame.

[Roly]

If it's a pair of headphones, then as Rob Morley says, it's tinsel wire rather than Litz wire.

Tinsel wire is bastard stuff to solder and you should really crimp it, but if there is no alternative, I find that tightly wrapping a long strand of copper wire around it and soldering to that will do the job fairly well. It's often neater to wrap a longer bare bit that you need and then cut it to length.

It's not the recommended way to do it, but sometimes a repair can't be done the recommended way.