How to solder very thin stranded wire?

On Sun, 24 Feb 2013 22:56:59 -0800, the renowned Jeff Liebermann
<jeffl@cruzio.com> wrote:

>
>From the graph, it appears that pure tin is the worst, with 60/40
>being a close second.  However, if there's any copper in the solder,
>the copper wire doesn't want to dissolve.  I'm not sure what's in the
>RoHS solder on my bench.  The label fell off long ago.  I'll find some
>more that doesn't have copper in it and see what happens.
>
>I'll see if I can find some finer wire and try again.  I want to see
>the wire "disappear".

The cheap lead-free stuff I have has 0.7% Cu. 


Best regards, 
Spehro Pefhany
-- 
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
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On Sun, 24 Feb 2013 12:36:51 -0800, Jeff Liebermann <jeffl@cruzio.com>
wrote:

>On 24 Feb 2013 16:47:58 GMT, "Default" <none@noname.net> wrote:
>
>>That is the theory...  If you slowly feed something like 32 or higher
>>AWG wire onto a hot, heavily tinned, tip you can watch it dissapear.  
>
>I just tried it with one strand from 24 AWG stranded wire, which is
>made from 7 strands of 32 AWG.  I held the iron on the wire for about
>5 minutes and nothing disappeared.  Perhaps it's because my soldering
>iron tip runs at about 400 C while copper melts at about 1085 C?

Probably should have said  -   single strand of soft, >= 32 AWG
UNTINNED copper wire as in "solder ez" magnet wire.  32 will dissolve
(I know) and 41 awg is damn near impossible to solder to.  Only thing
that works is "reflow" (tin the part and heat it then touch the wire
to it - or wrap it around a tinned heavier lead with several turns
then reflow.  In production quantities flux the part then a quick dip
in a just-skimmed  solder pot)

There is a real art to soldering fine gauge wire and litz wire.

Jeff Liebermann wrote:
> On Sun, 24 Feb 2013 16:29:46 -0600, John Fields
> <jfields@austininstruments.com> wrote:
> 
> 
>>On Sun, 24 Feb 2013 12:36:51 -0800, Jeff Liebermann <jeffl@cruzio.com>
>>wrote:
>>
>>
>>>On 24 Feb 2013 16:47:58 GMT, "Default" <none@noname.net> wrote:
>>>
>>>
>>>>That is the theory...  If you slowly feed something like 32 or higher
>>>>AWG wire onto a hot, heavily tinned, tip you can watch it dissapear.  
>>>
>>>I just tried it with one strand from 24 AWG stranded wire, which is
>>>made from 7 strands of 32 AWG.  I held the iron on the wire for about
>>>5 minutes and nothing disappeared.  Perhaps it's because my soldering
>>>iron tip runs at about 400 C while copper melts at about 1085 C?
> 
> 
>>It's not so much about the melting point of copper as it about copper
>>dissolving into a molten tin - lead alloy.
>>
>>An analogy might be sugar dissolving into water far below sugar's
>>melting point.
> 
> 
> Thanks.  That makes sense, but I'm still skeptical.  So, I tried it
> again, this time with a thicker #28 bare copper wire on both my 750F
> lead-tin (60/40) iron tip and my 850F RoHS tip.  15 minutes of applied
> heat and I get the same result as before... nothing happened (except a
> well tinned piece of wire and a pile of dross).
> 
> Digging, I found:
> "Properties of Alloys of Multicore.. Solder Wires"
> <https://www.distrelec.cz/ishop/Datasheets/M-POFA_eng_datasheet.pdf>
>     Multicore Savbit Solder is produced especially to
>     overcome the problem of ordinary tin/lead solders
>     dissolving copper. It is an alloy to which a precise
>     amount of copper has been added so that no further
>     copper absorption should take place during soldering.
> 
> From the graph, it appears that pure tin is the worst, with 60/40
> being a close second.  However, if there's any copper in the solder,
> the copper wire doesn't want to dissolve.  I'm not sure what's in the
> RoHS solder on my bench.  The label fell off long ago.  I'll find some
> more that doesn't have copper in it and see what happens.
> 
> I'll see if I can find some finer wire and try again.  I want to see
> the wire "disappear".
> 
Did you first dip the wire tail in acetone to clean off the fibers and
any form of coating on the wire?

  After do so, you then use a small amount of flux..

It has worked for me in the past for types of fine wire bundle in fiber
fillers.

Jamie

Spehro Pefhany wrote:

> On Sun, 24 Feb 2013 22:56:59 -0800, the renowned Jeff Liebermann
> <jeffl@cruzio.com> wrote:
> 
> 
>>From the graph, it appears that pure tin is the worst, with 60/40
> 
>>being a close second.  However, if there's any copper in the solder,
>>the copper wire doesn't want to dissolve.  I'm not sure what's in the
>>RoHS solder on my bench.  The label fell off long ago.  I'll find some
>>more that doesn't have copper in it and see what happens.
>>
>>I'll see if I can find some finer wire and try again.  I want to see
>>the wire "disappear".
> 
> 
> The cheap lead-free stuff I have has 0.7% Cu. 
> 
> 
> Best regards, 
> Spehro Pefhany

  really, the junk I have has 5% in it and it hate it ! ;)

Jamie