How to solder very thin stranded wire?

[Jamie]

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

 

[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