Usually for enamel stripping/tinning like this a low tin content (40/60,
even 30/70) is used, this avoids problems of embrittlement, necking and so
on caused by the rapid dissolution of the copper into the tin at the high
operating temperatures. Drossing should also be reduced if you use an
electronic grade, (low tin alloys are commonly used in non electronic
applications).
Kind Regards
Mike Fenner
Applications Engineer, European Operations
Indium Corporation
T: + 44 1908 580 400
M: + 44 7810 526 317
F: + 44 1908 580 411
E: [log in to unmask]
W: www.indium.com
Leadfree: www.Pb-Free.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Mike DiGiacomo
Sent: Wednesday, July 10, 2002 2:51 PM
To: [log in to unmask]
Subject: Re: [TN] Tinned wire breaking
Hi Phil,
Having used Litz wire the past 4 years, I completely understand your brittle
wire situation. We to used a solder pot to tin the wire. I attribute the
brittleness of the wire to the enamel on the individual Litz wire strands.
During the tinning, I think the enamel reflows and the strands become a
single brittle mass.
Maybe you could try using a heat sink around the wire during tinning to stop
heat from running to far up the wire causing the embitterment.
Hope this helps,
Mike Di Giacomo
Process Development Engineer
microHelix Inc.
Portland, Oregon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Phil Nutting
Sent: Wednesday, July 10, 2002 5:37 AM
To: [log in to unmask]
Subject: [TN] Tinned wire breaking
Good morning,
In many of our designs we use Litz wire. To make a connection with Litz
wire the enamel coating from each strand must be removed. Historically we
have used a small solder pot to tin the ends of the Litz wire. Currently we
have a situation where these tinned wires (about 20 AWG) are breaking when
bent around a turret connection. Initially we thought it was due to the
solder pot having been turned up too high, but I just ran some tests with
the pot at normal temperatures and the wire is still brittle. (Gee, what is
my "standard" temperature.... just measured it at 900°F.... oops, that's a
little high).
What temperature do you folks run small solder pots at? Should I be in the
700-750°F range?
Are there any other thoughts on why the wire is so brittle?
Thanks in advance,
Phil Nutting
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