Date: Wed, 7 Nov 2012 15:05:29 -0500
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
In-Reply-To: <5099DE17.40209@flatsurface.com>
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Hi Mike,
At 11:05 PM 11/6/2012, Mike S wrote:
>Common 60/40 has a tensile strength of around 535 kgf/cm², 3.5% silver
>solder, about 580. Not that much difference. The important thing is to
>ensure the joint is properly wetted, and keep the joint stationary while
>cooling. Using a eutectic alloy (63/37) almost eliminates the issues
>cause by movement.
I agree that a joint that's moved while in the
mushy zone is a bad joint, period.
I'm a huge believer in 63/37 solder, wonderful
stuff. There's a jeweler's low-temp solder
called Tix, costs a fortune. Do you know anything about it?
You have an interesting point about the
non-eutectic solders needing to have the joint
mechanically secured while they go through the plastic zone.
>Mechanically, a proper soldered joint of equal overlap (and no twist)
>will be stronger than a non-soldered WU splice with stranded wire, so it
>should be apparent where the strength comes from. WU splices are really
>only effective on solid wire, which shouldn't ever be used in an
>automotive environment.
Yes, I wasn't thinking about how much less
integrity the WU splice has in stranded wire.
I take your point, I think. My concern about
solder joints has never been about tensile
strength but rather fatigue tolerance. A prime
example is in the 022 ECU, where the boards are
joined by a couple of say 20-pin flattened wire
interconnects with paper insulation. The length
is such that they form an S curve and exert a bit
of pressure shoving them into their connecting
through-holes. I can't imagine these things
weigh more than a couple grams, but they are
pulling themselves out of the boards
nonetheless. There's no thermal cycling to speak
of so I can only put it down to vibration.
Now whether this is really an issue with two
wires soldered together in-line is another
question and I don't know the answer. I am
concerned about it in a high-vibration
environment like a car, but I'm more concerned
with the hard spot that the solder leaves when it
wicks up into the strands. For these reasons I
personally am leery of solder joints under these
conditions, though I'm very fond of solder in
general. My habit when working in salt water was
to seal the ends of crimp connections with
multiple coats of "Liquid Electrical Tape" which
is a vinyl compound, and I never had a joint fail
in many years (whereas every single unprotected
crimp fitting on the boat corroded completely off
where the wire entered the crimp. However here is
an alternate view.
http://yachtpals.com/marine-electrical-9162 It
must be stressed of course that a cheap crimp
connector is useless, and insufficient crimping force likewise.
Yours,
David
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