From: "Marvin Kaye" <marv@lancaironline.net>
Subject: Re: To solder or not to solder, that is the question
To: lml
Date: Sun, 21 Jan 2007 14:44:56 -0500
Message-ID: <web-1781412@logan.com>
In-Reply-To: <0BCBD581-4D00-4AA1-9947-1CECFF7B42AC@adelphia.net>
References: <list-1780732@logan.com>
 <0BCBD581-4D00-4AA1-9947-1CECFF7B42AC@adelphia.net>
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Posted for Gary Casey <glcasey@adelphia.net>:

  With a great deal of trepidation I'll take a slightly opposing view -  maybe
more of a glancing view, as I don't actually disagree with any  of the
previous posts.  There appears, at least to the average  builder like me, no
attempt made by the manufacturers to standardize  connectors in our aircraft.
  Consequently, to do an adequate job of  crimping the terminals one would 
need
maybe thousands of $$ of  crimping tools.  People who do large volumes of
crimped connectors  eschew even expensive manual crimpers, saying they still
allow for  variability.  Soldered joints can be made to be reliable, but it
  takes some skill and practice; fortunately not money.  I crimped  those
connectors for which I had what I considered to be an adequate  crimp tool,
but soldered the others, which meant most of them.  The  same is true of
splices.
  
  At my day job we solder perhaps 200K joints a day and we found that  the
control of heat and time is the key.  Solder will wick up a  stranded wire,
making it rigid and therefore prone to failure only if  the wire is above the
melting point of the solder.  If the wire  extends through the crimp portion
of the terminal and is exposed (as  is the case for Faston terminals)
soldering is fairly  straightforward.  With a hot iron (how hot?  not sure,
but certainly  above 400F) touch the iron to the terminal near the wire end.
  It can  touch the wire end, but that isn't necessary.  It takes a tiny bit 
of
  solder to enhance the heat transfer at this point of contact.  Apply  the
solder to the tip of the exposed conductor and as soon as the  solder wets the
wire and terminal remove the solder and heat.  Don't  wait for the solder to
fully wick into the joint - the solder is only  there to guarantee electrical
contact, not to provide mechanical  strength.  To make a nicer looking joint
and remove any solder balls  that might inhibit the terminal from going into
the connector give  the terminal quick flick to fling off the excess solder.
  The bottom  line is that the wire that goes into the terminal is never 
heated
  above the melting point of the solder, preventing solder from wicking  back
into the wire.  Time is very important - the terminal should be  heated above
the melting point for the shortest possible time as  anything more than 1.5
seconds starts to degrade the joint and makes  wicking into the wire more
likely.  The same basic technique can be  used for wires than aren't exposed,
such as those that go into a  "solder pot" type of terminal.  Heat the
terminal, NOT THE WIRE, and  touch to solder to the wire/terminal interface
after the terminal is  hot and then immediately remove the heat.  I usually
pull the wire  slightly out of the joint so there is some bare wire exposed
and then  after the solder melts and fills the joint I push the wire in the
  rest of the way at the same time I remove the heat.  Only the tip of  the
wire will then be above melting temperature, avoiding wicking.
  
  Also, as many have said, the strain relief is the key to durability  and any
terminal without one built in has to have something done to  provide strain
relief.  What I do for any connector exposed to  vibration, even if it has a
good strain relief, is to double over the  wires (make into an "S" with the
connector in the middle) and tie the  wires back to the connector body.  I am
willing to splice wires with  solder and I do it "end-to-end" by spreading the
strands a little and  then pushing the wires together.  Solder is applied to
the point  where the wires connect, but again very quickly so that the solder
  won't wick past the actual connection.  Then the spice is doubled  over and
the shrink tube previously slipped over one of the wires  (you did remember to
do that, didn't you?) goes over the whole  thing.  Finally the wire is tied to
the bundle to keep it from  moving.  For connectors with clamp-type strain
reliefs the trick is  to slightly push the bundle into the connector before
tightening the  clamp to ensure that none of the wires has any stress on it at
the  terminal.
  
  Just a suggestion,
  
  Gary Casey