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January 2007

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Subject:
From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Thu, 18 Jan 2007 16:24:41 -0600
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Hi, Jon
I am not sure of the cause, but I assumed it to be outgassing. I do not
think it was caused by the heat alone.
I also know that THHN-type wire was most susceptible to the problem. The
tin-coated wires such as UL 7004 less so, but it still oxidized to the
point where it would not solder easily.
As part of my own business, I used to bring in aviation fueling trucks
and wire them and install either the tank and pump or the hydrant/pump
systems, and then I installed dead-man switches throughout the trucks
connected to a PLC controller. In order to start and drive the truck,
everything had to be in place, the driver needed to be seated, the
brakes off, the hose wound onto the reel, the valves locked, etc. We
used DOD-STD THHN automotive wire, and I recall having a spool of this
wire come in and it was black under the insulation. There were no
outward signs that anything else was wrong with the wire.

I later found out that the supplier had a warehouse fire.

Later in life, I experienced wire turning black after it had been
soldered to circuit boards. It turned out that the CEM used a standard
UL 7004 wire and baked the assembly after it was soldered to cure an
epoxy that was used to hold down the wires. When we went to rework one,
the stranded, tinned UL 7004 hookup wire was black inside of the
insulation. The bake temp was only 65 deg. C. for 4 hours. The same lot
of wire still on the spool showed no signs of oxidation.
Strange things happen.

-----Original Message-----
From: Roberts, Jon [mailto:[log in to unmask]] 
Sent: Thursday, January 18, 2007 4:04 PM
To: Stadem, Richard D.; TechNet E-Mail Forum
Subject: RE: [TN] SHELF LIFE OF STRANDED WIRE

Richard,

First, I thank you. I am also from the old school (actually was an Navy
Civilian Instructor in Indianapolis In working at the Naval Avionics
Center in the late 80s and all through 90s until DoD cancelled the Mil
Standards for soldering. I am glad you reminded all about OA flux and we
do not use that anywhere here.  I did not know about heating of wire can
induce oxidation so is the insulation out gassing causing the oxidation?

Jon

-----Original Message-----
From: Stadem, Richard D. [mailto:[log in to unmask]]
Sent: Thursday, January 18, 2007 3:41 PM
To: TechNet E-Mail Forum; Roberts, Jon
Subject: RE: [TN] SHELF LIFE OF STRANDED WIRE

If the wire is oxidized on the surface to the point where it will not
solder, the surface resistance will be higher and there may be some
reduction in conductivity when mechanically crimped. If they are
oxidized well up under the insulation either they oxidized prior to
insulation application or there was a reaction inside the insulation. If
a spool of wire is heated up over 90 C I know that it can oxidize under
the insulation.

A word of caution: Do not attempt to use a highly active OA flux to
pre-tin oxidized wire, as the OA flux will seep up inside the insulation
and cannot be washed away. Only a no-clean or RMA flux should be used
when tinning wires, and the dwell time in the pot should be of such
length that full activation of the flux occurs. The procedure I was
taught by the old school is to dip the wire in IPA, then dip only the
portion to be tinned (or slightly less) in the flux, and then dip in the
solder such that it wicks up under the insulation a minimum of the wire
thickness. After the wires were tinned they were collectively dipped in
alcohol again to remove as much of the flux residue as possible.
Automated tinning systems are set up to perform the tinning in much the
same manner.

That's my 2 peso's on that.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Roberts, Jon
Sent: Thursday, January 18, 2007 2:02 PM
To: [log in to unmask]
Subject: Re: [TN] SHELF LIFE OF STRANDED WIRE

Thanks for all the inputs.  This is a picture of a purchased item
containing multiple wires that are formed into a fusion lug at one end.
The other ends we strip and some wires are soldered into a connector and
others are crimped to pins.  The wire when looking very dark (almost
black) will not take solder and we use a solder pot. We have cut back up
to 12" and still found unsolderable wire.

We now have come across wire on spools in house that is very dark in
color that was manufactured in 05 and 06 and stored in a controlled
environment for temperature and humidity here.

Main question I have is can you use wire that does not take solder for
crimping operations?

Again thanks for all the responses and will keep watching for anymore
you folks may have.  Jon



-----Original Message-----
From: Dehoyos, Ramon [mailto:[log in to unmask]]
Sent: Thursday, January 18, 2007 11:42 AM
To: [log in to unmask]
Subject: Re: [TN] SHELF LIFE OF STRANDED WIRE

	Older than 2 year spool of wire should still wet with no
problem. There has to be an issue, not enough heat is being used to
solder the wire, or no flux to remove the top oxide layer, real cheap
wire,... Of course the expose ends, specially if in a very humid or
corrosive environment would have to be cut off. A freshly strip  wire
should have a shelf life of many years.
	Regards,
	Ramon
	 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Frederick Miller
Sent: Thursday, January 18, 2007 12:27 PM
To: [log in to unmask]
Subject: Re: [TN] SELF LIFE OF STRANDED WIRE

I would do a "dip and look" test to verify that the wire is wetting.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Jon Roberts
Sent: Thursday, January 18, 2007 11:51 AM
To: [log in to unmask]
Subject: [TN] SELF LIFE OF STRANDED WIRE


Searching for data or information regarding process control to self life
of stranded wire (M22759/32). Wire is used for both soldering and
crimping. We are considering two years from Date of manufacturing (DOM)
from vendor.  
Problem being experience is discoloration (oxidation) of wire surface.  
Considering also using solderablitity criteria to determine if wire is
suitable for crimping.  Any help or information is extremely welcomed.  

Jon

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