Hi,

 Crimping after solder is a terrible idea. You are going to shear the solder
at the copper and terminal surfaces. Solder simply has very little strength
compared to the other materials.

 Solid wire will not crimp into a tight robust joint. Soldering is about all
you can do. Or switch to a fine stranded wire.

Bob K.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Nutting
Sent: Wednesday, October 24, 2012 4:45 PM
To: [log in to unmask]
Subject: Re: [TN] Crimping to AWG 8 solid magnet wire

Richard,

I don't have any data to support or refute this.  The idea of soldering the
wire BEFORE crimping goes along with the notion of the leaded solder
"relaxing".  If the soldering is done AFTER crimping I don't think there
will be solder relaxing as you had a good mechanical crimp before you
unnecessarily added the solder.  If someone says to me they are worried
about the solder melting I remind them that for the solder to melt it will
require a very high temperature and it is a safe bet they have a bigger
problem to worry about.

Phil

-----Original Message-----
From: Stadem, Richard D. [mailto:[log in to unmask]]
Sent: Wednesday, October 24, 2012 3:28 PM
To: TechNet E-Mail Forum; Phil Nutting
Subject: RE: Crimping to AWG 8 solid magnet wire

Hi, Phil
I understand and totally agree with you and Steve, soldering stranded wire
and then crimping is a bad idea.
The original reason was that the leaded solder would eventually relax and
cause the crimp to fail.
However, is that still true with lead-free solder?

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Nutting
Sent: Wednesday, October 24, 2012 10:35 AM
To: [log in to unmask]
Subject: Re: [TN] Crimping to AWG 8 solid magnet wire

Gerald, et. al.,

Maybe this is a case of "if some is good, more has to be better".
Presumable the manufacturer has tested their terminal successfully at 60
psi, but did the end user not use the same gauge and type wire as the
manufacturer tested.  Maybe someone assumed that more pressure would make a
better joint and the idea stuck... "we have always done it that way".  Solid
and stranded of the same gauge will actually have different wire diameters.

Some folks will assume that by soldering they make a better connection.  Not
the case.

Some folks will say that they have to handle a lot of current so it needs to
be soldered.  But the wire/lug combination can only handle the amount of
current it is rated for without potential for failure.

The only place we use solder with crimps is when terminating Litz wire.
Litz is a whole bunch of fine enamel coated wires that each strand must be
stripped to make a connection.  Chemical stripping and solder pot immersion
are the only possible solutions.  Solder pot stripping is the most
environmentally and manufacturing friendly.

Years ago we crimped and then soldered our terminals.  Bad practice!  I have
converted our staff to agreeing that crimp and solder is incorrect.  The
theory is that if the wire/lug combination has been properly sized and
properly crimped that it will make a gas tight mechanical weld.  Adding
solder does two possible detrimental things, flux wicked up the wire (not an
issue for solid wire) and it makes the wire more susceptible to breakage due
to wire fatigue (not an issue for solid wire).  Several years ago this
discussion came up and I had Steve Gregory post a document that I had gotten
from Amp that clearly stated that soldering was bad practice and it outlined
exactly what I have listed above.

Just my opinion though.

Phil Nutting

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Gerald Bogert
Sent: Wednesday, October 24, 2012 10:26 AM
To: [log in to unmask]
Subject: [TN] Crimping to AWG 8 solid magnet wire

October 24, 2012



IPC/WHMA-A-620 includes the following requirements pertaining to crimping to
solid wire.



a.     Crimping to solid wire is not allowed except for connector center
contact.

b.     Crimp tool cycle must be completed.



We have an OEM who crimps a solid AWG # 8 gage magnet wire (stripped to
remove insulation) to a standard AN-8 (T&B) NAVY type terminal lug using a
manual hydraulic crimp tool that has adjustable pressure settings.  If the
crimp is performed at 90 PSI, one gets a complete tool cycle which leaves a
deep crimp impression on the top surface of the lug and the # 8 impression
on the reverse side of the lug.  One can see a bell-mouth at both ends of
the lug.  If a 60 PSI setting is used, the crimp forms and one can see two
small crimp impressions on the top of the lug but nothing on the back side
of the lug.  Both settings result in the lug barrel forming around the OD of
the stripped magnet wire.  The OEM uses the 60 PSI setting because of the
concern of over crimping at the 90 PSI setting resulting in possible damage
to the wire.  At one time the lugs were brazed rather than crimped but this
process caused some lugs to crack so they changed from braze to crimp.



The contract drawing also mandates that the lugs be soldered after crimping
and that the solder must flow to fill any voids inside the lug barrel.



Based on the above, I have the following questions that I would appreciate a
response to:



1.     What is the technical basis for not allowing crimp to solid wire
for any solid wire other than for connectors and why would we not have the
same concern for connector crimp?

2.     Would one expect solder to flow into the ID of the lug with the
60 or 90 PSI settings?

3.     Assuming the 60 psi crimp is pull tested and passed, is this a
technically acceptable crimp?  If not, why not?



[log in to unmask]


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