Gregg,

I just looked for and can't quickly find my copy of an Amp document that explained the reason for not tinning and then crimping.

Basically they said that with a properly sized wire barrel for the wire to be crimped and using the correct tool that is calibrated you get a gas tight mechanical weld.  Pre-tinning will increase the likelihood of a wire failure where the solder ends on the wire strands.

Another way to look at is the additional labor cost of tinning and then removing the flux prior to crimping.  Using an OA or other active flux is a failure waiting to happen from flux wicking under the wire insulation.

We make one exception regarding tinning before crimping and that is for Litz wire that must be chemically stripped or dipped in a solder pot to remove the enamel from each wire strand to enable an electrical connection.

Hope this helps.

Phil Nutting

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Gregg Owens
Sent: Tuesday, May 31, 2011 1:24 PM
To: [log in to unmask]
Subject: [TN] Tinning Stranded Wire - Crimped Connections

Dear Technetters:

I have been posed a question I can't answer. In both the IPC-A-610 and IPC-A-620 require that stranded wires used for crimp connections NOT be pre-tinned with solder. Okay I get the requirement, but does anyone know why this is a requirement. Pre-tinning keeps the strands together, so there is some push-pack on why this is a requirement. Any thought appreciated.

Gregg Owens


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