Tom -

Wire crimping is not covered by the IPC-A-610 standard. Crimping is covered
by the:

 A-620 - Requirements & Acceptance for Cable & Wire Harness Assemblies

 This standard does have a section on pre-tinning. I would use this
 standard to come up with an acceptable process.






Cheryl Tulkoff
Phone:(512) 683-8586
Fax: (512) 683-8847
National Instruments
11500 N. Mopac Expressway
Building A
Austin, TX 78759-3504





                      Tom Gervascio
                      <tgervascio@SPART        To:       [log in to unmask]
                      ON.COM>                  cc:
                      Sent by: TechNet         Subject:  [TN] Wire crimping
                      <[log in to unmask]>


                      05/12/2004 08:54
                      AM
                      Please respond to
                      "TechNet E-Mail
                      Forum."; Please
                      respond to Tom
                      Gervascio





We have an application where we think we are forming galvanic corrosion
between silver plated wire and exposed copper (from mechanical stripping).
One suggestion that we had was to permit us to pretin the wire with a ROL0
halide free flux, water wash and then crimp on the mating part.  The
response I received was "In response to question 1. No. Stranded wire must
not be tinned when using crimped contact.

There are two reasons I'm aware of: 1. The crimp would not hold properly.
2.
Tinning stranded wire makes it brittle. Brittleness is not an issue at the
CCA end of this wire because it gets potted, but the crimp-connector end is
subjected to movement and vibration. "

Any feedback on this- the application is an high reliability avionics
application and must conform to IPC-A-610 Class 3. I would think that
pretinning the wire would effectively distribute any forces over a larger
cross sectional area (the solder would wet between the individual stands of
wire). I would think that pretinning would not make the wire brittle but
the  downside I could think of- 1.making sure that all flux residues are
out of the joint,
2. the insulation is not damaged by the pretinning,
3. and increasing the resistance of the interconnection

Any information would be appreciated.




Tom Gervascio
Senior Process Engineer
Sparton Electronics
(352) 540-4040

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