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March 2002

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Date:
Mon, 11 Mar 2002 08:20:25 -0600
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Hi Moonman! One potential source of contamination would be a soldermask
residue remaining on the pads after the soldermask application (due to a
fabrication oops) prior to the application of the ENIG. Depending on your
ability to get a reasonable sample, you can use FTIR analysis to determine
if soldermask residue is remaining on the nonwetted pads. Good Luck.

Dave Hillman
Rockwell Collins
[log in to unmask]





Earl Moon <[log in to unmask]>@ipc.org> on 03/11/2002 05:57:13 AM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
       to Earl Moon <[log in to unmask]>

Sent by:    TechNet <[log in to unmask]>


To:    [log in to unmask]
cc:

Subject:    Re: [TN] ENIG AND NON WETTING


Daan,

As always, I appreciate your input. To clarify, the boards were freshly
received from a major international supplier. I instructed our assembly
house (the same major international supplier - how about that for strategic
planning as the same boards, in volume will be, guess what, assembled by
the
same major international supplier in another location) to reflow and wave
solder the solder samples. The supplier wave soldered the side in which I
had little interest. It was the SMT side, with all the little bastard TI
CSP's that held the most interest for obvious reasons or that should have
been obvious to all as it's all I've been yacking about for two months to
you all and all prospective suppliers.

I got the wave results last week with the non wetting as I described. The
wave solder process was "normal" to the major international assembly
operation with flux type, flux application, conveyor speed, wave types,
wave
height, preheat temps, solder temp, and all the other stuff we all know and
love about wave soldering and its process management requirements.

The board showed, clearly, non wetting on some bottom side SMT pads, at
about 50% non wetted. It also showed, clarly through hole pads about 50%,
by
quantity, non wetted with some obviously adhacent.

My question, again, is what in the ENIG, over bare copper after SM
application, is possibly affecting this type solderability. It's a mystery
worth more investigation.

Again, thanks Daan and I hope I clarified.

Earl

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