Hi Paul - is it possible that you have a flux "bubble" due to flux
evolution that prevents solder from getting to a pad?  You lost me on the
flux you are using - is it a type R (sorry TechNet, I know that
nomenclature is no longer valid)? What is a SM/NA flux? The flux bubble
theory would explain the randomness that you are seeing - there has been
flux evolution issues in the past that have resulted in some of the wording
currently found in the ANSIJ-STD-002/003 specifications. Good Luck.

Dave Hillman
Rockwell Collins
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[log in to unmask] on 04/16/98 10:22:57 AM

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To:   [log in to unmask]
cc:    (bcc: David D Hillman/CedarRapids/Collins/Rockwell)
Subject:  [TN] FAB: Ni/Au Solderability test




Hello all,
Our standard solderability test for HASL or Reflowed Tin-Lead finish is
5 seconds at 235 C (455 F) using non-activated SM/NA Flux on a static
solder bath. We are seeing odd instances of missed pads on Electroless
Nickel/Immersion Gold finish where the solder has not touched the pad at
all.
This only occurs on random isolated pads, sometimes one in a row of SMD
pads, and I am wondering whether the test parameters should be slightly
different for this finish or if there is a problem with the test rig.
The majority of pads have tinned and solderability on these is very
good.
Any input on test parameters used elsewhere would be appreciated.
--
Paul Gould
[log in to unmask]
Isle of Wight,UK
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