Hi Dave - thanks for your suggestion. It is a likely explanation for the
problem we are seeing. The SM/NA flux is a non-activated flux specified for
this test by British Standards which is low in ionics and much less
aggressive than the old flux we used to use (R8 I think). As there is no
pre-heat on the test rig, there are volatiles trapped between the test piece
and the solder which could lead to trapped bubbles on smd pads. This
explains why it does not happen on holes as the gas can escape. What I need
to do is find a way of eliminating this by changing our test method.

Best Regards

-----Original Message-----
From: David D Hillman <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: 19 April 1998 06:30
Subject: Re: [TN] FAB: Ni/Au Solderability test


>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nomenclature is no longer valid)?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
>[log in to unmask]

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