Steve
Difficult to say, for sure. I think the most significant clue is the
halo round the mounting hole (?) in the middle of "ivory" and the lack
thereof in "ebony" (isn't this a little racist?). This is confirmed by
the fact that the left edge of "ivory" is worse than the centre. This
leads me to suppose that there is some reaction occuring at edges.
What is your soldering/cleaning chemistry, what is the substrate
(presumably FR-4, but which type?) and what type of solder mask is it?
If I had to make a guess, I'd tend to say that the probability lies with
a solder mask problem, possibly simply undercuring. A possible cause is
that an old LPI mask material is not releasing sufficient free radicals
to ensure cross-linking through the thickness of the mask, leaving a
polymerised surface layer and a tender under layer. This could allow
flux penetration. However, your enlargement does show another problem
which would worry me even more: particulate matter, including fibres. If
these foreign bodies are under the solder mask, as it looks, then you
may be in DEEP trouble if you need reliability.
Brian
"Stephen R. Gregory" wrote:
>
> Hey All!
>
> Wave soldered three boards today, all the same assembly, same profile, etc.,
> and after wash one board looked all milky white on the bottom, they all
> looked the same coming out of wave though...when comparing it to the other 2,
> it was like Ebony and Ivory...go to:
>
> http://www.driveway.com/share?sid=4eced0a4.94f42&name=Pictures&view=3
>
> And you see what I mean. I've got a close-up on Ivory too. Mask seems intact,
> and everthing else seems okay except for the milky color... the "Ebony" looks
> like it almost was going to do the same thing, because you can see the
> outline of the wave solder fixture in it, but it didn't. On "Ivory" you can't
> miss the fixture outline...what in the bajeebers would cause something like
> this? Is the board scap? It's class-2.
>
> I tried baking to see if would do anything but it didn't...
>
> Thanks!
>
> -Steve-
>
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