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Date: | Tue, 28 Nov 2006 12:13:47 EST |
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We had a similar situation recently on a rigid-flex brd (which were sold to
assy house)
where hand soldering was performed....green soldermask....to a trained eye
it looked like massive delamination.
It was discoloration of soldermask (not soldermask peeling or
lifting)....which could be due to heat, flux interaction...we did not really figure out the
cause. It was limited to hand soldering areas only.
X-section proved it (looking with back-light) and also U can scrap the
soldermask w. X-acto knife and see if the laminate below is really delaminated.
Our brds were for aerospace...customer bought the brds after X-sections from
independent lab and report.
Rush
Accurate Engg Inc
_www.accueng.com_ (http://www.accueng.com)
818-768-3919
In a message dated 11/28/2006 9:01:58 AM Pacific Standard Time,
[log in to unmask] writes:
This is standard FR4 with immersion silver finish.
The standard soldermask colour we spec is clear, not green. Allows us to
better see the copper, and often some inner layer features as well, but if you
aren't used to working with FR4 with clear soldermask, it can definitely look
a little strange, at first.
The dark colour seen is due to an inner layer that is primarily ground plane.
I'm pretty sure that it isn't soldermask bubbling
We have not yet done any microsectioning. So far we have only seen this on
fully populated boards that have experienced some hand-soldering, and we are
reluctant to sacrifice one, if it can be saved for production.
I have a blank two-up panel available from each manufacturer we've used. We
are planning to run some hand-soldering tests. Vary temperatures, one
unbaked and one baked from each panel, etc. Any other ideas?
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