Steve,
My initial reaction to your comments are that the
fabricator has liquid leaking back out of the vias after curing.
I'll explain why I believe this:
- If it were a curing problem causing peeling it would be
more widespread
- If it were poor adherance at the copper (i.e. via pads,
trace, etc) you would see peeling in those other places as well
- If the copper was contaminated, it would also be
affecting other areas than vias.
- Component holes being larger than vias would drain of
liquids better than vias
- Vias being tented can entrap liquid if precautions and
proper processing are not performed, and this is what I believe is
happening.
I have seen this happen a few times here at our
place.
Keep in mind I am basing this solely on the information
available, I could be way off base...
Curious to know how this evolves though...
Franklin D Asbell
----- Original Message -----
Sent: Friday, February 11, 2000 8:12 AM
Subject: [TN] Solder mask failing tape test..
> Mornin' all!!
>
> This morning
I got a email from one of our buyers telling me that one of the
> boards
at one of our fab shops is being held-up because it doesn't pass their
>
solder mask tape test. My buyer said that they told him that the mask is
only
> coming off the via's, and it was because of uncured mask. The mask
is a LPI
> and the via's aren't meant to be tented. Also the board doesn't
go through
> wave solder as the only through-hole is hand soldered because
it goes up
> through the board from the bottomside.
>
> My
buyer is asking me if we should accept the boards. I have a few
concerns.
> One thing is that if there is uncured mask at the via's, what
guarantees are
> there that there isn't more at other places on the board?
Shouldn't uncured
> mask be a simple thing to fix by either baking the PCB
(if it's a thermal
> cure), or exposing it to more UV (if it's a UV
cure)?
>
> Further still, does uncured mask come off in a tape
test? Or is mask coming
> off from a tape test more an indication of an
adhesion problem from
> contamination?
>
> Thanks in advance
for all replies,
>
> -Steve Gregory-
>
>
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