Hi, Rudy,
Assumption is correct - over-etch occurs in the same place on all boards of
the same design, and is on the patterns. Masked traces are in good
condition. Fab house has not suggested a change of design as a solution to
the problem - in fact they didn't even want the over-etched boards back, so
my belief is that they knew about the problem even before they shipped the
product.
I myself need to learn a lot more about what is a produceable design and
what isn't as far as this sort of thing is concerned, though I would trust
that our board designers should know more about that than I. They
supposedly followed IPC-2221 & 2222 when putting the design together, but
who knows what was missed (if anything).
Does anyone else have this problem with boards with blind vias? Or if it's
DFM'd, what steps were taken to avoid this issue?
Best regards
Peter Duncan
"<Rudy
Sedlak>" To: [log in to unmask]
Sent by: cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST
TechNet Aero/ST Group)
<[log in to unmask] Subject: Re: [TN] Over-etch II
ORG>
11/16/01
11:23 PM
Please
respond to
"TechNet
E-Mail
Forum."
This MAY be so simple, we will wonder why/how they did not see the
problem...
To understand this analysis/suggestion, you have to understand the
difference
between pattern plating (which is done after photoresist application) and
panel plating (which is done before photoresist application).
Again, I am grasping/guessing here, as I really do not understand the
process
well enough to give "expert" advice....
If they are doing a "selective" panel plate, which would make the Copper
selectively thicker, this would be an obvious answer...
I assume that the over etch problem occurs at the same place on all the
boards of the same design? And it occurs on 100% of the boards of a
similar
design? (In other words, is the problem one of process/board design, or
one
related to equipment used in fabrication?)
If the problem is not always in the same place, this would speak to
equipment
issues at their facility...and even if the the problem occurs at the same
place on all boards, it could still POSSIBLY be equipment issues at the
fabrication facility.
Rudy Sedlak
RD Chemical Company
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