Hi All,
Thanks for the overwhelming response, but sorry guys I did not get what I
wanted. To respond to all the queries that was posted, below are my reponse:
1. We use Cupric etchant.
2. We AOI only the signal layers 100%, but the P&G layers are only sampled
about 10% of the lot & this is where our problem lies. If we do a 100% then
we can capture them hopefully.
3. We perform Hi-pot test for P&G cores less than 3.5 mils, maybe we need to
do this for other cores also. But the problem is what if it is Sig/P&G core
we may not be able to do this, then we may have to do 100% AOI for the P&G
layer.
4. Misregistration, etching problems etc, etc., we may have them but we do
not have a good feel because the biggest problem is we are not able to
locate them as the P&G short can happen at any location randomly across the
panel, so we need to figure out a way of finding the fault before we can
nail down the root-cause.
5. But, based on the few we are able to locate we do not see under-etch,
misregistration etc., but could be copper particles between the clearances,
but the number of boards able to be troubleshoot are so small we cannot
truly establish the true cause.
6. All the boards are bare boards immediately after our process & is
detected at the final electrical test, does not escape to the customer.
7. In fact I tried using a Toneohm ground short fault locator, but was not
very successful. If the short happens to be between a trace & ground then it
is fast & easy, but if it happens to be between the P&G which runs across
the layers on the board, it is very cumbersome & not able to locate.
8. We are having a small percentage of boards with this problem & more
apparent on designs with tight tolerances for the clearance pad on the
inners.
So anyone out there can think of a way to check, measure or locate the P&G
shorts apart from doing 100% AOI will be very much appreciated.
Thanks,
Krishnan
-----Original Message-----
From: Rudy Sedlak [mailto:[log in to unmask]]
Sent: Thursday, September 18, 2003 4:49 PM
To: [log in to unmask]
Subject: Re: [TN] Inner Layer Ground Shorts
Are you etching with Cupric, or Ammoniacal etchant? Ammoniacal is quite
sensitive to tarnish on the board, so if your boards are tarnishing, this
could be the problem...
What do the shorts look like? Can you send us a picture?
Lots of resin spots popping up in the industry lately, not, of course, that
I would want to blame the copper foil, or laminate from any particular part
of the world... and this could be causing your problems...do you check
laminat with black light as a part of inspection? Might be a real good idea
to begin, if you are not... One of the Sanmina's found innerlayer shorts
almost completely related to resin spots on the Copper...
Good luck from Shenzhen China..
Rudy Sedlak, RD Chemical Company
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