Hi Jack,
Seems to me you got into trouble because your "pinkish core" which is
unbalanced with the rest of the 6 layers, looks like a decoupling layer =>
or Buried Capacitance layer.. in any event, so thin for such voltage with
only ONE pre-preg, is calling for troubles. Had a case similar where the
facing layers where not parallel to each other. Hot Press Lamination does
not always produce same pressure at any points of the board and adding to
the fact glass threads were not even either, plus a low quantity of resin,
creating "almost holes" where shorts happened.
If we are talking about inner layer BC, then BC (Sanmina patent) need to be
made using no glass and particular dielectric material.
See the real intention of the Designer.. if she/he is not using this couple
of layers for BC...
Meilleures Salutations
Very Best Regards
Roland
www.PCBspecialist.com
Roland Jaquet
14 Champ Budin
1258 Perly, GENEVA
SWTZERLAND
GSM+41-79-203-3723
"Quality is best measured not by the return of the products but by the
return of the customers"
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Olson
Sent: Wednesday, November 21, 2007 10:58 AM
To: [log in to unmask]
Subject: [TN] Core Quality Issue?
Sorry to re-start a previous discussion, but I'm still dealing with a
board failure and I'm trying to learn fast.
I received a higher-resolution picture of a board problem we are having
http://www.frontdoor.biz/PCBportal/corequestion.jpg
<http://www.frontdoor.biz/PCBportal/corequestion.jpg>
Http://www.frontdoor.biz/PCBportal/corequestion.jpg
http://www.frontdoor.biz/PCBportal/corequestion.jpg
and if I look at it closely, I can see the dividing line between all ten
layers of dielectric.
By looking at which way the copper is located from each dividing line, I
can tell which are cores and which are prepreg (because the prepreg
layers will flow "around" the copper features) For example, the thin
pinkish layer is a core. Am I on the right track so far?
So, our problem is a 120V end-of-line test frying two out of every
hundred boards right through the pinkish core material with the white
streak through it
(3.2 mils, which should handle a few kilovolts at least, right?)
So here's the question:
Should I be questioning the material quality rather than the bare-board
manufacturing process itself?
I realize you guys have already been generous with helping me on this,
so I hope I'm not pushing your patience...
onward thru the fog,
Jack (aka "the new guy")
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