http://npil.kaist.ac.kr/pdf/foreign_journal/FJ_76.pdf
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of vladimir Igoshev
Sent: Thursday, September 29, 2011 2:02 PM
To: [log in to unmask]
Subject: Re: [TN] Board question
Hi Dave,
I just measured it from the sections and they were pretty much identical and well balanced!
Vladimir
SENTEC Testing Laboratory Inc.
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (416) 899-1882
Fax: (905) 882-8812
www.sentec.ca
-----Original Message-----
From: "David D. Hillman" <[log in to unmask]>
Sender: TechNet <[log in to unmask]>
Date: Thu, 29 Sep 2011 12:53:49
To: <[log in to unmask]>
Reply-To: TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Subject: Re: [TN] Board question
Hi Vlad - one other thing to check - is the pwb stack up "balanced"? Are
all of the layers (both the dielectric and the copper) symmetrical with
respect to the board thickness midpoint? Are you sure all of the
thicknesses are equal?
Dave Hillman
Rockwell Collins
[log in to unmask]
"Vladimir Igoshev. PhD" <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
09/29/2011 11:49 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
"Vladimir Igoshev. PhD" <[log in to unmask]>
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Subject
[TN] Board question
Hi TechNetters,
I have a question for board gurus, as I'm almost lost.
Here is a story. A panel of four simple 4 layers FR4 twists after
going through the first side re-flow and flatten out after the second
side is re-flowed. It does the same thing with and without the
components placed.
The panels are from new vendor and the old ones had never exhibited
the problem. What confused me is that both boards (from both of the
vendors) were built identically: dielectric layers and Cu
layers are look identical thickness- wise.
There are no signs of resin recession or delamination in
cross-sections which could have pointed out at incomplete curing.
Glass bundles look also identical.
What else it could be?
Any suggestions are deeply appreciated.
--
Best regards,
Vladimir Igoshev. PhD
mailto:[log in to unmask]
SENTEC Testing Laboratory Inc.
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (416) 899-1882
Fax: (905) 882-8812
www.sentec.ca
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