Hi Paul,
How could I practically do?
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: Paul Reid <[log in to unmask]>
Sender: TechNet <[log in to unmask]>
Date: Thu, 29 Sep 2011 13:41:27
To: <[log in to unmask]>
Reply-To: TechNet E-Mail Forum <[log in to unmask]>,
Paul Reid <[log in to unmask]>
Subject: Re: [TN] Board question
Hi Vladimir,
Some times the warp and weft of the material is coming into play. The warp is the direction of the weave that the glass fibres were in tension; the weft is the direction in which the glass fibres where under less tension, where more compliant to go around the glass had tight as with the warp.
Placing the warp in one direction can cause the boards to bow and twist.
I would check out the weft direction of each layer from each layer.
Best regards,
Paul Reid
Program Coordinator
PWB Inc,
Work 613 596 4244, ext 229
Home 613 839 7794
_____
From: TechNet on behalf of Vladimir Igoshev. PhD
Sent: Thu 29/09/2011 12:49 PM
To: [log in to unmask]
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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