Very often, this condition goes well beyond normal balanced copper plane
constructions. It is a matter of other resin/glass construction
requirements.

From a fabricator's standpoint, is the press calibrated? Are press cycles as
specified? Is press platten parallelism assured (lead strips, etc.). Do all
heater elements work? Is thermal input balanced, etc.? And on it goes.

Earl Moon
----- Original Message -----
From: Brian Lane <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, September 27, 1999 11:46 AM
Subject: Re: [TN] Warped PCB's


> Chris,
> Is there even copper distribution on the 2 outer layers? How about on the
> inner trace layers? If one of your trace layers either internally or
> externally is out of balance with it's 'mate', you could be contributing
to
> the problem. It could have been that the board shop did some kind of
rework
> that heated the board, and cooled it in a condition that allowed it to
warp
> (ie solder mask touch up). You didn't mention your dielectric properties,
> but of course they should also be balanced.
>
> At 02:23 PM 9/27/99 -0400, Chris Bartkowiak wrote:
> >Friends:
> >
> >I have a 6 layer board that warps.  The R&D group tells me its a
> >Manufacturing problem. I'm not so sure.
> >
> >Details:
> >.062" Thick NEMA FR4
> >Stack: (Trace/Gnd/Trace/Trace/Power/Trace) w/1/2 oz copper clad.
> >R&D group tells me the layers are balanced from the center of the stack
> >out.
> >
> >What should Manufacturing be doing to prevent these boards from
> >warping?  Or is the only solution a higher temperature
> >FR4 material that adds cost to the board.  Could it be a problem with
> >the board house. Please advise.
> >
> >Regards, Chris
> >
> >##############################################################
> >TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
> >##############################################################
> >To subscribe/unsubscribe, send a message to [log in to unmask] with
> following text in
> >the body:
> >To subscribe:   SUBSCRIBE TECHNET <your full name>
> >To unsubscribe:   SIGNOFF TECHNET
> >##############################################################
> >Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
additional
> >information.
> >If you need assistance - contact Gayatri Sardeshpande at [log in to unmask]
or
> >847-509-9700 ext.5365
> >##############################################################
> >
>
> ##############################################################
> TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
> ##############################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with
following text in
> the body:
> To subscribe:   SUBSCRIBE TECHNET <your full name>
> To unsubscribe:   SIGNOFF TECHNET
> ##############################################################
> Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
additional
> information.
> If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
> 847-509-9700 ext.5365
> ##############################################################

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################