Since you are only seeing this on the outside panels in the stack, it would
indicate that your heat rise in these panels is significantly faster than the
panels in the middle of the stack, meaning that the resin sets up in these
panels before all of the air is evacuated.  Measure your heat rise on both
the top and bottom panels and on the middle panel; the heat rise rate and
the lagging material may need to be adjusted to reduce the heat rise on
the outside panels.  You also might specify a certain range for your heat
rise rate - we always looked at 190F-300F rather than ambient to
whatever the max temp was, since that was more of a critical range (it's
where the resin flows and sets up).

You may wish to try "PACOPAD" from Paper Corp. of the United States -
call 212/337-5539 for your local supplier.  We use Pacoform #5500-10
here.  I have also used silicone rubber sheets with some success, but I
can't remember where I bought them.

I also never had much success with using 7628 for filling anything bu 1oz
plane layers.  I personally would never try to fill 2 or 3 oz with anything
thicker than 1080 - probably 2 plies next to the plane layers, and then the
7628.

Hope it helps.
Fred J.

>>> Afri Singh <[log in to unmask]> 01/22/98 10:39pm >>>
Can anyone shed some light on a problem i am having in my lam dept.
We are getting pockets of air (bubbles) trapped in low pressure areas
towards the middle of the panel
Seen only on the top or bottom panel of each book
This only happens on cores with 2-3 oz cu.

So far we have tried
heat rise 12 -16 F /min
b-stage with more resin- we are using 7628 only
vacume assist press and hydrolic
low pressure vs high
no kiss cycle
flatness of plates
not able to modify the pettern

  thank you for any suggestions

##############################################################
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.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or
847-509-9700 ext.311
##############################################################

##############################################################
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.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
##############################################################