We are experiencing some bow and twist, greater than 1%, on standard 4 layer multilayer. I know that the copper tracks and ground plane is spread quite evenly over the circuit. Iam also testing a different build from our existing one. Details as follows: Existing Build Testing Build !/2 oz Outer Foil !/2 oz Outer Foil 1 x 2125 pre-preg 1 x 2125 2 x 7628 1 x 2125 0.51mm 1/1 Core 0.93mm 1/1 Core (Core Tg >125) (Core Tg >140) 2 x 7628 1 x 2125 1 x 2125 1 x 2125 Gel time is short flow: 120 seconds +/- 20 Vacuum press cycle details: 90 mins @ 175 deg C / Heat up rate 6 deg C per min / 36 min cool down @ 10 tonnes. I would also be interested in comments on the way panels are thermally cured at final cure photoimage - racks, Tunnel dry, etc ?? Ian Paterson [log in to unmask] ############################################################## 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 ##############################################################