Technetters. We are manufacturing multilayer printed circuit boards. One of our customers request us to make 6 layer memory module board(7"X6.3"X0.05"t) of which bow tolerance is Max 0.30%. It's very tough job. Our 1st yield for that board is lower than 80%. Lamination stack height, heating rate, cooling rate, cushion material, layup construction, coppper balance, baking.... These parameters which I thought related with flatteness were tested many times. But we still see bowed boards(Max 0.70%). I will make every effort to make SUPER FLAT BOARD. Any advice would be appreciated. Thanks in advance. Herold Green ---------------------------------- ----------------------------------------------------------- EasyPost - the FREE web based email service from EasySpace Visit http://www.easyspace.com for the best deals on virtual servers - just US$ 8.50 /month for 100 Meg webspace with your domain name and Frontpage 98 extenions. ---------------------------------------------------------- ################################################################ TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################