You wrote: > >We are currently experiencing drilling tears in a 12 layer part. The part >has 12 layers FR4 all layers are 2oz. Pre-Preg style is 1080. Tears are >in both pre-preg and original substrate layers. We have tried reducing hit >counts, some attempts at pecking. > >Has anyone experienced this problem or can anyone suggest a fix. > >Best Regards >Ian Giddings > Ian, A few questions to try and help you out. 1. What size drill? When drilling through 10 - 2oz layers (internals) the bit is going through a lot of copper and may become hot..If you are using drills smaller than .021 or so you may have a real problem. I would definitely reduce the hit count on your bits and I might reduce the chip load and maybe the stack height. 2. How is the lamination? With all that copper you need a lot more heat to flow that resin well.. are you getting good fill? Are you drilling through dry glass because all the resin ran to the layers?... I would look at the cure..you may not be advancing the Tg of the material due to all the heat needed to get the 20 ozs of copper up to temp for enough time. 3. By tears..do you mean gauges at the bundles? This would be a result of a worn dull bit or a lack of resin in the bundle. I would look at these issues and try to optimise the package. can the signal layers be 1 oz? Can the dead pads be removed from the signal layers to reduce wear on the bits? Can you go to more B-stage to improve the resin to glass ratio between layers?...like replace 2 plys of 1080 with 3 plys of 106? Hope these suggestions help Douglas Jefery Electrotek, Inc. [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. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################