Pat, We divide the part into the four quadrants, and in each quadrant fan toward the corner of the part. This makes for a horizontal and a vertical routing channel (like a plus sign) through the center of the part. Jon DeGenova [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: [DC] Minimum routing layers for a 256 pin BGA part with 1.27 Author: "DesignerCouncil E-Mail Forum." <[log in to unmask]>, Pat Paulson <[log in to unmask]> at Internet Date: 5/13/98 11:59 AM I'm working on my first design using a BGA part and I'm looking for any ideas that would be helpful. I'm using a 25 mil pad for the solder ball with pin escapes (through hole vias) for each pad. These pin escapes are placed in the same direction so the solder side of the pcb looks like the bga footprint for de-bug purposes. I guess this means I have to use 4 layers to route away from the part? Are there any tricks that I'm missing? I'm ready to say the heck with pin escapes at the part. What techniques do other people use? I'm using 6/6 widths/spacing. Thank you for your ideas/help! Pat Paulson VTEL Corp. [log in to unmask] ################################################################ DesignerCouncil E-Mail Forum provided as a free service by IPC using LISTSERV 1.8 c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE DesignerCouncil <your full name> To unsubscribe: SIGNOFF DesignerCouncil ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional informa tion. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-970 0 ext.311 ################################################################ ################################################################ DesignerCouncil 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 DesignerCouncil <your full name> To unsubscribe: SIGNOFF DesignerCouncil ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################