The questions I have are related to back-to-back BGA assembly on double sided surface mount designs. A common application is reverse- pinned memory devices, i.e. which lets both parts share similar signals (data line, address line, etc.). Specifically, 1. Are the BGA's commonly mounted with their pads exactly mirror imaged? 2. Can they share common vias? 3. Are there any known reliability issues with implementing directly mirrored pad configurations? Bruce Tostevin Benchmark Electronics Hudson, New Hampshire ################################################################ 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 ################################################################