All, The IPC-2221, Generic Standard on Printed Board Design, and its predecessor IPC-D-275 indicate to use the maximum finished hole size when calculating land size for outer layers and the maximum drilled hole size when calculating inner layers lands. One must include twice your annual ring requirement (one for each size of the land) and a manufacturing allowance for process variation. Both standards include a table to guide you when determining how much of an allowance to provide. If you call fro etchback, then you must also add it to your inner layer land calculation. The referenced section in IPC-2221 is 9.1.1 Figure 9-2 and 9-3 illustrate how annula ring is determined. Regards, Gary Ferrari Executive Director IPC Designers Council 860-350-9300 ################################################################ 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 ################################################################