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
################################################################