Morey,

I would like to comment on your misunderstanding of the annular ring
requirements as specified in IPC-2221.

The 0.005 and 0.002 numbers that you quote are not new. They were listed in
IPC-D-275 under "military requirements." Both the IPC-D-275 and the current
IPC-2221 reflect the "minimum allowable" annular ring. We do NOT recommend
that one should design to the minimums. The numbers in any of the tables
either reflect a range, or a minimum that may be reliably achieved in
manufacturing. Designers are encouraged to size the annular ring based on
their assembly and repair requirements. As an example, if hand soldering is
possible in your rework philosophy, then a larger annular ring should be
designed into the land.

Annular ring problems experienced by fabricators are usually attributed to an
inadequate amount of "standard fabrication allowance" in the land size
calculation as specified in the design standard.

Regards,

Gary Ferrari
Executive Director
IPC Designers Council
860-350-9300
fax 413-771-5386