Nancy,

IPC-TM-650 microsection methods 2.1.1, manual microsectioning
is the one referenced in the 276 document.  This doesn't have 
figures illustrating the exact measuring locations, however the
6.1 para addresses that thickness should not be determined 
at nodules , voids, cracks or irregular and thin platings.

If your hole wall was very rough, you might have nodules where
the plating was thicker than others and deep folds where the
plating thinned.  These would not be indicative of the actual
deposit if the hole wall was not rough.  The thin areas are considered
ok, if they do not go below 0.0008".

Hope this helps

Susan Mansilla
Robisan Laboratory
317-353-6249