Key changes include moving from a specifying rounded rectangle pad shapes with corner radii,
, which officially includes through-hole guidelines that were missing from the 7351 series. PCB Libraries Where to Find Resources IPC-7351C Land Pattern Overview | PDF - Scribd ipc-7351c pdf
The development of IPC-7351C was famously stalled and eventually scrapped in favor of starting fresh with Key changes include moving from a specifying rounded
version, with the intended "C" updates largely absorbed into the newer IPC-7352 Guideline Overview of IPC-7351C ipc-7351c pdf