Hello there,

My colleague was reading the IPC-2221 when she come across the
difference in definition between internal and external annular ring. I,
too cannot understand why? Anyone can to try, maybe Jack Crawford can
help :8)

External Annular ring :  The minimum annular ring on external layers is
the minimum amount of copper (at the narrowest point) between the edge
of the hole and the edge of the land after plating of the finished hole.

Internal Annular ring : The minimum annular ring on the internal layers
is the minimum amount of copper (at the narrowest point) between the
edge of the drilled hole and the edge of the land after drilling the hole.

Thanks and regards,
Wee Mei


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