(Posting from my home email, as my work email is not compatible with the IPC email forum).

IPC 2222, section 10.1.1 addresses it (16 mils + min spacing). I interpret it to apply to all layers in a board. If you’re requiring fabrication in accordance to 6012/6018, it assumes that the design follows 2221/2222 (unless otherwise specified of course). This 6012 update originated within the rev D effort because there are designs out there with internal and/or external metal running within 2-3 mils from an edge and board users still want to maintain 50% of the lateral spacing free of haloing which has very low producibility.

Joey Rios
MIT Kavli Institute

Sent from my iPad

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