Hi David,
Our CAM operators (bare board fab) tell me that same size, or consistent
oversize (i.e. 3 mil ring) work equally well.  Consistency is the only
important factor.  This allows us to globally manipulate the soldermask pad
sizes as needed.
When clearances vary within one artwork, adjusting soldermask pad sizes
takes much longer.

Note: I assume that mask pad size would equal "hole size" only on
unsupported (no pad) holes.

Note: don't forget to add a fab. dwg. note allowing the board shop to adjust
mask pad sizes as needed.

Regards,
Mark

        -----Original Message-----
        From:   David Hoover [SMTP:[log in to unmask]]
        Sent:   Tuesday, November 04, 2003 11:18 PM
        To:     [log in to unmask]
        Subject:        [TN] Soldermask Clearance Question

        I am in the middle of a discussion/debate with assemblers on one
side and
        designers on the other.

        The question is:
        What would your shop prefer to receive from the designer for
soldermask features?

        either
        A) 1:1?  (Soldermask clearance same as the holesize, padsize,
surfacemount, or
                      clearanced feature size)
        or
        B) Soldermask Clearance set at some value over the pad/feature/SMT
size?
            (Like 3 mils per side)

        Thanks for any and all responses,

        David Hoover


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