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ADuCM350 Footprint

Question asked by gimbal on Jan 18, 2018
Latest reply on Jan 24, 2018 by devangs3
The Aducm350 datasheet specifies a ball diameter of (0.25 | 0.30 | 0.35 )mm and the recommended footprint available for download has  0.305mm pad (copper, solder, paste all the same). Typically I've seen a pad size of ~80% of the nominal ball diameter used and believe non-soldermask defined is preferred. Is there a reason for such a large pad and no solder mask expansion?
My current design uses the below sizes for a slightly smaller pad and some solder mask expansion to make the pads non-solder mask defined. Is there any concern with this?
Pad = 0.26mm
Solder paste = 0.26mm 
Solder mask  = 0.36mm (0.05mm expansion)