My preference is to find out the diameter of the solder mask defined pads on the bga side and use that value for the NSMD pad on
the board. The goal is to have equal surface tension on either side when the ball is in reflow. (ignoring differences due to
flux and intermetallics)
Best Regards
David Greig
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GigaDyne Ltd
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t: +44 (0)1383 624 975
www.gigadyne.co.uk
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Perkins
Sent: 02 March 2007 00:36
To: [log in to unmask]
Subject: [TN] BGA footprint
Hi
I am working on a new board with a 0.5mm pitch BGA and I am wonder if someone can advise me on the footprint.
1) the datasheet says the solder ball is 0.3mm +/-0.05mm
2) IPC recommends to use 80% of ball diameter for the pad which would be 0.24mm
3) Would it be OK to use a 0.2mm pad? I am hesitant to go against recommended size without some corroborating documentation. The
reason I would want to use 0.2mm pad is to avoid using via-in-pad.
I am curious if IPC defines footprints based on what is good for manufacturing or is it simply theoretical?
Thanks
Bob
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