Fellow Technet subscribers,

I have a question related to BGA standoff distance after reflow.   We are
noticing some variation in standoff distance on some of the larger plastic
BGAs installed onto densely populated, double sided boards.  By standoff
distance I mean the distance measured between the bottom of the BGA package
and the top of the solder mask located on the pwb.

Is standoff distance considered a good indicator of correct solder ball
collapse?  Is there a formula for calculating what the theoretical standoff
distance should be after reflow based on package weight, solder ball
diameter, # of balls, etc...?

Joe

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