Greetings!

Assume the reflow profile and solderability are good.  Our experience
indicated that the 0402 pad design is the key to good process yield.  In
some cases, the use of nitrogen might help to enlarge your process window.
Anyway, here are my two cents on pad design:
     - Increase end joint width (side joint length)
     - Reduce end joint length
     - Optimize pad spacing
     - Pad shape: oval seems to work as good as square
     - Laser cut your stencil on 0402 pads whenever possible
Remember, reduce solder fillet variation reduces tombstoning.

Hope that helps
Mike Yuen

 ----------
From: owner-technet
To: TechNet
Subject: Re: [TN] tombstoning