We are experiencing tombstoning with our 0402 chips when our nitrogen is
on, but when it is off, the defect goes away.  And as one would expect, the
solder joints are not as shiny and smooth  without the nitrogen.

We are using SN63 fine pitch paste in a forced convection reflow oven.

One of our suppliers (ROHM) has recommended using non-eutectic SN62 (with
silver) and .02" diameter round pads spaced apart .04" but we have never
tried this type of pad design before (square peg on a round pad)!

Any suggestions or experiences would be appreciated.

Thanks,

Phil Bavaro
(619) 658-2542
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At 5:52 AM 2/17/96, Jeffery L. Hempton wrote:
>There was a question a few days ago on cures for tombstoning.
>
>One of the simplest but effective cures that we've found to help with this
>problem, at least for 0805 and 0603's, is to design the spacing between pads
>to be .020".