In a message dated 12/16/99 6:33:28 PM Central Standard Time,
[log in to unmask] writes:

> Hello technet!
>
>  I got some capacitors that I feel like rejecting but before
>  I do, I need some experienced guru to confirm.
>
>  I have a chip component that is the same size as the pads.
>  I have no end Overhang but neither do I have a good solder
>  fillet, the ends of the part is almost flush with the ends
>  of the pads (not to says that in fact it is).  I have a
>  tinny side fillet (but very tinny) or joint... So Accept
>  or Reject (The QA in me cant resist to reject!)
>
>  Anyone can help??
>
>  JF

Hi Jean,

Just from experience, you shouldn't worry too much...the most important part
of a solder joint is the interface between the bottom of the solderable
surface on the part, and the top surface of the pad...side fillets to add a
bit to things but not as much as one may think. I've also heard from gurus
like Werner, that the big beefy solder joints on caps that many like to see,
actually may degrade the reliability and actually cause the caps to crack
during thermal excursions.

At a past employer (a memory company) there was a custom footprint used on
the decoupling caps on the SIMM's we built that would compromise the pad
dimensions so that either a 0805 or a 1206 could be used which resulted in
just about the same scenario with the 1206's that you describe. The pads were
squished together close enough that both terminations on a 0805 would solder,
but when you put a 1206 on them there wasn't the kind of side fillets that
you would see on a standard 1206 footprint.

We built literally thousands and thousands of these modules without a
problem. The custom footprint became a problem though when we went to
no-clean, because a solder-bead or squeeze-ball was guaranteed when a 1206
was placed. Not a problem in a cleaning environment, because they were always
washed off...but that doesn't happen in a no-clean process...

-Steve Gregory-

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