Mike,
        The extra width won't cause more defects.  But I would be concerned
about the center of pad to center of pad dimension.  If the paste on one pad
becomes completely liquidus slightly before the other, it will pull the
center of the termination to the center of the pad.  As long as the center
of one pad to the end of the other pad is not farther away than the length
of the 1206, surface tension from the late reflowing pad will re-center the
1206.  However, if that distance is farther than the 1206 can span, you will
end up with an open on some parts.  Optimizing the reflow profile will only
do so much.

This is a surprisingly common problem.

Thanks

Ryan Grant
Advanced Technology Engineer
MCMS
(208) 898-1145
[log in to unmask]


> -----Original Message-----
> From: Mike Lang [SMTP:[log in to unmask]]
> Sent: Friday, June 30, 2000 2:11 PM
> To:   [log in to unmask]
> Subject:      [TN] 1206 Capacitors on 1812 Pads
>
>
> I have a need to place 1206 capacitors on pads design for 1812 components.
>
>
> The caps are NPO (high quality).
>
> The pad-to-pad dimension is very similar (within 0.003") for my 1812 pads
> and 1206 pads, so that is not a concern to me. What is a concern is the
> width of the pads which differ by about 0.060".
>
> My question:  Should I expect more defects or reliability issues by using
> a pad which is 0.060" too wide on the 1206?
>
>
>
>
> Thanks,
>
> Lang
> x5046

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