I posted a similar inquiry some time back and Werner offered the advice as
mentioned by Steve. However, placing components on oversized pads resulted
in some components slipping and sliding on the pads during reflow. The end
result being components that were misligned to the pads but still on them.
Cosmetically, it did not look good.

My 2 cents

-----Original Message-----
From: Stephen R. Gregory [mailto:[log in to unmask]]
Sent: Friday, June 30, 2000 11:52 PM
To: [log in to unmask]
Subject: Re: [TN] 1206 Capacitors on 1812 Pads


In a message dated 06/30/2000 3:15:52 PM Central Daylight Time,
[log in to unmask] writes:

<< 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 >>

Hi Lang!

They will fit, but I have read posts (from Werner I think) that big beefy
solder joints on caps (which is what you'll have with 1812 pads) can tend to
make the caps crack. It also says that on AVX's "Surface Mount Zero Defect
Design Checklist" article on their web page (http://www.avxcorp.com). Look
under Technical articles, then Surface Mount, and you'll see the PDF article
there...

-Steve Gregory-

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