One factor to help eliminate tombstones is do not reflow in nitrogen.
Presence of nitrogen lessens surface tension. Reduce pad spacing. IRI Alpha
Metals has a reference guide for aperture selections and stencil solutions.
Contact Rich Syphers at Technimark for the guide.
[log in to unmask]
Dave Chapman
Manufacturing Engineer
Circuit Service Inc.


-----Original Message-----
From: Rick Thompson [mailto:[log in to unmask]]
Sent: Tuesday, October 29, 2002 6:17 PM
To: [log in to unmask]
Subject: [TN] Round Pads for 0402 Parts?


We have a customer who is using round pads for 0402 size parts to reduce
solder volume.  Despite optimizing the profile, we still get a higher than
usual percentage of tombstoning.  Does anyone have any recommendations /
insights, pro or con, on using this type of pad with 0402 components, versus
using some other techniques to reduce solder volume?

Thanks in advance.

Rick Thompson

Sr. SMT Process Engineer
SMTEK International, Inc.
+1 (805) 532-2800
[log in to unmask]

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