Paul,

Multicore are currently developing an anti tombstoning paste. We ran a trial
with it last week
on some dummy boards and parts with excellent results. I do not think that
it is released to the
market yet, but it is definately worth investigating. We placed 4,600
capacitors, and got no
tombstoned part after reflow. The aperture pad ratio was 1:1 using a 5 thou
stencil.

We had run the same boards and parts a few weeks earlier with another solder
paste and got
approximately 50 parts tombstoned out of the 4,600 placed.

Martin Bourke
SCI Ireland
[log in to unmask]

-----Original Message-----
From: Paul <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: 11 May 1999 15:33
Subject: [TN] Tombstoning 0402 caps.... Help needed.


>Hi All,
>        I am looking for any information concerning the reduction of
>tombstoning.
>
>        The only parameters that we can adjust are the size of the paste
>dot, the type of paste used (any composition as long as it is eutectic
>PB/SN), and the reflow profile (two atmosphere choices).
>
>        Since the physical pheomeonon is centered around surface tension I
>am very interested to read about any study that was done that resulted in
>reduced surface tension.
>
>        Currently the process is in the fractional percentages, the goal
>is to go below 100 DPM.
>
>Thanks,
>Paul Gill
>Process Engineer
>
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