problem:  smd components floating off the pads during reflow  (i.e. mailbox
aluminium electrolytic capacitor)(d-packs)

question:  is there any  information (or guidelines) that discuss the
relationship between component weight and contact surface area with the
board.

we have mailbox packages that float around during reflow because the
surface tension of the molten paste is not great enough to prohibit the
component from moving during reflow.   the problem is also related to
"smoothness" of the material handling, i.e. no abrupt inertial changes.

we can kinda guess that larger lead/land and pad sizes would keep the
component in it's appropriate location, but it would be nice to have some
"rule of thumb ratio" that we can add to our design guidelines.

any help would be appreciated.

M.R. McQueeney
Advance Technology Engineering
Chrysler Huntsville Electronics
(256) 464-2629
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