I am dealing with an intermittent solder bridging on a BGA package-
about 5 percent of the time.  One avenue to make the process more robust
I was looking at was redesigning the stencil aperture.  I am currently
using a 33 mil square solder aperture giving a paste volume of 2722
cubic mils (with a 5 mil stencil). This reduced the incidence of
bridging - the previous stencil was 6 mils thick and had a print volume
of 3267 cubic mils. The ratio of the stencil aperture to the stencil
aperture area is 92%

The sphere diameter on the package is 24 mils and the pitch is  and in
the past I have made stencil apertures 2 mil larger than the maximum
diameter- in this case the volume would be 1540 cubic mils.  The ratio
of the stencil aperture wall to the stencil print area for a round
aperture is 52%. I spoke with the supplier of the component but they had
no recommendations and a cursory Google search provided no additional
information so I thought I ask the Technet folks.

Thanks


 Tom



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