Yannick,

You might look at the solderpaste you're using.  We found significant
differences in voiding with water soluble pastes. I suspect there are
similar differences with no-cleans.

Rick Thompson

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


===== Original Message from [log in to unmask] (TechNet E-Mail Forum.) at
3/11/03 5:14 am
>Hi,
>
>  We experience some void in BGA.  We try different paste and profile but
>nothing seem to eliminate those void. We try something, we took a BGA and
>put only  flux on the ball( Flux 297DX from AIM) and we didn't see any
>voiding after that...
>
>  We use stencil of .006mil, and .005mil of thickness, and we had some
>medium to large void
>
>  We also try a .004 stencil ( like a mini-stencil) where we put some paste
>and we had some little BGA.
>
>  My question is, could the paste and the ball of the BGA could not be
>compatible( we use a no clean solder paste, 63/37, our Solder ball under BGA
>are also 63/37).
>
>  Or is the stencil thickness is very important??
>
>  We use a 10% reduction on the stencil whti round pad
>
>Thanks You
>
>Yannick Brisson
>============================
>Technicien SMT
>Technician SMT
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