Hi All,

The pads of PBGA`s that we use are defined by solder mask  on  our
multilayer FR4 pcb`s
The diameter of stensil aperture is bigger than the pad diameter , so we
are actually printing
( no-clean ) paste on the soldermask.
Is this OK, or should it be avoided ? I presume that the adhesion between
stensil
aperture-paste is bigger than the other one between soldermask and paste,
resulting
to increased risk to solder balls, which could be fatal under PBGA ( pitch
.05" )

Stencil width is 0.15 mm (  6 Mils ), laser cut
Stensil  diameter .56 mm  ( 0.22" )
Pad  diameter    0.72 mm  ( 0.28" )  max
Solder Mask diameter 0.52 mm ( 0.20" )

Any opinions?

Brs, Johannes

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