Chi-Man,

   Try this...Create the dot pattern to run a few mils larger than the
via hole on one side and on the other side, image with a dot pattern a
few mils smaller than the overall pad diameter. Cure the mask and apply
the hole plug from the side which was imaged a few mils larger than the
pad diameter.

   Keep an eye on the off-contact, I found this gave me fits when trying
to reduce smudging around the SMT's.

   Another thing you may want to try is to use drilling's entry material
as your screen. Drill the tooling holes and the vias first and swap off
the entry material. Adhere the entry material to a mesh and cut away the
mesh. I hear that this is a much more effective way of screening hole
plug. I hear it is also easier to set up because you can use the tooling
holes in the entry material to align the boards.

                                            Good luck!

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