Folks,

Given the need for "thin" solder mask and good anti-solderball performance,
I have heard people talk about using LPI to cover the board and then
plugging the vias with dry-film, applied only to the vias.  If the plugs are
on the side of the board opposite the component this might help.

From a test point of view, plugging the vias is a big win!

Any comments from board shops on this type of secondary operation?????

Robert Gordenker
Sr. Test Engineer
ESI Vision Product Div.

                -----Original Message-----
                Subject:        Re: [TN] plugged vias, or no plugged vias?

                     Tim, thanx for the reply!
                     When dry films first hit the scene many years back, we
began using
                     them for our boards, mostly mixed technology, and were
having solder
                     ball and thickness issues, and like a lot of the
industry, we went to
                     LPI for all of our products. I am reluctant to travel
back down that
                     path, and we would have to requalify our board.
However, I want to
                     keep open-minded. But I know some of our board vendors
no longer
                     promote dry dilm, and have moth-balled the process.
                     Are you using dryfilm mask to successfully cover/plug
vias on
                     reflow/reflow boards with HASL finish?
                     And are you having solder balling or mask thickness
issues? We have
                     multiple .5mm pitch "thin" devices on this assembly, so
mask thickness
                     is a concern.
                     Please respond with your dryfilm experience, I'm all
ears!!
                     Thanx again Tim.
                     Jeff Hempton


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