We have an application where we must guarantee that we have no exposed
conductors on a large section of board.  We needed to have vias in this
area, and dry film was the only way our board vendor would guarantee vias
were tented.  We also are seeing better results in our wave solder process
because of the tented vias.  But alas, nothing is perfect, as we are seeing
by the results in our printing process.


Steve Quinn


At 05:48 PM 4/16/96 PST, you wrote:
>     
>     I am surprised that an one is still using dry film soldermask.  And 
>     even more shocked that anyone has just started to use dry film.  I was 
>     sure that the entire industry has converted to LPI.
>     
>     Why are you using dry film soldermask?
>
>
>______________________________ Reply Separator
_________________________________
>Subject: ASSY:  Dry film mask and paste thickness
>Author:  [log in to unmask] at corp
>Date:    4/16/96 3:47 PM
>
>
>We have just started using a dry film mask(Vacrel), which is about .003" 
>thick.  We are using a .006" stencil and printing .020" pitch parts, and are 
>measuring paste thickness of about .009".  We are using a metal squeegee, 
>but seeing some "dog ear" looks to the paste.  We seem to be getting a poor 
>separation of paste from the stencil.  The mask is about .0005" higher than 
>the pads.  Our variation in paste height measurements on a board has 
>increased by .002" from Photo Imageable to dry film.
>   Are there any ideas on how to process a board with Vacrel to improve our
>printing process?
>     
>Thanks for any ideas/suggestions.
>     
>     
>Steve Quinn
>Heurikon Corp
>8310 Excelsior Dr
>Madison, Wi   53717
>[log in to unmask]
>     
>
>
>