Vu,
     
     I went through this process once before.  I defined the process as 
     Soldermask Dot Printing.  Its not one stop shopping but it works.  Set 
     up one DP-10 screen exposing vias to be filled.  Only fill the 
     soldermask from one side.  Three (3) passes may be required to push 
     the soldermask to the solder side (pending board thkness).  Soldermask 
     dimples will be apparent on the solder side, but no need for concern.
     
     Two side filling will entrap air/moisutre in the via in-turn causing 
     soldermask blowhole which may result in further process problems at 
     assembly.  Since filling the vias with mask is prior to HAL, entrapped 
     air/moisture with component heat will oxidize the copper, in-turn may 
     cause reliability issues.  In other cases, oxidation propagates no 
     further than the top micrometer barrier, therfore protecting the 
     underlying copper (argueable).
     
     Any how, cure the LPI following Dot Print and proceed forward as 
     normal. The mask was either Taiyo PSR4000 or Ciba Probimer 52.
     
     I have an idea of what you are trying to achieve.  There is an 
     alternative to what you are trying to process.  Call me and I can 
     explain further.
     
     John Gulley - QA
     972-578-3928
     [log in to unmask]
     


______________________________ Reply Separator _________________________________
Subject: FAB: One step soldermasking to plug vias
Author:  "vu" <[log in to unmask]> at Internet
Date:    11/14/96 3:10 PM


     This question probably has been asked before: 
     
     Does anyone know an effective way to do one step soldermasking 
     operation to plug via holes using DP-10 machine? Is there a preferred 
     solder mask that can do this?
     
     Vu Minh Du
     Process Engineering
     PC World
     
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