Dave:
     
        I have used Nitrogen in certain situations to provide an inert 
     atmosphere for the solder paste if I had to leave the paste for a 
     period of time longer than normal after printing.  It was done with 
     the intent of minimizing the oxidation of the solder spheres if there 
     was significant solvent (carrying agent) losses.  I seemed to have 
     excellent luck but I was using an RMA solder paste.
     
         A suggested vendor of nitrogen desiccator boxes is Terra Universal 
     and their number is 714-526-0100.
     
        I would recommend that you touch base with your solder paste vendor 
     and see what they might recommend.  Some formulations of solder paste 
     are more susceptible to process problems than others especially if 
     your facility is not temperature and humidity controlled.  They may 
     have a formulation that may work for your exposure time.
     
     Kevin Frasier
     [log in to unmask]
     http://www.sciatl.com


______________________________ Reply Separator _________________________________
Subject: Assembly: Solder Paste Life Extension
Author:  [log in to unmask] at PMDF
Date:    4/16/96 12:59 PM


     Hello TechNet - I am looking for some opinions/info on the use of 
     extending the tack life of printed solder paste on assemblies. Yes, I 
     know I should be processing as soon as possible but life on the 
     process floor is far from ideal!
     
        1- Does storage in nitrogen chambers help?
     
        2- Who manufactures nitrogen chambers?
     
        3- Does refrigerated storage help?
     
        4- Any technical papers/resources available in industry?
     
     Thanks,
     
     Dave Hillman
     Rockwell Collins
     319-395-1615
     [log in to unmask]





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