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Mon, 11 Nov 1996 16:57:52 -0600
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From [log in to unmask] Thu Nov 14 16:
48:11 1996
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     Address,
     
     An industry move 8 years ago was to move away from from V-HAL to HASL 
     due to coplanarity issues on fine pitch devices.  To me, back then, it 
     made all the sense in the world.  After further testing we found that 
     HASL did not provide the needed coplanarity necessary and solder 
     puddles were more apparent on the component side (top) lands versus 
     the solder side (bottom) lands, however the panel was run.  
     
     Because of that, V-HAL were re-thought, boards were turned at an angle 
     for better coplanarity in addition to several other variables.
     Because of the technology changes there has been a move towards V-HAL, 
     since the solder height is better controlled, for lack of a term.
     
     My discussion today throws all this out the door.  HASL it seems, 
     now controls solder height and provides better coplanarity than V-HAL.
     
     
     #1  Aside from vendor process control, I would like to hear from 
         others on WHAT is WHAT anymore?  Lets forego alternative surface 
         finishes in your responses.
     
     #2  Re-HAL boards should not be concern anymore if properly done?  
         I am seeing some SnPb oxidation and would prefer to re-HAL boards.
         Aside from the standard concerns, thermal excursions (cycling)
         (laminates are way ahead now, considering solder hasn't changed), 
         inducing bow and twist, etc, what are some unique concerns.
     
     John Gulley = QA
     INET Inc.
     972-578-3928
     
     
     
     

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