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December 1997

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Fri, 5 Dec 1997 04:45:10 -0600
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     Bill,
     
     Not necessarily true.  With regards to which method is best, Batch or 
     In-line, EITHER process is great.  Consider this, Enthones patented 
     method is an Automated In-line Process that submerges the entire PCB 
     in Entek Plus Cu-106A.  The prior and post steps are Spray bar (e.g. 
     Soak, Microetch, Acid Dip, etc.).  The important consideration here is 
     Solution Temperature and utmost, the dwell time.  Regardless of what 
     method is used, the dwell time will make or break the assembler (your 
     customer).  A nominal OSP thickness should be .2-.5 microns.  Perform 
     a coupon test and verify via a Spectrometer method.  Again, either 
     process will work, provided the latter items are monitored.
     
     With regards to Thermal Excursions, I do not recommended a bake 
     following an OSP application.  A board bake to remove moisture prior 
     to typical Assembly process is not the same.  Consider this, a typical 
     bake is 1-2 hours @ 110°C (230°F), again dependent on the oven 
     convection.  The Thermal Excursions encountered in Assembly are quick 
     with respect to a bake.  Reflow is typically 5 minutes max per side 
     and same for Wave Solder (pre-heat plus solder pot) and then consider 
     the 130°F wash should you use an OA (Water Soluble Paste).
     
     Maybe someone else can answer this, what Temp/time ratio is equivalent 
     to removing "X" OSP thickness.  There are alternative methods for 
     monitoring moisture absorption at the Fabricator.
     
     John Gulley 
     Inet Inc
     972-578-3928
     [log in to unmask]
     
     
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