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August 1997

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Fri, 22 Aug 1997 10:58:12 +0000
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Hello

I'd like to throw my 2 cents in.  We have gone through a
painfully time with corrosion.

RMA flux-YES it can cause problems with components.
YES it does get into the fine cracks in the lead egress.
LEDs for instance(with current limiting resistors) can
crack during wave or IR processing.  Aqueous cleaning
drives in contaminants and causes rapid corroison-DEAD
components.    We have seen flux entrappment in
FETs in TO220 style packages-causing leakage paths
between leads.  Many components are sensative to the
halides and chlorines in RMA that are not cleaned properly.

One thing we learned, cleaning is paramount!  You
could use any chemistry however, you must thoroughly
clean the product.  Aqueous cleaning tank reservoirs must be
measured for dirt(ionics).  We found extensive humidity testing
would provide the data supporting cleanliness.   Corrision quickly
grows like a yeast fungus on  bread, in humidity.

Proudly, we are at a point where our process is 100% NO-CLEAN.
Our chemistries both at the front end are compatible with
the repair and field service organizations.   We are doing
quite well with controlling corrosion.

Obviously there is more behind the scenes than I can list in
a memo.


Good Luck-we did it.  You can too!
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      Don F. Fumia
      [log in to unmask]
      Schneider Automation
      No. Andover MA
   508-975-9344   FAX x9714
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