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December 1998

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Subject:
From:
Douglas Pauls <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 17 Dec 1998 07:52:55 EST
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In a message dated 12/16/98 3:42:06 PM US Eastern Standard Time,
[log in to unmask] writes:

>
>  I have some component guys who have ruled that plastic parts can only be
>  assembled on a no-clean flux line.  Anyone using a rosin (RMA) flux is
>  dis-qualified from assembling for us.  I know the theory is that the
>  microcracks formed at reflow temperatures will entrap corrosive residues,
>  but I have trouble buying the NO-CLEAN GOOD, ROSIN-BAD generalization.

Sounds like ignorance or fear talking.  From my perspective, there is no such
thing as a good flux or a bad flux.  The trick is to find the right flux for
the application and optimize for that flux.  High solids rosins have some very
good protective characteristics from an electrochemical standpoint.  I can
furnish you with an equal number of failure mechanisms for a low solids flux
as for either high solids rosins or for water solubles.  As a process
troubleshooter, I see just about every conceivable way for an assembler to
misuse a flux.  I have yet to see a case where plastic bodied parts could not
withstand an RMA process, but came out well in a no clean.  I would be *real*
interested to know their justification on that ruling.

Doug Pauls
Contamination Studies Labs

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