Virgil

A few hurried thoughts to be going on with:

How did you qualify your cleaning process?

A small amount of even ionic residues close to a few terminations may
average out over the whole board surface as being "in-spec", while being
dangerous where they are.

Your white residues may also be non-ionic, in which case the
contamination tester won't react to them, in any case.

MIL-P-28809 is archaic and dates from long before SMD became popular. It
consequently has no bearing on SMD assemblies. Many users specifiy
cleanliness levels of 1 or even 0.5 µg/cm2 eq. NaCl for SMD assemblies.

Have you tested the flux and saponifier for compatibility?

What are your washing parameters? Many conveyorised cleaners are
inadequate for saponification. Temperature can be very critical. How do
you rinse? With what?

Brian

Virgil Lenton wrote:
> We have recently had some cleanliness testing issues.
> We are washing SMT CCA's with RMA solderpaste in a batch washer (AQ400RU)
> with Armakleen E2001A saponifier. The CCA's are being cleanliness Tested
> with an Omega Meter Model 600 SMD without heat.
>
> Cards that easily pass cleanliness testing at the 14uGNaCl/in squared
> acceptance level refered to in MIL-P-28809 have visible traces (under
> magnification) of whitish flux residue under and around many of the SMT
> components.
>
> I do understand that the cleanliness tester is not meant to be an
> analytical tool, but is a tool to be used for process control.
>
> Here are my questions.
> What do others in the industry do to decide when CCA's are clean enough?
> Do you come up with your own acceptable cleanliness test level using SPC
> techniques?
> Any other comments?
>
> Many thanks in advance
> Virgil
>
>
>
> Virgil Lenton - Manufacturing Engineering
> SED Systems - A Division of Calian
> Saskatoon, Saskatchewan
> Canada
>
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