In a message dated 97-11-06 09:56:28 EST, you write:

> We are using water soluble flux and solder pastes. How we can check
>  cleaning quality at exit of water cleaning and drying station?

Are you talking about monitoring the cleanliness of the water going into your
aqueous cleaner or checking the ionic cleanliness of the assemblies after
aqueous cleaning?

For the former, an in-line resistivity monitor should do.  For the latter, I
suggest ion chromatography (IPC method 2.3.28) as an analytical tool, and
then use the modified ROSE method, developed by Phil Wittmer at Delco.  That
method is currently in draft form for IPC review as 2.3.25.1.  This method
uses the ion chromatography extraction method, but allows you to use your
ionic cleanliness tester.  Phil has found reasonably good correlation between
IC and the mod-ROSE method.  The background paper was published in the IPC
Technical Review, March of 97.

>  What methods are being used by process engineers for checking/monitoring
>  cleaning quality?

In my experience, the most used (but least understood) measurement tool is
bulk ionic cleanliess (ROSE).  Only a small fraction of engineers have
baselined the response of the instrument against another analytical residue
detection method.  I really think the mod-ROSE method shows real promise as a
process control tool.

Doug Pauls
CSL

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