In a message dated 98-04-03 13:10:22 EST, you write:

>
>  I am not sure if How Clean is Clean is going to be
>  answered, but How Much More can be Extracted by
>  Extended Times and Temperatures.

I agree to some extent.  The intent is to compare methods.

>
>  Just because something can be extracted does not
>  mean it will impact performance.

True.  We are not trying to set pass-fail limits, or determine how much is
good, how much is bad.  Just comparing methods.  Dr. John Sohn would echo your
opinions in this respect.  If, in fact, the modified-ROSE test results in high
numbers from residues that have no effect on performance, then it is also
something we need to know, as this method is being used at a number of
fabrication sites.  Any fabricator to Delco Electronics is using it if they
want to meet Delco's C-7000 bare board spec.

>
>  I would first like to see correlation between performance
>  and the amounts of material extracted.  I don't see any
>  sense in getting all worried because some test methods
>  give higher numbers than others until we see what the
>  impact on performance is.

I don't plan on getting worried or panicking due to higher numbers.  I think
this is a "chicken and the egg" type of question.  Do we first accurately
measure residues, then find out their effects, or do we figure out effects,
then try to backtrack to the residue levels which caused the effects.  My
preference is the former.  I understand the importance of the latter.

Addressing a number of different off-line e-mails:  This testing is not done
to set an IPC pass-fail limit on bare board cleanliness.  That effort is much
farther down the road, two or three studies from now.  There is no intention
of jambing any one method down someones throat or superceding existing test
methods.  The intent is to give a reasonable comparison in residue
measurements between the existing ROSE method, the experimental modified-ROSE
method, and two different ion chromatography methods.  The intent is to give
board fabricators additional tools to determine if they are giving clean
product to customers.  In my opinion, the current ROSE test does not do an
adequate job.

Doug Pauls
CSL

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