In a message dated 98-01-27 09:04:21 EST, you write:

>
>  The IPC limit for contamination is 10.07 ug / sq in NaCl equiv.    The 3 ug
>  limit is good for no-clean, but naturally the cleaner the better.
>

It should be pointed out that the historical 10.06 figure was for finished
assemblies, processed with high solids rosin fluxes.  For bare boards, MIL-
P-55110 (or was it 28809?) had a value of 5.5 micrograms of sodium chloride
equivalence per square inch.  IMHO, both are a crock.

These limits have been so abused and applied to so many inapproprate places
that it is not funny (one of my favorite pet peeves).

A better measure of board and cleanliness is ion chromatography (IPC-TM-650,
method 2.3.28).  For this, we advise bare board cleanliness of less than 2.00
micrograms of chloride per square inch and less than 15 micrograms of bromide
per square inch.  These measures are NOT THE SAME as the ROSE measures above.

More information on these will be available on our web page, assuming I can
get the host service to get it in place in the next week or so. (A nightmare).

Doug Pauls
CSL

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