I am occasionally seeing irritating low levels of calcium in some assemblies that we test via ion chromatography.

Some organizations required spec levels as low as <1 ppm.

My questions to you techies is:

#1 Besides wash water are there any other sources of calcium that come to  mind?

#2 is there any real value in having Calcium specs down as low as 1 ppm?  (I suspect not and this spec was merely carried over from the semiconductor industry where it may have more value)

CH65 is of some help here in that is does speak much more of the evils of Na that Ca& Mg, but not as much as I had hoped. 

Thoughts??

Rich  Kraszewski 
Senior Process Engineer
Plexus Engineering Solutions 

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