I bow to Doug's superior but cheesy knowledge (buttering him up!). 
However, in dairy farming regions, the cow lick is a dangerous source of 
sodium contamination. A cow's tongue is like a rasp and she must 
liberate a fine lick powder when using one. In a high wind, this powder 
would travel at a good lick, onto everyone's PCBs. An ionic tester could 
cream off the salt deposits.

Brian

On 11.02.2014 15:17, Douglas Pauls wrote:
> Brian raises some excellent points, but I must disagree that the most
> likely source of calcium is the tap water.
>
> Rich works up in Wisconsin (Up Nort).  Wisconsin is a dairy state and cows
> are everywhere.  Using Brian's submicroscopic theory, your calcium is
> coming from when cows walk by the plant.  Perfectly logical.  You have a
> Holstein Crisis.
>
> Your second most likely source of calcium could either be from tap water,
> or it could be coming from your solder mask.  Many masks have a certain
> amount of calcium as a filler compound.  Elevated levels of calcium in
> your extract solutions may mean the solder mask is not fully cured or that
> it is chemically degrading, allowing the filler material to leech out.
>
> Doug Pauls
>
>
>
> From:   Brian Ellis <[log in to unmask]>
> To:     <[log in to unmask]>
> Date:   02/11/2014 01:57 AM
> Subject:        Re: [TN] Risks Associated with Calcium
> Sent by:        TechNet <[log in to unmask]>
>
>
>
> Good point re CaCl2 used for deicing. As you probably know, in a former
> life I made the Microcontaminometer. With the smallest tank, it could
> measure down to picograms NaCl equivalent. I had some thoroughly cleaned
> samples, 1" x 1" ceramic hybrid wafers, on my bench for testing.
> Suddenly, they showed ionic contamination levels much higher than they
> should have, which puzzled me. I was pondering on this when I saw a salt
> (NaCl) sprinkler going along the road and light dawned. The tyres of
> cars passing kicked up an aerosol of slush and salt that presumably
> evaporated leaving a suspension of submicroscopic salt crystals that
> floated everywhere including into my lab, which was a good 20 m from the
> road (and the windows were shut!). This hypothesis was confirmed on a
> number of subsequent occasions.
>
> Similarly, I had a customer in Rennes at the foot of the Brittany
> peninsula, about 50 km from the coast. He told me that his PCBs showed
> consistently slightly higher ionic contamination readings when a violent
> north-westerly Atlantic storm was raging.
>
> However, tap water is the most probable source of Ca.
>
> I'm afraid that 1 ppm is meaningless as such unless we know the area
> from which the aliquot was derived. 1 ppm from a sample the size of an
> A4 paper sheet would be bugger all in terms of reliability but it may be
> a different story if the sample was a small passive component.
>
> Brian
>
> On 11.02.2014 00:08, Richard Kraszewski wrote:
>> 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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