I agree with Doug.  Rick, can you send few lb of string cheese this way?  Many thanks. 

Joyce Koo
Researcher
Materials Interconnect Lab
Office: (519) 888-7465 79945
BlackBerry: (226) 220-4760

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Tuesday, February 11, 2014 8:17 AM
To: [log in to unmask]
Subject: Re: [TN] Risks Associated with Calcium

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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