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 >> >> ______________________________________________________________________ >> This email has been scanned by the Symantec Email Security.cloud > service. >> For more information please contact helpdesk at x2960 or > [log in to unmask] >> ______________________________________________________________________ >> > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > > > > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________