Lee
I agree with you, but these equivalence figures may be very misleading
as they were established using instruments which were relatively
primitive, by today's standards, in the 1970s, using old process
methods. The European Space Agency found that the equivalence between
different instruments varied enormously with different flux/cleaning
processes (see their published report). It could be dangerous or too
easy to slavishly rely on these old data.
I agree that ion chromatography is an excellent diagnostic tool, where
ionic contamination testing is a good process control method. Believe it
or not, I designed a combined instrument for both in the mid 1980s but
never commercialised it as no-one would have paid the price, at that
time. It worked on the principle of doing an ionic contamination test
(computer controlled). While it was printing out the data from that, the
computer commanded the extraction of two samples of the solution (one
was a reserve, in case of problems. One sample was passed to the
chromatograph which looked for halides as anions and Na, K, Cu and Sn as
cations. The same computer then analysed the results from both tests,
including the curve shape from the first and the ionic conductivities,
to give known values of ions and to make a stab at guessing what the
difference was between the two tests. It sometimes found a total of more
ions with the Dionex than was found by the Contaminometer (ie the total
of the the conductivity from the detected ions was > the conductivity of
the solution!!!!). Such are empirical errors. However, it was spot on
with known injections of reagents and mixtures of them. The software did
a helluva lot of number crunching. Academically, that was one darn good
instrument. Please excuse an old man rambling about his previous lives!
Brian
Lee Whiteman wrote:
>
> Ken Patel,
>
> I agree with Brian Ellis, but to give you some more insight on Ionic
> Contamination limits, I pulled my old copy of MIl-STD 2000. Based on Table
> VII, you find the following upper control limits:
>
> MIL-P-28809 Beckman / Markson: 10 micrograms NaCl / sq. in.
> Omegameter: 14 micrograms NaCl / sq. in.
> Ionograph: 20 micrograms NaCl / sq. in.
> Ion Chaser: 32 micrograms NaCl / sq. in.
>
> What that means is that for different test methods, there are varying
> degrees of sensitivity (ionograph is more sensitive than omegameter). If you
> (or anyone else) is interested, I have a report that explains this to you.
> It's rather lengthy (15 Mbytes in PDF format) to send via E-Mail so I will
> need you address, etc., to FED-Ex to you.
>
> However, if you application requires a higher cleanliness standard, you can
> (and should) reduce these upper control limits appropriately. I agree with
> Brian that you should set the upper control limits for ionic contamination
> found by the omegameter or ionograph.
>
> For additional information on the omegameter and ionograph, you may want to
> check out the following website: http://www.scscookson.com/instruments/.
>
> If you are setting up a cleaning process, or have a problem with
> cleanliness, your best bet would be to have the boards tested via Ion
> Chromatography. That will tell you what ionic contamination is on the board,
> and their respective quantities. We have this capability and you can call me
> off-line about it.
>
> Good Luck.
>
> Lee Whiteman
> Senior Manufacturing Engineer
> ACI / EMPF
> Telephone: (610) 362-1200; Ext. 208
> FAX: (610) 362-1290
> E-Mail: [log in to unmask] <mailto:[log in to unmask]>
>
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]]On Behalf Of Ken Patel
> > Sent: Wednesday, December 13, 2000 8:44 PM
> > To: [log in to unmask]
> > Subject: [TN] Ionic contamination Limit
> >
> >
> > Guys,
> > What is the acceptable Ionic contamination limit for Omegameter 600 and
> > Inograph 500 both made by Alphametals?
> >
> > re,
> > ken patel
> >
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