Mike

As an ex-manufacturer of instruments, please allow me to add another 2 cents worth. The
Ionograph and Zero-Ion are so-called dynamic instruments which measure the conductivity of the
solution leaving the test tank, deionise it and then return it to the tank. This means that
the solution conductivity must return to the initial base line. The dissolved contamination is
integrated mathematically from the resultant curve. This idea is theoretically sound but
depends on a) working the solution for long times at conductivities where the extraneous CO2
absorption from the air is at its highest and unpredictable; b) that the DI columns remove all
the ions in one passage and c) that the differentiation is instantaneous. These factors result
in necessary approximations which tend to give a too-high reading. Another problem is that,
because it can be set up with a very low conductivity baseline with very long test times, it
can detect ions from substrate materials, which are irrelevant to what is wanted.

The Omega Meter, Contaminometer (one exception - see below) and some others are the so-called
static types. These depend on auto-integration by the accumulation of the ions in the
solution. Because of their nature, they were less sensitive to CO2 absorption and were
generally more accurate, except that - if the volume of solution was too small - there was a
small risk of saturation, in which case the reading would be slightly too low. Tests we did
showed that this would occur only at massive doses of ionic contaminants, especially some
organic lead salts and that the contamination would be extremely high, anyway. I shall risk
the ire of the dynamic fans by saying that the static type is inherently more precise. Despite
what was said in another post, some instruments of this type can stop the test automatically
when there is no further significant rise in conductivity and therefore are not working for a
fixed time. Another advantage of this type is that, if a test is stopped at, say, 15 minutes
but the conductivity is still rising, it is easy to mathematically extrapolate with a
reasonable accuracy to the end point, so that test times are shorter - this is done
automatically by the software.

One instrument we developed could be run in either static or dynamic mode by simply loading a
different software. Commercially, this was a flop as nearly all the customers opted for the
static mode because it was faster and more precise with easier number-crunching.

Hope this helps.

Brian

Michael Fenner wrote:

> These instruments are designed to wash ionic material from a specimen. The difference is
> that the Omegameter processes for a fixed time. The Zero Ion [and the Ionograpgh]
> allegedly extract till there is nothing left. So in theory you can use an Omegameter like
> a Zero Ion by simply continuously replacing your sample back in the machine until the
> reading doesn't change and then adding all the readings up, or you can do the opposite and
> take your work out after a fixed time from the other two. Consideration of the above shows
> that readings taken on one machine type can't be equated to readings from another, the
> quality of correlation will obviously depend on the rate at which the ionic material
> dissolves into the system.
>
> The amount of ionic material collected by the machine is then manipulated mathematically
> into a number which is called the amount of contamination per unit area of PCB.
> Keep in mind that this is an average number only and is not qualitative:
> You don't really know what the ionic contamination is, nor do you know its distribution on
> your work. You assume it comes only from your prior processing and is even distributed.
>
> These machines are  good for process control and measuring the effect of process changes
> as results are obtained quickly enough to respond to in real world time.
> In an ideal world to use them as a shopfloor method  for determination of reliability you
> would first need to plot their readings against time to fail in say SIR testing  or
> accelerated ageing trials for the specific process they are to be used on.
> In this real world you may have to adopt a more pragmatic method , like trying to find out
> what other similar companies to yours do, industry sector practice  and so on.
>
> Mike Fenner
>
> ----- Original Message -----
> From: Collins, Graham <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: 18 January 2000 13:36
> Subject: Re: [TN] Omega meter v.s. Zero-ion(ZI-100A)
>
> > Ramsey, Fumiaki-San
> > The Omegameter was sold in several different models, ours does the full
> > calculations and prints the results on a small slip of paper (like a cash
> > register), as well as .  So no calculators are used in our case.
> > We have both an Omegameter and an Ionograph.  The operators prefer the
> > Omegameter as being a bit easier to use, the main difference being that our
> > Ionograph is an early model where the top of the tank is about 6 feet off
> > the ground, and about 3 feet deep - so some tricks have to be used to get
> > product in and out of the thing.
> > The Ionograph is said to be more accurate than the Omegameter, the main
> > difference (as I understand it anyway) is that the Ionograph uses heated
> > solution, so it does a better job of removing the residue from the CCA.  The
> > Ionograph is controlled by a separate PC and offers more "bells and
> > whistles".  As well, the unit they currently sell does not have the elevated
> > tank, so is much easier to use.
> >
> > Never having seen a Zero-Ion, I can't comment on those.
> >
> > regards,
> >
> > Graham Collins
> > Process Engineer,
> > Litton Systems Canada, Atlantic Facility
> > (902) 873-2000 ext 6215
> >
> >
> >
> > -----Original Message-----
> > From: Ramsey's [mailto:[log in to unmask]]
> > Sent: Tuesday, January 18, 2000 8:23 AM
> > To: [log in to unmask]
> > Subject: [TN] Omega meter v.s. Zero-ion(ZI-100A)
> >
> >
> > Alpha Metals sold the Omega Meter 500. Aqueous Technologies sells the
> > Zero-Ion. The Omega Meter 500 was replaces by  technology similar to the
> > Zero-Ion. The new unit is the Ion-O-graph or something like that.
> >
> > The Omega Meter and Zero-Ion both use a DI water and Alcohol mixture. 75%
> > alcohol by volume.
> >
> >
> > The Omega Meter cleans the test solution to some value greater than 19 Meg
> > ohms and measures the change in solution resistance over time. The measured
> > resistance, temperature, and specific gravity of the solution are factors in
> > a hand calculation to relate the removed contamination to an equivalent
> > amount of salt per square inch or cm.
> >
> >
> > The Zero-Ion  cleans the test solution to one of two preset resistance
> > values, 150 Meg ohms or 50 Meg ohms. The unit  then measures the time it
> > takes to return the solution to that resistivity value after a specimen has
> > been added to the solution. Firmware calculates an equivalent of salt per
> > surface area for you and prints the result in a number of formats.
> >
> >
> > The Omega Meter is less sensitive, in my experience. However, the Zero-Ion
> > can give misleading results because it is so sensitive. There have been
> > occasions where the Zero-Ion measured outrageous levels of contamination
> > because it started to extract contaminates from plastics and the solder mask
> > (especially dry film). The 50 Meg ohm range yields  more stable measurements
> > in these cases.
> >
> >
> > The Omega Meter requires the user to calculate test results by hand. A
> > programmable calculator would be needed for most production line workers.
> >
> >
> > The temperature of the test solution in the Zero Ion increases when used
> > heavily. The warm test solution is a better solvent than room temperature
> > test solution. I found that the tests results were slightly different when
> > the solution was warm. It can give the impression that things are getting
> > worse, when the test solution is merely getting warm.
> >
> >
> > The Omega Meter cleans the sample for a set period of time. The time is
> > selected by the user. The manual suggests five minutes. I found that that
> > results from the Zero-Ion and the Omega Meter were more alike when the test
> > was run for 10 to 15 minutes.  A test cycle in the Zero-Ion will take from
> > 15 to 40 minutes.
> >
> >
> > In my opinion, these tools are only useful for setting a benchmark for your
> > cleaning process. Neither give you an absolute measure of contaminates.
> >
> >
> > The Zero-Ion is easier for a production worker to use, though it can
> > mis-lead users because it is very sensitive.
> >
> >
> > The Omega Meter is not as easy to use. I found its sensitivity satisfactory
> > for use as a benchmarking tool.
> >
> >
> >
> > Subject:
> >         Omega meter v.s. Zero-ion(ZI-100A)
> >     Date:
> >         Mon, 17 Jan 2000 16:36:16 +0900
> >    From:
> >         "F.Shigeoka(Ueno-Seiki)" <[log in to unmask]>
> >
> >
> >
> > I'm looking for test equipment to measure flux residue.
> > Does anyone know the difference between Omega metaer and Zero-ion ?
> > ---------------------
>
> > To
> >
>
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