Following from the EMPF HelpLine in Indianpolis, prepared by Tim Crawford:

Regarding your question as to whether the Ionograph works with low residue
fluxes, the answer is yes........and no.  The problem with the Ionograph, or
any other bulk resistivity meter, is that they measure anything ionic.  Low
residue fluxes contain weak organic acids that are ionic in nature, but are
also benign to the reliability of the PWA.  So, depending on your actual
flux chemistry and how much flux you are applying,  you may find that the
Ionograph will measure high amounts of contamination, which may not
necessarily be bad.  I stress MAY NOT BE BAD.  Since ionic contamination can
come from many sources, the contamination may not all be from the flux, but
may also be plating chemistry from the board shop, perspiration from an
operator, salt from someones lunch......... These systems are not analytical
tools, they are process control tools.

I assume that you are wanting to use a low residue flux as a way of going to
a no-clean process.  The best way to sell your customer on allowing you to
do this is to show them that you understand the WHOLE process and are able
to control it.  And the best way to do this is to use an analytical method
such as ion chromatography.  The ion chromatograph (IC) is much more
accurate, repetitive, not influenced by process conditions, and best of all
it is ion specific so it will tell you what kinds of ionic materials are
being left on the PWA.  These systems are rather expensive and not easy to
operate so I do not recommend that you buy one of these to control your
process.  But I would recommend that you work with a lab that has this
capability to optimize your process.  Once you have optimized your process
(including incomming inspection, quality control, storage, handling, etc.),
send samples to the lab, while at the same time running duplicates on your
Ionograph.  Once the IC is showing that evrything is clean except for the
weak organic acid from the low residue flux, correlate those results with
the Ionograph and use that as your process control tool. If at a future date
your Ionograph numbers jump, you know something happened with your process
that is contributing additional contamination.
>
>>Date: Wed, 12 Jun 96 10:19:53 EST
>>From: "Hollandsworth, Ron" <[log in to unmask]>
>>To: [log in to unmask]
>>Subject: Assy:  Ionograph & No-Clean Flux
>>
>>     What would be a reliable test method for selling the
>>     No-Clean/Low-Residue flux concept to Mil Customers.  Is
>>     Ionograph testing best?  Could I get some replys from some
>>     of you folks who have jumped this hurdle.  Looking for some
>>     suggestions.  Thanks in advance for the help.
>>
>

                      Jack Crawford
                  HelpLine Manager
    Electronics Mfg. Productivity Facility
                     317.226.5616
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