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Thu, 17 Jul 2003 18:39:07 EDT |
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The basic assumption being made here is that the Residue Release Rate of all
these different flux families into the 75/25 v/v 2-propanol/water test
solution is the same. All the original work, choice of test time etc. was based on
the release rate of solvent cleaned rosin flux residues. Northern Telecom
studied this release rate issue and found that while well over 90% of rosin flux
residues came off in the 15 min. test period, it took about 2 hours for an
equivalent amount of water soluble flux residue to come off the boards into
solution.
So yes, you can get get very low Ionograph numbers with WSF in 15 minutes,
but only because you are measuring a very small fraction of the residue that is
present-- its the 80-90% that is still left on the board after the test is run
that is going to harm your product!
For those that are interested in this, I have a greatly expanded version of
the history of ionic measurements plus references to key studies in this area.
The Navy did an exhaustive study of using ionics to measure water soluble
fusing fluids, concluded that it was not a relevant test method; concluded that
SIR much better for WSFF or WSF. This was the same group that developed the
ionic test in the first place. All of this has been published.
Bill Kenyon
Global Centre Consulting
P.O. Box 553, Montchanin, DE 19710 USA
Tel: 302.652.4272 Fax: 302.652.5701 Cell: 302.377.4272
email: [log in to unmask]
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