From:	NAME: WILLIAM G KENYON              
	FUNC: Chemicals/Electronics           
	TEL: 302-652-4272                     <KENYONWG@A1@ESVAX>
To:	NAME: [log in to unmask] <"[log in to unmask]"@ESDS01@MRGATE@ESVAX>

Northern Telecom did an extensive investigation of the response 
of WS flux residues vs. time in an ionic tester of their own 
design when they switched from rosin to water soluble.  Quite to 
their surprise they found the release rate of WS flux residues 
from the laminate surface was much slower than rosin fluxes.  In 
fact, where the rosin fluxes would have released 90-95% of their 
residues into the 75/25 IPA/water solution within the standard 15 
min. test period, the level of WS flux residue release did not 
approach 90-95% until the tester had run about 2 hours.  Thus 
many users in the industry assumed they were getting much cleaner 
boards with the WS flux process vs. rosin.  As you can see, this 
was an artifact of comparing the results from an ionic test 
system optimized for one flux residue (rosin) with the data from 
a system that was not optimized for the residue (WS) being 
tested.
The military proposed work to come up with an optimized system 
for measuring WS flux residues in the Soldering Standardization 
Plan in 1980-81, but the work was never funded nor done.  

Interestingly, your report states that higher numbers were 
obtained.  There are two factors that could contribute to this:
first, the levels of halide activator are much higher in WS 
fluxes than in rosin fluxes.  Your flux supplier can give you the 
data here). Thus plain TCA will remove RMA residues to the levels 
needed to pass mil spec tests, where alcohol azeotropes are 
normally needed to get RA fluxes to pass.  In work done early on, 
I was testing Freon TE, Freon TES, the development product that 
was commercialized as Freon TMS and Freon T-E 35 on telephone 
assemblies soldered with Alpha 611 RMA flux.  (The T-E 35 used a 
35% blend of ethyl alcohol in CFC-113 in the boil sump, with the 
4% ethanol azeotrope in the rinse sump.  Both are % by weight).
We had a steady supply of assemblies to clean and use for ionic 
testing.  Statistical analysis of the results showed that the 
groups were "statistically indistinguishable" -- i.e., that RMA 
flux didn't present the cleaning challenge needed to separate and 
rank various cleaning agents.  The downstream effect of all this 
was that proposed work on engineering an in-line cleaner for T-E 
35 was dropped and the effort was put into support for efficient 
cleaner designs for TMS, and that we used RA wave solder flux and 
RA solder paste for the B-36 assemblies in the CFC Phase 1 and 2 
tests.  
With that bit of cleaning and testing trivia posted, the other 
reason the results might be higher and erratic is the WS flux 
used.  All the work I did on WS fluxes in the early '80s were on 
the polyglycol types- which were the only ones available.  As the 
industry gradually accepted the fact that many of the standard 
polyglycols used in IR reflow fluids, HASL fluids, WS fluxes etc. 
could have a very negative effect on SIR, industry leaders in the 
flux world formulated new materials that comply with the WSF0 
category (no polyglycols). The release rate for these materials 
might be quite different from the older formulations; however I 
don't think anyone has looked into that.  Also, the solids or 
non-volatile loading may be much less, which makes generation of 
a foaming version that applies a precise flux loading more 
difficult.  This could be the reason for erratic numbers.
In my WSF/RA/SA flux work, I did flux loading studies on the test 
boards at three different conveyor speeds and reported the data 
at Nepcon West in '83.  Top and bottom side pre-heat profiles at 
the three different speeds were reported as well.  The boards 
were cleaned and then ionics, solder defects, SIR and EmR data 
were given.  So there are data availble that could be used to 
compare with the numbers you are getting today.
--Bill Kenyon
Global Centre for Process Change, Inc.
302-652-4272/-5701 Tel/Fax

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To subscribe/unsubscribe send a message <to: [log in to unmask]>   *
* with <subject: subscribe/unsubscribe> and no text in the body.          *
***************************************************************************
* If you are having a problem with the IPC TechNet forum please contact   *
* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask]      *
***************************************************************************