Natasha:
        Amen to all of  that Brian.  If farming out is not an option, use an
Austin America type of batch cleaner.  They are well built and do a fairly
good job. New ones cost about 17 K, but if you look long enough it is
possible to find one used for a lot less.  Install a filter series made up
of a grain filter, mircro filter, carbon filter and two DI bottles in
series. Have a 2  megaohm light after the first bottle.  When the first
bottle light goes off, transfer the second bottle to the first one position
and recharge the first one and  place in the second one place. This will
ensure your water out of the second DI bottle will be close to 18 megs.
After filtration hook up a heater and set it to about 140 deg F. The heater
needs to be made of material that can withstand DI water. Have the cleaner
maintain the temp  during operation. Some cleaners have hot air dryers built
in, if not blow the boards off  with dionized air right after process
completion, then bake them. DI water is agresive and will remove loose
particles left on the surface,  remove rosin layer by layer,  remove layers
of metal...  Stainless steel and Teflon will withstand the aggressiveness
effects of DI water.
        Regards,
        Ramon



> -----Original Message-----
> From: Brian Ellis [SMTP:[log in to unmask]]
> Sent: Thursday, August 28, 2003 3:39 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] Water Soluble Solder and Cleaning Methods
>
> Many questions. Unfortunately, the many answers (see below) are full of
> ifs and ands and buts.
>
> Natasha Erker wrote:
>
>  >
>  > 1) Are water soluble solders safe to use with surface mount devices?
>  > As far as I can tell, they have mostly been used with through hole,
>  > as the small gap of SMD does not allow water to penetrate it when
>  > cleaning, and thus the highly corrosive residues remain trapped
>  > beneath.
>
> Happily, there are no water-soluble solders, just w/s chemistry :-) Yes,
> they are suitable, and much used, IF you can be sure of cleaning them
> correctly.
>  >
>  > 2) What is the difference between a saponified resin flux and an
>  > organic acid flux? What other types of fluxes do WS solders use?
>  > Which is preferable?
>
> Now we are into semantics. All fluxes used for electronics are based on
> organic acids, even pure rosin. It would therefore be clearer to use
> "water-soluble" as being more explicit. As the term implies, what it
> means is that most of the residues, after soldering, can be removed by a
> suitable washing and rinsing with water. Rosin (and synthetic resin)
> flux residues are not water soluble, but may be rendered so by
> saponification. This is a chemical process, using very aggressive
> alkalis, that react with the rosin to form a kind of soap (hence the
> name). This soap then needs to be washed off and rinsed, in a similar
> manner to the wash/rinse process as for w/s fluxes.
>
>  > 3) Will ionic cleanliness testing provide an indication if the
>  > cleaning process is effective?
>
> Yes!
>
> I believe that ROSE testing is not
>  > directly aplicable to non-rosin based fluxes,
>
> Not so, I'm afraid. It is perfectly usable with all cleaning processes
> to determine general cleaning quality, but you need to determine, for
> yourself, the acceptable level for your products.
>
> You may be confusing it with "no-clean" processes, where ionic
> contamination testing may be used as a general process control tool but
> has no meaning in terms of absolute values.
>
>
> but would ROSE, in
>  > conjunction with Ion Chromatography provide useful data? How would be
>  > best to monitor the cleaning process to ensure it is in control?
>
> If you clean, ionic contamination testing, by itself, will generally be
> sufficient for quality control. Ionic chromatography is a useful
> qualification and troubleshooting tool.
>  >
>  > 4) What types of batch cleaners are available? Will an industrial
>  > dish washer provide sufficient pressure to clean SMD with WS solder
>  > assemblies? What price range would I be looking at for an 'effective
>  > yet cheap' cleaner?
>
> I personally am opposed to the use of cleaners employing domestic
> dishwasher techniques, including lab washers, for a good number of
> reasons. They usually do not give good results and I say this from
> experience. My company, now liquidated, in Switzerland, pioneered w/s
> techniques in the early 1970s and our initial cleaners were based on
> adapted commercial lab washers. They worked well, but... In the early
> 1980s, we switched from this technique to one based on hotel
> dishwashers, much modified for the electronics industry (you would run
> into trouble if you used a standard one; effectively, other than the
> chassis, housing and motorised linear spray arms, little remained of the
> hotel dishwasher!). These were MUCH more effective. I've maintained some
> data on our old web site at
> http://www.protonique.com/plcom/files/cleaningmach.htm
> which I have no hesitation in mentioning here as there are no commercial
> interests left. If you surf through the pages and the video, you may
> pick up some ideas.
>
> However, drying is a bigger problem than cleaning. Especially with SMDs,
> you do not want to simply allow the residual water to evaporate on the
> assemblies, as any residual contaminants will dry off where the
> capillaries are smallest, i.e., round the solder joints, exactly where
> you want them least.
>
> "Effective but cheap" are paradoxal terms. As a rule, you can have one
> or the other, but not both (although many cleaner manufaturers producing
> cheap machines will deny this vehemently, to defend their cabbage
> patch). If we were selling our APL-5 range today, we would be asking
> about $50-80k for a complete cleaning/drying line. Our original APL-1
> (modified lab dishwasher) cost about $10k in 1975.
>
> You have another option which would undoubtedly be the most economical
> one: farm out the assembly/soldering/cleaning of this small quantity of
> boards to a well-equipped company that is specialised in what you want
> to do: think! no qualification, no learning curve, no capital
> investment, no wasted products during start-up and, if chosen correctly,
> no botched-up assemblies because of cheap equipment. Sounds good to me!
>
> Hope this helps
>
> Brian
>
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