Jim
VPS or condensation soldering is, indeed, a good theoretical process
with, as you imply, its main advantage being asymptotic, so component
cooking becomes more difficult.
There are fluids available up to about 260°C, so that is not the
problem. The main problems are
a) the fluids are damned expensive
b) with much fluid vapour trapped under components, such as BGAs, the
losses (emissions) are not inconsiderable
c) the fluids, along with SF6, are amongst the worst "global warmers"
known to man, with an atmosperic residence time in the thousands of
years. The GWP of these fluids is about 10,000, that is that if you lose
just 2 kg in a year, this is equivalent to all the CO2 a medium car will
emit in all its lifetime. Apart from that, do you wish to have some
chemical you use floating around in the atmosphere for the next several
millennia, not knowing what is going to happen to it in the end?
Regarding equipment, the last machine I saw was of German manufacture (I
know they were built up to a year or two ago and they may still be). It
was a batch machine but, IMHO, it was not especially well designed to
minimise emissions.
Brian
Jim Kittel wrote:
>
> Dear TechNetters,
> While attending the last APEX show, I was surprised to find vapor phase
> soldering equipment essentially non-existent. At least the high end,
> conveyorized machines were not to be found. The equipment being peddled for
> no-lead SMT soldering is pretty much 'improved' convection reflow stuff.
> With our convection reflow oven we have to run about 40 C. above melt point
> to reliably solder our more difficult high layer count boards with large
> BGA's (about 30% of our business). If we built these with 'no-lead'
> processing (which may be required soon) I expect the boards would be
> approaching 250 C., which our organic boards and parts would not tolerate.
> It seems to me, in-line vapor phase soldering with a smooth transition into
> the vapor chamber, would offer many advantages. If we could find a thermal
> liquid with a boiling point of 225 or 230 C., we may be able to solder
> 'no-lead' pastes with only a 10 or 15 C. delta and not worry about melting
> down parts. Also we would be in an easily controlled inert atmosphere to
> reduce oxidation.
> Am I missing something in this analysis that is obvious to everyone else?
> Help? Where have all the vapor phase machines gone?
> Jim Kittel
> L-3 Communications
>
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