Techies

Taking on-board all that has been said, consider:

There is at least one system on the market where the entire process is
conducted in a sealed chamber.

In this way, the expensive heat transfer fluid may be recycled with
minimal losses - < 10 kgs per year assuming 2000 hours per year. BTW,
that's only 5 litres or just less than 1.5 USgallon per year! (Proven in
application.)

The process involves loading the chamber with assemblies, and sealing
it. The fluid is then injected at a controlled rate onto a heated plate
in the bottom of the chamber. As this plate would be set at around 25 to
30 DegC above the boiling point of the liquid, the liquid will vaporise.


It will then condense onto anything colder than itself, even under the
most discreet devices.

Because of the controlled rate of injection, the temperature ramp can be
easily maintained at 2 to 2.5 DegC per second.

Because the liquid can only boil at its boiling point - there is a
temperature delta of less than 5 DegC over the boiling point. 

The process is being done in an inert atmosphere.

What are the boiling point liquids that are available? 200 - 210 - 220 -
230 - 240 DegC 

Thus, SAC alloy (Tin Silver Copper) with a melting point of 219 DegC
will be reached with 220 liquid and NO overtemperature issues
whatsoever.

Upon completion of this part of the process, a separate vacuum pump
removes the vapour to ensure, as far as possible, that there is minimal
residue for "evaporative" or "drag-out" losses. The fluid is filtered
and recycled into the reservoir for almost perpetual re-use.

The process may be considered "dis-continuous" or "batch" but, with the
right size of chamber, a whole days production could be achieved in only
3 minutes. BTW, this is only to show that throughput is not an issue.

This is a process that is receiving considerable interest on this side
of the pond. If you want more, contact me off-line because from this
point on, it is commercial!

Regards Graham Naisbitt
 
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> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Björn Kullman
> Sent: Monday, May 27, 2002 07:57
> To: [log in to unmask]
> Subject: [TN] SV: [TN] Vapor phase
> 
> 
> True about not being able to overheat components, but, 
> consider the fast ramp-up that the majority (all?) of vapour 
> phase ovens produce. Components sensitive to temperature 
> changes above 4 deg/sec are liable to damage.
> 
> Björn Kullman
> 
> Sincotron Technology Center, Norrköping, Sweden
> Sincotron Sverige AB                    www.sincotron.se
> phone +46 (0)11-368288 mobile +46 (0)70-4245607
> 
> -----Ursprungligt meddelande-----
> Från: TechNet [mailto:[log in to unmask]]För Brian Ellis
> Skickat: den 25 maj 2002 08:06
> Till: [log in to unmask]
> Ämne: Re: [TN] Vapor phase
> 
> 
> Mike
> 
> It's true that PFCs do dissolve oxygen but the quantity in 
> the vapour phase is sufficiently low that no significant 
> oxidation will occur, unlike non-controlled atmospheric 
> convection or IR soldering. Milder/less flux can be used.
> 
> The advantage over convection is that 3-D assmeblies are much 
> easier to solder and, being asymptotic, the process is less 
> liable to damage components which are very thermally 
> sensitive because it is impossible to exceed the vapour 
> temperature which is fixed by the chemical composition.
> 
> Brian
> 
> > Stefano Riccardi wrote:
> >
> > Hi all!
> > We are currently looking for the assembling of a double 
> side SMT - one 
> > side THT (High pin count connectors) board, with a lot of BGA. An 
> > assembler proposed us the use of vapor Phase reflow soldering. Any 
> > comment about this method? Can someone tell me where I can find 
> > informations (books, www,
> > publications) about the vapor phase soldering?
> >
> > Thanks!
> 
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