Brian:, its not the dissolved oxygen so much as the fact the vapour doesn't
displace all the air.
Björn: At the risk of being pedantic, an advantage of saturated vapour
phase, and a principal factor in its original introduction for back plane
soldering, and subsequent adoption in surface mount, is its ability to heat
very uniformly almost irrespective of work size or geometry. This uniformity
allows ramp rates which are much higher than is possible with other
mechanisms for heat transfer.
Anyone: However VPR heat transfer fluids are more expensive than, and
clearly have an environmental impact which is greater than, the most common
alternative medium used in conventional reflow ovens. Air is free :)
The process advantages of VPR - which I fully appreciate - have to be set
against its costs and disadvantages on a case by case basis. IMHO I think
that this sort of analysis will show that for odd geometries heavy parts
mixed prototyping etc, and for adhesive [epoxy] curing, saturated VPR has
some attractions. Certainly it's a process which is hard to get wrong on one
offs, but its harder to get really optimum on longer runs.
Kind Regards
Mike Fenner
Applications Engineer, European Operations
Indium Corporation
T: + 44 1908 580 400
M: + 44 7810 526 317
F: + 44 1908 580 411
E: [log in to unmask]
W: www.indium.com
Leadfree: www.Pb-Free.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Brian Ellis
Sent: Monday, May 27, 2002 10:11 AM
To: [log in to unmask]
Subject: Re: [TN] SV: [TN] Vapor phase
Björn
There are VP reflow systems with controlled preheating, either using
secondary fluids or IR. It is not necessary to put cold components in
vapour at 215°C or more.
Brian
Björn Kullman wrote:
>
> 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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