There is a lot of material on VP in the IPC archives, I have posted the two
links before but may be still be useful. My off the top of the head estimate
two years ago was there would be 10-15% usage of VP. Movement of small
passives has always been a small issue when compared with convection in air.
In nitrogen you get the same lifting for different reasons. Changing the
passive footprint on 0402 is not a major issue to make the design more
robust.
Its true that some systems are more difficult to profile than a regular oven
but not impossible. Its like selective soldering systems, many people never
correctly profile these, just takes a little more time!!
Report covers the use of VPS on lead-free rigid and flexible circuits.
www.smartgroup.org/experience/experiencereport2006.pdf
The other file based on a simple survey I did a coupe of years ago.
www.smartgroup.org/nepcon2006/bobwillisvp.pdf
Still waiting for the someone in the UK to load up a machine in the UK with
235 and 240 fluid to run some tin/copper/nickel paste. Convection works OK.
Many thanks
Bob Willis
2 Fourth Ave, Chelmsford, Essex, CM1 4HA England
Tel: (44) 1245 351502
Fax: (44) 1245 496123
Mobile: 07860 775858
www.ASKbobwillis.com
New Bob Willis "Printed Board Inspection & Quality Control Workshop" 24th
March www.ASKbobwillis.com/faworkshops.pdf
"Troubleshooting Your Assembly Yields Workshop" 25th March
www.ASKbobwillis.com/faworkshops.pdf
Book Bob's "Step by Step Failure Analysis Workshop" 22nd April
www.ASKbobwillis.com/faworkshops.pdf
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: 16 October 2008 14:03
To: [log in to unmask]
Subject: Re: [TN] FW: [LF] Vapor Phase Soldering
After performing a DoE about 4 years ago I changed the pad layouts in
the design library for 0805, 0402, and 0201 components, and changed the
placement angle to 15-24 deg. offset. This results in the molten solder
having to pull the part straight first before it can pull it up, but by
that time both ends are in liquidus. Using this combination, we have had
very few tombstones, although occasionally we do see 0201s billboard,
but very few. We solder more than a million solder joints each month.
Other companies that I do consulting for have adapted the same library
with the same results, except they did it on assemblies that are
primarily soldered with convection reflow. With convection, the offset
is not so important, but the pad design is.
You can map the profile of your assembly or process control tool the
same way you do with a convection oven. I simply connect the
thermocouples to the assembly per the IPC standard, and run it into the
VPS and back out. The RD1 and RD2 have an in-and-back-out train, not a
through conveyor. It is actually easier to run the profiler because I
don't have to actually let the profiler go into the chamber. When our
techs are profiling a new assembly, they use an actual PWB and load it
with as many dummy or scrap parts as we can find. When they perform a
process control verification, they use a fixture that has small metal
clampdowns to hold each TC. This way I can replace TCs when they wear
out without having to solder/epoxy them in place. Doing it this way
maintains the integrity of the fixture. The only variation we see is due
to the very small variation in thermocouples themselves. The mass of the
clamps will actually give you a more accurate reading because they pick
up the IR portion of the energy inside the oven as well as the
convection temperature. The difference can be as much as 7-8 deg. C.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Grunde Gjertsen
Sent: Thursday, October 16, 2008 12:30 AM
To: [log in to unmask]
Subject: Re: [TN] FW: [LF] Vapor Phase Soldering
Apart from tombstoning that is in my experience much worse than with
convection.
Another thing with VP, how do you document your temperature profile?
Grunde
"Stadem, Richard D." <[log in to unmask]> Sent by: TechNet
<[log in to unmask]>
15.10.2008 17:51
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to "Stadem,
Richard D." <[log in to unmask]>
To
[log in to unmask]
cc
Subject
Re: [TN] FW: [LF] Vapor Phase Soldering
I should also opine that when soldering RoHS-compliant assemblies using
lead-free solder paste, you will probably get a much better yield with
VPS than you ever will with convection. Especially in the case of SAC
solders.
There, I said it. Listen to the screams.....
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Wednesday, October 15, 2008 10:38 AM
To: [log in to unmask]
Subject: [TN] FW: [LF] Vapor Phase Soldering
-----Original Message-----
From: Stadem, Richard D.
Sent: Wednesday, October 15, 2008 10:34 AM
To: '(Leadfree Electronics Assembly Forum)'; 'Tony Ingano'
Subject: RE: [LF] Vapor Phase Soldering
VP soldering is great for reflow of massive or hard-to-solder assemblies
or when doing certain subassembly processes (socket manufacturing, etc.)
They are an invaluable tool in any manufacturing facility. There are no
process drawbacks with using the modern VPS machines, better preheaters
and sumps fixed the issues of thermal shock and excessive vapor fluid
use. 3M's Fluorinert and Galden PFPE fluids are safe to use from an
environmental standpoint, per our PCA state offices.
You must recognize that VPS requires some amount of thermal shock in
order to facilitate the condensation action, but it is not usually so
large as to hurt the reliability of most standard SMT components. There
may be some heat-sensitive components that you would not want to solder
with VPS, however. You need to do the homework before jumping in and
running production hardware with VP. Homework is spelled
q-u-a-l-i-f-i-c-a-t-i-o-n, which should include thermal cycling.
But we get a lower DPMO when using VPS than we do with convection reflow
ovens. Better, more uniform heat transfer = better solder wetting.
I have used R&D Technical Services machines, Model RD1 and RD2, and they
have worked extremely well for the companies that I work with. Find them
at:
http://www.rdtechnicalservices.com/index.html
Disadvantages are the cost of the fluids, and the machines require more
cleaning (maintenance) due to the amounts of flux contamination on the
insides of the chamber from the vapor. We have our maintenance people
thoroughly clean them each month as a means of preventing oxidation of
the internal chamber parts.
We use two temperatures of fluid, depending on the application. I am
still waiting for Galden and 3M to get schmart and provide the different
fluid tempertures in different colors so it is easier to avoid using the
wrong temperature fluid.
Anyone know of an inert dye that I can add to the fluid that would not
affect its performance?
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Tony Ingano
Sent: Wednesday, October 15, 2008 8:14 AM
To: [log in to unmask]
Subject: [LF] Vapor Phase Soldering
I am wondering if anyone is currently using vapor phase soldering. What
are the disadvantages of vp soldering? Also, who are the major
manufacturers of VP soldering machines?
Thanks,
Tony
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