Electronics > Projects, Designs, and Technical Stuff
Vapour phase Soldering
jeremy:
--- Quote from: coppice on January 22, 2015, 09:04:26 am ---
--- Quote from: jeremy on January 22, 2015, 08:53:12 am ---3) yes, or maybe some of those watercooling blocks from overclocking kits too? coppice: you want the fluid to condense on the lid so that it doesn't escape.
--- End quote ---
As the vapour is heavier than air, why would it escape? You aren't going to lift the lid until the vapour pressure has dropped.
--- End quote ---
Actually, this is not true in a batch-like system. See the CPU soldering video above; there is no lid on the vessel, just a cooling jacket. You will also still get some loss due to natural diffusion even though it is denser. I'm not sure if this is worth worrying about, but the stuff is expensive so someone needs to test that.
Also, I'm not sure I would feel comfortable having a 100% sealed container being vigorously heated. It might also increase the BP of the fluid. Again, I think someone needs to actually measure the pressure and/or BP changes to see if these are negligible or not.
Does anyone have any contacts at 3M/dupont/solvay that they can put me in touch with? I've already tried contacting 3M AU but they (understandably) haven't got back to me yet.
--- Quote from: coppice on January 22, 2015, 09:04:26 am ---Take what I say with a pinch of salt. I'm basing what I say on results in the 1980s with lower temperature fluid and leaded solder.
--- End quote ---
Thanks for your opinion anyway. It's useful to get many points of view and many people's experiences.
helius:
There are some interesting videos from the manufacturers of these machines.
This company has several videos: This one demonstrates a jig that can desolder a BGA using the same machine and process as for soldering:
Depopulating a whole board would take ages, but it's not uncommon to only rework one large component. The large BGAs are also the hardest to rework with hand tools.
Especially interesting is their top-line product, the VP6000, which has a vacuum system. I assume it is used to recover more of the fluid, or to make the boards dry faster. They have options for filtering flux residue and for convection coolers to enhance board drying.
It also shows that they can calibrate the process using a live device inserted into the vapor bath.
jeremy:
--- Quote from: helius on January 22, 2015, 09:37:07 am ---There are some interesting videos from the manufacturers of these machines.
This company has several videos: This one demonstrates a jig that can desolder a BGA using the same machine and process as for soldering:
Depopulating a whole board would take ages, but it's not uncommon to only rework one large component. The large BGAs are also the hardest to rework with hand tools.
Especially interesting is their top-line product, the VP6000, which has a vacuum system. I assume it is used to recover more of the fluid, or to make the boards dry faster. They have options for filtering flux residue and for convection coolers to enhance board drying.
It also shows that they can calibrate the process using a live device inserted into the vapor bath.
--- End quote ---
Nice, thanks for sharing.
Asscon (related to siemens?) actually has some recent patents on the vacuum. It outgasses the solder to extract any flux pockets caught inside the joints that would cause solder voids. See http://www.smtnet.com/library/files/upload/Vapor-Phase-Soldering.pdf
mrpackethead:
--- Quote ---1) yes, otherwise you will risk tombstoning or wicking. It's actually more of a problem with smaller components apparently because they will heat much faster than the pads. 150C preheat makes this problem basically go away. Source is in one of my previous posts in this thread. Usually an different batch oven is used, but that's only because in production everything needs to go super fast.
--- End quote ---
Tombstones are just painful. We get the odd ones happening in our reflow oven from time to time. For a small batch / prototype system, I wonder if it will be sufficient to heat the board in a convection oven, and then drop on the tray ( gently! )
--- Quote ---2) depends on the amount of heating. Seems like as long as the board is in the vapour and not the fluid it will be ok. If you're talking about density, it is heavier than air.
--- End quote ---
I was more thinking about physically how high the vapour cloud will be, and how big the "zone" between 'air' and the vapour will be. ( there will be some 'transition zone' )
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3) yes, or maybe some of those watercooling blocks from overclocking kits too? coppice: you want the fluid to condense on the lid so that it doesn't escape.
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Now that sounds like quite a good idea. Though i have some good pelters and some fans, that would be very effective as well, and i save yet more water pumping around.
--- Quote ---4) I don't see why you couldn't just wash the board with distilled water in place after everything had cooled down, then just run the thing on 120C for a bit to evaporate the water. When I finally get hold of some galden or fluorinert (I'm trying to get 500mL, but the cheapest I've got so far is about AU$1200 for 3.8L), I think it would be good to do some experiments to see just how much loss you get when you do something like this.
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It may not even be a problem. but looking at another machine it seems they have implemented some fans that blow air over the board once its out of the vapour. My guess is that this helps dry them. ( a bit like squiring compressed air on a board, that you've washed in IPA.. )..
mrpackethead:
--- Quote ---Does anyone have any contacts at 3M/dupont/solvay that they can put me in touch with? I've already tried contacting 3M AU but they (understandably) haven't got back to me yet.
--- End quote ---
Been in touch with solvay, and am waiting for an answer.
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