Practical DIY or modest cost Vapor Phase - does it exist yet?

[pisoiu]

Hi all,
I need a bit of advice regarding my tests with vapour phase oven. My tests are made in a 200mm deep gastronorm pan.
Problem #1, heating. I was deeply concerned about heaters not exceeding 300 degrees celsius (and breaking galden into toxic compounds) and I decided to use PTC heaters from aliexpress, those sold for LED desoldering, with 260 degrees limit. I mounted under the pan 4 pcs x 300W heaters, which seem to do the job at the beginning. What I missed from calculations is the fact that the PTC heaters cut power drastically once temperature goes up. It heats up everything up to 100-150 degrees but at 200 degrees it stops, cannot go further. At that point they take around 250W (all 4 pcs) and that is not enough to raise temperature further. It is a balance point between input power and what is lost. I need to change the heater and to dump the PTC idea.  I was thinking to put a 260 degrees resettable thermal fuse on a normal heating element to prevent it to overheat. But I am unable to find something usable at this temperature. I made some experiments with something like this: https://www.tme.eu/ro/details/hts16-230-500/rezistoare-de-incalzire/telpod/hts-16-230-500-3-6-3/ but they were not ok, I had problems with the contacts desoldering, even if the manufacturer claims the element is ok up to 400 degrees on surface.
Can anyone recommend me a suitable heating element, preferably not round? I need a flat surface to install the thermal fuse.
Problem #2. During tests, without any lid, from the heated galden vapors were raising constantly, but I assumed they are only water vapors from atmosphere, since galden was under 200 degrees all the time.  Trying to build up temperature inside chamber, I decided to put an aluminium lid above. After some time, since aluminium plate was cooler than the vapors coming from the chamber, they sticked to its surface. But when I put the finger on the lid surface, there was not water, I think it was galden. The substance on the lid surface has the same oily consistency as galden. Am I losing galden? Why, since its temperature is under boiling temperature?
Thanks.

[IconicPCB]

cgroen.

i have continued with the build lately and am getting good results with galden230.

I am working with four solid hot plates from an electric stove. The heater assembly is pulling about 11 Amps at 240V and the production cycle takes about 15 minutes.

I have designed a controller for the oven but have not implemented it yet. I am operating the oven manually on the understanding that i am NOT EXCEEDING 4W/cm2 applied power density.

The oven is in early development, I wish to introduce a cooling fan into the chamber to scavenge vapors prior to opening the lid.

I have introduced a separator between top and bottom half of the chamber and the product basket and the lid allow for the basket to be lowered into reflow one and be lifted into cooling zone while the separator gate is closed between the two zones.

I still get  vapor loss however i expected the vapor to condense on cooling coils much more so than it does.I think a recirculating fan inside the chamber will scavenge the vapor.
I use only one thermocouple in the basket to monitor rise of vapor.
Once the temperature reaches 230 C i time the reflow cycle and then turn of the power, turn on water and raise the basket into cooling zone followed by closure of barrier between the two zones.

I wait for the temperature in cooling zone to reach a manageable level and then open the lid and remove soldered boards.
The basket is 350 x 450 mm and the overall throughput is acceptable due to the large area.

[cgroen]

cgroen.

i have continued with the build lately and am getting good results with galden230.

I am working with four solid hot plates from an electric stove. The heater assembly is pulling about 11 Amps at 240V and the production cycle takes about 15 minutes.

I have designed a controller for the oven but have not implemented it yet. I am operating the oven manually on the understanding that i am NOT EXCEEDING 4W/cm2 applied power density.

The oven is in early development, I wish to introduce a cooling fan into the chamber to scavenge vapors prior to opening the lid.

I have introduced a separator between top and bottom half of the chamber and the product basket and the lid allow for the basket to be lowered into reflow one and be lifted into cooling zone while the separator gate is closed between the two zones.

I still get  vapor loss however i expected the vapor to condense on cooling coils much more so than it does.I think a recirculating fan inside the chamber will scavenge the vapor.
I use only one thermocouple in the basket to monitor rise of vapor.
Once the temperature reaches 230 C i time the reflow cycle and then turn of the power, turn on water and raise the basket into cooling zone followed by closure of barrier between the two zones.

I wait for the temperature in cooling zone to reach a manageable level and then open the lid and remove soldered boards.
The basket is 350 x 450 mm and the overall throughput is acceptable due to the large area.

Sounds good!
My project is on hold at the moment, everything is ready (mechanically) to be produced, but until now, I simply have not had the time to finish it I hope things will clear somewhat in the future so I can get on with the project.
If you have any more info/pictures etc of your setup I would love to see them!

[kylehunter]

Sorry for the bump, figured it's better here than a whole new topic..

I'm considering building an oven for our shop. It'll mainly be for prototypes, small batches, and for complex boards when I don't want to profile our big ovens (we have two heller convection ovens). End game, I'd like to have one that has a fast enough batch time to where it becomes feasible to use the vapor phase vs powering up the main oven for all but production runs.

Cost isn't going to be super important, as the alternative for us is to spend $20K  for an Asscon oven.

I'm planning on modeling a lot of this off of vapor degreasing systems. They use incredible toxic solvents, as a result, limiting vapor loss is a safety concern. https://www.baronblakeslee.net/vapor-degreasers/baronette/index.html is an example of a nice batch style vapor degreaser. They don't rely on a sealing lid, instead they go full force with the condensing coils to make sure vaport can't leave. Not having a sealing lid helps massively with pressurization, and cycle time.

Here's a quick mockup of what I'm think of thusfar: (Ignore the exact dimensions, this was before I found the mcmaster container!)




Basically, when doing multiple panels, the Galden will be constantly boiling, so the vapor cloud will always be present. The first set of condensing coils will constantly be condensing vapor. This effectively will stop most vapor from being above this point. Then there will be a 75mm gap, which is called "freeboard" in the vapor degreasing world. There will still be a bit of vapor here, but it will be cooling as it goes. Above this point, there will be another set of coils. This should condense the rest of the vapor that is still around.

This "layered" system allows for cycle times to be pretty fast, since you don't have to wait for the Galden to boil. It also allows there to be a nice temperature gradient to help with reflow profiling.

My current idea for the heater is to have a custom machined heater block with cartridge heaters inside it. (We use this for a reflow hotplate currently) This will be affixed to the bottom of the container, to heat from the bottom up. The coils will be liquid cooled using some sort of laser cooler or similar. The carriage system for the PCB I really haven't put much thought into yet, as that is a pretty easy part and will worry about it later. https://www.mcmaster.com/3763K211/ is what I'm planning on using for the container.

Please let me know your thoughts! I literally just started brainstorming this yesterday, so I'm sure I'm overlooking a lot.

[helius]

There's a very important difference between a vapor degreaser and a VPS system, which is that the former runs open-loop and the latter can't. The Galden cannot be "constantly boiling" because there would be no control over heat transfer rates, and your boards would be terrible with tombstoning and solder voids everywhere. This has been gone over repeatedly in this thread and others, take the time to read them.

[kylehunter]

There's a very important difference between a vapor degreaser and a VPS system, which is that the former runs open-loop and the latter can't. The Galden cannot be "constantly boiling" because there would be no control over heat transfer rates, and your boards would be terrible with tombstoning and solder voids everywhere. This has been gone over repeatedly in this thread and others, take the time to read them.

So either I'm wildly missunderstanding how commercial solutions operate, or I miss explained my idea to you..

So, commercial, batch or inline systems (I don't mean the cheap few thousand $ hobby systems) the Galden is constantly boiling, just like I described. You control the ramp rate of the PCB by controlling how it is lowered into the cloud. This is the only way to have somewhat fast cycle times. If not, you have to wait for it to boil and cool down each time.

Here's an article showing how it works (sorry for the crap image!):

https://www.electronicproducts.com/vapor-phase-reflow/# (See section "2.  Preheat zone")


Since the area above the 230c vapor will of course still be hot, by lowering the gantry at a controlled rate, you effectively control the preheating of the system.

Hope that explains it!

Also, this system will absolutely be closed loop. There will be multiple thermocouples at each layer making sure no temperatures exceed safe operating temps.

[helius]

So either I'm wildly missunderstanding how commercial solutions operate, or I miss explained my idea to you..

So, commercial, batch or inline systems (I don't mean the cheap few thousand $ hobby systems) the Galden is constantly boiling, just like I described. You control the ramp rate of the PCB by controlling how it is lowered into the cloud. This is the only way to have somewhat fast cycle times. If not, you have to wait for it to boil and cool down each time.

Yes, I think you do misunderstand how they operate. They don't "control how it is lowered into the cloud", instead the elevator moves down when the cycle begins and raises when the cycle ends. The speed or depth of the elevator is not servo controlled. The heat input, on the other hand, is: yes, the Galden is hot all the time, but the thing you seem to be missing is that once a vapor cloud exists, every additional watt added to the fluid is a watt that is released on the board by condensing fluid. If this heat flux is not controlled according to a profile, the results will be inconsistent.

[KaneTW]

The last time I spoke with an ASSCON rep the position was controlled in the higher end batch units. There's docs somewhere.

[kylehunter]

So either I'm wildly missunderstanding how commercial solutions operate, or I miss explained my idea to you..

So, commercial, batch or inline systems (I don't mean the cheap few thousand $ hobby systems) the Galden is constantly boiling, just like I described. You control the ramp rate of the PCB by controlling how it is lowered into the cloud. This is the only way to have somewhat fast cycle times. If not, you have to wait for it to boil and cool down each time.

Yes, I think you do misunderstand how they operate. They don't "control how it is lowered into the cloud", instead the elevator moves down when the cycle begins and raises when the cycle ends. The speed or depth of the elevator is not servo controlled. The heat input, on the other hand, is: yes, the Galden is hot all the time, but the thing you seem to be missing is that once a vapor cloud exists, every additional watt added to the fluid is a watt that is released on the board by condensing fluid. If this heat flux is not controlled according to a profile, the results will be inconsistent.

I'm sorry, I just don't think you're correct... Like KaneTW, I also have spoken with Asscon some time ago, and they do control the soldering like I said. You may be right on the cheaper models, again, that's not what I'm trying to compare here. Just look up online "vapor phase reflow preheat" or "soft vapor phase reflow". There's a lot of articles discussing this method. Here's a really good one, which even show's a diagram of the board being moved into and out of the cloud to control temperatures: https://smtnet.com/library/files/upload/Vapor-Phase-Soldering.pdf

> every additional watt added to the fluid is a watt that is released on the board by condensing fluid.
No it's not... Since there's a cold condensing coil in the chamber, that coil removes excess heat, causing the fluid to drip back down in the tank to be reheated. I could constantly boil the liquid, without a board inside it, and as long as my cooling coil is powerful enough, it would sit indefinitely at a steady state. I think you're thinking that this is just a closed chamber, with a heater on the bottom. That's not at all what I'm going for here...

[KaneTW]

The whole point of vapor phase reflow is that the vapor is not heated, only the liquid is. Primary method of heat transfer is condensation of the Galden onto the assembly. The amount of heat going into the liquid phase doesn't matter as long as there's sufficient vapor and the liquid phase doesn't locally overheat.

That being said, I don't think batch units are pressurized. There's a condensate coil and a lid but it's more like a pot lid, not a pressure cooker lid.

I'd run a fluid sim with your approach.

[kylehunter]

The whole point of vapor phase reflow is that the vapor is not heated, only the liquid is. Primary method of heat transfer is condensation of the Galden onto the assembly. The amount of heat going into the liquid phase doesn't matter as long as there's sufficient vapor and the liquid phase doesn't locally overheat.

That being said, I don't think batch units are pressurized. There's a condensate coil and a lid but it's more like a pot lid, not a pressure cooker lid.

I'd run a fluid sim with your approach.

Yeah absolutely, that's what I'm going for here. It won't be pressurized at all.

[KaneTW]

Fundamentally the main issue I see is the condensate coils not providing enough of a temperature gradient. Rest seems close enough to existing batch units.

That being said, this is getting into the territory where it'd be cheaper to buy an inline vapor phase system than develop and iterate on this system.

[kylehunter]

Fundamentally the main issue I see is the condensate coils not providing enough of a temperature gradient. Rest seems close enough to existing batch units.

That being said, this is getting into the territory where it'd be cheaper to buy an inline vapor phase system than develop and iterate on this system.

Gotcha. Yeah my plan for the start is just to run straight tap water and back down the sewer. At least then I know that the cooling capacity won't be an issue.

As for the pricing, IDK man, those inline machines start at $100k - $200k. This won't even come close to that. Especially the first prototype setup. We'll see though.

[Kean]

Kyle, have you looked at the Vapor Phase One?  https://pcb-arts.com/en/vapor_phase_one

I'm not sure if it is big enough for your needs, or if it can run in a batch mode similar to what you describe - but it is open source hardware and might be worth looking at.

Their video is kind of cool...

[kylehunter]

Kyle, have you looked at the Vapor Phase One?  https://pcb-arts.com/en/vapor_phase_one

I'm not sure if it is big enough for your needs, or if it can run in a batch mode similar to what you describe - but it is open source hardware and might be worth looking at.

Their video is kind of cool...

Yeah definitely have! He actually posted a lot of his progress in this thread and another on EEVBlog.

It seems like a solid idea, with some odd design choices. I'd do a custom one to be able to have the continuous boil approach which they don't do, and also content for a new YT series!

[Kean]

Yeah definitely have! He actually posted a lot of his progress in this thread and another on EEVBlog.

Ah, yeah... 

I did check this thread for a couple of search terms to see if it was already mentioned, but it didn't come up as Lukas doesn't actually mention it or his company by name in this thread.