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

[KaneTW]

Yeah, something like that. It needs a fairly decent epoxy to hold up to the stresses, but it should be doable. Would need to verify with simulations. The big issue there is temperature. Duralco 133 goes up to 350C, but I'm not sure if the strength is sufficient.

 From what I remember commercial ovens bolt them on using a backplate, but that would require drilling through the Gastronorm container.

It's still possible to make a liquid tight seal under those constraints, but there's more failure points and you need a machined part anyhow which kills all the advantage a Gastronorm has.

If a bonded strip heater turns out to be unviable, you could immerse them. That should give you a high surface area. Bonding in this case can be done with a high temperature silicone if it's chemically compatible with galden. Otherwise fix it from outside.

[cgroen]

I'm trying to dive a little more into this....
I see the Weller WAM 3000 has a smaller container below the "floor" of the large chamber, where it has the Galden/heater.
Is this a possible (or am I misunderstanding their drawing..) solution ? Doing this, one could much easier find a suitable heater, and the amount of Galden would be lower (compared to having the whole bottom of the large chamber covered with Galden). Will this still enable the vapor to move/fill the bottom of the large chamber ?
(sorry for asking probably stupid questions, I'm not a "gas wizard" )

[KaneTW]

That's a good idea, mostly because it cuts down on heater surface area. From the drawing it seems like they're bolting it on.

The vapor is denser than air, so there will be a vapor blanket up to some level. Level control is done via temperature sensors.

[cgroen]

That's a good idea, mostly because it cuts down on heater surface area. From the drawing it seems like they're bolting it on.

The vapor is denser than air, so there will be a vapor blanket up to some level. Level control is done via temperature sensors.

Thanks Kane!
Ï'm looking at the various models ASSCON VP450 and the Weller, a plan starts to materialize

The process chamber, I will get that done in stainless steel (I'm not a TIG welder, so I will leave that to the professionals  ). Its very easy then to find a suitable heater and have that incorporated into the design. I'm aiming at something like 400 x 400 mm PCB area, I wonder how much area around the PCB is needed for the vapor to get "above" the PCB ? I'm guessing 50 mm around larger than the PCB on all 4 sides, but this is just a guess !!

The "Galden" container that will be placed in the middle/below of the large chamber will be designed around whatever suitable heater I can find, I will get something with a large area (many "windings") per the recommendations you gave about approx. 4W/cm2. I will be looking for something around 2KW or so (should be plenty).

Cooling, I see some have a bunch of fans for cooling (IMDES etc), some use a real compressor/chiller (ASSCON) and some use simple water circulating system (Lukas). I also saw one of the members here (I think it was Iconic-PCB) that had 2 coils inside the process chamber with what looked to be simple water cooling. If that system is running or not I don't know.

I'm also temped to make the tray moveable by a winch system, ASSCON seems pretty neat. I know this is not absolutely needed, but why not overdo it once you have the possibility
I know this is probably going to take me too long, I really need this to be finished rather sooner than later, but I figure I might as well do it as good as I can...

Thanks a lot for the inputs so far, really appreciated !! 

[cgroen]

So, something along these lines....
The bottom chamber has an extra bottom so there is a small compartment where the heating element will be placed. This will give me a good even surface to mount isolation on. This also enables me to select whatever heating element is suitable.
Only "issue" is that the heating element is just touching the top of the small chamber, its only stuffed in between the top and bottom. I hope this will transfer the heat.
Otherwise I can use the mica strip heaters, might even be better!!

[KaneTW]

Heat transfer with an air gap is really bad. For that type of application I strongly suggest a strip heater with some (suitably rated) thermal grease and clamps or a backplate fixing it to the bottom.

[Lukas05]

Hi,

the project on my side is also coming along quite nice so far.
I´ve opened up a new thread a while ago, if you want to have a look at the current stage of development.

https://www.eevblog.com/forum/projects/automatic-vapor-phase-oven/

The results are pretty good. The profile also looks a lot cleaner now. The modelling of the lift mechanism combined with the behaviour of the vapor phase itself where a bit challenging.
I ended up modelling the system in LTSpice to play around with the regulation loop parameters.

This is the most recent board I soldered in the oven:

https://pbs.twimg.com/media/EQSbkagWsAAwvSB?format=jpg&name=4096x4096

I´am using gastronorm at the moment since it really is the cheapest option. Until now I can´t confirm any buckling of the container. My simulations also don´t show any excessive amount of stress. I will post-process the simulation results and post them in here. I don´t know If I will stick with the container in the future. The reason why I didn´t publish any source of the container is that it was an ebay fund.

I wouldn´t recomment drilling any holes in the bottom of the container. Or at least I don´t see the need to. I could imagine this action would come along with a lot more manufacturing an qualification effort. The immersion heater I´m using works good so far. The phase change at the heating element can transfer a lot of energy. By nature of convection the resulting vapor phase is very homogeneously. A PCB that covers most of the tray are creates a lot more disturbances in the heat distribution profile than the location of the heating element. (these disturbances aren´t very large still)

[cgroen]

Heat transfer with an air gap is really bad. For that type of application I strongly suggest a strip heater with some (suitably rated) thermal grease and clamps or a backplate fixing it to the bottom.

Kane,
I agree, it needs to make contact. The idea was that _perhaps_ the heater could be pressed up against the upper plate, but its still not optimum. I'm currently looking into mica strip heaters, by combining a bunch of those in series/parallel I can reach f.ex 1700 Watt on a 350 x 300 mm "tray" where the galden then would be located. That will give me 1.6W/cm2 which is a lot lower than the max recommended of 4 to 5 W/cm2.

Hi,

the project on my side is also coming along quite nice so far.
I´ve opened up a new thread a while ago, if you want to have a look at the current stage of development.

https://www.eevblog.com/forum/projects/automatic-vapor-phase-oven/

The results are pretty good. The profile also looks a lot cleaner now. The modelling of the lift mechanism combined with the behaviour of the vapor phase itself where a bit challenging.
I ended up modelling the system in LTSpice to play around with the regulation loop parameters.

This is the most recent board I soldered in the oven:

https://pbs.twimg.com/media/EQSbkagWsAAwvSB?format=jpg&name=4096x4096

I´am using gastronorm at the moment since it really is the cheapest option. Until now I can´t confirm any buckling of the container. My simulations also don´t show any excessive amount of stress. I will post-process the simulation results and post them in here. I don´t know If I will stick with the container in the future. The reason why I didn´t publish any source of the container is that it was an ebay fund.

I wouldn´t recomment drilling any holes in the bottom of the container. Or at least I don´t see the need to. I could imagine this action would come along with a lot more manufacturing an qualification effort. The immersion heater I´m using works good so far. The phase change at the heating element can transfer a lot of energy. By nature of convection the resulting vapor phase is very homogeneously. A PCB that covers most of the tray are creates a lot more disturbances in the heat distribution profile than the location of the heating element. (these disturbances aren´t very large still)

Thanks Lukas,
I'm looking in your thread 10 times a day hoping for updates
Can you tell me the size of the gastronorm you use ?

[cgroen]

Just got a couple of mica strip heaters (I have never seen these in real life, so had to get my hands on a couple to get a feeling for it)
My good friend is a brilliant mechanical engineer/CAD designer, I'm hoping for his help on this
I wonder why the Weller WAM 3000 is "dead", it seemed like a reasonable idea, either the market was not there, or it didn't work 

[nisma]

It works, the reason it is dead is because of several design decisions and its high price.
Later a cheaper model with better specs came out, VP50 relabeled to some names , I don't remember the exact name from non OEM version. Having double eurosize panels on WAM the tact time is 17 minutes and on VP50 it is just 3min /panel. If PnP have tact time of 6-12min do you really consider the more priced WAM for more then 3 seconds
after you have realized this?

[cgroen]

It works, the reason it is dead is because of several design decisions and its high price.
Later a cheaper model with better specs came out, VP50 relabeled to some names , I don't remember the exact name from non OEM version. Having double eurosize panels on WAM the tact time is 17 minutes and on VP50 it is just 3min /panel. If PnP have tact time of 6-12min do you really consider the more priced WAM for more then 3 seconds
after you have realized this?

Thanks Nisma,
good to know that it at least works (do you happen to know what the selling price was at the time?) !
Do you know about which "design decisions" that was the problem ?
Incredible that the cycle time was 17 minutes on it, I mean with a gate and all that.

[nisma]

No, i don't remember the selling price.
The so called bad design decision was not bad itself, it was just bad in relation to the concurrency that emerged later.
The 30x30cm instead of 50x50cm for batch processing.
Probably this was the limit for forced cooling.
The other is the use of forced air cooling instead of liquid cooling with laser chiller.
liquid cooling is more efficent and a lot more quite as forced air cooling.
Annother problem with the massive air movement is that dust is moved around giving additionl headcaches.
The Fan starts during galden heating process.
Third is not to use fan cooler on top, this lead to increased galden usage.

[cgroen]

No, i don't remember the selling price.
The so called bad design decision was not bad itself, it was just bad in relation to the concurrency that emerged later.
The 30x30cm instead of 50x50cm for batch processing.
Probably this was the limit for forced cooling.
The other is the use of forced air cooling instead of liquid cooling with laser chiller.
liquid cooling is more efficent and a lot more quite as forced air cooling.
Annother problem with the massive air movement is that dust is moved around giving additionl headcaches.
The Fan starts during galden heating process.
Third is not to use fan cooler on top, this lead to increased galden usage.

Thanks Nisma!
sounds like good valid points you make there, i can imagine the large fans and dust, didn't think of that before, but makes perfect sense.
I see on most commercial units that the coolers (water cooler) is mounted at various points compared to the vapor cloud, some shows them just above the cloud, and some show them higher up in the chamber, I wonder the effect of that?

[cgroen]

I'm trying to get  a feeling for the heater needed for my system. Does any of you have an idea of how much "heating area" is needed to get this going, lets say I have a chamber of 500 x 500 mm, and that the area where the liquid galden is located is maybe 300 x 300 mm (as an example). Is that way too much area to heat on, or is it way too small (I kknow that Galden is heavy, and I hope the vapor will "level out" so it will fill the larger compartment from the bottom and up when forming, so the area where the galden is located does not need to be huge) ?
I'm not a "vapor/fluid" expert (software is my main trade ), and I'm having a hard time figuring all this out. Also, lets say that the "container" where the liquid galden is located is 300 x 300 mm, how much power is needed for a system like this to work ? are we talking 1000W, 1.5Kw, 3 KW or ?? (assuming 230 degC, and vapor height of maybe 150 mm or so )
My good friend is arriving in a couple of days, and then the design starts, I need some ballpark figures to aim at for a start, I know that this will be a lot of experimenting, but would be nice to have a starting point.
Originally I needed a finished system, luckily I have taken care of the immediate need in another way, so I have the time now to make something that hopefully will work.....
All inputs are welcome 

[KaneTW]

When I was designing a system, my main considerations were:

* Heater/fluid well area determined by minimum fluid level
=> You want at least some fluid (how much depends on your controller skills) to provide a safe operating margin so that the heater can keep running during the process

* Maximum fluid level determined by process volume (and well area)
=> You can estimate the amount of galden needed using the ideal gas law and your process volume, then add the minimum fluid amount determined above

* Vapor level determined by target heat capacity
=> You want enough vapor so that there's always vapor around the PCB during the actual soldering process. If there's not enough vapor, you'll have difficulties with maintaining a profile.

* Heater power determined by cycle requirements, maximum heating density, and process volume
=> You need to fill the vapor level back up to nominal after a cycle finishes, which is determined by how much heat you can dump into the liquid. If you can wait for half an hour for the vapor level to go back up, you don't need a strong heater. If you need to do it in 2 minutes, things get more complicated. You can calculate the minimum energy required from the Galden datasheet (specific heat + heat of vaporisation), but that doesn't include losses.

[cgroen]

Thanks for all the input Kane, much appreciated 
I know what direction to go with a lot of the stuff now, need to go study!
But, one thing I have a hard time figuring is how large the part that holds the Galden needs to be compared to the area of the large chamber. My idea is to make a smaller area with the liquid Galden, put the heaters below that, and let the vapor rise up and around in the large chamber (exactly like the Weller WAM3000 in the drawing below). From that drawing, the "hot area" looks much smaller than the actual process chamber. The good thing about that is the lower amount of Galden needed (smaller area). I just need some kind of idea if that is possible and "allowed" (a different approach is Lukas and the IMDES devices, they have liquid Galden over the complete area of the chamber.
I have a couple of mica strip heaters here, each is 6 x 4 inches, and 950 Watt. An ideat situation would be to make a small chamber of perhaps 8 x 8 inches or so, the heaters could then cover the bottom of that, and heat the Galden in there. I'm just not sure if a 8 x 8 inch (200 x 200 mm) chamber would be enough for "cooking" the Galden for a process chamber of 500 x 500 mm, or if the vapor just will fill it fine anyway

Again, thanks a lot Kane for your input (and your patience )

[cgroen]

Doing (at least trying to) some math here....
I'm NOT sure I got all this under control, I might be waaaay off and wrong in a lot of the following, but hey, at least I'm trying


If I set the process chamber to 500 x 500 mm, the height of the vapor to 200 mm (volume is 0.05 m3)
The temperature is set to 230 deg C, and pressure of 1 atm, I get 1.211 mol required using: https://www.chemicool.com/idealgas.html
According to https://www.solvay.com/en/brands/galden-pfpe , the molecular weight of LS/HS/HT-230 is 1020 amu (LS/HS/HT-200 is 870 amu)
So 1 gram of HT-230 is 1/1020 mol (1/870 mol for HT-200).

So to fill the 500 x 500 mm chamber with a 200 mm high "cloud of vapor", I need 1.211 mol * 1020 => 1235 gram of HT-230
If using HT-230 instead (870 amu), I will need 1.211 mol * 870 => 1054 gram of HT-200

Density at 25 deg C of HT-230 is 1.82 g/cm3, so 1235 gram is 679 mL.
Density at 25 deg C of HT-200 is 1.79 g/cm3, so 1054 gram is 589 mL.

Just for fun, compared to water: molecular weight of water is 18.02 amu. 1.211 mol of water weights 21.6 gram
So 21.6 gram of water can fill the chamber with vapor, Galden HT-230 requires 1235 gram/679 mL for the same !

Getting fluid up to boiling temperature:

Specific heat @ 25 deg C for Galden is 0.23 Cal/g deg C => 0.96 J/g*deg C.
To raise 1253 gram Galden from 20 deg C to 230 deg C requires: 1253 * 210 * 0.96 => 254 kJ.
So if 253 kJ is required, I can bring the Galden to boiling point (from 20 to 230 deg C) in 1 minute using 253 kJ/60 seconds => 4.2 kW

Specific heat for water is 4.186 J/g*deg C.
To raise 1000 gram of water from 20 deg C to 100 deg C requires: 1000 * 80 * 4.186 => 335 kJ
So, the water will boil in 60 seconds if I inject: 335 kJ/60 seconds => 5.58 kW.

Vaporizing the fluid completely:

Heat of vaporization for Galden when already is at boiling point, for both HT-200, HT-230, LS-200 and LS-230 is 63 J/g (the different types are almost all the same value).
So to vaporize 1235 gram of (already boiling) HT-230 I need 1235 * 63 => 78 kJ.
If I would need to vaporize all the Galden in 1 minute I would be required to supply 78 kJ/60 sec => 1.3 KW of heat during that 1 minute (sounds like an awful small amount ??).
(for HT-200, this would be somewhat smaller, the amount of Galden is smaller, and it would need to be raised 30 deg less than the HT-230)

Heat of vaporization of water already at boling point:2260 J/g
To vaporize 1000 gram of water (already boiling) I need 1000 * 2260 =  2260 kJ
Vaporizing in 60 seconds requires: 2260 kJ/60 sec => 37 kW for 60 seconds

All of this assumes ideal conditions, no loss to the surroundings etc.

Can anyone perhaps confirm the calculations, at first I thought it is a large amount of Galden needed to fill the chamber, I know it is quite large (500 x 500 x 200 mm), but still?
Also, I don't quite understand that the heat of vaporization is 63 J/g for Galden and 2260 J/g for water, is that really true ?

On top of that amount I will need to add the minimum level as Kane pointed out (also a 200 mm high vapor cloud is very much, could probably be much smaller).

EDIT:

If chamber is 500 x 500 with only 130 mm cloud height:
Volume = 0.5*0.5*0.13 = 0.0325 m3
At 230 deg C, 1 atm, 0.0325 m3, 0.787 mol is required.
0.787 mol * 1020 => 803 gram => 441 mL

Raising 803 gram from 20 to 230 deg C in 60 seconds: 803 * 210 * 0.96 => 162 kJ = 162 kJ/60 seconds => 2.7 kW

Vaporizing it in 60 seconds when at boiling point: 803 gram * 63 J/g => 50.6 kJ => 50.6 kJ/60 seconds => 840 Watt

[cgroen]

Been busy here
My vapor phase oven is taking shape. I have a very good friend that is a mechanical engineer in his day job, so I'm lucky 

Its a ongoing work, so far most of the chamber is designed, the lift system and the heaters. Still missing the details for the lid (the sealing has been taken care of with rubber gasket that goes down in the chamber, the sides at the top is at a slight angle to make it tight.
Below is some screenshots of whats been done so far. The cooling devices are right now being produced (in china), they are made with channels inside and Festo couplings for the water. My plan is to use a "laser tube chiller" (CW5200 with compressor, https://www.teyuchiller.com/co2-laser-tube-water-chillers_p31.html), they can go down to 5 degC (I see ASSCON's device runs at 6 degC, with a low alarm at 5 degC, if I'm not mistaken).
All of the temperature sensors are not going to be mounted, only 3 of them. But as I don't know the exact height, there are 10 different positions to chose from.
In the Galden container, there is a stainless steel tube that will allow water cooling of the Galden (can be activated with a solonid during cooling sequence).

The controller for it are also (almost) finished, still need to figure the best algorithm for soldering, couple of graphs for the temperature sensors etc, right now there is simple support for solder profiles, the lift moves to the correct position etc. Will need to be tweaked once I have a physical oven

Controller uses a NXP processor (LPC54628), has 32 MByte SDRAM, 128 MB filesystem (I know, overspec'd ), H bridge for the lift motor, encoder input for lift, 6 x 3 wire PT100 inputs, 4 x 2 A outputs, 4 x analog/digital 24V inputs, Ethernet and a 4.3" capacitive touch screen (GUI is using littlevGL).

I have uploaded a small video of a run, all with simulated operation. And as I wrote, the actual soldering sequence/profile is no where near how its supposed to be, this was only done to help developing the GUI etc.

I still have a few issues/worries, one of them if the galden container is "large" enough, if its close enough to the walls of the chamber, I guess the vapor will find its way regardless.

Video of controller here:

https://youtu.be/1f__h6oHO9U

[cgroen]

Couple pictures of controller

(still need to implement the graph of the temperature sensors etc)

[rx8pilot]

Couple pictures of controller

(still need to implement the graph of the temperature sensors etc)

Holy hell.....I have some catching up to do 

Looks awesome.

[KaneTW]

Very nice--glad it's coming along well.

[cgroen]

Very nice--glad it's coming along well.

KaneTW,
a lot of it because of your input 

My major concern at the moment is if the heaters will do the job, if they fail, the idea is to make a solid alu block and embed "heating cartridges" in it, clamp it to the bottom of the Galden container, and use that instead.

Once I get something constructed, I will do a proper description, I will also probably publish the files for the mechanics and BOM file

[suj]

Looking at previous professional projects, I was wondering whether to show my realization (still under construction), but maybe someone will be interested. I decided to use the GN container, heating from the outside with an IR heater and cooling with water in an open system. The lid has a gasket and a mounted quartz glass window. A coil made of a capillary tube serves as venting, and a cooling coil is bent from an aluminum tube. I used high-temperature silicone as sealants and assembly adhesive. As a control, I used a PLC from my shelf, I only bought a touch panel for it. As the PLC had analog inputs for temperature conversion I used a K to voltage converter which I bought on ebay. One of the thermocouples is glued with Kapton tape to the bottom of the container (red in the graph), the second thermocouple on the thin wire arm touches the PCB (green) and the third is placed a few centimeters above the PCB (yellow). I used temperature gradients as the setpoint for the PID controller. The slightly strange color of the container on the outside is due to the fact that in order to reduce the reflectivity of IR radiation I used chemical oxidation on stainless steel. I set everything up in the kitchen to have close access to the drain, and it has stayed that way for the last few months  . I need to mobilize myself to put everything in a small control cabinet and do the final cabling. The effects on my amateur level satisfy me. Finally, a few photos of the effects.

[rx8pilot]

 

[julian1]

These consumer "Deep fat fryers", that combine enclosure, top window, heating element, and thermostat look a bit interesting.

https://www.trustedreviews.com/wp-content/uploads/sites/54/2019/10/3-VonShef-1.5L-Stainless-Steel-Deep-Fat-Fryer-768x512.jpg

https://www.trustedreviews.com/reviews/vonshef-1-5l-deep-fat-fryer

There are a bunch of model varations/sizes, but most regulate to 190C as top temperature. Run it open loop and maybe it would hit 230C without futher mods.

Attach a vertical length of copper tubing out the top, like a still/ air-cooled fractionating column to condense the Galden back to liquid. Or glue flexible tubing to the lid, and then run tap water through it.