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

[mrpackethead]

some more experimenting, and some interesitng observatrions;

(a) the height of galden vapor above its liquid is can be controlled, ( once its vapourizing ), by controlling the amount of power you supply to the system..    With a PID control loop it appears that it is quite possible to maintain quite a tightly controlled vapor cloud height.   (+/-5mm is easy )

(b) putting an object above the galden liquid ( such a a pcb or a wire mesh ) largely 'stops' the vapour from rising further utill the object is nearly at the vapourisation temp.   

(c) the 'air' thats in teh 20mm above the vapour ranges from 120 to 160C.. Nearly perfect for the pre soak.

[rx8pilot]

some more experimenting, and some interesitng observatrions;

(a) the height of galden vapor above its liquid is can be controlled, ( once its vapourizing ), by controlling the amount of power you supply to the system..    With a PID control loop it appears that it is quite possible to maintain quite a tightly controlled vapor cloud height.   (+/-5mm is easy )

(b) putting an object above the galden liquid ( such a a pcb or a wire mesh ) largely 'stops' the vapour from rising further utill the object is nearly at the vapourisation temp.   

(c) the 'air' thats in teh 20mm above the vapour ranges from 120 to 160C.. Nearly perfect for the pre soak.

This is good information.
It seems that moving the Galden tray as a partial control for the temp profile is a better option than moving the PCB itself. A modestly tight PID of the galden temp and a simple motion system for the cloud could yield just about any profile.
For my larger scale experiment - I am looking at commercial oven windows so I can easily see what is happening from the side. So far, that does not seem all that difficult and should help get things dialed in quickly by having both thermocouples and visual cues.

[mrpackethead]

It seems that moving the Galden tray as a partial control for the temp profile is a better option than moving the PCB itself. A modestly tight PID of the galden temp and a simple motion system for the cloud could yield just about any profile.

I suspect that might be more complex than you expect.   If you 'dropped' the galden tray, you will still have 'energy' in the surrounding container, which will mean that the cloud probably will get wider for a little time, and then sink down and find a new point of equilibrium.   Like wise,  if you move it up, you'll intially compress the cloud and then the surrounding container reaches temp, it will rise..    It does not take much mass to cause the cloud to 'stall' while that mass comes to the vapor temp.     

All that said, its an interesting idea and one that might have some merit.   I'm pretty convinced that i wont' need to implmenet any moving parts,  and the system will be able to be kept exceptionally simple, and low cost.   The sacrifice might be in throughput.  Having said that though,  This is system will be so cheap, that scaling out will be a very viable option.

[/quote]
For my larger scale experiment - I am looking at commercial oven windows so I can easily see what is happening from the side. So far, that does not seem all that difficult and should help get things dialed in quickly by having both thermocouples and visual cues.
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The galden vapour itself does not show itself up visibly that much..   Most of any visible cloud tends to be water vapour.

[ChristopherN]

The shallow pan I bought is too shallow. It heats up fine but the lid leaks a lot of vapor. It seems like big stainless vessels are kind of hard to find, I need something that can fit a 450*350mm board.

Any ideas?

[SMTech]

Probably not as easy to find online but cheesemaking & brewing equipment would be an interesting place to look. Lots of big stainless containers and the engineers/service people in those industries often have the fabrication skills to make it too. Hanging out at a few bankruptcy sales could also work...

[Kjelt]

trying to imagine a large pot, but what came to mind is the caterers thingy. made a little search, saw some chafing dish 22x14inch @ amazon. could be cheaper on aliexpress. 

The issue is to heat this thing to 230C without putting a heater in.
These things usually go to 90C to keep food warm, this can be easily done by heating the bottom. But bypassing the thermostat and temperature fuses and to heat the bottom to 230C could give problems, perhaps the whole outside will warm up over 150C for instance.

[mrpackethead]

The shallow pan I bought is too shallow. It heats up fine but the lid leaks a lot of vapor. It seems like big stainless vessels are kind of hard to find, I need something that can fit a 450*350mm board.

Any ideas?

If you can visibly see much  vapour its more than likely to be water vapor,..  I've run my 10cm deep pan now 12 time or so, and i've not lost any noticeable galden from it. 

[mrpackethead]

trying to imagine a large pot, but what came to mind is the caterers thingy. made a little search, saw some chafing dish 22x14inch @ amazon. could be cheaper on aliexpress. 

The issue is to heat this thing to 230C without putting a heater in.
These things usually go to 90C to keep food warm, this can be easily done by heating the bottom. But bypassing the thermostat and temperature fuses and to heat the bottom to 230C could give problems, perhaps the whole outside will warm up over 150C for instance.

This is why the frying pan is so good.

[mrpackethead]

I was able to achieve a much better curve with some PID based ( in python ) control of the heater, with a thermocouple.. I was able to slow down ( and stop the heat up ) to create a short soak..   This is certainly not an ideal profile curve yet, but i'm now confident that i can get there with some more iterations and tuning. 

In the mean time, i've decided the the quickest way to move this off a PC platform is to use an Ardunio.. Theres some good PID librarys for that as well.      Because i'm using a DMX512 lighting control pack to control the pan, i'll use a DMX sheild to control it.   For a more practical solution this just needs to be a phase controlled triac circuit.   But i'm using what i have, and I eventually think i'll run several of these side by side, and it has 12 channels, and its spread across 3 phases.

[mrpackethead]

Pile of bits and peices for hte frying pan!

Will start building this up now,  planning to make it run on a ardunio.

[rx8pilot]

Oooooh! This is awesome. Can't wait to see the follow up.

Typet purly on my fone.

[mrpackethead]

Aliexpress the home of cool useful low cost, sometimes dubious gear.   All came with valid descriptions though.

[pisoiu]

While reading various information about vapor phase soldering, I noticed that in almost all discussions/videos/examples, it is assumed that one board is lowered into vapor for soldering. But how about stacked boards/panels put one above each other in a supporting frame, for increased throughput? Is any reason not to do this, as long as vapors encompass the whole stack from top to bottom ? Thank you.

[mrpackethead]

I have stacked four boards high, and had good results. Its a good way of upping your through put significnatly.

The challenge is stacking them and not disturbing the components while they are still on unfryed paste.

[rx8pilot]

I have stacked four boards high, and had good results. Its a good way of upping your through put significnatly.

The challenge is stacking them and not disturbing the components while they are still on unfryed paste.

Did you have to fabricate some sort of fixture to accomplish this? I like the idea but only if I can easily and reliably stack them without bumping parts around.

[pisoiu]

I purchased some aluminium profiles, that kind used in frames of 3d printers. They can be easily assembled together and have some channels in which a panel could slide easily. I don't see why this would not work.
https://www.tme.eu/ro/en/details/k2020-i5_2m/aluminium-profiles/kraftberg/k2020-i5-2m/

I also got some galden from eleshop, I am thinking to make some tests with vacuum vapor phase soldering, to see if I can build something usable for small batches.
My starting point would be to use a stainless steel pressure cooker. It has a solid frame, sealed container, usually sloped lid to drain top condensed galden, the lid has ports where I can connect vacuum pump, etc. Also easy to heat with induction.
Problems so far is to find a big enough vessel for my panels. Biggest I was able to find so far has 36cm in diameter. I also have some concerns about the sealing ring, I'm not sure it will hold 230 degrees.

[mrpackethead]

I have stacked four boards high, and had good results. Its a good way of upping your through put significnatly.

The challenge is stacking them and not disturbing the components while they are still on unfryed paste.

Did you have to fabricate some sort of fixture to accomplish this? I like the idea but only if I can easily and reliably stack them without bumping parts around.

I just used some nuts as spacers. :-)    not exactly high tech, and  very prone to bumping, but it did work.

[Kjelt]

Again I look at the pro machines and see that none AFAICT stack the pcb's, why ?
My guess is that this is because the temperature differs with the height/distance in the mist.
For DIY projects this is perhaps not a problem, you probably keep heating till the heighest boards also reach the target 230C and reflow but by then the lower boards probably have been too long in the 230C region.
The pro machines have traceability of the reflow curve, they need this for their customers to proof they kept to the standards in case some boards prematurely fail due to heat stress or other causes.

[pisoiu]

That's a good observation. I imagine that could happen in the heating phase where I assume that vapors displaces the above atmosphere gradually, therefore different heights have different temperature profiles. Perhaps things are different when using vacuum. I have some galden on the road, I still have to find a closed container and a vacuum pump, I'll try to make some tests.

[KaneTW]

Be aware that the boiling point of liquids changes with pressure. Generally, the vacuum is pulled after the solder paste has melted (this will require a cold trap or similar to prevent Galden loss, and your pump will need to be able to hot process gasses).

[pisoiu]

My plan was to create vacuum at the beginning. I actually think to use boiling point variation vs pressure to my advantage, lower pressure means lower boiling point.
I make some assumptions here, maybe I'm wrong, but the timing of events would be:
-put boards, close container
-create vacuum, not very hard, what allows a cheap 1 stage pump
-if I start to heat galden, boards won't actually increase temperature until vapors reach their surface. Lower boiling point means galden will evaporate sooner than 230C, (boiling point at 1 bar). This should help with temperature gradient. Avoids situation when vapors touch boards only when they are very hot and cause sudden increase in temperature. During this process, pressure inside container should gradually increase due to presence of vapors. By controlling carefully quantity of liquid galden versus container volume, should be easy to calculate needed galden qty to obtain 1 bar when vapors reach 230C, in this situation, inside pressure is equal with outside pressure, therefore we have same boiling point. Am I wrong?
-stop heater, cooling by whatever means necessary to control cooling slope, creating vacuum again inside
-when temperature is low enough, slowly allow air inside until pressure equalizes, then open container.


le: thinking of it, I may need to create a system to insert galden into container only after vacuum is created, otherwise I may extract galden vapors during vacuum creation process...

[KaneTW]

Unless you keep pumping off vapor, the pressure in the tank will eventually increase due to evaporation of Galden. A 10 liter volume will be at atmospheric pressure after 250g of Galden have evaporated (via ideal gas law, with Galden having a molar mass of 1020g/mol). You'd need to run some simulations or calculations to determine the temperature gradient.

Galden's boiling point at 10mbar is 112C (http://www.trimen.pl/witek/calculators/wrzenie.html + datasheet values for Galden). However, it rises pretty quickly, with a BP of 207C at just half atmospheric pressure. That seems like too steep a gradient to me, so you'd have to continue to pump off and control the vacuum meticulously to ensure a good profile.

In most commercial machines, a profile is implemented by hovering the boards above the vapor front. I'm not sure if you could mix several different Galden types and get a layered system that way, though.

Some further reading re: profile:
http://www.torenko.com/pdf/Todays-Vapor-Phase-Soldering-Tech-Paper.pdf
https://ieeexplore.ieee.org/document/6102707

[pisoiu]

In most commercial machines, a profile is implemented by hovering the boards above the vapor front.

And probably this is why they do not stack boards.

[mrpackethead]

Again I look at the pro machines and see that none AFAICT stack the pcb's, why ?
My guess is that this is because the temperature differs with the height/distance in the mist.
For DIY projects this is perhaps not a problem, you probably keep heating till the heighest boards also reach the target 230C and reflow but by then the lower boards probably have been too long in the 230C region.
The pro machines have traceability of the reflow curve, they need this for their customers to proof they kept to the standards in case some boards prematurely fail due to heat stress or other causes.

My observation is that the delta T in the dense vapour is very small.   The height of the dense vapour is largely proportional to the amount of energy that you continue to supply once the liquid galden has reached boiling point.,   The vapour cloud will rise very quickly to its 'level',  definatly a short enough time that you can create a useful cloud of say 50mm within 3-4 seconds. 

[Kjelt]

Again I look at the pro machines and see that none AFAICT stack the pcb's, why ?
My guess is that this is because the temperature differs with the height/distance in the mist.
For DIY projects this is perhaps not a problem, you probably keep heating till the heighest boards also reach the target 230C and reflow but by then the lower boards probably have been too long in the 230C region.
The pro machines have traceability of the reflow curve, they need this for their customers to proof they kept to the standards in case some boards prematurely fail due to heat stress or other causes.

My observation is that the delta T in the dense vapour is very small.   The height of the dense vapour is largely proportional to the amount of energy that you continue to supply once the liquid galden has reached boiling point.,   The vapour cloud will rise very quickly to its 'level',  definatly a short enough time that you can create a useful cloud of say 50mm within 3-4 seconds.

So next experiment is to stack lets say three levels of boards attach a thermocouple to each board and log the temperature reflow curve from start to finish. Show the results. I can predict they are way off the ideal reflow curve esp the soaking time at 160C and the final 230C time will be exceeded for the lower board and not met with the upper board or any shift depending in the actual movement of the boards and rise of the mist.
It is a nice idea but not one that companies building VP machines since the 80s would not have thought off.
Instead they create the extra space in the existing 2D tray space.
Just my two cents, but its a science forum, do the experiments.