Author Topic: Practical DIY or modest cost Vapor Phase - does it exist yet?  (Read 10240 times)

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Offline mrpackethead

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Re: Practical DIY or modest cost Vapor Phase - does it exist yet?
« Reply #175 on: November 11, 2019, 06:52:39 pm »
Would something like a 20q/l roasting oven be a useful starting place? 
too shallow unless you are willing to loose Galden, which is much more expensive than that oven.

Actually, maybe not.  My work with using the frying pan says that you can have a shallow pan.  The galden is actually reletively contronable.   that is not the problem that you solve with using a deep container.    Using the deep container lets you build MUCH better profiles, becuase you can build the elevator platform. That is the game changer.   I had avoided it, because I could not come up with a mechanically simple way to build it.  What Lukas05 has done is come up with a mechanically simple way to make it work. That is the game changer.

I scoured Aliexpress looking for a deep Dish, and have failed. :-(



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Online pisoiu

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Re: Practical DIY or modest cost Vapor Phase - does it exist yet?
« Reply #176 on: November 11, 2019, 08:15:12 pm »
I scoured Aliexpress looking for a deep Dish, and have failed. :-(

Same here with aliexpress but there may be another way. I made some tests with that kind of rectangular containers which are used to serve icecream and food in malls. Don't know what they are called. But that format has maximum 200mm depth. I wanted deeper and I was able to find at a local dealer of stainless steel supplies. Among other things (tubes, bars, various containers), they sell containers for dish washing in restaurants. I find those suitable, they are quite big, and they have another feature, the bottom is slightly sloped, which in my opinion is a good thing to use the deepest part for heater.
Check this pdf: http://www.italinox.ro/images/pdf/gastronorm.pdf , at page 4 and 5 you will find them. Texts are in Romanian but images and drawings are self explanatory. Walls are 1mm thick and 330mm depth seem ok for this application.
 


Online Kjelt

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Re: Practical DIY or modest cost Vapor Phase - does it exist yet?
« Reply #178 on: November 11, 2019, 10:41:16 pm »
rectangular containers which are used to serve icecream and food in malls. Don't know what they are called. But that format has maximum 200mm depth.
those are standard for the horeca and called Gastronorm.

You can use it as the base that contains the fluid and get a stainless steel plate chassis welded upon it as high as you want.
 

Offline mrpackethead

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Re: Practical DIY or modest cost Vapor Phase - does it exist yet?
« Reply #179 on: November 11, 2019, 11:11:43 pm »
Quote
I scoured Aliexpress looking for a deep Dish, and have failed. :-(
Really ?  :o

Dish as opposed to Pot.  Being round, it makes it difficult to attached flat plate water coolers ( as used for GPU's etc ) which are readily avaialble and cost effective.     It seems that Gastronorms max out at 200mm deep.



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Offline mrpackethead

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Re: Practical DIY or modest cost Vapor Phase - does it exist yet?
« Reply #180 on: November 12, 2019, 05:24:40 pm »
I scoured Aliexpress looking for a deep Dish, and have failed. :-(

Same here with aliexpress but there may be another way. I made some tests with that kind of rectangular containers which are used to serve icecream and food in malls. Don't know what they are called. But that format has maximum 200mm depth. I wanted deeper and I was able to find at a local dealer of stainless steel supplies. Among other things (tubes, bars, various containers), they sell containers for dish washing in restaurants. I find those suitable, they are quite big, and they have another feature, the bottom is slightly sloped, which in my opinion is a good thing to use the deepest part for heater.
Check this pdf: http://www.italinox.ro/images/pdf/gastronorm.pdf , at page 4 and 5 you will find them. Texts are in Romanian but images and drawings are self explanatory. Walls are 1mm thick and 330mm depth seem ok for this application.

Yes, it seems that the 'Gastronorm' maxes out at 200mm.  They all come in standard sizes.
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Offline Lukas05

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Re: Practical DIY or modest cost Vapor Phase - does it exist yet?
« Reply #181 on: November 15, 2019, 11:12:52 pm »
Hi,

since some of you liked the project, I thought I would continue documenting the progress :)

A problem occured in the last run of the vapor phase oven. The container is sealed pretty good at the moment. There is only a small hole in the side wall for the heating element cables.
This poses a problem when it comes to pressure equalisation. The relatively cold PCB is lowered into the vapor phase. A lot of the gas condenses onto the cold surface in the first few seconds.
This causes the pressure in the system to drop, and air from the outside rushes into the chamber. This by itself isn´t a problem. But it gets problematic when lifting the hot PCB out of the vapor phase.
By lifting up the hot board into cooler parts of the chamber, the pressure rises. This causes galden vapor to get pushed out of the chamber. This of course means unwanted galden loss over time.
Currently I´m designing sorf of a reflux condenser. This will probably just be a 6mm copper pipe bent into an air cooled coil. The galden condenses in the pipe, and flows back into the container, while also providing a controlled pressure equalization.

I´m goint to verify this design in a FEM simulation. I´ve already startet so simulate parts of the project, to get some ideas of the material stresses and also transient behaviour of the system.
This will also be the foundation along with the measurements for the temperature profile regulator. I will post the results once I have calculated them through.

The post process of the coupled cfd simulation looks beautiful already I think :)
Here you can see the convection of the galden until 30 seconds after turning on the heating element.

https://www.flickr.com/photos/136915492@N02/49070612068/in/dateposted/
« Last Edit: November 15, 2019, 11:14:24 pm by Lukas05 »
 

Online Kjelt

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Re: Practical DIY or modest cost Vapor Phase - does it exist yet?
« Reply #182 on: November 16, 2019, 08:18:52 am »
Wow you are really taking it a step further  :-+
Just trying to think along could it be that your base carrier plate is to massive, taking too much Galden up?
If I look at this pro machine the boards carrier is only a wire mesh
https://youtu.be/jVQTcViEaUk
 

Offline mrpackethead

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Re: Practical DIY or modest cost Vapor Phase - does it exist yet?
« Reply #183 on: November 16, 2019, 10:20:17 am »
Wow you are really taking it a step further  :-+
Just trying to think along could it be that your base carrier plate is to massive, taking too much Galden up?
If I look at this pro machine the boards carrier is only a wire mesh
https://youtu.be/jVQTcViEaUk

You'd get the same issue, if you have a pcb that is large ( its also solid ).     

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Offline mrpackethead

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Re: Practical DIY or modest cost Vapor Phase - does it exist yet?
« Reply #184 on: November 16, 2019, 10:33:39 am »
A problem occured in the last run of the vapor phase oven. The container is sealed pretty good at the moment. There is only a small hole in the side wall for the heating element cables.
This poses a problem when it comes to pressure equalisation. The relatively cold PCB is lowered into the vapor phase. A lot of the gas condenses onto the cold surface in the first few seconds.

This would absolutely be correct.  This raises another problem. If you lower the PCB into the Galden too fast, your re flow profile is going to be way too steep on the way up.    With the 'static' frying pan method, i was effectivel 'preheating' the pcb. ( giving it a soak period ) by regulating the amount of energy that was going into the system.    If you were to monitor the temp of the PCB,  ( you'd need a thermocouple attached it ), you' would be able to control the rate at which it heated up quite well.  Above the 'thick' galden cloud, is a 'soft' cloud, and that vapour provides a pretty useful way of getting teh board up to a temp 10 lower than the melt point of the solder paste.

Galden vapour is easy to disturb. you only need a tiny draft and you'll blow it out of the tank.  However, If its 'still', it really does sit nicely, and unless you put LOTs of energy into it, its easy to keep it in the tank.     Moving PCB's in and out of the vapor does create a lot of movement.


This causes the pressure in the system to drop, and air from the outside rushes into the chamber. This by itself isn´t a problem. But it gets problematic when lifting the hot PCB out of the vapor phase.
By lifting up the hot board into cooler parts of the chamber, the pressure rises. This causes galden vapor to get pushed out of the chamber. This of course means unwanted galden loss over time.

Quote
Currently I´m designing sorf of a reflux condenser. This will probably just be a 6mm copper pipe bent into an air cooled coil. The galden condenses in the pipe, and flows back into the container, while also providing a controlled pressure equalization.

That has proved to be an effective way of keeping galden in teh tank as well.  I tryed using it to cool my frying pan project, and it worked.     The big problem with teh frying pan project is that while i can get really good results,  its a very long cycle time..  as the galden goes from cold to nearly cold, and thats the best part of 15 minutes.

Your design is really very clever using the cable lifts.    Some of the commerical VP machines bring the board out of the vapour into the top of tank, and then a door closes between teh board and the bottom of the tank.   I think thats doable with another cable lift.   I'll try and draw a picture tommorrow of what i mean. 
If that could work, you'd be able to get great cycle times, becuase you'd probably nto even need to cool the galden down.

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Offline Lukas05

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Re: Practical DIY or modest cost Vapor Phase - does it exist yet?
« Reply #185 on: November 16, 2019, 03:26:54 pm »
Hi,

Quote
If you were to monitor the temp of the PCB,  ( you'd need a thermocouple attached it ), you' would be able to control the rate at which it heated up quite well.

I think this is the route I will go with this. The mass of the PCB varys a lot potentially from small PCBs with 0.8mm thickness, to 2.4mm multilayer boards with huge inductors.
This of course influences the time constant of the thermal low-pass wich ist formed with the heat capacity of the PCB. I´m thinking of an easy mechanism that presses a thermocouple on the PCB.... (not so sure how I would tackle this right now)
Another approch I had in mind would be to fixate a thermocouple on a small PCB with a ground plane that is installed permanently somewhere where it doesn´t take up much space.

Quote
Some of the commerical VP machines bring the board out of the vapour into the top of tank, and then a door closes between teh board and the bottom of the tank.

Yeah the two chamber design is very common it seems. I´m not sure if I want to install something similar, since it adds quiet a bit complexity an potentially BOM cost to the project.
Since I don´t need very low cycle times I think I will first evaluate the quick cool concept in detail. If I´m not satisfied with the result I will investigate the two chamber hybrid.

Quote
Just trying to think along could it be that your base carrier plate is to massive, taking too much Galden up?

Yes I think I will also swap that base out for something that has a higher "hole-to-metal" ratio.
« Last Edit: November 16, 2019, 03:30:15 pm by Lukas05 »
 


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