Mini Blog: IMDES Vapour Phase Purchase - Jumbo.

[mrpackethead]

some thin copper tube (i used 4mm ) bent into a coil that runs around the bottom of the tank, with water flowin thorugh it, worked very well for me to bring the temp down significantly quicker.    Make sure that you run it open,  so if you do create steam,  its got a place to go.   ( dont' run a sealed closed loop ). I was recirculating my water with an aquarium pump,  and getting a 10C rise or so, when the vapour was at max temp.

[WaldMaker]

some thin copper tube (i used 4mm ) bent into a coil that runs around the bottom of the tank,....
I was recirculating my water with an aquarium pump,  and getting a 10C rise or so, when the vapour was at max temp.

Could you please explain the coil position a bit more?

coil = single loop of tube or more?

coming in and out at the same side of the tank or up through the lid?

Bottom = above Galden fluid? How far above ?

around = close to the tank walls ?  How close to wall and the PCB?

recirculating  = running all the time, also when Galden is heated?

How much water do you keep in your water reservoir?

If you cool during vapour is present does the cooling create more thermodynamic movement of the vapour cloud?

I ask this because now the vapour rises up to the lid and condensates on the lid and creates bigger drops of fluid Galden. If the running cooler coil creates a kind of vapour circulation up in the center and down near the walls maybe less would reach the lid?

[mrpackethead]

some thin copper tube (i used 4mm ) bent into a coil that runs around the bottom of the tank,....
I was recirculating my water with an aquarium pump,  and getting a 10C rise or so, when the vapour was at max temp.

>Could you please explain the coil position a bit more?
 
i set it up so it was largely hard up against the sides of the tank. the first few coils sit in the galden. with the remaining ones ( another 6 ) above the cold vapour level.

>coil = single loop of tube or more?

Eight coils stacked on stop of each other.

>coming in and out at the same side of the tank or up through the lid?

I drilled holes in the side of the tank and used some silcone grommets to get a nice fit so it seals nicely around the copper tube.  i have got it coming in and out in the same corner.   

>Bottom = above Galden fluid? How far above ?

Bottom is in the galden () when its cold

>around = close to the tank walls ?  How close to wall and the PCB?

I made it so its sitting hard up against the sides of the tank. Because the tank is slightly tapered it ends up sitting in there without any need for any additional supports etc.

>recirculating  = running all the time, also when Galden is heated?

Just when its cooling.   I picked up control from the exisiting fans.

>How much water do you keep in your water reservoir?

I have about 100L. Its the same tank i use for cooling my laser cutter.     After a few cycles its got a little bit warmer but not crazy warm.   perhaps risen to 30C, from 20C.

>If you cool during vapour is present does the cooling create more thermodynamic movement of the vapour cloud?

I'm not sure I udnerstand your question.      I certainly do make a differnerence in terms of cooling it quicker.  it goes back to just a few minutes, rather than 10-12


>I ask this because now the vapour rises up to the lid and condensates on the lid and creates bigger drops of fluid Galden. If the running cooler coil creates a kind of vapour circulation up in the center and >down near the walls maybe less would reach the lid?

I've done hundreds of cycles in mine, and I'm only loosign very small amounts of galden.  So its not getting out of the tank.  Possibly a bit is left on PCBs.     We are only taking 1-2ml each cycle.    I've not had to add much extra fluid at all.   Somethign to be aware of is that when you first use it after a while is that yo'll likely get quite a lot of steam ( water vapour ) coming off, as the galden is quite hydropscopic. So while you think that you'r loosing galden out the sides, its actulaly only steam.       


I woudl be very keen to collaborate with you on improving this. The IMDES is the right idea. the impmleneation is just terrible.

[WaldMaker]

>Could you please explain the coil position a bit more?
 
i set it up so it was largely hard up against the sides of the tank. the first few coils sit in the galden. with the remaining ones ( another 6 ) above the cold vapour level.

Doesn't the water in the coils start boiling when they sit in the hot Galden?
As you said, the circulation pump is only on when the cooler fans are on.

Most commercial machines have some kind of cooling apparatus at the top part of the tank to produce a condensation zone so that hot vapor does not reach the lid and to form a preheat and cool down zone for those machine that lower the PCB down into the vapor.

Some videos show inline systems where the PCB conveyor runs open above the tank.

In my IMDES machine I observe a kind of vapor "storm" in the tank during the second half of the process time which reaches the lid and leads to several thick drops of Galden.
 
So I think my first "enhancement" will be adding a cooling pipe around the top and see if one can create a "hot tub" of steadily present vapor into which we lower the PCB.
Having built a DIY SMD pick and place machine and 3D printer using a micro-stepped stepper and a belt or spindle drive you can create a very soft running PCB elevator. Problem is how to get through the lid. If we keep the vapor cloud down in the tank then the "danger" of loosing Galden through some kind of pass through is negligible.

I also am enhancing my TC arrangement by using high temperature (295°) solder to fix the TCs to specific solder pads with components attached to be able to best possible measure the temperature profile.
 

I would be very keen to collaborate with you on improving this. The IMDES is the right idea. the implementation is just terrible.

Yes, the direction IMDES shows is right and proves that VPS can be successfully implemented on a low cost level.

I believe it can be improved economically with a bit more sophisticated control, better cooling and some mechanical enhancements.

Therefore I hope this thread can bring ideas and experience together.

[mrpackethead]

Doesn't the water in the coils start boiling when they sit in the hot Galden?
As you said, the circulation pump is only on when the cooler fans are on.

yes, it did.  I had a bit of hotwater, and then a small amoutn of steam.   This is why its really important to have an 'open' end to your pipe, so that if it does boil it has somwhere to go.
what i did to get aroudn this,  ( and i need to get a soliendoi in the mix ), was put my water pump higher than the coil, and put a one way valve on its output.  ( more on that later ).. I also needed to put a "T" in the pipe that i coudl open or close to the environment ).   

When the pump stops, water stops flowing, but it does stay in the pipe because its working against the vacumn that forms after the one way valve.     By opening the pipe to 'the' air, it 'dumps' the rest of the water out. ( its gravity feed ), and so it just free flows out.    Its a bit of a struggle for the water to get out of the coils. I'm thinking that you might consider blowing air in to empty it. but thats yet another improvement.   Because the pump is NOT self priming if you just stop it, and its above the water level of what its pumping it will empty out and then wont' work again.

<quote>
Most commercial machines have some kind of cooling apparatus at the top part of the tank to produce a condensation zone so that hot vapor does not reach the lid and to form a preheat and cool down zone for those machine that lower the PCB down into the vapor.
</quote>

yes, but remember they are continous systems. they never fully cool the galden back to liquid.   ( this woudl be MUCH MUCH faster as the boards only need to be in the galden for a much shorter period. For the low volume stuff, this is not nearly as much of a problme.


<quote>
In my IMDES machine I observe a kind of vapor "storm" in the tank during the second half of the process time which reaches the lid and leads to several thick drops of Galden.
</quote>
That has been an issue for me, but not somethign that particyully is of concern, I've done a lot of boards, and i'm not really loosing any.  Arguably a better shaped lid that has a ridge line might be better, so the galden rolls of the lid aback into the tank

<quote>
So I think my first "enhancement" will be adding a cooling pipe around the top and see if one can create a "hot tub" of steadily present vapor into which we lower the PCB.
</quote>
That will be really interesting to see how it goes.  Its a BIG step in complexity though.