Electronics > Projects, Designs, and Technical Stuff
Vapour phase Soldering
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Kjelt:

--- Quote from: jeremy on January 27, 2015, 09:21:09 am ---I think the more useful characteristic is the vapour "height", which seems mostly to be controlled by temperature/injected energy. The better you can control the vapour height, the better your oven will be.
--- End quote ---
That might be the reason for the three level temperature sensoring, might be necessary for a good level control indication.
jeremy:
Ok, so I've been reading the manual of the weller WAM3000 very carefully, and here is my guess at how it works. Also, nailed down some parameters I think would be reasonable to aim for. See attached for the diagram taken from the weller manual here: http://www.egmont.com.pl/cooper/instrukcje/OI_WAM3000_GB.pdf

The weller machine supports a 300x300x55mm board. I'm guessing the air space cross section in the chamber is maybe 350x350mm ? It also supports a load of maximum 1kg. I have some medium sized steppers lying around from a different project which are rated at about ~3 Nm, so with a small sprocket and chain drive it should easily be able to lift 1kg+1kg platform. This seems like a pretty good target load.

The machine drawing appears to be to scale (all of the external dimension ratios match the machine specs). From this, I have the following very rough measurements:

Full chamber (including gated zone but not including fluid container): 360mm high, 350mm square
Gated location: 120mm from the top of the fluid container
Fluid container: 40mm high, 200mm square

First, you have three sensors. I'm going to assume these are thermocouples, given that the vapour is optically transparent and is extremely chemically inert. The right thermocouple should hopefully have a fast enough response time. (Maybe using those fairly recent 4x4 thermopiles or something could be interesting here. melexis is the company iirc?). Level 1 is closest to the heater at the bottom.

Here are the basic steps:


* Heat the vapour phase fluid until Level 1 reaches the defined preheat temperature
* Open the top door, put your populated board onto a mesh platform. Close the door and press go
* The board is lowered approximately to the level 2 sensor and the gate above the level 3 sensor is closed
* Heat is applied to the fluid until Level 3 reaches the defined finish temperature. The vapour will not rise that high unless the PCB is unable to absorb any more heat; this means that basically condensation has stopped and the solder should be fully reflowed
* Heat is reduced and external cooling fans are turned on. After level 2 drops below a defined temperature, the gate will be opened and the mesh platform will be lifted
* Enjoy your freshly soldered PCB!
PS while I'm not saying anyone should throw out your soldering irons, have you seen the price of the high end weller/pace/ersa/metcal gear? It makes the fluid look very cheap in comparison! ;) I think that an entire DIY vapour phase setup (with fluid) would cost less than one of my weller stations, and I have two of them!
mrpackethead:
So, i think we have a good solution for our vapour fluid.    (  further distilled Galden HT230 ).     Time to move on a little.

Theres a lot of variables here, that we don't have a good handle on. but some guidance from the commercial machinese is helpful.

Heres my thoughts on the other topics.

(a) the Weller and that other machine we saw,  both suggest using about 1kg of Fluid in their machines,   Thats only about 600ml.   My suspision is that you don't need much fluid to make quite a lot of vapour.

(b) the commercial machines all seem to have a small "well" in the bottom of their tanks, you  don't need to cover the entire base

(c) Heating almost certainly should be by some kind of external heater rather than an immersion one.   Plenty of options there, and it really needs to be closed loop control system.   We want to provide enough energy, but not too much.      For experimentation purposes I'm thinking that it will be very useful to measure temp at several locations..   I'm thinking   

- in the fluid to be boiled
- on a aluminium block that can be raised and lowered,  this in many ways can be used to simulate your 'load'.   
- Some sensors further above the vapour.

My feeling is that if we cafefully control the heating, then vapor loss is going to be minimal.   Look at this video ( ).  There is nothing elaborate about their 'tower'.

Time to stop talking and order some fluid and get started.


jeremy:

--- Quote from: mrpackethead on January 27, 2015, 07:01:29 pm ---So, i think we have a good solution for our vapour fluid.    (  further distilled Galden HT230 ).     Time to move on a little.

Theres a lot of variables here, that we don't have a good handle on. but some guidance from the commercial machinese is helpful.

Heres my thoughts on the other topics.

(a) the Weller and that other machine we saw,  both suggest using about 1kg of Fluid in their machines,   Thats only about 600ml.   My suspision is that you don't need much fluid to make quite a lot of vapour.

(b) the commercial machines all seem to have a small "well" in the bottom of their tanks, you  don't need to cover the entire base

(c) Heating almost certainly should be by some kind of external heater rather than an immersion one.   Plenty of options there, and it really needs to be closed loop control system.   We want to provide enough energy, but not too much.      For experimentation purposes I'm thinking that it will be very useful to measure temp at several locations..   I'm thinking   

- in the fluid to be boiled
- on a aluminium block that can be raised and lowered,  this in many ways can be used to simulate your 'load'.   
- Some sensors further above the vapour.

My feeling is that if we cafefully control the heating, then vapor loss is going to be minimal.   Look at this video ( ).  There is nothing elaborate about their 'tower'.

Time to stop talking and order some fluid and get started.

--- End quote ---

The weller has a sensor in the fluid as well. And to simulate your load, why not just get an already soldered PCB?

I am going to try 1/4" ASTM420 stainless ball bearings in a pyrex beaker (currently in the mail) and an induction hot plate; I think this alloy will work. I'm also trying to get a board manufactured with some 0.5mm pitch BGAs for testing, but that's proving to be quite difficult (in fact, at this stage one board would cost more than 1kg of galden due to the 3/3mil traces required).

Also, from that video:
chain driven lift: check
linear guides: check
guides don't extend all the way into the fluid, but get close: check


Unfortunately though I am away from home for a month, so no playing with toys for me.  :'(
mrpackethead:


--- Quote ---The weller has a sensor in the fluid as well. And to simulate your load, why not just get an already soldered PCB?

--- End quote ---

because i'll be able to easily make a nice fitting for a thermocouple and it will be completely consistent. 
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