Electronics > Projects, Designs, and Technical Stuff
Vapour phase Soldering
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SeanB:
You are only using the vapour, so it is not worried much by flux and other residues. Eventually you just run it with a drip tray collecting the condensed liquid till it is dry below and with the now distilled liquid up in the top. Then clean the boiler area and reuse the fluid.
mrpackethead:
(1) do you need to do anything in terms of pre-heating your board before it goes into the vapour?

(2) How "thick" is the vapour layer above the liquid.

(3) Im thinking that a 'lid' that has a stack of aluminium heat sinks that sits over the tank might be quite good a well.

(4) If the board is sitting flat, after it is raised out of the vapour,  the vapour could potentially condense and sit on the board, ( once its cold ).   Maybe when you pull it up, it needs to be angled once the solder is solid?

(5) Double sided..  Just rely on surface tension?
coppice:

--- Quote from: mrpackethead on January 22, 2015, 08:38:14 am ---(1) do you need to do anything in terms of pre-heating your board before it goes into the vapour?

--- End quote ---
Not really. Just don't heat too quickly, so the vapour has time to warm the components through.  While the core of the components is still drawing heat from the surface you won't get a good flow of solder. That might not be a big issue with small components, but it can be with big chunky power ones.

--- Quote from: mrpackethead on January 22, 2015, 08:38:14 am ---(2) How "thick" is the vapour layer above the liquid.

--- End quote ---

--- Quote from: mrpackethead on January 22, 2015, 08:38:14 am ---(3) Im thinking that a 'lid' that has a stack of aluminium heat sinks that sits over the tank might be quite good a well.

--- End quote ---
I'm not clear what you are trying to achieve there? It seems like that just going to make the fluid condense on the lid instead of the board. The whole things works by the latent heat of condensation ending up in the components.

--- Quote from: mrpackethead on January 22, 2015, 08:38:14 am ---(4) If the board is sitting flat, after it is raised out of the vapour,  the vapour could potentially condense and sit on the board, ( once its cold ).   Maybe when you pull it up, it needs to be angled once the solder is solid?

--- End quote ---
That isn't a problem when things are done right. If the vapour pressure is greatly reduced while the board is still warm, the fluid evaporates. The board should come out dry.

--- Quote from: mrpackethead on January 22, 2015, 08:38:14 am ---(5) Double sided..  Just rely on surface tension?

--- End quote ---
Yes. Make sure nothing jolts that board before soldering.  :) Alternatively glue spot.
jeremy:

--- Quote from: mrpackethead on January 22, 2015, 08:38:14 am ---(1) do you need to do anything in terms of pre-heating your board before it goes into the vapour?

(2) How "thick" is the vapour layer above the liquid.

(3) Im thinking that a 'lid' that has a stack of aluminium heat sinks that sits over the tank might be quite good a well.

(4) If the board is sitting flat, after it is raised out of the vapour,  the vapour could potentially condense and sit on the board, ( once its cold ).   Maybe when you pull it up, it needs to be angled once the solder is solid?

(5) Double sided..  Just rely on surface tension?

--- End quote ---

1) yes, otherwise you will risk tombstoning or wicking. It's actually more of a problem with smaller components apparently because they will heat much faster than the pads. 150C preheat makes this problem basically go away. Source is in one of my previous posts in this thread. Usually an different batch oven is used, but that's only because in production everything needs to go super fast.

2) depends on the amount of heating. Seems like as long as the board is in the vapour and not the fluid it will be ok. If you're talking about density, it is heavier than air.

3) yes, or maybe some of those watercooling blocks from overclocking kits too? coppice: you want the fluid to condense on the lid so that it doesn't escape.

4) I don't see why you couldn't just wash the board with distilled water in place after everything had cooled down, then just run the thing on 120C for a bit to evaporate the water. When I finally get hold of some galden or fluorinert (I'm trying to get 500mL, but the cheapest I've got so far is about AU$1200 for 3.8L), I think it would be good to do some experiments to see just how much loss you get when you do something like this.

5) thermosetting epoxy designed for smd is not that expensive, and I've got it from RS in the past in plastic syringe form. I'd post the link, but I'm getting "RS Online is temporarily unavailable."

Cleaning the fluid should be straightforward. You can get a liebig condenser on ebay from china for like $30.

free_electron: nice pic. what did you draw it in?
coppice:

--- Quote from: jeremy on January 22, 2015, 08:53:12 am ---3) yes, or maybe some of those watercooling blocks from overclocking kits too? coppice: you want the fluid to condense on the lid so that it doesn't escape.

--- End quote ---
As the vapour is heavier than air, why would it escape? You aren't going to lift the lid until the vapour pressure has dropped.

--- Quote from: jeremy on January 22, 2015, 08:53:12 am ---5) thermosetting epoxy designed for smd is not that expensive, and I've got it from RS in the past in plastic syringe form. I'd post the link, but I'm getting "RS Online is temporarily unavailable."

--- End quote ---
The material is cheap, but applying it can be a pain. People don't really like doing this, unless its being done by a fully automated machine that tightly controls quantities. If you dispense just a little too much, or don't place it accurately,  it can spread onto the pads, especially if the parts are very small.

Take what I say with a pinch of salt. I'm basing what I say on results in the 1980s with lower temperature fluid and leaded solder.
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