Vapour phase Soldering

[tautech]

Can't this type of reflow be achieved using less expensive liquids?

We'd all like to know that too, but how they might behave at elevated temperatures is the unknown. 
Contamination of the reflow MUST be of primary concern would you not think?
Then there is the interaction with any componentry also to consider.

Inert, non-toxic tailored reflow fluids seem the best option to me.

[IanB]

Can't this type of reflow be achieved using less expensive liquids?

I would look at a convection oven using circulating hot air. Air is cheap and easily obtained, and the circulation currents lead to even heating and good heat transfer.

A possible design could include an electric hot air gun as a heat source and a triac dimmer for temperature control. The hot air gun comes with its own fan, so you only need to put together a suitable insulated enclosure with a window and some suitable baffles for good circulation. The temperature sensor could be placed in the exhaust port and measure the air temperature leaving the oven.

[tautech]

Can't this type of reflow be achieved using less expensive liquids?

I would look at a convection oven using circulating hot air. Air is cheap and easily obtained, and the circulation currents lead to even heating and good heat transfer.

A possible design could include an electric hot air gun as a heat source and a triac dimmer for temperature control. The hot air gun comes with its own fan, so you only need to put together a suitable insulated enclosure with a window and some suitable baffles for good circulation. The temperature sensor could be placed in the exhaust port and measure the air temperature leaving the oven.

Sorry Ian, but have you read the whole thread?
One of the benefits of VP is the inert atmosphere of the vapour, the main reason to investigate this technology.

[IanB]

Sorry Ian, but have you read the whole thread?
One of the benefits of VP is the inert atmosphere of the vapour, the main reason to investigate this technology.

I understand that, but I have not seen the argument that the inert atmosphere is important. Is it common to use an inert atmosphere in industrial reflow soldering processes today? If soldering today was done in an argon atmosphere I would see the point, but I'm not sure that is the case. It's my understanding that the solder flux forms a protective film between the air and the molten solder and this is a sufficient barrier to keep oxygen away.

[helius]

using a nitrogen blanket in an inline reflow machine seems fairly common.
There seem to be some untrue rumors about it going around, though:
http://blogs.indium.com/blog/semiconductor-and-power-semi-assembly/dispelling-10-myths-about-nitrogen-reflow-part-i

[IconicPCB]

About 20 years ago  I sold the first nitrogen atmosphere wave soldering machine in Australia.

You could see the solder pot surface remain dross free as the oxygen level inside the process tunnel went down. Minimum flux was required to get good solder joints.

In fact the difference in density between flux and flux solvent was imperceptible attesting to the low solids flux.

[jeremy]

Is stainless steel really a requirement?

I mean if fluid is inert it ought not contribute to corrosion process in any way.

Why does it need to be stainless steel why not ordinary galvanized sheet metal ?

I don't think so. Most cooking ovens I have seen are not made of stainless, so I don't see why galvanized metal would be a problem. Much easier to weld shut too.

Zapta: I think at higher pressures you will change the melting point of the solder. Also, you could possibly force the fluid into the fr4 or other parts.

[Kjelt]

Actually Ian has a fairly good point I think.
If you have a large vessel with at the bottom a controlled oven heated 230

o

C area filled with Argon gass (which is heavier than air so will stay at the bottom) it would still be a matter of slowly lowering the pcb inside the area till the temp profile is correct.
Only problem I see is that hot air rises up so you have less controlled heating profile unless you let the pcb slide in from aside instead of above but then you have chance of loosing Argon.
We need a mechanical engineer here to sort this out 

[tautech]

Actually Ian has a fairly good point I think.
If you have a large vessel with at the bottom a controlled oven heated 230

o

C area filled with Argon gass (which is heavier than air so will stay at the bottom) it would still be a matter of slowly lowering the pcb inside the area till the temp profile is correct.
Only problem I see is that hot air rises up so you have less controlled heating profile unless you let the pcb slide in from aside instead of above but then you have chance of loosing Argon.
We need a mechanical engineer here to sort this out 

For a hobbyist to buy and keep an Argon supply on hand will cost more than the litre of Galden.

[mikeselectricstuff]

For a hobbyist to buy and keep an Argon supply on hand will cost more than the litre of Galden.

You can get disposable cylinders of argon for welding - about GBP17 in the UK

[MK]

Air, density about 1.2 Kg m3, Argon about 1.6 Kg m3, galden ht230 has a molecular weight of about 1000, so ~26kg per m3
www.g-werner.at/de/downloads/solvay_solexis_galden.pdf

I think the argon will be superfluous.

[Kjelt]

For a hobbyist to buy and keep an Argon supply on hand will cost more than the litre of Galden.

I have a 5 litre tank for my wine hobby 
If I remember correctly (couple of years back) you buy the tank for around 100 euro's and next time only pay the refills (you exchange the cylinder for a filled one) costing 18 euro's or something like that. Only problem is safety if it leaks in a closed environment there will be no air to breath. But than if you have a small cylinder this would not pose a big problem.

[Kjelt]

Air, density about 1.2 Kg m3, Argon about 1.6 Kg m3, galden ht230 has a molecular weight of about 1000, so ~26kg per m3
I think the argon will be superfluous.

What do you exactly mean, superfluous?  Google translation says "not necessary",  but the argon prevents the oxydation if you use simple hot air reflow and do not use galden. Yes if you use galden Argon is useless.

[tautech]

For a hobbyist to buy and keep an Argon supply on hand will cost more than the litre of Galden.

Good to see that not everybody gets raped on industrial gas pricing like we do in NZ.
Bottle hireage ~$120/year
Re-fillable bottle purchase $500 up
2 m³ fill ~$80

Hence the reason behind my statement

Air, density about 1.2 Kg m3, Argon about 1.6 Kg m3, galden ht230 has a molecular weight of about 1000, so ~26kg per m3
www.g-werner.at/de/downloads/solvay_solexis_galden.pdf

.

So what is an educated estimate of the m³ of vapour from 500ml of Galden?
Cause you can't see the stuff, how big might a suitable vessel need to be?

Or is this of little concern as it will be ALL temp controlled?

From the datasheet linked above:

The process is extremely fast and efficient since the
heat transfer coefficient of vapor condensation is
about ten times (10x) faster than hot air and about
eight times (8x) faster than infra red heat.

Doesn't that fascinate you, it does me.

[MK]

Air, density about 1.2 Kg m3, Argon about 1.6 Kg m3, galden ht230 has a molecular weight of about 1000, so ~26kg per m3
I think the argon will be superfluous.

What do you exactly mean, superfluous?  Google translation says "not necessary",  but the argon prevents the oxydation if you use simple hot air reflow and do not use galden. Yes if you use galden Argon is useless.

I assumed people wanted to use Argon and Galden, as argon by itself will not have enough thermal capacity/conductivity to do the job fast enough.

[MK]

For a hobbyist to buy and keep an Argon supply on hand will cost more than the litre of Galden.

Good to see that not everybody gets raped on industrial gas pricing like we do in NZ.
Bottle hireage ~$120/year
Re-fillable bottle purchase $500 up
2 m³ fill ~$80

Hence the reason behind my statement

Air, density about 1.2 Kg m3, Argon about 1.6 Kg m3, galden ht230 has a molecular weight of about 1000, so ~26kg per m3
www.g-werner.at/de/downloads/solvay_solexis_galden.pdf

.

So what is an educated estimate of the m³ of vapour from 500ml of Galden?
Cause you can't see the stuff, how big might a suitable vessel need to be?

Or is this of little concern as it will be ALL temp controlled?

From the datasheet linked above:

The process is extremely fast and efficient since the
heat transfer coefficient of vapor condensation is
about ten times (10x) faster than hot air and about
eight times (8x) faster than infra red heat.

Doesn't that fascinate you, it does me.

500 ml of galden at 230 centigrade will be about 33 litres or just a bit more, then you need to allow a reasonable volume on top to allow for the stirred layer not to lose any galden, as it costs quite a lot, down to your design skills to keep the galden where you need it.

MK
edited because I forgot to allow for the high specific gravity of galden.

[jwm_]

Just throwing it out there, but perhaps brake fluid will work?

dot 4 has a 230C melting point, but is made of glycols so is likely flammable however dot 5 is silicone based and has a vapor point of 260C. I have no idea what else is in there though so I wouldn't want to breath the vapors, but perhaps another generally available silicone will work? Take appropriate precautions if you try this of course.

    John

[mrpackethead]

As a starter for 10 points, I'm going to do my designed based on the following;

My tank size is going to be 400 x 300mm,  and i figure i want a vapour cloud of about 200mm thick.  Thats going to be 18l of vapour, which requires 272ml of fluid.    A heater 'well' will be big enough to have the heater and the fluid in.  I think i'll make that well big enough to house 500ml of fluid.     I want to have a pretty good "head room" for the cloud so, i think we'll build the sides up so they are 600mm tall.

I'll put thermocouples in

(a) the heating well
(b) a little above the liquid level for the well
(c) 100mm above the well.  This is where the board will sit, when it is lowered into the tank.
(d) 200mm above the well. This should represent where the vapour should 'reach'.   

Cooling system to be designed yet

[jeremy]

Hello everyone,

It seems everyone has gone quiet on this front. I just wanted to let anyone interested know that I am indeed crazy enough to keep trying with this.

The UPS guy showed up today with a neat 7kg package (please don't ask how much this cost ):




Note the warning about 300C, this stuff decomposes into hydrofluoric acid so great caution is needed with the heating.

I am having a container fabricated as we speak out of ASTM302 stainless steel, and the ASTM440 6.35mm stainless steel ball bearings for the induction heater are on the way. Unfortunately I had to get it made at a metal shop, as I do not have a TIG welder nor the skills to TIG weld. And the price of a good TIG welder pales in comparison to the price of galden.

I went stainless because I don't want to have to deal with oxidation at all. It was a little more expensive, but I am considering this an investment in my own learning, and I hope in the open source community. I've gained a lot from open source, and if this turns out ok then I will document the project and make it available online as my way of giving back.

I also have some 3mil/3mil breakout boards coming with a 0.5mm pitch BGA on them (atmega48) for testing. But they were slowed up by Chinese new year, so I don't have them yet.

As a very strange sidenote, the inside of the package smells like mint (including the paper documentation). I have no idea why.

In the meantime, I've been brainstorming some ideas for computer vision software for machine-assisted placement of fine-pitch BGAs. But now that the galden has arrived, I'm planning on doing some characterisation experiments with it, particularly with respect to the evaporation rate. I can't guarantee I'll be able to do anything else as my real work is about to crank up, but if anyone has any good ideas for some tests please let me know. Keep in mind that I'm an EE, not a chemist

My bank account hurts, but it's for science. 

[IconicPCB]

Nice one Jeremy.

I also have a container on the way and need to purchase some of the chemistry.

I dropped anote to solway enquiring where in this part  of the world I could get the fluid. So far silence.

[hkBattousai]

I have been searching "vapour phase soldering" in Google for more than an hour, but I still haven't found answer to one question:

At what step is the solder put onto the PCB?

I watched many Youtube videos (there wasn't any close up one). They put the PCB solderless PCB inside the hot cloud. And when they take it back, there are solders on the pads. Where did that solder come from? The boiling liquid doesn't contain any solder as far as I understood.

Can you please clarify this?

[MK]

I have been searching "vapour phase soldering" in Google for more than an hour, but I still haven't found answer to one question:

At what step is the solder put onto the PCB?

I watched many Youtube videos (there wasn't any close up one). They put the PCB solderless PCB inside the hot cloud. And when they take it back, there are solders on the pads. Where did that solder come from? The boiling liquid doesn't contain any solder as far as I understood.

Can you please clarify this?

They use solder paste, when it reaches the melting point the components stick with the surface tension of the solder.

[hkBattousai]

I have been searching "vapour phase soldering" in Google for more than an hour, but I still haven't found answer to one question:

At what step is the solder put onto the PCB?

I watched many Youtube videos (there wasn't any close up one). They put the PCB solderless PCB inside the hot cloud. And when they take it back, there are solders on the pads. Where did that solder come from? The boiling liquid doesn't contain any solder as far as I understood.

Can you please clarify this?

They use solder paste, when it reaches the melting point the components stick with the surface tension of the solder.

Thanks MK. I always though that "solder paste" is just another name for "flux". I made a quick research and learned about it.

[helius]

hkBattousai: the solder paste appears as a matte gray substance, but under high magnification it contains many small balls of solid solder in a flux gel. at the instant it reflows, it turns shiny and bright. Since it is sticky before reflow, it is used to stick components down to their pads before the board is moved to the reflow machine.

You can see the tiny solder balls melting together in this video:

Watch at 1:00 and 1:40

jeremy: the data sheet that comes with the HT230 in your picture shows a BP range of 222-237 C (10-90%). That seems to be quite close to a previous poster's figures for LS230:

Some more data, that i was able to obtain tells me that;

The Distillation spec range of the HT230. 
 10% >  210C,  90% < 250

Compared to the LS which is
 10% < 222,  90% < 235

Is there an error somewhere?
Edited: I see that the first figures are for the specific batch you received. So it looks like your batch is within the same range as the worst-case spec for LS230, implying it may work perfectly fine in machines designed for LS230.

[Chris Jones]

Hi all,

I've just started using an Asscon Quicky 300 (stop sniggering) vapour phase reflow soldering machine at work, with HT-230 Galden and lead-free solder paste. It worked pretty well on my first try though my stencil might be a little thick (thickest option from OSHstencils) - I got some solder bridging on a 0.5mm pitch LQFP so I needed to rework that with some solder braid, but very happy for a first try as it saved me about two days worth of hand soldering on that board.

I have the manual for the machine (on paper only at present), and I have recorded some temperature profiles at a couple of places in the chamber. It is an interesting machine. The top glass door has a seal around it which is pressed tightly by a clamp to stop vapour getting out - I had a thermocouple wire going over the seal and a bit of Galden leaked out there due to the wire preventing a good seal in that location. The board carrier stays put down near the bottom of the tank a few centimetres above the fluid surface, during the heating and cooling periods (~ 2.4kW flat heater plate UNDER the base of the tank). The tank holds 1kg of Galden. The vapour rises in the chamber and when it gets to the board, the board heats very rapidly. You can see the solder melt, then once the board reached the top temperature (229C) I gave it another 20 seconds and pressed the button to stop the cycle (trying not to cook the chips for too long) at which point it dumps cooling water through a stainless steel pipe that is immersed in the fluid tank at the bottom of the chamber, and now-hot water from this pipe drains out through a pipe from the bottom of the machine. The water-cooled stainless pipe quickly starts re-condensing the vapour and the board cools down fairly rapidly. When the board gets back down to about 150C you can wind the board up to the top of the chamber to dry off and cool a bit more. If you don't press the button to stop the cycle when the solder has melted, then the vapour keeps rising in the chamber until it gets to a temperature sensor about half-way up the front wall of the chamber which terminates the cycle. That would result in the board down the bottom of the tank being at 230C for about 3 minutes which was longer than necessary so I used the stop button instead of waiting for the vapour to reach the sensor.

If anyone wants more info on this machine let me know. I would like something like this for home too, though then I'd probably need to buy some Galden of one of you.