Professional Grade Reflow Ovens

[mikeselectricstuff]

What about ATTEN ovens?



http://www.batronix.com/shop/soldering/ovens.html

No window = instant fail

[mcinque]

hmm... Mike, why you get instant fail without a window? Mybe because you can't see what's happening inside and so modify time/temp according to custom settings?

[Sebastian]

We have a vapor phase reflow oven at school. They are ideal for prototyping because they heat up quickly but I have no idea what company it is from and how much it costs.
Maybe you can find a used one on ebay.

[Precipice]

Maybe you can find a used one on ebay.

I wish...
About £15000 seems to be the entry level. It's not the heating up quickly that's the reason they're great (in fact, manufacturers go to great lengths to slow down the heating up), it's that it's impossible to overheat components - the temperature you get to is the boiling point of the fluid, and no higher. You also exclude oxygen from the soldering process, so you get nice clean joints, even with lead free solder.
I've been buying the fluid, and playing with modified deep fat fryers. Results have been excellent, so I need to build a less manual, and slightly bigger, unit.

[Carrington]

I've been buying the fluid, and playing with modified deep fat fryers. Results have been excellent, so I need to build a less manual, and slightly bigger, unit.

You can upload images?

The advantages of the vapor phase soldering:

  - Any danger of overheating.
  - 10x faster than hot air and 8x faster than IR heating (independent of component density, size, shape, or surface area).
  - No temperature differential.
  - Defect-free results on densely-packed, high-component-mix assemblies containing complex BGAs, CSPs, and other advanced devices.
  - Soldering takes place at only 5°C to 10°C over the melting point of the solder paste.
  - Eliminate component stress and delamination of components and substrates.
  - Different PCB assemblies can often be processed in the same batch without having to adjust the temperature profile .
  - No need for a nitrogen atmosphere, as the vapor itself and the entire atmosphere in the chamber are chemically inert (prevents oxidation).
  - Soldering fluids are chemically and thermally stable, non-toxic, free of CFCs, and environmentally-safe.
  - Lead-free and tin/lead solders can easily be processed in the same system by simply changing the vapor phase fluid.

[free_electron]

Now there is an idea for a kickstarter ! A hobby vapor phase oven...

For the uninitiated :

Vapor phase soldering is THE rolls royce of processes.
-you can't fuck it up
-success guaranteed
-perfect solder joints each and every time
-no risk of crisping boards or parts.
-clean
-environmentally friendly

It has one drawback. The liquid needed might as well be mouse milk ... At almost 1000$ a gallon...
Fortunately, if the oven is well built the liquid is reused over and over with very minimal wasting.

The trick is the liquid. A fluorinert material, essentially liquid teflon, is being heated in a deep tub, like a deep fryer.
The liquid boils at a specific temperature and creates a cloud of vapor. Galden (which is one brand name of this liquid , made by dupont i believe ) is availble in several boiling points. One of em is 220 degree c. Another is 270 degree c. It goes in steps of 5 degrees..

Galden is completely inert. You can drink the stuff, it goes straight through you. The molecule is inert.
Even in vapor form it is inert.

Now, how does the magic work ?
You lower a pcb, pri ted with solder paste and populated with parts i to the cloud of vapor. Vaporised galden is denser than air. It doesn't rise. It forms a blanket. Kinda like throwing dry ice in water.
The hot galden vapor will transfer its heat to the cold pcb , thus heating it up. In exchange the galden re liquified, and drips off the pcb back in the tub where it is reheated.
This process goes on until the pcb and all components sit at exactly the same temperature of that cloud (which , if you picked the galden 220, is exactly 220 degrees c ). Since solder melts at 183 (snpb) the entire board reflows at thr same temperature.
No gradients, no warpage, no hotspots , nothing. Perfect reflow !

You can visually see when this point has been reached. As long as the board is colder than the vapor cloud, beads of liquid galden will form and drip off. Once at temperature this beading stops and the board goes dry.
A nice side effectis that the galden also dissolves any residual flux ...
So the boards come out squeaky clean as well !

Simply raise the board out of the cloud, wait a few seconds to let it cool so the solder can solidify and bob and annie are you aunt and uncle.

The real ovens use a lid and have a condenser ring installed. So no vapor can escape. There is a cold zone about 20 centimeter above the vapor cloud.

Galden can be purified to remove the flux contaminants. The only waste is in escaping vapor.

Another side effect is that solder joints are essentially done under an oxygen free atmosphere. So the flux can do its work and the wetting happens under a blanket of galden vapor as opposed to air which oxidises the solder and the pads, reducing wettability that the flux tried to create.

[free_electron]

Vapor phase soldering has been around for a very long time , like the 50's but always had the problem that the chemical used was extremely toxic. Not only that, the blanket disllaces oxygen and , if done in a badly ventilated room could asphyxiate people. The liquid has no smell  or color, so you don't see it or notice it You simply go unconscious. Pretty much like co poisoning...

That changed 15 to 20 years ago when that galden stuff became readily available. The toxic problem went away. The potential blanketing problem is still there. Vapor phase machines need to run in well ventialetd rooms just in case tha vapor escapes.

If you use a deep tub , only put in a few cups of liquid and use a thermo co troller that is set for a few d egrees over the vapor point there iss virtually no risk.

Add a condenser coil at the top

All that is needed is essentially a deep fryer and a condenser coil. You can feed that one from a refrigerator motor ... In the condenser coil you can also run galden liquid, just pick one like at 100 degrees c.  The vapor will not pass the cold zone (well, cold .. 100 degree zone, you don't want to thermally shock the boards cooling down ) and the board cools gradually.

Why is this not used in the industry ?
It is a batch process. Not a flow through process.. Board goes in, board comes out , then next board goes in. Not like a huge reflow oven that is a chain or belt driven machine that cranks out boards.
So the throughput is low.

And that galden stuff is bloody expensive...

[free_electron]

http://www.coultersmithing.com/OldStuff/CLAB/coffee_can_reflow.htm

This guy does it in a coffee can. I like the deep fryer approach better.

http://www.wenesco.com/vapor.htm?gclid=CIeT0-KJk8ACFcI7MgodhkkApA

http://www.ebay.com/itm/CENTECH-Vapor-Phase-VP-1000-HIGH-TEMPERATURE-SOLDERING-SYSTEM-/351138971819?pt=LH_DefaultDomain_0&hash=item51c18380ab

I did a quick look on ebay for the liquid, but none of em available there are suitable. The boiling point is too low. 157 degree was the highest. You need fc-70. That boils at 215 degree c which is perfect .

[Precipice]

Mu current thought is :
Deep fat fryer (preferably, like the cheap Aldi ones I got, with a heating element outside the pan, so nowhere for fluid to hide or overheat.)
Basket arrangement to hold the PCB at a useful height
Pyramidal aluminium hat, quite tall. This has:
  riveted-on L-section extrusion, running vertically, to act as a heatsink. As many sections as will fit.
  A vigorous PC fan at the top, blowing air down all 4 sides of the pyramid, and over all these heatsink strakes.
  A USB camera, an illumination LED and a (say) 16x4 PIR widget (The Melexis one goes hot enough) all at the top. It shouldn't get hot up there.
The hat needs to drip the fluid back into the fryer, and avoid it escaping, since it's expensive, and gets absolutely everywhere! (Lesson learned from simply using the fryer unhacked).

Making it all rectangular should make fabrication easy, but round would also do - I'm wondering whether I should get one of those
http://search.ebay.co.uk/171229554056 - easy enough to wrap cooling coils round the top section, and heating it with an induction hob should avoid messing around with strapping resistors together.

What I'd really like is some heatproof material that floats on galden vapour, so I could easily measure (and control) the vapour level. Hints would be very welcome!

Another thought I have from time to time - vapour phase is all very spiffy, but for prototype purposes, where you don't need to do boards back to back very often - can you just dunk boards in a bucket of the stuff, and heat it up? Or do the components float off in a comedy manner?

[free_electron]

It would wash away the solder paste. That stuff is thinner than water ....

You dont really need a condensing hat.  Fluorinert vapor is denser than air. It sinks... So it forms a blanket.

Simply get a deep fryer with a digital temperature control. Set to a few degrees above fluorinert boiling point.

I am tempted to experiment with this. Just need to find a nice deep (deep bucket) fryer.

http://www.ebay.com/itm/Home-Double-Deep-Fryer-4-Qt-Electric-Stainless-Steel-Kitchen-1700w-3-Baskets-/380851065216?pt=Small_Kitchen_Appliances_US&hash=item58ac7e1180

Or

http://www.ebay.com/itm/Deep-Fryer-Stainless-Steel-Dual-Electric-Presto-Basket-Countertop-Commercial-4-/111435097772?pt=Small_Kitchen_Appliances_US&hash=item19f20ca6ac

[Precipice]

Unfortunately, you do need a cooling hat (or a really, really deep container). Vapour just flopped everywhere, and there was a slick of the stuff over the kitchen... If I do it again, I'll take video.
I was hoping the vapour would just sit in a blanket, but it seems not.

[Kjelt]

Question, how does lowering a pcb into vapor of 220 degrees C guarantee to follow the required reflow process like holding the temp at 160 degrees for 30+ seconds to wet the flux in the paste? Or do you also need special solderpaste for ths process?

[Precipice]

It doesn't - some VP ovens seem to have some convection preheating going on.
I want to just modulate the power going into the bath, and watch the board temperature with the 16x4 PIR in the top of the hat. That should be closed loop enough to avoid any disasters.

If you don't bake your part before assembly, dunking them in a bath of hot vapour strikes me as a good way to induce popcorning as the trapped water boils.

[Carrington]

Now there is an idea for a kickstarter ! A hobby vapor phase oven...

It's a good idea.   

Probably many people already tried to build one. Sometimes it is faster to perform an intense search through the network.

After a quick search I found this:
http://www.arxterra.com/news-and-events/members/vapor-phase-soldering/

Also, on this web many concepts relating to the reflow soldering are explained (and many other things).
http://www.ami.ac.uk/courses/topics/0132_rs/

[Precipice]

After a quick search I found this:
http://www.arxterra.com/news-and-events/members/vapor-phase-soldering/

What the hell? They're pouring a watering can of water into their hot galden? I don't understand.

[Carrington]

No idea! But maybe you are referring to this:

The heaters powered up fine and was used to heat up some water while we were also testing for leaks in the tank and the seals around the heating element through-wall penetrations. The heater drew 10.5 amps while energized and successfully heated up the water to a slow boil.

Maybe they are doing some test, at the end water will evaporate.

[Precipice]

Nope - they pour in the Galden, then, a few minutes later, they pour in a can of water.
It seems they're trying to have a blanket of water vapour over the galden vapour, and a blanket of water over the galden. This seems, err, unconventional.

[Carrington]

Ok, I get it, but don't know why they do that.
They have a video where they show this?

[Kjelt]

How much of that Galden LS230 stuff do you need for a decent process?
It is for sale in Germany for €41 per 100ml
http://www.electronic-thingks.de/attachments/069_Electronic-Thingks-Pricelist-2014-03-13_en.pdf

[free_electron]

not a lot. probably 200 to 300 milliliter should work.
looks like that stuff has come down a lot in price... then again the one i used was Galden HT210 used in the cooling system of an ion implanter.

in the ovens they use HS or LS which seems to be a lot cheaper. 85$ a pound. so 160$ per kilo. Still a gallon sets you back a big swath of cash ... and that stuff is heavy ..

it's still at 1550$ per 5kg ( which is about a gallon for that material )
http://www.oritech.com.au/search.aspx

[Kjelt]

Nope - they pour in the Galden, then, a few minutes later, they pour in a can of water.
It seems they're trying to have a blanket of water vapour over the galden vapour, and a blanket of water over the galden. This seems, err, unconventional.

Looks like it was a test to see if it was the Galden vapour escaping or the water vapour. Why they put in water in the first place is beyond me. 'Reading the text they didn't have their temperature measurements in place, they did not know the temperature of the fluid.

[Carrington]

In the long term, it is cheaper than the nitrogen. A refill of 7 liter of nitrogen costs 35 Euros.
Although if the gas is contained throughout the entire process, it would be cheaper.
But this is not the case for this type of rework stations:
http://www.bokar.com/index,29,FOCUS-Series-Hot-Air-Nitrogen-Systems.html
But I suppose that is the best option to rework a single component...

[Carrington]

No window = instant fail

Returning to conventional ovens, I also prefer a large window, like this:
http://www.manncorp.com/smt/prod-325/reflow-ovens-bench-top-850.html

[mikeselectricstuff]

I've been buying the fluid,

Where from, and how much?
When I looked a while ago I couldn't find any sources in small quantities
The key to doing this small-scale is getting a setup that needs the minimum amount of fluid (regardless of PCB size!) and doesn't lose much.

[Precipice]

On ebay, been paying up to £300 for a 5Kg bottle, rather less for smaller bottles.
You need so little, though, that the cost of the fluid shouldn't be a showstopper (although you would miss the feeling of 'how heavy???' when you pick up a big pot of it).