Accidently my vapour oven?

[law]

Having a good day today.
I am reworking some boards that did not reflow initially - I had trouble with my paste.

I took some advice and got some liquid flux to put onto the boards, then put them through the oven again for another reflow.
This was going well, until I mixed up my flux bottle with my machine oil bottle. It seems that, clever me, I used the same type of dispensing bottle for the machine oil as I did with the flux.
I wrote in sharpy on the bottle what it was, but that of course, rubbed off.
I've been doing some feeder maintenance, and just put the wrong bottle in the wrong place.

Being my first time with liquid flux (am used to gel flux), I thought the flux had just become more viscous after have been out for a few hours. I ran some boards through the machine.
The smell let me know that something was wrong, I pulled the boards out of the oven. They look ok, but have residue on them. I assume they did not reflow properly and I will get rid of them.

My problem is - have I nuked the nice new Galden that I just put in the machine a couple of weeks ago? I sure hope not.

There is still a bit of a lingering smell, and I would like to keep using my oven...

Any thoughts?

[tooki]

I think you missed a word in your thread title? Might wanna edit that.

[Whales]

First of what: what model of machine oil?  Have you checked the SDS?  If you share it here I can take a quick look and see if there is anything obvious to be worried about.

If it's just a mineral oil then you're probably good.  If it has teflon/PTFE/similar in it then I'd consider treating the oven (and board) as toxic waste, the burned remains of fluorinated compounds are really hazardous and horrible.  (EDIT: I'm probably worrying too much, vapour change ovens are already temperature limited and use fluorinated fluids anyway).  Don't try and clean it yourself without getting advice first, and if you have already started then stop until you can make sure.

Technically the oil could have worked as a mild flux   All it needs is to be a reducing agent that burns near soldering temp.  But yeah cleaning the residue might be a PITA. 

[law]

Hey,
Thanks for your reply.

Good call on checking the SDS. The oil was plain old Singer Oil:
https://singerco.com.au/singer-oil-100ml/1l/5l-/

It looks like it is a mineral oil, so that is some good news I suppose.

[Whales]

Good to hear   Technically its burnt products are still toxic & carcinogenic, but of a similar calibre to actual flux.  If it was heated without easy access to oxygen (due to the vapour) then it might have mainly polymerised rather than burning, creating a sticky varnish like layer.

(On some further thought: PTFE might not be as much of a risk as I had thought due to the intrinsic temperature-limiting nature of vapour ovens.  Eg 230degC shouldn't cause notable decomposition for most PTFE.  But don't quote me on that, perhaps it still bakes hotter if it reaches a heating element after dissolving.)

I don't have experience with vapor phase change ovens, apologies.  For questions like "will the oil have dissolved into my fluid", "will it bake onto the elements heating the fluid" and "will it contaminate my other boards" you'll need to seek the advice of other forum members here or your fluid supplier. 

[Whales]

I don't know about Galden, but Krytox (another vapour phase change soldering PFPE) claims that most things are insoluble.  See https://www.krytox.com/en/-/media/files/krytox/krytox-chemical-stability.pdf  (Interestingly though it seems fluorinated lubricants do get dissolved!)

Perhaps the oil didn't dissolve in, but just partially vaporised and maybe coated some of the lid, panels and parts near the PCBs inside your oven?  Doe anything look dirty or like they might have a thin glaze/varnish on them?

Hoping someone with experience can jump in here 

[law]

> Doe anything look dirty or like they might have a thin glaze/varnish on them?
I did wipe the glass lid on the inside and got some brown residue on the wipe. It's difficult to say if it is flux residue or oil.

I just took a photo of the crime scene.
The brown ripply bits across the bottom I think are flux. I had to clean the machine when I got it, and the chamber had similar rippled looking brown on the bottom,
However I note that there is black charred residue around the edge of the liquid/wall interface. The white-ish lines on top looks like oil sitting on the surface of the liquid.

I think it will be getting drained and another clean...

Thanks again

[law]

Some good news,

I just talked with the oven manufacturer and local distributor and both recommended draining the Galden, cleaning the machine and replacing the filters, then filtering the Galden and just putting it back in.
Apparently you just use coffee filters to filter the Galden. I asked the manufacturer if filtering would be enough to remove the oil and they said just filter it again!

[law]

Hey all,

I've since cleaned my oven and it is smelling much better.
I drained and filtered the Galden twice, but it still has a reasonably strong burnt oil smell to it.
I'm probably going to fill the machine with fresh Galden and deal with the old stuff later.

I am looking for some opinions on whether its worth attempting a rescue on some of the boards that went through.
I've included a couple of pictures, one you can see is covered in residue and the other is a good board that was made prior to the incident.
The one covered in residue has not been cleaned.
Each board has about $40AUD in parts on it and 12 went through the oven.
I suspect if I was to attempt a rescue, I'd have to clean the boards, flux them, then put them back through the oven.
That would make 4 times through the oven: double sided load - parts install means twice through the oven,  then once for an attempted rework, then a fourth time for an attempted rework again.
I'm not sure that they would be happy boards after such a bad time.
Does anyone care to weigh in?

Thanks again

[Whales]

Your "good" and "bad" images -- is the only difference the presence of the oil, or have you washed the good one more as well?  I can't much flux residue on the good image.

I would suspect that the solder joints in the oily one are fine and don't need a reflow.  Removing the polymerised oil tar would still be a good idea though (it could go acidic over time).  Getting it out from underneath the chips might be fiddly if it's hard to dissolve.

Is it the old galden that smells like burnt oil or the machine itself after you empty it?  Putting a whole fresh batch in might be a mistake if it's partially soluble and stuck inside the machine (you would be better off washing the inside out first).

[law]

Hey,

The "good" image has not been washed at all. I use no-clean flux. It is a bit hard to see, but I can see it in between the pads of the unpopulated parts and around the INA240 down the bottom.
The oil residue is the only real visible difference. What I am not sure about is the quality of the solder joints, or any damage to the board (in any way) in the presence of the oil.
I was thinking of dunking all the boards into some PCB cleaner I have (Chemtools Kleanium) and giving them a blast in the ultrasonic.
I might try and clean the boards, but just use them for in house testing and demos.

It is the old Galden that still has the burnt oil smell.
I drained the Galden from the machine and filtered it twice (through coffee filters, at the manufacturers recommendation).
I actually asked them to confirm that a simple filter through the coffee paper would be sufficient, and they said "If filtering once isn't enough, then just filter again. It should be enough."
I might drop them another email..
I was actually pretty surprised that there was still a smell. Before I drained it I'm pretty sure I could see that there was oil floating on top of the Galden.
It drains via a hole in the bottom of the process chamber, which has a weld bead around it. So not all the Galden drains out - you might be left with 1mm in the bottom.
I thought that the oil would still be floating on top of the remaining Galden, which I mopped up with cloths and disposed of, but the smell still remains!

As for the machine, after I drained the Galden I cleaned the machine out pretty thoroughly with the recommended oven cleaner. I left it over night with the lid open a bit to air out, then did the same thing the next day - another clean with the cleaner and lid open over night.
There is a hint of the smell still in the machine, but the Galden is definitely worse.

Thanks again

[Whales]

Coffee filters only help if it's insoluble solids.  The molecules you are smelling might be an insoluble liquid (like the oil-on-top you noted) or soluble aromatic compounds (distillation might be the best way to try and remove these).

Perhaps try putting a blank PCB with paste on it through the cycle and see if it ends up with an oily residue or not.  You might have already removed the bulk of the problem and are simple left with a small amount of burnt aromatics.

RE your photors: It's very interesting that most of the oily residue is in places near pads.  I wonder if this was driven by thermal causes (galden condensing more readily on the metal parts?) or if the oil and flux combined in a chemical reaction to make the sticky tar.

[law]

>Perhaps try putting a blank PCB with paste on it through the cycle and see if it ends up with an oily residue or not.  You might have already removed the bulk of the problem and are simple left with a small amount of burnt aromatics.
I've replaced the couple of filters in the machine (internal circulation fan and exhaust to outside world), so I'm aiming to fill it and give it a run this morning.
I'm thinking you are correct with the small amounts of burnt aromatics. I ended up contacting Asscon again and they suggested that the smell should go away with time.

I'll let you know how I get on. Thanks again.

[law]

I refilled the machine with the last of the fresh Galden I had (just enough!) on the 30th and ran a bunch of test boards through it.
It is working very well again. There is still a bit of a residual smell, but the boards are coming out perfectly.
I'm off to label my bottles of stuff better.

Thanks for your help and suggestions.

PS - I actually cleaned the oven four times before I put fresh Galden back in it. Pretty sick of cleaning it to be honest....

[uer166]

What's that BLDC all in one drive chip? Looks neat

[law]

Hey, its a TI DRV8312.
The PWM interface is a bit weird, but it works pretty well.