Re: desktop ovens

by adafruit on Mon Oct 11, 2010 12:11 am

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Re: desktop ovens

by charliex on Mon Oct 11, 2010 1:37 am

ok good, thats the one i choose too, since its got that cool yellow/orange glow.

cheers :)
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Re: desktop ovens

by mikeselectricstuff on Mon Oct 11, 2010 6:47 pm

I wonder if the orange/yellow glow (assuming it's the actual heater and not window-dressing ) is a good idea.
if a large proportion of the heating is via IR rather than air convection, then there might be issues with dark coloured parts absorbing significantly more heat than more reflective ones, exceeding their temperature limit before the rest of the PCB has reached soldering temperatures.
It might also create issues with parts heating up faster than the PCB, especially when there are large copper areas, leading to tombstoning etc.
This is guesswork and I've not done any testing on this, however I do know that industrial reflow ovens don't generally use direct IR heating (or at least not entirely) and there must be a good reason for this, as IR would probably be faster and easier to control.

I tend to run my toaster oven with the elements only just glowing (230V oven at about 150V via a variac) for preheat, then up to dull red for reflow.
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Re: desktop ovens

by ohararp on Fri Oct 22, 2010 12:27 pm

adafruit, just to confirm are you doing your production reflow using the black and decker infrawave?
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Re: desktop ovens

by adafruit on Fri Oct 22, 2010 12:36 pm

yes thats what we said
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Re: desktop ovens

by ohararp on Sun Oct 24, 2010 11:29 am

Freaklabs, any chance you could post a picture of the bottom of the aluminum plate of your hot plate? I am working on a diy hot plate now and am using a simple ring heater and ssr to control the heater. I am finding the hot plate is very easy to control with the larger thermal mass of the hot plate.

Here are 2 good links on this as well:
http://wiki.picbasic.org/index.php?n=Projects.EasyHotPlate
http://wiki.picbasic.org/index.php?n=Projects.SimpleTCTemperatureControl
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Re: desktop ovens

by blipton on Mon Nov 29, 2010 6:37 pm

So in general would it be safe to say, that

Skillets / Hot Plates are best for single sided boards only.. although the surface temperature is uneven..
(ex. http://mightyohm.com/blog/2009/01/diy-p ... -hotplate/
http://www.ntscope.com/Merchant2/mercha ... Code=QK870
http://www.sparkfun.com/tutorials/59 )

Ovens should only be used for 2 sided boards since the the ic components get baked hotter than on a skillet
(BLACK & DECKER, Infrawave Infrared Toaster Oven
http://www.sparkfun.com/tutorials/60
)

Regardless, however, is a closed loop temperature control mandatory? How important is to not just throw the board on/in, but rather have a temperature pid controlling it (Omega CN77000, techFX reflow 3.0, anlagelab pcb, etc)?

What gear is the safest approach?
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Re: desktop ovens

by mikeselectricstuff on Tue Nov 30, 2010 8:41 am

Closed-loop control is by no means essential - it just means you can press 'go' and leave it to get on with it while you go do something else.
As long as your toaster has a decent window you can do it by eye, preferably with a temperature probe, but once you get used to the oven even that isn't too necessary.
I would recommend a simple timer or alarm function on your watch to alert you to when reflow is likely to start (based on previous experience), as reflow times are on the the sort of scale that it's easily to get distracted while waiting for it to get up to temp, then you notice a smell of burning board...
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Re: desktop ovens

by blipton on Sat Dec 04, 2010 11:34 pm

So either a B&D Oven for $150 + a Controller $150,
http://www.reflow-kit.com/rkuk/order_pr ... 634dad52ac

or a Madell QK870ESD Skillet with Built-in Controller $400
http://madelltech.com/m3-12.html

pricing seems very close (~$350)...

But ran across this, which makes it seem like it's possible to do it much cheaper using the "Cash Olsen" method:
http://www.kd5ssj.com/index.php?Itemid= ... ew=article
http://www.youtube.com/watch?v=Mty1kfwXcm4 http://www.youtube.com/watch?v=F0OKuxPiGKs

Can as-good results be achieved using the inexpensive tools?
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Re: desktop ovens

by mikeselectricstuff on Mon Jul 18, 2011 4:44 pm

The main difference between a toaster oven and a proper reflow oven is the level of automation. If you want to put a board in, press a button and come back later, you need a proper controlled oven.
If however you're happy to sit and watch it after the first couple of mins, then a toaster is fine.
If you really want to use lead-free, be aware that there is a much lower margin between 'reflow' and 'meltdown', and a toaster can be more problematic - evwn with professional ovens, they sometimes use nitrogen to reduce oxidisation, but the easiest answer to that is to just avoid leadfree.
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