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Toaster Oven reflow

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DaveW:
I've been looking at soldering at BGA and some higher density QFN packages at home recently and I started looking at using a toaster oven for solder reflowing. I couldn't find the oven used in the sparkfun writeup in the UK
http://www.sparkfun.com/tutorials/60
so I found this instead
http://www.amazon.co.uk/Andrew-James-White-Litre-Grill/dp/B003SE88Z4/ref=sr_1_1?ie=UTF8&qid=1295006018&sr=1-1-spell
The internal space is nice and roomy for any PCB I do at home



I took the side off to get to the controls. Very simple and the temperature control could be off as it's outside the oven but all the easier to modify!
I simply changed the thermostat out for an SSR-didn't even need to cut any wires!



A 3mm hole to get a thermocouple though and the modding is almost done



It does heat up quickly enough, 15-100 deg. C in 110 seconds, 15-200 deg. C in 246 seconds. I'll put a higher temperature thermocouple in there and get it under PID control with a PIC. Looks like a quick simple way to get into reflow soldering, judging by what other people have done should be easily capable to doing BGA packages which I've had to leave before,

apex:
Hey, cool!
apex

tyblu:
Very cool -- will enjoy doing this myself in the future. Is it pretty even heat, or is there a convection fan inside? (Does it matter?)

Time:
hell, I have just done it on an unmodded toaster oven, thermo couple/meter lots with no problems

Chasm:
The problems with such a conversion are usually the temperature probe and the distribution of the heat within the heater - and of course that you are playing with the mains.

The temperature probe problem can be solved by using something designed for this task, usually a thermocouple. But those are not necessarily cheap, and have some pitfalls. (You have to keep the other end of it at a constant temperature or know the current temperature to compensate for it.) OTOH cheap part bin solutions like a diode are not too stable and introduce nonlinearity problems.

Distribution of heat should be even. you don't want to burn one part of a board while another is not even melting. It can be improved with a fan -which of course has it's own pitfalls- or by using a oven that has top and bottom heating elements and thus heats up more evenly.

And then there is this mains thing... Let's say it this way:
Mains can kill you. Mains can burn down the house. Mains can kill your significant other.
And usually most important: Insurance companies have the habit of not paying at all when tampered with gadgets are involved.

So better know what you are doing before tampering with it.

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