Electronics > Projects, Designs, and Technical Stuff

Toaster Oven reflow

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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
so I found this instead
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,

Hey, cool!

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?)

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

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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