It uses two resistive heaters in serie. The temp is controlled by a PID controller. On top you see a fan. This cools the oven if needed so I can cool it faster. It scuckes cool air in through holes in the bottom, via the room between inner and outer cabinet to the top.
I mounted an extra K-type thermocouple. This hangs in the oven in such a way that I can position it on the part.
It can be used for reflow or reballing. But for me more important, testing the tempco of components. I mounted a big fuse on the front. The oven heats up fast enough for reflow. It has no profiles. I do that with a stopwatch. I know the curve of time against temp. The controller is easy en fast to set so I ramp it up in several steps. A bit more work but for me good enough. I mounted a switch that cuts of the heaters while the temp reading stays powered. The oven has no problem to get above 220 degrees.
I mounted a piece PCB material as a heath-shield. The PID controls a solid state relais. The big grey thing in the middle.
As a test I reballed a small BGA from a junkbox pcb. That is a not as difficult as I was thinking. I used a microscope and a pincet to place the balls in sticky flux-gel. That was a few minutes work.
To protect the pcb and other parts I used aluminum tape and kapton tape.
Then a few minutes in the oven.