Just thought I’d chime in here as I have massive experience in SMT reflow methods (in a professional capacity)…
First off, DO NOT buy a cheap reflow oven from China or anywhere else: They are total garbage, and by that I mean they do not work at all. I had the unfortunate pleasure of trying to setup one for a client and it ended up in the dumpster, literally, I thew it there myself. It was $3,500.
SMT reflow with a normal, decent quality, toaster oven is super easy and doesn’t require a controller. I’ve reflowed hundreds of boards this way, with both leaded and lead-free paste. Large BGA’s are pretty tricky due to shadowing, but everything else works fine. The low temp Bismuth paste is crazy easy (can use a hair dryer…lol).
The trick is just profiling the oven. Usually I do 5 minutes of preheat at ~250F then crank to max for 2-3 min. The last bit is more critical but you can just watch it. Once you see the solder start to melt, count down 30 more seconds then turn it off. Simple as that. Let it cool down a bit before the next board. The two step, preheat then max is critical and the ‘secret’ to making this work.
The reason this works is because these little ovens don’t have much power. Their natural ramp up curve it pretty close to ideal. I’ve verified this on a few different models with profiling probes. For DIY work its great. There is no way a controller will improve it.
IMHO, the controllers are a total waste of money, for two reasons: First, it’s not needed. Second, there is just no way a temp control like this actually works. The temperature of the PCB and parts is very unrelated to air temperature, especially in something with such low thermal mass and power. Real IR/Convection reflow ovens DO NOT work like this at all. Real reflow ovens (that work), even the tiny ‘prototyping’ ones are 8kw or more. This kind of control is total nonsense.
Next time I’m in Vancouver I can do a demo. I also have a nice higher end toaster oven I can donate that I used to use for this. I now use a $35,000 VPS oven.
Please feel free to hit me up for any other info/advice re SMT. Most things are easy but the techniques are specialized and not always obvious.