If you want to solder SMT components professionally, you should use reflow oven. OF course, no one suggests using specialized oven which is really pricy and used in PCB houses where tons of boards are soldered. With a little bit of effort you can build pretty good oven that can solder small PCB batches. Zaggo simply purchased a toaster oven for about 40€. He also wanted to keep warranty, so he started building external controller that doesn’t mess with internals.
Oven controller is based on Attiny45 microcontroller that comes with 4K of flash. He was able to squeeze in full PID algorithm along with minimal user interface. Temperature is measured by using 100k thermistor and oven is controlled with simple mechanical relay via transistor. Single push button is used to start program. Its performance is indicated with single LED. The circuit turned out to be very compact and easy to build with through hole components. Practically any simple oven can be turned in to reflow station without loosing warranty. Source code and other files can be downloaded from GitHub.