The printed circuit board with all its components is then placed in a reflow soldering oven. The reflow oven gradually heats the circuit following a precise temperature curve to assure a uniform fusion of the solder paste, avoiding thermal shocks and the resulting mechanical tensions in the components that one finds with hand-soldered assemblies.

The reflow oven is controlled by a prototype module of our own design. A thermocouple measures the temperature of the circuit being soldered, and optocouplers with zero-crossing detection allow the microprocessor to control the heating elements smoothly and without any of the emi fluctuations found with relay-controlled devices.

Prototype of a triac module with zero-crossing detecting optocoupler — this compact module can safely switch currents up to 40 amperes: