Following the component placement, the assembled PCB goes through the soldering oven Kurtz Ersa Hotflow 4/20, where the high temperature gradually melts the paste and attaches the components to the board. These are long convection ovens with a process length of more than 6 metres separated into 10 heating zones and cooling zones. Preheat, thermal soak, reflow, and cooling are the four stages into which the zones are split.
Solder profiles can be optimised for each particular assembly job based on the component size and layout, layer counts on the PCB, and copper distribution on the board. The oven's heating zones are each set at a controlled temperature that corresponds to the solder profiles needed for assembly.
After heating the component and its attachment to the board, follows the cooling process. The solder paste will harden as soon as the temperature decreases significantly, and the components are then attached onto the circuit board. In the final areas of the reflow oven, where the processed board is cooling, the solder alloy solidifies and forms the solder joints.
After reflow soldering the PCB board goes to the loader, which performs two functions. It can act as a buffer for the boards that are waiting for checking or it can be used to cool down the board after reflow soldering.