ReflowLöten

Reflow soldering, also known as reflow Löten in German, is a process used to solder surface-mount components onto a printed circuit board (PCB). It involves applying a solder paste to the pads of the PCB, placing the components onto the paste, and then heating the entire assembly in a reflow oven. The heat causes the solder paste to melt and then solidify, forming electrical connections between the component leads and the PCB pads.

The process typically begins with the application of solder paste, which is a mixture of solder powder and flux. This paste is precisely dispensed onto the designated areas of the PCB using a stencil or automated dispenser. Once the paste is in place, the surface-mount components are picked and placed onto the sticky solder paste. Following this placement, the populated PCB is passed through a reflow oven.

Reflow ovens are designed with multiple heating zones that gradually increase the temperature. This controlled heating profile is crucial for a successful reflow process. Initially, the oven gently heats the board to evaporate the solvent in the solder paste. Then, it reaches the activation temperature of the flux, which cleans the surfaces to be soldered. Finally, the temperature peaks above the melting point of the solder alloy, allowing it to flow and form fillets. As the board exits the oven and cools, the solder solidifies, creating robust joints. Different solder alloys have varying melting points, and the reflow profile must be tailored accordingly to avoid damaging the components or the PCB.