o Reflow soldering, a machine soldering process, is the preferred technique for surface mount circuit boards. Reflow requires that solder is applied at the start of the process, generally by stencil printing solder paste onto required areas of the board. Automated pick-and-place machines then place the components directly onto the solder paste, which retains them in position temporarily. The board then passes through a reflow oven where the solder paste melts to form the permanent joint.