The process of reflow soldering involves attaching components to metal pads on a circuit board with solder paste, and then subjecting the entire unit to heat. When uniform heat is applied to the components and circuit board, the temporary connections can become permanent solder bonds. Reflow soldering may be used with traditional through-hole technology, though it is the main method for connecting surface mount devices (SMDs). The purpose of the reflow soldering process is to submit the circuit board and components to a uniform level of heat that will melt the solder paste without damaging any of the electronics. Reflow soldering typically includes four distinct stages, each of which involves a different level of heat.
Traditional soldering typically involves through-hole technology, where component leads are passed through a circuit board and then heated individually as solder is applied. This type of soldering can be time consuming, and applying excessive heat to an individual component may be damaging. It is also difficult or impossible to use traditional methods with surface mount technology (SMT), where each component sits on top of the circuit board.
