Works well on components with leads or wires that have to be mounted on the PCB by plugging them through the holes drilled on the PCB. The extra lead part has to be soldered on the other side of the board. This technology is applied on PCB assemblies containing large components such as resistors, capacitors, coils, switches etc.

Surface mount technology is used for small & miniature components/ICs with small footprints which allow for a larger density of components on the PCB. In this method the components are mounted directly onto the surface of the PCBs. Sensitive components, some very small, such as resistors or diodes are placed manually or by automated pick & place equipment onto the surface of board.

This is called SMD assembly, for Surface Mount Device. Surface mount technology can be applied on small size components and integrated circuits (ICs).

Some PCBs are designed to have both through hole components & SMDs on the same circuit board. Through hole components are still typically used in boards with high power handling requirements. These boards with both SMDs & Thru-hole components are referred to as Mixed component boards & use Mixed Technology for the components’ assembly.