Surface-mount technology (SMT) is a PCB method for producing electronic circuits in which the components are mounted or placed directly onto the surface of printed circuit boards (PCBs). Surface-mount technology was developed in the 1960s and became widely used in the late 1980s. Much of the PCB pioneering work in this technology was by IBM.
The design approach first demonstrated by IBM in 1960 in a small-scale computer was later applied in the Launch Vehicle Digital Computer used in the Instrument Unit that guided all Saturn IB and Saturn V vehicles.[2] Components were PCB mechanically redesigned to have small metal tabs or end caps that could be directly soldered to the surface of the PCB.
Components became much smaller and component placement on both sides of a board became far more common with surface mounting than through-hole mounting, allowing much higher circuit densities. SMDs can be one-quarter to one-tenth the size and weight, and one-half to one-quarter the cost of equivalent through-hole parts.An electronic PCB device so made is called a surface-mount device (SMD). In the industry it has largely PCB replaced the through-hole technology construction method of fitting components PCB with wire leads into holes in the circuit board. Both technologies can be used PCB on the same board for components not suited to surface PCB mounting such as large transformers and heat-sinked power semiconductors.
