Abbreviated as SMT, surface-mount technology is a design standard for constructing electronic circuits where the components are mounted directly onto the the surface of the printed circuit board (PCB). The components have small metal tabs (or caps) that are soldered directly to the surface of the printed circuit board on tin-lead, silver, or gold plated copper pads, called solder pads.
SMT is mostly done using surface mount soldering equipment even though hand soldering is also done occasionally. Most manufacturing units using surface mount technology are cleanroom and ESD-Safe because most SMD electronic components, like semiconductors, are very sensitive to static charge. The cleanroom environment prevents these components from getting damaged because of static electricity.
SMT is used almost exclusively for the manufacture of electronic circuit boards these days. They are smaller, often offer a better level of performance and they can be used with automated pick and place machine that in many cases all bit eliminate the need for manual intervention in the assembly process.Wired components were always difficult to place automatically because the wires needed to be pre-formed to fit the relevant hole spacing, and even then they were prone to problems with placement.
Although many connectors and some other components still require assisted placement, printed circuit boards are normally developed to reduce this to an absolute minimum, even to the extent of altering the design to use components that can be placed automatically. In addition to this, component manufacturers have developed some specialised surface mount versions of components that enable virtually complete automated assembly for most boards.