Electronic surface mount components are attached directly to the printed circuit board (PCB). They are also known as SMT components (surface mount technology) or SMD (surface mount devices). These components can be either active or passive electronic components. Some of the types of components made in these surface mount configurations include: capacitors, inductors, resistors, semiconductors, and thermistors,
The actual technology was developed in the 1960’s, but was not fully implemented or widely used until the 1980’s. This technology helped to allow for the progression of smaller and smaller electronic devices such as calculators and computers. It also helped to open the door to an entirely new industry, electronic contract manufacturing.
In this process, the components are first put on reels using a tape and reel machine. Then the boards are populated with the various SMD components usually using a pick and place machine. Next, the printed circuit boards are run through a re-flow soldering oven. This solders the components to the board itself with a minimal amount of hand labor.
Their smaller size is not without its drawbacks. Most of the surface mount components cannot carry as much power as the older thru-hole technology because of their smaller size. Sometimes the transformer or inductor must be mounted in a separate (usually by hand) process because they are too large to be tape and reeled. Hence these boards cannot be entirely populated by a pick and place machine.
All in all, however, the surface mount technology is how most components will be manufactured in the future. The call for power is decreasing, with the exception of specific applications, so the smaller size is not an issues for most computers, tablets, and cell phones. Going forward most components will be surface mount devices, if they are not already.