An Introduction to Surface Mount PCB Technology

Introduction to Surface Mount PCB Technology

Look inside any piece of commercially made electronic equipment these days and you will see a lot of tiny devices, many of which are minute in size. Rather than using traditional components with wire leads these devices have been mounted onto the surface of the printed circuit board using a technique known as surface mount pcb technology or SMT for short. This enables much more functionality to be incorporated into electronic products in a smaller package, and considerably speeds up PCB assembly.

SMT is the most prevalent method of component mounting on electronic PCBs. The main advantage of SMT is that it enables components to be placed much closer together on the circuit board than would be possible with traditional leaded components. This allows a far greater level of functionality to be included within a small package, and helps satisfy the continuous demand for smaller electronic devices.

Another significant benefit of SMT is that it eliminates the need for drilled holes to be used to hold the components in place. This greatly simplifies the process of manufacturing a PCB and also reduces the risk of errors during assembly. It also makes it much easier to use automated systems for PCB assembly.

SMT component packages generally have smaller diameters than their leaded counterparts, and this allows more circuits to be fitted into the same footprint on the printed circuit board. The smaller component sizes also mean that a smaller amount of solder needs to be used, which reduces the overall cost of the assembled device.

An Introduction to Surface Mount PCB Technology

The smaller component sizes also reduce the interference coupling that would otherwise occur between adjacent tracks on a multilayer board, and this is a significant advantage for EMC considerations. However, the use of SMT components requires that a multilayer board construction with a grounded ground plane be used, in order to take full advantage of the reduced interference reduction that it offers.

One disadvantage of SMT is that it is often more difficult to inspect the completed electronic product for defects than a through-hole product. This is because the solder connections on SMT devices are typically very fragile, and they can be more prone to failure under stress than through-hole connections. This can be mitigated, however, by ensuring that the appropriate inspection and test methods are employed during SMT production.

As the name suggests, SMT devices are designed to be set down and soldered directly onto a PCB’s surface. The majority of popular basic components like capacitors and resistors now come in surface mount versions as well as their traditional leaded counterparts, but more specialist types such as transistors and logic and analogue ICs are only available as surface mount components.

Finally, SMT components are usually less heat-tolerant than their leaded equivalents and this can be a significant issue in some applications. This is particularly important in PCBs that are likely to be subjected to thermal shock or vibration. Ongoing research is helping to address this issue and ongoing advances in component design are making SMT components more reliable in high-temperature applications.

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