In Surface Mounted Technology (SMT), components are placed directly onto the surface of a PCB to make what’s referred to as a surface-mount device (SMD).
Due to its efficiency and effectiveness, Surface Mounted Technology (SMT) has widely replaced through-hole technology methods for constructing PCBs, however, both methods are often utilized on an equivalent PCB. This is due to some components that are simply not suited to surface mounting.
These components may have large transformers and heatsinked power semiconductors. Generally speaking, SMT components are smaller in size than through-hole units as they need smaller leads or don’t have any leads in the least.
The primary advantage of SMT is size. Because today’s electronics are expected to be more compact, there is an increase in demand for smaller units.
SMT makes this possible. But despite the fact that these units are not as bulky as older devices, there is actually a much higher component density, as well as more connections per each component. This means that electronics are often more efficient and advanced than ever before, while still being as compact as possible.
Fewer holes need to be drilled into the boards which leads to faster and more automated assembly processes, and the fact that components are able to be situated on either side of the circuit board simplifies things further. On top of this, there are many SMT parts and components that really cost but their through-hole counterparts.
All of this leads to a lower initial cost, less time required for fixing and production, reduced manufacturing cost, and more efficient use of your time.
Unfortunately, there are not any perfect or fool-proof manufacturing processes, and SMT does have its drawbacks also. As an example, SMT isn’t fitted to any large, high-power/high-voltage parts. Because of this, SMT and through-hole construction may have to be combined for better results.
Additionally, the tiny size of SMDs can create issues, therein the solder joint dimensions still grow smaller as advances are made toward ultra-fine pitch technology. Ultimately, this means that less solder is able to be used for each joint which can result in voiding, and integrity issues.
The solder connections of SMDs are also capable of being damaged by potting compounds as they go through thermal cycling. Lastly, SMT shouldn’t be used because of the sole attachment method for any components which will be subject to ongoing mechanical stress, as an example, connectors that are utilized to interface with the external devices which are often attached.
When Should Surface Mounted Technology be used?
Because of its many benefits, the bulk of products manufactured at this point utilize surface mounted technology.
Despite this, we’ve seen that SMT isn’t suitable altogether cases. As a rule, SMT should be considered if:
Your products must be very small/compact.
Your products must be able to accommodate large volumes of memory.
Your final product must be sleek and lightweight despite the component density
Your product will need to be able to function at high speed/frequencies
You need to produce large quantities with automated technology
Your product should only transmit little or no noise
Your product must be ready to accommodate an excellent deal of huge, high lead-count complex ICS
The main advantages of SMT are
Much higher component density (components per unit area) and lots of more connections per component.
Components are often placed on each side of the circuit card.
The Higher density of connections because holes don’t block routing space on inner layers, nor on back-side layers, if components are mounted on just one side of the PCB.
Small errors in component placement are corrected automatically because the physical phenomenon of molten solder pulls components into alignment with solder pads.
(On the opposite hand, through-hole components can’t be slightly misaligned, because once the leads are through the holes, the components are fully aligned and can’t move laterally out of alignment.)
Better mechanical performance under shock and vibration conditions (partly thanks to lower mass, and partly thanks to less cantilevering)
Better EMC performance (lower radiated emissions) thanks to the smaller radiation loop area (because of the smaller package) and therefore the lesser lead inductance.
Fewer holes need to be drilled. (Drilling PCBs is time-consuming and expensive.)
Lower initial cost and time of fixing for production, using automated equipment.
Simpler and faster-automated assembly. Some placement machines are capable of placing quite 136,000 components per hour.
Many SMT parts cost but equivalent through-hole parts.
A surface-mount package is favored where a coffee profile package.
SMT maybe be unsuitable due to the only attachment method for components that are subject to frequent mechanical stress, like connectors that are used to interface with external devices that are frequently attached and detached.
SMDs’ solder connections could also be damaged by potting compounds browsing thermal cycling.
The Handling of small SMT components is often difficult, requiring tweezers, unlike nearly all through-hole components. SMDs are easily removed from the place by slightly of a hand tool.
Without developed skills when manually soldering it is very easy to reflow the solder of an adjacent SMT component and displace it.
Many types of SMT component packages can’t be installed in sockets, which give for straightforward installation or exchange of components to switch a circuit and straightforward replacement of failed components.