Surface Mount Technology (SMT) is a general term for mounting electronic components directly on the PCB surface. Components such as resistors, capacitors, transistors, integrated circuits can be soldered to the surface of the circuit board thanks to this technology. Such electronic components are called Surface Mount Device (SMD).
The traditional way of mounting electronic components on a circuit board is by inserting the component leads through the hole in the PCB and soldering it to the back surface of the board. This method is called Through Hole Technology (THT).
SMT makes assembly of electronic components easier and faster. On the other hand, it takes up less space, making it possible to design compact cards. Other advantages of SMT are as follows.
- Components can be placed on both sides of the circuit board. This enables smaller PCB designs to be created.
- SMT enables the assembly of thousands of components on the circuit board in minutes with the help of robotic machines. This significantly reduces production time and cost.
- SMT-mounted PCBs can realize high-speed signal transmission as they contain short connections.
The SMT process begins with applying solder paste to the pads on the circuit board. Then the components are placed on the PCB with the help of pick and place machines. The circuit board is passed through a heater, causing the solder to melt and the solder joints to form. At the end of this process, a number of quality control procedures are implemented, including component alignment and solder control.
Although SMT has numerous advantages over THT, SMT is not suitable for some components such as large transformers and semiconductor devices with heat sinks. On the other hand, this mounting method is also not good for harsh environments, as SMT soldered components only to the surface of the board. In such cases, THT may be a better option.
It is possible to use both SMT and THT on the same circuit board. THT is still preferred in military and aerospace products that are exposed to harsh environmental conditions. THT is also widely used in test and prototyping applications where manual adjustments and changes are required.
