SMT resistors or surface mount technology resistors are a type of passive electronic component. They are more precisely a low profile resistor that mounts directly to the printed circuit board (PCB) as opposed to a thru-hole resistor where the axial leads go through the board while the body of the resistors rests on top. They are extremely useful and popular where space or PCB real estate is at a premium.
There are a number of different styles or types of SMT resistors. Chip resistors are common place in many mobile phones and other portable electronic devices where "the smaller the better" is the battle cry and board space is extremely valuable, but power requirements are very low. They can be either thick film or thin film, depending upon the application requirement. These resistors have the connectors or contacts directly on the resistors itself and are therefore soldered directly to the board.
Another type of SMT resistor has leads extending from its body and are bent in such a way that the resistor itself is flush with the PCB. These are called gull wings and they can achieve higher power levels than there SMT chip counterparts. There are some on the market that are rated as high as 35 watts. Beware, however, as many of the SMT resistors with higher power ratings stipulate a lower temperature or specify the type of mounting in order to dissipate the necessary heat.
Lastly, for our discussion, there is the disk resistor. It is cylindrical in nature and is used in high frequency applications. They are used in low inductance applications because their geometry does not create a magnetic field. These type resistors are more common in RF and microwave applications.
In this world of smaller and smaller mobile devices, SMT resistors will be with us for the foreseeable future. As the power requirements continue to be reduced, so will the size of these SMT resistors.
