Surface mount inductors are electromagnetic induction components made by winding insulated wires. They are commonly used inductive components.

The function of a surface mount inductor is to pass DC and block AC – this is a simplified explanation.  It isolates and filters AC signals, or forms resonant circuits with capacitors and resistors.

The function of tuning and frequency selection inductors: An inductor coil and a capacitor can be connected in parallel to form an LC tuning circuit. Any current in the circuit containing a surface mount inductor will generate a magnetic field, and the magnetic flux of this field acts on the circuit.

When the current through the surface mount inductor changes, the DC voltage generated in the inductor will oppose the change in current. When the current through the inductor coil increases, the self-induced electromotive force generated by the inductor coil is opposite to the direction of the current, preventing the increase in current, and simultaneously converting a portion of the electrical energy into magnetic field energy stored in the inductor; therefore, after filtering by the inductor, not only are the pulsations of the load current and voltage reduced, and the waveform becomes smoother, but the conduction angle of the rectifier diode also increases. Shielded surface mount inductors have a different function than ordinary surface mount inductors. Ordinary surface mount inductors are not shielded in the circuit, and their use may not achieve the desired effect. Shielded surface mount inductors can shield against some current instability in the circuit, effectively acting as a barrier. A shielded inductor's complete metal shield surrounds the positively charged conductor, inducing an equal amount of negative charge on the inner side of the shield and an equal amount of positive charge on the outer side. If the metal shield is grounded, the positive charge on the outer side will flow into the ground, and there will be no electric field on the outer side, meaning the electric field of the positively charged conductor is shielded within the metal shield.

Shielded inductors also play a coupling role in the circuit. To reduce the coupling interference voltage of the alternating electric field on sensitive circuits, a shielded surface mount inductor can be placed between the interference source and the sensitive circuit, and the metal shield is grounded. The magnitude of the coupling interference voltage from an alternating electric field to a sensitive circuit depends on the product of the alternating electric field voltage, the coupling capacitance, and the grounding resistance of the metal shield. By ensuring that the metal shield is properly grounded, the coupling interference voltage from the alternating electric field to the sensitive circuit can be significantly reduced. Electric field shielding is primarily based on reflection; therefore, the thickness of the shield does not need to be excessive, with structural strength being the main consideration.