QFNs lack traditional exterior leads, instead using metalized terminal pads on the bottom. This "near chip-scale" footprint makes them 62% smaller than traditional TSSOP packages.
Different types of QFN packages are used based on the specific application's needs: What Are QFN Packages | Sierra Circuits
A central exposed thermal pad on the bottom of the package can be soldered directly to the PCB, facilitating rapid heat dissipation and preventing the chip from overheating.
Short internal bond wires reduce lead inductance and impedance, which enhances signal integrity and makes them ideal for high-speed and high-frequency applications.
The low-profile, leadless construction makes these packages physically sturdy and less prone to damage during handling. Common Variations