Definition

Thermal vias are plated through-holes designed to transfer heat from components to copper planes or the opposite side of the PCB. They're commonly used under QFN and BGA thermal pads to conduct heat to inner ground planes or bottom-side heatsinks. Arrays of 0.3mm thermal vias on 0.6mm pitch can reduce junction temperature by 20-40°C. Vias directly under thermal pads should be plugged or capped to prevent solder wicking during reflow. Vias outside the pad area can be tented with solder mask instead, which costs less. More vias improve thermal conductivity but may weaken the pad structure if too densely packed.