100 V, 40 A FERD in a fully isolated TO-220
The STMicroelectronics FERD40H100SFP is a Field Effect Rectifier Diode (FERD) rated for 100 V DC reverse voltage and 40 A average rectified current. It is part of the EconoPACK™ 2 series and comes in a TO-220-3 Full Pack package (TO-220FPAB), which means the back tab is fully isolated — no insulating pad or washer is needed between the device and the heatsink. That saves a BOM line and a manual assembly step.
At 20 A forward current the maximum forward voltage is 675 mV. That is low for a 100 V / 40 A rectifier — the FERD structure trades a slightly higher reverse leakage for a lower Vf compared to a standard ultrafast diode of the same voltage class. The reverse leakage at 100 V is 190 µA, which is the price paid for that conduction loss advantage. The recovery speed is listed as Standard Recovery >500 ns at >200 mA. This is not a fast-recovery or ultrafast diode — it is meant for line-frequency rectification, not for a 100 kHz PFC boost stage.
Junction temperature and thermal management
The maximum junction temperature is 175 °C, which is the standard ceiling for silicon power diodes in industrial and motor-drive environments. The TO-220 Full Pack package has a higher thermal resistance than the standard TO-220 because the plastic encapsulation adds an insulating layer between the die and the heatsink. For a 40 A average current at elevated ambient, the heatsink must be sized to keep the junction below 150 °C in steady state to leave headroom for overload transients.