The Infineon AUIRFU4104 is a 40 V, 42 A N-channel HEXFET in the TO-251-3-21 (IPAK) through-hole package, qualified to AEC-Q101 for automotive and harsh-environment power switching. Its 5.5 mOhm Rds(on) at Vgs=10 V and 42 A sets the conduction loss floor — at full rated current that's under 10 W dissipation in the channel alone, but the 140 W package power limit means the junction-to-case thermal path and copper pad area on the PCB drive the real current ceiling.
Gate drive: not a logic-level part
The 4 V gate threshold at 250 µA and 89 nC total gate charge at Vgs=10 V tell you this is a standard-threshold MOSFET — it needs a gate drive swinging to 10 V to hit the rated 5.5 mOhm Rds(on). A 5 V logic-level gate signal leaves it in the linear region, so budget a proper gate driver or a driver with a bootstrap rail above 8 V.
Temperature range and qualification
Junction temperature spans -55°C to 175°C, wider than the typical 150°C max — this part lives in under-hood engine compartments, transmission controllers, or any high-ambient automotive module where the silicon sees sustained heat soak. The AEC-Q101 stamp means it's passed the automotive qualification flow: HTRB, H3TRB, and temperature cycling.
The TO-251 through-hole package is a mature, widely sourced form factor; supply is steady through the standard Infineon distribution channel.