This part is a kind of semiconductor called FS40SM-6.

Function of this product has Nch POWER MOSFET HIGH-SPEED SWITCHING USE.

Manufacturers : Powerex Power Semiconductors

Image and pinout :

Some of the text within the PDF file :

MITSUBISHI Nch POWER MOSFET FS3UM-18A HIGH-SPEED SWITCHING USE FS3UM-18A OUTLINE DRAWING 10.5MAX. r 3.2 7.0 Dimensions in mm 4.5 1.3 16 φ 3.6 3.8MAX. 1.0 12.5MIN. 0.8 2.54 2.54 4.5MAX. 0.5 2.6 q w e wr q GATE w DRAIN e SOURCE r DRAIN e q ¡VDSS 900V ¡rDS (ON) (MAX) 4.0Ω ¡ID 3A TO-220 APPLICATION SMPS, DC-DC Converter, battery charger, power supply of printer, copier, HDD, FDD, TV, VCR, personal computer etc. MAXIMUM RATINGS Symbol VDSS VGSS ID IDM PD Tch Tstg (Tc = 25°C) Parameter Drain-source voltage Gate-source voltage Dr [ ... ]

FS40SM-6 PDF Datasheet Download