This part is a kind of semiconductor called 2SK2039.
Function of this product has N-Channel MOSFET Transistor.
Manufacturers : Inchange Semiconductor
Image and pinout :

Some of the text within the PDF file :
INCHANGE Semiconductor isc N-Channel MOSFET Transistor isc Product Specification 2SK2039 DESCRIPTION ·Drain Current –ID= 5A@ TC=25℃ ·Drain Source Voltage- : VDSS= 900V(Min) ·Fast Switching Speed APPLICATIONS ·Switching regulators ·UPS ·DC-DC converters ·General purpose power amplifier ABSOLUTE MAXIMUM RATINGS(Ta=25℃) SYMBOL ARAMETER VALUE UNIT VDSS Drain-Source Voltage (VGS=0) VGS Gate-Source Voltage ID Drain Current-continuous@ TC=25℃ 900 ±30 5 V V A ID(puls) Pulsed drain current 15 A Ptot Total Dissipation@TC=25℃ 150 W Tj Max. Operating Junction Temperature 150 ℃ Tstg Storage Temperature Range -55~150 ℃ ·THERMAL CHARACTERISTICS SYMBOL PARAMETER MAX UNIT Rth j-c Rth j-a Thermal Resistance, Junction to Case 0.833 ℃/W Thermal Resistance, J [ ... ]
2SK2039 PDF Datasheet Download
