This part is a kind of semiconductor called UFF100-04.

Function of this product has 10A Ultra Fast Recovery Rectifier.

Manufacturers : Frontier

Image and pinout :

Some of the text within the PDF file :

FRONTIER ELECTRONICS CO., LTD. UFF100-005 THRU UFF100-06 10A ULTRA FAST RECOVERY RECTIFIER C ASE : ITO-220AC( UFF100-×× ), FULLY INSULATED PACKAGE O B C D 1 2 J K . MILLIMETERS MIN MAX 10.27 9.72 6.90 6.30 15.50 14.50 13.00 13.80 4.1 4.95 5.20 1.52 0.9 4.8 3.1 2.5 2.9 0.8 Ø 3.4 F H I G PIN 1 PIN 2 CASE L E M B C D E F G H I J K L M O FEATURES ! ULTRA FAST RECOVERY TIME ! LOW FORWARD VOLTAGE ! LOW THERMAL RESISTANCE ! HIGH CURRENT CAPABILITY ! HIGH VOLTAGE ! GLASS PASSIVATED CHIP JUNCTION MECHANICAL DATA ! CASE：TRANSFER MOLDED ! TERMINAL：MIL-STD-202F METHOD 208 ! POLARITY︰AS MARKED ! EPOXY：UL94V-0 FLAME RETARDANT MOLDING COM POUND ! WEIGHT：1.81 GRAMS MAXIMUM RATINGS AND ELECTRICAL CHARACTERISTICS RATINGS AT 25°C AMBIENT TEMPERATURE UNLESS OTHERWISE SPECIFIED SINGLE P [ ... ]

UFF100-04 PDF Datasheet Download