This part is a kind of semiconductor called U20UC20.

Function of this product has SILICON DIODE.

Manufacturers : UTC

Image and pinout :

Some of the text within the PDF file :

UNISONIC TECHNOLOGIES CO., LTD U20UC20 Preliminary SILICON DIODE  DESCRIPTION The UTC U20UC20 is a diode, it uses UTC’s advanced technology to provide customers with low peak reverse current, etc.  FEATURES * Low peak reverse current DIODE  ORDERING INFORMATION Ordering Number Lead Free Halogen Free U20UC20L-TF1-T U20UC20G-TF1-T Note: Pin Assignment: A: Anode K: Cathode Package TO-220F1 Pin Assignment 123 AKA Packing Tube U20UC20L-TF1-T (1)Packing Type (2)Package Type (3)Green Package (1) T: Tube (2) TF1 : TO-220F1 (3) L: Lead Free, G: Halogen Free and Lead Free  MARKING www.unisonic.com.tw Copyright © 2014 Unisonic Technologies Co., Ltd 1 of 3 QW-R601-086.b U20UC20 Preliminary DIODE  ABSOLUTE MAXIMUM RATINGS PARAMETER SYMBOL RATINGS UNIT Rep [ ... ]

U20UC20 PDF Datasheet Download