This part is a kind of semiconductor called FCU20UC30.

Function of this product has SILICON DIODE.

Manufacturers : UTC

Image and pinout :

Some of the text within the PDF file :

UNISONIC TECHNOLOGIES CO., LTD FCU20UC30 Preliminary SILICON DIODE  DESCRIPTION The UTC FCU20UC30 is a diode, it uses UTC’s advanced technology to provide customers with low peak reverse current, etc.  FEATURES * Low peak reverse current  SYMBOL DIODE  ORDERING INFORMATION Ordering Number Lead Free Halogen Free FCU20UC30L-TA3-T FCU20UC30G-TA3-T FCU20UC30L-TF3-T FCU20UC30G-TF3-T FCU20UC30L-TF1-T FCU20UC30G-TF1-T Note: Pin Assignment: A: Anode K: Cathode Package TO-220 TO-220F TO-220F1 Pin Assignment 123 AKA AKA AKA Packing Tube Tube Tube  MARKING www.unisonic.com.tw Copyright © 2014 Unisonic Technologies Co., Ltd 1 of 3 QW-R601-278.a FCU20UC30 Preliminary DIODE  ABSOLUTE MAXIMUM RATINGS (TA=25°C, unless otherwise specified) PARAMETER SYMBOL [ ... ]

FCU20UC30 PDF Datasheet Download