This part is a kind of semiconductor called 1SMB5918B.

Function of this product has SILICON ZENER DIODES.

Manufacturers : EIC

Image and pinout :

Some of the text within the PDF file :

www.eicsemi.com 1SMB5913B - 1SMB5956B VZ : 3.3 - 200 Volts PD : 3.0 Watts FEATURES : * Complete Voltage Range 3.3 to 200 Volts * High peak reverse power dissipation * Flat handling surface for accurate placement * Low leakage current * Pb / RoHS Free MECHANICAL DATA * Case : SMB Molded plastic * Epoxy : UL94V-0 rate flame retardant * Lead : Lead Formed for Surface Mount * Polarity : Color band denotes cathode end * Mounting position : Any * Weight : 0.108 gram SILICON ZENER DIODES SMB (DO-214AA) 5.30 ± 0.22 4.65 ± 0.30 1.14 ± 0.38 0.1 ± 0.1 2.1 ± 0.15 3.62 ± 0.32 0.22 ± 0.07 2.28 ± 0.15 Dimensions in millimeters MAXIMUM RATINGS Rating Maximum Steady State Power Dissipation at TL = 75°C, Measured at Zero Lead Length Derate Above 75 °C Thermal Resistance From Junction to Le [ ... ]

1SMB5918B PDF Datasheet Download