This part is a kind of semiconductor called ST120-100L2MI.

Function of this product has Wet Tantalum Capacitors.

Manufacturers : Vishay

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Some of the text within the PDF file :

www.vishay.com ST Vishay SuperTan® Wet Tantalum Capacitors with Hermetic Seal Vishay ST represents a major breakthrough in wet tantalum capacitor technology. Its unique cathode system provides the highest capacitance per unit volume. The design facilitates a doubling of capacitance, lower ESR and higher ripple current rating compared with conventional wet tantalum products. Moreover, the ST has the capacitance stability of a solid tantalum capacitor and there are no circuit impedance restrictions. The ST is housed in an all tantalum, hermetically sealed case and is manufactured to withstand hazardous environments. The ST is used widely in the defense and aerospace industries and whenever there is a space problem. PERFORMANCE CHARACTERISTICS Operating Temperature: -55 °C to +85 °C (to [ ... ]

ST120-100L2MI PDF Datasheet Download