This TAJC686K006SNJ is a 68 µF molded tantalum capacitor rated at 6.3 V with ±10% tolerance and a 1.5 Ohm ESR. It is part of the TAJ series from KYOCERA AVX, packaged in the standard C size code (2312 / 6032 metric). The 1.5 Ohm ESR sets the ripple current handling — for a typical 100 kHz buck converter output, the capacitor's self-heating stays within limits when the RMS ripple current is below ~400 mA. The 6.3 V rating provides a 20% derating margin on a 5 V rail, which is standard practice for tantalum reliability.
The TAJ series is a mature, widely second-sourced platform — if a BOM line needs a backup, the same C-size 68 µF 6.3 V ±10% rating is available from multiple tantalum manufacturers.