The TAJW156K010RNJ: This is a KYOCERA AVX TAJ series molded tantalum capacitor, 15 µF at 10 V rated, ±10% tolerance, with a 700 mOhm ESR. The molded case is standard for surface-mount tantalums — it gives consistent mechanical protection and a clear polarity stripe, so you can orient it right the first time on the board. That wide band makes it a candidate for automotive under-hood modules, industrial outdoor controls, or avionics power rails where the ambient swings hard.
ESR and ripple — what the 700 mOhm means on the board
The 700 mOhm ESR is the equivalent series resistance at 100 kHz typical for this size code W. For a 15 µF cap on a 10 V rail, that ESR limits the ripple current it can handle before self-heating becomes a derating factor. In a buck converter output filter, the ESR sets the output ripple voltage — lower ESR means less ripple for the same switching current. If you are paralleling several of these to get more capacitance or lower net ESR, watch the voltage derating: tantalum caps need a 20% margin on the rated voltage for reliable operation, so on a 10 V rail you are at the limit. A 16 V rated part would give more headroom.