TAJB155K025RNJ is a molded tantalum capacitor from the KYOCERA AVX TAJ series, rated 1.5 µF at 25 V with ±10% tolerance and 5 Ohm ESR. The molded construction gives it a stable mechanical profile for automated pick-and-place assembly on a standard 1411 (3528 Metric) footprint.
ESR and temperature — what the 5 Ohm spec means for your board
The 5 Ohm ESR at 25 V and 1.5 µF sets the ripple current capability — for a typical buck converter output filter, the self-heating from ripple current through this ESR must stay within the 125°C ceiling. At 100 kHz, the ESR dominates the impedance, so the capacitor's filtering effectiveness is limited above a few hundred milliamps of ripple. The B case code (3.50 mm x 2.80 mm x 2.10 mm) fits the standard 1210 footprint — the 0.083 inch seated height clears most low-profile enclosures. The molded body is not hermetically sealed, so conformal coating is recommended in condensing or washdown environments.