The part and what it does
The JMK105BJ334KV-F is a 0.33 µF multilayer ceramic capacitor in the 0402 (1005 metric) surface-mount package, rated 6.3 V with an X5R temperature coefficient. As a Series M part from Taiyo Yuden, it targets SMPS filtering — the 6.3 V rating sits at the lower end of the MLCC voltage stack, so confirm it clears the highest rail voltage present on the switching node where it decouples. The 0402 body measures 1.00 mm × 0.50 mm with a maximum thickness of 0.55 mm — standard fan-out works on a two-layer board, though the thin profile means the part is sensitive to paste volume and reflow offset; check the land pattern against Taiyo Yuden's recommended footprint before committing to a layout.
Temperature grade and filtering context
X5R with an operating range of -55 °C to +85 °C marks this as a commercial-temperature MLCC — adequate for indoor consumer and industrial equipment PCBs, but not the extended temperature range needed for under-hood or outdoor enclosures. If the SMPS runs in a heated cabinet or near a thermal source, a larger X7R or X8R part would carry more margin. The ±10% tolerance class is standard for bulk decoupling in a switching supply — it is not a precision hold-up or timing reference, so the tolerance band does not constrain SMPS loop design. When selecting for ripple filtering near the switching frequency, the ESR and impedance profile of the X5R dielectric matter more than the capacitance tolerance.