Dual NPN/PNP transistor in a 1.6 × 1.6 mm footprint
It is designed for space-constrained switching and amplifier stages where a matched pair saves board area and reduces component count. The NPN side transitions at 180 MHz, the PNP at 140 MHz, giving enough bandwidth for low-speed switching, signal buffering, and small-signal amplification up to the low-MHz range.
The SOT-563 (also listed as SOT-666) is a tiny six-lead package, roughly 1.6 × 1.6 mm. The small body means low thermal mass, so it reflows quickly; the 150°C junction maximum means you want a standard lead-free profile and no extended dwell above 260°C peak.