This study presents a comprehensive numerical investigation of the thermo-hydraulic performance of microchannel heat sinks with fan-shaped cavities, where pin fins of varying geometries, sizes, and eccentric placements are embedded specifically in the arcuate region of the cavity. A unit cell from a thirty-three-channel array is simulated using deionized water as coolant under laminar flow conditions across Reynolds numbers from 100 to 500. The analysis considers heat transfer coefficient (h), maximum base temperature (Tmax), thermal resistance (Rth), pressure drop (ΔP), and performance factor (PF). Results show that pin fins in the arcuate region significantly enhance convective heat transfer by increasing surface area and inducing strong vortical structures, while also influencing hydraulic performance. Among the tested geometries, circular fins provide the most balanced thermo-hydraulic behaviour, whereas rhombus fins maximize heat transfer but at higher pressure penalties. Variation in fin size reveals that intermediate diameters achieve the best trade-off between heat transfer and hydraulic resistance. Eccentric placement of fins within the arcuate cavity strongly affects local flow structures. Along the y-axis, the Ey1 configuration demonstrates up to 19% enhancement in heat transfer over the baseline Ey0 due to improved flow guidance and mixing, albeit with moderate pressure rise, while Ey − 1 yields the poorest performance. Along the z-axis, the Ez − 2 configuration achieves up to 8% improvement in heat transfer relative to the baseline, driven by vortex-induced mixing, though accompanied by higher pressure drops. Despite these trade-offs, the performance factor remains above unity for all cases, confirming overall thermal benefits. The novelty of this work lies in the systematic evaluation of pin–fin geometry, size, and eccentric placement confined solely to the arcuate region of fan-shaped cavity microchannels, an aspect not previously reported in microchannel heat sink studies. The findings provide practical design insights for optimizing microchannel heat sinks intended for high-performance microelectronic cooling applications.