This article reports the role of micro-structured surfaces on phase change heat transfer due to impingement of a liquid micro-jet array. Experiments are conducted with an array of sixteen free surface DI water jets, each 125 μm diameter, at two different jet Reynolds number conditions of 1012 and 1747. A systematic, parametric study is carried out with eight different micro-structure patterns, all square cross-section micro-studs, by varying stud size, height, spacing, and stud arrangement (in-line and staggered array of studs). The structures are fabricated over a base area of 0.0001 m₂ (1 cm₂). In general, compared to the plain base surface, all the micro-structures improve impingement boiling heat transfer. The performance enhancement occurs in all regimes of boiling: at the onset, fully developed nucleate boiling and the critical heat flux (CHF). The optimal microstructure shows up to 78% increase in CHF compared to the plain surface. Heat flux in excess of 1000 Watts/cm₂ is demonstrated. The results are explained in light of the three distinct roles played by the micro-structures: (a) additional surface area, (b) additional bubble nucleation sites, and (c) obstruction to spreading of the high-speed, thin liquid film on the impingement surface.