This paper investigates convective chilling and heat transfer characteristics for twelve different round jet array configurations impinging on a heated silver plate. The arrays, ranging from 3×3 to 12×12 with jet diameters between 0.5 mm and 1.7 mm, were tested at five volume flow rates (0.0000167 m³/s to 0.0003 m³/s) at a constant jet-to-target distance of 1.30 mm using an air jet impingement apparatus. For each pair of arrays with identical size, number of jets, and spacing, the array with the smaller jet diameter (0.5 mm) consistently achieved superior convective cooling and higher heat transfer coefficients compared to the larger-diameter array. For example, the 12×12 array with 0.5 mm jets cooled the target surface to temperatures as low as 20.25°C with a heat transfer coefficient of 98,765 W/m²°C at the highest flow rate, outperforming the 12×12 array with 1.7 mm jets under identical conditions. Furthermore, increasing the flow rate improved both chilling effectiveness and heat transfer coefficient across all configurations. These findings demonstrate that smaller jet diameters provide more effective impingement cooling for electronic thermal management applications.