Heat removal capabilities and radiation performances of several sparse antenna array topologies are studied for cooling enhancement in 5G millimeter-wave base station antennas. Both electromagnetic and thermal aspects are jointly considered for the first time in array layout optimization and a novel connection between layout sparsity and thermal management is presented. Two types of active electronically scanned arrays (AESA’s), based on the traditional and planar approaches, are examined. Thermal management in AESA’s is discussed, with a focus on cooling challenges at millimeter waves. Being relatively low-cost and low-profile while supporting flexible beamforming, passively cooled planar AESA’s with fanless CPU coolers are proposed, for the first time, to be used in 5G base stations. Additional cooling for such arrays is achieved by increasing the inter-element distances in the layout. Linear irregular arrays, spiral arrays, thinned arrays, circular ring arrays and heat sink antenna arrays are revisited with a critical discussion on their electromagnetic and thermal performance. The results are compared with regular and square layouts that are used as benchmarks throughout the paper.@en