Embodiments disclosed herein include a modular microwave source array. In an embodiment, a housing assembly for the source array comprises a first conductive layer, wherein the first conductive layer comprises a first coefficient of thermal expansion (CTE), and a second conductive layer over the first conductive layer, wherein the second conductive layer comprises a second CTE that is different than the first CTE. In an embodiment, the housing assembly further comprises a plurality of openings through the housing assembly, where each opening passes through the first conductive layer and the second conductive layer.