This document describes a multi-function module for mmWave communication and user input using mechanical switches in an electronic device. The multi-function module may be located behind a non-conductive button (e.g., volume button, power button) of the electronic device. Further, the multi-function module includes an elongated antenna substrate with mechanical switches mounted thereon and distributed along a longitudinal length of the antenna substrate. At least one of the mechanical switches is implemented as a radiating element for a mmWave patch antenna. The multi-function module also includes one or more integrated circuit components mounted to the antenna substrate and configured to use the at least one mechanical switch as the radiating element for the mmWave patch antenna to provide the mmWave communication. In this way, the multi-function module enables the mechanical switches to coexist with the mmWave patch antennas.