Despite increasing needs for efficient thermal solutions for next-generation radio-frequency (RF) devices for 5G/6G communications, accurate spatial temperature characterizations of these devices are lacking, hindering efforts to develop effective thermal designs. During the proposed beamtime, we aim to develop a novel, X-ray nano-diffraction-based thermal metrology technique to accurately characterize internal temperatures of RF devices made of crystalline multi-layers with tens of nm spatial resolution. If successful, our work will deliver, for the first time, a high-resolution internal temperature map of RF devices in situ. Subsequently, we anticipate new innovations in thermal solutions in these electronic devices.