Design and Production of the CMS High Granularity Calorimeter Mockup Modules

During the LHC long shutdown 3 (2024-2026), the Compact Muon Solenoid (CMS) experiment will replace its current endcaps with a high granularity calorimeter (HGCAL) that comprises ~6M silicon cells and ~400K scintillator tiles. HGCAL will operate at -30 C in order to keep electronics noise low and charge collection efficiency as high as possible to maintain MIP calibration capability. A mock-up program for silicon-based modules is underway to optimize materials and construction techniques to meet the challenges of cold operation. We present the current design, material choices, assembly process, and results of thermal and mechanical studies to date.