Robustness of CMS HGCal Silicon modules under HL-LHC irradiation conditions

The CMS Collaboration is preparing to build replacement endcap calorimeters for the High Luminosity LHC (HL-LHC) era. The new High-Granularity Calorimeter (HGCal) is a highly granular sampling calorimeter with approximately six million silicon channels, as well as about four hundred thousand scintillator tiles whose output is read by on-tile silicon photomultipliers. The calorimeter is designed to operate in the harsh radiation environment of the HL-LHC, where pile-up is expected to exceed 140. The silicon part of the calorimeter will be made of about 26000 silicon modules. During the last two years, several irradiation campaigns were carried out where modules with different baseplate materials were irradiated in a Co-60 facility up to 150 MRad absorbed dose. These modules were then thermal cycled and tested both at 20C and -40C to explore their robustness at high radiation dose. In this talk, results for different thermal cycling campaigns on irradiated modules with Cu-W and Ti baseplates will be presented.