A new stress-relieving layer in ATLAS ITk strip modules

The Inner Detector system of the ATLAS experiment will be replaced with a new all-silicon detector known as the Inner Tracker (ITk) to prepare for high particle-rate conditions at the High Luminosity LHC. The innermost layers of the ITk will be composed of silicon pixels, while the outer layers will consist of silicon strips. The basic element of the ITk Strip detector is the module, composed of front-end electronics glued to a silicon microstrip sensor. A critical problem was encountered during module pre-production wherein some silicon sensors cracked due to thermal stresses when mounted to local support structures and brought to cold operating temperatures. A potential solution has been trialed in which the modules are redesigned to include a new layer of soft glue between the front-end electronics and the silicon sensor to absorb thermal stresses. This redesign necessitated a new R&D phase of the project. These proceedings explore the technical challenges of incorporating the stress-relieving layer into the module assembly chain and evaluate the impact of the redesign on prototype module performance.