Quality control considerations for the development of the front end hybrid circuits for the CMS Outer Tracker upgrade

The upgrade of the CMS Outer Tracker for the HL-LHC requires the design of new double-sensor modules. They contain two high-density front end hybrid circuits, equipped with flip-chip ASICs, passives and mechanical structures. First prototype hybrids in a close-to-final form have been ordered from three manufacturers. To qualify these hybrids a test setup was built, which emulates future tracker temperature and humidity conditions, provides temporary interconnection, and implements testing features. The system was automated to minimize the testing time in view of the production phase. Failure modes, deliberately implemented in the produced hybrids, provided feedback on the system’s effectiveness.