Reliability test results of the interconnect structures of the front-end hybrids for the CMS Phase-2 Tracker Upgrade

High Density Interconnect (HDI) hybrids are being developed for the CMS Tracker Phase Two Upgrade for the HL-LHC. These hybrids are carbon fibre reinforced flexible circuits with flip-chips, passives and connectors. Their operational lifetime is determined by the reliability of the solder joints of the surface mount components (flip-chips, passives, connectors) and the copper traces and vias in the hybrid substrate. Specific test coupons were exposed to accelerated thermal stress cycles, aiming to test the reliability of the solder joints, vias and traces. Results from different suppliers and technologies will be evaluated and compared.