The upgrade of the CMS tracker for the HL-LHC is based on a binary readout scheme using the CMS Binary Chip (CBC2). The connectivity requirements of this flip-chip ASIC requires the use of high density interconnecting hybrids. Module integration studies indicated that a foldable flexible hybrid circuit results in an optimal module arrangement. A full module size HDI flexible hybrid was designed, integrating eight CBC2 ASICs. The hybrid is fitted with carbon fiber stiffeners and a sharp folding allows connecting the two strip sensor wirebond arrays. The front end circuit development was focused on the 2 Strip (2S) module electronics. This paper will present the implementation of the 2S front end electronics on a flexible substrate covering the mechanical and electrical properties of the assembly.
The CMS tracker upgrade for the HL-LHC relies on different module types, depending on the position of the respective module. They are built with high-density interconnection flexible circuits that are wire bonded to silicon strip and pixel-strip sensors. The Front-End hybrids will contain several flip-chip bonded readout ASICs that are still under development. Mock-up prototypes are used to qualify the advanced flexible circuit technology and the parameters of the hybrids. This paper presents the Pixel-Strip (PS) mock-up hybrid in terms of testing, interconnection, fold-over, thermal properties and layout feasibility. Plans for circuit testing at operating temperature (-30°C) are also presented.
K: Front-end electronics for detector readout; Radiation-hard electronics; Detector design and construction technologies and materials; Manufacturing
High Density Interconnect hybrids are being developed for the CMS tracker Phase-2 upgrade for the HL-LHC. These hybrids are flexible circuits laminated to carbon fiber composite stiffeners and are assembled with flip-chips, passives and connectors. The wire bonding to sensors and the soldering requirements for these components requires an almost perfectly flat surface. A lamination process is proposed, focused on the compatibility with a lead-free reflow process. The stack-up of the hybrid was optimized to balance the forces induced by the Coefficient of Thermal Expansion (CTE) differences in the assembly. The proposed lamination process was applied to prototype 8CBC3 hybrid circuits.
More than twenty-five thousand hybrids will be produced for the CMS Outer Tracker Phase-2 Upgrade. The hybrids are assembled with flip-chips, passives and carbon-fibre stiffeners. They will be glued to their module supports, together with powering and optical transmission hybrids, making repairs almost impossible. Due to the complexity of the hybrid circuits and the circuit assembly, production scale testing is a very important aspect. A crate-based scalable test system was designed to enable a multiplexed test of front-end hybrids. A test card was produced for the 2S hybrids and two different hybrid test cards are under development.
Sixteen thousand 2S front-end hybrids and twelve thousand PS front-end hybrids will be produced for the CMS Tracker Phase-2 upgrade. The hybrids consist of flip-chips, passives and mechanical components mounted on a flexible substrate, laminated onto carbon-fibre stiffeners with thermal expansion compensators. In the prototyping phase, several critical issues have been solved to manufacture these complex circuits. Final designs are now reaching readiness for the full-scale production. Lessons learned during the prototyping phase and different improvements implemented for manufacturability will be presented in this contribution.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.