Testing of the front-end hybrid circuits for the CMS Tracker upgrade

Abstract

The upgrade of the CMS Tracker for the HL-LHC requires the design of new doublesensor, silicon detector modules, which implement Level 1 trigger functionality in the increased luminosity environment. These new modules will contain two different, high-density front-end hybrid circuits, equipped with flip-chip ASICs, auxiliary electronic components and mechanical structures. The hybrids require qualification tests before they are assembled into modules. Test methods are proposed together with the corresponding test hardware and software. They include functional tests and signal injection in a cold environment to find possible failure modes of the hybrids under real operating conditions.

Quality Control Considerations for the Development of the Front End Hybrid Circuits for the CMS Outer Tracker Upgrade

“…It relies on signal injection strips buried under the wire bond pads directly inside the flexible circuit of the hybrid. This solution eliminates the problems of precise positioning of an external antenna circuit described in [2] thus speeding up the testing procedure. After being used, those signal injection strips need to be grounded to avoid the presence of floating conductors in the close proximity of analogue interconnections.…”

“…For example, for a 10-bit DAC it requires only 10 data taking iterations instead of full 1024-step S-curve scan. The logic of shorts and opens recognition remained unchanged and is described in [2].…”

A High Throughput Production Scale Front-End Hybrid Test System for the CMS Phase-2 Tracker Upgrade

“…These test cards share the same geometry for the card outline and the connector placement. The functions are also similar: signal level translation, buffering, analogue to digital conversion and other tests to qualify the hybrids [5]. The PS-FEH test card has additional complexity as it includes also a spring loaded needle test socket with mechanical structures pressing the hybrids onto the socket.…”

Front-end hybrids for the strip-strip modules of the CMS Outer Tracker Upgrade

“…It is compatible with the latest Service Hybrid design and its connector's pin assignment. It was fully routed following the manufacturing constraints and implementing all necessary testing features described in [4]. The design was studied in terms of the voltage drop budget across the power and return plane, which are well balanced as shown in Figure 5.…”