Production and testing of the powerboard for ATLAS ITk Strip barrel modules

Abstract

The upgrade of the ATLAS ITk strips detector for HL-LHC will employ a custom PCB (powerboard) for on-module DC-DC conversion, HV switching, and monitoring. Production of about 14100 of such PCBs with high reliability is a big challenge. This paper will present the production procedure and quality control (QC) testing system for the powerboards to be installed on ITk Strip barrel modules. During production, about 150 powerboards will be produced every week. Each powerboard will need to pass QC tests before they are assembled to module. The QC tests include thermal cycling between −35 °C and 40 °C, soak test (continuous running of DC-DC converter at high load at 20 °C), and basic functionality and characterization electrical tests of the low voltage (LV), high voltage (HV), and monitoring functions of the powerboard. A custom QC test system is described, which is based on a reusable PCB (active board) with all testing circuits, a one-time powerboard carrier card, and a Z-turn SoC board which hosts and runs the testing program. The production procedure and QC test system has been tested with 400 powerboards during pre-production, and the system has been proven ready for production with the desired testing program, speed, safety, and cost. Performance and typical failures of powerboards observed during the QC test of pre-production powerboards is also presented.

Threshold bounce — occupancy-dependent modulation of the discriminating threshold in silicon detectors

“…Modules form the base units of the ITk strip tracker [11,12]. Sensors for each module have a strip pitch of ∼70 μm and an active depth of 300 μm [13]; glued onto each sensor are flex-circuits known as hybrids -which instrument readout and control -and powerboards [14] -which instrument high-voltage and monitoring. Mounted onto each hybrid are ATLAS Binary Chip (ABC) ASICs, and each ABC performs the readout of 256 strip channels.…”