Speaker
Description
This work presents a packaging concept enabling planar and curved chip integration with a minimized material budget. Building on foundational techniques introduced two decades ago for the ALICE ITS1 and the STAR tracker, this approach uses flexible cables made of aluminum and polyimide. Additionally, instead of conventional wire bonding, which poses limitations in handling and bending of detector assemblies, single-point Tape Automated Bonding (spTAB) is employed. By creating openings in the polyimide layer, free-standing aluminum traces of the cables are directly bonded to the sensor, eliminating the need for additional wire connections.
Extending this concept, the entire printed circuit board (PCB) is rendered flexible by stacking three layers of 20 μm thick aluminum traces and 25 μm thick polyimide. These layers include a ground plane, a signal layer (supporting both digital and analog signals), and a bonding layer (replacing wire bonding). SpTAB is utilized both for inter-layer connections and for sensor bonding. In a prototype implementation, an ALPIDE chip is successfully bonded using this method, demonstrating an ultralight packaging solution that could be readily adapted for future designs needing flexible chip or compact electronics integrations. All fabrication and assembly steps took place at Fondazione Bruno Kessler, and the workflow will be outlined to illustrate the feasibility of this approach for upcoming experimental applications. Production results and characterization of the assembled device will be presented. Additionally, the testing setup and the outcome of the initial readout tests will also be showcased. Finally, we will quantify the flexibility of the complete assembly (chip plus PCB) and discuss how the spTAB connections behave under bending radii of only a few centimeters.
