The proposed topic of the thesis is related to ultra-thin PCBs, tailored for applications where intricate designs demand cutting-edge space optimization, such as in satellite payloads or large-scale scientific experiments. In detector systems, minimizing PCB thickness is often necessary to reduce dead material in the active region, where the sensor is highly sensitive to any perturbations. This is crucial for both space-based and ground-based scientific experiments.

The PhD candidate will undertake a comprehensive study encompassing (i) design and simulation, (ii) manufacturing and (iii) experimental campaigns for the high-frequency characterization (up to 30 GHz) of custom Printed Circuit Boards (PCBs) and various bonding schemes to chip-to-flex interconnections.

Ultra-thin PCBs will either be manufactured in FBK via custom patent-pending techniques or by commercial standards to be used as a benchmark. The candidate will design and simulate the PCB stack, including differential pairs and controlled impedance routing.

Full process control during manufacturing will enhance the model development, allowing for the identification of specific contributions from the macroscopic geometric features (such as the shape of the metal leads) to microscopic elements like lead roughness, grain size (see Mayadas-Shatzkes model) and bonding types.

The study will explore various bonding techniques, including wire-bonding, TAB bonding and bump bonding for 3D integration. These techniques differ in materials and bonding geometries, affecting impedance and signal insertion loss. Thus, developing a computational model (e.g.using Comsol) and validating it with experimental measurements is critical for selecting the appropriate electronics design.

By validating the simulated data with VNA measurements, the investigation aims to deepen the understanding on how each factor included in the model influences the signal integrity of PCBs in high-frequency applications. Those insights will inform the design of advanced assemblies for scientific detectors in future experiments at CERN or in space missions conducted by ASI, ESA and NASA.