Development of an open-source FEM simulation tool for aluminum PCBs based on PALACE-FEM

Aluminum PCBs are widely used in particle physics experiments because they offer a significantly lower material budget than traditional copper-based solutions (X0: Al ≈ 8.9 cm, Cu ≈ 1.43 cm). This approach has already been adopted in several major experiments, such as ALICE ITS1/ITS2 and STAR. The integration of low material budget Kapton-aluminum PCBs with MAPS sensors is now being considered for next-generation detector systems, including IDEA (FCC-ee), ALICE3, and ePIC. Motivated by the growing interest within the community, Fondazione Bruno Kessler (FBK) started developing an innovative approach to Kapton-aluminum PCBs manufacturing. This effort has produced the first results, demonstrating its feasibility through the successful interconnection of an ALPIDE chip. The resulting PCB achieves an overall material budget of approximately 0.05%, comparable to the sensor X0. To validate the electrical properties of these flexible PCBs, a dedicated simulation environment is required. For this reason, the goal of this work is to develop a comprehensive simulation tool capable of incorporating realistic PCB properties derived from material-characterization techniques such as resistivity analysis or precise cross-section measurements with Plasma Focused Ion Beam (PFIB). This work focuses on Geant4 simulations and on Finite Element Method (FEM) simulations performed using the open-source Palace framework to model the flexible PCB structures with high precision. In the initial phase, different mesh sizes and refinement parameters were varied to identify the optimal trade-off between computational cost and solution accuracy, with simulation results validated against IPC-2251 standards.