Description
Within the CERN EP R&D programme and the DRD3 collaboration, new hybridisation approaches are being developed for pixel detectors, aiming at rapid prototyping while ensuring interconnection reliability and scalability. To adapt the pad topography of the chips, an in-house Electroless Nickel–Gold (ENIG) bumping process has been developed at the single-die level, providing the flexibility to accommodate the diversity of chip designs and integration constraints. Different hybridisation approaches are currently under investigation to address the diversity of chip designs and integration constraints. One such approach is anisotropic conductive adhesive (ACA) bonding, in which conductive microparticles dispersed in an adhesive film (ACF) or paste (ACP) provide both electrical and mechanical connections between the sensor and the ASIC through thermocompression using a flip-chip bonder. Another technique under study involves the use of gold stud bumps deposited on the chip pads for electrical interconnection, combined with an epoxy adhesive to ensure mechanical bonding. This work presents recent developments in the ENIG bumping process and flip-chip bonding techniques. Results obtained from daisy-chain test structures, as well as from assemblies based on functional ASICs and sensors, demonstrate promising performance. The reliability of the interconnections has been evaluated through environmental testing in a climate chamber.