Micro-Nanostructured Aluminum Island Reinforcement of SLM AlSi10Mg/PI Heterogeneous Interfaces: Cohesive Zone Modeling and Experimental Validation

This paper addresses the issue of heterogeneous interface reinforcement between SLM-AlSi10Mg substrates and polyimide (PI) insulation layers. Micro-nanostructured aluminum islands are constructed on the AlSi10Mg surface via chemical etching, followed by PI coating curing to form a typical Al/PI interface. Based on a three-dimensional digital reconstruction model and cohesive zone modeling (CZM) theory, combined with parametric finite element simulations, the effects of interface material toughness and microstructural geometric parameters (including aluminum island depth Z and out-of-plane aspect ratio AR_out) on the mechanical behavior of the interface are systematically investigated. The simulation accuracy and the representativeness of the simulation model's geometric region are confirmed through mesh independence and representative volume element (RVE) convergence tests. Results show that as the interface material's tangential toughness increases, the interface tensile strength grows exponentially and transitions from brittle fracture to ductile failure. Increasing the interface material's normal toughness, however, reduces the interface tensile strength due to increased stress concentration at the top of the aluminum islands as dt increases. Increasing the aluminum island depth significantly enhances the mechanical interlocking effect; when the interface microstructure is slender and deep with an AR_out of 0.5, the interface strength can be increased by 21 times compared to that of a smooth interface. The measured interface strengths for smooth and 1-μm-deep aluminum island structures are 2.52 MPa and 34.03 MPa, respectively, while the simulated values are approximately 0.75 MPa and 15 MPa. The force-displacement curves obtained from the simulation match the measured interface failure modes, verifying the effectiveness of the simulation model. This model accurately captures the reinforcement mechanisms of micro-nano interface structures and provides theoretical guidance for optimizing heterogeneous interface parameters and designing highly reliable packaging.