Interfacial fracture behavior of polyimide/copper in RDL structures for advanced electronic packaging

Polyimide (PI) is widely used in the fabrication of redistribution layers (RDL) for fan-out packaging due to its excellent mechanical properties. However, the miniaturization of electronic components has posed numerous new challenges to the electronics manufacturing industry. As an important part for signal redistribution and structure support, the evaluation of the structural stability of RDL has become an urgent issue in advanced packaging. In this study, PI/Cu lap joint specimens were used to investigate the mechanical properties and interfacial adhesion performance of PI under different curing conditions. Through lap shear tests, scanning electron microscopy (SEM) analysis, and finite element method (FEM) simulation, the applicability of PI in packaging structures was systematically analyzed. The results show that PI sintered at high temperature exhibits good structural stability and is less prone to crack formation during deformation. But it has relatively low fracture toughness and strength, and tends to delaminate from Cu, making it unsuitable for structures subjected to large deformations. In contrast, PI cured at room temperature demonstrates higher fracture strength and better interfacial adhesion, as well as greater deformability, but is more prone to crack initiation, making it less suitable for structures under long-term loading. This study not only reveals the influence mechanism of curing conditions on the structural properties and adhesion performance of PI, but also provides theoretical support and research guidance for the manufacturing of RDL and the optimization of PI forming processes in advanced packaging.