Preparation and conductive mechanism study of Ag/PS core-shell particles for high-performance anisotropic conductive films

Anisotropic conductive films (ACFs) are promising materials for flexible electronics and wearable devices due to their excellent electrical conductivity and mechanical flexibility. However, simultaneously achieving high conductivity, superior mechanical properties, and long-term stability remains a critical challenge. In this study, polystyrene (PS) microspheres were surface-functionalized with acrylic acid to introduce carboxyl groups, enhancing surface reactivity for subsequent electroless silver plating. When the mass ratio of AgNO₃ to PS was 2:1, the prepared Ag/PS core–shell conductive particles exhibited a dense and continuous silver layer with an average thickness of ∼45 nm and an electrical resistivity of 2.03 × 10⁻³ Ω·cm, confirming their excellent conductivity. The epoxy resin-based ACFs prepared using these particles remained electrically insulating in both the X- and Y-directions while exhibiting a Z-axis resistivity of 6.67 × 10¹ Ω·cm after hot pressing. Furthermore, at a hot-pressing pressure of 2 MPa, the resistance was reduced to 1.2 Ω, while the shear strength reached a maximum of 1.8 MPa. The conductive mechanism of ACFs was systematically investigated by analyzing the morphological evolution of conductive particles under varying hot-pressing pressures. Additionally, the ACFs maintained stable electrical performance after 33 days of storage at 0 °C, meeting industrial transportation and storage requirements. This study provides valuable insights into the structural design and performance optimization of conductive fillers, contributing to the development of high-performance ACFs for microelectronic and flexible device applications.