Hierarchically packed liquid epoxy composites with ultralow CTE and viscosity for high-performance wafer-level...

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Liquid epoxy molding compounds (LMCs) are crucial for electronic packaging but face challenges in balancing processability, mechanical reliability, and dimensional stability.
• Achieving high filler loadings in LMCs often leads to poor flow properties and compromised performance.

Purpose of the Study:

• To develop a synergistic design strategy for highly filled LMCs that overcomes trade-offs between processability, mechanical reliability, and dimensional stability.
• To achieve ultra-high filler loading while maintaining excellent rheological and mechanical properties.

Main Methods:

• Integrated matrix optimization using a ternary epoxy system.
• Multiscale hierarchical packing with bimodal fused silica and core-shell rubber (CSR) nanoparticles.
• Interfacial engineering via epoxy-based surface functionalization to reduce viscosity.

Main Results:

• Achieved ultra-high filler loading of 87 wt% (78.5 vol%) with a trimodal particle architecture.
• Developed a highly flowable suspension with exceptionally low viscosity (~250 Pa s) at high solid loadings.
• Resulting LMC exhibits a low coefficient of thermal expansion (CTE) of 8.20 ppm °C⁻¹, high glass transition temperature (Tg) (~170 °C), and superior flexural strength (~150 MPa).

Conclusions:

• The hierarchical-interfacial approach successfully addresses the inherent trade-offs in highly filled LMCs.
• This strategy provides a scalable blueprint for next-generation thermoset composites for advanced electronic packaging.
• The developed LMC demonstrates uniform, low-warpage wafer-level molding with robust hydrothermal reliability.