Investigating the 3-Dimensional Structure of Metallic Filler Particles in Electrically Conductive Adhesives

Electrically conductive adhesives (ECAs) are emerging interconnection materials whose performance hinges on a continuous three‑dimensional metal filler network. Understanding the 3D microstructure is essential for predicting percolation, optimizing filler loading, and ensuring reliable, low‑temperature interconnects. 2D analyses miss critical connectivity and distribution details that govern current paths. We present a 3D characterization of the metallic filler network in ECAs using focused ion beam–scanning electron microscopy (FIB-SEM) slice-and-view. The study aims to illuminate the 3D microstructure, enabling prediction of percolation, optimization of filler loading, and assessment of reliable, low-temperature interconnects. A voxel-based reconstruction from aligned 2D slices assigns phase labels (metal vs. resin) and color values to visualize the network and its interfaces, allowing explicit identification of connected and non-connected metal filler particles, which is crucial because macroscopic current conduction relies on a continuous metal network bridging 2 contact interfaces. The metal filler fraction in the resin matrix for 3D (volume) and for 2D (slice) data can be tested and showed a comparable value for the apparent ECA. Variations were found on microscopic scales which average out fast. Segmentation distinguishes connected clusters from isolated fillers, estimate in-plane needed current distances, noting that non-connected particles near sample edges can be artifacts that must be excluded from interpretation.