Enhancing electrical and mechanical properties of electrically conductive adhesives via synergistic effect of Ag@Cu particles and silver flakes

Conductive adhesives (ECAs) are critical for advanced electronic packaging, but the high cost of silver fillers limits their widespread application. This study presents a hybrid filler strategy combining silver-coated copper (Ag@Cu) nanoparticles with a low content of silver flakes to achieve high electrical conductivity at reduced cost. The Ag@Cu particles were synthesized via a two-step wet chemical reduction method, yielding a well-defined core–shell structure with a dense silver coating that prevents copper oxidation. A series of ECAs were prepared with silver flakes and Ag@Cu nanoparticles at a fixed total filler loading of 70%. The results demonstrate that the optimal silver flake content is 4%, at which the ECA exhibits the lowest volume resistivity of 3 × 10⁻ 4 Ω·cm. The prominent conductivity improvement stems from synergistic geometric regulation. Low loading silver flakes serve as conductive bridges to fill interparticle gaps and construct hybrid point-to-face contact, verified by SEM. The silver flake composite retains favorable shear strength and thixotropy for screen printing. A circuit test with printed films lit an LED, validating its feasibility for flexible circuits. This work develops low cost, high-performance ECAs using Ag@Cu nanoparticles and silver flakes, achieving a balance between excellent conductivity and reduced material cost.