A High Thermal Conductivity Kovar Alloy via Chemical Tailoring

Achieving high thermal conductivity while maintaining thermal expansion compatibility is crucial for efficient heat dissipation and long-term reliability in electronic devices; yet, it remains rare in metallic systems. Here, through chemical tailoring in high-symmetry face-centered cubic Fe–Ni alloys, we design a Fe55.6Ni27.3Cu17.1 ternary alloy to achieve both low thermal expansion (αl = 5.37 × 10–6 K–1, 112–492 K) and high thermal conductivity (18.24 W·m–1·K–1 at room temperature). Cu substitution shifts the Fe majority-spin d band top-edge toward the Fermi level, strengthening the magneto-volume effect and reducing thermal expansion, while simultaneously increasing the s band electron density at the Fermi level to enhance free-electron transport and boost thermal conductivity. These results highlight that chemical tailoring provides an effective strategy for enhancing thermal and magnetic properties, offering both a theoretical foundation and a practical pathway for designing high-performance electronic packaging alloys.