Enhancing the thermal conductivity of Kovar alloys without increasing their thermal expansion coefficient through the incorporation of an Ag network

Abstract

Kovar alloys are considered ideal candidates for electronic packaging due to their low thermal expansion coefficient (TEC). However, their low thermal conductivity (TC) significantly limits their broader application. Herein, Ag networks are incorporated into one of the Kovar alloys (4J50) to produce Ag/4J50 composites by electrolessly plating Ag onto 4J50 powders, followed by hot-pressed sintering. The continuous Ag network significantly increases the TC of the alloy without compromising its TEC. The TC of the Ag/4J50 composite containing 15 wt% Ag is enhanced to 56 W/(m·K), three times higher than 16.7 W/(m·K) of the 4J50 alloy. Meanwhile, its TEC at 20–500 ℃ is 10.2 × 10⁻⁶ K⁻¹, only slightly larger than 9.5 × 10⁻⁶ K⁻¹ of the alloy. Our findings provide a general method for significantly enhancing the TC of other Kovar alloys.