Low‐Temperature Solidifiable Liquid Metal with Ultrahigh Thermal Conductivity Enabled by Spontaneous Phase Transition for Electronics’ Safety and Long‐Life Cooling

Gallium‐based liquid metals have displayed many advantages as a thermal interface material for high‐power electronic devices. However, due to their excellent rheological property, liquid metals do carry risks for electronic systems, including the possibility of short circuit or even failure. For this problem, a low‐temperature solidifiable liquid‐metal EGaInSn/Cu composite is proposed, and the matter state of this composite can transform from liquid to solid spontaneously even at room temperature. Subsequently, the liquid–solid transition behavior and phase composition evolution of liquid‐metal composites during solidification are investigated, and it is found that the solidifying reaction is triggered by the formation of CuGa₂ intermetallic compounds and the precipitation of In₃Sn solid solutions. Moreover, this study confirms that the obtained composite with only a 36% volume ratio of copper fillers can achieve an ultrahigh thermal conductivity of 86.7 W (m K)⁻¹, which is far greater than that of other analogous liquid‐metal composites. More importantly, the mechanical and thermal properties of this material after solidification have always maintained steady in the thermal cycling test. It demonstrates that the low‐temperature solidifiable liquid metal can satisfy the needs of electronics’ safety and long‐life cooling application.