Thermal Management of Three-Dimensional Chips and Monolithic Integrated Circuits Using Phase Change Materials–Si/Cu Composites

Abstract The increasing demand for high-performance computing has accelerated the development of three-dimensional integrated circuits (3DICs), which offer enhanced performance but pose significant thermal challenges due to greater heat flux and more complex thermal pathways. This study explores the feasibility of phase change material (PCM)–Si/Cu composites for transient thermal management in 3DICs. To validate its effectiveness, we fabricated, characterized, and evaluated the PCM–Si pin-fin composites (a size of 50 × 50 μm2, a pitch of 100 μm, and a height of 150 μm). A custom-built experimental setup enabled simultaneous electrothermal, infrared (IR), and high-speed optical imaging, allowing in-depth quantitative analysis of phase transition dynamics under pulsed heat flux conditions. The results confirmed that PCM–composite systems are particularly effective for short-duration heat pulses, well before reaching steady-state conditions, achieving up to a ∼20% reduction in peak junction temperature (e.g., from ∼88 °C to ∼71 °C in representative tests). 3D finite-element simulations revealed that most of the vertical heat flow is conducted through the high-conductivity scaffold (Si pin fins), while lateral conduction from the Si pin fins into the PCM enables efficient utilization of latent heat during rapid transients, effectively buffering temperature spikes. The fundamental timescale-dependent behavior and phase change dynamics observed in this work are expected to apply to other PCM-enhanced cooling systems with a high-conductivity scaffold, particularly in applications with high-frequency thermal cycling over the PCM's phase change temperature, although specific timescales will depend on the material properties, geometry, and operating conditions. The present work provides a framework for development of PCM–copper nanowire (CuNW) composite thermal interface materials (TIMs) with the capability to suppress temperature spikes in timescales < 1 ms. To this end, we have also demonstrated the infiltration process for phase change material into the CuNWs matrix.