Thermal Analysis of High Current Vertical Power Delivery Network with Embedded Microchannel Cooling

Advancements in high-performance computing (HPC) demand densified interconnect and assembly methods in power delivery networks (PDN). A challenge accordingly emerges with system-on-package (SoP) solutions using vertical power delivery networks (VPDNs), where heat dissipation from the die and the integrated voltage regulator (IVR) is a primary concern. This paper presents a numerical thermal analysis of two VPDN designs: distributed on- and in-interposer dual-phase multi-inductor hybrid (DPMIH) converters. Positioned vertically beneath the die for a 12 V-to-1 V single-stage, high-current power conversion using gallium nitride (GaN), these configurations are evaluated in scenarios with and without embedded microchannel cooling. With microchannel cooling, the analysis incorporates 103 microchannels, each 200 μm wide and 100 μm high, employing water as the working fluid. The aim is to maintain device temperatures below 90 °C during 1 kW power delivery to a monolithic 3D (M3D) die while minimizing pumping losses for microchannel cooling and ensuring total efficiency exceeds 80 % at a high current density. Numerical results show that without embedded microchannel cooling, the maximum system temperatures reach approximately 126.1 °C and 155.5 °C for on- and in-interposer configurations, respectively. Conversely, embedded microchannel cooling with a flow rate of 0.05 kg/s reduces maximum system temperatures to 54.6 °C and 74.6 °C for on- and in-interposer configurations, respectively. For maintaining temperatures just below the threshold of 90 °C, on-interposer conversion requires a flow rate over 0.015 kg/s, with pumping power consumption of at least 9.2 W, whereas in-interposer conversion demands a minimum flow rate of 0.025 kg/s, consuming 39.4 W of pumping power.