Abstract:

To improve the capacities and capabilities of microelectronic devices, 3D packaging is an attractive solution which can provide increased functional density at a decreased cost per function. However, classical cooling approaches, such as the use of a heat sink or cold plate on the topmost component, are gradually becoming incapable of maintaining a temperature below the manufacturer-prescribed maximum junction temperature in a 3D-packaged system since the heat is compounded between different die layers. Using micro- and nanofluidic systems to expose the die directly to a dielectric coolant, known as embedded cooling, can provide far lower junction-to-ambient thermal resistances. Further, employing two-phase heat transfer methods can facilitate ultrahigh heat removal to tackle die-level hotspots reaching 1 kW/cm² on each high-power tier in a 3D microelectronic device. This chapter presents a brief overview of microscale evaporative cooling technologies that can be implemented in embedded cooling methods capable of removing ultrahigh heat fluxes from 3D chips. The following two major topics are covered in this chapter: (1) device fabrication and integration, and (2) the characterization of thermal and operational performances through temperature measurement and flow visualization. Additionally, we emphasize research findings related to the use of hollow micropillars to create asymmetric evaporating droplet arrays. These droplet arrays can provide an ultrahigh cooling performance that exceeds the maximum heat flux reported earlier in the literature and reaches up to 14.70 kW/cm², with a heat transfer coefficient of 7 × 10⁶ W/m²K.

This book chapter can be accessed online here.