Liquid Nanodielectrics for Heat Transfer in 3D Heterogeneous Microsystems: A Review

Three-dimensional heterogeneous integrated (3DHI) circuits can be made by stacking layers of microsystems one over the other and making the connection shorter, which allows for less power consumption since the DC losses will be very low over shorter distances. This novel and innovative packing technique of the microsystems was considered revolutionary in achieving 100% packing efficiency, compactness, and low power consumption. However, the thermal management issues that are imminent to the internal processing components in the 3DHI limit the widespread implementation of this technology. Although the two-phase heat transfer significantly enhances the heat removal from the micro and nano-sized passages, the complexity arises when the coolant comes in direct contact with the electrically active components. The best way to counter this problem is by using fluids that have dielectric properties. However, these dielectric liquids are invariably known for their poorer thermal conductivity and physical properties than water. So, the thermal properties of these liquids need to be enhanced to be used in place of the existing coolants. One way to do that is by adding nanoparticles, which have been proven to enhance the thermal conductivity of fluids significantly. Using nanodielectric fluids (NDFs) as a coolant in the 3DHI of microsystems can be a convincing alternative to the existing thermal management techniques that use water (or other electrically conducting liquids) as a coolant. This paper critically reviews the existing NDFs studied in power transformers to provide enhanced heat dissipation and dielectric strength to propose potential NDF options for 3DHI systems. This can be a transformative and innovative approach to thermal management in microsystems.