Thermal and Mechanical Analysis of Embedded Liquid Cooling with Microchannel and Pin-fin Structures

Embedded liquid cooling is expected to be a prominent thermal solution for high performance device with advanced packaging such as 3D ICs. It offers significantly high heat transfer performance due to its micro-structured cooling path in close proximity to the active device. In the concept of embedded liquid cooling, electrical interconnect between vertically stacked chip is enabled by Through Silicon Vias (TSV) integrated inside of the microchannel/pin-fin. Therefore, such microstructures play important role not only for the enhancement of heat dissipation but also for the reliability of the device. However, mechanical stress durability of delicate micro-structure becomes serious issues during package assembly process with temperature change. It is crucial to evaluate the mechanical characteristics of embedded cooling system while maintaining the high thermal performance. This paper presents the comprehensive study of two types of embedded cooling structures-microchannel and micro pin-fin, in terms of the thermomechanical and the thermo-hydraulic characteristics. Full-scale three-dimensional simulation model is developed for thermomechanical and Computational Fluid Dynamics (CFD) analysis to investigate the above-mentioned performances. For thermomechanical analysis, stress distribution and the warpage of the chip are evaluated for each cooling structures. Also, maximum stress on interconnection layer between chip-to-chip, as well as chip-to-substrate are investigated. For thermo-hydraulic analysis, characteristics such as thermal resistance, average chip temperature, pressure drop are compared. Based on the simulation results, novel design with hybrid structure of microchannel and pin-fin are proposed to achieve balanced performance for both mechanical and thermal aspects. By integrating the benefits of microchannel and pin-fin structures, it is numerically demonstrated to achieve high heat transfer and moderate pressure drop while maintaining sufficient mechanical reliability simultaneously.