Chip Cooling Research Articles

Effects of Aging on Macro Performance and Multiscale Structure Change of Highly Filled Elastomer Composites for Chip Cooling Investigated by Broadband Dielectric Spectroscopy

Effects of Aging on Macro Performance and Multiscale Structure Change of Highly Filled Elastomer Composites for Chip Cooling Investigated by Broadband Dielectric Spectroscopy

Multiphysics Simulation of a Novel Self-Adaptive Chip Cooling with a Temperature-Regulated Metal Pillar Array in Microfluidic Channels

Conventional liquid cooling techniques may provide effective chip cooling but at the expense of high pumping power consumption. Considering that there is dynamic heat load in practice, a self-adaptive cooling technique is desired to reduce operational costs while preserving inherent cooling effectiveness. In this work, a novel self-adaptive cooling strategy is presented to balance the thermal and flow efficiency in accordance with the dynamic thermal load, based on temperature-regulated movement of the metal pillar array in a microfluidic channel. With an illustrative device, the effectiveness of such a strategy is investigated using multiphysics modeling and simulation. As a case study, the device is considered to be initiated with a chip power of 5 W and an inlet coolant velocity of 0.3 m/s. It is shown that the temperature-regulated movement of the metal pillar heat sink will be activated rapidly and equilibrate within 30 s. Parts of the metal pillars immerse into the coolant flow, resulting in significantly improved heat transfer efficiency. The diminished thermal resistance leads to a reduction in chip temperature rise from 225 K (without structural adaptation) to 91.86 K (with structural adaption). Meanwhile, the immersion of metal pillars into the coolant also causes an increased flow resistance in the microfluidic channel (i.e., pressure drop increases from 859.27 Pa to 915.98 Pa). Nevertheless, the flow resistance decreases spontaneously when the working power of the chip decreases. Comprehensive simulation has demonstrated that the temperature-regulated structure works well under various conditions. Therefore, it is believed that the presented self-adaptive cooling strategy offers simple and cost-effective thermal management for modern electronics with dynamic heat fluxes.

Efficient Solutions for Electronic Chip Cooling: Multi-Objective Optimization Using Evolutionary Algorithms with Boron Nitride Nanotube-Based Nanofluid

Optimization algorithms have significantly evolved because of advancements in computational capacity. This increase aids in the availability of data to train various artificial intelligence models and can be used in optimizing solutions for electronic chip cooling. In the current study, such a microchannel heat sink (MCHS) is optimized using a Boron Nitride Nanotube (BNN)-based nanofluid as a coolant. Thermal resistance and pumping power are chosen as the objective functions, while geometric parameters such as the channel aspect and width ratio are used as the design variables. Multi-objective multiverse optimizer (MOMVO), an evolutionary algorithm, is used to optimize both objective functions, which are minimized simultaneously. The primary objective of this study is to study the applicability of such advanced multi-objective optimization algorithms, which have not previously been implemented for such a thermal design problem. Based on the study, it is found that the optimal results are obtained with a population size of only 50 and within 100 iterations. Using the MOMVO optimization, it is also observed that thermal resistance and pumping power do not vary significantly with respect to the channel aspect ratio, while pumping power varies linearly with the channel width ratio. An optimum thermal resistance of 0.0177 °C/W and pumping power of 10.65 W are obtained using the MOMVO algorithm.

Advanced Thermal Control Using Chip Cooling Laminate Chip (CCLC) with Finite Element Method for System-in-Package (SiP) Technology

This paper introduces a novel approach to address thermal management challenges in system-in-package (SiP) technology, which is a significant concern in various advanced technologies. The main objective is to assess the electrical and thermal performance of the SiP model by utilizing Chip Cooling Laminate Chip (CCLC) technology. To achieve this, we employed finite element method (FEM) analysis using COMSOL Multiphysics® and MATLAB® to compare the results of electrical and thermal SiP models with and without CCLC technology. The numerical simulations revealed that, as opposed to the traditional model, the temperature variation decreased significantly with a uniform temperature distribution when employing the CCLC technology. Additionally, the thermal conduction performance of the packaging system using CCLC demonstrated remarkable reliability and resolution with cost-effective micro-devices, particularly in micro-medicine applications. The analysis of the electrical and thermal models reported a maximum error between them of 1.15 ∘C.

Study on the Performance of a Y-Shaped Liquid Cooling Heat Sink Based on Constructal Law for Electronic Chip Cooling

Abstract The power of one rack in a data center can be greater than 3 kW, which is released within a relatively small area. However, most of the heat in a data center is released from the electronic chips. Thus, the energy consumption of the air-conditioning system in a data center will be significantly decreased if the heat released by the electronic chips can be reduced directly. Although liquid cooling heat sinks (LCHS) have been demonstrated as an effective way to resolve this problem, the application of LCHS is limited by the uneven cooling distribution on the surface of the electronic chips and the liquid leakage of the LCHS. The constructal law optimizes the design of the pipeline by introducing the freedom of deformation in the fluid geometry to obtain the optimal global performance. In this study, a novel Y-shaped liquid cooling heat sink (YLCHS) was proposed based on the constructal law, in which the cooling water enters the center of the heat sink through the inlet pipe and diffuses into the periphery through the internal Y-shaped microchannels. A numerical simulation was carried out to determine the cooling effect of the YLCHS. Compared to those of the conventional S-shaped liquid cooling heat sink (CSLCHS), the peak surface temperature and the average surface temperature of the electronic chip with YLCHS were decreased by 15.2 °C and 6.3 °C, respectively. Furthermore, the pressure loss of the electronic chip with YLCHS was also reduced by 63.0%.

Optimization of Microchannel Heat Sink with Rhombus Fractal-like Units for Electronic Chip Cooling

Abstract Microchannel heat sink is commonly used as a high-efficiency heat exchanger type in electronic microchips cooling, and the parallel microchannels arranged on the heat sink not only enhance heat transfer area but also result in large pumping power. In this paper, a novel structure of microchannel heat sink with rhombus fractal-like units is proposed for improve the overall performance, and a geometry optimization approach is developed for the design of the new microchannel heat sink. The validation of the geometry optimization approach is performed, and the results show that the predicted pumping power can describe 93% of the experimental data within the deviation limit of ± 5% and the mean deviation is 1.95%. Compared to the conventional parallel microchannel heat sink, the microchannel heat sink with rhombus fractal-like units may increase the COP by 7.9%-68.7% under the same constrains of external size, specified heat flux and maximum temperature limitation, which indicates the rhombus fractal-like units may effectively improve the efficiency of microchannel heat sinks.

Optimization of Converging and Diverging Microchannel Heat Sink for Electronic Chip Cooling

This article presents a steady-state 3-D conjugate heat transfer and single-phase liquid flow simulation in the microchannel heat sink (MCHs). The 3-D governing equations with boundary conditions are solved for a constant heat flux of 200 W/cm2, applied at the bottom surface of MCHs. An array of microchannels with three different cross-sections—uniform, converging, and diverging—are investigated for a fixed chip dimension of 20-mm length, 4-mm width, and 0.15-mm substrate thickness. This article aims to present a comparative analysis of the hydraulic and thermal performance of MCHs with three different cross-sections. Simulations are performed for volume flow rate and microchannel depth range of 20–140 mL/min and 0.25–1.25 mm, respectively, with silicon microchannel using water as the working fluid. Numerical simulations are performed using COMSOL Multiphysics 5.3. Comparative analysis shows that for a wide range of volume flow rate, diverging channels MCHs shows superior thermohydraulic performance. Furthermore, it is observed that with an increase in depth or aspect ratio of the channel, there is a significant reduction in pumping power requirement with some marginal reduction in thermal performance. Furthermore, to calculate the optimized channel dimensions for minimum thermal resistance and pressure drop, a MATLAB code was written. Based on the results, the optimized channel dimensions are identified. The work presented and discussed in this article is relevant and beneficial for designing compact MCHs for electronic cooling applications.

The Chip Cooling Model and Route Optimization with Digital Microfluidics

Using microfluidic technology to achieve integrated chip cooling is becoming a promising method to extend Moore law effective period. The thermal management is always critical for 3D integrated circuit design. Hot spots due to spatially non-uniform heat flux in integrated circuits can cause physical stress that further reduces reliability. The critical point for chip cooling is to use microfluidic cooling accurately on the hot spots. First, based on electro-wetting on dielectric, the paper presents an adaptive chip cooling technique using the digital microfluidics. Then, a two-plans 3D chip cooling model has been given with its working principle and characteristics. And single plan chip cooling model is presented, including its capacitance performance and models. Moreover, the dentate electrode is designed to achieve droplet continuing movement. Next, the ant colony optimization is adopted to get optimal route during electrode moving. Last, the experiments demonstrate the adaptive chip cooling technique proposed in this paper is effective and efficiency.

Experimental Study of Energy Saving Performances in Chip Cooling by using Heat Sink with Embedded Heat Pipe

With the rapid development of computer industry, the computer performance is seriously restricted by the energy consumption and heat dissipation of high heat flux chip. The increase in high density server racks makes the power supply and the heat dissipation more complex. Thus, it is necessary to optimize the computer chip cooling technology. In this study, heat pipe was used to enhance the cooling performance of CPU. Different forms of heat sink embedded with heat pipe were adopted, and the heat dissipation and energy saving performance were studied. Consequently, the cooling performance can be enhanced with the new cooling technology, and the energy consumption can also be reduced in order to make the CPU work at normal operation temperature, due to high efficiency heat dissipation technology.

Heat transfer and friction characteristics of the microfluidic heat sink with variously-shaped ribs for chip cooling.

This paper experimentally and numerically investigated the heat transfer and friction characteristics of microfluidic heat sinks with variously-shaped micro-ribs, i.e., rectangular, triangular and semicircular ribs. The micro-ribs were fabricated on the sidewalls of microfluidic channels by a surface-micromachining micro-electro-mechanical system (MEMS) process and used as turbulators to improve the heat transfer rate of the microfluidic heat sink. The results indicate that the utilizing of micro-ribs provides a better heat transfer rate, but also increases the pressure drop penalty for microchannels. Furthermore, the heat transfer and friction characteristics of the microchannels are strongly affected by the rib shape. In comparison, the triangular ribbed microchannel possesses the highest Nusselt number and friction factor among the three rib types.

Flow and Thermal Performance of a Water-Cooled Periodic Transversal Elliptical Microchannel Heat Sink for Chip Cooling.

Flow and thermal performance of transversal elliptical microchannels were investigated as a passive scheme to enhance the heat transfer performance of laminar fluid flow. The periodic transversal elliptical micro-channel is designed and its pressure drop and heat transfer characteristics in laminar flow are numerically investigated. Based on the comparison with a conventional straight micro- channel having rectangular cross section, it is found that periodic transversal elliptical microchannel not only has great potential to reduce pressure drop but also dramatically enhances heat transfer performance. In addition, when the Reynolds number equals to 192, the pressure drop of the transversal elliptical channel is 36.5% lower than that of the straight channel, while the average Nusselt number is 72.8% higher; this indicates that the overall thermal performance of the periodic transversal elliptical microchannel is superior to the conventional straight microchannel. It is suggested that such transversal elliptical microchannel are attractive candidates for cooling future electronic chips effectively with much lower pressure drop.

Numerical Investigation on Microelectronic Chip Cooling Using Multiple Orifice Synthetic Jet Actuator Based on Theory Field Synergism

Synthetic jet is applied to the field of heat and mass transfer, because the periodical suck and blow enhances forced convection heat transfer. A multiple orifice synthetic jet actuator (SJA) is designed for the cooling of microelectronic chips. By using fin, it can achieve higher effectiveness of heat transfer with a combination of active and passive scheme in heat dissipation. Numerical simulation of the flow field of the multiple orifice SJA is performed to analyze the mechanism of the heat dissipation. Based on the above work, numerical simulations presenting the effects of heat dissipation with different flat-to-orifice distances are performed in this study. The theory Field Synergism of the optimization of convection heat transfer is introduced to evaluate the effects of the parameters on heat transfer by comparing the magnitude of the integral value. The results verify that the larger the integral value is, the higher the heat transfer coefficient is. And there is an optimum impinging distance at which the synergy degree between velocity field and temperature gradient field reaches its peak and the heat transfer coefficient is the highest.

Flow and Heat Transfer Analysis of an Electro-Osmotic Flow Micropump for Chip Cooling

This paper reports theoretical and numerical analysis of fluid flow and heat transfer in a cascade electro-osmotic flow (EOF) micropump for chip cooling. A simple analytical model is developed to determine the temperature distribution in a two-dimensional (2D) single channel EOF micropump with forced convection due to a voltage difference between both ends. Numerical simulations are performed to determine the temperature distribution in the domain which is compared with that predicted by the model. A novel cascade EOF micropump with multiple microchannels in series and parallel and with an array of interdigitated electrodes along the flow direction is proposed. The simulations predict the maximum flow rate and pressure capability of one single stage of the micropump and the analytical model employs equivalent circuit theory to predict the total flow rate and back pressure. Each stage of the proposed micropump comprises sump and pump regions having opposing electric field directions. The various design parameters of the micropump includes the height of the pump and sump (h), number of stages (n), channel width (w), thickness of the channel wall or fin (r), and width ratio of the pump and sump (s:p) regions. Numerical simulations are performed to predict the effects of these design parameters on the pump performance which is compared with that predicted by the analytical model. The micropump is used for cooling cooling of an Intel® CoreTM i5 chip which produces a maximum heat of 95 W over an area of 3.75 × 3.75 cm. Based on the parametric studies a design for the cascade EOF micropump is proposed which provides a maximum flow rate of 14.16 ml/min and a maximum back pressure of 572.5 Pa to maintain a maximum chip temperature of 310.63 K.

Experimental and Numerical Study of Transient Electronic Chip Cooling by Liquid Flow in Microchannel Heat Sinks

Cooling of electronic chips has become a critical aspect in the development of electronic devices. Overheating may cause the malfunction or damage of electronics. The time needed for heat removal is particularly important in a wide range of electronic systems, such as switching circuits. Thus, it is important to characterize the transient behavior of the system and determine the response. Most studies in the literature have focused on steady-state circumstances and the transient effects have not been considered in the detail needed. In this article, an experimental system and a numerical model were developed to test the effects of different parameters and their influence on the transient electronic chip cooling by liquid flow in microchannel heat sinks. The temperature change with time of the system for different heat fluxes at different flow rates was determined, from which the response time is obtained. Three different configurations of multi-microchannel heat sinks were tested during the experiment. Numerical models were then developed to simulate the transient cooling for two of these configurations. A good agreement between the experimental data and numerical results showed that single-channel models are capable of simulating the thermal behavior of the entire heat sink by applying appropriate assumptions and boundary conditions. The experimental results can then be used to improve the numerical models and vice versa.

Computational Fluid Dynamics Assisted Control System Design With Applications to Central Processing Unit Chip Cooling

In this paper, a computational fluid dynamics (CFD) assisted control system design methodology has been described in detail. The entire design and evaluation procedure has been illustrated through a feedback control system synthesis for a central processing unit (CPU) chip cooling system. The design methodology starts with a full-scale CFD simulation of the nonlinear dynamic process to generate the input and output databases of the process. Using this data set, linear dynamic models around specified operating points are obtained using system identification techniques. Based on these models, one can design appropriate control systems to meet the required closed-loop control system specifications. To illustrate the effectiveness of this technique, it has been used to design a controller for a PC chip cooling system. In particular, the coupling issues between ‘real-time’ dynamic controllers with non real-time CFD simulation have been resolved. A physical experimental test bench based on a cooling system of a Pentium III CPU has been constructed. The feedback linear control systems designed by the proposed CFD approach have been evaluated experimentally for six CPU load conditions.

Thermal Transport in Graphene and its Application in Chip Cooling

Graphene, the latest isolated allotrope of carbon made of individual atomic sheets bound in two dimensions, shows many remarkable properties. Academic and industry research groups around the globe are carrying out theoretical and experimental studies to discover and investigate characteristics of graphene. Due to its outstanding properties, graphene has a potential to revolutionize technology. Particularly, graphene was found to be one of the best known heat conductors, thus it can be used in nanoelectronic and optoelectronic devices as a heat spreader component. It was also recently reported that graphene is an excellent conductor of heat with the room temperature thermal conductivity values on the order of or exceeding those of carbon nanotubes. In the experiment an indirect method of measuring G peak position of the Raman spectrum as a function of both the temperature of the graphene sample and the power of the heat source was used to compute the thermal conductivity. The sample in the experiment had rectangle geometry and the heat source was approximated as a hot line on the surface of the sample. The thermal conduction in graphene flakes was simulated using the finite element method with the help of COMSOL software package, which solves numerically the partial differential equations, in order to investigate how thermal transport is influenced by a surface geometry of the sample and geometries of the heat sources. We found that all mentioned factors impact heat propagation in different ways and have to be included in the experimental data extraction. The results of the simulations proved correctness of the experimental determination of the thermal conductivity in single layer graphene. Numerical procedure was also developed to simulate heat propagation in semiconductor device structures with graphene layers incorporated as heat spreaders. The simulation results showed that the incorporation of graphene and its multilayers with proper heat sinks can substantially lower the temperature of the chip. The developed simulation procedure can provide a necessary input for next experiments on heat conduction in graphene structures e.g., graphene multi-layers and graphene―heat sink structures and other device-level thermal management applications.

Analysis of Flow and Thermal Performance of a Water-Cooled Transversal Wavy Microchannel Heat Sink for Chip Cooling

With the increasing output power of the integrated circuit chips, the heat flux involved is being accordingly increased. In such situation, the air has almost reached its limit of cooling capacity, and thus the liquid cooling technology incorporating microchannel heat sinks is desired to cool the electronic chips in order to remove more heat loads. However, these microchannel heat sinks are often designed to be straight with rectangular cross section. In this study, on the basis of a straight microchannel having rectangular cross section, a kind of transversal wavy microchannel is designed and then the laminar flow and heat transfer are investigated numerically. It is shown that for removing the identical load, the transversal wavy microchannel has great potential to reduce pressure drop compared to the straight microchannel, especially for higher wave amplitude at the same Reynolds number, indicating the overall thermal performance of the transversal wavy microchannel is superior to the traditional straight rectangular microchannel. It is suggested such wavy microchannel can be used to cool chips effectively with much smaller pressure drop penalty.

A Compact Loop Heat Pipe With Flat Square Evaporator for High Power Chip Cooling

In this paper, systematic experimental and theoretical investigations were carried out on a copper-water compact loop heat pipe with a flat square evaporator having a bottom area of 30 mm × 30 mm. Wick structure inside the evaporator was made of fine copper powder with carefully designed vapor removal channels sintered directly on the substrate. In addition, the design and fabrication of a 120 mm air-cooled condenser was given adequate consideration. From the experimental tests, it is found that such a small loop heat pipe can manage a heat load of more than 600 W, and no dry-out occurs. In the favorable vertical configuration, with an air velocity of 2.8 m/s, this compact loop heat pipe has a thermal resistance as low as 0.042°C/W, with a corresponding evaporator thermal resistance as low as 0.018°C/W . As well, the theoretical analysis agrees in principle with the experimental data.

Thermal Performances Analysis of Microelectronic Chip Cooling System with Thermoelectric Components

The microelectronic chip thermoelectric cooling equipment and its test system have been developed for the deficiency of the conventional cooling technologies in this paper. The thermal resistance analysis model was applied in research the heat transfer process of the microelectronic chip cooling system and its characteristics. The results show that: When the thermoelectric cooling (TEC) system is in normal operating condition,the Peltier effect is the dominant role in the thermoelectric cooling process despite the opposite actions of the Joule and Fourier effects. The thermal resistance of TEC, which is Q2, decreases when the operating current (I) increases. For the different chip power, there is an optimum current (Iopt) making the interface thermal resistance between chip and TEC minimum (Q1). Q1can obtain the minimum 0.465°C·W-1 when the chip power is 25W and Iopt is 2.4A. The total thermal resistance (Qtotal) firstly decreases and then increases with the increase of operating current. There is an optimum current which allows the total thermal resistance is smallest. Qtotal may obtain the minimum value 0.672°C·W-1 when the chip power is 25W and Iopt is 2.4A. Furthermore, Qtotal Iopt both increase by the chip power.

Evaluation of Jet Impingement, Spray and Microchannel Chip Cooling Options for High Heat Flux Removal

Thermal management for high heat flux removal from microelectronic chips is gaining critical importance in many earth-based and space-based systems. Heat fluxes greater than 1 MW/m2 (100 W/cm2) have already been realized in high-end server applications, while cooling needs in next generation chips and advanced systems such as high-power electronics and electrical systems, pulsed power weapons systems, solid-state sensors, and phased-array radars are expected to reach 5–10 MW/m2 (500–1000 W/cm2). After evaluating the contributions from different thermal resistances in the chip-to-ambient thermal path, this paper presents a critical review and research recommendations for three prominent contending technologies: jet impingement, spray cooling, and microchannel heat sinks.