REPORT SUBJECT RESEARCH METHOD TOPIC MICRO CHANNEL

MINISTRY OF EDUCATION AND TRAINING HCMC UNIVERSITY OF TECHNOLOGY AND EDUCATION REPORT SUBJECT: RESEARCH METHOD TOPIC: MICRO-CHANNEL Lecturer: PhD Dang Hung Son Group 3: DINH THE DUY 20147151 PHAN HOANG BUU DAO QUOC DUY LY TU CO download by : skknchat@gmail.com 20147150 LECTURER REVIEW ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… …………………………………………………………………………………………… .…………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… …………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… …………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… 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studies ( page 6-8 ) 20 ) download by : skknchat@gmail.com HEAT TRANSFER SIMULATION FOR THERMAL MANAGEMENT OF ELECTRONIC COMPONENTS Đinh Thế Duy Phan Hoàng Bửu Đào Quốc Duy Lý Tự Cơ Ho Chi Minh City University of Technology and Education Viet Nam Faculty of High Quality, No Vo Van Ngan Street, Linh Chieu Ward, Thu Duc District, Ho Chi Minh City, Vietnam ABSTRACT This research is to introduce the electronics design workflow and show the problem of heat transfer for electronic devices Physical, economic, environmental, ergonomic or performance issue all have a big influence on heat transfer Engineering knowledge achievements and their relationship with a PLM platform are schematically discussed The most common heat transfer solvers and the peculiarities for the electronic are presented The concept of athesehis is presented through two examples First, an example of natural convection transfer for a heat sink The second study was an experimental forced-convection steady-state cooling setup Experimental results will be presented in the report Keywords: Electronics, design, cooling, heat transfer, knowledge, FEM, CFD download by : skknchat@gmail.com Introduction The mechanism of heat transfer in electronics is very complex The multi-physics aspect can be divided into three domains: the electric domain, the thermal domain, and the fluid one Heat is generated in most electronic components devices with moderate cooling capacity are cooled by fans liquid can also be used to cool them It is necessary to take care of the temperature of electronic devices to prolong their life and performance Products are getting smaller and smaller, demand is increasing, manufacturer standards are constantly improving, and manufacturers have to keep up the pace Radiator with heat pipe combination Heat sinks that combine heat pipes, micro-channels with highly thermally conductive materials can replace conventional coolers The economical aspect can turn into concern as the final products become expensive and their manufacturers are no longer competitive All design decisions for an electronic device are made only after the cooling problem for that device has been resolved Therefore, heat transfer is a very important issue in the design of electronic components Numerical 3D optimization of a heat sink base, Computational Fluid Dynamic (CFD), combining numerical and analytical temperature approximation All these papers describe specific solutions for particular cases Important product information and the relationship with Product Life Cycle Management (PLM) solutions are also discussed These examples contain theoretical and experimental solutions that prove the accuracy of the presented concepts Problem statement In the field of electronics, competitiveness is a key factor to assure an optimal product price in respect to actual standards Design engineers face multiple challenges in order to take the right decisions Optimal electronics are designed with the least number of components, placed on an optimal Printed Circuit Board (PCB) layout and assembled in an ergonomic casing The engineering knowledge is stored at PLM level and used further to automate simulation tasks, reuse models and share results The conceptual design is tested using Electronic Design Automation software The exterior and interior 3D assembly is completed by means of Computer Aided Design (CAD) software Optimal thermal assessments require a combination of analytical solutions, empirical analysis and thermal modeling, using all available tools to support each other A wide range of heat transfer solvers are available Thus, numerical solutions are more common because complex parameters are not required Two types of commercial numerical heat transfer solvers are available: the Finite Element Method (FEM) and the CFD solver 2.1 FEM Solvers Thermal analysis is used to determine the temperature distribution and the other heat transfer computations in a body: download by : skknchat@gmail.com the quantity of heat exchanged, thermal gradient and heat flux As the structural response is influenced by the thermal field, coupled thermal-structural analysis are performed to describe the stress state due to thermal expansion or contraction In structural FEM based software, heat is transferred by conduction, convection or through radiation The major disadvantage of the FEM thermal analysis is the size of the model and the computation time 2.2 Computational Fluid Dynamics Simulating real flow by numerical solutions of the governing equations Thermal management can be simulated using the CFD Solvers instead of approximating convection film coefficients as FEM software The major advantage on the FEM solution is the dedicated CFD pre and postprocessors available for electronics Simulation capabilities are expanded due to extended material libraries, components and Integrated Circuit (IC) package databases, multi-layer PCB configurators, thermal interface materials and others 2.3 Electronic Design Automation The circuit diagram of the assembly is created using Electronic Design Automation software for circuit evaluation and simulation purposes in the electrical domain The behavior of the current is captured and its transient flow can be described allowing all heat data to be estimated 3D CAD files independent or with the use of third-party tools, such as macros and addons 2.4 Heat Transfer Calculator The behavior of the electronic components can be used to compute 2D surface heat flow on 3D internal heat generation for components and printed circuits Due to the complexity of the heat flow mechanism in electronics (i.e switching circuits, power losses, thermal characteristics, junction temperature, joule heating) a complete physic description is still not available Therefore, methods of computing thermal characterization parameters are based on simplified assumptions a 2.5 Computer Aided Design Not all Electronic Design Automation applications have CAD generation features or extended component libraries (i.e complex heat sinks, heat pipes, blowers, fans, specific connectors).Therefore, in order to complete the product assembly, a CAD system is required A final layout is proposed, than minor design changes are considered For example, passive components can be placed in the vicinity of active components to act as heat exchangers Also, small heat sinks can be positioned on the PCB under the download by : skknchat@gmail.com active components, to enhance the thermal behavior around hot spots This is only a preliminary design scenario where the 3D assembly is parameterized 2.6 Heat Transfer Solvers Heat transfer solvers are used to predict the temperature of the components and parts within an assembly The central role of the heat transfer code capability of such software to identify any issues Both hot spots within the PCB temperature distributions that exceed operational limits can be visualized The choice of the heat ware ranges from simple analytical code numerical solvers Results from the heat transfer to decide if the design is optimal or an optimization scenario has to be considered The concern of electronics heat transfer computer is that of the active components and their cooling components (resistors, transistors, integrated circuits transformers) Theoretical approach The equations for conductive heat transfer are described by: where represents the specific heat matrix, time derivative of the nodal temperatures, - thermal conductivity matrix, and - the effective nodal heat flow vector The primary unknown values are the nodal temperatures Other thermal parameters can be computed based on the nodal temperatures There are two types of FEM thermal analysis: steady-state and transient thermal analysis 3.1 Steady-state thermal analysis Steady-state thermal analysis is used to determine the temperature distribution in a structure at thermal equilibrium Steady-state solvers assume that the loaded body instantaneously develops an internal field variable distribution to equilibrate the applied loads The analysis is generally non-linear because the material properties are temperature dependent The governing equations for a non-linear regime are: where i represents the iteration step number The first iteration is used to solve the initial temperature conditions and the solution proceeds to the next iteration until the result convergence is achieved The necessary number of iterations for a precise solution depends on the non-linearity of the problem For solving the non-linear problem NewtonRaphson algorithm is used 3.2 Transient thermal analysis This type of analysis is used to determine the temperature distribution within a structure as a function of time, to distribution within a structure as a function of time, to predict the rates of the heat transfer, or the heat stored in the system The transient thermal analysis download by : skknchat@gmail.com assumes the evolution of a new field variable distribution from a set of initial conditions via a set of transition states, evolving through time Because most of the thermal phenomena have a transient evolution, this is the most common type of thermal simulation Material properties for a transient thermal analysis are: the density, the thermal conductivity and the specific heat The last characteristic is used to consider the effect of the stored heat: where: is the specific heat matrix and matrix of the thermal conductivity Loads are functions of time The effects of numerical integration are activated using the Crank-Nicholson, Euler and Galerkin or Backward stiffness methods When the solution is done, post-processing of the temperature evolution in time can be presented as tables, graphs or contour plots 3.3 CFD thermal analysis The CFD (Computational Fluid Dynamics) simulation solves the conservation equations for mass and momentum For flows involving heat transfer, an additional equation for energy conservation is required The equation for mass conservation, or the continuity equation, can be written in a general form as follows : where is the fluid density, - speed vector, and source mass The conservation of momentum in an inertial reference frame is described by where is the static pressure, external body forces Also, stress tensor, gravitational body force, and - contains other model-dependent source terms The stress tensor is given by where is the molecular viscosity, I - unit tensor, and the second term on the right hand side represents the effect of volume dilation For the heat transfer, the energy equation is solved in the following form: download by : skknchat@gmail.com where is the effective conductivity, is the turbulent thermal conductivity, defined according to the turbulence used model, and - the diffusion flux of species The first three terms on the right-hand side of Eq represent the energy transfer due to conduction species diffusion, and viscous dissipation, respectively includes any other volumetric heat sources Additional transport equations are also solved for turbulent flow 4, CASE STUDIES 4.1 Transient Thermal Analysis for Heat Sink performance evaluation In this first example, the transient temperature behavior of natural convection cooled electronics was simulated using a FEM transient thermal analysis 4.1.1 Simulation model setup: The model comprises a single layer FR-4 Epoxy board that has been attached two IC silicon based chips, cooled by natural convection using a fined aluminum alloy heat sink this simulation is to study the temperature distribution within the heat sink for a transient heat flow, such performance of the cooling solution can be evaluated The simulation requires the definition of three domains: electrical domain (current flow constraints within the circuit), thermal domain (heat generated due to the cu rent flow) and fluid domain (stagnant air heat transfer between the heat sink and the exterior) The simulation domains and parameters are described in the below Fig Non-linear IC heat cycles used in the simulation Domain Thermal domain Fluid domain Results Parameters Active component heat flow [W] Reference temperature [°C] Stagnant air natural convection cases [W/m2°C] Transient nodal temperatures [°C] Non-linear (Fig 3) 22 7.151 (Fig 5) Fig Non-linear IC heat cycles used in the simulation Fig Heat sink temperature distribution download by : skknchat@gmail.com 4.1.2 Results and discussions: After completing the solution, time-temperature distributions graph (Fig 4) and the nodal temperatures for certain analysis time steps were processed to evaluate the performance of the heat sink The time-temperature graph shows three distinct regions: a linear temperature growth region and two parabolic ones, that describe the response of the heat sink after conduction is achieved The temperature non-uniformity is clearly depicted as the heat remains concentrated at the bottom face of the heat sink, while the fins remain essentially at the reference temperature 4.2 Steady State forced convection cooling analysis First of all, general remarks have to be done regarding Figure In most cases, the heat flow of the active electronic components is non-linear However, due to the specific heat of each material found in the path of the thermal conduction, a steady-state temperature will be achieved for the non-linear heat flow that has a constant behavior in time Solving the transient CFD heat transfer problem can generate a black-box behavior of the product Further, specific convergence guidelines for transient CFD problems are not available, because the accuracy of the results relays most on the experience of the analyst Moreover, solver output files become large and the time required to achieve a solution increases dramatically 4.2.1 Simulation model setup: In this second study ANSYS ICEPAK pre and post processors, together with ANSYS FLUENT were used to simulate a steady-state forced convection cooling problem The active components were two MOSFETS installed on two aluminum heat sinks with horizontal fins (Fig 6) An exterior circuit comprising four resistors for each MOSFET caused the active components to generate a constant level of heat Cooling is achieved by an axially Installed fan as the air flows from the case back (called inlet) to the front (outlet) Two precision LM-35 temperature sensors were installed in different positions on the heat sinks and using an external micro-controller, the temperature was measured considering the time increment, until the steady-state temperate is achieved The experiment took place in three stages: circuit power ‒ ON; transient temperature monitoring; ////Steady state temperature achieved Probe Experimental steady state CFD Error ‒ download by : skknchat@gmail.com Experimental and simulation values temperature (°C) T1 T2 36.1°C 41.9°C steady state temperature (°C) 36.207°C 41.36°C experimental vs simulation temperatures 0.27% 1.45% Results and discussions: The processed results were the temperatures of the components and the pressure In order to check the accuracy of the results, experiments were performed to determine the steady-state temperature (Fig 14) The evolution of the transient temperature during time was read by connecting two temperature sensors to an external Data Acquisition Board Using a PC and MATLAB software, a code was written to read the temperature from the sensors (Fig 15) The experiment ended when the steady-state temperatures were reached Both and sensors were monitored These temperatures were compared with the corresponding values of two temperature probes, placed in the CFD model at the same coordinates, matching the surface contact be- tween the heat sink and the sensor A good fit between the simulation results and the experimental ones, with an acceptable error has been found Results and errors are detailed in Table Experimental time-temperature graphs and CFD simulation temperature probes are presented 1.2.2 References Conclusions Advanced modelling techniques and new simulation strategies were presented for the heat transfer analysis of the electronic components The multi-physics simulation procedures were employed in conjunction with circuit evaluation software in an original approach The work- flows ensured efficient model preparation stages and fast verification of the results The research had an extended literature overview, as well as a large theoretical back- ground A comparison between Finite Element Method and Computational Fluid Dynamics heat transfer procedures was also included The thermal management was defined and explained from an integrated PLM point of view, where Electronics Design Automation, Computer Aided Design and Heat Transfer Calculators concepts were developed The two case studies proved the efficiency and the accuracy of the proposed techniques Data acquisition tools were used and original MATLAB codes were deployed Parameters defined and monitored during the experiments were explained and illustrating graphs were provided Further work will focus on design optimization based on all simulation strategies discussed, to re- duce expensive material consumption and to find a trade-off between environmental demands, price and product performances, that can be satisfied in respect to the actual standards download by : skknchat@gmail.com This paper does not only highlight the experimental or simulation procedures, but it is an integrated approach for describing the multi-physics of electronics heat transfer The novelty of the research consists in the use of integrated simulation tools, tuned with experimental methods that support the workflow References [1] Freescale Semiconductor Inc., Thermal Analysis of Semiconductor Systems, available at: http://cache.nxp.com/files/analog/doc/white_ papep/BasicThermalWP.pdf, accessed: 2016-02-01 [2] W.C Leong, M.Z Abdullah, C.Y Khor and H.J TAN, FSI Study of the effect of air inlet/outlet arrangement on the reliability and cooling performances of flexible printed circuit board electronics, Journal of Thermal Science and Technology, Vol 33, No 1, 2013, pp 43‒53 [3] P Singhala, D.N Shah and B Patel, Temperature Control using Fuzzy Logic, International Journal of Instrumentation and Control Systems (IJICS), Vol 4, No 1, 2014, pp 1‒10 [4] G Sharon, Temperature Cycling and Fatigue in Electronics, http://www.dfrsolutions.com/wpcontent/uploads/2014/10/TemperatureCyclingandFatiguein-Electronics1.pdf, accessed: 2016-04-01 [5] S Satyanarayan S., S Zade, S Sitre S and P Meshram, A Text Book of Environmental Studies (As per UGC Syllabus), Allied Publishers PVT LTD., New Delhi, 2009 [6] J Li and S Zhong-Shan, 3D numerical optimization of a heat sink base for electronics cooling, International Com- munications in Heat and Mass Transfer, Vol 39, No.2, 2012, pp 204-208 [7] J.N Davidson, D.A Stone, M.P Foster and D.T Gladwin, Real - Time Temperature Estimation in a Multiple Device Power Electronics System Subjected to Dynamic Cooling, IEEE Transactions in Power Electronics, Vol 31, No 4, 2016, pp 2709‒2719 [8] Morgan Advanced Materials, Web Based Heat Transfer Calculator, available at http://morganhea- tflow.com/Account/Login?ReturnUrl=%2f, ac- cessed: 2016-01-15 [9] S Rzepka, F Krämer, O Grassmé, and J Lienig, A multi- layer PCB material modeling approach based on laminate theory, Thermal, Mechanical and Multi-Physics Simula- tion and Experiments in Microelectronics and Micro- Systems, edited by G.Q Zhang, Freiburg-im-Breisgau, Germany, April 2008, pp 234‒243 download by : skknchat@gmail.com ... to keep up the pace Radiator with heat pipe combination Heat sinks that combine heat pipes, micro- channels with highly thermally conductive materials can replace conventional coolers The economical... verification of the results The research had an extended literature overview, as well as a large theoretical back- ground A comparison between Finite Element Method and Computational Fluid Dynamics... multi-physics of electronics heat transfer The novelty of the research consists in the use of integrated simulation tools, tuned with experimental methods that support the workflow References [1] Freescale