Advanced thermal analysis of microelectronics using spreading resistance models

摘要

Thermal analysis of electronic devices is one of the most important steps for designingudof modern devices. Precise thermal analysis is essential for designing an effective thermaludmanagement system of modern electronic devices such as batteries, LEDs, microelectronics,udICs, circuit boards, semiconductors and heat spreaders. For having a preciseudthermal analysis, the temperature profile and thermal spreading resistance of the deviceudshould be calculated by considering the geometry, property and boundary conditions. Thermaludspreading resistance occurs when heat enters through a portion of a surface and flowsudby conduction. It is the primary source of thermal resistance when heat flows from a tinyudheat source to a thin and wide heat spreader. In this thesis, analytical models for modelingudthe temperature behavior and thermal resistance in some common geometries of microelectronicuddevices such as heat channels and heat tubes are investigated. Different boundaryudconditions for the system are considered. Along the source plane, a combination ofuddiscretely specified heat flux, specified temperatures and adiabatic condition are studied.udAlong the walls of the system, adiabatic or convective cooling boundary conditions areudassumed. Along the sink plane, convective cooling with constant or variable heat transferudcoefficient are considered. Also, the effect of orthotropic properties is discussed. Thisudthesis contains nine chapters. Chapter one is the introduction and shows the concepts ofudthermal spreading resistance besides the originality and importance of the work. Chapterudtwo reviews the literatures on the thermal spreading resistance in the past fifty years with a focus on the recent advances. In chapters three and four, thermal resistance of a twodimensionaludflux channel with non-uniform convection coefficient in the heat sink plane isudstudied. The non-uniform convection is modeled by using two functions than can simulateuda wide variety of different heat sink configurations. In chapter five, a non-symmetrical fluxudchannel with different heat transfer coefficient along the right and left edges and sink planeudis analytically modeled. Due to the edge cooling and non-symmetry, the eigenvalues ofudthe system are defined using the heat transfer coefficient on both edges and for satisfyingudthe orthogonality condition, a normalized function is calculated. In chapter six, thermaludbehavior of two-dimensional rectangular flux channel with arbitrary boundary conditionsudon the source plane is presented. The boundary condition along the source plane can beuda combination of the first kind boundary condition (Dirichlet or prescribed temperature)udand the second kind boundary condition (Neumann or prescribed heat flux). The proposedudsolution can be used for modeling the flux channels with numerous different source planeudboundary conditions without any limitations in the number and position of heat sources. Inudchapter seven, temperature profile of a circular flux tube with discretely specified boundaryudconditions along the source plane is presented. Also, the effect of orthotropic properties areuddiscussed. In chapter 8, a three-dimensional rectangular flux channel with a non-uniformudheat convection along the heat sink plane is analytically modeled. In chapter nine, a summaryudof the achievements is presented and some systems are proposed for the future studies.udIt is worth mentioning that all the models and case studies in the thesis are compared withudthe Finite Element Method (FEM).