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- 实验方案
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Development and optimization of the laser-assisted bonding process for a flip chip package
摘要： In a ?ne pitch ?ip chip package, a laser-assisted bonding (LAB) technology has recently been developed to overcome several reliability and throughput issues in the conventional mass re?ow (MR) and thermal compression bonding technology. This study investigated the LAB process for a ?ip chip package with a copper (Cu) pillar bump using numerical heat transfer and thermo-mechanical analysis. During the LAB process, the temperature of the silicon die was uniform across the entire surface and increased to 280 (cid:3)C within a few seconds; this was high enough to melt the solder. The heat in the die was quickly conducted to the substrate through the Cu pillar bumps. Meanwhile, the substrate temperature was low and remained constant. Therefore, a stable solder interconnection was quickly achieved with minimal stress and thermal damage to the package. The substrate thickness, the number of Cu bumps, and the bonding stage temperature were found to be important factors affecting the heat transfer behavior of the package. The temperature of the die decreased when a thinner substrate, a higher number of Cu bumps, and a lower bonding stage temperature were used. If the temperature of the die was not suf?ciently high, insuf?cient heat was transferred to the solder to melt it, resulting in incomplete solder joint formation. Thermo-mechanical analysis also showed that the LAB process produced lower warpage and thermo-mechanical strain than the conventional MR process. These results indicated that a LAB process using a selective local heating method would be bene?cial in reducing thermo-mechanical stress and increasing throughput for the ?ne pitch ?ip chip packages.
关键词： Laser-assisted bonding,Copper pillar bump,Thermo-mechanical analysis,Flip chip package,Heat transfer
更新于2025-09-11 14:15:04
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Numerical Simulation on Laser Welding considering Surface Deformation and Convective Heat Transfer
摘要： Laser welding requires much capital investment comparing with generally employed arc welding. However, the laser welding enables to join very small objects with high accuracy because the laser has high energy density and high controllability. In addition, it is possible to suppress welding deformation due to low heat input. Therefore, the laser welding is employed for various joining processes. This study aims to clarify formation mechanism of weld pool in laser cladding in order to improve incomplete fusion through numerical simulation on laser welding considering deformation of weld pool surface and convective heat transfer in it. Consequently, it was found that the gas pressure plays important role for improve incomplete fusion in laser welding. The higher pressure of gas increases penetration depth by pushing away molten metal at center of the weld pool without changing direction of convection.
关键词： Laser Welding,Simulation,Convective Heat Transfer,Surface Deformation
更新于2025-09-11 14:15:04
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Improved banded method for spectral thermal radiation in participating media with spectrally dependent wall emittance
摘要： To develop an efficient and practical spectral radiation model for CFD simulations, a banded approach is proposed for a mixture of carbon dioxide and water vapor in varying thermodynamic states. Using a previously reported band dividing scheme, a statistical narrow band model is implemented to provide gray band absorption coefficient databases. The databases were then approximated by certain simple correlations, which can be readily used in CFD calculations of RTE solvers. The correlations were validated in several 1D and 3D benchmarks representing various combustion conditions. The accuracy and CPU cost of the proposed banded approach were studied and compared with those of other similar methods. The results demonstrated that the new approach is an efficient and accurate method that can be conveniently applied in a commercial CFD code for spectral radiation; moreover, it can handle non-gray walls. As a practical case study, the proposed approach was used to simulate radiative heat transfer within a back pass channel of a CFB boiler. The effect of combustion scenarios, i.e., air- and oxygen-fired, boiler load, inlet flow conditions, and wall material, was analyzed by the CFD model. The predictions of two different RTE solvers, i.e., P1 and DO, and the required CPU time were compared for gray and non-gray models.
关键词： Non-gray wall,Back pass channel,CFB boiler,Radiation heat transfer,Band absorption coefficient,Narrow band calculation,Non-gray gas modeling,Banded approach
更新于2025-09-11 14:15:04
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[Energy, Environment, and Sustainability] Advances in Solar Energy Research || Shell-and-Tube Latent Heat Thermal Energy Storage (ST-LHTES)
摘要： Thermal energy storage (TES) unit has become an integral part of thermal energy conservation. As the name implies, the device simply stores heat when energy from the source is available in excess, and releases the same when energy from the source falls short of the requirement. By doing so, such devices deliver heat energy across the temporal barrier, making thermal energy available for extended working hours of solar thermal power plants (STPP). High energy density and stable operation for long duration are desirable qualities which may be found in latent heat thermal energy storage (LHTES) system. To exploit the advantage of LHTES, the most common design reported in the literature is shell-and-tube type latent heat thermal energy storage (ST-LHTES) systems with phase change material ?lled in shell side, while (heat transfer ?uid) HTF ?ows in the tubes (or vice versa). The present chapter gives a detailed classi?cation of ST-LHTES systems based on geometry, orientation and relative position of PCM and HTF in heat exchanger along with the classi?cation of phase-change materials. Numerical modelling of heat transfer phenomenon is presented along with some simulated results for enhanced PCM, clearly describing the coupling between PCM and HTF domain. Various heat transfer enhancement techniques and parametric analysis have been discussed with challenges and future scope.
关键词： Latent heat,Thermal energy storage,Coupling,Shell and Tube Heat Exchanger,Heat transfer ?uid,Phase change material
更新于2025-09-10 09:29:36
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Thermal meta-device in analogue of zero-index photonics
摘要： Inspired by the developments in photonic metamaterials, the concept of thermal metamaterials has promised new avenues for manipulating the flow of heat. In photonics, the existence of natural materials with both positive and negative permittivities has enabled the creation of metamaterials with a very wide range of effective parameters. In contrast, in conductive heat transfer, the available range of thermal conductivities in natural materials is far narrower, strongly restricting the effective parameters of thermal metamaterials and limiting possible applications in extreme environments. Here, we identify a rigorous correspondence between zero index in Maxwell’s equations and infinite thermal conductivity in Fourier’s law. We also propose a conductive system with an integrated convective element that creates an extreme effective thermal conductivity, and hence by correspondence a thermal analogue of photonic near-zero-index metamaterials, a class of metamaterials with crucial importance in controlling light. Synergizing the general properties of zero-index metamaterials and the specific diffusive nature of thermal conduction, we theoretically and experimentally demonstrate a thermal zero-index cloak. In contrast with conventional thermal cloaks, this meta-device can operate in a highly conductive background and the cloaked object preserves great sensitivity to external temperature changes. Our work demonstrates a thermal metamaterial which greatly enhances the capability for molding the flow of heat.
关键词： thermal cloak,zero-index photonics,thermal metamaterials,convective heat transfer,heat conduction
更新于2025-09-10 09:29:36
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Measurements, Mechanisms, and Models of Heat Transport || Macroscopic Analysis of the Flow of Energy Into and Through Matter From Spectroscopic Measurements and Electromagnetic Theory
摘要： That light (what we see) and heat (what we feel) traveling through air or vacuum are the same phenomena is now well-known. However, heat transfer within a solid is treated differently: most researchers consider elastic waves as the main carrier of interior heat, after Debye (1914). This situation in part stems from the vibrations of molecules or ions in condensed matter, which are connected with the heat capacity of a solid, not being probed by spectroscopy until B1930 due to instrumental limitations (Sawyer, 1963).
关键词： radiative transfer,spectroscopy,infrared,heat transfer,light,vibrational spectroscopy
更新于2025-09-10 09:29:36
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Measurements, Mechanisms, and Models of Heat Transport || A Macroscopic Model of Blackbody Emissions With Implications
摘要： Measurements of heat transfer in gas, pourable liquids, and nonmetallic solids point to diffusion of radiation being an essential component of heat transport (Chapter 5, Chapter 6 and Chapter 7). Diffusive radiation of heat is a direct outcome of a kinetic theory of gas that incorporates the inelastic nature of collisions (Chapter 5). Long ago, Lommel (1878) associated blackbody (BB) emissions from solids with inelastic losses, and specifically discussed damping of atomic vibrations (Kangro, 1976), but was unable to provide a formula for thermal emissions. His ideas were set aside in the early 1900s. Yet, strong theoretical support for inelasticity exists in the laws of thermodynamics, when these are framed in terms of the macroscopic behavior of light (Chapter 1 and Chapter 5). Fourier’s laws, which describe heat transfer as energy flowing through a medium (Chapter 3), are also consistent with diffusive of radiation explaining conduction in solids.
关键词： blackbody emissions,inelastic collisions,diffusive radiation,heat transfer,thermal emissions,kinetic theory,Fourier’s laws,thermodynamics
更新于2025-09-10 09:29:36
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AIP Conference Proceedings [Author(s) INTERNATIONAL CONFERENCE ON CIVIL, MECHANICAL AND MATERIAL ENGINEERING: ICCMME 2018 - Jeju-do, Korea (16–18 March 2018)] - Experimental study on the monomer structure of solar semiconductor cold wall
摘要： In this paper, solar semiconductor cold wall structure was adopted in the net-zero energy buildings, NZEB for short. The heat transfer and refrigeration effect of the monomer structure of semiconductor cold wall were tested, we get that the monomer structure of semiconductor cold wall has certain cooling effect. However, the heat exchange effect is not good of the cold and hot aluminum plate only through natural convection and radiation heat transfer. It is necessary to further study the process of semiconductor refrigeration and heat transfer and the factors that affect the cooling effect. At the same time, it put forward a series of suggestions and improvement opinion for NZEB in hot summer and cold winter areas.
关键词： semiconductor refrigeration,refrigeration effect,heat transfer,net-zero energy buildings,solar semiconductor cold wall
更新于2025-09-10 09:29:36
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Surface plasmon-enhanced near-field thermal rectification in graphene-based structures
摘要： We propose a thermal rectification structure composed of InSb and graphene-coated 3C-SiC separated by a nanoscale vacuum gap. To obtain an obvious thermal rectification effect, the permittivities of these materials are all considered to be temperature-dependent. Numerical calculations based on fluctuation electrodynamics reveal that the introduction of graphene into the structure enhances significantly near-field radiative heat flux and thermal rectification efficiency owing to the strong coupling of surface plasmon-polaritons between InSb and graphene. In general, the rectification efficiency above 60% can be maintained for the vacuum gap less than 70 nm. The rectification efficiency exceeding 95% is realized for a vacuum gap of 10 nm and a chemical potential of 0.1 eV. Increasing the emitter’s temperature leads to the drastic increase of the rectification efficiency in a wider temperature range. A lower chemical potential seems more favorable to raising rapidly the rectification efficiency. The above results might be helpful in designing a thermal diode with higher efficiency and wider vacuum gap.
关键词： near-field radiative heat transfer,thermal rectification,InSb,surface plasmon-polaritons,graphene,3C-SiC
更新于2025-09-10 09:29:36
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[IEEE 2017 International Renewable and Sustainable Energy Conference (IRSEC) - Tangier (2017.12.4-2017.12.7)] 2017 International Renewable and Sustainable Energy Conference (IRSEC) - Modeling the Solar Station with the Parabolic Trough Collector Receiver
摘要： In this paper, we present a detailed mathematic model of the Parabolic Trough Collector (PTC) receiver, which has been theoretically studied. The PTC receiver contains a circular tube absorber with a suitable selective layer, surrounded by a glass cover locate along the focal line of PTC receiver. We have established a mathematical model to control the fluid temperature as well as the absorber and the glass cover temperatures.
关键词： heat transfer fluid,solar energy,solar flux,outlet temperatures,Parabolic Trough Collector Receiver
更新于2025-09-10 09:29:36