Thermal management of power electronics modules packaged by a stacked-plate technique

The research presented in this paper is part of a multidisciplinary research program of the Center for Power Electronics Systems at Virginia Tech. The program supported by the Office of Naval Research focuses on the development of innovative technologies for packaging power electronics building blocks. The primary objective of this research is to improve package performance and reliability through thermal management, i.e., reducing device temperatures for a given power level. The task of thermal management involves considering trade-offs in the electrical design, package layout and geometry, materials selection and processing, manufacturing feasibility, and production cost. Based on the electrical design of a simple building block, samples of packaged modules, rated at 600 V and 3.3 kW, were fabricated using a stacked-plate technique, termed metal posts interconnected parallel plate structure (MPIPPS). The MPIPPS technique allows the power devices to be interconnected between two direct-bond copper substrates via the use of metal posts. Thermal modeling results on the MPIPPS packaged modules indicate that the new packaging technique offers a superior thermal management means for packaging power electronics modules.     

火电厂基建项目调试中的安全管理研究

在科学技术的带动下,我国火电技术得到了快速的发展和完善,保证了当地的正常供电。但是从当前火电厂基建项目的实际运行来看,由于很多火电厂为了加快完成任务,不能精确统计并对火电厂运行状况进行测量,导致实际运行中产生了较多安全问题。本文主要对火电厂基建项目调试中的安全管理进行研究,希望可以给相关人员提供参考。     

电力企业营销管理系统设计研究

为了分析研究电力企业的营销管理系统设计,针对某电力企业设计了一种营销管理系统,并分析应用的具体方案及技术.结果显示在该电力企业中,应用营销管理系统之后,不仅提升企业的营销管理效率,提高70％的工作效益,企业的营销管理产生问题的几率也降低40％,具有实际的应用价值.在电力企业中,针对电力企业设计营销管理系统,不仅可以有效降低电力企业营销管理中问题的发生几率,还可以提升电力企业营销管理的工作效益,具有一定的可行性.     

Dielectric strength and thermal performance of PCB-embedded power electronics

Advantages of embedded power electronics compared to classical soldered and bonded DCB modules are smaller size, less weight, and cost savings (Hofmann et al., 2012) [1]. In addition, the low parasitic inductance provided by the embedded technology offers the potential to better utilize the maximum chip voltages and the use of fast switching semiconductors. Compared to a standard module of 15.4 nH, the measurement at the embedded module showed 2.8 nH (Neeb et al., 2014) [2].Heat-spreading in the thick copper plate inside the printed circuit board improves the thermal conductivity. At the same time, by combination with silver sintering for the die attach, higher lifetimes compared with standard DCB (direct copper bonding) assemblies may be reached.Potential risks of this new approach are lifetime limitations, and restricted dielectric strength and thermal performance of the module. In order to evaluate the embedding technology for power devices, test samples were designed and fabricated.In this study, different PCB materials were evaluated. Temperature dependent thermal conductivity of each material was measured and temperature-dependent partial discharge tests have been conducted.     

Optimization of wire connections design for power electronics

In automotive power electronics, low cost and reliability requirements both demand to optimize each part of the package in order to increase its life time during use. The wire bonding breakage accounts for one of the most common failures observed on power modules. In particular, the heel crack mechanism, mainly due to Joule self-heating, can occur in the module, leading to its death. Thus, the wire geometry design has to be set up to maximize its endurance. This paper presents an analytical method able to predict the optimal wire length regarding a wire displacement criterion. Finally, comparisons between experimental results and predictions of the analytical model are given.     

Advanced thermal architecture for cooling of high power electronics

This paper presents a thermal architecture concept for analysis of thermal problems and solutions existing in electronics systems. The thermal problems are categorized into a total of seven levels from chip to system. Advanced thermal technologies for addressing the thermal problems at all seven levels are discussed. Integrating the thermal architecture with the electronic architecture can significantly improve the effectiveness of the thermal management.     

Microjet cooling devices for thermal management of electronics

This research is an effort to demonstrate the applicability of miniaturized synthetic jet (microjet) technology to the area of thermal management of microelectronic devices. Synthetic jets are jets which are formed from entrainment and expulsion of the fluid in which they are embedded. Design issues of microjet cooling devices are discussed along with characterization of excitation elements and the turbulent synthetic jets produced thereby. Geometrical parameters of the microjet cooling devices were empirically optimized with regards to cooling performance. The cooling performance of the optimized microjets was compared with previous theoretical and empirical studies of conventional jet impingement. The cooling performance of the microjet devices has been investigated in an open environment as well as in a vented and closed case environment. In such experiments, the synthetic jet impinges normal to the surface of a packaged thermal test die, comprising a heater and a diode-based temperature sensor. This test assembly allows simultaneous heat generation and temperature sensing of the package, thereby enabling assessment of the performance of the synthetic jet. Using microjet cooling devices, a thermal resistance of 30.1/spl deg/C/W has been achieved (when unforced cooling is used, thermal resistance is 59.6/spl deg/C/W) when the test chip is located at 15mm spacing from the jet exit plane. In order to more directly compare and scale the cooling results, a preliminary study on heat transfer correlations of the microjet cooling device has been performed. Finally, a comparison of the performance of the microjet cooler with standard cooling fans is given.     

智能移动终端产品热设计研究

为了解决智能移动终端局部过热的问题,从平面热布局面积入手,采用热传导技术,抓住多模智能移动终端热源器件布局的关键,给出一个考虑散热的布局最小面积;根据热流密度来计算结构的整机高度。通过热仿真来进行布局和结构设计的模拟,给出结构设计的参考意见,最后通过测试去验证和完善热设计。经过实际产品的发热红外图谱分布试验,获得智能移动产品实际的温度分布平面图,得到了与仿真一致的结论。     

Robust snubberless soft-switching power converter using SiC power MOSFETs and bespoke thermal design

A number of harsh-environment high-reliability applications are undergoing substantial electrification. The converters operating in such systems need to be designed to meet both stringent performance and reliability requirements. Semiconductor devices are central elements of power converters and key enablers of performance and reliability. This paper focuses on a DC–DC converter for novel avionic applications and considers both new semiconductor technologies and the application of design techniques to ensure, at the same time, that robustness is maximized and stress levels minimized. In this respect close attention is paid to the thermal management and an approach for the heatsink design aided by finite element modelling is shown.     

探讨火力发电企业ERP体系结构

作者结合实际参加了发电企业信息化建设,通过调研大量电力行业信息化建设项目和参考ERP实施相关资料的基础上对发电企业ERP特点和体系结构进行分析,最后结合火力发电企业的特点提出了发电企业ERP体系结构。     

Investigations of thermal interfaces aging under thermal cycling conditions for power electronics applications

This paper presents new investigations on the aging of Thermal Interface Materials (TIMs) subjected to thermal cycling conditions. The challenge was to design a specific and original set-up in order to not only undergo avionic temperature mission profile (?50 °C/+150 °C) but also to perform standardized thermal characterization at always same conditions. Thermal conductivity is used as aging indicator. Several TIM materials (change phase, graphite and polymer based) have undergone more than 1500 of such cycles. As a result, only the phase change material thermal interface has been affected with a 30% increase of initial thermal resistance.     

Implications of thermal instability on HBT power amplifier reliability

Thermal stability is one of several important performance requirements for RF power amplifier modules used for cellular applications. In this work, the conditions for thermal instability in an HBT array for shared and individual ballast configurations are evaluated using experimental results from RF biased life test (RFHTOL) and ADS simulations. The instability is modest under nominal operating conditions, but becomes more severe at elevated temperatures which are frequently used in accelerated reliability tests such as RFHTOL. Thermally unstable power cells exhibit current crowding where one or two cells hog most of the current, resulting in localized hot spots from increased power dissipation density. This paper discusses the link between reliability failures during RFHTOL reliability testing and the thermal stability of HBT arrays used in a power amplifier. Shared ballast arrays are shown to be less thermally stable than individually ballasted arrays and thus have more failures during RFHTOL testing. Electro-thermal results indicate the layout aspects of power amplifier module also play an important role in determining junction temperatures for various stages.     

Degradation of thermal interface materials for high-temperature power electronics applications

The specific thermal resistance values of several thermal interface materials (TIMs) intended to thermally enhance Cu contact pairs and their degradation under isothermal ageing at 170 °C have been investigated using Cu stack samples consisting of 10 Cu discs and 9 layers of the TIMs. The results obtained indicate that the specific thermal resistance values of the as-prepared Cu stack samples, one with conductive Ag thermal grease, one with Sn–3.5Ag solder joints and one with 25 μm thick Sn foil as TIMs are significantly lower than those of the Cu stack sample without any TIM. However, after the isothermal ageing at 170 °C for 90 days, the specific thermal resistance values of the samples with these TIMs are not substantially different from those of the sample without any TIM. Also reported in this paper is an estimation of testing errors for the specific thermal resistance values, microstructure characterization of the aged samples and effect of the degradation of these TIMs on the thermal performance of a high-temperature half bridge power switch module.     

纯电动汽车热管理系统的研究

随着世界各国对环境问题的日益重视,纯电动汽车已受到社会各界的广泛青睐,而电动汽车的发展,很大程度上受电池热管理系统、电机和电机驱动热管理系统、空调热管理系统三大系统技术成熟度的制约.本文将从结构布置和控制方式方面研究讨论,提供建议,以减少电池能耗,增加续航里程、提升整车可靠性和舒适性,希望能为EV热管理系统设计提供借鉴和参考.     

供电企业绩效管理体系优化设计

本文主要对供电企业绩效管理系统的优化进行了具体设计,采用了J2EE程序架构和Java语言设计,并结合B/S分布式多层体系结构,实现一体化平台操作界面。     

有机印制板上倒装芯片的可靠性研究

对一种有机印制板上倒装芯片（Ｆｌｉｐｃｈｉｐ）进行温度循环试验,测出其失效分布曲线,然后通过扫描声显微镜、红外显微镜和剖面等失效分析手段,发现失效模式主要是合金焊点中的断裂以及下部填充料（Ｕｎｄｅｒｆｉｌ）中的损伤如分层（Ｄｅｌａｍｉｎａｔｉｏｎ）和内部裂缝（Ｃｒａｃｋ）。详细地阐述了倒装芯片中的下部填充料损伤在温度循环试验条件下的产生、发展及它们对合金焊点可靠性的影响。     

Transient thermal management of temperature fluctuations duringtime varying workloads on portable electronics

This paper describes the investigation of solid to liquid phase change materials (PCM's) for passive energy storage during the condition of time varying workloads on portable electronics. The model investigated includes a thermal control unit (TCU) embedded in an epoxy polymer. A TCU is an enclosure that contains phase change material (PCM) and a thermal conductivity enhancer, is located near the power source, and acts as an energy storage and heat-spreading module. Physical experiments were carried out to investigate the performance improvements of introducing a TCU into an embedded system and were used to validate the accuracy of the numerical model. Numerical simulations were performed to study the effect duty cycles and substrate thermal conductivities have on the thermal performance of the electronic wearable computer system with passive energy storage. Additionally, the TCU was numerically modeled to determine the influence of boundary conditions on TCU performance. To quantify the improvements of the system, metrics were developed from analyzing the thermal evolution of the TCU parameters, such as temperature fields, temperature bands, PCM characteristics, and power loads. Results indicate that using a TCU for passive energy storage significantly increases the portable electronics system's operational performance. Duty cycles with the same average power over the duration of the cycle do not influence the length of the PCM phase change time, but do impact the mean value of the temperature fluctuation bands     

关于电力市场下火电厂机组检修计划的探讨

火电产的机组检修计划的制定对于保障火电厂的发电设备安全,电力的正常供应具有重要的作用.本文主要从电火厂机组检修的模型建立和具体的算例分析两个方面展开讨论.     

新型封装材料与大功率LED封装热管理

高效散热封装材料的合理选择和有效使用是提高大功率LED(发光二极管)封装可靠性的重要环节。在分析封装系统热阻对LED性能的影响及对传统散热封装材料性能进行比较的基础上,阐述了金属芯印刷电路板材料、金属基绝缘板材料、陶瓷基板材料、导热界面材料和金属基复合材料结构特点、导热性能及其封装应用实例。指出了封装材料的研究重点和亟待解决的问题。     

基于ASP的实验室开放管理系统的设计与实现

基于ASP语言设计了实验室开放管理系统,通过网络实现了教师对实验课程的发布、修改,以及学生对实验的预习、预约。