Investigation of the thermal performance of micro-whisker structured silicon heat spreaders for power devices

The driving forces of developments in power electronics are the continuing miniaturization and enhancement of power densities. New packaging concepts are required allowing the dissipation of a power loss density of up to several hundred W/cm² at operation temperatures as low as possible. A promising attempt to decrease the thermal resistance to the ambient is the development of silicon substrates structured with microwhiskers perpendicular to its surface. An industrial application of this new heat spreader technology in power electronic modules makes necessary the specification of the substrate properties. In this work, a new method for determination of thermal qualities based on laser heating of the heat spreader, surface temperature measurement by thermovision, and dynamic reverse modeling is described. For numerical determination of the thermal characteristics, the measured data are evaluated with the help of a thermal model of the heat spreaders under various boundary conditions. The respective temperature distributions are calculated with a new simulation tool using an alternating-direction implicit algorithm (ADI-method). Results obtained from heat spreaders with microwhisker treatment are compared with those from reference samples with a polished surface. Based on these results a view on future applications for power electronics assemblies are derived.     

The potential of diamond and SiC electronic devices for microwaveand millimeter-wave power applications

The potential of SiC and diamond for producing microwave and millimeter-wave electronic devices is reviewed. It is shown that both of these materials possess characteristics that may permit RF electronic devices with performance similar to or greater than what is available from devices fabricated from the commonly used semiconductors, Si, GaAs, and InP. Theoretical calculations of the RF performance potential of several candidate high-frequency device structures are presented: the metal semiconductor field-effect transistor (MESFET), the impact avalanche transit-time (IMPATT) diode, and the bipolar junction transistor (BJT). Diamond MESFETs are capable of producing over 200 W of X-band power as compared to about 8 W for GaAs MESFETs. Devices fabricated from SiC should perform between these limits. Diamond and SiC IMPATT diodes also are capable of producing improved RF power compared to Si, GaAs, and InP devices at microwave frequencies. RF performance degrades with frequency and only marginal improvements are indicated at millimeter-wave frequencies. Bipolar transistors fabricated from wide bandgap material probably offer improved RF performance only at UHF and low microwave frequencies     

电力电子装置通讯电路的研究

研究了一种简化电力电子装置通讯电路的方案,将控制器和驱动电路之间多路并行信号转化成串行信号,并且在一台单相逆变器上进行了实验验证,使逆变器得到了很好的输出波形.     

X band c.w. TRAPATT oscillators using ring diodes on diamond heat spreaders

TRAPATT diodes for X band c.w. operation have been made using both double-epitaxy and diffusion techniques. These p+nn+ devices are fabricated in ring configurations and mounted on type-IIA diamond heat spreaders. A c.w. TRAPATT performance of 3.3 W and 18.5% efficiency has been achieved at 8 GHz using these diodes.     

4H-SiC power devices for use in power electronic motor control

Silicon carbide (SiC) is an emerging semiconductor material which has been widely predicted to be superior to both Si and GaAs in the area of power electronic switching devices. This paper presents an overview of SiC power devices and concludes that the MOS turn-off thyristor (MTO™), comprising of a hybrid connection of SiC gate turn-off thyristor (GTO) and MOSFET, is one of the most promising near term SiC switching device given its high power potential, ease of turn-off, 500°C operation and resulting reduction in cooling requirements. The use of a SiC and an anti-parallel diode are primary active components which can then be used to construct an inverter module for high-temperature, high-power direct current (d.c.) motor control.     

Current SiC technology for power electronic devices beyond Si

Recent big progress in SiC technology for power electronic devices beyond Si is reviewed. Historical aspects in SiC development are described. Current subjects such as bulk crystal growth, epitaxial growth, device processes for new generation of SiC power devices are briefly explained. Commercially available Schottky diodes and possible switching devices are introduced.     

Hot rocks [single crystal diamond for power semiconductor devices]

This article describes the production, using chemical vapour deposition, of single crystal synthetic diamonds. It then discusses their practical use in semiconductor devices. Diamond is a wide band gap semiconductor with high breakdown voltage, high saturation velocity, high carrier mobility, and high thermal conductivity. In addition it is extremely radiation hard. Diamond semiconductors are ideal for high-power, high-frequency electronic applications.     

功率器件寿命预测模型

分析了功率器件寿命预测研究现状,并通过恒定应力加速寿命试验来提取器件失效参数,利用正态分布统计方法提取Coffin-Manson寿命预测模型参数建立功率器件寿命预测模型并进行分析。结果表明,模型参数拟合值和实测值的相关系数均在96.8%以上,试验结果满足正态分布统计,说明得到的模型参数是有效的。模型在ΔTj为70.5℃下仿真值与试验值的相对误差为2.768%,证明了该模型的可行性和准确性。     

电力电子器件的模块化与集成化

概要介绍电力电子器件的模块化与集成化发展进程以及功率模块、单片集成模块和智能功率模块等三种常用的电力电子器件模块。     

Orientation independent two-phase heat spreaders for space constrained applications

This paper presents a novel orientation independent two-phase heat spreader for constrained space applications.¹ The two-phase spreader plate has a central evaporator section with an integrated condenser along the edges. A micro-fabricated three-dimensional enhancement structure is employed to improve the heat transfer performance of the spreader plate. The thermal performance of the system is characterized at different power levels and also for various inclination angles. At the maximum heat flux of 6.3 W/cm² under natural convection conditions, the junction temperature of the two-phase spreader was found to be 47.6 °C less than the junction temperature predicted for an equivalent solid metal plate subjected to similar boundary conditions. The performance of the spreader plate is found to be orientation independent as long as the enhancement structure in the evaporator remains flooded with the coolant liquid.     

Silicon heat pipes used as thermal spreaders

An increase in power densities in electronic devices is a direct consequence of their miniaturization and performance improvements. We propose the use of flat miniature heat pipes with micro capillary grooves to spread heat flux across a heat sink. Models of the structure were developed to calculate heat transfer limitations and temperature drops. A brass/water prototype was fabricated to demonstrate the feasibility of heat spreading using this type of heat pipe. Simulation and experimental results obtained with the prototype are described. The dissipated power reached 110 W/cm/sup 2/ without heat transfer limitations. The results are then extended to the design of this type of heat pipe in silicon. Thermal performance was calculated. Simulation, experimental results and the fabrication process are presented.     

碳化硅电力电子器件在电力系统的应用展望

就目前来看,我国的科学技术得到快速发展。在这一背景下,半导体的器件在制作以及生产的工艺上都得到一定的发展。而碳化硅属于宽带材料的一种,其主要的特点是高热导率、高饱和电子漂移速率以及高击穿场强等。通过这种新型的半导体,可以实现大功率、高压以及高温应用。另外,由于碳化硅成本的大幅度降低,且其性能得到提升,使得碳化硅在电力系统中得到普遍使用。本文将对电子系统中碳化硅电力电子器件的应用进行了深入的分析以及探讨。     

Characterization of piezoelectric materials as a power source for electronic implantation devices

Piezoelectric materials are attractive as a power source for implanted nanoelectronic systems using the energy generated by weaves alive and physiological or biophysical processes. The study of a piezoelectric thin film sensor and its behavior as mechanical to electrical energy converter is discussed. A piezoelectric polymer—PVDF—was characterized and its physical parameters measured. Besides, the development of a PVDF-based power source activated by mechanical vibrations and efficiencies around the 5% is presented.     

Thermal simulation of joints with high thermal conductivities for power electronic devices

The thermal properties of new power modules joined by materials with high thermal conductivities, such as Ag or Cu nanoparticle joints, can differ from those of current modules joined by ordinary solders with low thermal conductivities. However, these properties have not been thoroughly investigated thus far. The overall thermal resistance of a simple simulation module was calculated by the 3-dimensional finite element method to study the correlation between the thermal conductivity of the joint layer and the thermal properties. The calculation results identified an optimal thickness to achieve the minimum thermal resistance when the thermal conductivity of the joint layer is much higher than that of the heatsink. This is presumed to occur because the thermal resistance decreases in the heatsink much more than it increases in the joint layer, owing to the increased uniformity of thermal spreading as the joint-layer thickness increases to the optimal value. This effect of thermal resistance reduction with thickening of the joint layer is seen when the thermal conductivity of the joint layer is sufficiently higher than that of the heatsink and the area of the joint layer is sufficiently smaller than that of the heatsink. The same effect is also expected in an actual module with a joint between a silicon carbide chip and a direct bonded copper substrate. This study reveals that the design concept for power modules should change to preliminarily estimate the optimal thickness to achieve the minimum thermal resistance when the thermal conductivity of the joint layer is much higher than that of the heatsink.     

Real-time computation of thermal constraints in multichip power electronic devices

In this paper, we present an implementation of a thermal modeling method, based on thermal impedances analysis and applied to a multichip module used as a power converter. Analytical functions of thermal impedances are derived from direct measurements of chips temperature with optical fiber sensors. We describe an original algorithm with a recurrent procedure to compute directly and accurately the convolution integrals with high speed performances. Finally, experimental measurements, in real working conditions, have been performed in order to complete the validation of the real-time estimation of the junction temperatures of the power electronic package.     

Single chamber compact two-phase heat spreaders withmicrofabricated boiling enhancement structures

Presents the thermal performance evaluation of a compact single-chamber two-phase heat spreader. The heat spreader setup has a central evaporator section with integrated fins for cooling along the edges. The evaporator employs a micro-fabricated three-dimensional (3-D) copper structure for enhancing boiling heat transfer. The thermal performance of the system was characterized at various power levels and condenser cooling conditions. The size of the boiling enhancement structure and effects of liquid fill volumes on performance were also investigated. Incorporation of the enhancement structure resulted in an improvement in the spreader thermal performance by decreasing the wall temperature at the evaporator by 8°C, for a power dissipation of 36 W/cm² at an air speed of 1 m/s. The maximum heat flux obtained based on a maximum evaporator temperature of 75°C for an air speed of 1 m/s was 42.5 W/cm². Variation in the liquid fill volume showed negligible effect on the maximum temperature at the evaporator, as long as the enhanced structure was fully flooded     

基于大功率电子器件的冷控系统设计

随着电子元器件的集成化程度越来越高,散热问题已经成为制约电子技术发展的主要因素之一.有效解决电子元器件的散热问题已经成为当前研究的热点问题.传统的风冷系统已经很难满足其散热要求.为此,以电子设备的水冷系统为研究对象,以ATmega 1280微处理器作为基础,设计了一款低成本、高效率的大功率电子器件的水冷控制系统,对系统各关键硬件模块做了详细的介绍,并采用模块化的方法给出了系统的软件架构.综合实验结果表明该系统操作方便、可靠性好、电磁兼容性强,具有较高的实用价值.     

探究电力电子器件及其应用的现状和发展

电力电子器件随着我国经济的发展与社会的进步已经在众多领域中进行了应用.本文主要就电力电子器件应用的现状、应用中存在的问题、未来发展的趋势三个方面的内容进行论述.     

Validation of the DJOSER analytical thermal simulator for electronic power devices and assembling structures

The present communication deals with the tests for the validation of the DJOSER steady-state thermal simulation program, purposely designed for power electronic assembling structures and which is based on the resolution of analytical relationships. The validation experiments were carried out theoretically by comparing the thermal maps with those obtained using standard finite-elements programs and yielding temperature accuracy below 1%. Experimental tests were also performed on purposely built multi-layer structures and industrial circuits with power diodes mounted in naked-chip configuration. The simulated maps were compared with accurate thermo-graphic recordings and showed a good agreement, testifying the validity of the mathematical model.