微电子器件的可靠性研究

随着科技的不断发展,信息处理效率的提高,微电子器件的尺寸越来越小,这使得微电子器件的可靠性问题逐渐凸显出来.微电子器件可靠性主要受四个方面的影响:栅氧化层、热载流子、金属化、静电放电.通过对国内外现状的分析,主要介绍了影响微电子器件可靠性的四个主要因素及其产生原理,并提出了提高微电子器件可靠性的解决方案及措施.     

Effect of synchronized piezoelectric fans on microelectronic cooling performance

This study reports on the influence of dual vibrating fans on flow and thermal fields through numerical analyses and experimental measurements. Two piezoelectric fans were arranged face to face and were vertically oriented to the heat source. 3D simulation was performed with FLUENT and ABAQUS with the use of code coupling interface MpCCI to calculate the velocity and temperature distribution on the horizontal hot plate. The fans' motion was described as deformable parts by ABAQUS at their first mode vibration. The effects of vibration phase difference between the fans corresponding to in-phase (Φ = 0°) and out-of-phase (Φ = 180°) vibrations were explored in terms of transient temperature and flow fields. The purpose is to enhance heat dissipation from the microelectronic component. Comparison with the performance of a single fan is made to assess the significance of the additional fan on thermal performance. Good comparison results were achieved through accurate modeling of the most important features of the fans and through heat transfer. Computed results show that the single fan enhanced heat transfer performance within approximately 2.3 times for the heated surface. By contrast, the dual fans enhanced heat transfer performance within approximately 2.9 for out-of-phase vibration (Φ = 180°) and 3.1 for in-phase vibration (Φ = 0°).     

Conjugate heat transfer in fractal-shaped microchannel network heat sink for integrated microelectronic cooling application

The hydrodynamic and thermal characteristics of fractal-shaped microchannel network heat sinks are investigated numerically by solving three-dimensional N–S equations and energy equation, taking into consideration the conjugate heat transfer in microchannel walls. It is found that due to the structural limitation of right-angled fractal-shaped microchannel network, hotspots may appear on the bottom wall of the heat sink where the microchannels are sparsely distributed. With slight modifications in the fractal-shaped structure of microchannels network, great improvements on hydrodynamic and thermal performance of heat sink can be achieved. A comparison of the performance of modified fractal-shaped microchannel network heat sink with parallel microchannels heat sink is also conducted numerically based on the same heat sink dimensions. It is found that the modified fractal-shaped microchannel network is much better in terms of thermal resistance and temperature uniformity under the conditions of the same pressure drop or pumping power. Therefore, the modified fractal-shaped microchannel network heat sink appears promising to be used for microelectronic cooling in the future.     

Self-cleaning and antireflective packaging glass for solar modules

Incident energy on solar modules is lost both through reflection at the first air/glass interface of the packaging glass and through scattering or absorption by accumulated dust on outdoor panels. While simple antireflective coatings on the glass can help alleviate reflection in systems with motorized tracking, the problem of dust accumulation on module surfaces over time remains and can even be exacerbated by certain antireflective coatings. Here, a process of non-lithographic nanostructuring of the packaging glass surface is shown to both reduce reflection at the air/glass interface and to have a self-cleaning property. The glass surface becomes superhydrophilic upon nanostructuring, with a measured contact angle less than 5° which is proven to be self cleaning by outdoor testing.     

建筑的功耗综合指标与可持续发展

论述了对人类的各种建设活动和各类建筑物可持续发展性能方面进行评价的重要意义;提出加权评分和价值折算两种基本评价方法,计算建筑物在其全寿命期内或研究阶段内,已发生的或预期的,满足人们需求程度和消耗地球资源程度的功耗综合指标.     

节能材料及其在建筑中的应用

分析节能材料在围护结构各部位的应用,以及各种节能材料(或技术)的特点;提出加强新型节能材料(如XPS板、PUR板、SPF保温材料等)和节能玻璃的利用.     

Underfill process for two parallel plates and flip chip packaging

Two parallel plates with a dimension of 5 mm × 5 mm and various gap heights (5, 10, 15, 20, 25, 30, and 35 μm) are simulated using a finite volume method-based software. A three-dimensional model is constructed, and a non-Newtonian underfill flow is simulated using computational fluid dynamics. The flow front advancement is monitored using the volume of fluid model. The underfill process for the two parallel plates and effect of gap height are the main focuses, and the application of flip chip packaging with a gap height of 30 μm is studied. The gap height has a crucial influence on the filling time and pressure drop. The presence of solder bumps is found to have a significant effect on the flow pattern at the melt flow portion. The comparison of the simulation and analytical results are in good conformity for the underfill flow of the two parallel plates.     

Optimum tip gap and orientation of multi-piezofan for heat transfer enhancement of finned heat sink in microelectronic cooling

Piezoelectric fans can be manipulated to generate airflow for cooling microelectronic devices. Their outstanding features include noise-free operation, low power consumption and suitability for confined spaces. This paper presents experimental optimization of tip gap and orientation angle of three piezoelectric fans (multi-piezofan) to maximize the heat removal performance of finned heat sink for microelectronic cooling. Design of experiments (DOE) approach is used for the optimization, and a three dimensional simulation using FLUENT 6.3.2 is carried out to better understand the flow induced by the multi-piezofan and the resulting heat transfer from the heat sink surface. For the optimization, the Central Composite Design (CCD) of response surface methodology (RSM) is exploited from the Design Expert software. In the numerical model, the flow induced by the piezofan is treated as incompressible and turbulent; the turbulence is taken care by the shear stress transport (SST) k–ω model. The experimental results are found to be in good agreement with the predictions. Out of 13 experimental trials determined by CCD, the optimum tip gap and fan orientation are found to be δ = 0.17 and 90° respectively. At this condition, an enhancement in convective heat transfer coefficient exceeding 88% is achieved, compared to natural convection.     

Crevice corrosion of copper for radioactive waste packaging material in simulated groundwater

The investigation described here was conducted to clarify the corrosion behaviour of high level radioactive waste containers made of copper. The influences of oxygen, chloride ion and sulphate ion on copper crevice corrosion were studied in solutions simulating groundwater characteristic of northwest China. The results showed that oxygen, chloride ion and sulphate ion promote crevice corrosion. Chloride ion was found to play a significant role in the crevice corrosion mechanism in copper, but sulphate ion had no effect on the mechanism.     

Saturation boiling of HFE-7100 from a copper surface, simulating a microelectronic chip

Experiments are performed, which investigated the effect of inclination angle, θ, on saturation pool boiling of HFE-7100 dielectric liquid from a smooth, 10×10 mm copper surface, simulating a microelectronic chip. For θ?90° and surface superheats, ΔT_sat>20 K, nucleate boiling heat flux decreases with increased θ, but increases with θ for ΔT_sat<20 K. Similarly, at higher inclinations and ΔT_sat>13 K, nucleate boiling heat flux decreases with increased inclination, but at lower surface superheats the trend is inconclusive. The developed nucleate boiling correlation is within ±10% of the data and the developed correlations for critical heat flux (CHF) and the surface superheat at CHF are within ±3% and ±8% of the data, respectively. Results show that CHF decreases slowly from 24.45 W/cm² at 0° to 21 W/cm² at 90°, then decreases fast with increased θ to 4.30 W/cm² at 180°. The surface superheat at CHF also decreases with θ, from 31.7 K at 0° to 19.9 K at 180°. Still photographs are recorded of pool boiling at different heat fluxes and θ=0°, 30°, 60°, 90, 120°, 150° and 180°. The measured average departure bubble diameter from the photographs taken at the lowest nucleate boiling heat flux of ∼0.5 W/cm² and θ=0° is 0.55±0.07 mm and the calculated departure frequency is ∼100 Hz.     

中国建筑美学发展方向研究

中国的建筑,有其独特的视角和品位。研究了中西方的建筑美学,探索了当今社会的主流价值观,提出,建筑美学发展的新方向,即进行绿色低碳建筑。     

建筑窗体玻璃节能研究

本文对建筑中的外门窗在太阳辐射热的传递与利用,对几种玻璃光在不同波段情况有效光的传递等方面作了分析研究,得出了不同的太阳高度角下、建筑不同朝向的窗户应选用的建筑门窗玻璃。并特别指出Low-E玻璃对建筑节能有着突出的优势。     

Architectural expression and low energy design

The passive approach to the themes of energy savings is essentially based on the morphologic articulations of the constructions. The experience of Studio Nicoletti in low energy building is exemplified by five groups of designs based on different typologies. Cool air stored in the heart of buildings. Tall buildings: energy savings based on minimization of the structural materials and bioclimatic systems. Double skin for cooling the external envelope of the buildings. Urban climate: climatization of large urban fragments, protected either by a glass envelope or a bioclimatic pergola. Integration of various methods including extensive use of natural lighting, like in the design for the New Acropolis Museum in Athens.     

浅谈建筑效果图后期处理

简述建筑效果图后期处理的重要性,阐述了效果图后期处理的步骤,提出了后期处理的几点建议。     

建筑装饰阻燃材料的开发及其应用研究进展

随着我国经济和国民生活水平的提升,人们对于室内建筑生活的环境和安全性越来越重视,建筑装饰阻燃材料是一种新型的室内装饰材料,具有耐热低导热系数等特性能在火灾发生时有效防止易燃物的快速燃烧,在保证人员安全同时减少火灾所造成的损失.总结了目前几种室内装饰阻燃材料的种类及制备方法、并对一些新技术及新工艺进行报道,并提出了建筑装...     

发光二极管无铅封装技术的研究

影响LED发光器件性能的主要因素是树脂的折射率、透光率、tg点、线性膨胀系数、与基材的粘合强度、吸水率等树脂特性,还要综合考虑原料成本和生产过程工艺控制等问题。针对以上因素,研究了LED发光器件在封装过程中的一些关键技术问题,以期在保证产品可靠性的前提下进一步提高封装的成品率、发光效率以及降低封装成本。     

Maintenance optimization for subsea oil pipelines

In this paper, the classical PF interval model, proposed for reliability centered maintenance, is used to optimize the preventive replacement policy of a subsea oil pipeline. The pipeline is subject to failure modes that may lead to oil release and pollution of the sea. The proposed replacement policy is based on regular condition measurements of the quality of an internal pipeline coating (lining). Holes in the coating will expose the pipe material (steel) to a corrosive environment. It is, therefore, important to identify holes in the coating and take action before the corrosion penetrates the pipe wall. The model proposed in the paper can be used to determine the inspection interval that minimizes the average maintenance cost per time unit. The model formulation is outlined and illustrative examples are solved. The mathematical evaluation of the replacement policy requires numerous assumptions. These assumptions have to be tailored to the specific application. The assumptions and the data provided are included for illustrative purposes to exemplify potential results that may be obtained by using the replacement policy.     

Airfoil optimization for wind turbine application

An airfoil optimization method for wind turbine applications that controls the loss in performance due to leading edge contamination is developed and tested. The method uses the class‐shape‐transformation technique to parametrize the airfoil geometry and uses an adjusted version of the panel code XFOIL to calculate the aerodynamic performance. To find optimal airfoil shapes, the derivative‐free Covariance Matrix Adaptation Evolution Strategy is used in combination with an adaptive penalty function. The method is tested for the design of airfoils for the outer part of a megawatt‐class wind turbine rotor blade, and the results are compared with airfoils from Delft University. It is found that the method is able to automatically create airfoils with equal or improved performance compared with the Delft designs. For the tested application, the adjustments performed to the XFOIL code improve the maximum lift, post stall, and the overall drag predictions.     

Process optimization for large-scale hydrogen liquefaction

The investment in the hydrogen infrastructure for hydrogen mobility has lately seen a significant acceleration. The demand for energy and cost efficient hydrogen liquefaction processes has also increased steadily. A significant scale-up in liquid hydrogen (LH₂) production capacity from today's typical 5–10 metric tons per day (tpd) LH₂ is predicted for the next decade. For hydrogen liquefaction, the future target for the specific energy consumption is set to 6 kWh per kg LH₂ and requires a reduction of up to 40% compared to conventional 5 tpd LH₂ liquefiers. Efficiency improvements, however, are limited by the required plant capital costs, technological risks and process complexity. The aim of this paper is the reduction of the specific costs for hydrogen liquefaction, including plant capital and operating expenses, through process optimization. The paper outlines a novel approach to process development for large-scale hydrogen liquefaction. The presented liquefier simulation and cost estimation model is coupled to a process optimizer with specific energy consumption and specific liquefaction costs as objective functions. A design optimization is undertaken for newly developed hydrogen liquefaction concepts, for plant capacities between 25 tpd and 100 tpd LH₂ with different precooling configurations and a sensitivity in the electricity costs. Compared to a 5 tpd LH₂ plant, the optimized specific liquefaction costs for a 25 tpd LH₂ liquefier are reduced by about 50%. The high-pressure hydrogen cycle with a mixed-refrigerant precooling cycle is selected as preferred liquefaction process for a cost-optimized 100 tpd LH₂ plant design. A specific energy consumption below 6 kWh per kg LH₂ can be achieved while reducing the specific liquefaction costs by 67% compared to 5 tpd LH₂ plants. The cost targets for hydrogen refuelling and mobility can be reached with a liquid hydrogen distribution and the herewith presented cost-optimized large-scale liquefaction plant concepts.