环氧模塑封材料的热–机械疲劳失效分析

封装材料的热疲劳失效是封装器件失效的主要原因之一.对在微电子封装中应用很广的环氧模塑封装材料进行了常温和高温下的拉伸、疲劳实验.基于以疲劳模量作为损伤因子的疲劳寿命预测模型,相应的材料参数通过实验获得.并通过实验得出了该环氧模塑封装材料考虑温度影响的疲劳寿命预测模型,利用该模型可以对微电子封装用高聚物的疲劳寿命进行预测.     

环氧模塑封材料的热-机械疲劳失效分析

封装材料的热疲劳失效是封装器件失效的主要原因之一。对在微电子封装中应用很广的环氧模塑封装材料进行了常温和高温下的拉伸、疲劳实验。基于以疲劳模量作为损伤因子的疲劳寿命预测模型,相应的材料参数通过实验获得。并通过实验得出了该环氧模塑封装材料考虑温度影响的疲劳寿命预测模型,利用该模型可以对微电子封装用高聚物的疲劳寿命进行预测。     

芯片叠层封装的失效分析和热应力模拟

通过高温高湿加速实验对双芯片叠层封装器件的失效进行了研究,观察到存在塑封料与上层芯片、BT基板与塑封料或贴片胶的界面分层和下层芯片裂纹等失效模式.结合有限元分析对器件内热应力分布进行了计算模拟,分析了芯片裂纹的失效机理,并从材料性能和器件结构角度讨论了改善叠层封装器件可靠性的方法.     

牛津型斯特林制冷机的加速寿命评价

分析了牛津型斯特林制冷机的主要失效模式和失效机理，针对蓄冷器污染的失效模式提出了高温工作加速寿命评价方法。对典型牛津型制冷机进行了不同温度下的动力学响应试验，确定了适合的加速寿命试验的应力条件。加速寿命试验已进行1200h，样机性能出现了退化。样机工作参数的走势显示，退化呈现由污染所致的典型特征，初步验证了高温工作加速污染退化的可行性。     

牛津型斯特林制冷机的加速寿命评价

分析了牛津型斯特林制冷机的主要失效模式和失效机理，针对蓄冷器污染的失效模式提出了高温工作加速寿命评价方法。对典型牛津型制冷机进行了不同温度下的动力学响应试验，确定了适合的加速寿命试验的应力条件。加速寿命试验已进行1200h，样机性能出现了退化。样机工作参数的走势显示，退化呈现由污染所致的典型特征，初步验证了高温工作加速污染退化的可行性。     

牛津型斯特林制冷机的加速寿命评价

分析了牛津型斯特林制冷机的主要失效模式和失效机理,针对蓄冷器污染的失效模式提出了高温工作加速寿命评价方法.对典型牛津型制冷机进行了不同温度下的动力学响应试验,确定了适合的加速寿命试验的应力条件.加速寿命试验已进行1200h,样机性能出现了退化.样机工作参数的走势显示,退化呈现由污染所致的典型特征,初步验证了高温工作加速污染退化的可行性.     

互连铝通孔电迁移特征及其可靠性研究

研究了超大规模集成电路铝互连系统中铝通孔的电迁移失效机理及其可靠性寿命评价技术.试验采用CMOS和BiCMOS两种工艺各3组的铝通孔样品,分别在三个温度、恒定电流的加速条件下试验,以通孔开路为电迁移失效判据,最后得到了在加速条件下互连铝通孔的电迁移寿命,其结果符合标准的威布尔分布,试验准确可行.通过电迁移模型对试验数据进行了拟合,得到了激活能、电流加速因子和温度加速因子,计算出了正常工作条件下通孔电迁移的寿命,完成了对铝通孔电迁移的研究和寿命评价.     

光模块加速寿命试验最佳测试温度的确定方法

为了确定小型可热插拔式(SFP)光模块寿命试验所需的最短时间,提出了基于加速因子最大化的最佳测试温度的确定方法。首先,利用阿伦尼斯模型证明了温度的选择不会改变寿命预测结果,并讨论了加速因子取极大值的条件。然后利用步进温度实验获得的驱动电流随测试温度变化的曲线给出了最佳测试温度的确定方法。最后,计算分析表明由于驱动电流受温度的影响,在最佳测试温度下进行光模块寿命试验仍然很困难。     

芯片叠层封装的失效分析和热应力模拟

通过高温高湿加速实验对双芯片叠层封装器件的失效进行了研究,观察到存在塑封料与上层芯片、BT基板与塑封料或贴片胶的界面分层和下层芯片裂纹等失效模式．结合有限元分析对器件内热应力分布进行了计算模拟,分析了芯片裂纹的失效机理,并从材料性能和器件结构角度讨论了改善叠层封装器件可靠性的方法．     

大功率LED加速寿命试验及问题分析

采用国家标准(GB1772)规定的电子元器件加速寿命试验方法,选择了工作环境温度作为加速应力,设计了四个应力等级的大功率LED加速寿命试验方案并进行试验.试验结果为每个应力等级下的失效模式有2～3种,不同应力级别确定的激活能有一定的差异.通过对金丝引线球焊处开裂、金属化层失效等主要失效机理的产生原因以及温度、电流密度之间关系分析,认为基于Arrhenius模型进行大功率LED加速寿命试验存在不足和缺陷,不能准确地预测稳态温度下的LED寿命,应当对Arrhenius模型进行修正.     

体内异常热源参数与体表温度关系的热像研究

人体内异常热源的位置信息在体表上表现为对应部位温度较高。体表温度可以通过医用红外热像仪摄取,这是诊断体内异常热源的方法之一。但是其摄取的体表温度分布并不能直接反应体内异常热源位置等信息,因此对热源深度、温度、热物性等参数与体表温度分布之间相互关系的研究是非常必要的。该文基于生物热传导方程,通过建立有限元模型,仿真分析了体内热源参数对体表温度分布的影响;将研制的温度可调的恒温热源埋于分层生物组织内,并以红外热像仪摄取各层生物组织的温度,给出体内、体表温度场的分布,对理论仿真结果进行实验验证。研究结果表明,体表温度分布与体内热源深度的关联性最大,为体内异常热源诊断的热像技术研究提供理论与实验依据。     

A Study on Thermal Performance of Heat Pipe for Optimum Placement of Satellite Equipment

A study on the operation of a heat pipe with two heat sources has been performed to optimize the heat distribution of satellite equipment. A numerical modeling is used to predict the temperature profile for the heat pipe assuming cylindrical two-dimensional laminar flow for the vapor, and the conduction heat transfer for the wall and wick. An experimental study using the copper-water heat pipe with the length of 0.45 m has been performed to evaluate the numerical model and to compare the temperature distribution at the outer wall for the non-uniform heat distribution. The results on temperature profiles for the heat input range from 29 W to 47 W on each heater are presented. Also the correlation between the heat input and the temperature increase is presented for the optimum distribution on two heaters. The result shows that the outer wall temperature can be controlled by redistribution of heat sources. It is also concluded that the heat source closer to the condenser can carry more heat while maintaining lower temperatures at the outer wall.     

基于体热源的激光透射焊接PA66温度场模拟

目前国内激光透射焊接温度场模拟大多采用面热源,无法考虑炭黑含量的影响。为此,文中使用Ansys的APDL语言构建了基于体热源的三维瞬态有限元模型,采用该模型对PA66的激光透射焊接温度场进行了模拟,并将模拟结果与面热源下的模拟结果、实验结果分别进行对比。结果发现,由体热源模型模拟得到的焊缝热影响区形貌与实际热影响区形貌较为接近,模型预测的热影响区尺寸也与实测值保持着较高的吻合度,表明体热源能较好地表征炭黑含量对焊接结果的影响,并在温度场模拟方面明显优于面热源。     

激光照射有血流散热组织的一维瞬态温度分布函数研究

研究激光热源在有血流散热的生物组织中形成的一维瞬态温度分布函数 ,适合于组织温度在热凝之前的传热过程。本文采用数学物理方程的定解求法解一维热传导偏微分方程 ,讨论结果的物理意义。结果表明 :当 μ >αh 时 ,激光热源在一维生物组织空间引起的温升一般随时间呈指数形式增大 ;而随与激光照射处的距离呈指数形式减少 ;当 μ <αh 时 ,组织空间任意点处的温升虽然随时间增大 ,但最终将趋于恒定值。     

Multidisciplinary Placement Optimization of Heat Generating Electronic Components on a Printed Circuit Board in an Enclosure

A multidisciplinary placement optimization methodology for heat generating electronic components on a printed circuit board (PCB) subjected to forced convection in an enclosure is presented. In this methodology, thermal, electrical, and placement criteria involving junction temperature, wiring density, line length for high frequency signals, and critical component location are optimized simultaneously using the genetic algorithm. A board-level thermal performance prediction methodology based on channel flow forced convection boundary conditions is developed. The methodology consists of a combination of artificial neural networks (ANNs) and a superposition method that is able to predict PCB surface and component junction temperatures in a much shorter calculation time than the existing numerical methods. Three ANNs are used for predicting temperature rise at the PCB surface caused by a single heat source at an arbitrary location on the board, while temperature rise due to multiple heat sources is calculated using a superposition method. Compact thermal models are used for the electronic components thermal modeling. Using this optimization methodology, large calculation time reduction is achieved without losing accuracy. To demonstrate its capabilities, the present methodology is applied to a test case involving multiple heat generating component placement optimization on a PCB.     

Performance characterization of a novel flat plate micro heat pipe spreader

A combined numerical and experimental investigation was conducted on a novel flat plate micro heat pipe spreader, to better understand the effect of primary operating parameters governing the performance of such devices. A numerical thermal model was developed to predict the temperature response with variation in the leading geometrical, material and boundary parameters of the spreader, viz. wall thickness, thermal conductivity, power input and heat source size. The results showed that, unlike conventional heat pipes, wall thermal conductivity is a major factor in such thin, flat spreaders. The spreader performance also degrades with decrease in heat source size. Visualization experiments have been conducted to qualitatively understand the heat transfer phenomena taking place on these devices. These confirmed that the primary limitation to heat transfer from these devices was due to the capillary limitation of the wick structures.     

Influence Coefficient Method for Calculating Discrete Heat Source Temperature on Finite Convectively Cooled Substrates

A simple method is developed for predicting discrete heat source temperatures on a finite convectively cooled substrate. The method is based on the principle of superposition using a single source solution for the mean or maximum contact temperature of an eccentric uniform heat source on a rectangular substrate. By means of influence coefficients, the effect of neighboring source strength and location may be assessed. It is shown that the influence coefficients represent localized thermal resistances, which must be weighted according to source strength. For a system of$N$heat sources, there exists$N$effects of source strength and position on any one heat source. This includes a self effect (source of interest) and$N$$-$1 influence effects (neighboring sources). The method is developed for isotropic, orthotropic, and compound systems. Convection in the source plane is addressed for isotropic and orthotropic systems. Expressions are developed for both mean and centroidal temperature.     

红外加热吸附反应外延系统的温度均匀性研究

为指导全新的吸附反应外延技术ARE(Absorption Reaction Epitaxy, ARE)设备红外热源的设计,分析在真空腔室中红外管阵列的热流分布。通过对灯管阵列灯管数量、灯管间距、灯阵与硅片之间距离等设计参数。采用COMSOL Multiphysics软件进行仿真模拟,研究了以红外为热源的设备腔室及硅片温度场分布情况,实测硅片表面温度及均匀性与仿真基本吻合。结果表明在保证源在硅片表面良好扩散效果的同时,当灯管阵列灯管长度为200 mm,数量为11根,间距10 mm,距离硅片15 mm时硅片表面温度不均匀度达到0.683%,满足红外加热吸附反应外延工艺需求,可为ARE红外热源及腔室设计提供参考。     

基于高斯型点扩展函数的红外图像热源复原

为了复原红外图像的热源,采用高斯点扩展函数的方法来增强热源的清晰度和对比度。首先,确定热源图像的高斯点扩展函数,建立其退化模型;然后,采用维纳滤波的方法复原红外图像中的热源,对复原图像通过YIQ变换来复原其温度场彩色信息;最后,通过边缘锐度和标准差评价分析热源复原的质量,并与盲复原算法对比。结果表明,边缘锐度边缘锐度和标准差分别提高了0.502%和0.124%。基于高斯型点扩展函数的方法对红外图像的热源复原具有明显的效果。     

基于红外测温的内部点热源的识别

基于表面测温的内热源识别问题在红外无损检测、微生物发酵、弹药和食物存储等领域都有重要的应用.利用遗传算法对导热反问题中热源项的反演问题进行了识别研究,系统地分析了多种因素对热源参数识别结果的影响.通过具体算例的求解,证明了该方法可以很好地解决内部点热源参数识别的问题.同时识别多个点热源的强度和位置时,结果都比确;在测温信息减少到依靠一边测温时,仅有远处的点热源的位置识别结果出现偏差;在测温误差的差不超过1.0℃时,热源强度和位置的识别结果都确的.