动圈式扬声器温度失效仿真

常态下测量了典型小功率动圈式扬声器的静态参数,根据Small小信号参数建立了扬声器温度失效模型;结合VisualC 和Matlab计算机语言的优势,编制了相应的仿真软件;对给定动圈式扬声器中可能出现的音圈短路、功率过载和意外结构性故障进行了计算机仿真,结果表明,封闭工作区间内温度急剧升高是导致扬声器失效的主要原因,与有限元模型计算结果相比较,最大误差分别为2.63%(16W,纸骨架)和3.36%(16W,铝骨架)。     

波峰焊焊点有限元模型的建立与分析

焊点在热循环服役条件下的力学行为分析是研究互连焊点失效机制的可行手段.采用MSC.MARC2000/MENTAT2000建立波峰焊焊点可靠性分析有限元模型,利用有限元计算软件Surface Evolver来对模型进行求解,研究三维空间中由重力、表面张力和其它形式的外力作用下的液体表面的成型问题.通过对典型插装元器件波峰焊焊点建立有限元分析的力学模型和在热循环载荷下应力应变过程,分析焊点内部力学参量和应力场的分布特征,结合通孔波峰焊点的热冲击可靠性测试结果,以此研究焊点失效机制.     

基于状态变量分析法的扬声器非线性测试

迄今为止的所有技术都不能动态地测量换能器的某种特定的非线性，并定量地分析其对总失真的影响。失真分析的核心内容是对换能器的非线性进行识别。德国克立佩尔公司成立于1997年。克立佩尔博士研究扬声器15年，建立了扬声器的大信号模型和扬声器非线性的系统识别技术，奠定了对非线性失真进行数字补偿的基础。电动扬声器在大振幅下的表现是不能用线性模型来描述的。     

NMOS管热载流子衰退效应评价模型及寿命预测方法研究

热载流子是器件可靠性研究的热点之一.特别对于亚微米器件,热载流子失效是器件失效的一个最主要方面.通过对这种失效机理及其失效模型的研究,为设计和工艺提供帮助,从而有效降低由热载流子引起的电路失效,提高电路可靠性.本文主要针对几种典型工艺的栅氧厚度(例如:Tox分别为150 (A)、200 (A)、250 (A))的NMOSFET进行加速应力实验,提取寿命模型的相关参数,估算这些器件在正常工作条件下的寿命值,对亚微米工艺器件寿命进行快速评价.     

扬声器非线性失真的分析与改进

扬声器单元非线性失真是影响扬声器单元重放品质的最重要的因素之一。介绍了扬声器单元非线性失真产生的原因,并针对扬声器单元的磁路及其零部件设计提出了改进方法。     

扬声器的发热机理及其热保护

音圈发热是引起扬声器损坏和失效的主要原因,也是限制扬声器功率承受能力的主要因素。由于电输入和总热阻的增大而使发热增加,总热阻取决于几种热转换机理,包括热传导、热辐射、对流和热的积存。本文分析了有关的因素并提出了两种热保护电路。     

动圈扬声器损坏限制上限功率及寿命分布研究

分析了动圈扬声器的损坏机理和失效类型,通过一系列扬声器的功率试验,提出了扬声器的寿命分布模型,并讨论了扬声器损坏限制的上限功率。     

高音、微型及号筒扬声器单元的大信号性能

高频信号专用扬声器可能产生明显的声学输出失真。磁路策动力和悬吊的非线性可用等效电路来建立模型,也可用基于电压和电流监测的系统识别技术动态地测量。被认可的模型是大信号性能数值预报的基础．同时该模型也揭示出每个非线性的影响。将该技术用于3个不同单元的诊断,比较了测量的和预报的失真。研究了热功率压缩并讨论了对感知音质的影响。     

金刚石厚膜热残余应力三维模拟及失效分析

运用ANSYS软件建立了三维轴对称有限元模型,对金刚石厚膜(φ40mm×1mm)内部和膜/钼基体界面处的热残余应力各个分量的分布作了全面的模拟,讨论了热残余应力对金刚石厚膜失效的影响.结果表明,金刚石厚膜内的热残余应力各个分量并非均匀分布,离界面越近,其值越大;界面处大的轴向拉应力和剪应力对于厚膜从基体上脱落有重要影响;在膜的上表面靠近外边缘局部区域内存在较大的径向拉应力和轴向拉应力,是造成膜开裂失效的原因;本文的三维有限元模型比以往的一维解析模型更全面,且能更合理地解释金刚石膜的失效现象.     

复合材料层合板渐进损伤分析与试验验证

文章基于能量耗散的渐进损伤分析方法,建立了复合材料层合板的三维有限元模型。采用了带剪切非线性的修正三维Hashin准则作为单元失效判据,使用Linde模型对失效单元进行材料性能退化。通过编写用户自定义材料子程序(UMAT),实现了失效准则与材料退化准则在Abaqus中的应用。并通过试验对有限元模型进行了验证,仿真误差为7.8%。仿真分析得到的失效位置与失效模式和试验一致,表明文章模型能合理有效地进行层合板的强度预测和失效分析。     

Nonlinear model reduction strategies for rapid thermal processingsystems

We present a systematic method for developing low order nonlinear models from physically based, large scale finite element models of rapid thermal processing (RTP) systems. These low order models are extracted from transient results of a detailed finite element model using the proper orthogonal decomposition (POD) method. Eigenfunctions obtained from the POD method are then used as basis functions in spectral Galerkin expansions of the governing partial differential equations solved by the finite element model to generate the reduced models. Simulation results with the reduced order models demonstrate good agreement with steady state and transient data generated from the finite element model, with an order of magnitude reduction in execution time     

Simulating package behavior under power dissipation using uniformthermal loading

The thermomechanical behavior of electronic packages under power dissipation is simulated using uniform thermal loading. Two packages are studied, a large periphery leaded plastic quad flat pack (PQFP) package and a more compact plastic ball grid array (PBCA) package, both mounted on a printed circuit board (PCB). Experimentally verified linear elastic finite element models are used to find the displacements at the predicted failure location during power dissipation, and then during uniform thermal loading. The results for the two cases are then analyzed to find correlations between power dissipation levels and equivalent heating temperatures. One use of the results could be to replace power cycling fatigue tests with thermal cycling tests, For the packages studied, the results revealed that very little uniform heating is required to simulate the thermomechanical effects at the failure location resulting from power dissipation. Due to the prestrained state of the packages at room temperature, power dissipation decreases the expansion mismatch while increasing the thermal mismatch between package and PCB     

PBGA封装热可靠性分析

对PBGA封装体建立了有限元数值模拟分析模型。模型采用无铅焊点,完全焊点阵列形式。研究了封装体在经历IPC9701标准下的五种不同温度循环加载后,受到的热应力、应变,以及可能的失效形式。结果表明,焊点是封装体结构失效的关键环节,焊点所受应力大小与焊点位置有关。比较了不同温度循环下封装体的疲劳寿命。其结果为提高封装体的可靠性和优化设计提供了理论依据。     

Reliability analysis of 3D heterogeneous microsystem module by simplified finite element model

Analyzing the structural reliability of 3D heterogeneous microsystem modules is an important step in their development. The finite element models of such modules are simplified by simulating the complicated structure of MEMS (microelectromechanical systems) devices integrated into a single interposer. In this study, thermal stress and cycling analyses for different finite element models of 3D heterogeneous microsystem modules are investigated. The results of the thermal stress analysis reveal the values of the maximum von Mises stress in the finite element models, at the interface between the interposer and the microgyroscope, and in the microgyroscope spring. They also illustrate the advantages and disadvantages of the different fabrication models. Module reliability assessments are also obtained through a thermal cycling analysis, the results of which show that properly simplified models designed to reduce computation time benefit the reliability analysis. This study provides useful suggestions for manufacturing and reliability assessments of 3D heterogeneous microsystem modules embedded using the through-silicon via technique.     

大型四点接触球轴承的有限元模型研究

基于非线性有限元分析方法 ,采用了线性轴承模型和非线性轴承模型分析了大型四点接触球轴承的变形和受力。两种模型的分析结果表明 :整体应力、应变分布和轴承外环的变形规律基本一致 ,证明了两种建模方法在一定程度上是可行的。讨论了引起非线性模型和线性模型之间差异的原因。求解得到的轴承变形曲线为轴承的设计提供了理论依据 ,具有重要的工程应用价值     

Failure and stress analysis of through-aluminum-nitride-via substrates during thermal reliability tests for high power LED applications

The objective of this study is to evaluate the reliability of through-aluminum-nitride-via (TAV) substrate by comparing those experimental results with the finite element simulation associated with measurements of aluminum nitride (AlN) strength and the thermal deformation of Cu/AlN bi-material plate. Two reliability tests for high-power LED (Light emitting diode) applications are used in this study: one is a thermal shock test from − 40 °C to 125 °C, the other is a pressure cook test. Also, the strength of AlN material is measured by using three-point bending test and point load test. The reliability results show that TAV substrates with thicker Cu films have delamination and cracks after the thermal shock test, but there are no failure being found after the pressure cook test. The determined strengths of AlN material are 350 MPa and 650 MPa from three-point bending test and point load test, respectively. The measurement of thermal deformation shows that the bi-material plate has residual-stress change after the solder reflow process, also indicating that a linear finite element model with the stress-free temperature at 80 °C can reasonably represent the stress state of the thermal shock test from − 40 °C to 125 °C without considering Cu nonlinear effect. The further results of the finite element simulation associated with strength data of AlN material have successfully described those of the reliability test.     

激光辐照下旋转充压柱壳失效的数值模拟

建立了激光辐照下充压旋转柱壳热力学响应的物理模型和数值计算模型,求解了激光产生的非线性温度场。在此基础上,考虑塑性和屈服强度的温度相关性,求解了非线性的应力场,分析了柱壳裂纹萌生的可能位置和条件。通过计算发现,旋转充压柱壳在过光斑中心外表面圆周上有最大应力值这说明在过光斑中心的外表面环带区域将有可能最先发生破坏。激光辐照薄壁柱壳时有较高的温升其更容易发生破坏;旋转柱壳在过光斑中心圆周上应力分布随旋转频率增加而趋于均匀这是因为旋转频率增加激光辐照的环带区域温度分布更加均匀;在激光总能量相同条件下,小光斑辐照时易产生裂纹。     

倒装芯片焊点可靠性的有限元模拟法综述

随着集成电路封装技术的发展,倒装芯片技术得到广泛的应用。由于材料的热膨胀失配,使倒装焊点成为芯片封装中失效率最高的部位,而利用快捷又极具参考价值的有限元模拟法是研究焊点可靠性的重要手段之一。介绍了集成电路芯片焊点可靠性分析的有限元模拟法,概括了利用该方法对芯片焊点进行可靠性评价常见的材料性质和疲劳寿命预测模型。     

Finite element modeling on electromigration of solder joints in wafer level packages

This work studies the electromigration of solder joints in an encapsulated copper post wafer level package (WLP) by finite element modeling. Experimental data showed that the electromigration failure occurs in solder joints on the printed circuit board (PCB) side due to the current crowding. In order to improve the electromigration performance on the PCB side with a copper post WLP, two new line-to-bump geometry designs are proposed. Coupled electro-thermal finite element modeling is performed to obtain the electrical and thermal fields simultaneously. The ionic flux from electron wind and thermal response is calculated based on finite element solutions. The divergence of the total flux, which is the sum of the divergence of electromigration and thermomigration, is extracted at the critical locations in solder joints. Results show that the new proposed design structures can reduce the maximum current density by 19%, and the divergence of the total ionic flux by 42%. Thermal gradient is very small in solder joints, therefore, the main driving force for electromigration failures comes from the electron wind. The finite element results on mesh dependency are discussed in this paper.     

Compact thermal modeling for packaged microprocessor design with practical power maps

In this paper, we propose a new behavioral thermal modeling technique for high-performance microprocessors at package level. Firstly, the new approach applies the subspace identification method with the consideration of practical power maps with correlated power signals. We show that the input power signal needs to meet an independence requirement to ensure the model predictability and propose an iterative process to build the models with given error bounds. Secondly, we show that thermal systems fundamentally are nonlinear and then propose a piecewise linear (PWL) scheme to deal with nonlinear effects. The experimental results validated the proposed method on a realistic packaged integrated system modeled by the multi-domain/physics commercial tool, COMSOL. The new piecewise linear models can model thermal behaviors over wide temperature ranges or over different thermal boundary convective conditions due to different fan speeds. Further, the PWL modeling technique can lead to much smaller model order without accuracy loss, which translates to significant savings in both the simulation time and the time required to identify the reduced models compared to the simple modeling method by using the high order models.