MEMS微加速度计在振动环境下的可靠性研究

由于微加速度计的可靠性成为其产品商业化过程中的一个重要问题,而冲击断裂是导致其性能失效的主要原因。主要研究了压阻式微加速度计在振动环境下的可靠性问题。设计了微加速度计在振动环境下的可靠性试验并通过ANSYS进行仿真。经过分析得出微加速度计在振动环境下的主要失效模式,并进行了相应的失效机理分析。通过可靠性实验进行了验证,对微加速度计在振动环境下的可靠性进行评估,并描绘了其可靠度与失效概率曲线。     

基于退化量分布的高量程MEMS加速度计的可靠性评估

高量程MEMS微加速度计主要应用于航空、航天及军工等高可靠性要求的惯导领域。为了更好进行微加速度计的可靠性寿命预测,提出一种基于退化量分布,以实验数据拟合推导出分布模型参数的变化关系从而更加准确的评估微加速度计的可靠性寿命。实验研究结论表明采用新的评估方法能够获得更准确的微加速度计可靠性预测。     

MEMS低量程微加速度计的设计

在传统双边四梁微加速度计结构的基础上,设计了一种新型MEMS低量程微加速度计,量程为±10 g。用ANSYS有限元软件对加速度计的结构建立仿真模型,进行应力、模态及抗冲击能力分析。加速度计供电电压为5 V时,灵敏度理论值达到1.029 mV/g,与传统结构相比,极大地提高了低量程微加速度计的灵敏度。     

灌封胶封装对高量程MEMS加速度计动态性能的影响

利用有限元模拟方法,对一种压阻式高量程MEMS加速度计进行了10万g峰值的半正弦加速度脉冲下的响应分析.灌封胶弹性模量的变化对高量程加速度计输出电压信号的影响可以忽略,且模拟输出电压的峰值与解析解接近.应力分析表明,芯片粘结胶、芯片与芯片盖板之间封接胶环的等效应力均随灌封胶弹性模量的增加而减小;弹性模量在4GPa以上的灌封胶适宜用来保护芯片.动态有限元模拟结果与自由落杆测试结果接近.     

复合量程微加速度计动态特性分析

介绍一种复合量程微加速度计.并分析其加速度计的阻尼比、幅频特性和相频特性.计算出其工作的频响范围.对加速度计的动态特性进行测试.对比分析理论计算结果与测试结果,验证该复合量程加速度计满足设计要求,可以有效地工作在4个量程范围内.     

灌封胶封装对高量程MEMS加速度计动态性能的影响

利用有限元模拟方法,对一种压阻式高量程MEMS加速度计进行了10万g峰值的半正弦加速度脉冲下的响应分析．灌封胶弹性模量的变化对高量程加速度计输出电压信号的影响可以忽略,且模拟输出电压的峰值与解析解接近．应力分析表明,芯片粘结胶、芯片与芯片盖板之间封接胶环的等效应力均随灌封胶弹性模量的增加而减小;弹性模量在4GPa以上的灌封胶适宜用来保护芯片．动态有限元模拟结果与自由落杆测试结果接近．     

MEMS及微机械加速度计可靠性研究

由于MEMS器件的应用日益频繁,其可靠性研究就显得十分重要。介绍了引起可靠性问题的原因。以微机械加速度计为例,指出了该加速度计的可靠性问题,以及对其可靠性测试研究的内容。     

复合量程微加速度计动态特性分析

介绍一种复合量程微加速度计,并分析其加速度计的阻尼比、幅频特性和相频特性,计算出其工作的频响范围。对加速度计的动态特性进行测试,对比分析理论计算结果与测试结果,验证该复合量程加速度计满足设计要求,可以有效地工作在4个量程范围内。     

微加速度计在冲击环境下的力学分析与仿真

微加速度计用于测量载体的加速度,并提供相关的速度和位移信息。该文主要对一种硅基压阻式高加速度g(g=9.8m/s2)值微加速度计在冲击加速度环境下进行有限元仿真分析。分析结果表明,所设计的压阻式高g值微加速度传感器在15×104 g量程内可正常并有效工作,且可承受40×104 g高速冲击,当加速度超过40.8×104 g时,加速度计发生失效变形。分析了加速度计在冲击环境下的主要失效模式及失效机理,得出了压阻式加速度计在冲击环境下的失效主要从梁与边框和质量块连接处开始,随着冲击时间(即冲击强度)的增加,结构应力逐渐达到屈服极限,材料发生屈服效应,然后发生断裂。     

高量程加速度计横向各向异性响应的自由落杆冲击评估法（英文）

采用自由落杆冲击法对悬臂梁型高量程加速度计(50 000g)的横向响应进行研究。钢杆和铝合金杆作为冲击体与地面上放置的金属钢砧碰撞产生应力波作为激励源,用于表征加速度计的性能,其中加速度计固定在金属杆的顶端。该方法不仅可以测量加速度计敏感轴的灵敏度,同时也可以测试其横向响应。实验表明,加速度计的各向异性响应与加速度计的固有结构和冲击体的直径紧密相关,理论计算与实验结果相一致。     

无掩膜腐蚀与伺服型电容式微加速度计

为了解决“三明治”这类微器件制作的深窄槽结构成型问题,运用无掩膜湿法腐蚀技术,成型悬臂梁雏形后再成型质量块,较好地实现了悬臂梁与质量块同时准确成型,研制出±70g和±5g两种不同量程的微加速度计。样品测试表明,利用这项技术所制作的微加速度计相对精度皆优于1×10^-4。其中,±70g量程的残差可控制在7mg以内,非线性可达0．02％;±5g量程的残差在0．4mg左右。     

批量化微加速度计综合测试平台设计

为了实现微加速度传感器批量标定的测试,能够更加方便地进行多个传感器的性能测试。基于SolidWorks软件平台设计了一种可一次进行多只传感器综合测试装置。该装置可分别进行翻转测试和振动测试,并且能够实现传感器测试夹具与测试平台的自动结合与分离。通过对用该装置测试的加速度计参数和原厂标定的加速度计参数对比表明,该测试平台的测试结果可靠。     

Reliability enhancement by time and space redundancy in multistageinterconnection networks

The authors present the dynamic full access (DFA) properties of fault tolerant multistage interconnection networks (MINs) which have multiple connections to the inputs and outputs, and thus potentially no hardcore. When full access is lost due to multiple faults, but DFA exists, multiple pass routing could be utilized to achieve graceful degradation. Some efficiency conditions for the existence of DFA in a broad class of fault tolerant MINs are derived. The reliability of four multiple path MINs under DFA is studied. The metrics used are the probability of existence of DFA and the mean time to failure. One particular network (the MD-Omega), which uses a minimum amount of hardware redundancy to provide two connections from each source to the MIN and to each destination from the MIN, shows the most gain in reliability when time redundancy is used. The MD-Omega network has a 2×2 switch as its basic element, but is almost as reliable as another fault tolerant MIN, the ASEN, which uses a 3×3 element, when multiple pass routing is used     

基于微加速度计的无线教鞭的设计

为弥补多媒体教学中激光笔的不足,提出了一种基于微加速度计的无线教鞭系统,它不仅具有激光笔上下翻页的功能,而且能在空中自由灵活移动实现高精度点击的功能,该系统以微加速度计ADXL345作为信号检测元件,并采用低功耗低成本微控制器AT89S52和RF芯片nRF24L01进行信息处理与无线传输,符合人体工程学设计,最大限度地满足人们使用鼠标时在手感以及舒适度和使用习惯方面的要求。     

Reliability enhancement of electronic packages by design of optimal parameters

Reliability growth testing involves the selection of optimal design parameters to enhance a product's reliability. This paper proposes a split plot experimental design that accommodates the restriction on randomization on the order of experimental runs caused by the experimental nature of accelerated reliability testing. The proposed experimental design provides statistically relevant solutions about the choice of design parameters, in terms of their reliability impact, in a much shorter time. A degradation model that aids in predicting the failure time for the given problem further supplements this discussion.     

Reliability enhancement of zinc oxide varistors using sputtered silver electrodes

Zinc oxide (ZnO) varistors, which are produced by sintering ZnO powder together with small additives of Bi₂O₃, Co₃O₄, Sb₂O₃ and other oxides, are popular ceramic semiconductor devices and widely used in electric circuits and systems as voltage-clamping or surge-arrester owing to their extremely nonlinear current–voltage characteristics. The reliability of ZnO varistors is the most important consideration, and researches are mainly focus on the material properties of ZnO body and the effects of additives, such as ZnO grain size and the surrounding additive-rich insulating barriers. However, the manufacturing of electrodes still remains the traditional silver baking process, and few people investigate the effects of electrodes on the reliability of devices. In this paper, we propose a novel electrodes manufacture process using magnetron sputtering technology, and investigate the reliability of devices comparing to silver baking process. Two groups of samples with diameters of 20 mm were prepared by silver baking and magnetron sputtering process respectively. The nonlinear voltage, nonlinear coefficient, and leakage current parameters were measured by the metal oxide varistor meter typed TTK-168; the energy absorption capacities were measured by a lightning current surge generator with 8/20 μs impulse waves; the adhesive strength of electrodes was measured by a dynamometer; the microstructures of the samples were examined using Scanning Electron Microscope, and the change ratio of nonlinear voltages at an environment of 125 °C after 100 h was chosen as the main reliability parameter. Results show that the sputtered electrodes could improve the reliability of samples by reducing the change ratio from 1.32% to 0.61%, with other parameters exceeding the silver baking samples at the same time. This enhancement is benefit from the good interface between sputtered electrodes and ZnO substrate as well as the low temperature during magnetron sputtering process.     

Reliability enhancement of digital combinational circuits based on evolutionary approach

Reliability has become an integral part of the system design process, especially for those systems with life-critical applications such as aircrafts and spacecraft flight control. The recent rapid growth in demand for highly reliable digital circuits has focused attention on tools and techniques we might use to enhance the reliability of the circuit. In this paper, we present an algorithm to improve the reliability of digital combinational circuits based on evolutionary approach. This method generates a global VHDL file for the selected initial set of components based on inserting multiplexers at the gate inputs of the circuit which helps to perform the simulations in only one session. This simulation framework is combined with single-pass reliability analysis approach to implement the evolutionary algorithm. The search space of the genetic algorithm is limited by the idea of slicing the initial set of components and also circuit partitioning could be used to further overcome the scalability limitations. The framework is applied to a subset of combinational benchmark circuits and our experiments demonstrate that higher reliabilities can be achieved while other factors such as power, speed and area overhead will remain admissible.     

Reliability and performance of a true enhancement mode HIGFET for wireless applications

Freescale’s true enhancement mode (EMODE) HIGFET is a high performance single supply technology used for wireless power amplifiers. It is the first technology of its kind to be produced in a high volume manufacturing environment. The EMODE HIGFET intrinsic reliability was evaluated using a conventional three temperature DC accelerated stress test. The device used for these tests has a total gate width of 0.6 mm, a gate length of 0.8 μm, and a die thickness of 3 mils. The device has no through-wafer vias, is representative of the unit cell for larger devices, and was processed using a production mask set.For targeted applications with a system life of 5 years, the first expected failure at 150 °C for the 1 ppm level was determined to be 82 years at a 90% lower confidence level, which exceeds the reliability requirements for subscriber unit power amplifiers by a wide margin. This work demonstrates that EMODE HIGFET devices are high performance RF devices with intrinsic reliability well in excess of anticipated system requirements.     

Reliability enhancement with the aid of transient infrared thermal analysis of smart Power MOSFETs during short circuit operation

The usage of novel measurement techniques enhances the capabilities of researchers and power device manufacturers to understand and address reliability problems in novel Smart Power Devices. Along this line of argument, this work describes a method to improve the reliability of the smart Power MOSFET devices by design. The design optimization process involves Silicon layout, interconnections, packaging and protection strategy as well. Accurate thermal transient analyses, made possible by the unique features of a custom infrared radiometric microscope experimental setup which allows dynamic temperature detection with a bandwidth of 1 MHz over the chip area, indicated the way to minimize peak temperature and to verify the effect of the optimization.     

Non linear response and optimization of a new z-axis resonant micro-accelerometer

Micro-Electro-Mechanical Systems (MEMS) accelerometers are micro-sized devices largely used for detecting accelerations in the consumer and automotive market. Both capacitive and resonant sensing have been successfully employed in these devices.In the present work, the focus is on a z-axis resonant accelerometer recently proposed in [1] and fabricated with the Thelma^© surface-micromachining technique developed by STMicroelectronics [2].After a full non-linear dynamic study, two possible optimized designs are studied through an optimization procedure. The goal of the work is to find a novel design for the z-axis resonant accelerometer which meets the linearity and the reliability requirements for MEMS accelerometers whitout losses in terms of sensitivity.