HgCdTe探测器In焊凸点的失效及有限元分析

卫星工作时,由斯特林机致冷的HgCdTe中长波红外探测器会经受从-173℃以下到常温的成千上万次温度循环.由于不同材料的热膨胀系数(TEC)不匹配,这样就会造成电极封装的疲劳和失效,进而影响卫星的正常工作.利用中科院上海技术物理研究所研制的温度循环设备TCE-a,模拟了真空环境下的斯特林制冷机的开关机模式,发现了In焊凸点的两种失效模式.运用有限元方法,对In焊凸点的失效进行了力学分析.     

基于LabVIEW的低温半导体器件温度循环系统

为研究低温半导体器件如HgCdTe中长波红外探测器温度循环过程的失效机理,提出了一种基于LabVIEW的温度循环实验设备。LabVIEW既用于测试又用于步进电机等的控制,结构简单,运行高效。经过数千次温度循环实验表明,该设备运行比较稳定,能够满足对低温半导体器件的筛选要求。     

Pb90Sn10焊点硅基器件与PCB板组装的温循可靠性研究

采用有限元仿真和实验两者相结合的方法,对-40～70℃使用环境下的Pb₉₀Sn₁₀焊点硅基器件与PCB板组装的组件,选择-55～85℃温度循环条件进行可靠性分析和研究。Anand模型仿真分析焊点在温循下应力应变行为,提取模型焊点在最后一个温度循环结束时的等效塑性应变分布并进行分析,确定最易发生热疲劳失效的关键焊点和关键位置。基于Coffin-Manson方程对热循环条件下焊点的服役寿命和失效模式进行预测。仿真结果表明焊点失效机理为热疲劳失效,失效模式为焊点开裂,失效循环周期为3 984 cycles。实验表明：温度循环500次,未出现焊点裂纹、空洞等缺陷;温度循环2 000次后焊点形貌由球形变为椭球形,焊点未出现明显缺陷。     

用显微红外热成像技术分析功率器件可靠性

利用显微红外热成像技术对功率器件进行热可靠性分析。先从理论上阐述了显微红外热成像技术的原理,进而尝试利用该技术进行微波功率器件可靠性筛选工作,通过分析获取了显微红外图像中的温度分布和峰值温度,大大提高了器件可靠性筛选工作的准确性。在功率器件失效分析方面,利用显微红外热成像技术对发生失效的器件进行热成像和分析,通过定位失效点找到器件发生失效的原因。另外,还利用该技术来验证器件热设计的成功与否,通过显微红外热成像获取的温度信息如峰值温度、温度分布等来判断器件的热设计是否符合要求,在实际的器件设计过程中起到了良好的效果。     

PBGA器件焊点的可靠性分析研究

根据PBGA器件组装特点,分析了器件焊点的失效机理,并针对实际应用中失效的PBGA器件在温度循环前后,分别使用染色试验、切片分析、X-射线分析等方法进行失效分析.分析结果显示样品PBGA焊点存在不同程度的焊接问题,并且焊接质量的好坏直接影响器件焊点抵抗外界应变应力的能力.最后,开展了PBGA器件焊接工艺研究和可靠性试验,试验结果显示焊接工艺改进后焊点的可靠性良好.     

塑封器件失效机理及其快速评估技术研究

针对影响塑封器件可靠性的五种失效机理,即腐蚀失效、爆米花效应、低温/温冲失效、闩锁以及工艺缺陷等方面进行分析和讨论,并提出利用高温潮热和温度冲击试验对塑封器件的可靠性进行评估.还介绍了美国航天局Goddard空间飞行中心提出的对塑封器件进行高可靠性筛选的方案.     

非硅MEMS惯性开关可靠性研究

非硅MEMS惯性开关具有体积小、成本低、可批量生产以及强度和导电性能较好的优点,但其可靠性问题制约了其应用领域。通过开展非硅MEMS惯性开关的可靠性实验(包括温度循环实验和随机振动实验),找出其主要失效模式为分层。通过对失效部位进行分析,并利用有限元方法分析器件上的应力分布,研究了相应的失效机理。研究结果表明:引发惯性开关分层失效的主要原因是层间产生疲劳效应,温度循环应力会使惯性开关各层间由于热膨胀系数失配而产生疲劳,而振动应力则直接加载在惯性开关上而使其产生疲劳;惯性开关中铬层与铜层之间最易发生失效,而分析表明该层间界面处热应力最大;经历温度循环实验和振动实验的惯性开关相较只经历一种实验的样本更容易失效,进一步说明了温度循环应力会使开关层间发生疲劳,而振动应力则会引起应力集中而加速分层失效。     

基于ANSYS的IGBT模块的失效模式

功率循环(PC)试验和温度循环(TC)试验是对绝缘栅双极型晶体管(IGBT)模块进行可靠性考核的两个基本试验,可以有效暴露出器件封装所存在的问题。基于ANSYS有限元分析软件,分别研究了IGBT模块在功率循环和温度循环两种不同的试验情况下的温度分布与应力、应变分布的情况。研究表明在这两种情况下IGBT模块的失效模式是不同的。功率循环条件下器件的温差较小,但温度、应力往往集中分布在引线键合点及其下方,一般失效会发生在引线键合点处。而温度循环下温度分布均匀,但高低温温差较大,更能考察器件在严酷的环境条件下的可靠性,由于每层结构的边缘位置处剪切应力较大,失效常常由每层结构的边缘部位开始,一般会发生芯片和陶瓷基板的断裂和焊料层疲劳等失效现象。     

CBGA器件焊点温度循环失效分析

陶瓷球栅封装阵列(CBGA)器件的陶瓷器件与印制电路板之间热膨胀系数的差异是导致焊点失效的主要因素,其可靠性一直是CBGA封装器件设计时需重点考虑的问题[1].对CBGA植球器件的板级表贴焊点在-55～105 ℃温度循环载荷条件下的失效机理进行了研究,结果表明,CBGA板级表贴器件的焊点的主要失效部位在陶瓷一侧焊料与焊球界面和焊点与焊盘界面两处,边角焊点优先开裂,是失效分析的关键点;随着循环周期的增加,内侧链路依次发生断路失效.     

MEMS加速度计可靠性评价技术

MEMS加速度计是动作识别设备、姿态控制设备等电子设备的核心器件,其功能失效会严重影响设备的可靠性。而目前国内外还没有MEMS器件的可靠性实验标准,这在一定程度上制约了MEMS加速度计的应用与发展。针对该现状,深入研究了MEMS加速度计敏感部件的失效模式及失效机理,得到了典型环境应力与器件失效的关系,分析了加载环境应力可能导致器件失效的环境实验,并选取了相应的MEMS加速度计产品进行了可靠性实验验证,得出了MEMS加速度计可靠性评价的初步试行方案。     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

中国建立EB级存储实验室,致力云计算应用(英文)

正With the support of 863 programs,Sugon Information Industry Co.,Ltd.,set up a dawning EB-class storage laboratory to address massive data storage requirements and largescale cloud computing demonstration applications.The Dawning EB-class cloud storage system adopts advanced fault-tolerant architecture,efficient data fault-tolerant algorithms with user authentication and data encryption policies to deal with the"lost""wrong"and"stolen"problems of data for ensuring the reliability and safety of the EB-class storage system in the public network application environments.The Dawning EB-class Storage Laboratory taking advan-