MEMS器件真空封装模型模拟

结合典型的MEMS器件真空封装工艺,应用真空物理的相关理论,建立了MEMS器件真空封装的数学物理模型,确定了其数值模拟算法。据此,对一封装示例进行了计算,获得了真空回流炉内干燥箱及密封腔体真空度的变化情况,实现了MEMS器件真空封装工艺过程的参数化建模与模拟。     

Characterization of intermediate In/Ag layers of low temperature fluxless solder based wafer bonding for MEMS packaging

Low temperature fluxless solder for wafer bonding has received a lot of attention due to its great potential in hermetic MEMS packaging. Previous research activities mainly deploy solder alloy of eutectic composition to achieve low bonding temperature. We proposed new intermediate bonding layers (IBLs) of rich Ag composition in In–Ag materials systems. In this study, we investigated the intermetallic compounds (IMCs) at the bonding interface with respect to the bonding condition, post-bonding room temperature storage and post-bonding heat treatment. With this IBL, the IMCs of Ag₂In and Ag₉In₄ with high temperature resist to post-bonding process are derived under process condition of wafer bonding at 180 °C, 40 min and subsequent 120–130 °C annealing for 24 h. Low melting temperature IMC phase of AgIn₂ is formed in the interface after long term room temperature storage or 70 °C aging treatment. This low melting temperature IMC phase can be completely converted into high melting temperature IMCs of Ag₂In and Ag₉In₄ after 120 °C additional annealing. Based on our results, we can design the packaging process flow so as to get reliable hermetic packaged MEMS devices by using low temperature fluxless In–Ag wafer bonding.     

基于钎焊的MEMS陀螺真空封装设计与实验研究

对于线振动硅微机电系统(MEMS)陀螺,真空封装是减小其振动阻尼、提高振动品质因数,进而提高性能的一种有效的措施。设计了一种基于钎焊的硅MEMS陀螺真空封装方案,该方案因不采用吸气剂,故可实现真空度可控。理论计算表明:该封装形式可以保持1 Pa以下的真空度;经过对真空封装后的陀螺实验测试结果表明:设计的陀螺驱动轴品质因数为1500,实际封装后的陀螺驱动轴品质因数为1700,满足真空度设计目标。经过对封装后的陀螺品质因数进行186 d的跟踪测试,品质因数基本保持不变,验证了该真空封装方案的可靠性。     

高量程MEMS加速度计封装工艺研究

对一种先进的双悬臂梁高量程MEMS加速度计的单芯片封装工艺进行了失效机理分析。手工粘贴芯片盖板可靠性不高,加速度计失效是由于胶粘剂(粘贴胶或灌封胶 )从芯片盖板和芯片的间隙流淌进入悬臂梁的过载保护间隙,阻碍了悬臂梁的摆动。高量程加速度计采用单芯片封装方法时,存在芯片正面和背面保护的可靠性问题,更好的封装方法是采用圆片级封装。黑胶不适宜用作加速度计的贴片胶,至少使用聚酰亚胺膜作背面保护时如此。     

MEMS封装技术

介绍了微机电(MEMS)封装技术,包括晶片级封装、单芯片封装和多芯片封装、模块式封装与倒装焊3种很有前景的封装技术。指出了MEMS封装的几个可靠性问题,最后,对MEMS封装的发展趋势作了分析。     

微机械陀螺封装应力研究

针对设计的微机械陀螺开展了封装应力影响的研究.在对陀螺封装影响进行理论计算分析的基础上,进行了有限元仿真分析,并分析了温度变化引起的不同结构梁的谐振频率的变化,结果表明:在封装应力的影响下,陀螺的谐振频率与温度存在线性关系,不同梁结构的线性增减是不同的,基底材料和粘胶的热膨胀系数与杨氏模量是影响谐振频率变化的因素.     

MEMS封装技术研究进展与趋势

介绍了MEMS(microelectromechanicalsystems)封装技术的研究现状和存在的问题,重点介绍了倒装芯片技术(flip chiptechnology简称FCT)、上下球栅阵列封装技术和多芯片模块封装技术三种很有前景的封装技术的特点及其在MEMS领域的应用实例,并且对MEMS封装有可能的发展趋势进行了分析。     

Reliability of MEMS: A perspective on failure mechanisms,improvement solutions and best practices at development level

Reliability of MEMS (MicroElectroMechanical-Systems) devices is a crucial aspect as it can discriminate the successful from partially or totally missed reaching of Microsystem technology based market products. However, the topic of MEMS reliability is significantly articulated, as it comprises numerous physics of failure and diverse failure mechanisms. Thereafter, it requires a pronounced sensitivity related to the actual operation conditions (environmental and functional) of the Microsystem device within the final application. In other words, reliability of MEMS is nowadays regarded as a standalone transversal discipline that must be seriously taken into account already from the early design phase. The purpose of this paper is to provide the reader at first with basic knowledge around the concept of reliability. Thereafter, the most relevant physics of failure and failure mechanisms typical of MEMS are grouped and briefly discussed, with specific attention to their employment in the field of displays. A synthetic review of valuable solutions to improve specific reliability aspects of MEMS devices for diverse applications is then proposed to the reader. Eventually, a brief discussion focused on best practices to address properly reliability during the whole development chain of innovative MEMS based products completes the contribution. It is a belief of the author that the particular blend of topics and aspects reported in the following pages, as well as the attitude of considering reliability as a transversal discipline of science, contribute to provide this contribution with an important benefit if compared to the reviews on reliability of MEMS previously published in literature.     

Reliability and validity of self-reported assessment of exposure and outcome variables for manual lifting tasks: a preliminary investigation

The reliability and validity of self-reported assessment of exposure and outcome variables were examined for manual lifting activities among ten physiotherapists. In this study, the participants evaluated the effects of five lifting variables on perceived effort, twice separated by a one-week period. One hundred and sixty-two lifting conditions were evaluated by each subject. The exposure and outcome lifting variables were described in linguistic terms. Intra-class correlation coefficient (ICC(1,1)) analysis revealed a mean value of 0.62 for all lifting activities. The self-reported assessment was cross-validated with the NIOSH lifting index by mapping the linguistic variables into numerical ranges. Moderate correlations (r = 0.54 and 0.53, p<0.01) were obtained between perceived physical exertion/perceived risk and lifting index. The findings of this study provide preliminary indications that human-based methodologies may be further explored on experienced workers.     

Biomechanical analysis of upper trapezius,erector spinae and brachioradialis fatigue in repetitive manual packaging tasks: Evidence from Chinese express industry workers

This study aims to assess the effects of repetitive motion-induced fatigue during manual packaging on kinematics and muscle activity of the arm, back and shoulder. Eighteen participants performed a 60-min manual packaging task. Electromyography median frequency of RUT, RES, LES and RB decreased by 13.2% (p < 0.05), 12.8% (p < 0.05), 11.3% (p < 0.05) and 21% (p < 0.001), respectively over time. The head flexion and the right upper arm flexion angles significantly (p < 0.001) differed among different packaging sizes, and similar results were observed for left upper arm flexion and rotation. The trunk and pelvis angles significantly (p < 0.05) differed over time under three kinds of packaging. The results showed there was an increase in the rating of perceived exertion from 8.56 to 16.94 (p<0.01) during the task. The outcomes of this study indicate repetitive movements in the manual packaging task resulted in elevated prevalence of muscle discomfort in packaging workers, especially the right brachioradialis. Interventions such as specific work: rest ratios, workplace redesign should be explored to relieve muscle fatigue and discomfort.Relevance to industryFor workers performing repetitive manual packaging tasks, biomechanical analysis of different muscles groups can help in developing appropriate ergonomic interventions.     

Characterization and failure analysis of MEMS: high resolution optical investigation of small out-of-plane movements and fast vibrations

A high resolution optical tool is required to investigate the mechanical behavior and failure modes of micro-electromechanical systems (MEMS). We report on the possibilities of a newly developed optical characterization tool for MEMS devices. Both slow movements and fast mechanical vibrations up to 15 MHz can be monitored. The instrument can perform an imaging operation for a complete image at once by employing laser TV holography, which is a large advantage over scanning laser Doppler vibrometers. For vibration measurements, this new, interference based instrument uses a beat frequency between object excitation and reference beam excitation. A normal CCD camera is used to obtain 3D images and movies of periodic mechanical motions of MEMS devices. Excitation can be by means of a PZT, or by using electronic excitation. We show that the instrument is a very useful tool for the characterization and failure analysis of MEMS devices.The whole MEMS team at IMEC and their coworkers in projects are thanked for providing many of the samples shown in this paper. In particular, we would like to thank the following people. Melexis is thanked for providing the membrane sample of Fig. 4–6 and 14. Figs. 7–9 were measured in the frame of the MISTRA project (IWT contract 000167). Theo Rijks (Philips Natlab) provided the sample of Figs. 10 and 11. Chris Muhlstein sent the sample of Fig. 12 to us. Hans de Vries (Philips Centre for Industrial Technology/EP&A) is thanked for providing the sample of Fig. 13. The switch of Fig. 15 was made in the MIRS project (5012352345). Laurent Francis (IMEC) is thanked for providing the sample of Fig. 16. Sjoerd van de Geijn of Océ-Technologies B.V. provided the sample of Fig. 17.     

Reliability and validity of self-reported burnout in college students: A cross randomized comparison of paper-and-pencil vs. online administration

Internet data collection is becoming increasingly popular in all research fields dealing with human perceptions, behaviors and opinions. Advantages of internet data collection, when compared to the traditional paper-and-pencil format, include reduced costs, automatic database creation, and the absence of researcher-related bias effects, such as availability and complete anonymity. However, the validity and reliability of internet gathered data must be established, in comparison to the usual paper-and-pencil accepted formats, before an inferential analysis can be done. In this study, we compared questionnaire data gathered from the internet with that from the traditional paper-and-pencil in a sample of college students. The questionnaires used were the Maslach Burnout Inventory - Student Survey (MBI-SS), the Oldenburg Burnout Inventory (OBI-SS) and the Copenhagen Burnout Inventory (CBI-SS). Data was gathered through a within-subject cross randomized and counterbalanced design, on both internet and paper-and-pencil formats. The results showed no interference in the application order, and a good reliability for both formats. However, concordance between answers was generally higher in the paper-and-pencil format than on the internet. The factorial structure was invariant in the three burnout inventories. Data gathered in this study supports the Internet as a convenient, user-friendly, comfortable and secure data gathering method which does not affect the accepted factorial structures existent in the paper format of the three burnout inventories used.     

The effect of transportation suit induced heat stress on helicopter underwater escape preparation and task performance

Although essential in an emergency such as a helicopter ditching, mandatory survival suits worn by civilian personnel may lead to heat strain during a normal flight. To explore the possibility that wearing a helicopter transportation suit impairs emergency performance, 11 individuals completed underwater escape procedures immediately following a pre-recorded emergency announcement (randomly played between 50 and 90 min) in two ambient temperature conditions (Thermoneutral = 21 °C and Hot = 34 °C). Mean skin and rectal temperatures were recorded throughout the trials, while situation awareness and thermal sensation/comfort were recorded on completion of trials. Results indicate that although mean skin and rectal temperatures were significantly higher at the end of both trials, escape procedures were not impaired. It can therefore be concluded that although conditions inside an offshore transport helicopter are perceived as being hot and uncomfortable, no deficits in escape performance should be expected in the first 90 min of flight.     

Center-of-pressure based postural sway measures: Reliability and ability to distinguish between age,fear of falling and fall history

The purpose of this study was to compare the test-retest reliability of a wide variety of center-of-pressure (CoP) based postural sway measures and their ability to detect the differences between the young and older groups (age comparison), between the older low- and high-fear of falling groups (fear of falling comparison), and between the older non-faller and faller groups (fall history comparison). Forty healthy females (twenty each in both young and older groups) performed three trials of bipedal quiet standing on a force platform, in which eighteen reported CoP based measures were computed from recorded CoP trajectory. Intra-class correlation coefficient (ICC), standard error of measurement (SEM) and %SEM were used to quantify their relative and absolute reliability. Fear of falling and retrospective falls of the older group were recorded using falls efficacy scale-international (FES-I) and the history of falls questionnaire respectively. Experimental results showed that eight measures (RMS distance, RMS distance-AP, mean velocity, mean velocity-AP, mean frequency, mean frequency-AP, phase plane parameter and fractal dimension) had acceptable levels of relative and absolute reliability. Three measures (RMS distance-AP, mean velocity, and phase plane parameter) were sensitive to detect age-group difference and fear of falling under both visual conditions, but no single measure was capable to detect differences between the non-faller and faller groups.Relevance to industryThe results of this research provide useful information on the selection of appropriate center-of-pressure (CoP) based postural sway measures to assess individual's balance ability for preventing the occupational falls.     

Effects of localized warpage and stress on chip‐on‐glass packaging: Induced light‐leakage phenomenon in mid‐sized TFT‐LCD

Abstract— Mura defects become visible in a 13.3‐in. TFT‐LCD using chip‐on‐glass (COG) packaging when the thickness of the glass substrate is decreased from 0.5 to 0.3 mm. Mura, the non‐uniform brightness in LCDs, is caused by COG packaging due to the mismatch of the coefficient of thermal expansion (CTE) and Young's modulus between the glass substrate and the IC‐driver Si chips. In this paper, a 3‐D finite‐element‐analysis (FEA) model, coupled with transient thermal analysis is first established to examine the warpage and stress behavior in the upper‐glass‐plate post‐COG‐package processing for identifying the root causes of the light‐leakage phenomenon. Prior to that, the simulated warpage results are validated by surface‐contour measurement. Data and modeling results show that a low bonding temperature together with a low modulus in novel ACF materials can effectively eliminate Mura. Besides, thinner silicon or a shorter length of Si chips as drivers offers enhanced reduction in the localized warpage, and thus can be a practical and low‐cost solution for eliminating mura defects.     

In vivo monitoring of oxidative burst induced by ultraviolet A and C stress for oilseed rape by microbiosensor

In this paper, poly-o-phenylenediamine and Pt microparticle modified Pt electrode (POPD/Pt-MP/Pt) as microbiosensor has been developed to monitor in vivo oxidative burst induced by ultraviolet A (UV-A) and ultraviolet C (UV-C) radiation stress in oilseed rape (Brassica napus L.). Twice oxidative bursts were detected, appearing at 2 and 25 h, respectively. According to the peak area of amperometry, the amount of H₂O₂ induced by UV stress was estimated to be 6.2 × 10⁻¹⁰ and 3.1 × 10⁻¹⁰ mol for such two oxidative bursts in detected leafstalk, respectively. This novel microbiosensor provides an effective tool for studying the defense reaction of the plant in the situation of UV stress and probing the antioxidative mechanism of the antioxidative enzyme.     

Occupational stress in submariners: The impact of isolated and confined work on psychological well-being

This study aimed to identify work-related and personal factors associated with occupational stress in submariners. Work and well-being questionnaires were distributed to 219 male submariners (mean age 34 years), as part of a larger cohort study involving a stratified sample of 4951 Royal Navy (RN) personnel. The stress rate in submariners was 40%; significantly higher than the stress rate in the general RN, although once demographic factors were controlled for in a matched control sample, this difference was no longer significant. A summary model accounted for 49% of the variance in submariner stress, with key differences emerging between the occupational factors associated with stress in submariners and in the general RN. The longitudinal nature of this study permits stress in submariners to be monitored over 5 years, which will provide valuable insights into the chronicity of stress in this specialised occupational group.

Statement of Relevance: This paper contributes to the current literature on the negative impact of working in isolated conditions. It is demonstrated that occupational stress in submarines can be partially explained using current theories of stress in the workplace. However, the constraints of a restricted environment introduce additional factors which can also be associated with occupational stress.     

Inhibition-related N2 and P3: Indicators of visually induced motion sickness (VIMS)

Visually induced motion sickness (VIMS) leads to psychophysiological discomfort and has an adverse effect on executive function. Response inhibition, which can inhibit inappropriate behavior to adapt to changing environments, is an important aspect of executive function. The present study investigated the changes in response inhibition following VIMS using event-related potentials (ERPs). In a two-choice oddball task, ERPs were recorded at baseline (pretest) and after a 40-min virtual reality (VR) training session (posttest). The results showed a larger deviant-N2 amplitude, smaller deviant-P3 amplitude and delayed deviant-P3 latency after the VR training. Our findings suggest that VIMS is characterized in part by impaired response inhibition and that inhibition-related N2 and P3 can be used as electrophysiological indices of response inhibition in the assessment of VIMS.     

Predicting employee information security policy compliance on a daily basis: The interplay of security-related stress,emotions, and neutralization

We conceptualized security-related stress (SRS) and proposed a theoretical model linking SRS, discrete emotions, coping response, and information security policy (ISP) compliance. We used an experience sampling design, wherein 138 professionals completed surveys. We observed that SRS had a positive association with frustration and fatigue, and these negative emotions were associated with neutralization of ISP violations. Additionally, frustration and fatigue make employees more likely to follow through on their rationalizations of ISP violations by decreased ISP compliance. Our findings provide evidence that neutralization is not a completely stable phenomenon but can vary within individuals from one time point to another.