先进的MEMS封装技术

从特殊的信号界面、立体结构、外壳、钝化和可靠性五个方面总结了MEMS封装的特殊性。介绍了几种当前先进的MEMS封装技术：倒装焊MEMS、多芯片(MCP)和模块式封装(MOMEMS)。最后强调，必须加强MEMS封装的研究。     

MEMS中的封装技术研究

MEMS中的封装工艺与半导体工艺中的封装具有一定的相似性 ,因此 ,早期MEMS的封装大多借用半导体中现成的工艺。本文首先介绍了封装的主要形式 ,然后着重阐述了晶圆级封装与芯片级封装[1] 。最后给出了一些商业化的实例     

MEMS中的封装技术研究

MEMS中的封装工艺与半导体工艺中的封装具有一定的相似性，因此，早期MEMS的封装大多借用半导体中现成的工艺。本文首先介绍了封装的主要形式，然后着重阐述了晶圆级封装与芯片级封装。最后给出了一些商业化的实例。     

用于MEMS器件芯片级封装的金-硅键合技术研究

MEMS器件大都含有可动的硅结构，在器件加工过程中，特别是在封装过程中极易受损，大大影响器件的成品率。如果能在MEMS器件可动结构完成以后，加上一层封盖保护，可以显著提高器件的成品率和可靠性。本文提出了一种用于MEMS芯片封盖保护的金-硅键合新结构，实验证明此方法简单实用，效果良好。该技术与器件制造工艺兼容，键合温度低，有足够的键合强度，不损坏器件结构，实现了MEMS器件的芯片级封装。我们已经将此技术成功地应用于射流陀螺的制造工艺中。     

用于MEMS器件芯片级封装的金-硅键合技术研究

MEMS器件大都含有可动的硅结构 ,在器件加工过程中 ,特别是在封装过程中极易受损 ,大大影响器件的成品率。如果能在MEMS器件可动结构完成以后 ,加上一层封盖保护 ,可以显著提高器件的成品率和可靠性。本文提出了一种用于MEMS芯片封盖保护的金 硅键合新结构 ,实验证明此方法简单实用 ,效果良好。该技术与器件制造工艺兼容 ,键合温度低 ,有足够的键合强度 ,不损坏器件结构 ,实现了MEMS器件的芯片级封装。我们已经将此技术成功地应用于射流陀螺的制造工艺中     

Substrate interconnect technologies for 3-D MEMS packaging

We report the development of 3-dimensional silicon substrate interconnect technologies, specifically for reducing the package size of a MOSFET relay. The ability to interconnect multiple chips at different elevations on a single substrate can significantly improve device performance and size. We present the process development of through-hole interconnects fabricated using deep reactive ion etching (DRIE), with an emphasis on achieving positively tapered, smooth sidewalls to ease deposition of a seed layer for subsequent Cu electroplating. Gray-scale technology is integrated on the same substrate to provide smooth inclined surfaces between multiple vertical levels (>100 μm apart), enabling interconnection between the two levels via simple metal evaporation and lithography. The developments discussed for each technique may be used together or independently to address future packaging and integration needs.     

采用综合法封装MEMS加速仪

MEMS封装系统应有MEMS执行感应功能,而且还要避免受到外界环境的影响,同时持续地改进质量,达到较高的ppm性能.本文采用SOIC封装,必须维持一个特定的共振频率,从而防止传感器被粘住或卡住.同时,封装必须确保传感器是可靠和完整的,没有出现断裂或输出偏差.本文采用一种综合学科研究方法,以确定合适的固晶材料来彻底解决器...     

Laser-assisted sealing and testing for ceramic packaging of MEMS devices

In this work, a CO/sub 2/ laser-assisted silicon lid sealing process, utilizing Au80/Sn20 solder, for encapsulating gas breakdown test micro-electro-mechanical structures (MEMS) in a ceramic quad flatpack (CQFP) was studied. Wire bonded MEMS dies were sealed into CQFPs under various gas media, such as air, nitrogen, helium and vacuum. The gas breakdown test results showed a significantly higher breakdown voltage for vacuum packaged parts compared to those packaged in other various gas environments. Hermeticity testing according to MIL-STD-883E showed that the leak rate of the package was below 10/sup -8/ atm cc/s. The bonding was uniform and the bonding strength is believed to be comparable to the tensile strength of Au80/Sn20 solder.     

Localized bonding processes for assembly and packaging of polymeric MEMS

Localized bonding schemes for the assembly and packaging of polymer-based microelectromechanical systems (MEMS) devices have been successfully demonstrated. These include three bonding systems of plastics-to-silicon, plastics-to-glass, and plastics-to-plastics combinations based on two bonding processes of localized resistive heating: 1) built-in resistive heaters and 2) reusable resistive heaters. In the prototype demonstrations, aluminum thin films are deposited and patterned as resistive heaters and plastic materials are locally melted and solidified for bonding. A typical contact pressure of 0.4 MPa is applied to assure intimate contact of the two bonding substrates and the localized bonding process is completed within less than 0.25 s of heating. It is estimated that the local temperature at the bonding interface can reach above 150/spl deg/C while the substrate temperature away from the heaters can be controlled to be under 40/spl deg/C during the bonding process. The approach of localized heating for bonding of plastic materials while maintaining low temperature globally enables direct sealing of polymer-based MEMS without dispensing additional adhesives or damaging preexisting, temperature-sensitive substances. Furthermore, water encapsulation by plastics-to-plastics bonding is successfully performed to demonstrate the capability of low temperature processing. As such, this technique can be applied broadly in plastic assembly, packaging, and liquid encapsulation for microsystems, including microfluidic devices.     

MEMS封装V形腔阵列的研究与制备

MEMS器件封装时,为了给具有活动装置的MEMS器件提供足够的空间,需要在封装的帽层上刻蚀出V形腔结构。本文利用V形槽工艺,制作出适合于硅片上大面积MEMS芯片封装用V形腔阵列。SEM照片表明,所做V形腔阵列结构整齐,图形清晰。     

Analysis of RF MEMS switch packaging Process for yield improvement

Radio frequency microelectro-mechanical systems (RF MEMS) switches offer significant performance advantages in high-frequency RF applications. The switches are actuated by electrostatic force when voltage was applied to the electrodes. Such devices provide high isolation when open and low contact resistance when closed. However, during the packaging process, there are various possible failure modes that may affect the switch yield and performance. The RF MEMS switches were first placed in a package and went through lid seal at 320degC. The assembled packages were then attached to a printed circuit board at 220degC. During the process, some switches failed due to electrical shorting. Interestingly, more failures were observed at the lower temperature of 220degC rather than 320degC. The failure mode was associated with the shorting bar and the cantilever design. Finite element simulations and simplified analytical solutions were used to understand the mechanics driving the behaviors. Simulation results have shown excellent agreement with experimental observations and measurements. Various solutions in package configurations were explored to overcome the hurdles in MEMS packaging and achieve better yield and performance     

Flip-chip packaging solution for CMOS image sensor device

Chip scaled opto-electronic packaging is introduced as a cost and size effective packaging solution for mobile phone with built in camera. The chip scaled assembly includes gold bumped CMOS image sensor device and its flip-chip bonding on substrate using the anisotropic conductive material. Two types of flip-chip module were designed to have flip-chip on flex and flip-chip on glass. It is shown that well controlled bumping process of thin film deposition and wet etching gives no damage to image sensing surface during the deposition and stripping of metal film. As results, smart and high degree miniaturized image sensor module is actualized for mobile phone and the reliability test results proved the robustness of module structure having flip-chip. Solder bumping was also reviewed and successfully introduced to verify the alternative of image sensor bumping.     

基于MEMS加速度传感器的轴承故障检测

提出了一种通过利用低成本的MEMS加速度传感器进行振动分析,实现检测电动机深沟球轴承多重故障的简易方法。首先分析了轴承多故障特征频率,然后通过快速傅里叶变换算法对轴承出现故障的电动机振动频率进行了分析,从振动频谱中提取故障频率来诊断轴承多重故障的存在。同时,基频分量周围的边带频率分量表明由于故障轴承存在空气间隙。在空载、单相以及失衡电压条件下通过实验对提出的方法进行了研究,结果显示提取出的故障频率与理论值两者十分接近,表明提出的方法能够有效检测并识别出感应电动机的多故障特征。     

基于MEMS传感器的运动轨迹的追踪系统

设计一种基于MEMS惯性传感器的行人运动轨迹的追踪系统。测量方式采用计步器的原理,直接利用加速度传感器来检测记录行人步伐的加速度的变化波形,采用三轴磁力计检测行人的运动方向,同时采用加速度值对方向进行倾角补偿。采用平滑滤波的方法对测量结果滤波,通过微处理器处理原始数据,得到比较准确的行人步数和运动方向。最后通过实验验证系统的有效性和可行性。     

一种用于MEMS检测的无耦合六维力传感器的研制

提出了一种用于MEMS检测试验平台中力学量测量的无耦合六维力 /力矩传感器的设计。对传感器的结构形式、测量原理作了介绍 ,进行了试验验证并给出了从 8路输出电压到六维力 /力矩的传递矩阵。该传感器通过采用巧妙的结构形式和特定的电阻应变片布片方案实现了六维力解耦 ,大大简化了后置信号处理电路的设计且在各轴都具有较好的测量分辨率。实验证明 ,该传感器具有无耦合、测量分辨率高、线性度好、标定简单、贴片方便、制造成本低的优点 ,满足了预计的设计要求     

一种用于MEMS检测的无耦合六维力传感器的研制

提出了一种用于MEMS检测试验平台中力学量测量的无耦合六维力／力矩传感器的设计。对传感器的结构形式、测量原理作了介绍，进行了试验验证并给出了从8路输出电压到六维力／力矩的传递矩阵。该传感器通过采用巧妙的结构形式和特定的电阻应变片布片方案实现了六维力解耦，大大简化了后置信号处理电路的设计且在各轴都具有较好的测量分辨率。实验证明，该传感器具有无耦合、测量分辨率高、线性度好、标定简单、贴片方便、制造成本低的优点，满足了预计的设计要求。     

Micro packaged MEMS pressure sensor for intracranial pressure measurement

This paper presents a micro packaged MEMS pressure sensor for intracranial pressure measurement which belongs to BioMEMS. It can be used in lumbar puncture surgery to measure intracranial pressure. Miniaturization is key for lumbar puncture surgery because the sensor must be small enough to allow it be placed in the reagent chamber of the lumbar puncture needle. The size of the sensor is decided by the size of the sensor chip and package. Our sensor chip is based on silicon piezoresistive effect and the size is 400 × 400 μm². It is much smaller than the reported polymer intracranial pressure sensors such as liquid crystal polymer sensors. In terms of package, the traditional dual in-line package obviously could not match the size need, the minimal size of recently reported MEMS-based intracranial pressure sensors after packaging is 10 × 10 mm². In this work, we are the first to introduce a quad flat no-lead package as the package form of piezoresistive intracranial pressure sensors, the whole size of the sensor is minimized to only 3 × 3 mm². Considering the liquid measurement environment, the sensor is gummed and waterproof performance is tested; the sensitivity of the sensor is 0.9 × 10^-2 mV/kPa.     

A compact instrumentation amplifier for MEMS thermal sensor interfacing

A compact CMOS instrumentation amplifier, based on a properly modified second order G _m?CC low pass filter (LPF), is proposed as a possible readout channel for integrated thermal sensors. Low noise and low offset characteristics are obtained by applying chopper modulation to the input transconductor. The high input thermal noise density, typical of low frequency G _m?CC filters, has been significantly reduced by adopting a two-stage topology for the first transconductor. Using this approach, an input noise density adequate for thermal sensor interfacing was obtained with no need of off-chip capacitors. The intrinsic filtering property of the amplifier effectively rejects the modulated offset ripple, allowing direct connection of the amplifier output to a low sampling rate AD converter. An original switching strategy involving swapping of the input and feedback ports is used to improve the gain precision. The effectiveness of the technique is proven by means of analytical arguments and electrical simulations performed on a prototype, designed with the STMicroelectronics BCD6s process.