Packaging of nanostructured microelectromechanical systems microtriode devices

Combining the world of microelectromechanical systems (MEMS) with that of nano can lead to new devices with unique or advanced functionalities. Carbon nanotubes are fascinating new nanomaterials with many interesting physical, chemical, and electronic properties and potential new applications. We have incorporated nanotubes into the MEMS structure as patterned, cold-cathode field emitters to create on-chip, miniature vacuum tubes of microtriodes that can be useful for high-frequency microwave communications. Proper bonding and assembly processes were essential in providing reliable electrical connections and improved amplification performances.     

Lead-free universal solders for optical and electronic devices

Widely used electronic components and optical materials are made up of a variety of inorganic materials, such as nitrides, carbides, oxides, sulfides, fluorides, selenides, diamond, silicon, and GaAs. The surfaces of these materials are known to be very difficult to bond with low-melting-point solders. A direct and powerful bonding on these surfaces has been obtained in air, without using any flux, by using low-temperature solders containing rare earth (RE) alloying elements. The nature of the bonding is based on chemical reactions at the interface, and hence, strong bonds are obtained. The Sn-3.5%Ag-2.5%Lu (by weight) solder and the Au-19.5%Sn-2%Lu solder, for example, exhibit interfacial-bond strengths in excess of 6.9–13.8 MPa. They can be useful for providing direct, ohmic-electrical contacts and interconnects in a variety of electronic assemblies and for producing dimensionally stable and reliable bonding in optical fiber, laser devices, or thermal-management assemblies.     

Lead (Pb)-free solders for electronic packaging

The harmful effects of lead on the environment and human health, coupled with the threat of legislation, have prompted a serious search for lead-free solders for electronic packaging applications. At present, Sn-Pb eutectic and other Pb-containing solders find widespread use in printed circuit board assembly. Several Pb-free solder alloys which appear to have the potential for replacing Sn-Pb solders are receiving increased attention from the electronic assembly community. Recently, numerous studies have been published detailing the wetting characteristics, tensile and shear strength, and creep and low-cycle fatigue properties of these alloys. It is the purpose of this paper to review these results and assess the suitability of the solders for electronic packaging from the viewpoints of process technology and reliability.     

Application of Au-Sn eutectic bonding in hermetic radio-frequency microelectromechanical system wafer level packaging

Development of packaging is one of the critical issues toward realizing commercialization of radio-frequency-microelectromechanical system (RF-MEMS) devices. The RF-MEMS package should be designed to have small size, hermetic protection, good RF performance, and high reliability. In addition, packaging should be conducted at sufficiently low temperature. In this paper, a low-temperature hermetic wafer level packaging scheme for the RF-MEMS devices is presented. For hermetic sealing, Au-Sn eutectic bonding technology at temperatures below 300°C is used. Au-Sn multilayer metallization with a square loop of 70 μm in width is performed. The electrical feed-through is achieved by the vertical through-hole via filling with electroplated Cu. The size of the MEMS package is 1 mm × 1 mm × 700 μm. The shear strength and hermeticity of the package satisfies the requirements of MIL-STD-883F. Any organic gases or contamination are not observed inside the package. The total insertion loss for the packaging is 0.075 dB at 2 GHz. Furthermore, the robustness of the package is demonstrated by observing no performance degradation and physical damage of the package after several reliability tests.     

The application of lead-free solder to optical fiber packaging

To achieve precise, hermetic, and reliable optoelectronic packaging, we studied a novel technology for bonding fibers to v-grooved chips by metallic soldering. Multilayered metallization of Ti/Au, Ti/Cu/Au, or Ti/Ni/Au has been prepared to improve the poor bonding nature of solder on oxide surface. The eutectic 43Sn57Bi (wt.%) alloy, having a melting point of 139°C, was selected to bond the fibers to v-grooved chips. The alignment and adhesion tests result show that the precision packaging by soldering has a satisfied reliability in the range of working temperature from −40°C to 85°C. The metallic solder bonding is hermetic, and hence, it can isolate the optical device from ambient environment.     

Fabrication of 3D MEMS toroidal microinductor for high temperature application

Based on Microelectromechanical systems (MEMS) technique and thick photoresist lithography technology, a new toroidal-type inductor for high temperature application has been successfully developed. In the fabrication process, heat-resistant materials are used, alumina as insulator and supporting materials instead of polyimide, heat resistant glass for underlay instead of normal glass, and copper for coil. The maximum inductance is 87 nH at 0.826 GHz and maximum of quality factor (Q-factor) is 4.63 at 0.786 GHz, at room temperature. With simulation of thermal deformation, it shows that the developed toroidal inductor can be suitable for high temperature application, from 300 to 700 °C.     

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     

圆片级低温富锡金锡键合

Sn-rich Au–Sn solder bonding has been systematically investigated for low cost and low temperature wafer-level packaging of high-end MEMS devices.The AuSn2 phase with the highest Vickers-hardness among the four stable intermetallic compounds of the Au–Sn system makes a major contribution to the high bonding shear strength.The maximum shear strength of 64 MPa and a leak rate lower than 4.9×10-7 atm·cc/s have been obtained for Au46Sn54 solder bonded at 310 ℃.This wafer-level low cost bonding technique with high bonding strength can be applied to MEMS devices requiring low temperature packaging.     

MEMS后封装技术

通过对局部加热与压焊技术的研讨,介绍了微系统后封装技术,微系统封装技术在微电机系统(MEMS)蓬勃兴起的领域已成为主要的研究课题.构建多应用后封装工艺不仅推动了此领域的发展,而且加速了产品的商业化进程.文章概述了通过局部加热和压焊技术形成创新型后封装的方法,阐明了目前MEMS封装技术和晶片压焊工艺技术的工程基础.重点陈...     

MEMS局部加热封装技术与应用

随着半导体技术的发展,封装集成度不断提高,迫切需要发展一种低温封装与键合技术,满足热敏器件封装和热膨胀系数差较大的同质或异质材料间的键合需求。针对现有整体加热封装技术的不足,首先介绍了局部加热封装技术的原理与方法,然后对电流加热、激光加热、微波加热、感应加热和反应加热等几种局部加热封装技术进行了比较分析,最后具体介绍了局部加热封装技术在热敏器件封装、MEMS封装和异质材料集成等方面的应用。由于局部加热封装技术具有效率高、对器件热影响小等优点,有望在MEMS技术、系统封装(SiP)、三维封装及光电集成等领域得到广泛应用。     

A fast-developing and low-cost characterization and test environment for a double axis resonating micromirror

Testing and characterization of micro-electro-mechanical systems (MEMS) and micro-opto-electro-mechanical systems (MOEMS) can be very challenging due to the multi-domain nature of these devices. Nowadays high volume, high-cost, and accurate measuring systems are necessary to characterize and test MEMS and MOEMS especially to examine their motions, deflections, and resonance frequencies. This paper presents a fast-developing and low-cost environment for MEMS and MOEMS testing and characterization. The environment is based on a flexible mixed-signal platform named Intelligent Sensor InterFace (ISIF). As a case study we consider the characterization of a double axis scanning micromirror. The testing environment has been validated by comparing measurement results with results obtained by the finite element method simulations performed with Comsol Multiphysics. Finally, these results have been exploited to create an electrical equivalent model of the micromirror.     

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。     

面向MEMS封装的微钎料球键合技术

微钎料球键合技术是一种成本低、适应性强,可靠性好的键合技术,容易与现有的IC自动化设备集成。微钎料球键合技术结合倒扣封装可以实现低成本、高密度以及高可靠性的MEMS封装;而且具有自对准或者自组装的功能,在MEMS封装中获得了广泛的应用。准确地预测微钎料球键合对于MEMS自组装的影响依赖于动态模型的发展。微钎料球键合技术的出现推动了标准化的MEMS封装工艺的进程。     

Status and prospects for phosphor-based white LED packaging

The status and prospects for high-power, phosphor-based white light-emitting diode (LED) pack-aging have been presented. A system view for packaging design is proposed to address packaging issues. Four aspects of packaging are reviewed: optical control, thermal management, reliability and cost. Phosphor materials play the most important role in light extraction and color control. The conformal coating method improves the spatial color distribution (SCD) of LEDs. High refractive index (RI) encapsulants with high transmittance and modified surface morphology can enhance light extraction. Multi-phosphor-based packaging can realize the control of correlated color temperature (CCT) with high color rendering index (CRI). Effective thermal management can dissipate heat rapidly and reduce thermal stress caused by the mismatch of the coefficient of thermal expansion (CTE). Chip-on-board (COB) technology with a multi-layer ceramic substrate is the most promising method for high-power LED packaging. Low junction temperature will improve the reliability and provide longer life. Advanced processes, precise fabrication and careful operation are essential for high reliability LEDs. Cost is one of the biggest obstacles for the penetration of white LEDs into the market for general illumination products. Mass production in terms of CoB, system in packaging (SIP), 3D packaging and wafer level packaging (WLP) can reduce the cost significantly, especially when chip cost is lowered by using a large wafer size.     

用于三维封装的铜-铜低温键合技术进展

在三维系统封装技术中,金属热压键合是实现多层芯片堆叠和垂直互连的关键技术。为了解决热压键合产生的高温带来的不利影响,工业界和各大科研机构相继开发出了多种低温键合技术。综述了多种不同的低温金属键合技术(主要是Cu-Cu键合),重点阐述了国内外低温金属键合技术的最新研究进展及成果,并对不同低温金属键合技术的优缺点进行了分析和比较。     

光通信用垂直腔面发射激光器的进展

垂直腔面发射激光器(VCSEL)以其优异的性能有望成为信息时代的新光源.文章介绍了用于光通信的VCSEL的开发现状.     

应用于流动控制的MEMS传感器和执行器

出现于20世纪80年代后期的微机械技术可以制作出微米尺度的传感器和执行器。这些微器件与信号调节和处理电路集成后,组成了可执行分布式实时控制的微电子机械系统(MEMS)。这种性能为流动控制研究开辟了一个崭新的研究领域。利用MEMS技术设计和制作了一种传感器和一种执行器。实验证明,采用体硅腐蚀的工艺制作微流体器件是可行的,同时可以避免牺牲层腐蚀和释放的复杂工艺。     

A new construction method of LDPC codes for optical transmission systems

Based on the construction method of systematically constructed Gallager (SCG)(4,k) code,a new improved construction method of low density parity check (LDPC) code is proposed.Compared with the construc...     

Effect of Cu concentration on morphology of Sn-Ag-Cu solders by mechanical alloying

The mechanical alloying (MA) process is considered an alternative approach to produce solder materials. In this study, the effect of Cu concentration in the ternary Sn-3.5Ag-xCu (x=0.2, 0.7, and 1) solder by MA was investigated. The (Cu,Sn) solid solution was precipitated as the Cu₆Sn₅ intermetallic compound (IMC), which was distributed nonuniformly through the microstructure. The Cu₆Sn₅ IMC, which was present in the SnAgCu solder with high Cu composition, causes the as-milled MA particle to fracture to a smaller size. Appreciable distinction on morphology of as-milled MA powders with different Cu content was revealed. When the Cu concentration was low (x=0.2), MA particle aggregated to a spherical ingot with large particle size. For higher Cu concentration (x=0.7 and x=1), the MA particle turned to flakes with smaller particle size. The distinction of the milling mechanism of Sn-3.5Ag-xCu (x=0.2, 0.7, and 1) solder by the MA process was discussed. An effective approach was developed to reduce the particle size of the SnAgCu solder from 1 mm down to 10–100 μm by doping the Cu₆Sn₅ nanoparticle during the MA process. In addition, the differential scanning calorimetry (DSC) results also ensure the compatibility to apply the solder material for the reflow process.     

MEMS封装技术现状与发展趋势

介绍了 MEMS封装技术 ,包括单芯片和多芯片封装技术。从适用性的观点出发 ,概述了当前的 MEMS封装技术现状 ,并对其未来的发展趋势做出了分析