微系统三维(3D)封装技术

文章论述塑料三维(3D)结构微系统封装技术相关问题,描述了把微电机硅膜泵与3D塑料密封垂直多芯片模块封装(MCM-V)相结合的微系统集成化。采用有限元技术分析封装结构中的封装应力,根据有限元设计研究结果,改变芯片载体结构,降低其发生裂纹的危险。计划采用板上芯片和塑料无引线芯片载体的替代低应力和低成本的3D封装技术方案。     

数字信号处理微系统设计

随着整机单位对电路尺寸及国产化的要求越来越高,数字信号处理微系统的需求显得尤为迫切。数字信号处理微系统不仅要求做到物理空间的缩小,更要保证整体性能的提升以及应用的简单化。数字信号处理微系统可以从SoC功能芯片、高可靠陶瓷/塑封基板3D-SiP封装等多个方面实现。但由于其成本高、周期长等缺点,严重影响了数字信号处理微系统的快速发展。通过设计实例,介绍了一种通过成品电路二次封装的方法,既解决了成本及周期的问题,又实现了小型化的目标。     

Review: Semiconductor Piezoresistance for Microsystems

Piezoresistive sensors are among the earliest micromachined silicon devices. The need for smaller, less expensive, higher performance sensors helped drive early micromachining technology, a precursor to microsystems or microelectromechanical systems (MEMS). The effect of stress on doped silicon and germanium has been known since the work of Smith at Bell Laboratories in 1954. Since then, researchers have extensively reported on microscale, piezoresistive strain gauges, pressure sensors, accelerometers, and cantilever force/displacement sensors, including many commercially successful devices. In this paper, we review the history of piezoresistance, its physics and related fabrication techniques. We also discuss electrical noise in piezoresistors, device examples and design considerations, and alternative materials. This paper provides a comprehensive overview of integrated piezoresistor technology with an introduction to the physics of piezoresistivity, process and material selection and design guidance useful to researchers and device engineers.     

A skin-contact-actuated micropump for transdermal drug delivery

In this paper, a skin-contact-actuated dispenser/micropump for transdermal drug delivery applications is presented. The micropump consists of stacked polydimethylsiloxane layers mounted on a silicon substrate and operates based on the evaporation and condensation of a low-boiling-point liquid. Therefore, there is no need for a heater and a power source, since only the thermal energy provided by skin contact is required for the actuation. A prototype device with overall dimensions of 14 mm × 14 mm × 8 mm is fabricated and characterized. For a perfluoro compound working fluid (3M FC-3284), a flow rate of 28.8 μ L/min and a maximum back pressure of 28.9 kPa is measured.     

An Application Specific Design Methodology for Microsystems

A fundamental approach to a coherent design strategy for microsystems is presented in this paper. Establishing such a concept can provide undeniable advantages concerning manpower, technical resources and development time. Prevalent design steps are discussed in detail, referring to the suggested ideas. Several microsystem applications and software tools are taken into account to illustrate the main aspects of a consistent design flow.The approach of behavioral physical modelling in combination with model based design optimization applying efficient and robust numeric methods in both fields allows pre-production optimization. Thus, overall development and redevelopment effort can be reduced significantly.     

微系统封装热问题探讨

电子机械系统微型化就是把不同功能的各种元器件封装到紧密空间, 目的在于分析有关封装设计负载下降的方案. 采用计算机程序配置发生器生成系统的热传递路径的几何构造和平面基板上热分布作为样本的方法,把这些构造的温度解决方案压缩进入快速估计公式中,使封装设计能够自由地进行相关的热传递分析. 通过涉及到几何学方面复杂的传热路径的系统热传递分析,快速完成每个设计改变. 结果表明系统微型化热设计,就是系统构造和整个向周围环境热损耗之间的耦合,就是热通过自然对流和辐射,从系统外壳上的一个区域向周围扩散. 最后得出结论,外壳材料热传导性跨越的参数领域,以及系统的性能长度为系统级热传递领域,对系统的构造敏感.性能长度对塑料封装系统而言约为1cm,对陶瓷及合金封装约为3~10cm,在铜或铝金属包层系统为10~40 cm.     

3D-Printed Electrostatic Microactuators for Flexible Microsystems

Developing small-scale, lightweight, and flexible devices with integrated microactuators is one of the critical challenges in wearable haptic devices, soft robotics, and microrobotics. In this study, a novel fabrication process that leverages the benefits of 3D printing with two-photon polymerization and flexible printed circuit boards (FPCBs) is presented. This method enables flexible microsystems with 3D-printed electrostatic microactuators, which are demonstrated in a flexible integrated micromirror array and a legged microrobot with a mass of 4 mg. 3D electrostatic actuators on FPCBs are robust enough to actuate the micromirrors while the device is deformed, and they are easily integrated with off-the-shelf electronics. The crawling robot is one of the lightest legged microrobots actuated without external fields, and the legs actuated with 3D electrostatic actuators enable a locomotion speed of 0.27 body length per second. The proposed fabrication framework opens up a pathway toward a variety of highly integrated flexible microsystems.     

Compact Low-Power Impedance-to-Digital Converter for Sensor Array Microsystems

With the rapid progress in CMOS compatible microfabrication of biosensors, there is an emerging need to miniaturize biosensor arrays onto the surface of silicon chips that acquire and process sensor data, permitting improved sensitivity, cost and throughput. In this paper, a low power circuit that extracts and digitizes sensor impedance information is presented. Composed of a novel multiplying integrator and a unique bidirectional counter/shifter, the circuit shares resources for impedance extraction and digitization to maximize hardware efficiency. The extremely compact size of the circuit enables the implementation of sensor array microsystems with simultaneous multi-channel readout. Fabricated in 0.5 mum CMOS, the circuit consumes 6 muW at 3 V and occupies only 0.06 mm², permitting over 100 readout channels within a 3 times 3 mm die. Circuit performance has been verified with a biosensor for gramicidin ion channel embedded in a tethered bilayer lipid membrane.     

Electrochemical Deposition of Permalloy Films for Magneto-Semiconductor Microsystems

The results of investigating local electrochemical deposition from a chloride electrolyte are presented. Ni₈₁Fe₁₉ permalloy films with magnetic properties similar to those of 3D samples with a uniform thickness and low mechanical stresses without high-temperature annealing are obtained. The dependences of the rate of congruent deposition of the permalloy on the current density are presented.     

Enhanced Optimization Algorithms for the Development of Microsystems

Due to the ongoing growth of microsystems' complexity, there is an urgent need for automatic optimization. In order to include it seamlessly in the customary design process, the algorithms have to be fast and robust. Calculations of the quality function call for at least one FEM-, netlist based or behavioral simulation. Thus the optimization process is a very time consuming task. This paper presents a methodology for enhancing the convergence characteristics of heuristic search methodologies. The concept is to combine direct optimization strategies with interpolation methods in such a way that a mathematical model of the quality function is successively constructed in parallel to an optimization run. Once this model has is meaningful enough, its evaluation can substitute time consuming simulation runs.     

Highly Adaptive Transducer Interface Circuit for Multiparameter Microsystems

A reconfigurable transducer interface circuit that combines the communication and signal conditioning necessary to link a variety of sensors and actuators to a microsystem controller is reported. The adaptive readout circuitry supports high-resolution signal acquisition from capacitive, resistive, voltage and current mode sensors with programmable control of gain and offset to match sensor range and sensitivity. The chip accommodates sensor self test and self calibration and supports several power management schemes. It provides digital and analog outputs to control actuators and a standard interface to peripheral components. The 2.2times2.2 mm CMOS chip was fabricated in 0.5-mum, 3-metal, 2-poly process, dissipates ~50 muW at 3.3 V in a typical multisensor application utilizing periodic sleep mode, and can read out a wide range of sensors with high sensitivity. A prototype microsystem with a microcontroller and MEMS pressure, humidity, and temperature sensors has been implemented to characterize interface chip performance     

Automated Generation of Compact Models for Fluidic Microsystems

Simulation and design of microfluidic systems requires various level models: high-fidelity models (usually 3D) for design and optimization of particular elements and devices, as well as system-level models allowing for VLSI-scale simulation of such systems. For the latter purpose, reduced or compact models are necessary to make such system simulations computationally feasible. In this paper, we present a design methodology and practical approach for generation of compact models of microfluidic elements. In this procedure we use high-fidelity 3D simulations of the microfluidic devices to extract their characteristics for compact models, and subsequently, to validate the compact model behavior in various regimes of operation. The compact models are generated automatically in the formats that can be directly used in SPICE or SABER. As an example of a nonlinear fluidic device, the generation of compact model for Tesla valve is described in detail. Tesla valve is one of the no-moving-parts (NMP) valves used in micropumps in MEMS. Its principle of operation is based on the rectification of the fluid, so it may be considered as a fluidic diode.     

Test Strategies for Electrode Degradation in Bio-Fluidic Microsystems

Electrode technology is fundamental to numerous actuation and sensing functions in bio-fluidic microsystems that target portable bio-analytical instruments. Within these systems high levels of reliability and robustness are crucial and normally complemented by requirements for extremely low probabilities of false positives or negatives being generated. New methods of validating functionality and integrity of the reading are hence required. Embedded test and condition monitoring are crucial technologies for delivering these capabilities. This paper presents two solutions for detecting degradation in electrodes that interface to fluidic or biological systems. In the first solution, a low frequency, impedance based method for identifying degraded structures within an array is proposed. This method depends on measuring and comparing the impedance of each sensing electrode. This research is backed up by physical measurements from an electrode array for drug testing on cardiac and neuron tissue. In the second solution, a mid-frequency oscillation test technique is proposed that is sensitive to degradation in the bio-fluidic interface capacitance, to contamination and to fouling.     

Tribotronics for Active Mechanosensation and Self‐Powered Microsystems

Tribotronics has attracted great attention as a new research field that encompasses the control and tuning of semiconductor transport by triboelectricity. Here, tribotronics is reviewed in terms of active mechanosensation and human–machine interfacing. As a fundamental unit, contact electrification field‐effect transistors are analyzed, in which the triboelectric potential can be used to control electrical transport in semiconductors. Several tribotronic functional devices have been developed for active control and information sensing, which has demonstrated triboelectricity‐controlled electronics and established active mechanosensation for the external environment. In addition, the universal triboelectric power management strategy and the triboelectric nanogenerator‐based constant sources are also reviewed, in which triboelectricity can be managed by electronics in the reverse action. With the implantation of triboelectric power management modules, the harvested triboelectricity by various kinds of human kinetic and environmental mechanical energy can be effectively managed as a power supply for self‐powered microsystems. In terms of the research prospects for interactions between triboelectricity and semiconductors, tribotronics is expected to demonstrate significant impact and potential applications in micro‐electro‐mechanical systems/nano‐electro‐mechanical systems (MEMS/NEMS), flexible electronics, robotics, wireless sensor network, and Internet of Things.     

微系统热管理技术的新发展

多功能高度集成的微系统技术对信息系统的通信、传感、处理和执行等方面产生了很大的影响,而热管理问题却一直制约着微系统技术的发展。该文介绍了美国在微系统热管理技术方面的项目研究计划及基于热传导与液冷技术的微系统热管理技术的新进展,提出了一种基于压电驱动的主动微系统高效热管理方法,并通过搭建试验样机完成原理性测试验证。该技术主要针对如微波毫米波大功率“瓦片式”T/R（收发）组件等射频微系统热管理应用。     

射频微系统冷却技术综述

雷达、电子战等射频电子装备向高集成度和大功率方向发展,有力牵引了射频微系统技术的进步,同时给冷却设计带来三大挑战:高面热流度、热堆叠和高体热流密度。冷却技术成为制约射频微系统应用的关键瓶颈之一。文中综述了国内外当前射频微系统冷却技术的发展现状,传统的远程散热架构因界面多与传热路径远已难以为继,高集成度的近结冷却技术显著提升芯片散热能力;以有源相控阵雷达为例,提出了射频微系统冷却的三代技术路线,指出了射频微系统热设计的主要发展方向。     

埋置型叠层微系统封装技术

包含微机电系统(MEMS)混合元器件的埋置型叠层封装,此封装工艺为目前用于微电子封装的挠曲基板上芯片(COF)工艺的衍生物.COF是一种高性能、多芯片封装工艺技术,在此封装中把芯片包入模塑塑料基板中,通过在元器件上形成的薄膜结构构成互连.研究的激光融除工艺能够使所选择的COF叠层区域有效融除,而对封装的MEMS器件影响...     

埋置型叠层微系统封装技术

包含微机电系统(MEMS)混合元器件的埋置型叠层封装,此封装工艺为目前用于微电子封装的挠曲基板上芯片(COF)工艺的衍生物。COF是一种高性能、多芯片封装工艺技术,在此封装中把芯片包入模塑塑料基板中,通过在元器件上形成的薄膜结构构成互连。研究的激光融除工艺能够使所选择的COF叠层区域有效融除,而对封装的MEMS器件影响最小。对用于标准的COF工艺的融除程序进行分析和特征描述,以便设计一种新的对裸露的MEMS器件热损坏的潜在性最小的程序。COF/MEMS封装技术非常适合于诸如微光学及无线射频器件等很多微系统封装的应用。