Monolithic pressure-flow sensor

A new silicon-based monolithic pressure-flow sensor has been developed. Its operation is based on the piezoresistive effect for pressure sensing and heat transfer for flow sensing. The sensor chip has a thermal isolation structure that is made of an oxidized porous silicon membrane. This structure thermally isolates the heating element located on the membrane from the rim of the chip. The sensor, in which the chip was mounted on a wall of an acrylate plastic pipe, was designed for biomedical applications. Measurements were made at pressures of 0-300 mmHg, water flow rates of 0-7 1/min, and fluid temperatures of 25-45°C. The temperature difference between the heating element and the fluid temperature sensing element was kept at 5°C. The sensor showed a pressure sensitivity of 1.32 µV/mmHg for 1-mA current supplied, a nonlinearity of 0.5 %F.S. for pressure sensing, an accuracy of ±10 %F.S. for flow sensing, and 90-percent response time of below 100 ms for flow sensing. The sensor was applied to the simultaneous measurements of pressure and flow rate in pulsedflow experimental systems.     

MEMS热式风速风向传感器输出性能优化研究

环境测温二极管在工作时受传感器芯片热场影响,常引发MEMS热式风速风向传感器加热电压-风速曲线异常。将其更换为外置测温二极管,并调整其与传感器芯片距离,成功解决了输出曲线异常现象。并在此基础上,优化芯片及外置测温二极管的封装方案,消除了热场的相互干扰和不必要的热损耗,同时保证了外置测温二极管与空气的良好接触。风场测试结果表明,传感器的加热电压-风速曲线变得平滑,且重复性好,风速和风向的测量误差分别在±4%和±4°以内,系统的上电稳定时间大幅缩短至15 s左右。     

光纤布拉格光栅热式流量传感技术研究

光纤布拉格光栅(Fiber Bragg Grating, FBG)热式流量传感技术具有测量阈值低、灵敏度高等优点,是近年来流量测量领域的研究热点。概述了FBG热式流量传感原理,总结了当前该技术研究的重点和难点问题(主要分为传感器加热、结构设计、温度补偿和封装增敏四个方面),旨在发现问题、展望未来。从近年来的典型研究成果入手,分析了电加热、光加热两种传感器加热方式和热线式传感结构。温度补偿和封装增敏部分则作为专题来研究,其中温度补偿旨在解决传感器加热换热与环境温度交叉敏感问题。最后归纳分析了该技术在大流量时的低灵敏度特性,并讨论了提升传感器灵敏度未来可能的研究方向和相关方法。     

Monolithic integrated direction-sensitive flow sensor

A manolithic integrated direction-sensitive flow sensor for measuring the velocity of gas or liquid flow is described. Its operation is based on the transfer of heat from a heated chip to a flowing fluid. Temperature differences on the chip are a measure for the flow velocity and flow direction in a plane parallel with the chip's surface. The sensor can be embedded in a wall, for example, in a wall of a tube conducting a fluid flow, and can be shielded from a direct contact with the fluid. Measurements are stated for velocities in a range below 3 m/s for air at room temperature.     

A high-performance thermal module for computer packaging

A thermal module was designed to transfer heat efficiently from high power dissipation chips to a liquid coolant via forced convection. Turbulent and laminar flow regimes were investigated. Channel geometries for deep channels (1000 μm deep, and used for turbulent flow), and shallow channels (100 μm deep, and used for laminar flow) were optimized for high heat transfer coefficient, ease of fabrication, and better structural rigidity of the module. A 4″ x 4″ module, made out of Cu, was tested using a 4″ Si “thermal” wafer as a heat generating source as well as a temperature sensor. Wafer scale integration and high energy ion implantation were employed to obtain nine l x l cm heat sources, and temperature sensing diodes embedded within the thermal wafer. For the deep channel design, the maximum device temperature rise on the module was 18° C for a power dissipation of 42 W/chip, and a flow rate of 126 cc/sec. For the shallow channel design, the temperature rise was 19° C for a flow rate of 19 cc/sec, and a power dissipation level of 42 W/chip. With all nine chips on the thermal module powered to 42 W/chip, the maximum chip to chip temperature variations were found to be 2 and 8° C for deep and shallow channel designs, respectively.     

新型恒温式集成温度传感器

<正> 一、引言 把敏感元件与信号处理电路集成在一起,实现传感器的集成化,是目前传感器发展的一个重要方向。它不仅可提高传感器的信噪比,还可以提高传感器的性能和接口灵活性。对于集成温度传感器,由于芯片上的信号处理电路与敏感元件必须一起工作在被测环境温度中,这样环境温度的变化会影响传感器中信号处理电路的性能,从而影响整个集成传感器的性能。本文提出一种工作在恒定芯片温度的新型集成温度传感器,其中的信号处理电路不受环境温度的影响,而且还具有传统温度传感器所没有的优点。     

Integrated electro-thermomechanical analysis of nonuniformly chip-powered microelectronic system

An integrated electrical, fluid flow and thermomechanical analysis is presented to study a product reliability and thermal management solution in an actual or nonuniform chip power distribution of an integrated circuit device in a realistic system application environment. This study aims to improve the existing limitations both on electrothermal analysis where simplified thermal boundary conditions is mostly used and on the current thermal and fluid flow analysis where uniform chip power is widely used to calculate the temperature. In this approach, the localized on-chip power distribution is obtained by using a transistor-level circuit model for simulating the interaction between the macro and functional blocks. A computational fluid dynamics analysis is used to calculate the fluid flow and heat transfer solution with a realistic thermal boundary conditions. To address the ultimate thermal induced mechanical stress and reliability effects on the chip-packaged assembly due to the nonuniform chip power distribution, finite element model is employed for the sequential steady-state heat transfer and mechanical analysis. The results are then discussed and specifically compared with the solutions based on the uniform chip power conditions.     

Miniaturised multi-MEMS sensor development

This paper describes the design, fabrication and initial characterisation of a MEMS-based environmental monitoring system. Intended for use with miniaturised Wireless Sensor Network (WSN) motes, the die measures 3 × 3 mm and incorporates humidity, temperature, corrosion, gas and gas flow velocity sensors on a single substrate. Fabricated using a combination of surface and bulk micromachining technologies, the sensor system is designed to replace discrete components on WSN module boards, thereby minimising space consumption and enabling smaller, cheaper wireless motes. Sensors have been characterised over a wide range of environmental conditions. An analysis of the effects of changes in environmental parameters other than the measurand of interest on the performance of the temperature and humidity sensors has been carried out, and corrections applied where necessary. A variety of corrosion monitors have been demonstrated. A gas flow velocity sensor, based on forced convective heat transfer and which has been thermally isolated from the silicon substrate in order to reduce power consumption and improve sensitivity at low flow-rates, has also been presented. The paper also outlines the design of the next generation sensing platform using the novel 10 mm wireless cube developed at Tyndall.     

带有TSV的硅基大功率LED封装技术研究

介绍了一种带有凹槽和硅通孔(through silicon via,TSV)的硅基制备以及晶圆级白光LED的封装方法。针对硅基大功率LED的封装结构建立了热传导模型,并通过有限元软件模拟分析了这种封装形式的散热效果。模拟结果显示,硅基封装满足LED芯片p-n结的温度要求。实验结合半导体制造工艺,在硅基板上完成了凹槽和通孔的制造,实现了LED芯片的有效封装。热阻测试仪测得硅基的热阻为1.068K/W。实验结果证明,这种方法有效实现了低热阻、低成本、高密度的LED芯片封装,是大功率LED封装发展的重要方向。     

Multidisciplinary heat generating logic block placement optimization using genetic algorithm

A multidisciplinary optimization methodology for placement of heat generating semiconductor logic blocks on integrated circuit chips is presented. The methodology includes thermal and wiring length criteria, which are optimized simultaneously using a genetic algorithm. An effective thermal performance prediction methodology based on a superposition method is used to determine the temperature distribution on a silicon chip due to multiple heat generating logic blocks. Using the superposition method, the predicted temperature distribution in the silicon chip is obtained in much shorter time than with a detailed finite element model and with comparable accuracy. The main advantage of the present multidisciplinary design and optimization methodology is its ability to handle multiple design objectives simultaneously for optimized placement of heat generating logic blocks. Capabilities of the present methodology are demonstrated by applying it to several standard benchmarks. The multidisciplinary logic block placement optimization results indicate that the maximum temperature on a silicon chip can be reduced by up to 7.5 °C, compared to the case in which only the wiring length is minimized.     

A novel fabrication process of MEMS devices on polyimide flexible substrates

Micro-electro-mechanic-system (MEMS) devices on flexible substrate are important for non-planar and non-rigid surface applications. In this paper, a novel and cost-effective fabrication process for an 8 × 8 MEMS temperature sensor array with a lateral dimension of 2.5 mm × 5.5 mm on a polyimide flexible substrate is developed. A 40 μm thick polyimide substrate is formed on a rigid silicon wafer using as a mechanical carrier throughout the fabrication by four successive spin coating liquid polyimide. The arrayed temperature sensing elements made of 1200 Å sputtered platinum thin film on polyimide substrate show excellent linearity with a temperature coefficient of resistance of 0.0028/°C. The purposed sensor obtains a high sensitivity of 0.781 Ω/°C at 8 mA at constant drive current. Because of the low heat capacity and excellent thermal isolation, the temperature sensing element shows excellent high sensitivity and a fast thermal response. The finished devices are flexible enough to be folded and twisted achieving any desired shape and form. Employing spin-coated liquid polyimide substrate instead of solid polyimide sheet minimizes the thermal cycling as well as improves the production yield. This fabrication technique first introduces the spin-coated PDMS (Polydimethylsiloxane) interlayer between the silicon carrier and the polyimide substrate and makes the polyimide-based devices separate much easier and greatly simplifies the fabrication process with a high production yield. A non-successive two-stage cure procedure for the polyimide precursor is developed to meet low-temperature requirement of the PDMS interlayer. The fabrication procedure developed in this research is compatible with conventional MEMS technology through an optimized integration process. The novel flexible MEMS technology can benefit the development of other new flexible polyimide-based devices.     

适用于大功率光电芯片散热的一体化平板热管

为解决大功率光电芯片散热问题,构造了一种新结构一体化平板热管。利用超轻多孔泡沫金属作为毛细吸液芯,以水、丙酮和乙醇为工质,在不同充液比、加热功率和倾角条件下对新结构热管的热性能进行了研究,结果表明,这种新结构平板热管不仅消除了热管与散热片间的接触热阻,而且使整个散热翅片也处于均温状态,当功率达到380W、热流密度超过445 W/cm2时,热管仍具有较好的均温特性,且热阻较小,可达0.04℃/W。在3种工质中,水是最佳工质选择,且当充液比为30%时具有较好的效果。实验表明,以泡沫金属为吸液芯的新结构一体化平板热管具有很好的传热性能,并扩展了承载大热流密度的能力。     

Closed-loop electroosmotic microchannel cooling system for VLSI circuits

The increasing heat generation rates in VLSI circuits motivate research on compact cooling technologies with low thermal resistance. This paper develops a closed-loop two-phase microchannel cooling system using electroosmotic pumping for the working fluid. The design, fabrication, and open-loop performance of the heat exchanger and pump are summarized. The silicon heat exchanger, which attaches to the test chip (1 cm/sup 2/), achieves junction-fluid resistance near 0.1 K/W using 40 plasma-etched channels with hydraulic diameter of 100 /spl mu/m. The electroosmotic pump, made of an ultrafine porous glass frit with working volume of 1.4 cm/sup 3/, achieves maximum backpressure and flowrate of 160 kPa and 7 ml/min, respectively, using 1 mM buffered de-ionized water as working fluid. The closed-loop system removes 38 W with pump power of 2 W and junction-ambient thermal resistance near 2.5 K/W. Further research is expected to strongly reduce the thermal resistance for a given heating power by optimizing the saturation temperature, increasing the pump flowrate, eliminating the thermal grease, and optimizing the heat exchanger dimensions.     

A liquid cooling solution for temperature redistribution in 3D IC architectures

The advancement of contemporary three-dimensional integrated circuit (3D IC) technologies offers a promising solution for the insatiable demand of the consumer electronics market. The increased complexity of 3D IC design permits the execution of multiple applications at greater speeds whilst remaining within the design constraints of energy consumption, yield and time-to-market. However, the increased computing performance and compact size may introduce a thermal barrier inhibiting performance, particularly in the case where multiple logic die are stacked and co-aligned hotspots are induced. To mitigate this thermal barrier a novel integrated active thermal solution is investigated in this paper whose purpose is to alleviate hotspots in a contemporary two-die 3D IC architecture. The solution employs a series of integrated microchannels, which permits the transfer of heat, via a coolant, from lower to upper strata. This microfluidic system is driven by a series of integrated AC electrokinetic pumps embedded in the channel walls. Recent advancements in electrokinetic micropump technology have allowed greater increases in fluid velocity – to an order of mm/s – while operating within the voltage constraints of a 3D IC. Numerically qualitative and quantitative temperature distributions are presented for a 3D IC chip design both with and without microchannels for a constant heat flux on the active layer of each silicon chip. The implementation of a microchannel network is shown to alter the thermal distribution map within a 3D IC package creating hot and cold zones with variations on temperature of ?14.6 °C≤ΔT≤9.8 °C with a ΔT_max of ?6.5 °C in the silicon die stack (equivalent to a total maximum heat flux, q_max″, of approximately 112.5 W/cm²). Increasing bulk fluid velocity, within the range 1.3 mm/s≤u_avg≤13 mm/s, can vary the area of the cold zone enhancing heat transfer and reducing the temperature of the die stack without an overall temperature change in the package.     

Micromachined thermally based CMOS microsensors

An integrated circuit (IC) approach to thermal microsensors is presented. The focus is on thermal sensors with on-chip bias and signal conditioning circuits made by industrial complementary metal-oxide-semiconductor (CMOS) IC technology in combination with post-CMOS micromachining or deposition techniques. CMOS materials and physical effects pertinent to thermal sensors are summarized together with basic structures used for microheaters, thermistors, thermocouples, thermal isolation, and heat sinks. As examples of sensors using temperature measurement, we present micromachined CMOS radiation sensors and thermal converters. Examples for sensors based on thermal actuation include thermal flow and pressure sensors, as well as thermally excited microresonators for position and chemical sensing. We also address sensors for the characterization of process-dependent thermal properties of CMOS materials, such as thermal conductivity, Seebeck coefficient, and heat capacity, whose knowledge is indispensable for thermal sensor design. Last, two complete packaged microsystems-a thermoelectric air-flow sensor and a thermoelectric infrared intrusion detector-are reported as demonstrators     

Constant-temperature integrated vacuum sensor

An integrated vacuum sensor based on heat transfer at a constant chip temperature (CCT) is introduced. It consists of a temperature-sensing stage, a CMOS op-amp and a heating branch circuit. All three part are integrated on one chip and connected to form a negative feedback loop for CCT operation. The heating power of the sensor chip was used to indicate the vacuum which affects the heat transfer between the chip and the vacuum ambient     

集成pH－ISFET／压力传感器的研究

基于ＳＤＢ／ＳＯＩ材料和硅微机械加工技术，提出了一种含微参比电极和择优差分补偿单元的背面引线ＰＨ－ＩＳＦＥＴ／压力传感器的新结构。并且设计了高稳定的可调芯片自恒温系统，以减少硅材料对温度敏感的效应。这种结构既方便地实现敏感元和信号处理电路的完全隔离，又有效地改善了敏感特性和稳定性。初步实验结果证实了新结构设计是成功的。     

集成pH－ISFET／压力传感器的研究

基于ＳＤＢ／ＳＯＩ材料和硅微机械加工技术，提出了一种含微参比电极和择优差分补偿单元的背面引线ＰＨ－ＩＳＦＥＴ／压力传感器的新结构。并且设计了高稳定的可调芯片自恒温系统，以减少硅材料对温度敏感的效应。这种结构既方便地实现敏感元和信号处理电路的完全隔离，又有效地改善了敏感特性和稳定性。初步实验结果证实了新结构设计是成功的。     

用于迫弹速度测量的柔性MEMS流速传感器仿真

大部分迫弹采用引信涡轮发电机兼作为弹道辨识用的速度传感器,但是涡轮发电机存在着低速停转和高速限速等测速问题.设计了一种贴装在引信上测量迫弹飞行速度的宽量程柔性MEMS流速传感器.利用有限元仿真软件对迫弹引信进行了流场仿真,确定了流速传感器在引信进气道内的贴装位置,并对传感器进行了热-流场耦合仿真.引信流场仿真表明,拉法尔管进气道后端壁面处流速与迫弹飞行速度为近似线性关系:迫弹飞行速度0～350 m/s对应壁面流速为0～75 m/s.进气道内安装的柔性流速传感器的热-流场耦合仿真表明,由传感器加热电阻的加热功率和三个测温电阻对的温度差可测量0.01～75 m/s的流速,这为传感器用于迫弹的弹道辨识奠定了理论基础.     

微型星敏热控设计及仿真

为了保证应用平台在轨任务期间的星敏感器正常工作,需要对其进行热设计。结合微型星敏感器组件的空间环境外热流、安装布局以及工作模式等条件,在热分析优化的流程上考虑了光机热等多种因素影响,设计了微型星敏感器组件的热控方案。该热控方案提出采用主动电加热以及遮光罩与星敏本体均温化的设计思路,解决了微型星敏感器组件在轨期间的空间热环境复杂、温度控制要求高、散热途径受限于安装结构等问题,保障了微型星敏感器组件有效、可靠的工作。建立了I-DEAS /TMG 有限元分析模型,开展了高、低温工况下的星敏感器组件的热控仿真,分析了星敏感器组件的温度分布以及均匀性等仿真结果,最后进行了地面试验,验证了热控方案的正确性,满足星敏感器组件热设计要求。文中工作可为后续在轨平台的微型星敏热设计提供参考。