行波管阴极和热子组件的热特性的数值模拟和实验研究

阴极热子组件作为星载行波管的核心部件,要求它具备稳定可靠、寿命长久、低功耗的特点。该文利用数值模拟和热测实验对某星载行波管阴极热子组件结构开展了研究,提出一种接触热阻估算方法,模拟了阴极热子组件结构热特性,设计并完成了阴极热子组件结构热测实验,首次获取了结构在一系列热子加热功率下由内到外的温度实测数据。进一步,通过修正阴极热子组件结构热模拟边界及激励,迭代得到接触热阻值,获取了一种高可靠的阴极热子组件结构热模型,实验表明,该热模型阴极温度计算精度在5%以内,结构最大温度计算误差不超过72 C。     

降低空间行波管热子功率的仿真研究

本文用Ansys热分析技术研究了某一空间行波管电子枪的阴极热屏组件中影响热子功率的诸多因素,提出了结构改进措施,并用Abaqus力学分析技术对新结构进行了抗力学环境能力分析。在未改变阴极面尺寸、阴极面温度以及可直接安装到原组件位置的前提下,新结构可将热子功率从4.4W降低到2.5W,预热时间和抗力学环境能力亦可满足要求。     

辐射型加热磁控注入电子枪温度均匀性和热形变分析

基于140 GHz兆瓦级回旋振荡器电子枪设计和研制,利用ANSYS热分析软件,建立相应的磁控注入电子枪模型,分析电子枪工作时阴极温度均匀性及热形变,尝试通过相关几何和电参数的调整,在改善阴极温度均匀性的基础上,尽可能消除热形变对电子轨迹质量的影响。通过对比相同加热功率下阴极发射带的实测温度及仿真温度,评价了仿真模型及结果的合理性,为阴极组件的实际设计提供了参考数据。     

电子器件

0625889太赫兹回旋管的计算机模拟〔刊,中〕/黄震//重庆邮电学院学报(自然科学版).—2006,(6).—221-223(C)0625890在FPGA下实现灵活的OLED灰度控制〔刊,中〕/付新虎//液晶与显示.—2006,21(3).—260-264(C)0625891用于空间行波管的高效率覆膜阴极组件的研究〔刊,中〕/刘燕文//真空科学与技术学报.—2006,26(3).—240-242(L)首先设计并研制出符合空间行波管要求的高效覆膜阴极组件,采用高温钨-钴焊料,将阴极焊接在阴极筒上,增加了阴极的耐冲击性能,阴极组件采用两层热屏,第一层热屏采用热传导率低的金属钛,提高了阴极组件的热效率,其加…     

热子可靠性研究

本文对钡钨阴极热子的可靠性作了分析,提出了几种解决办法,并叙述了阴极热子组件中热子腿的局部过热问题及解决途径。     

红外热成像技术在铜电解电流分布测量中的应用

针对铜电解槽中阴极棒电流值无法实时测量的问题,应用红外热成像技术采集电解槽阴极棒的红外图像。对原始图像进行处理与分析的基础上,获取阴极棒的表面温度值。其次,通过理论分析与数据验证,结合COMSOL仿真软件数据建立了温度与电流之间的函数关系模型,进而求出电流值。对比实测电流值与模型电流值,结果表明:电解槽的总电流误差均在±5%以内,各阴极棒的电流误差基本在±12%以内,仅个别阴极棒电流误差偏大。该方法不仅实现了对阴极棒电流值的在线监测,而且对极间短路故障的检测提供了依据。     

空间行波管电子枪阴极温度拟合计算研究

工作温度是影响阴极发射能力和寿命的关键参数,其与电子枪保温结构、加热功率、环境温度相关,未经实测时不同加热功率和环境温度下的阴极温度往往较难确定。本文利用温度试验数据构建并拟合出简化的空间行波管电子枪热节点模型,通过热节点模型推算出不同加热功率和环境温度下的阴极温度,与实测温度比较验证了模型的准确性。此构建拟合热节点模型的方法为推算电子枪阴极温度提供了一种简便途径。     

回旋行波管高质量阴极及电子枪研究

回旋行波管对回旋电子注参数（纵横速度比、速度零散等）非常敏感,实验中需进行电子参数调节,高质量电子枪研制是整管设计核心之一。基于理论分析、结构分析及热分析等对回旋行波管电子枪进行改进设计,对阴极、热子进行优化设计,研发的电子枪速度零散＜2%,优于国际报道的3%。项目在热分析和形变分析基础上,改进了阴极结构及制备工艺,显著提高了热子加热效率,将阴极加热功率从100W降低至50W左右,提升了阴极发射的均匀性和稳定性,10%工作比下长时间工作稳定、可靠,有效保障了阴极寿命,新研电子枪在Ka频段回旋行波管装管实验,脉冲功率100kW,平均功率10kW,连续工作稳定、可靠。     

复合式热屏对φ200mm CZSi单晶生长速率和氧含量的影响

对φ200mm太阳能CZSi单晶生长的传统热场进行了改进,施加了复合式热屏.对改进前后热场温度梯度、单晶氧含量进行了实验分析,并对该系统的氩气流场进行了数值模拟.研究了复合式热屏影响拉速和单晶氧含量的机理.实验表明本文采用的复合式热屏和氩气流场可以提高拉速,降低硅单晶氧含量.     

复合式热屏对Φ200mm CZSi单晶生长速率和氧含量的影响

对Φ200mm太阳能CZSi单晶生长的传统热场进行了改进，施加了复合式热屏. 对改进前后热场温度梯度、单晶氧含量进行了实验分析，并对该系统的氩气流场进行了数值模拟. 研究了复合式热屏影响拉速和单晶氧含量的机理. 实验表明本文采用的复合式热屏和氩气流场可以提高拉速，降低硅单晶氧含量.     

The use of rapid thermal processing to control dopant redistribution during formation of tantalum and molybdenum silicide/n+polysilicon bilayers

The successful use of rapid thermal processing (RTP) to form Ta- and Mo-polycide structures is described. Samples were annealed by exposure to the blackbody radiation of a resistively-heated graphite heater in vacuum. Rapid redistribution of phosphorus in the bilayer structure is observed during the sintering process. Long-time high-temperature anneals can result in significant loss of dopant from the polycide structure. Data is presented to show that RTP parameters can be optimized to produce highly-conductive polycide structures with minimal dopant loss from the poly-Si layer, which is not possible for furnace-annealed samples.     

Impact of thinning stacked dies on the thermal resistance of bump-bonded three-dimensional integrated circuits

In three-dimensional integrated circuits (3DICs) aggressive wafer-thinning can lead to large thermal gradients, including spikes in individual device temperatures. In a non-thinned circuit, the large bulk silicon wafer on which devices are built works as a very good thermal conductor, enabling heat to diffuse laterally. In this paper we experimentally examine the thermal resistance from an active on-chip heater to the heatsink in a two-tier bump-bonded 3D stacked system. A simplified structure is introduced to enable such measurements without the time and cost associated with the full fabrication of such a system. Die thinning is seen to have a pronounced effect on the thermal response, which can adversely affect system reliability. Thinning the top tier from 725 μm to 20 μm resulted in a nearly 4 times increase in the normalized temperature rise of the heater of our test chip.     

Microjet cooling devices for thermal management of electronics

This research is an effort to demonstrate the applicability of miniaturized synthetic jet (microjet) technology to the area of thermal management of microelectronic devices. Synthetic jets are jets which are formed from entrainment and expulsion of the fluid in which they are embedded. Design issues of microjet cooling devices are discussed along with characterization of excitation elements and the turbulent synthetic jets produced thereby. Geometrical parameters of the microjet cooling devices were empirically optimized with regards to cooling performance. The cooling performance of the optimized microjets was compared with previous theoretical and empirical studies of conventional jet impingement. The cooling performance of the microjet devices has been investigated in an open environment as well as in a vented and closed case environment. In such experiments, the synthetic jet impinges normal to the surface of a packaged thermal test die, comprising a heater and a diode-based temperature sensor. This test assembly allows simultaneous heat generation and temperature sensing of the package, thereby enabling assessment of the performance of the synthetic jet. Using microjet cooling devices, a thermal resistance of 30.1/spl deg/C/W has been achieved (when unforced cooling is used, thermal resistance is 59.6/spl deg/C/W) when the test chip is located at 15mm spacing from the jet exit plane. In order to more directly compare and scale the cooling results, a preliminary study on heat transfer correlations of the microjet cooling device has been performed. Finally, a comparison of the performance of the microjet cooler with standard cooling fans is given.     

PCB板级电路中高效散热结构的优化设计

印制电路板(PCB)厚度方向的导热系数比平面方向的导热系数小得多,为了改善板厚度方向的导热性能,提出了一种改进的自然对流冷却散热方式。首先,通过在PCB板中设计热过孔并在其背面安装散热器,应用热分析软件Icepak对散热模型进行仿真,优化设计散热器翅片的厚度和数目对功率器件温度分布的影响;然后,根据优化后的结果,选定最佳修正尺寸,制作测试结构;最后,采用热电偶法对其进行实验测试,结果表明此散热结构可有效降低器件的温度。     

Polymeric optical waveguide switch using the thermooptic effect

An all-polymeric optical waveguide switch which uses total internal reflection from a thermally induced index barrier is discussed. Very large effective index changes ΔN=2×10^-2 were found in the polymeric waveguide. The temperature under the evaporated stripe heater was measured from the change in its resistance. The effective index change due to the temperature increase agrees well with values calculated from the deflection angles. The operation of the switch is, apart from a small waveguide dispersion effect, polarization-insensitive. Switching times of about 10 ms were measured. It should be possible to reduce them to a few milliseconds in optimized thermal designs and with regulated power dissipation in the heater     

Bias temperature instability assessment of n- and p-channel MOS transistors using a polysilicon resistive heated scribe lane test structure

A fast wafer level device reliability stress at elevated temperatures is demonstrated. It neither needs an external heat source like a thermal chuck or an oven nor cooling. The necessary temperature for acceleration of the bias temperature stress drift mechanism is achieved by electrically resistive heating. For this reason a polycrystalline silicon (polysilicon) resistive heated test structure was designed with a MOSFET embedded between two polysilicon heater strips. A 4-terminal metal resistor above the heater allows temperature control via the temperature coefficient of the resistance. The stress algorithm performs simultaneous thermal and electrical stress. The device temperature is determined by a comparison of the temperature measured at the metal level and the pn-junction temperature determined from the forward diode characteristics. Results of an assessment of the bias temperature instability of CMOS transistors using this type of structure are discussed. They demonstrate the usefulness of the whole methodology presented.     

基于非对称热结构的激光热稳频系统

针对目前热稳频激光器抗干扰能力差的问题,研制了一种基于非对称热结构的激光热稳频系统.该系统采用不同热传导材料建立具有多个连续热传导层的热结构,其中电热控制层和干扰吸收层被有限导热层隔离并呈不对称的热传导特性.由于有限导热层的隔离作用,电热控制和环境干扰对激光管的热作用速度分别取决于电热控制层和干扰吸收层的热惯性大小.结构参数设计中使电热控制层的热惯性远小于干扰吸收层,则可在保证电热控制效率的同时降低环境干扰的作用速度,从而提高稳频系统的抗干扰性能.最后,建立基于非对称热结构的纵向塞曼激光热稳频系统,对其抗干扰特性进行验证.实验结果表明:在普通实验室条件下稳频系统的频率稳定度优于1.8×10-10,而在1 m/s的持续气流扰动下其频率波动<1.5×10-9.     

Design and simulation of micromechanical thermal converter for RF power sensor microsystem

This paper discusses the thermo-mechanical simulations performed with the aim to optimize the temperature distribution of the microwave power sensor (MPS) microsystem keeping the thermal stress as low as possible. The concept of the absorbed power measurement is based on a thermal conversion, where the dissipated or absorbed RF power is converted into the thermal power, inside a thermally isolated system, so-called the micromechanical thermal converter (MTC) device. A new MTC approach uses a GaAs with an active high electron mobility transistor (HEMT) heater. New technology of low stress polyimide has been used for MTC thermal isolation.By means of thermo-mechanical simulations, we propose a GaAs micromechanical thermal converter design and a layout of the active sensor elements (HEMT heater and a temperature sensor TS) placed on the MTC structure. Spatial temperature distribution, thermal time constant, thermal stress and displacement and the power to temperature characteristics are calculated from the heat distribution. These findings are compared with results of thermo-mechanical measurement of real micromachined MTC devices. The 3-D thermal and thermo-mechanical simulations were performed, using the CoventorWare simulator.     

微波加热沥青系统中辐射器结构的优化设计

先通过微波工作室CST软件仿真计算,并结合波导设计理论对某公司原有辐射器结构进行场分析,然后对磁控管的安装位置与辐射器结构进行了优化设计.优化后的结构与优化前相比较明显降低了反射,并得到了实验验证.此优化不仅满足了加热效率的需求,也有利于磁控管的寿命.     

含双层GST的低功耗CRAM存储元结构设计

基于热场分析,在CRAM存储元传统结构的加热层和底电极之间插入一层存储介质GST,设计出含双层GST的CRAM存储元结构.在模拟存储元热场分布过程中引入热辐射边界条件,使模拟结果更接近实际.根据设计要求,将双层GST新型结构与传统结构的热场进行比较,结果表明,含双层GST的新型结构一方面实现了存储元与CMOS晶体管的热兼容,增强了器件的稳定性;另一方面,将reset电流减小到0.5 mA,降低了器件功耗.