基于NI DAQ的功率LED热特性测量分析系统

分析了功率发光二极管(LED)基于电学测量的热阻的测量方法,介绍了采用高性能数据采集卡构建了新型的功率LED热特性自动测量分析系统,实现对功率LED结温和热阻的精确、简便的测量.对几种典型功率LED样管的测试结果,与校正样品的标称值完全相符,并可对LED的瞬态热过程进行更深入分析.     

Emitter ballasting resistor design for, and current handlingcapability of AlGaAs/GaAs power heterojunction bipolar transistors

A systematic investigation of the emitter ballasting resistor for power heterojunction bipolar transistors (HBTs) is presented. The current handling capability of power HBTs is found to improve with ballasting resistance. An equation for the optimal ballasting resistance is presented, where the effects of thermal conductivity of the substrate material and the temperature coefficient of the ballasting resistor are taken into account. Current levels of 400 to 800 mA/mm of emitter periphery at case temperatures of 25 to -80°C for power AlGaAs/GaAs HBTs have been obtained using an on-chip lightly doped GaAs emitter ballasting resistor. Device temperature has been measured using both an infrared microradiometer and temperature-sensitive electrical parameters. Steady-state and transient thermal modeling are also performed. Although the measured temperature is spatially nonuniform, the modeling results show that such nonuniformities would occur for a uniform current distribution, as would be expected for an HBT with emitter ballasting resistors     

The pyroelectric detector of infrared radiation

The pyroelectric detector is a thermal sensor of infra-red radiation requiring no bias. While in principle a pure capacitor (hence theoretically noiseless), the detector has a varying noise contribution as a function of frequency due to a load resistor, series loss resistance, and amplifier. The actual sensor is a pyroelectric crystal exhibiting spontaneous polarization. The spontaneous polarization and dielectric constant of the crystal are temperature-dependent. A change in incident power raises the detector temperature causing an electric charge to appear across the electroded surfaces cut perpendicular to the crystal's ferroelectric axis. Under open circuit conditions, a voltage is obtained which is ultimately neutralized by current flow through the leakage resistance or load resistor. The evacuated detector package incorporates an electroded flake of triglycine sulfate mounted on a substrate of low thermal and electrical conductivity, a field effect transistor, load resistor, and an infrared transparent window. Data on the detectivity, responsivity, and noise as a function of frequency and area are presented. Polycrystalline pyroelectric detectors of TGS are feasible and simplify the construction of arrays and mosaics. Applications of the pyroelectric detector to date have been in a multielement line scanner, thermal imaging camera, spectrometer, and laser calorimeter.     

Calibration of resistance type die level temperature sensors usinga single temperature technique

Thermal test chips are widely used to develop electronic packaging thermal solutions and to evaluate electronic package assembly processes. Temperature sensors are an integral component on thermal test chips. Unfortunately, each temperature sensor must be calibrated in order for them to be effective. Each calibration can take up to one hour to complete. In a time when increasing sample sizes and shorter development cycles are taxing current equipment and manpower resources, new calibration techniques must be established to keep development costs down. This paper discusses simplified calibration procedures, which can significantly reduce the time needed for temperature sensor calibration. The simplified calibration procedures utilize single-resistance measurements either at room temperature or at the anticipated test temperature. For four different test chip designs included in the current study, calibration error variations less than ±0.6°C at a ±2σ confidence level are possible. The simplified calibration procedures can be applied to any resistor type temperature sensor that has a linear correlation between its electric resistive properties and temperature     

Thermal analysis of electromigration test structures

Analytical expressions are derived for estimating the temperature profile along a straight-line resistor test structure due to the joule heating generated by a high current-density stress, such as is used in accelerated stress tests to characterize metallizations for electromigration. It is shown how an improved estimate of the mean metallization stress temperature may be made and how the thickness and thermal conductivity of the underlying electrical insulator affect the temperature profile of the metallization. Recommendations for the design of electromigration test structures are developed that will promote reduced temperature gradients in the metallization during stress testing and improved reproducibility of electromigration characterizations.     

用AlN薄膜提高NiCr电阻网络的可靠性

采用低温反应射频溅射法在微晶玻璃上沉积了一层具有择优取向的氮化铝薄膜，再在其上沉积８０Ｎｉ－２０Ｃｒ电阻网络。对电阻网络进行了功率老化、高温存贮、热冲击等可靠性试验，结果表明具有ＡｌＮ薄膜的电阻网络性能得到很大提高     

Study of electric heating effects on carbon nanotube polymer composites

Carbon nanotube (CNT) composites are ideal materials for electric heating (E-heating) components owing to their lightweight, rapid heating ability, and easy processability for microscale patterns. However, careful consideration of their thermal stability and the effect of E-heating on CNT composites is necessary to ensure safety and long-term durability. Thermal degradation of CNT composites as a result of E-heating was found to be much more severe than air convection heating (C-heating). Enhanced mechanical properties of CNT composite were observed after 40 h C-heating, while E-heating composites became fragile that the matrix was severely damaged at the same temperature/hours. Consequently, the electrical resistance of the CNT composite for E-heating was dramatically increased. To avoid thermal degradation and a dramatic increase in resistance, the E-heating temperature should be much lower than the temperature limit of thermally stable polymer. In addition, thermal degradation of the polymer matrix could be relieved through the addition of CNTs, which can be understood as parallel resistor model, by spreading thermal concentration throughout the polymer matrix.     

Photovoltaics in a single dimension

Whereas the conversion of radiation in 3 dimensions into electrical work (e.g. solar energy conversion) gives rise to laborious numerical computation, the conversion efficiency of radiation in a single dimension (e.g. resistor noise) can be treated by simple analytical calculations. It turns out that a single diode converts 1-D radiation with an efficiency not exceeding 6[log (2)/π]² = 0.29, whereas the single junction solar cell is able to convert 3-D radiation with an efficiency up to 0.44. In an electrical network with non-uniform temperature, a diode is able to convert the thermal noise of a resistor into useful work with an efficiency equal to 0.29 times the square of the Carnot efficiency, a value substantially smaller than the Carnot efficiency itself.     

薄膜转移工艺制备的128×128规模高架桥式电阻阵

采用新的薄膜转移工艺,成功制备了128×128规模的高架桥式电阻阵。电阻阵的单元尺寸为50μm×50μm,占空比50%。初步测试了该高架桥电阻阵的两个基本指标,微桥的热时间常数和最高等效黑体温度,并对该电阻阵进行了成像实验。采用电学法测试单个微桥的时间常数τ约为4.5 ms,可在100Hz下工作。将整个面阵点亮,在8~12μm波段最高等效黑体温度达到250℃,推测在3~5μm波段最高等效黑体温度超过300±20℃。将整个器件全部点亮并驱动到最高温度时,器件的最大功率为30 W。该电阻阵可成功实现驱动显示成像。测试结果表明该高架桥式电阻阵初步满足红外景象产生器的要求。     

Lightly trimming the hybrids

Laser resistor trimming, an effective tool for producing accurate and reliable electrical elements is discussed. Laser trimming has minimum effect on power handling capability; element value variation with time, temperature, and voltage; and electrical noise. The principles of laser trimming, laser types used, trimming techniques, and technology trends are described. Laser cutting of ceramics in such applications as electronic packaging and the use of lasers to pattern thin films are also discussed     

Increased resistance in p-type poly-Si resistors by thermal annealreduction interface charge

The effect of thermal annealing on characteristics of p-type poly-Si thin-film resistors was investigated. A significant increase was observed as the source/drain anneal temperature or anneal time was increased. The increased resistance is due to a reduction in current component arising from field-enhanced current via grain-boundary trap states at the drain end of the resistor. The reduction is this field-enhanced current arises primarily from a reduction of positive charge density at the top and bottom oxide/poly-Si interfaces of the thin-film resistor (and thus a reduction in the magnitude of the drain electric field) with increased annealing temperature and time     

Infrared Image Series Automatic Registration and a History & Tendency Analysis

Infrared camera has been widely used in electrical power systems for predictive and preventive thermal fault diagnosis. Without historical IR images being considered, most thermograph analysis used at present are concerned with static image. The dynamic history and tendency analysis which compares the newly taken image with historical images is particularly attractive. Conclusions can be drawn from temperature variations rather than just from anomalous thermal pattern. However the spatial distortions prevent such dynamic analysis from being practicable. So the need to register infrared images arises. This paper proposes an automatic registration algorithm based on closed temperature contour matching for infrared image series of a target equipment taken at different times. Centroid Distance Function is used in image registration for the first time. The algorithm can remove spatial distortions, bring temperature variations into prominence and endow infrared camera with dynamic analysis ability. Experiment shows that the algorithm is simple, effective and extensible.     

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.     

Technique for thermal stabilization of transistors

An alternative scheme to transistor thermal stabilization by emitter resistor ballasting is proposed. The technique involves a resistor with a negative temperature coefficient of resistance connected across the emitter-base junction which bypasses excess base current that tends to be drawn due to local transistor heating.     

一种解决HBT功率器件热失控的新方法

提出了一种具有强耦合作用的新型镇流电阻器网络,该镇流电阻器网络为树形拓扑结构,对其工作原理进行了详细分析.基于COMSOL MULTIPHYSICS软件的仿真结果表明:该镇流电阻器网络具有自适应功能,通过其耦合作用可以自动调整HBT并联阵列中晶体管的电流,使高温HBT的热量向低温HBT传递,获得更为均匀的温度分布,较好...     

CO2激光辐照下热敏电阻温升的数值计算与实验

对激光照射下热敏电阻的温升进行计算,得到温升和热敏电阻输出信号与入射激光功率的关系：当激光功率小于热敏电阻的破坏阈值时,输出信号与激光功率近似线性关系;同时计算了破坏阈值的大小。实验采用CO2激光器,测量了热敏电阻输出信号与入射激光功率的曲线,分析表明,热敏电阻吸收激光能量造成的热破坏是主要原因,在允许的误差范围内,计算与实验结果基本一致。     

准光学馈电网络高精确度镜体结构热变形仿真分析

毫米波亚毫米波探测仪在静止轨道运行时,其各子系统性能受环境热辐射影响。根据在轨温度场数据,采用有限元分析法对准光学馈电网络热变形情况进行仿真;采用GRASP软件将器件热变形后的形位、形面参数进行拟合,仿真分析当准光馈电网络受在轨环境热辐射时电性能变化情况。结果表明,环境热辐射对准光学馈电网络的电性能有一定影响,采用温控措施后,可避免在轨温度变化引起的性能变化。     

基于虚拟仪器的温度测量系统

基于虚拟仪器技术,利用热电偶设计了一套温度测量系统,包括硬件和软件设计,硬件包括对热电偶输出信号的放大和滤波,以及对冷端温度的补偿电路,冷端温度通过Pt100热电阻进行测量;软件采用Labview进行编写,界面简洁,可通过图形化的界面对温度进行实时监测。     

用红外热像仪与红外测温仪诊断电气设备故障的对比研究

电气设备是故障多发装置。利用红外测温仪或红外热像仪能够检测出设备发热异常部位并确定其表面温度,再结合红外诊断标准便可对异常设备的故障严重程度进行判别,从而实现对电气设备的故障诊断。针对电气设备控制箱电气元件的发热缺陷,利用ST80+红外测温仪与FLIR E320红外热像仪进行了温度监测,并通过运用表面温度法和相对温差法进行故障严重程度诊断,对两种设备监测诊断的差异进行了分析。结果表明,利用红外热像仪能较准确地监测诊断出电气元件的过热缺陷,利用红外测温仪能检测出多数控制箱电气元件过热缺陷,但对部分缺陷的严重程度等级判别低于热像仪的判别结果。