Drop failure modes of Sn-3.0Ag-0.5Cu solder joints in wafer level chip scale package

To reveal the drop failure modes of the wafer level chip scale packages （WLCSPs） with Sn-3.0Ag-0.5Cu solder joints, board level drop tests were performed according to the JEDEC standard. Six failure modes were identified, i.e., short FR-4 cracks and complete FR-4 cracks at the printing circuit board （PCB） side, split between redistribution layer （RDL） and Cu under bump metallization （UBM）, RDL fracture, bulk cracks and partial bulk and intermetallic compound （IMC） cracks at the chip side. For the outmost solder joints, complete FR-4 cracks tended to occur, due to large deformation of PCB and low strength of FR-4 dielectric layer. The formation of complete FR-4 cracks largely absorbed the impact energy, resulting in the absence of other failure modes. For the inner solder joints, the absorption of impact energy by the short FR-4 cracks was limited, resulting in other failure modes at the chip side.

Integrated power electronics module based on chip scale packaged power devices

High performance can be obtained for the integrated power electronics module（IPEM） by using a three-dimensional packaging structure instead of a planar structure. A three- dimensional packaged half bridge-IPEM （HB-IPEM）, consisting of two chip scale packaged MOSFETs and the corresponding gate driver and protection circuits, is fabricated at the laboratory. The reliability of the IPEM is controlled from the shape design of solder joints and the control of assembly process parameters. The parasitic parameters are extracted using Agilent 4395A impedance analyzer for building the parasitic parameter model of the HB- IPEM. A 12 V/3 A output synchronous rectifier Buck converter using the HB-IPEM is built to test the electrical performance of the HB-IPEM. Low voltage spikes on two MOSFETs illustrate that the three-dimensional package of the HB-IPEM can decrease parasitic inductance. Temperature distribution simulation results of the HB-IPEM using FLOTHERM are given. Heat dissipation of the solder joints makes the peak junction temperature of the chip drop obviously. The package realizes three-dimensional heat dissipation and has better thermal management.

美国黄金鲈的育苗技术

美国黄金鲈仔苗的培育方式有两种: A.高蛋白网箱培育法:此法投资略大,要求高,调配各生长阶段的饵料含量及安排各环节的不同培育方法,是以不改变它的食性为目的培育法. B.高密度多极饲养法:此法投入少、食性转换率高,操作简便,有利于成鱼的主养,对广大繁、养殖者来讲效率更加显著.为此,就此培育方法向广大繁养殖朋友作如下介绍.

六月上旬广州清平药市动态

天气日趋炎热,很多中药材均难过炎热夏季保管关,故各家进货多是宁少勿多,市场购销显得清淡,交投多属零星。潞党参(白条党)的选装佳品货趋少,现市上所售多为打扁的二等品,也有许多是小条纹党而冒充“佳品”。质量一般者每斤22元(公斤下同),较年初18元缓升22.2％,交投多为小批量。内蒙黄寸片每斤13元,山西混片每斤10元,河北。

姑苏行

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长翅膀的“鱼儿”

想象一下,“长翅膀的鱼儿”是什么样子的? 在世界的瞳仁的一个小角落里,有一片金黄的麦田。用眼睛摸一下,哦,它是软软的、厚厚的、暖暖的。上面是蓝色的水晶一样的天空。听说一个叫作风的姑娘经常会用感动的眼泪来擦洗它。这么大一片天空.真得用最纯净的眼泪来擦洗呀。所以在这个故事的开头,我们要谢谢这个擦天的风姑娘啊。没有她,这个故事也不会有一片美丽的天空。

Improved charge transfer by size-dependent plasmonic Au on C_3N_4 for efficient photocatalytic oxidation of RhB and CO_2 reduction

A series of Au/g-C3N4(Au/CN)nanocomposites were successfully prepared,where g-C3N4 nanosheets(CN NSs)served as a substrate for the growth of different sized Au nanoparticles(Au NPs)using the constant temperature bath-reduction method.The effect of Au NP size on electron transfer efficiency between the interfaces of the nanocomposite was studied.The three-dimensional finite-difference time-domain results revealed that larger Au NPs showed increased strength of the localized surface plasmon resonance effect.An increased number of high-energy electrons were available for transfer from Au NPs to CN under the visible light irradiation,inhibiting electron transfer from CN to Au NPs.Photoelectrochemical performance analysis showed that smaller Au NPs exhibited higher separation efficiency of the electron-hole pairs photo-generated with reasonable distribution density.These results are favorable for the improvement of photocatalytic performance.Compared to other nanocomposites,the 3-Au/CN sample(prepared using 3 mL HAuCl4 solution)with reasonable distribution density and small Au NPs exhibited the best photodegradation activity(92.66%)of RhB in 30 min under the visible light irradiation and photoreduction performance of CO2 to CO and CH4 with yields of 77.5 and 38.5μmol/g,respectively,in 8 h under UV light irradiation.Considering the experimental results in the context of the literature,a corresponding size-dependent photocatalytic mechanism was proposed.

Influence of Shape and Size of Threshing Frame and Tobacco Grade on Leaf Strip Structure

This paper focused on the influence of the shape and size of threshing frames as well as the grades of tobacco leaves on the structure of threshed leaves.The testing tobacco leaves all came from the hilly ecological region of Nanling and belonged to burnt sweet,alcoholic sweet and scent category.The comprehensive evaluating value S was taken as the test index.Results showed that,without considering the influence of tobacco grade on leaf structure,the shapes of first-stage thresher five-link frames were all hexagons,and the combination with the sizes of 3.5,3.0,3.5,3.0,3.0 inches had the highest evaluating value S of 2.49.For tobacco grade C2FH,the shapes of first-stage thresher five-link frames were also hexagons,and the evaluating value S reached the highest value of 3.40 with sizes of 3.5,3.0,3.5,3.0,3.0 inches.Comprehensive analysis showed that:3.0 inch frame performed better in controlling the percentage of large-sized strips than 3.5 inch frame did;rhombic frames were better than hexagon frames in reducing the breakage rate of tobacco leaves;different shapes or sizes of nonadjacent two-link frames can help to improve the threshing quality.

Design of Image Signal Processor for Hardware Size

The Image sensor needs various image processing by Image Signal Processor （ISP） to improve image quality. Conventional cameras have their own software ISP functions to perform in PC instead of using commercial ISP chips. However these methods have problems such as large computation for image processing. In this paper, th authors proposed ISP that significantly reduced chip area by efficiently sharing of hardware and software. Large operation blocks are designed to hardware for high performances, and hardware is imployed simultaneously with software considering the size of the hardware. The implemented ISP can process Video Graphics Array （VGA） （640 ＊ 480） images and has 91 450 gates size in 0. 35 μm process.

Effect of brazing parameters on fillet size and microstructure of cladded fin-microchannel tube joints

This work concerns the optimization of furnace brazing conditions for joining micro-multiport aluminum tubes and fins made with AA4343/AA3003/AA4343 brazing sheet in mini-assemblies mimicking the core of an automotive heat exchanger.Taguchi method was used for design of experiment,considering five process parameters with two levels of values.The aim was to maximize the fillet size of the brazed joints,which has an important influence on the thermal integrity and mechanical properties.Fillet length measurements of brazed joints were performed with a metallographic microscope.The statistical analysis allowed to obtain the optimum values of process parameters(peak temperature,residence time,heating rate,microchannel tube type and flux).At a 95%confidence level,the variability of fillet length is most significantly affected by the peak brazing temperature(77%),residence time(15%)and heating rate(7%).The predicted maximum fillet length was(152±11)μm,which was corroborated by confirmation trials.The microstructural analysis of tube−fin joints showed that variations in peak temperature and residence time affect only the size of the eutectic zone of fillet formed,but not the nature or composition of the constituent phases.

Recycling of AZ91 Mg alloy through consolidation of machined chips by extrusion and ECAP

AZ91 Mg alloy recycled by a solid state process and equal channel angular pressing(ECAP)exhibited a superior strength. The mechanical properties of AZ91 Mg alloy recycled from machined chips by extrusion at 623 K and ECAP at 573 K and 623 K were compared with those of the reference alloy which was produced from an as-received AZ91 Mg alloy block under the same conditions as the recycled alloy.The recycled specimens show a higher strength at room temperature than the reference alloy.The improvement of the tensile properties is attributed not only to the small grain size,but also to the dispersed oxide contaminants.

Contribution to the Study and Analysis of the Lightning Aggression on the Wind Turbine

Generally, lightning damage has mainly been to home appliances and telephones, towers and power transmission and generation equipment mal functions and damage due to strikes on power lines. With the adoption of wind power generation equipment, however, lightning damage is also increasing in this area. Through his dimensional characteristics, the wind power system is more exposed in the nature compared to all others systems. Lightning damage is the single largest cause of unplanned downtime in wind turbines, and that downtime is responsible for the loss of countless megawatts of power generation. The wind turbines are important structures, since they can easily attract the wrath of storms hits heights close, they can also capture the most distant. The rotation of the blades may also trigger lightning and result in considerable increase in the number of strikes to a wind turbine unit. Since wind turbines are tall structures, the lightning currents that are injected by return strokes into the turbines will be affected by reflections at the top, at the bottom, and at the junction of the blades with the static base of the turbine. We present our contribution in this paper to study lightning strokes and their effects on the wind turbines with the aim to enrich the work and to suggest more effective means of protection against lightning.

图行天下

罗伊救世主欧洲杯开赛前.英国一家博彩公司在港口小城多佛尔竖起了一座英格兰队新主帅罗伊·霍奇森的雕像,雕像高达100英尺,造型取自巴西里约热内卢的耶稣雕像,头部自然换成了霍奇森,左胸加上了英格兰旗帜,底部加上了一个足球,底座上刻着ROY THEREDEEMER(罗伊救世主)字样,脸部正向着海峡对面的法国.有趣的是,英格兰队赛前多名主力伤退,内忧外患层出不穷,接手不久的霍奇森被广泛看低,但他却率队在前两轮逼平法国且打破了43年正赛不胜瑞典的魔咒,小组晋级前景光明——这样的罗伊还真成了英格兰的救世主!

Effects of Blade Geometry on Performance of Wells Turbine for Wave Power Conversion

An optimum design of the turbine would need a clear understanding of the influence of blade geometry on a Wells turbine performance. Practically, it is difficult to suggest the optimum geometry for the Wells turbine due to the complex interrelation among important parameters, the solidity, hub-to-tip ratio, aspect ratio, blade sweep of rotor, and so on. In the present study, the effect of blade geometry with the hub-to-tip and aspect ratios of rotor on the turbine performance was investigated with a numerical technique. As a result, the optimum blade geometry is as follows: the hub-to-tip ratio is about 0.7, and the aspect ratio about 0.5 under other constant important parameters, NACA0020 blade with blade sweep ratio of 0.35, and solidity of about 0.67. Furthermore, the detailed flow patterns for blade geometry were also shown and discussed in this paper.

No evidence of a generalized potential ‘cost’ of apical dominance for species that have strong apical dominance

When the shoot apical meristem of plants is damaged or removed,fecundity and/or plant growth may suffer(under-compensation),remain unaffected(compensation)or increase(overcompensation).The latter signifies a potential‘cost’of apical dominance.Using natural populations of 19 herbaceous angiosperm species with a conspicuously vertical,apically dominant growth form,we removed(clipped)the shoot apical meristem for replicate plants early in the growing season to test for a potential cost of apical dominance.Clipped and unclipped(control)plants had their near neighbours removed,and were harvested after flowering production had finished but before seed dispersal.Dry mass was measured separately for aboveground body size(shoots),leaves,seeds and fruits;and number of leaves,fruits and seeds per plant were counted.We predicted that:(i)our study species(because of their strong apically dominant growth form)would respond to shoot apical meristem removal with greater branching intensity,and thus overcompensation in terms of fecundity and/or biomass;and(ii)overcompensation is particularly enabled for species that produce smaller but more leaves,and hence with a larger bud bank of axillary meristems available for deployment in branching and/or fruit production.Widely variable compensatory capacities were recorded,and with no significant between-species relationship with leaf size or leafing intensity—thus indicating no generalized potential cost of apical dominance.Overall,the results point to species-specific treatment effects on meristem allocation patterns,and suggest importance for effects involving local variation in resource availability,and between-species variation in phenology,life history traits and susceptibility to herbivory.