Polymer-Protected Cu-Ag Mixed NPs for Low-Temperature Bonding Application

A simple method has been proposed to prepare polymer-protected Cu-Ag mixed nanoparticles (NPs), which are suitable for use as low-temperature bonding materials. The polymer coated on the Cu-Ag mixed NPs can protect them from oxidation effectively when heated in air at temperature lower than 280°C. The low-temperature bonding process utilizing Cu-Ag mixed NPs as the bonding material is investigated. The bonding experiments show that robust joints are formed using Cu-Ag mixed NPs at 160°C in air. The shear test shows that addition of copper to silver is helpful for improving joint strength. This novel sintering-bonding technology using Cu-Ag mixed NPs as an interconnection material has potential for application in the electronics packaging industry.     

温度对高精度光学玻璃折射率均匀性检测的影响

为了实现光学玻璃折射率均匀性的高精度(0.2×10-6)检测,测量环境温度引入的测量不确定度应小于0.05×10-6。对测量过程中温度引入的不确定度进行了详细分析,总结了温度引起的5种误差源,对各种误差源进行了不确定度分析。结果表明,当测量腔中空气、贴置板、折射率液及被测件的径向温差不超过±0.01℃时,温度引起的测量不确定度为0.031×10-6,满足精度要求。为实验室环境的改造提出了建议,并为高精度玻璃折射率均匀性测量提供了分析数据。     

Investigation of optical and electronic properties in Al–Sn co-doped ZnO thin films

Al-Sn co-doped ZnO thin films were deposited onto quartz substrates by sol-gel processing. The surface morphology and electrical and optical properties were investigated at different annealing temperatures. The surface morphology showed a closely packed arrangement of crystallites in all the doped films. As prepared co-doped films show a preferred orientation along an (0 0 2) plane. This preferred orientation was enhanced by increasing the annealing temperature to between 400 °C and 500 °C, but there was a shift to the (1 0 1) plane when the annealing temperature rose above 500 °C. These samples show, on average, 91.2% optical transmittance in the visible range. In this study, the optical band gap of all the doped films was broadened compared with pure ZnO, regardless of the different annealing temperature. The carrier concentration and carrier mobility of the thin films were also investigated.     

GS-DFB半导体激光器的光自注入技术

报道了一种光脉冲自注入的新方法 ,它能使增益开关 DFB激光器输出光脉冲的时间抖动从 5.7ps减小到 1.2 ps,分析了注入光延迟时间及功率对时间抖动的影响 ,指出为取得抑制时间抖动的最佳效果 ,必须选择合适的反馈光脉冲延迟时间和适当的反馈光功率。实验中观察到在增益开关 DFB激光器光脉冲建立期间注入反馈光时 ,输出光脉冲会发生严重畸变。     

Bus-driven floorplanning with thermal consideration

As the increasing number of buses in multi-core SoC designs, bus planning problems become a dominant factor in determining the chip performance. To cope with these issues, it is desirable to consider them in the early floorplanning stage. Recently, many bus-driven floorplanners have been proposed in the literature. However, these proposed algorithms only consider the bus planning problem without the thermal effect. As a result, there are hotspots, which result in high chip temperature, on the chip. In this paper, a thermal-driven bus-driven floorplanning algorithm is proposed to separate hotspots during the perturbation stage and to keep buses away from hotspots during the routing stage. To avoid time-consuming thermal simulations, the superposition of thermal profiles, which are the thermal distribution of each module, is adopted to efficiently estimate the module temperature. Compared with the state-of-the-art bus-driven floorplanner, experimental results demonstrate that the proposed algorithm can effectively separate hotspots and reduce the chip temperature.     

Emulsion polymerization: State of the art in kinetics and mechanisms

Over decades of carefully designed kinetic experiments and the development of complementary theory, a more or less complete picture of the mechanisms that govern emulsion polymerization systems has been established. This required means of determining the rate coefficients for the individual processes as functions of controllable variables such as initiator concentration and particle size, means of interpreting the data with a minimum of model-based assumptions, and the need to perform experiments that had the potential to actually refute a given mechanistic hypothesis. Significant advances have been made within the area of understanding interfacial processes such as radical entry and exit into and out of an emulsion polymerization particle, for electrostatic, steric and electrosteric stabilizers (the latter two being poorly understood until recently). The mechanism for radical exit is chain transfer to monomer within the particle interior to form a monomeric radical which can either diffuse into the water phase or propagate to form a more hydrophobic species which cannot exit. Entry is through aqueous-phase propagation of a radical derived directly from initiator, until a critical degree of polymerization z is reached; the value of z is such that the z-meric species is sufficiently surface active so that its only fate is to enter, whereas smaller aqueous-phase radical species can either be terminated in the aqueous phase or undergo further propagation. For both entry and exit, in the presence of (electro)steric stabilizers, two additional events are significant: transfer involving a labile hydrogen atom within the stabilizing layer to form a mid-chain radical which is slow to propagate and quick to terminate, and which may also undergo β-scission to form a water-soluble species. Proper consideration of the fates of the various aqueous-phase radicals is essential for understanding the overall kinetic behaviour. Intra-particle termination is explained in terms of diffusion-controlled chain-length-dependent events. A knowledge of the events controlling entry and exit, including the recent discoveries of the additional mechanisms operating with (electro)steric stabilizers, provides an extension to the micellar and homogeneous nucleation models which enables particle number to be predicted with acceptable reliability, and also quantifies the amount of secondary nucleation occurring during seeded growth. This knowledge provides tools to understand the kinetics of emulsion polymerization, in both conventional and controlled/living polymerization systems, and to optimize reaction conditions to synthesize better polymer products.