Kinetics of AuSn4 migration in lead-free solders

The relatively fast diffusion of Au atoms in eutectic PbSn matrix is considered one of the contributing factors to the Au embrittlement problem. In this study, we further investigated the Au embrittlement problem in high-Sn solders. Experimentally, Sn3.5Ag (wt.%) spheres with 500-μm diameter were soldered over the Au/Ni soldering pads. It was found that some of the AuSn₄ needles that formed after reflow inside the solder migrated back to the solder/pad interface during thermal aging. However, the migration kinetics in high-Sn solders was slower compared to that in eutectic PbSn. The difference in migration kinetics of AuSn₄ in eutectic PbSn and SnAg was ascribed to the difference in the magnitudes of the Au flux and the Ni flux. In eutectic PbSn, the Au flux was much greater than that of the Ni flux, and the Au and Ni flux were in the same order of magnitude in eutectic SnAg. The relative magnitude of the Au and Ni flux changed in eutectic PbSn and SnAg because the homologous temperatures of PbSn and SnAg were different.     

meso-四（3-三氟甲基苯基）卟啉与锌的微波催化显色反应的研究

研究了用新显色剂meso-四(3-三氟甲基苯基)卟啉(T(3-TFMP)P)光度法测定痕量锌(Ⅱ)时微波对于显色反应的催化作用和微波操作条件.实验表明,在pH 10.8的缓冲液、Tween-80及盐酸羟胺介质中,经微波加热50 min,显色反应完全,锌(Ⅱ)量在0～4.0 μg/25 mL范围内具有线性关系,表观摩尔吸光系数ε429为5.13×105 L·mol<-1·cm-1.采用加入CyDTA进行退色光度法测定,同时加入混合掩蔽剂,可以消除大多数共存离子的干扰.方法可应用于三甘醇和保健品中痕量锌(Ⅱ)的测定.     

《石油沥青纸胎油毡》国家标准的修订

《石油沥青纸胎油毡》国家标准进行了第三次修订。本文介绍了修订的理由、修订的内容与依据，并与国内外同类产品标准进行了比较。     

绿色理念的内涵拓展与绿色图书馆建设

绿色图书馆是图书馆学的一个新的研究方向和发展趋势.文章首先深刻挖掘绿色内涵的本质,阐述正确理解绿色图书馆的含义,接着探讨了绿色图书馆建设的要素取向,从而明确了现阶段发展绿色图书馆的必要性.     

凤滩水电厂自动发电控制策略

介绍了凤滩水电厂自动发电控制(AGC)策略的实现方法,重点介绍了修正等容量比例有功分配方法及相应措施.程序设计的原则是,机组紧跟目标负荷的情况下,在最佳效率下运行,同时减少机组开/停机次数、有功调节频率和跨越振动区次数,从而减少机组磨损,兼顾运行效率和机组运行安全.     

A Single-Die 124 dB Stereo Audio Delta-Sigma ADC With 111 dB THD

This paper presents a highly power-efficient stereo delta-sigma ADC designed for high-precision applications, with measured inter-channel isolation over 130 dB. This design adopts a single-loop, fifth-order, 33 level analog modulator with positive and negative feedforward paths. An interpolated multilevel quantizer with unevenly weighted quantization levels replaces a conventional 5-bit flash type quantizer. These new techniques suppress signal dependent energy inside the delta-sigma loop, reduce internal channel coupling and power consumption. Manufactured in 0.35 mum double poly, three metal CMOS process, the single-die chip includes two analog modulators, on-chip bandgap reference circuit, decimation filter and serial interface circuits. The core die area is around 14.8 mm². The ADC achieves 124 dB dynamic range (A-weighted), -111 dB THD over 20 kHz bandwidth. Total power consumption is less than 330 mW.