气氛对无铅回流焊的影响

无铅化进程给电子组装带来了一系列的新问题。主要阐述了气氛对无铅回流焊工艺和性能的影响。与锡铅焊料相比,无铅焊料的熔点高、润湿性差和工艺窗口窄等一系列问题给无铅回流焊带来了新的挑战。焊接时以氮气作为保护气氛对提高可焊性有明显的效果,惰性气体保护可以明显改善无铅焊料的润湿性,适当降低焊接温度,减少工艺缺陷,形成良好的焊点;此外,还原性气氛(如氢气)也能显著改善无铅回流焊焊点质量。     

电子焊料的无铅化及可靠性问题

随着环境保护意识的增强,人们更清楚意识到铅的剧毒性给人类健康、生活环境带来的严重危害,全球范围已相继立法规定了使用含铅电子焊料的最后期限,无铅封装,无铅焊料成为了近年来的研究热点问题。本文主要叙述了研究无铅焊料的驱动力,以及无铅焊料须满足的基本要求、常用无铅焊料的优缺点和改进方法,同时介绍了无铅化焊接由于焊料的差异和工艺参数的调整,给焊点可靠性带来的相关问题。     

无铅焊接技术在微电子封装工业中的应用综述

介绍了无铅焊接技术的现状以及国内外对Sn-Ag和Sn-Zn等二元无铅焊料的研究成果,以及无铅焊接的几种常见技术.     

Sn-Ag-Cu系无铅焊料的显微组织与性能

用无铅焊料取代现有的含铅焊料已经成为历史发展的必然趋势.Sn-Ag-Cu系合金具有优异的可靠性和可焊性,受到了电子工业界的广泛关注.阐述了近年来该系焊料合金的微观组织和性能的一些研究成果,并对该系无铅焊料的特性进行了比较.结果表明,低银焊料的组织和性能比高银焊料好,而且成本低,为确定综合性能最佳的该系焊料合金提供依据.     

自适应无铅焊料的开发与研究

可靠性是电子工业发展所面临的最大难题.随着对无铅焊料的深入研究,消除金属间化合物对焊点机械性能的不利影响,及解决由于印刷电路板与电子材料间的热膨胀系数不同所产生的、在热循环过程中出现的热疲劳现象,都是提高可靠性的途径.提出了开发自适应无铅焊料解决上述问题,阐述了制备自适应无铅焊料的可行性,并展望了此种焊料的良好应用前景.     

全国焊接标准化技术委员会无铅焊接材料工作组

全国焊接标准化技术委员会无铅焊接材料工作组（编号为SAC／EC55／WG1）于2008年7月由郴州金箭焊料有限公司负责召集并经国家标准化管理委员会批准成立。主要负责焊接用无铅焊料领域的国家标准制修订工作。     

微电子互连锡基无铅焊料的发展

对国内外无铅焊料发展情况进行了综述,详细分析了当前运用广泛的Sn-Ag,Sn-Cu和Sn-Ag-Cu无铅焊料的相组织、性能等,列举了商业应用中无铅焊料的使用情况,并阐述了无铅焊料的可靠性问题、发展要求以及发展趋势等.     

绿色无铅电子焊料的研究与应用进展

概述了关于无铅电子焊料全球范围的立法与研发计划、国内外无铅焊料的发展现状及所取得的研究成果,探讨了无铅焊料合金的专利问题,进行了无铅软钎焊技术可行性、经济性和可靠性分析,介绍了无铅焊料的应用情况,并展望了前景.     

稀土元素对无铅焊料性能的影响

随着公众环保意识的增强,含铅焊料的发展和应用受到了极大的限制,研制新型的、环境友好的无铅焊料来取代传统的锡铅焊料成为近年来研究的热点,而添加微量元素合金化以获得性能优异的无铅焊料尤其受到研究者的关注。本文系统地综述了添加微量稀土元素对无铅焊料物理化学性能、显微组织、力学性能、电迁移及锡晶须生长等的影响,并对稀土元素在无铅焊料中的应用及发展趋势进行了展望。     

焊料无铅化--不可回避的选择

随着欧盟《RoHS指令》执行日期的临近,电子产品的无铅化组装已经不可回避。尽管无铅产品在国内已经四处可见,然而,以SnAgCu三元合金为主流的无铅产品几乎全部依赖于进口。我国焊料产量大,产品链广,受欧盟指令的影响,焊料的使用将直接影响相关产品的出口。无铅焊接的全面导入需要解决很多问题,特别是无铅焊料的产业化。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.