两类有脱层损伤层合圆柱壳的半解析法研究

为了研究层合壳脱层,本文首先建立了柱坐标系下Hamilton 正则方程的8 节点等参元列式;然后分别采用了"先分后合" 模型和"弱粘接" 模型对开口壳的脱层损伤进行了模拟;通过利用层间的力学关系建立了整个壳的求解方程;最后分别从粘接完好和脱层两类情况对开口壳进行研究,并计算脱层前缘裂纹扩展的能量释放率. 数值实例的分析结果表明环向脱层受外载荷影响大于轴向脱层外载荷影响,脱层深度对两类脱层模型影响较大.     

Introduction of plastic encapsulated devices in systems operating under severe temperature conditions

In this paper, we describe the evolution of the selection, qualification and implementation methods used to validate the introduction of plastic SMD's into electrical equipment submitted to extreme environmental conditions:The first introduction phase was addressing equipment operating up to 125°C. The selection process was intentionally kept to minimum with emphasis on qualification through mission profile at equipment level. The results in terms of cost, performance, reliability and field feedback experience were extremely positive.The second phase was initiated for operating conditions as high as 175 °C environmental temperature. The selection process of plastic components operating at such extreme conditions, includes a full qualification through mission profile at component level. The experiments using vehicle test boards led to numerous electrical failures originated by a unique failure mechanism: delamination.In consequence, the selection process is being reviewed: a short-test for capability will be run with emphasis on initial behavior versus delamination.Expected benefits are

reduction of overall qualification costs through elimination of complete qualification with mission profile at component level.

faster availability to designers.

     

季铵盐功能化的钛硅分子筛催化丙烯氧化酯化合成碳酸丙烯酯

将有机卤素季铵盐以硅烷化键合方式嫁接到钛硅分子筛上,制备了兼备催化氧化烯烃合成环氧化物和环氧化物碳酸酯化反应的新型双功能催化剂,考察了其在丙烯、过氧化氢和二氧化碳一步合成碳酸丙烯酯的催化性能.研究表明,具有大外表面积的层剥离的钛硅分子筛是一种嫁接季铵盐合适的载体,丙基三丁基卤化铵是酯化催化性能优良的功能化基团,两者的偶合使一步法催化丙烯环氧化酯化合成碳酸丙烯酯的收率达48%.该催化剂具有较好的稳定性和重复使用性能.     

Reversible Electrochemically Triggered Delamination Blistering of Hydrogel Films on Micropatterned Electrodes

Stimuli responsive elastic instabilities provide opportunities for controlling the structures and properties of polymer surfaces, offering a range of potential applications. Here, a surface actuator based on a temperature and electrically responsive poly(N‐isopropyl acrylamide‐co‐sodium acrylate) hydrogel that undergoes a two‐step delamination and buckling instability triggered using micropatterned electrodes is described. The electrically actuated structures entail large out‐of‐plane displacements that take place on time‐scales of less than 1 s, in response to modest triggering voltages (?3–6 V). Alongside these experimental observations, finite element simulations are conducted to better understand the two‐step nature of the instability. In the first step, hydrogel films undergo delamination and formation of blisters, facilitated by electrochemical reduction of the thiol groups anchoring the film to the electrodes. Subsequently, at larger reducing potentials, the electrolytic current is sufficient to nucleate a gas bubble between the electrode and the gel, causing the delaminated region to adopt a straight‐sided blister shape. Finally, thermally induced deswelling of the gel allows the film to be returned to its flat state and readhered to the electrode, thereby allowing for repeated actuation.     

Solvent‐Dependent Delamination,Restacking, and Ferroelectric Behavior in a New Charge‐Separated Layered Compound: [NH4][Ag3(C9H5NO4S)2(C13H14N2)2]⋅8 H2O

A new anionic coordination polymer, [NH₄][Ag₃(C₉H₅NO₄S)₂(C₁₃H₁₄N₂)₂] ⋅ 8 H₂O, with a two‐dimensional structure, has been synthesized by a reaction between silver nitrate, 8‐hydroxyquinoline‐5‐sulfonic acid (HQS), and 4,4′‐trimethylene dipyridine (TMDP). The compound stabilizes in a noncentrosymmetric space group, and the lattice water molecules and the charge‐compensating [NH₄]⁺ group occupy the inter‐lamellar spaces. The lattice water molecules can be fully removed and reinserted, which is accompanied by a crystalline–amorphous–crystalline transformation. This transformation resembles the collapse/delamination and restacking of the layers. To the best of our knowledge, this is the first observation of delamination and restacking in an inorganic coordination polymer that contains silver. The presence of a natural dipole (the anionic framework and cationic ammonium ions) along with the noncentrosymmetric space group gives rise to the room‐temperature ferroelectric behavior of the compound. The ferroelectric behavior is also water‐dependent and exhibits a ferroelectric–paraelectric transformation. The temperature‐dependent dielectric measurements indicate that the ferroelectric/ paraelectric transformation occurs at 320 K. This transformation has also been investigated by using in‐situ IR spectroscopy and PXRD studies. The second‐harmonic generation (SHG) study indicated values that are comparable to some of the known SHG solids, such as potassium dihydrogen phosphate (KDP) and urea.     

Micro-punching process based on spallation delamination induced by laser driven-flyer

In this article, we proposed a micro-punching process for microstructure on films based on laser driven-flyer induced spallation delamination phenomenon at the interface between a film and its substrate. To validate such a micro-punching process, a series of experiments were carried out for fabrication of microstructures on Au films coated on K9 glass substrates and polyimide substrate. Results show that through such a punching process, the microstructure on Au films can be fabricated efficiently and the spatial resolution is able to reach micron level. Moreover, we found that this method was more suitable for films coated on soft substrates rather than that coated on brittle substrates due to the additional destruction of the brittle substrate. This micro-punching process has a wide range of potential application in microfluidic devices, biodevices and other MEMS devices.     

HDI板爆板缺陷分析方法浅谈

爆板是PCB制造企业中非常常见也非常严重的一种缺陷,随着后道无铅焊接制程的导入,该问题显得尤为突出,急待解决。作者根据实际工作经验,总结出了对HDI板爆板缺陷进行分析的4种不同分析方法:垂直金相切片分析法,平磨分析法,剥离分析法和Tg/T260测试分析法。通过对每种分析方法的详细介绍,总结出了其各自的优缺点和适用的场合。同时,通过对这些方法的介绍,为工程师在以后的工作中如何运用合适的方法对HDI板爆板缺陷进行全面有效的分析提供了参考。     

Nonlinear progressive damage model for composite laminates used for low-velocity impact

In order to effectively describe the progressively intralaminar and interlam- inar damage for composite laminates, a three dimensional progressive damage model for composite laminates to be used for low-velocity impact is presented. Being applied to three-dimensional （3D） solid elements and cohesive elements, the nonlinear damage model can be used to analyze the dynamic performance of composite structure and its failure be- havior. For the intralaminar damage, as a function of the energy release rate, the damage model in an exponential function can describe progressive development of the damage. For the interlaminar damage, the damage evolution is described by the framework of the continuum mechanics through cohesive elements. Coding the user subroutine VUMAT of the finite element software ABAQUS/Explicit, the model is applied to an example, i.e., carbon fiber reinforced epoxy composite laminates under low-velocity impact. It is shown that the prediction of damage and deformation agrees well with the experimental results.     

HDI爆板问题分析及改善

2003年RoHS指令的提出使得电子产品无铅化成为必然发展趋势,无铅焊接将逐渐取代锡铅合金焊接。与有铅焊接相比,无铅焊接温度高,焊接时间长,所以无铅焊接对PCB,尤其对具有盲埋孔结构的HDI板的耐热性是一个重大考验。文章先根据我公司出现的HDI爆板现象进行理论分析,再从材料和塞孔工艺两方面验证不同结构HDI板产生爆板的条件,寻求改善爆板的工艺途径和HDI材料选型。     

QFN封装分层失效与湿-热仿真分析

采用湿度敏感度评价试验及湿-热仿真方法,分析了温湿度对于QFN封装分层失效的影响.通过C-SAM和SEM等观察发现,QFN存在多种分层形式,分层大多发生在封装内部材料的界面上,包括封装塑封材料和芯片之间的界面、塑封材料和框架之间的界面等.此外,在封装断面研磨的SEM图像上发现芯片粘结剂内部有空洞出现.利用有限元数值模拟的方法,对QFN封装的内部湿气扩散、回流过程中的热应力分布等进行了模拟,分析QFN分层失效的形成原因.结果表明,由于塑封器件材料、芯片、框架间CTE失配,器件在高温状态湿气扩散形成高气压条件下易产生分层.最后提出了改善QFN分层失效的措施.