Comparing the Impacts of the Capillary and the Molded Underfill Process on the Reliability of the Flip-Chip BGA

In the assembly process for the conventional capillary underfill (CUF) flip-chip ball grid array (FCBGA) packaging the underfill dispensing creates bottleneck. The material property of the underfill, the dispensing pattern and the curing profile all have a significant impact on the flip-chip packaging reliability. Due to the demand for high performance in the CPU, graphics and communication market, the large die size with more integrated functions using the low-K chip must meet the reliability criteria and the high thermal dissipation. In addition, the coplanarity of the flip-chip package has become a major challenge for large die packaging. This work investigates the impact of the CUF and the novel molded underfill (MUF) processes on solder bumps, low-K chip and solder ball stress, packaging coplanarity and reliability. Compared to the conventional CUF FCBGA, the proposed MUF FCBGA packaging provides superior solder bump protection, packaging coplanarity and reliability. This strong solder bump protection and high packaging reliability is due to the low coefficient of thermal expansion and high modulus of the molding compound. According to the simulation results, the maximum stress of the solder bumps, chip and packaging coplanarity of the MUF FCBGA shows a remarkable improvement over the CUF FCBGA, by 58.3%, 8.4%, and 41.8% (66 $mu {rm m}$), respectively. The results of the present study indicates that the MUF packaging is adequate for large die sizes and large packaging sizes, especially for the low-K chip and all kinds of solder bump compositions such as eutectic tin-lead, high lead, and lead free bumps.      

澳洲插头产品的法规要求及标准解析

介绍了澳大利亚插头产品的法规要求及插头的型式、尺寸、参数和测试要点,分析了插头的电流额定值和配线之间的关系,强调了插销绝缘套的要求。对重要的试验项目,如弯曲试验、插销绝缘套的耐磨试验、温升试验、高温压力试验进行了说明。     

宇航元器件应用验证指标体系构建方法研究

通过分析宇航元器件应用验证指标体系的特点,建立了一套面向宇航元器件应用验证的指标体系构建方法,该方法分别应用专家遴选系统、头脑风暴法和德尔菲法,解决了宇航元器件应用验证指标体系构建中的专家遴选、因素识别和指标体系构建问题。最后,应用该方法建立了宇航元器件应用验证综合评价指标体系基本结构。     

On the Complexity of the Verification of the Costas Property

In this paper, we show that in order to ascertain whether a permutation has the Costas property, only a restricted subset among the totality of pairs of entries in the same row of the difference triangle needs to be checked, and we explicitly describe such a subset. This represents a further refinement on the definition of a Costas permutation. This observation can be used to speed up algorithms that exhaustively search for Costas permutations. Asymptotically, the savings approaches 43% for large orders when compared with the previous standard efficient method.     

the Good,the Bad and the Ugly

《Sat Magazine》,2012年11月刊对于当红的有效载荷商业搭载(Hosted Payload)业务,由十余家知名航天企业组成的"有效载荷搭载联盟"(HPA)显然颇具发言权。在最新一期Sat Magazine杂志上,HPA的代表撰文细数了有效载荷搭载业务最近面临的"善、恶、丑":"善"——美国总统奥巴马在向国会提交的2013财年预算申请中为与有效载荷     

On the Transparency of the Stroma in the Mammalian Cornea

This paper discusses the transparency of the normal mammalian cornea with particular reference to the scattering of light from the fibril structure in the stroma. It is shown theoretically that Maurice's fibril-lattice model would allow about 50? rms isotropic fibril displacements from the ideal lattice positions to produce one percent scatter. This theoretically acceptable disorder seems to be in reasonable agreement with electron micrographic investigations. It is also shown that the scattered power is inversely proportional to the fifth power of the wavelength for this scattering model. Other scattering models are also discussed. These exhibit different wavelength dependence (1/?3, 1/?). Unfortunately no scatter versus wavelength measurements seem to have been reported in the literature.     

基于矢势标势与电场的量级分析

根据矢势和标势满足的波动方程,分析了电磁波传播时电场的纵向分量与横向分量之比值,用量级分析的疗法证明了其纵向分量可以忽略。     

冷藏库的微电脑控制操作研究

在介绍微电脑控制小型氟利昂冷库功能的基础上 ,对具体操作方法作了研究 ,在实际技术应用上有一定的意义。     

下一代网络的演进--从SoftSwitch到IMS

文章介绍了国际标准组织中下一代网络（NGN）体系结构的最新研究进展,探讨了下一代网络可能的演进路线：从软交换到因特网协议（IP）多媒体子系统（IMS）,即网络走向融合的道路。文章着重介绍了IMS的结构和功能实体。     

氧化膜和玻璃浸润性测量方法的探讨

通过计算和实验首次探讨了异材浸润性的两个评价指标浸润角与铺展面积之间的关系，弄清了滴座实验方法与铺展实验方法的适用范围，在此基础上提出测量浸润角０Ｍ４５”的氧化膜与玻璃之间的浸润性时应采用铺展实验方法。     

基于PSASP程序的励磁系统PID控制的仿真与验证

励磁系统的PID参数对发电机组和电网稳定的可靠性和动态品质具有重要的作用。检验励磁系统PID参数准确性的方法主要是进行发电机空载阶跃响应试验。本文采用中国电力科学研究院研制的电力系统综合仿真程序PSASP对沧东电厂4号机励磁系统进行了5%机端电压阶跃仿真试验,然后根据仿真结果进行了现场试验,结果表明仿真结果对现场试验具有重要的指导意义,不仅节省了现场调试的时间,而且进一步提高了现场试验的安全性。     

以质为根,夯实企业生存和发展的基石

该文以直接论述的方式,指出国家对质量工作的重视,就当前元器件和整机企业中存在的质量问题进行深入剖析,从宏观和微观层面对企业生存和发展的关键提出切实可行的建议和对策。     

沉铜背光不良问题的改善

主要介绍了一直困扰印制电路沉铜生产工艺过程中频繁出现的背光不良问题的追踪改善情况,通过深入研究和探索,找到了问题的产生根源,制定了有效的改善措施,最终杜绝了背光不良问题的发生,稳定了沉铜工序的生产。     

表面态对GaN HEMT电流崩塌效应影响的研究

针对GaN HEMT电流崩塌物理效应,测试了各种条件下器件I-V特性。发现在栅脉冲条件下器件最大漏输出电流减小了23.8%,且随着栅脉冲宽度减小或周期增大而下降,并且获得了其输出电流与脉冲宽度W和周期T的定量关系;在漏脉冲测试条件下,器件输出电流有所增大,并随着脉冲宽度减小而缓慢增大。实验结果,可用器件栅漏之间表面态充放电的原理来解释所观察到的测试现象和电流崩塌物理。     

耦合相互作用对光纤中类明孤子传输特性的影响

本文采用变分法，导出了双全同耦合光纤中类明孤子参数的演化方程组，在此基础上讨论了类明孤子在耦合光纤中的传输特性，分析了耦合相互作用对类明孤子参数的影响。     

唯产业是根唯亮点是本--回眸"中国信息安全战略与趋势"高层研讨会4年之履

引言四季轮回,大自然总是不偏不倚地遵循着这一守则,使人类感受着异样的景观和不断的期待。《信息安全与通信保密》杂志社感受自然恩泽的同时,也期盼着能为信息安全产业界带来四季如春的新意与生机。 二零零一年始办的“中国信息安全发展趋势与战略”高层研讨会已经走过了4个年头,承蒙主管领导、专家学者及广大安全企业和行业用户之关照与呵护,4年后的今天依然能够站在产业的前沿,架设各方之间的桥梁,领略产业风景。此心情不敢独有,现就产业发展之线,连贯研讨会4年的历程,与各方人士共飨。     

Analyzing the stability of the FDTD technique by combining the vonNeumann method with the Routh-Hurwitz criterion

This paper addresses the problem of stability analysis of finite-difference time-domain (FDTD) approximations for Maxwell's equations. The combination of the von Neumann method with the Routh-Hurwitz criterion is proposed as an algebraic procedure for obtaining analytical closed-form stability expressions. This technique is applied to the problem of determining the stability conditions of an extension of the FDTD method to incorporate dispersive media previously reported in the literature. Both Debye and Lorentz dispersive media are considered. It is shown that, for the former case, the stability limit of the conventional FDTD method is preserved. However, for the latter case, a more restrictive stability limit is obtained. To overcome this drawback, a new scheme is presented, which allows the stability limit of the conventional FDTD method to be maintained     

红外探测器内部颗粒物对图像的影响

在高灵敏度的红外光学系统中,来自系统内部的热辐射是影响系统探测性能的重要因素之一。污染颗粒物通常是杂散辐射的主要来源,除了光学元件的表面污染,探测器内部也会存在污染颗粒物。文中主要研究探测器内部颗粒物对焦平面光场分布产生的影响。根据红外辐射及散射原理建立了相应的理论模型,对探测器内部不同温度、不同位置的颗粒物在焦平面上形成的光场分布进行了仿真计算和对比分析,并进行了实验验证。结果表明,探测器内部如有颗粒杂质,在一定的使用环境下,可在探测器焦面上产生黑斑、白斑、黑点白斑等异常现象,而这些异常光场分布会对场景中的红外目标物产生干扰,造成误判,从而影响对目标的准确识别。因此应采用措施以保证探测器内部的洁净度,防止颗粒物的产生。     

视距传播中地面起伏对传播中值衰减的影响

电波在以视距传播方式进行传播时,在低空大气层中还要受到地面的影响。文中具体分析了视距传播下几种传播模型中地面起伏对电波传播衰减中值的影响,并进行了相应的计算,最后给出相应地面起伏度与传播衰减中值之间的关系。     

基于监控系统的应用,探索电源集中化维护模式的变革

本文旨在通过对移动通信电源维护和管理工作的现状深入分析,提出以机房、基站监控系统为基础的电源维护综合管理和支撑平台的建设与应用方案,并结合综合电子化运维管理平台(IMEP)的应用,对集中化的电源维护管理模式的建设和运作进行探索.