电子仪器失效(故障)分析

本文结合具体实例着重介绍了电子测量仪器失效分析中最通用的方法--根据故障部位分析故障产生的原因.为广泛开展失效分析活动,提高电子测量仪器可靠性水平提供重要参考.     

浅谈电子设备中软件可靠性与稳定性的检验

本文结合某电子设备中一个软件故障的发现、验证和排除过程,就如何对电子设备中软件可靠性与稳定性的检验进行了一定的探讨。     

Ball grid array reliability assessment for aerospace applications

Reliability of ball grid arrays (BGAs) was evaluated with special emphasis on space applications. This work was performed as part of a consortium led by the Jet Propulsion Laboratory (JPL) to help build the infrastructure necessary for implementing this technology. Nearly 200 test vehicles, each with four package types, were assembled and tested using an experiment design. The most critical variables incorporated in this experiment were package type, board material, surface finish, solder volume, and environmental condition. The packages used for this experiment were commercially available packages with over 250 I/Os including both plastic and ceramic BGA packages.The test vehicles were subjected to thermal and dynamic environments representative of aerospace applications. Two different thermal cycling conditions were used, the JPL cycle ranged from −30°C to 100°C and the Boeing cycle ranged from −55°C to 125°C. The test vehicles were monitored continuously to detect electrical failure and their failure mechanisms were characterized. They were removed periodically for optical inspection, scanning electron microscopy (SEM) evaluation, and cross-sectioning for crack propagation mapping. Data collected from both facilities were analyzed and fitted to distributions using the Weibull distribution and Coffin–Manson relationships for failure projection. This paper will describe experiment results as well as those analyses.     

Thermal resistance degradation of surface mounted power devices during thermal cycling

Backside scanning acoustic tomography (SCAT) images have been correlated to alloy morphology (cross-section) and composition data (stoichiometry) to model the Θ_JC degradation for surface mounted device packaged power ICs as a function of the temperature cycling range. We find that an appropriate setting of the die attach process can suppress needle-shaped Cu₃Sn in favor of roughly spheroid Cu₆Sn₅. We derived, from the degradation of the Θ_JC during thermal cycling stress tests with different temperature swings, an acceleration factor with the use of the Coffin–Manson law. The fit parameter q in this formula is 9.3 for the new improved setting of the die attach process when the high SO power (HSOP) package is used. The moisture sensitivity level has no significant influence. Finally, a maximum Θ_JC degradation of 0.33 K/W based on the normal distribution approach results in a minimum lifetime of 12 years. When a customer requires a maximum Θ_JC of 2.0 K/W at the end of life, 50 years can be guaranteed.     

波峰焊接设备的发展动态

介绍了目前在美国市场上波峰焊接设备的发展动态、主要涉及：焊剂的添加、预热处理、焊料波峰、传输带和惰性气体的保护等内容。另外还介绍了新近的一些波峰焊接设备的情况,以供有关技术人员参考。     

基于高迁移率微晶硅的薄膜晶体管

近年来,微晶硅(μc-Si:H)被认为是一种制作 TFT 的有前景的材料.采用PECVD法,在低于200℃时制作了微晶硅TFTs,其制作条件类似于非晶态 TFTs.微晶硅 TFTs 器件的迁移率超过了 30 cm2/Vs,而阈值电压是 2.5 V.在长沟道器件(50～200 μm)中观测到了这种高迁移率.但对于短沟道器件(2 μm),迁移率就降低到了7 cm2/Vs.此外,该 TFTs 的阈值电压随着沟道长度的减少而增大.文章采用了一种简单模型解释了迁移率、阈值电压随着沟道长度的缩短而分别减少、增加的原因在于源漏接触电阻的影响.     

星载多光谱CCD相机电子电路研制

研制的多光谱CCD相机采用线阵CCD推扫方式成像，具有5个成像谱段，每个谱段的敏感器阵列由3片CCD拼接而成，给出了相机电子电路部分的总体设计方案。采用各片CCD信号串行读出的方法形成两路视频信号，简化了星上数据处理电路。设计了直流差分耦合电路，使信号直流漂移降到20mV以下，采用无源滤波器抑制信号噪声，在保证奈奎斯特频率衰减小于0.5dB的前提下，使信号随机噪声降到了2mV以下。     

Calculation of absolute electron-impact ionization cross-sections of dimers and trimers

We report calculations of the electron-impact ionization cross-sections of selected dimers (homonuclear diatomic molecules) and trimers (homonuclear triatomic molecules) using a method which relies only on macroscopic quantities in conjunction with a “defect concept”. The empirically determined defect describes the deviation of the cluster (dimer, trimer) cross-sections from a simple linear dependence on the cluster size. We compare the calculated cross-sections to experimental data for the dimers S₂ and F₂ and the trimer O₃ and we present predictions for the ionization cross-sections of Br₂, I₂, C₂ and C₃ for which no experimental data are available. Lastly, we extend the method to the calculation of ionization cross-sections for the fullerenes C₆₀ and C₇₀. Received 6 December 1999 and Received in final form 10 April 2000     

亚洲印制电路板业的现状与发展

近年来，电子工业技术的飞跃进步，促进了亚洲印制电路板业的巨大发展，当前亚洲已成为世界最大的印制电路板生产地区。文章综述了亚洲（特别是日本、中国台湾地区、韩国、新加坡、马来西亚）的印制电路板业在生产、技术、市场等方面的现状与发展。     

战场情报侦察系统的现状前瞻及发展建议

本文介绍当前国外战场情报侦察系统的发展近况。文中对几种典型的战场侦察系统进行了评论。最后作者就发展我国战场情报侦察系统提出了几点建议