Effect of Free‐Stream Turbulence on the Flow Structure near a Wedge and the Windward Side of an Airfoil

The flow structure behind wire grids is studied for flows with a low subsonic velocity, and the effect of grids on the boundarylayer flow structure is considered. It is shown that the meanvelocity inhomogeneity induced by the grid does not disappear until a distance of 925 calibers downstream of the grid is reached. Liquidcrystal thermography combined with hotwire measurements made it possible to find the source of steady largescale streamwise vortex structures in the boundary layer on a wedge and on an airfoil and to determine the parameters of these structures.     

量子线/铁基超导隧道结中隧道谱的研究

考虑铁基超导中能带间的相互作用和界面对每一个能带的散射作用, 利用推广的Blonder-Tinkham-Klapwijk模型, 并通过求解Bogoliubov-de Gennes 方程研究了具有不同类型双能隙系统的量子线/铁基超导隧道结中准粒子的输运系数和隧道谱. 研究表明: 1)在弹道极限时, 随着带间相互作用的增大, s_± 波隧道谱中零偏压附近的平台演变成电导峰; s₊₊ 波的平台演变成凹陷; p波的零偏压电导峰被压低. 2)界面对两个能带的散射作用不为零时, 随着带间相互作用的增大, s_± 波和s₊₊ 波两能隙处的峰值将降低, 而两峰间的凹陷值将变大; p波的零偏压电导峰被压低, 非零偏压电导增大. 3)界面对每个能带的散射, 可使其产生的电导峰变得更加尖锐, 但可压低和抹平另一个带产生的电导峰值. 这些结果对于澄清铁基超导体的能隙结构和区别不同类型铁基超导体有所帮助.     

应用于裸芯片去污的气相清洗技术

军用和民用微型电子产品的MCM、HIC等复杂混合电路正在越来越多地采用裸芯片,然而,裸芯片由于尺寸小、电路密集、焊盘间距小等原因,在进行组装的过程中一旦有微量的污染物出现,就会对裸芯片的应用造成较大影响。气相清洗通过清洗溶剂蒸汽在组件表面冷凝,形成液体滴下带走污染物,避免了传统的通过机械力、超声振动等清洗方式对裸芯片造成的不可修复的损伤。对限幅二极管砷化镓裸芯片、硅基裸芯片进行气相清洗,有效除去裸芯片表面的污染物,具有无损高效的特点。     

Ultra-fine pitch palladium-coated copper wire bonding: Effect of bonding parameters

Copper (Cu) wire bonding has become a mainstream IC assembly solution due to its significant cost savings over gold wire. However, concerns on corrosion susceptibility and package reliability have driven the industry to develop alternative materials. In recent years, palladium-coated copper (PdCu) wire has become widely used as it is believed to improve reliability. In this paper, we experimented with 0.6 ml PdCu and bare Cu wires. Palladium distribution and grain structure of the PdCu Free Air Ball (FAB) were investigated. It was observed that Electronic Flame Off (EFO) current and the cover gas type have a significant effect on palladium distribution in the FAB. The FAB hardness was measured and correlated to palladium distribution and grain structure. First bond process responses were characterized. The impact of palladium on wire bondability and wire bond intermetallic using a high temperature storage test was studied.     

Copper wire interconnect reliability evaluation using in-situ High Temperature Storage Life (HTSL) tests

This paper describes the use of in-situ High Temperature Storage Life (HTSL) tests based on a four point resistance method to evaluate Cu wire interconnect reliability. Although the same set up was used in the past to monitor Au–Al ball bond degradation, a different approach was needed for this system. Using conventional statistical methods of failure probability distributions and a fixed failure criterion were found to be unsuitable in this case. Besides this, tests usually take very long until a sufficient percentage of the population have failed according to that criterion. A simple physical model was used to electrically quantify ball bond degradation due to the prevailing failure mechanism in a substantially smaller amount of test time. The method enabled the determination of activation energies for a number of moulding compounds and is extremely useful for a fast screening of such materials regarding their suitability for Cu wire.     

铜线键合Cu/Al界面金属间化合物微结构研究

由于铜线具有较高的热导率、卓越的电学性能以及较低的成本,被普遍认为将逐渐代替传统的金线而在IC封装的键合工艺中得到广泛的应用。铜线键合工艺中Cu/Al界面金属间化合物(IMC)与金线键合的Au/Al IMC生长情况有很大差别,本文针对球焊键合中键合点的Cu/Al界面,将金属间化合物生长理论与分析手段相结合,研究了Cu/Al界面IMC的生长行为及其微结构。文中采用SEM测试方法,观察了IMC的形貌特点,测量并得到了IMC厚度平方正比于热处理时间的关系,计算得到了生长速率和活化能数值,并采用TEM,EDS等测试手段,进一步研究了IMC界面的微结构、成分分布及其金相结构。     

汽车线束图纸的自动识别方法

结合我国汽车行业的生产现状,研究、讨论了一种计算机自动识别汽车线柬图纸的方法。该方法通过计算机软件仿真试验,在符合某一预先设定好的识图规则的情况下,根据编制好的程序对图纸中线束进行判断,筛选出需要的线束和线束段,将其按类合并,最终达到自动完成线束长度和线束分类识别的目的。这种新的识别方法较传统的人工读图,分段计算,相加求和的方法有了很大的创新,极大地提高了我国汽车行业的生产效率,减少了人员操作的错误率,为企业生产带来直接利益。     

碳化硅金刚线切割表面粗糙度的研究

碳化硅是新兴的第三代半导体材料。用固定磨料金刚线切割机对其进行切割加工,分析了加工过程的各项参数对晶片表面粗糙度的影响,为优化碳化硅金刚线切割过程提出依据。     

绕制精密螺旋线的系统技术

在螺旋线型慢波电路行波管中,精密螺旋线是重要的组成部分,由于精密螺旋线的绕制要求高（包括螺距精度、螺旋线形状）,行业研究机构、制造与使用单位、检测部门等在不断地进行系统研究和工艺试验。对绕制精密螺旋线系统的主要结构、控制方法进行了叙述,经实际应用证明了这种方法的可行性。     

局部增强压焊块铝层厚度的工艺方法

针对目前铜线封装对芯片压焊块的铝层厚度要求较高的问题,通过改进芯片制造工艺流程,对芯片内部压焊块的铝层进行单独地加厚。以便同时满足芯片封装厂采用铜线打线和芯片制造厂金属刻蚀工艺难易的要求。做法为,在钝化层刻蚀完成后,再生长一层足够厚的金属层,进行钝化层反版的光刻以及湿法刻蚀,只保留下压焊块区域的金属层,此时压焊块区域就...