直流偏压对脉冲激光烧蚀沉积非晶碳膜的影响

在不同的负直流衬底偏压下，用脉冲激光沉积法在单晶Si和K9玻璃衬底上沉积上水晶碳膜，用扫描电镜观察膜的表面形貌；用椭偏法测量沉积在K9玻璃上的厚茺和折射率；显微硬度相对于硅衬底测量；对沉积在硅衬底上的膜进行了Raman光谱分析，光谱表现为3个峰。在激光能量相同时，线宽随偏压不同而不同，膜的硬度随偏压不同而不同。     

45钢激光渗硼后的显微组织及相结构分析

用扫描电子显微镜和Ｘ射线衍射仪对４５钢激光渗硼层的显微组织和相结构进行了分析，结果表明４５钢激光渗硼后，渗硼区的显微组织：表层为胞晶组织，次表层为树枝晶组织，再往里为共晶组织。渗硼区组织的相组成为α－Ｆｅ、ＦｅＢ、Ｆｅ２Ｂ、Ｆｅ３（Ｃ·Ｂ）及Ｂ４Ｃ相等。不同显微组织中各相所占比例不同，因而导致各区显微硬度不同。     

NC toolpath generation for arbitrary pockets with Islands

This paper presents an efficient algorithm for generating cutter paths for the NC milling of arbitrary pockets with multiple islands. In this algorithm, the pocket border and island profiles are made up of concave or convex segments comprising linear and circular arc elements. For the generation of NC tool paths, the algorithm is divided into four stages, namely, profile pre-processing stage, offset calculation, determination of the termination condition, and determination of the path sequence. Compared with the other pocketing algorithms, the main aspect of this work is that the pocket border and island profiles are pre-processed in the first stage of the algorithm. Making use of contour bridges in the profile pre-processing stage, the island profiles are connected to the pocket border profile to form a closed path. This then simplifies the calculations in cutter offsets and eliminates the problem of nesting which occurs in some other pocketing algorithms.     

论光发射器件研究与发展方向

提出了半导体光发射器件发展的五大方向,即单纵模、高速率、大功率、可见光和光电子集成技术。指明了现阶段研究重点及今后研究方向和奋斗目标。     

ZL108镍基粉末激光表面合金化气孔与裂纹的研究

ZL10 8表面镍基粉末激光合金化的实验研究表明 :激光合金化层的显微组织由两部分组成 ,与基体金属交界处是垂直于熔合线生长的具有定向凝固特征的树枝状晶 ,合金化区是细小的等轴状晶。在树枝状晶相邻间的凹陷处和基体金属未熔化晶粒的界面上最有可能产生气泡核 ,熔池保护不良 ,合金粉末或粘接剂中残存水分 ,均是影响气泡生成的主要因素。对于合金层中的裂纹 ,主要是在熔池凝固末期 ,已凝固合金化层金属塑性不足并在残余拉应力作用下造成的低塑性脆化裂纹。     

激光快速成形过程熔池行为的实时观察研究

通过建立近距离连续拍摄系统实现了对激光快速成形过程中熔池行为的实时观察,并采用图像分割算法获得了熔池侧视形态,结合熔覆试样的定量金相法获得的熔池前视形态,对熔池进行了定量表征。结果发现,熔池的长度和宽度与光束直径相当,熔池自由表面呈圆弧形并向外凸起,最大熔深处熔池自由表面法向和激光束轴线之间存在夹角,表明熔池向激光束轴线方向倾斜,而熔池在液态存在时间较短,例如光束直径为4mm,光束扫描速度为5mm/s时,熔池在液态存在时间小于1秒。激光熔覆区的高速摄影实验结果发现,随金属粉末的射入,熔池的几何尺寸逐渐减小,熔池后沿不断抬高,最大熔深处熔池自由表面法向和激光束轴线之间的夹角由1度左右逐渐增大到25度左右,导致熔池中局部凝固条件发生改变,从而影响到局部熔覆层的微观组织。     

Characteristics of laser aided direct metal/material deposition process for tool steel

Laser aided direct metal/material deposition (DMD) process builds metallic parts layer-by-layer directly from the CAD representation. In general, the process uses powdered metal/materials fed into a melt-pool, creating fully dense parts. Success of this technology in the die and tool industry depends on the parts quality to be achieved. To obtain designed geometric dimensions and material properties, delicate control of the parameters such as laser power, spot diameter, traverse speed and powder mass flow rate is critical. In this paper, the dimensional and material characteristics of directed deposited H13 tool steel by CO₂ laser are investigated for the DMD process with a feedback height control system. The relationships between DMD process variables and the product characteristics are analyzed using statistical techniques. The performance of the DMD process is examined with the material characteristics of hardness, porosity, microstructure, and composition.     

Thermal parameters identification of micrometric layers of microelectronic devices by thermoreflectance microscopy

The objective of this paper is the determination of the thermal properties of micrometric layers of electronic devices using a thermoreflectance probe. Unlike classical thermoreflectance methods, the main point of the method presented in this paper is to be able to quantify the heating energy (by Joule effect) and the effective temperature response (by calibration). It is then possible to estimate the thermal conductivity (in W m⁻¹ K⁻¹) instead of the thermal diffusivity (in m² s⁻¹). A semi-analytical thermal 3D-periodic model then enables to identify a few thermal properties of the layers of the device, and in particular the thermal conductivity of the passivation layer. This methodology has been applied to the study of an industrial device containing interconnect test structures made of copper lines on a silicon wafer with a few micrometers BCB (BenzoCycloButene) polymer passivation layer. The BCB thermal conductivity and the metal heat capacity are obtained using this method.     

EM-5009B激光图形发生器光栏的修正方法

激光图形发生器是半导体掩膜制版的主要设备之一,它具有精度高、结构复杂、操作简单和生产效率高等特点,但是,其光栏精度对加工的版图精度有很大的影响.文章根据光栏的结构原理和实际应用,详细阐述了EM-5009B激光图形发生器光栏的修正方法.     

Cost-tolerance relationships for non-traditional machining processes

In recent years, non-traditional machining processes have been growing in popularity and their applications have continued to increase. However, very limited research work has been carried out to investigate their economic implications on tolerance allocation. This paper reports on cost-tolerance relationships for non-traditional processes, namely, electrical discharge wire machining and laser beam machining. Medium carbon steel plates are machined using the two processes to obtain cost-tolerance data which are fitted to various mathematical models. A third-degree polynomial function has been found which gives the most representative fit to the data obtained. An example is presented to illustrate the application and to compare the cost implication of the two machining processes.