HDI板RCC料层孔壁爆裂原因分析和改善

分析了HDI板生产中RCC料层出现孔壁爆裂的原因,同时给出了改善方法,并对此原因和改善方法进行了验证。     

观察裂纹路径及组织演变的SEM样品制备方法研究

本试验利用SEM和电阻炉研究一种SEM样品的制备方法,用于观察裂纹路径,并分析断裂后的显微组织变化。结果表明:通过浸镀焊锡,能够在不同断裂方式形成的裂纹轨迹上形成一条明显的"纯锡带",呈现出裂纹路径。同时该方法能够观察分析拉伸、冲击、断裂韧性及疲劳断裂等过程中产生的二次裂纹路径及断裂表层下的组织演变。     

对2024铝合金疲劳裂纹扩展寿命进行预测

通过二维弹塑性有限元计算得到Ⅰ型静态裂纹在常幅疲劳载荷下裂纹尖端塑性应变能,进而获得裂纹尖端塑性应变能和应力强度因子幅值的非线性关系;根据能量平衡概念,建立了裂纹扩展速率与裂纹尖端塑性应变能的关系。由此得到一种基于裂纹尖端塑性应变能的疲劳裂纹扩展寿命预测模型,利用该模型预测了中心裂纹平板的疲劳裂纹扩展寿命,预测结果与试验值吻合得很好。     

Strain‐Visualization with Ultrasensitive Nanoscale Crack‐Based Sensor Assembled with Hierarchical Thermochromic Membrane

As eidetic signal recognition has become important, displaying mechanical signals visually has imposed huge demands for simple readability and without complex signal processing. Such visualization of mechanical signals is used in delicate urgent medical or safety‐related industries. Accordingly, chromic materials are considered to facilitate visualization with multiple colors and simple process. However, the response and recovery time is very long, such that rapid regular signals are unable to be detected, i.e., physiological signals, such as respiration. Here, the simple visualization of low strain ≈2%, with ultrasensitive crack‐based strain sensors with a hierarchical thermochromic layer is suggested. The sensor shows a gradient color change from red to white color in each strain, which is attributed to the hierarchical property, and the thermal response (recovery) time is dramatically minimized within 0.6 s from 45 to 37 °C, as the hierarchical membrane is inspired by termite mounds for efficient thermal management. The fast recovery property can be taken advantage of in medical fields, such as monitoring regular respiration, and the color changes can be delicately monitored with high accuracy by software on a mobile phone.     

过渡合金层对激光多层送丝堆焊层组织性能的影响

采用灰铁基体材料,住小预热情况下通过增加Ni Re过渡合金熔覆层,再选用专用高硬度的合金焊丝进行激光送丝堆焊试验;分析堆焊过程物相变化,探索过渡合金对高硬度厚层堆焊裂纹倾向的影响规律,寻找高硬度厚层堆焊情况下防止裂纹产生的工艺方法。堆焊采用自制专用自动送丝机构,用Thermoatl-SCINTAGX’TRAX射线衍射仪和Thermo Noran VANTAGE-ESI能谱分析堆焊层物相组成。     

一种基于GPU的大规模地形绘制算法

利用Geometry Clipmap算法的基本思想,对原算法进行简化与改进。在预处理阶段,对地形数据的存储方式进行简化,并采用Clipmap结构进行组织和管理;在绘制阶段,重点针对不同分辨率层次之间的裂缝问题进行分析和处理,提出了一种引入过渡带的方法有效消除了裂缝。实验表明,该方法有效提高渲染速率,并充分发挥GPU的优势,实现了大规模地形数据的实时可视化。     

彩虹表在密码破解中的应用

密码作为一门科学,有着悠久的历史,在人类社会的发展过程中起到了至关重要的作用,如今的信息时代,密码应用更加广泛。在电子证据取证过程中就常遇到重要文档资料设置密码的情况,如办公软件Word、WPS形成的加密文档,以及Windows操作系统密码等。通过对加密文档或操作系统密码生成和存储方式的研究,在实践中利用3次换算的彩虹表破解这些密码具有方便快捷的优点,可以更好地协助电子证据取证工作。     

Cracking energy estimation of ultra low-k package using novel prediction approach combined with global-local modeling technique

Interfacial crack/delamination, due to the presence of dissimilar material systems, is one of the major concerns of thermo-mechanical reliability for the development of next node technology in integrated circuits (IC) devices. The cracking energy results from many back end of line (BEOL) and packaging processes at various temperature differences is prone to drive the crack advance. To investigate the sensitivity of crack propagation in low-k dielectric materials, a robust estimation of J-integral approach combined with a rectangular path of integral contour is performed using finite element analysis (FEA). By means of the verification of 4-point bending test (4-PBT), excellent agreements are obtained as compared with the experimental data. Moreover, a multiscale modeling technique is proposed to resolve the difficulty of model construction as from bridge device level to packaging level. The sub-modeling procedures developed specifically for the impact prediction of interfacial crack in complicated Cu/low-k interconnects. The analytic results indicate the foregoing methodology is valuable to forecast the physical behavior and reliability of advanced IC devices in the nano scaled size. On the basis of the presented results in this research, an approximated criterion for determining the dimensions of sub-model is suggested and demonstrated as well.     

高温合金/不锈钢异种材料T型接头激光穿透焊工艺研究

针对飞行器发动机水冷壁结构,进行了GH3128/06Cr19Ni10异种材料T型接头激光穿透焊试验,主要研究了焊接参数对焊缝成形和焊接裂纹的影响规律,分析了焊接裂纹形成原因,得到了较合理的焊接工艺区间。结果表明,对于GH3128/06Cr19Ni10异种材料T型接头激光穿透焊,连续焊比脉冲焊更易实现稳定焊接,获得良好焊缝成形。焊接裂纹是接头主要缺陷裂纹都在高温合金一侧产生,控制激光功率、保证对中可降低裂纹产生概率。焊接接头的另一种缺陷是表面下塌,保证间隙小于0.2mm可抑制下塌缺陷的产生。对由41条焊缝组成的模拟件进行了10MPa,5min水压测试,每条焊缝都满足要求。     

PBGA焊接开裂失效原因分析及改善

由于PBGA组件点位于四件与PCB之间,焊点的检查和检修成本很高,控制PCB组件焊接失效显得尤为重要。文章通过对焊接失效的焊盘镍层、金层结构进行了SEM、X-RAY分析导致焊接失效产生的主要原因,并针对此现象进行控制与改善。