Laser Ultrasound Inspection System for Quality Evaluation of Emerging Complex Packaged Electronic Devices

该奖项的研究目的是确定基于激光超声干涉测量技术的测量系统是否可用于微电子封装组件的焊点凹凸检测。该方法将使用同心光纤阵列来传递激光能量，以便在芯片封装组件表面的热弹性范围内产生超声波，而无需烧蚀封装。通过使用对称和非对称的信号处理方法来区分好的和坏的焊点，将提高系统的效率。对于对称方法，将使用一个样品表面上的两个对称位置的点来计算测量度量（例如时域相关函数），这将消除对信号处理算法中要求使用来自良好芯片的信号作为参考的依赖。小波和相关系数信号分析方法将用于确定对称或非对称凸点布局的芯片封装中是否存在缺陷。在早期研究中开发的用于分析一维包装的有限元模型将用于分析这些包装。将研究三维模型，以考虑这些包装中存在的所有层。该有限元模型将用于确定焊料凸起的数量和大小如何影响缺陷的可检测性。如果成功的话，这项研究将产生一种新型的低成本超声焊点检测系统，可用于评估各种电子封装的质量。该系统将提供快速优化测试程序的潜力，从而显着减少新产品的引入和加速周期时间。这将节省电子设备生产的成本。该项目还将为学生提供教育机会。

The research objective of this award is to determine if a measurement system based on a laser ultrasonic-interferometric technique can be used for solder bump inspection in microelectronic package assemblies. The approach will be to use a concentric array of optical fibers to deliver laser energy in order to generate ultrasound in the thermo elastic regime on the surface of a chip package assembly without ablating the package. The efficiency of the system will be increased by using symmetric and asymmetric methods of signal processing to discriminate between good and bad solder bumps. For the symmetric method, a measurement metric (such as the time-domain correlation function) will be calculated using two symmetrically located points on one sample surface, and this will remove the reliance on requiring the use of a signal from a good chip as a reference in the signal processing algorithm. Wavelet and Correlation Coefficient signal analysis methods will be used to determine the presence of defects in chip packages with either symmetric or non-symmetric solder bump layouts. A finite element model, developed in earlier research for analyzing one-dimensional packages, will be improved for analyzing these packages. Three-dimensional models will be investigated to take into consideration all the layers that are present in these packages. This finite element model will be used to determine how the number and size of the solder bumps affects the detectability of defects. If successful, this research will result in a novel and low-cost ultrasonic solder bump inspection system that can be used for evaluating the quality of a wide variety of electronic packages This system will offer the potential for rapid optimization of test programs resulting in significant decrease in new product introduction and ramp-up cycle times. It will result in cost savings in the production of electronic devices. The project will also provide educational opportunities for students.