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

该奖项的研究目标是确定基于激光超声干涉技术的测量系统是否可用于微电子封装组件中的焊料凸点检测。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的表面上产生热弹性状态下的超声波，而不烧蚀封装。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料凸块，系统的效率将得到提高。对于对称方法，将使用一个样本表面上的两个对称定位的点来计算测量度量（诸如时域相关函数），并且这将消除对需要使用来自良好芯片的信号作为信号处理算法中的参考的依赖。小波和相关系数信号分析方法将被用来确定是否存在缺陷的芯片封装与对称或非对称的焊料凸块布局。一个有限元模型，在早期的研究中开发的分析一维包装，将改善这些包装的分析。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块的数量和尺寸如何影响缺陷的可检测性。如果成功的话，这项研究将导致一种新的和低成本的超声波焊料凸点检测系统，可用于评估各种各样的电子封装的质量。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推出和爬坡周期时间。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.