针对焊锡球连接的检测难题，乔治亚理工大学开发了一种新的非接触、无损检测方法，能够检测缺失焊锡球、未湿润（开路）、脱焊或裂纹焊点以及错位或损坏的封装。该技术通过脉冲激光激发微电子组件振动，干涉仪测量其表面位移，缺陷会导致振动响应变化。通过信号处理技术对比测试设备和无缺陷设备的振动签名，识别缺陷。研究目标是创建低成本、高灵敏度、准确、快速且高度自动化的原型系统，用于在线检测、工艺开发和故障分析。此技术可能无损检测因翘曲或热膨胀系数不匹配导致的芯片基板应力。论文讨论了当前检测系统的性能和局限性，并探讨了该技术在微电子制造和开发中的新颖应用及其潜在影响。
摘要：
Inspection of solder bump interconnections is more difficult than conventional lead-frame solder connections because the solder joints are hidden from view. Current inspection methods, such as automated optical inspection (AOI), automated x-ray inspection (AXI) and acoustic micro imaging (AMI) have limited capabilities for inspecting the mechanical integrity of solder joints. A new noncontact, nondestructive inspection technique developed at Georgia Tech can evaluate the chip-to-substrate mechanical integrity by detecting missing solder balls; nonwetted (open), disbonded or cracked solder joints; and misaligned or cracked packages. In addition, this new technique may provide a nondestructive means to detect residual stress in the chip-substrate bond due to warpage or coefficient of thermal expansion mismatch. Pulsed laser energy excites a microelectronic component into vibration, and an interferometer measures its out-of-plane surface displacement. Defects in the solder joints or silicon chip itself cause measurable changes in the vibration response. Signal processing techniques are used to identify defects by comparing vibration signatures of tested devices to a reference, defect-free device. The long-term goal of this research is to develop a low-cost, high-sensitivity, accurate, fast, highly automated prototype system to demonstrate the use of this technique for online inspection, process development and failure analysis. This paper discusses the design and performance of the current inspection system, presenting specific results for a wafer-level chip scale package (CSP) and a flip chip. These results aid the discussion of system performance and limitations. Novel applications of this inspection technique and the expected impacts in microelectronics manufacturing and development are also discussed.
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