密封环境中硅光敏芯片粘接缺陷的检测方法研究

The bad adhesive between photosensitive chip and base will lead to photosensitive chip off when silicon photoelectric detector is used in strong impact and vibration occasions or rapid decline of electrical performance after a period of time in actual use, and this failure is often fatal in weapons, aviation and spaceflight. At present, fault detectors can be eliminated by centrifugal test method. However, this method has some disadvantages, such as, fuzzy of test criterion, poor reliability, low efficiency and possibility to introduce new damage. Now, the nondestructive testing of adhesive defect has become the most difficult problem in the screening of photoelectric detector due to the small volume of the detector and chip and basal packaging in sealed environment. So that, the proposed project aims to develop a noncontact photoacoustic nondestructive testing method to detect the adhesive defects of small-sized material in sealed environments based on the advantage of laser ultrasonic. In the project, we will theoretically study the excitation and modal characteristic of ultrasonic in the horizontal limited complex layers structure generated by laser pulse focused on the interface between the inert gas and photosensitive chip, and research the influence of boundary bound on laser ultrasonic, and analyze the mechanics of the interaction between adhesive defect and laser ultrasonic in small-sized structure, and then develop the quantitative relationship between adhesive defect and laser ultrasonic. An experimental device for the photoacoustic test of adhesive defect in small-sized layer structure in sealed environment will be developed and actual testing for adhesive defect in typical photodetectors will be prosecuted.

光敏芯片与基座间粘接不良将导致硅光电探测器在强冲击和振动场合出现光敏芯片脱落或实际使用一段时间后电性能的快速衰退，这种失效在兵器、航空和航天等领域往往是致命的。目前靠离心试验筛选剔除故障样品，这种方法试验判据模糊、可靠性差、筛选效率低且可能引入新的损伤。由于探测器体积小、芯片和基底封装在密封环境中，这使得粘接缺陷的无损检测成了探测器筛选中遇到的最为棘手的难题。本项目旨在发挥激光超声非接触点激发的优势发展密封环境中小尺寸材料粘接缺陷（含粘接强度）的非接触式光声无损检测理论和方法。理论上研究脉冲激光聚焦惰性气体-硅光敏芯片界面在横向受限多层复杂结构中的超声激发及模态特征, 讨论边界束缚对激光超声的影响，分析小尺寸结构中超声与粘接缺陷的作用机理，建立粘接缺陷与超声波参量的定量关系。实验上建立密封环境中小尺寸层状材料粘接缺陷光声检测的实验装置，并将其应用于典型硅光电探测器粘接缺陷的实际检测。

为了解决密封环境中硅光敏芯片粘接缺陷的快速无损检测问题，本项目发挥激光超声非接触点激发的优势发展密封环境中小尺寸材料粘接缺陷（含粘接强度）的非接触式光声无损检测理论和方法。通过项目组三年的努力，解决了尺寸受限三维层状结构中光、热、力、声多场耦合分析、复杂超声模态中粘接缺陷信息的提取方法、流（气）-固界面上激光超声波的光学定量探测等多个关键问题，建立了惰性气体-硅光敏芯片界面超声波的激光激发、传播及其与界面粘接缺陷相互作用过程的数学模型和有限元算法。该算法一方面能够得到超声波激发过程中的全场数据，另一方面能够方便地考虑材料热物理特性随温度的变化，且在材料形状和结构处理方面有很好的鲁棒性，是处理特殊复杂结构中激光热弹激发超声波问题的有效途径。项目创新提出透射式光偏转探测方法，并建立了相应的光纤耦合传感装置和密封充满惰性气体环境中激光激发气-固界面超声波进行硅光敏芯片粘接缺陷检测的全光学系统。该装置不仅具有灵敏度高、易调节等优点，更重要的是区分了测量气-固界面超声波时气体折射率改变和界面形变两个分量，能够准确测量气-固界面超声波，为正确分析研究密封充满惰性气体环境中气-固界面上激光超声波提供了实验基础。此外，还通过数值仿真研究了横向受限层状微型结构中激光激发超声场的空间和时间分布特征；讨论了不同边界束缚形式对超声波模态的影响；还研究了光敏芯片粘接缺陷对层状复杂结构中激光超声波形的影响；寻求不同形式的粘接缺陷在激光超声信号中的表现形式；讨论了粘接缺陷大小、位置、形状等参量对激光超声波特征参量的影响，为探讨密封充满气体环境中粘接缺陷测量方法做出了有益尝试。