Development of THz Wave Tomography Technique and Nondestructive Evaluation of Delamination in Mounted Electronic Packages

1.太赫兹波产生与探测系统的研制飞秒激光器产生的脉冲激光束被分束器分成泵浦光和探测光。然后将泵浦光束聚焦在未掺杂的GaAs晶片上。由于光电导效应，从GaAs发射极产生脉冲THz光束。此外，太赫兹光束聚焦在ZnTe晶体白色上，探测光束也通过时间延迟聚焦在ZnTe传感器上。由于Pockels效应，电光调制引起探测光束的相位变化。利用一对平衡光电二极管，检测了太赫兹波相位随电场变化的情况。2.层析成像系统的构建将产生的太赫兹光束聚焦到被检样品上，将携带样品信息的反射太赫兹波聚焦到ZnTe传感器上。探测光束与ZnTe传感器处的反射THz光束同步。同时，通过电动载物台在x和y方向上移动样品。因此，通过调节作为时间门的时间延迟，记录从样品的横截面反射的THz波的振幅，并产生断层图像。3.电子封装中的分层的非破坏性评估对于THz波断层成像的实际应用，在安装的电子封装中的芯片和密封剂树脂之间的分层的3D图像的产生，以及建立装配线上安装的电子封装的无损评估方法。

1.Development of the generation and detection system of THz waveA pulsed laser beam generated by a fs laser was separated into a pump and a probe beam by a beam splitter. The pump beam was then focused on a nondoped GaAs wafer. Due to the photoconductive effect, a pulsed THz beam was generated from the GaAs emitter. Moreover, the THz beam was focused on a ZnTe crystal white the probe beam was also focused on the ZnTe sensor, through a time delay. Due to the Pockels effect, a phase variation of the probe beam was induced by the electro-optic modulation. By using a pair of balanced photodiodes, the phase variation which varies with the electric field of the THz wave was detected.2.Construction of the tomography systemThe generated THz beam was focused on the inspected sample, and the reflected THz wave which carries the information of the sample was focused on the ZnTe sensor. The probe beam was synchronized with the reflected THz beam at the ZnTe sensor. In the same time, the sample was moved in the x and y direction by an electric stage. Therefore, by adjusting the time delay as a time gate, the amplitude of the reflected THz wave from a cross section of the sample was recorded, and a tomograph was generated.3.Nondestructive evaluation of delamination in electronic packagesFor the practical use of the THz wave tomography, the generation of the 3D image of delamination between the chip and the encapsulant resin in the mounted electronic packages, and the establishment of nondestructive evaluation method of mounted electronic packages on an assembly line, are being promoted.