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利用分束器将飞秒激光产生的脉冲激光分离成泵浦光束和探测光束。然后将泵浦光束聚焦到非掺杂的砷化镓晶片上。由于光导效应，从发射极产生了脉冲太赫兹光束。此外，THz光聚焦在一块白锌晶体上，探测光通过一段时间延迟聚焦在锌Te传感器上。由于普克尔斯效应，电光调制引起了探测光束的位相变化。2.层析成像系统的构建将产生的太赫兹光束聚焦在被测样品上，反射的携带样品信息的太赫兹波聚焦在锌Te传感器上。探测光束与在ZnTe传感器上反射的太赫兹光束同步。同时，通过电台使样品沿x和y方向移动。因此，通过调整时间延迟作为时间门，记录从样品的横截面反射的太赫兹波的幅度，并生成层析图像。3.电子封装分层的无损评估为太赫兹波层析成像的实际应用，正在推动电子封装贴装芯片与封装树脂之间分层的三维图像的生成，以及建立装配线上贴装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.