Developement of improved imaging techniques and new, structured, high frequency ultrasound transducers for the acoustic microscopy

随着集成电路封装的小型化、高布线密度和扁平元件的安装，对非破坏性测试技术的要求越来越高。扫描声学显微镜(SAM)特别适用于重建物体内部结构。它允许检测空气夹杂或裂缝等空洞，或测试边界层以定位分层。超声波图像比X射线图像更好地显示这种空洞。为了获得超声图像，聚焦的单一探头扫描样本。超声波显微镜工作在10至230 MHz的频率范围内，绘制反射信号的幅度，并达到微米范围内的分辨率，适用于平面结构。如果结构的任何部分的声速未知，所得到的图像是不正确的。如果必须测试具有倾斜或弯曲界面的结构，SAM将失败。山姆需要大量的时间，因为每一层都需要必要的调整和个别的测试。因此，SAM不适合用于工业生产的在线监测。该项目的目标是改善图像质量，扩大测试场景，并减少扫描声学显微镜所需的测量时间。为了实现这一点，应提供新的测量技术和硬件，特别是允许聚焦和控制声场的结构化相控阵。新的测量技术允许在不同深度和倾斜或弯曲表面下同时进行测试，以及确定结构每个部分的声速。因此，将开发和建造高达40 MHz的多通道扫描声学显微镜和分段环形阵列。这些阵列的单元数应尽可能低，而常规探头的分辨率应达到或超过常规探头的分辨率。由于目前还没有用于制造这些阵列的商用复合材料，因此必须采用软模技术，以获得高达40 MHz、球面曲率的精细复合材料。先进的软模技术提高了构造相控阵的自由度，并允许开发完全匹配本项目和其他项目测试问题的探头。

The progress in packaging of integrated circuits, with more miniaturisation, high wiring densities and mounting of flat components requires techniques of non-destructive testing with increasing capabilities. Scanning acoustic microscopy (SAM) is especially well applicable to reconstruct the inner structure of objects. It allows to detect voids like air inclusions or cracks or to test boundary layers to localise delaminations. An ultrasonic image displays such voids much better than an X-ray image. To obtain an Ultrasonic image a focussing single probe scans the specimen. Ultrasound microscopes work in a frequency range of 10 up to 230 MHz, plot the amplitudes of the reflected signals and reach a resolution in the range of microns for flat structures. The resulting image is incorrect, if the sound velocities of any part of the structure are unknown. SAM fails if a structure with inclined or curved interfaces has to be tested. SAM needs a lot of time because of the necessary adjustment and the individual test of each layer. Therefore, SAM is not suitable for an application on online monitoring of industrial production. The goals of the project are an improvement of image quality, the expansion of test scenarios and a reduction of the necessary measuring time for the scanning acoustic microscopy. To reach this, new measuring techniques and hardware, especially structured phased arrays, which allow focusing and steering the sound field, shall be provided. The new measurement techniques allows a simultaneous testing in different depths and under inclined or curved surfaces as well as a determination of sound velocity in each part of the structure. Therefore a multichannel scanning acoustic microscope and segmented annular arrays up to 40 MHz will be developed and constructed. The number of elements of these arrays should be as low as possible whereas the resolution of conventional probes shall be reached or beaten. Because commercial composites for the construction of these arrays are not available, the soft mold technique shall be advanced, to obtain fine scaled composites up to 40 MHz with a spherical curvature. The advanced soft mold technique enhances the degree of freedom for structuring phased arrays and allows the development of probes which exactly match the problem of testing for this project and beyond.