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

集成电路封装的进步，更小型化，高布线密度和安装的平面组件要求技术的无损检测能力不断提高。扫描声学显微镜（SAM）特别适用于重建物体的内部结构。它可以检测空气夹杂物或裂缝等空隙，或测试边界层以定位分层。超声图像比x射线图像能更好地显示这些空洞。为了获得超声图像，聚焦单探头扫描试样。超声波显微镜的工作频率范围为10至230兆赫兹，可以绘制反射信号的振幅，并在平面结构中达到微米范围内的分辨率。如果结构的任何部分的声速是未知的，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，则SAM将失败。由于需要对每一层进行必要的调整和单独的测试，SAM需要大量的时间。因此，SAM不适合用于工业生产的在线监控。该项目的目标是提高图像质量，扩展测试场景，减少扫描声学显微镜的必要测量时间。为了实现这一目标，必须提供新的测量技术和硬件，特别是结构化相控阵，它可以聚焦和引导声场。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，多通道扫描声显微镜和高达40 MHz的分段环形阵列将被开发和构建。这些阵列的元素数量应尽可能低，而传统探针的分辨率应达到或超过。由于用于构建这些阵列的商用复合材料是不可用的，因此需要先进的软模具技术，以获得具有球形曲率的高达40 MHz的精细缩放复合材料。先进的软模技术提高了相控阵结构的自由度，并允许开发完全符合本项目及以后测试问题的探头。

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.