X-Ray Based Methods for Nondestructive Testing and Material Characterization
The progress in complexity and miniaturization in the field of new materials as well as in micro production needs improvements and technical advances in the field of micro NDT to provide better quality data and more detailed knowledge about the internal structures of micro components. Nondestructive methods like radioscopy, ultrasound, optics or thermal imaging therefore increasingly gain in importance with respect to ongoing product and material development in the different phases like material characterization, product control or module reliability. Depending on all these different features like application fields, material inspection or characterization, this contribution will give an overview about the radioscopic based methods related to their most important applications.
Radioscopic inspection has become one of the most powerful tools in the field of non destructive testing for industrial material inspection since the discovery of X-rays by Conrad Wilhelm Röntgen in the year 1895 (Nobel Price 1901). Already at this time, C.W. Röntgen had to face the same problems, which are still today regarded as major challenges with respect to advanced research and development for nondestructive testing:
- The high dynamic range of measured intensities caused by exponential attenuation law for radiation in matter
- The superposition of object structures along the radiation beam direction, caused by projective geometrical imaging (projection technique)
- Long exposure times, essential for a reasonable signal to noise ratio (SNR)
- Loss in contrast by diffuse background, generated by scattered radiation which occurs during Compton interaction of photons with electrons of the outer atomic shell
- The strong attenuation by metals compared to weak absorption of human skin, organs and tissue
Today, in modern industrial quality control, x-rays are used in two different ways:
1.Two dimensional radioscopic transmission imaging (projection technique), usually applied to inline inspection tasks in application fields like lightweight material production, electronic component soldering or food production.
2.Computed tomography for generation of three dimensional data, representing spatial information and density distribution of objects. CT application fields are on the one hand the understanding of production process failure or component and module inspection (completeness) and on the other hand the dimensional measuring of hidden geometrical outlines (metrology).
This presentation demonstrates the methods including technical set ups (x-ray source and detector), imaging and reconstruction results and the methods for high speed and high resolution volume data generation and evaluation.
