X-ray Microanalysis in Scanning Electron Microscopes (SEMs) is a powerful, widely used, and well known technique. From its inception, elemental maps using characteristic X-rays produced in the sample when it is struck by the incident electron beam have been correlated with the electron image of the same region. Such methodology provides the elemental distribution in the region of interest on a micro scale. The intrinsic problem with such correlation, however, is that the perspective (line of sight) of the Back-Scattered Electron Detector (BSED) does not match that of the X-ray detector (now usually called SDD for the modern Silicon Drift Detector) because the size and complexity of the two detectors required them to be placed in different physical locations. Using Secondary Electron images to correlate with X-ray maps is at least as encumbered because the SED bias voltage enables the collection of the low energy secondaries from the back side of surfaces that would otherwise be shielded from the detector, often eliminating shadows completely. The differences in parallax and perspective between the BSED and the X-ray detector, and in the case of an SED, the elimination of line-of-sight dependence, often makes correlation between the X-ray and the electron images problematic, particularly to non-experts who may find it difficult to make the mental corrections to adjust for and ignore these differences. The correlation is especially difficult for samples having rough surfaces, particularly those with macro scale topography (such as populated PCBs, fracture surfaces, large particle dispersions, etc.).
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