An x-ray inspection system comprising: a cabinet; an x-ray source within the cabinet; a wafer support within the cabinet configured to support a semiconductor wafer to be inspected, a wafer support positioning assembly for positioning the wafer support relative to the x-ray source, wherein the x-ray source is located above the wafer support and is fixed relative to the cabinet, wherein the wafer support positioning assembly allows for relative movement between the wafer support and the x-ray source, and comprises a first horizontal wafer positioning mechanism (212, 214) for moving the wafer support in a first horizontal direction, and a second horizontal wafer positioning mechanism (216, 218) for moving the wafer support in a second horizontal direction; an x-ray detector within the cabinet for detecting x-rays that have passed through the wafer to record an image of the wafer; a detector positioning assembly for positioning the x-ray detector relative to the x-ray source; a wafer loading and unloading assembly configured to transport wafers from outside of the cabinet to the wafer support, and from the wafer support out of the cabinet; a controller configured to control the operation of the x-ray source, wafer support positioning assembly, detector positioning assembly and the wafer loading and unloading assembly; and an image processor connected to the controller and the x-ray detector and configured to process image data received from the detector; characterised in that: - the wafer support positioning assembly is located below the wafer support; - the wafer support positioning assembly comprises a vertical wafer positioning mechanism (214, 216) for moving the wafer support in a vertical direction; and - the x-ray inspection system further comprises at least one fan filter unit configured to force air through the cabinet from an air inlet above the wafer support to an air outlet below the wafer support. a cabinet; an x-ray source within the cabinet; a wafer support within the cabinet configured to support a semiconductor wafer to be inspected, a wafer support positioning assembly for positioning the wafer support relative to the x-ray source, wherein the x-ray source is located above the wafer support and is fixed relative to the cabinet, wherein the wafer support positioning assembly allows for relative movement between the wafer support and the x-ray source, and comprises a first horizontal wafer positioning mechanism (212, 214) for moving the wafer support in a first horizontal direction, and a second horizontal wafer positioning mechanism (216, 218) for moving the wafer support in a second horizontal direction; an x-ray detector within the cabinet for detecting x-rays that have passed through the wafer to record an image of the wafer; a detector positioning assembly for positioning the x-ray detector relative to the x-ray source; a wafer loading and unloading assembly configured to transport wafers from outside of the cabinet to the wafer support, and from the wafer support out of the cabinet; a controller configured to control the operation of the x-ray source, wafer support positioning assembly, detector positioning assembly and the wafer loading and unloading assembly; and an image processor connected to the controller and the x-ray detector and configured to process image data received from the detector; characterised in that: - the wafer support positioning assembly is located below the wafer support; - the wafer support positioning assembly comprises a vertical wafer positioning mechanism (214, 216) for moving the wafer support in a vertical direction; and - the x-ray inspection system further comprises at least one fan filter unit configured to force air through the cabinet from an air inlet above the wafer support to an air outlet below the wafer support. - the wafer support positioning assembly is located below the wafer support; - the wafer support positioning assembly comprises a vertical wafer positioning mechanism (214, 216) for moving the wafer support in a vertical direction; and - the x-ray inspection system further comprises at least one fan filter unit configured to force air through the cabinet from an air inlet above the wafer support to an air outlet below the wafer support.