What is an x-ray inspection system and where is it used?

A two dimensional (2-D) x-ray inspection system is basically an x-ray microscope. X-rays are produced by an x-ray tube and pass through the sample into an x-ray image capture device, such as a digital image intensifier, which converts the x-rays into images that the operator views. Any object or material within the analysed sample that has material of higher density than the surroundings will absorb more of the x-ray beam and so cast a darker shadow on the detector (see figure). In this way, solder and copper tracks appear dark compared with the laminated circuit board in a PCB, for example, when viewed in an x-ray system. In-system sample manipulation is required to pan over the test object (x and y plane) as well as to alter the available magnification (z-direction). Further details and definitions of the key features of x-ray inspection systems can be found in the ‘glossary of terms’ section of this web site.

X-ray inspection systems are used by the printed circuit board and semiconductor industries to check and monitor the quality of their manufacturing processes and products. It offers a way to investigate, in a non-destructive way, the locations and joints within their products that cannot be inspected optically. For example, x-ray inspection allows investigation of the solder joint quality, in situ, for area array packages such as Ball Grid Arrays (BGAs), flip chip devices and other chip scale packages (CSPs). It can also be used for investigating the wire attachment quality within semiconductor device packages. Many other applications exist. Without x-ray inspection, the only alternative would be by the damage/removal of the part in question for subsequent optical investigation. However. This optical approach makes the product/device unusable in the future and destroys the environment that needs to be investigated in the process.