Recent advances in x-ray technology

Taking x-ray images goes back over 100 years. Since then, there have been numerous advances in x-ray technology and these have been increasingly applied in helping the manufacturing of electronic components and assemblies, as well as in their failure analysis. Most recently, this has been rapidly driven by the reduction in device and feature size and the movement to using newer, lower density materials within the structures, such as copper wire replacing gold wire as the interconnection material of choice within components. Another driver for developments is the engineering of single 3D packages with multiple chips stacked vertically one on top of the other, which results in smaller and more efficient packaging of devices. In order to meet these challenges and those in the future, there have been a number of recent key improvements to the vital components within x-ray systems. The choice of available technologies, however, means selecting the tube/detector combination, which is optimum for a particular electronics inspection application, is no longer so clear-cut. For example, one configuration may provide certain benefits that are applicable for one area of electronics inspection, whilst being less valid for others. This paper will review the various x-ray tube and detector types that are available and explain the implications of these choices for electronics inspection in terms of what they provide for inspection regarding image resolution, magnification, tube power, detector pixel size and the effects of detector radiation damage, amongst others. This paper will also look in detail at the capabilities of high end CT systems to inspect wafer bumps, copper pillars and TSV's, new designs are reducing key dimensions of all of these interconnections challenging x-ray systems to produce clear images.