Considerations for minimizing radiation doses to components during X-ray inspection

The ability to undertake non-destructive testing on semiconductor devices, during both their manufacture and their subsequent use in printed circuit boards (PCBs), has become ever more important for checking product quality without compromising productivity. The use of X-ray inspection not only provides a potentially non-destructive test but also allows investigation within optically hidden areas, such as the wire bonding within packages and the quality of post solder reflow of area array devices (e.g. BGAs, CSPs and flip chips). During X-ray inspection the sample is bathed in the ionizing radiation of high-energy photons, so the sample receives a radiation dose. Certain devices are susceptible to damage by ionizing radiation. Therefore, this susceptibility may require the user to consider the radiation dose being given to these items during the X-ray inspection process to ensure critical thresholds are not exceeded. This paper will discuss the issues that a user of these radiation-sensitive components may wish to consider, together with practical suggestions as to how to measure and minimize the radiation dose for best practice during X-ray examination.