Determination of BGA structural defects and solder joint defects by 3D X-ray laminography

The equipment and software for X-ray laminography has advanced rapidly in recent years. The latest systems can distinguish features as small as 5 μm in diameter and identify their locations to within 10 μm in three dimensions within an IC package. Details of complex closely spaced structures can be extracted readily with recently developed microlaminographs. At this resolution, the method is termed microlaminography. In this paper, the technology, methodology and results from a microlaminography system developed for failure analysis in IC packaging are presented. The copper traces in the built up layers of a BGA substrate were extracted and analysed individually. Bond-wire shorts in the plane of the solder resist in a lot of BGA assemblies were located and identified with subsequent verification by destructive physical analysis (DPA). 3D reconstructions of individual solder balls within an assembly were created and examined for defects. These analyses could not have been done by normal 2D X-ray; formerly only DPA could extract such information