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56 SMT Magazine • August 2014 (PoP, stacked dies). These high-density packages do not have visible solder joints and cannot be reliably inspected using AOI, making AXI the only reliable method to inspect for structural defects incurred during assembly and solder re- flow. The increased use of wireless technologies in mobile devices also brings metal shielding mounted onto the PCBA, which prevents stan- dard visual inspection. These components can be only inspected using X-ray imaging. Cost-reduction through Integration Cost-reduction measures in electronics man- ufacturing are driving the adoption of highly integrated IC packages and more complex dual- sided PCB assemblies with reduced test access. This further reduces the utility of traditional optical inspection and electrical testing. AXI has therefore become an important element in reducing rework costs, by verifying actual de- fects and eliminating unnecessary repairs. INtRODuCtION tO INLINE aXI tEChNOLOgy continues aRTIClE Process Quality Management Extended inspection coverage offered by In- line Automated X-ray Inspection provides real- time solder joint quality information which can be used to statistically monitor and adjust the manufacturing process and maintain stable production quality. Increasing demands on high production yields and process miniaturization stress inspec- tion capabilities of optical and electrical inspec- tion systems, which are becoming unable to test the quality of many solder joints. X-ray inspec- tion is therefore becoming a key component for maintaining stable quality and eliminating pro- cess variation. aXI in PCB assembly Manufacture Defect Detectability Matrix Based on different principles, the three dom- inant inspection and testing technologies each Figure 12: optical, X-ray and electrical testing each cover a different segment of manufacturing defects that affect typical electronics production.