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54 SMT Magazine • August 2014 aRTIClE INtRODuCtION tO INLINE aXI tEChNOLOgy continues Manual (MXI) • X-ray microscope • QA, human/manual calls • Very low volume; time-consuming Computed Tomography (CT, micro CT) • X-ray microscope • Quality assurance, research • Very high 3D quality imaging, very low speed aXI Market Drivers Ever since the first through-hole compo- nents were hand-placed on PCBs, methods have been needed to test the resulting product for manufacturing defects. The initial use of man- ual visual inspection yielded uneven results, as operators would get tired and bored of repeti- tive tasks. While functional testing verified that the product was operational at the moment it left the factory, it didn't reveal any structural sol- der joint defects which might cause early failure due to shocks received during transport, or as a part of deployment. Weak solder joints would break, resulting in the whole product being re- turned from the field for repairs. The traditional inspection method for structural defects was cross section, an expensive approach which re- quires destruction of the inspected board. As the electronics market moved to high volume production, automated inspection equipment became indispensable to maintain high yields and stable production quality, SPI (solder paste inspection), AOI and AXI. X-ray proved to be the most suitable non-destructive inspection technology for high-density boards with hidden joints. Mobile Electronics The growing success of mobile electronics with limited PCB space has forced a transition towards higher density packages with bottom- facing solder joints (BTCs) and multiple layers Figure 11: inline AXi adoption drivers in electronics manufacturing include cost-cutting measures as well as technological developments.