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30 SMT Magazine • June 2015 of the solder penetration by means of 2.5D X- ray imaging is often very difficult, especially in the case of multi-row connectors. The pins of the individual rows are often concealed by one another. In addition, multi-row connectors are harder for the classification staff to interpret in a 2.5D image than in a three dimensional sec - tional image in which the solder joint is always displayed from above as a slice. The Salami Tactic To calculate the solder penetration, the THT solder joint is digitally divided into slices. In a method comparable to slicing salami, slices with In-LIne SOLDeR PeneTRATIOn TeSTInG WITH 3D X-RAy InSPeCTIOn continues the thickness "d" are generated and the area of each slice that is covered with solder is calculated. Figure 5 shows the digital section schematically. To calculate the solder penetration, a mini- mum allowable slice area is then defined in mm² in the THT test function. A check is then carried out slice-by-slice to determine whether this minimum area is achieved. If the area is under the minimum, this is the stop criterion for determining the solder penetration. The penetration height "h" (mm) is then calculated by the machine and, in the event of any faults, this measurement is displayed beside the X-ray fault image on the repair station/classification Table 2: overview of test coverage using 2D/3D Aoi and 3D AXi. Figure 3: connectors in 2.5D oblique radiation with easily visible defects in the solder penetration. figure 4: connectors with many successive rows of pins one behind the other in 2.5D oblique radiation; the solder joints are difficult to separate. Feature