SMT007 Magazine

SMT-June2016

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92 SMT Magazine • June 2016 tion, the minimum allowable height of the sol- der is 12.5 pixels on the Z axis. 21 Figure 16 shows the obtained reconstruction of the solder joint surface where the contour lines of the solder joint is within the specifica- tions of the IPC A-610 standard. Figure 17 shows a SMD resistor where the left pad has a lower solder quantity when com- pared with the right pad. Applying 3D-SJR, it is possible to verify that the solder joint is not according to the specifica- tion on the IPC A-610. In these specifications at least 75% of electrodes should have a minimum solder joint of 25% the component electrode height. Figure 18 represents the contour lines of the solder surface obtained by applying the 3D-SJR method. The obtained results of the solder joint (SJ) classifier for the two samples show that on the bad sample only 37% of the electrodes have solder joints higher than 25% of the electrode height. In this case, 3D-SJR allows the verifica- tion that the solder height in the component electrode is not according to IPC A-610 stan- dard specifications. Conclusions Due to the specular reflection of the solder joint, the solder joint analysis is the most dif- ficult step in AOI systems. With the structured ring light system, it was possible in the im- age acquisition to correctly identify the solder shape and improve solder analysis. The proposed 3D-SJR method improves the actual AOI system solution for solder joint anal- ysis and achieves better results in fault detec- tion not possible with the traditional 2D AOI systems. Nowadays because of the difficulty of 2D AOI systems to provide solutions for inspection in several cases of failure detection, companies have started buying 3D AOI systems that are in Figure 16: Solder surface contour lines. Figure 18: Solder surface level curve (bad sample). Figure 17: Bad solder joint sample. 3D SOLDER JOINT RECONSTRUCTION ON SMD BASED ON 2D IMAGES

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