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June 2016 • SMT Magazine 89 Figure 9 shows the height variation of the solder joint from a minimum value of 25×20 µm obtained at the component electrode and a maximum value of 35×20 µm. The obtained minimum value is higher than the minimum value specified on IPC A-610 for the solder joint height at the component electrode [9] . Solder Joint Classification The 3D-SJR allows the implementation of new classifiers to analyze the solder joint, namely length, height and volume (Table III). The solder joint height is computed for a spe- cific y coordinate of the inspection area. The pa- rameter cr is the camera resolution used in the acquisition system. The IPC-A-610 standard specifies the limits for the solder joint of SMD components. Ac- cording to this standard, the solder height (SJH) should be higher than 25% of the component electrode height [9] . Figure 11 shows an example described in the IPC-A-610 document, where the specification for the solder height can be seen close to the component electrode. The pa- rameter H represents the component height, and the parameter F represents the solder joint height at the component electrode. The recon- struction of the surface solder shape (3D-SJR) determines the F value to be used in the solder joint classification on the AOI system. Taking into consideration the IPC-A-610 standard regarding the specification of the sol- der joint along the component electrode, as seen in Figure 12, it was implemented a new classifier (20). Figure 9: Solder joint height variation. Table III: 3D-SJR Classifiers. Figure 10: Solder joint reconstruction of the inspection area for a specific y coordinate. Figure 11: Solder joint height [9] . 3D SOLDER JOINT RECONSTRUCTION ON SMD BASED ON 2D IMAGES