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82 PCB007 MAGAZINE I APRIL 2025 hybrid alignment point. e direct imaging machine then aligns optimally to both refer- ence types for maximum accuracy (Figure 7). Solder Mask Exposure Alignment Solder mask alignment sometimes pres- ents additional challenges due to: • Low-transparency solder masks (black, white, etc.) • Partial fiducial coverage by the solder mask Figure 8: Recognition of pad fiducials under black and white solder masks with partial coverage of the fiducial. Proper CCD lighting settings are crucial in overcoming these issues. With the right machine configuration and illumination adjustments, these challenges can be effec- tively managed (Figure 8). Summary In this article, we have explored registra- tion in PCB manufacturing, a critical factor influencing yield and precision. Registra- tion is interconnected with mechanical and optical processes, impacting nearly ever y step of PCB fabrication. As PCB designs continue to evolve, achieving precise registration will remain a key challenge—one that requires both advanced technology and a deep under- standing of process control . PCB007 Simon Khesin is the key account manager at Schmoll Maschinen GmbH. To read past columns, click here. Figure 7: Combo target recognized by MDI at outer layer exposure stage.