Optimizing Component Placement: CMM vs. AOI

摘要

The importance of quality control in printed circuit board (PCB) assembly is intensifying in proportion to the shrinking geometries of boards and components. The challenge for placement equipment is also increasing as these shrinking components are extremely fragile. Inline automatic optical inspection (AOI) systems used for inspection, verification and measurement after component placement can help maintain a level of quality that seems to work well for most standard board configurations. However, AOI systems do not lend themselves to the proactive statistical process control (SPC) that is required for effectively streamlining today's highly complicated assembly lines. Today, performance baselines must be established based on knowledge of machine characteristics and using in-process and additional monitoring and trend analysis to anticipate and prevent defects. Rework used to be an expected part of production, but now it is avoided as much as possible because of the added cost factor and because many new assembly technologies and materials simply cannot be reworked. SPC can minimize both unscheduled downtimes and defective boards. The ability to adjust the process based on defects when they do occur allows continuous quality improvement.