Digital-signal-processor-based inspection of populated surface-mount technology printed circuit boards

The inspection of surface-mount technology printed circuit boards is an increasing problem due to the fine pitch technology that is beginning to be used. Human visual inspection is unsuitable for this technology necessitating the use of computer-based inspection systems. Correlation has been used by the authors to detect solder bridges and misaligned leads on surface mount components. This operation is too slow on a general purpose computer requiring over seven seconds to inspect each component lead. A digital signal processor based multiprocessor system has been designed to provide the required computational power. Using optimization techniques and restructuring the data to be correlated enables each processor in the system to inspect 424 leads per second.