Machine-vision techniques for inspection of printed wiring boards and thick-film circuits

Abstract

In this paper, a review of machine-vision methods for microelectronic production and related unsolved problems is given, based on research paradigms and manufacturing needs that are seldom addressed in the literature. Although the importance of many industrial machine-vision applications has been identified, this paper will cover only a subset of these problems because of space limitations. Specifically, the automated visual inspection of printed circuit boards and thick-film circuits will be reviewed. Different aspects of these problems will be surveyed, including manufacturing considerations, contributions to sensing techniques, and, more importantly, digital image processing and analysis methods. For printed wiring boards, several production stages are addressed in which automated visual inspection plays a key role, from artwork to lamination of multiple layers and plated-through holes. In addition, the main inspection problems arising in populated boards will be reviewed, such as solder joint integrity and top-surface component placement. Finally, some machine-vision approaches used for thick-film and hybrid circuit inspection are considered.