Visual input for inspection and closed loop control of a hybrid circuit printer



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A machine vision system is used to inspect thick film printed circuit boards. Inspection functions detect defects and misalignment and feed corrective data back to the processing facility. This thesis describes a visual Inspection system for the thick film screen printing process in which complex patterns are printed on ceramic substrates. The image algebra, based on set theory, is utilized as a vehicle for image processing and analysis algorithm. A predefined shape is used as a probe to test the nature of a circuit pattern. A computerized visual inspection specification is created to define the inspection criteria and the system requirements. An algorithm is developed to snap the image and to detect faults based on programmable parameters. It also measures the misregistration of the circuit with respect to the edge of the substrate. A computer control algorithm, utilizing digital control theory, has been developed to control an alignment system of a screen printer. The control algorithm has the capability of accepting visual feedback input signals for a real-time closed-loop control system.



Hybrid integrated circuits--Inspection, Thick-film circuits, Automatic control--Data processing