Checking connectors with machine-vision systems

June 1, 2001
Even though PC manufacturers promote the capabilities of their hard drives, processors, and memory, the reliability of PCs depends upon the interconnects used between internal components.

Andrew Wilson,Editor,[email protected]

Even though PC manufacturers promote the capabilities of their hard drives, processors, and memory, the reliability of PCs depends upon the interconnects used between internal components. To ensure that connectors are of the highest standards, Samtec (New Albany, IN) uses automated, in-line machine-vision inspection systems from PPT Vision (Minneapolis, MN) to check its range of board-to-board, power-to-board, card-to-board, cable-to-board, and application-specific connectors.

"Inspection accuracy is a critical aspect of our business," says Steve Koopman, Samtec manufacturing engineering manager. "Faulty components result in device failure and damage the device manufacturer's reputation," he adds. Essential inspections for electronic connectors include pin presence/absence, coplanarity, and true position; these features are critical to successful seating of the connector on the circuit board and the mating of the connector to a cable.

Technician operates the Samtec high-speed- connector-inspection station. Capable of checking 1100 parts per hour, the system has increased both the inspection throughput by more than 100% and also the accuracy of inspection.
Click here to enlarge image

Until the company started producing high-density connectors, Samtec employees performed all part inspections manually. Some connectors contain as many as 500 pins in multiple row configurations. "With such a large quantity of small pins, the human eye is incapable of discerning coplanarity," says Koopman. "And, visual inspection could not achieve an acceptable accuracy level. We needed a machine-vision inspection system to check individual coplanarity among 500 tightly grouped pins with 100% accuracy to provide the required quality for these connectors," he adds. Additional goals included reducing inspection labor hours and increasing throughput.

After evaluating available hardware, Koopman selected the Passport DSL (digital serial link) system from PPT Vision for this task. In operation, from 10 to 40 connectors are loaded into open tubes on the inspection machine. Under gravity feed, these open tubes guide the connectors down to a machined slide. Here, individual connectors are allowed to fall down the slide under the direction of a PLC-based air-controlled gating system. Individually, each connector is held by a slide assembly that slowly moves the part under the field of view of the imaging system.

Three 550-mm Invaritar telecentric lenses from Melles Griot (Rochester, NY) coupled to three digital cameras from PPT Vision view the sides and top of the connector. "Telecentric lenses were important in this application," explains Josh Adwell, a Samtec engineer in the electronics group, "because they yield images from which precise measurements can be taken."

To check for coplanarity, pin sway, presence, and centerline, images of the connectors are taken from the top and both sides as the connectors are slowly moved by the slide assembly across the field of view of the three cameras. "PPT Vision's Connector Tool played a large part in the development of the vision application," says Adwell. As part of the vision program manager (VPM), the Connector Tool images many small sections of the connector as it passes under the DSL system's camera. The software then stitches these images into a complete view of the whole connector. The VPM software also streamlines the Passport DSL setup by replacing lines of code with graphic programming tools that users can "drag-and-drop" into a flow chart.

Samtec's first Passport DSL system, now in use for ten months, provides 100% parts inspection of the company's Quad Row Staggered SMT Socket Assembly. Samtec also has integrated the Passport DSL systems with secondary assembly equipment, such as pick-and-place systems.

"In addition to the original goals of increasing connector quality and throughput, the Passport DSL imaging system has decreased scrap, re-work, maintenance time, and replacement part costs," says Koopman. "Since the installation of the first DSL system, Samtec has eight more in various stages of development."

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