QMT Features: April 2016
Vision cuts out bottlenecks
A leading microwave circuit manufacturer uses a 3D CNC vision system to speed inspection

Teledyne Labtech’s circuits can be found in many demanding applications including defence electronics, air traffic control systems, global telecommunications and satellite communications systems. Its special expertise is in the manufacturing of complex microwave PCBs, from double-sided PTFE, Mixed Dielectric Multilayer PCBs, through to complex metal-cored PCBs. The company also offers plated through holes (PTH), blind and buried vias, laser cut cavities, embedded resistors and connectors.

The sheer complexity and exacting dimensional tolerances of these intricate circuits, together with the inherent material instability of the PTFE laminates in particular, necessitates the use of thorough in-process quality checks throughout each stage of manufacture. On completion, each of the company’s PCBs undergoes meticulous, high-precision final inspection. As rising production levels and ever tighter customer demanded tolerances recently began to place a strain on the company’s existing inspection equipment, a search was made for a fast throughput, high-accuracy, non-contact measuring system that would remove the possibility of inspection bottlenecks.

Dick Heinrich, Site Director, Teledyne Labtech Ltd. explained. “As rising global demand for our microwave circuit solutions had started to place a strain on our final inspection department, it became clear that we needed to source a highly accurate, non-contact measuring technology that could keep pace with our increased output.

“Given the technical developments in the field of non-contact metrology, we compiled a list of system requirements that would not only solve our inspection capacity problem, but also further enhance our capability. Having approached our existing vision measuring systems supplier with a challenging system specification, the company was unable to meet our demanding requirements.”

Following capability trials, decision was made to invest in a Quick Vision non-contact system from Mitutoyo.
This is a non-contact dimension measurement system that uses a CCD (charge-coupled device) camera to take images that are magnified by a high-quality optical lens. The edges of the workpiece under inspection are then detected by the use of advanced image processing technology.

Commenting on the trials at Mitutoyo’s technical centre, Mr Heinrich said: “Not only were we very impressed with the ease and speed of generating programs related to the PCBs that we had brought along, the speed of the resulting inspection routines that took place in fully-automatic CNC modes and the precision of the machine’s results, convinced us that we had found the ideal answer to our needs.

“We currently use the system on a day-shift basis; however at peak times, such as month-end, we extend its hours of operation. Since its installation, in addition to delivering the required levels of accuracy and consistency, the machine has considerably improved our inspection throughput speed. We expect our inspection times to reduce further as we gain experience and continue to develop new, more efficient programs. To this end, we are beginning to investigate the possibility of loading multiple circuits onto the machine’s bed.

“Our operators particularly appreciate the Quick Vision’s useful backlighting feature, that allows us to accurately measure track features immediately above the substrate (heel of a track), and its ability to automatically record inspection data. We intend to use the inspection data to provide a useful feedback loop to the corresponding manufacturing process steps to adjust specific settings that would allow yield improvements of the process.”
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