CST Global’s new automatic visual inspection machine trebles laser test throughput

III-V optoelectronic foundry Compound Semiconductor Technologies Global Ltd (CST Global) of Hamilton (near Glasgow), Scotland, UK has introduced an automatic visual inspection machine, trebling laser throughput and increasing test accuracy.

“We do a visual inspection of all lasers,” says production project engineer Colin Jackson. “Our recently introduced automatic bar stacker machine produces up to 50 2-, 3- or 4-inch wafer bars at once. The bars are held in a gel pack for inspection. At around 110 lasers per bar, this is over 5000 lasers at a time,” he notes. “We used to manually inspect two gel packs per 12-hour shift. Since introducing the bar stacker, this manual inspection was not fast enough. The new automatic visual inspection machine easily handles six gel packs per shift.” This increases throughput from 10,000 to 30,000 lasers per shift, removing the bottleneck.

CST Global worked with the visual inspection machine manufacturer Keyence and software developer Wolf to commission, develop and optimize the new visual inspection machine. “Software is used to recognize the laser ID number, recording an image of each laser for reference,” says Jackson. “It removes human error, making the process auditable, repeatable and totally consistent,” he adds.

“The visual inspection machine brings other key benefits to CST Global. We now only need one inspector per shift, allowing us to re-deploy valuable resources elsewhere,” comments Jackson. “We can track wafer batch quality, working with our key suppliers to help increase yield. Finally, we are streamlining the visual inspection process to handle yet more gel packs per shift. We expect throughputs to near 40,000 lasers per shift shortly.”