Electronics-Machine Vision Symbiosis Continues to Benefit Both Industries
| By: Winn Hardin, Contributing Editor
Wafers: The Front of the Front-End
As wafers have grown to 400-mm diameters to improve yields and profits, one might think semiconductor companies are completely interested in the largest cameras capable of resolving the smallest minimum features on the wafer in a single image. But that’s not necessarily true, explains Rich Dickerson, Manager of Marketing Communications at machine vision camera manufacturer JAI Inc. (San Jose, California).
“Resolution at the sensor level doesn’t seem to be as critical for them,” Dickerson says. “They’re using high-magnification lenses to look at very small details rather than the entire wafer and so are less concerned about how many pixels they can put on a single feature rather than about the quality of the optics. However, because of the incredibly small physical feature sizes – much smaller than what you look at on a PCB [printed circuit board] ¬– semiconductor companies are very interested in cameras sensitive in the UV [ultraviolet]. The wavelength of the light used to illuminate the feature must be shorter than the size of the feature if you want to see it at all.”
For these reasons, semiconductor companies tend to do more sampling of the wafer rather than 100% inspection of each wafer, although searches for large scratches and other gross defects will prompt 100% inspection early in the semiconductor wafer manufacturing process. “Once the wafer gets cut up into individual dies, they’re more likely to do 100% inspection of small features on the chip,” says Dickerson.
PCBs: Not Just ‘Made in Asia’ Anymore
Thanks to low labor costs, many of the world’s PCB contract manufacturers have operated out of Asian markets. However, factors such as automation benefits, rising labor costs, and a desire to manufacture closer to end markets to strengthen supply chains has many companies looking to new locations in Eastern Europe and Central America.
Speaking from Guadalajara, Mexico, during the recent Surface Mount Technology Association conference, Christoph Wimmer, Global Business Development Manager for Microscan (Renton, Washington) which focuses on machine vision and code reading, said that many contract manufacturers are moving operations to Mexico – led in part by the automotive industry.
“The automotive industry in particular is seeing strong growth in Mexico, as is demand for track-and-trace solutions,” says Wimmer. “A lot of companies that outsourced their electronics assembly to Asia are now moving production closer to their markets due to faster connection times between business units, improved interaction, and similar reasons.”
Microscan is seeing strong demand for its up-to-6k line-scan, camera-based, track-and-trace solution that can identify all barcodes on large printed circuit boards. Wimmer attributes the growing demand to several factors, including a continuing increase in automation in electronics manufacturing, protection against recalls in automotive, and a need for faster turnover to improve margins in a cost-conscious industry.
“The European electronics manufacturing industry leads the world in automation, followed by the U.S. and then Asia,” says Wimmer. “But even in Asia there’s growing demand for automated assembly and inspection as they deal with customers wanting more product traceability, higher quality and raising labor costs. And the more automation you use, the more traceability you need to verify that boards are being routed properly through the plant.”
Wimmer was at a plant recently “that was essentially operated by two people. And that takes a lot of automation.”
He also cites product switch over time as a major concern for electronics manufacturers, especially in the automotive sector. “Consumer electronics production lines normally have larger production runs with dedicated lines, but automotive electronics are increasingly going to smaller more flexible production runs,” Wimmer says.
In fact, Microscan conducted a study recently that showed in this industry, which has very tight margins, switch overs can take between 10 minutes and 2 hours. “If a company can cut that down, they can make a lot more profit,” Wimmer adds.
While Microscan focuses primarily on track-and-trace and secondarily on assembly verification, JAI is seeing big demand for smaller area-array cameras instead of line-scan cameras for imaging an entire board.
“Our PCB customers are interested in higher-resolution [cameras], but not extremely high resolution,” says JAI’s Dickerson. “A 5-MP camera is something that gets a lot of traction. They also want high frame rates and global shutters because they’re moving around boards, disk drive assemblies, or discrete components, and they do it relatively fast. So they want a blend of high resolution and hundreds of frames per second, which brings up CMOS cameras. A final point is a they like high dynamic range because so many of the components are highly reflective [think solder joints]. They could take multiple images at high speeds to accommodate the dynamic range requirements, but if they can use a high-dynamic-range camera, that simplifies the process.”
Dickerson adds that smaller-form cameras are also imperative because they often are mounted on moving platforms. And using small cameras means less mass and momentum to deal with, which leads to faster throughput.
In addition, 3D PCB inspection is becoming more important as a board needs to fit in smaller enclosures and tolerances get tighter, Dickerson notes.
Flat Panels, Low Noise, High Res
Finally, flat-panel manufacturers continue to put high resolution at a premium. “You’re essentially doing pixel-to-pixel comparisons, so they’re interested in the 20-MP camera, and in some cases the 8- and 12-MP cameras if it’s faster to move the camera around the flat panel than to try and process 20 MP of image data,” Dickerson says. “And [flat-panel manufacturers] have always been concerned about low noise because you’re essentially inspecting glass. You need low noise to be able to tell the difference between a small scratch and noise in the camera.”
As Asia continues to export more electronics manufacturing to other parts of the world while prototypes are still done in developed countries, the electronics market is becoming even more global. This bodes well for machine vision companies who – thanks to factory calibration and smarter software development kits – make it easier for a manufacturing line developed in San Jose to be duplicated in Guadalajara or wherever the customers gather.