3D AOI uses multiple high speed, high resolution cameras to detect the smallest of defects in the placement and height of microchips, electronic components and applied solder paste (SPI) in electronic circuit boards (PCB). In order to fully leverage all the pixels acquired by these high-end cameras, a communication standard is needed to deliver in-depth pixel data for meaningful analysis. CoaXPress in particular seems to tick all the boxes.
3D AOI Overview
3D AOI stands for 3D Automated Optical Inspection. This highly demanding process step in electronics manufacturing typically entails a 100 percent, 3D, inline quality control of printed circuit board components. With up to 5 cameras, several ROIs (Regions of Interest) are simultaneously examined. The acquired pixel data is subsequently offered to a frame grabber, which in its turn transfers the data to a PC running dedicated imaging software, using the PCI or PCIe bus for further calculations. Since today’s camera specifications are formidable – a 12-megapixel resolution at 180 frames per second is the new standard – high bandwidth solutions are necessary to meet the relentless real time requirements introduced by these cameras. And although there are several high speed communication standards that at first sight seem to fit the bill, each have their own specific trade-offs upon further inspection. With one exception: CoaXPress.
3D AOI Challenges: Faster and Smaller
Several challenges are facing the electronics sector. With at least one new phone model a year, manufacturers call for ever shorter development cycles in order to stay ahead of the competition. For cost-efficiency, the production capacity is on constant need of ramping up, calling for higher throughputs of production machines and inspection equipment. Although Moore’s law seems to reach its limits in terms of transistor density, new architectures still allow for a doubling in calculating power within the same chip size every 1.5 to 2 years. In other words: things get smaller still, a trend which can only be enabled and leveraged by more precise systems. More precise inevitably means a higher resolution and a higher pixel quality. Measured in pixel depth – 8 bit being the standard for 3D AOI – pixel quality determines not only how small a thing we may look at, but also the reliability of our observation. In other words, data integrity is increasingly a factor in high-end vision applications such as 3D AOI. Effects such as EMC become ever more important, especially at greater cable lengths.
3D AOI and CoaXPress: All Boxes Ticked
When looking at the 3D AOI requirements and comparing the various communication alternatives, CoaXPress seems the most favorable. For starters it boasts an impressive 6.25 Gb/s (12.5 Gb/s in 2017), including up to 13 W of power and trigger capabilities. Being a serial point to point communication standard this is accomplished with a single cable, also allowing for much greater cable lengths (up to 100 meters), more flexibility and shielding against electromagnetic interference. These mechanical and electrical properties might seem ‘a nice bonus’, but they actually offer direct value. Greater cable lengths and smaller bending radii mean a more compact build of 3D AOI stations, without the need of amplifiers or other devices. The same holds true for enabling twice the bandwidth with the same cable. OEMs need fewer frame grabbers, shrinking the machine footprint while at the same time offering scalability and reducing costs.