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Automated Optical Inspection Keeps Pace With QA Demands
Small components and fine circuit features such as this have made manual inspection methods impractical if not even possible for checking today's PCBs.

Smaller components and more densely packed printed-circuit boards (PCBs) are challenging the best efforts of electronic manufacturers to maintain a high level of quality assurance (QA). But as more and more manufacturers and integrated manufacturing services (IMS) providers are discovering, automated optical inspection (AOI) can bolster not only a company's QA programs but its manufacturing efficiency as well. As one global IMS provider in particular discovered, for customers demanding the highest quality from their IMS suppliers, especially for relatively low volumes of complex, densely packed, and sometimes large PCBs, AOI is the only viable QA option.

That IMS company is TT Electronics (Weybridge, Surrey, UK,, a global provider specializing in the production of low volume, high mix electronics built for the aerospace, defense, medical, industrial and rail industries. The company's investments in modern manufacturing equipment and their development and application of new technologies are based upon a deep understanding of the industry and their customers' needs. Advances in PCB technology and reductions in component sizes required TT Electronics to upgrade to an advanced AOI solution to maintain their high levels of QA. The latest AOI technology offers early detection of defect trends and generates the critical data required to make informed process decisions. By efficiently using the data generated by an AOI system, it is possible to identify manufacturing problems and not only improve product quality, but dramatically boost product yields and reduce manufacturing costs.

Unfortunately, manual inspection is no longer fast or reliable enough to handle the high packing densities, small component sizes, and high-throughput requirements of today's electronic manufacturing facilities. With short production runs and fast set-up times required, manual test strategies cannot be implemented quickly or cost-effectively enough. In contrast, AOI approaches offer rapid programming, high inspection reliability, and fast throughput. In fact, TT Electronics has been using AOI technology for more than 10 years in both its Rogerstone, Wales, UK and Perry, OH facilities. Within TT Electronics' business models, AOI technology provided the only means to achieve the high quality, coverage, and high throughput needed in their low-volume, high-mix manufacturing environments.

TT Electronics had always embraced advances in smaller components and more densely packed PCBs, but knew that their test solutions also had to keep pace. Upon embarking on a development and upgrade program, they realized the limitations of their existing AOI equipment, and in handling such miniature components as 0201 devices, the existing AOI equipment did not provide adequate resolution or throughput speed, and the false failure rate was running too high with these smaller components. TT Electronics' AOI equipment supplier at the time was unable to provide a solution, so other AOI suppliers were contacted for proposals based on TT Electronics' new, more demanding inspection requirements. After extensive evaluations of various systems, including paper evaluations and full-scale equipment trials, the FX Series AOI system from Nordson YESTECH was chosen. It proved to be the easiest system to program, and evaluation boards ran through inspection quickly and efficiently on a short production run.

At TT Electronics' Rogerstone facility, inspection takes place within a cellular architecture, in which output from four production lines can be directed through either of the two AOI cells. Since installation of the new FX Series AOI systems, 100 percent inspection has become more easily manageable, assisted by strategic use of holding areas to organize assemblies before and after inspection. The new AOI systems have provided clear benefits. The throughput rate has doubled, even with an increased number of checks being made. With their optical character recognition (OCR) capabilities, pattern matching, accuracy of component value capture, and recognition of manufacturers' logos, the new AOI systems have helped achieve new levels of fault-capture efficiency, while also reducing the number of false fails. They also provide reliable checking of board orientation.
The FX Series AOI system from Nordson YESTECH has helped TT Electronics improve its QA efforts and product throughput at more than one of its manufacturing facilities.

In addition to the improved optical resolution and accuracy, TT Electronics considers the reduction in false failure rate to be of critical importance. Previously, the facility experienced levels of around 50 to 100 false failures per board. With the new AOI systems in place, the false failures have been reduced to a level that complies with TT Electronic's manufacturing environment, with a related increase in productivity. Backed by local training and support from Nordson YESTECH, this has improved TT Electronic's productivity and quality, both by faster online throughput and by easier, faster offline programming and AOI system changeover between products. The offline programming capabilities have also contributed to improved productivity, by eliminating lost production time. The offline capabilities allow for a captured image to be transferred to an office personal computer (PC), where the inspection program can be configured. The complete package can then be transferred back to an online AOI system, ready for use subject to final checking.

Software Speeds Setups
Real-time data transmission and statistical process control (SPC) software monitors defect trends, and automated alarms help improve early warning capability, pointing manufacturing personnel toward the source of process excursions. For TT Electronics', their new AOI systems offer tremendous advantages in terms of programming. Compared to rules-based inspection systems, the new AOI systems, with Nordson YESTECH's image technology, offer easy programming. The systems use YESPC software for fast setup and customizable programming to meet q wide range of unique needs. The AOI programs can be configured by regular on-staff operators, rather than specialized software engineers, and typically require less than 60 minutes for setup.

These AOI systems avoid a rudimentary approach of programming from Gerber files, working with SIPLACE files that have been verified. These files are fed through a third-party converter which generates Nordson YESTECH-compatible instructions. The AOI software environment is based on Windows operating system (OS) software, for ease of development and deployment of new programs. The software compatibility supports reduced product changeover time. For a company such as TT Electronics, working in a low-volume environment with a large mix of products calling for frequent system changes, this reduced product changeover time contributed to increased throughput.

Of course, learning to use new AOI equipment takes time, and Bob Hannah, Operations Director at TT Electronics IMS, gives much credit to Nordson YESTECH for helping with the training: "The success of AOI as part of our quality infrastructure depends on our staff's skill in operating the equipment and making the most of its many features. We are delighted with the quality of the AOI system, as well as the training and support, and the untiring commitment, which we have received from Nordson YESTECH throughout TT's learning curve. As a result, we now have operators who are confident and effective in performing AOI inspection, and a near 100 percent uptime for our AOI facility."

Nordson YESTECH's President, Don Miller, adds his thoughts on the importance of AOI for improved QA: "Electronics manufacturers long have been driven to identify and control defects to improve quality and enhance yields. Implementation of AOI has proven to be a successful way to achieve these goals. By assessing AOI inspection goals and methods that best meet specific needs, manufacturers can realize measurable gains in both quality and overall yields while dramatically reducing costs. We are pleased that our FX Series AOI system is an effective and integral part of TT Electronics, QA program."

Contact: Nordson YESTECH, 2762 Loker Avenue West, Carlsbad, CA 92010 760-918-8471 fax: 760-918-8472 Web:

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