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When AOI Isn't Enough
Viscom AOI/AXI combination X7056.
By the Staff of Viscom

Zollner Elektronik AG is the only German company listed among the top 15 electronics manufacturing services (EMS) manufacturers worldwide. The services offered by this company range from the development of electronic products to after-sales services. Just as comprehensive as its services is the range of industries supported by Zollner — automotive and industrial electronics, medical technology, aviation, and aerospace, and telecommunications. To manufacture the most widely varying products effectively with high product quality and cost consciously, the equipment used in electronics assembly production must fulfill the company philosophy of innovative strength and flexibility.

Since its founding in 1965, Zollner has been family-owned. Today, it has 15 international locations and with more than 7,000 employees worldwide, the company offers system services for every phase of the product lifecycle. The company's range of services starts with customer-specific development through material and supply chain management, up to production and after-sales service. On average, it accounts for more than 2,600 NPIs annually.

Mission Critical Assemblies
Because of the mission-critical nature of many of the products coming down its production lines, 100 percent defect-free assembly must be guaranteed. This all adds up to rising demands on flexibility during production and the company's needs have outgrown its installed base of inspection equipment.

In this setting, a pure orthogonal AOI inspection has no chance. To detect potential defects, typically an X-ray inspection is used. Because the AOI still offers obvious advantages due to its speed, it makes sense to investigate whether an AOI with angled view is adequate. Thus, the strategy becomes as much AOI as possible, as much AXI as needed.

Therefore, those responsible at Zollner began a search for a new solution that would be suitable in both large volume in-line production as well as high-mix/low-volume. Uwe Schulze, responsible for AOI and AXI in the inspection technology area at Zollner, summarized this situation. "Our goal is to develop and produce faster, technologically superior and more flexibly than our market competitors. This results in giving our customers a clear competitive advantage," Schulze said. "Our equipment also must be capable of meeting this claim. The flexibility of the system was especially crucial for us because the different assemblies also necessitate different AOI and AXI test concepts."

Combined AOI/AXI
The company had been using X-ray inspection systems that had been designed exclusively for a pure 3-D X-ray inspection. When deployed for in-line production, this restriction to full surface 3-D AXI presented certain disadvantages. Schulze explains: "It doesn't always make sense to use 3-D X-ray for the entire assembly. The cycle time is shorter when an AOI is also used. Full surface 3-D X-ray inspection is very time-intensive and the x-ray systems needed for this are very expensive."

To raise the bar for its test coverage while solving this test dilemma, the company conducted an extensive evaluation of the inspection systems available on the market and decided to augment its existing AXI solutions with a Viscom X7056 inspection system. With this inspection system, it is now possible for the company to perform both AOI and AXI in just one system. This highly flexible inspection system finds visible as well as hidden defects quickly with a high level of reliability. The combination inspection system provides simple program setup and high throughput.

"Viscom systems make it possible to graduate the inspection by combining both AOI and AXI in one system," Schulze said. "The more we can inspect optically, the faster the entire inspection process. We have never had such flexibility before, and this provides us with a true advantage."

The heart of the X7056 X-ray technology is the high-capacity, microfocus X-ray tube from Viscom. It offers high performance — even heat sinks and shielding plates do not represent any obstruction — while it provides resolutions of 5, 7 or 10µm per pixel in the X-ray section. Depending on the application, 3-D, 2.5-D or 2-D X-ray technologies are used to achieve the highest inspection depth and shortest possible cycle times. In addition, due to the integration of the optical 8M sensor technology, the system offers the high inspection depth of the Viscom AOI systems with a comparable throughput. The OnDemandHR function offers the possibility to flexibly switch the resolution from 23.4 to 11.7µm/pixel with full image field size.

Complex Assemblies
Zollner uses the X7056 systems for complex assemblies and especially to inspect QFNs and BGAs. Although they appear simple to the casual glance, the exposed stamped edges of QFN components are considered to be a greater inspection challenge than the very stable standard BGAs. MicroBGAs with raster dimensions in the fine-pitch range also present serious inspection challenges. Schulze continues, "With AOI, such features as presence, displacement, polarity and solder quality can be checked. The AXI function is used to inspect not only where hidden menisci are only visible with difficulty, but also where taller components introduce shadowing."

Offline Programming
One important factor during the selection of an inspection system is the easy and speed with which the inspection program can be created. This is especially true where products change frequently, and it is essential that inspection programs can be created quickly and easily. The ability to operate two different types of inspection at the same time in one system provides a special advantage. "With our previous AXI system, the programming was difficult and hardly convenient." Schulze said. "But with the Viscom software, we have the same surface for both AOI and AXI. Therefore, the change between AOI and AXI is easy. This way, we are faster and more flexible." Despite the combination of cameras and X-ray tube, programming and inspection plan creation cost the operator no additional effort. The current CAD data and libraries remain completely compatible. Schulze continues, "What we really like is the possibility of offline programming. With the multi-picture image recording and video that the system provides. We can now accomplish up to 90 percent of our programming offline. This is a great advantage because the systems are inline and the entire production line no longer needs to be halted."

With this new combination system in place, specific assembly and program creation is faster and easier, and cycle times are significantly improved. The offline programming and intelligent inspection tools increase convenience during inspection. Schulze summarizes, "The absolute plus is definitely the combination of AOI and AXI. Through the full-fledged AOI, it is not only possible to determine information in addition to the AXI, such as polarity markings, barcode recognition, and component inscriptions, but also to completely inspect solder joints."

Contact: Viscom AG, Carl-Buderus-Str. 9-15, 30455 Hanover, Germany +49 511 94996-0 fax: +49 511 94996-900 E-mail: Web:

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