The X-ray Inspection Revolution
09/01/2002
ANNIVERSARY INSIGHTS
BY ALFRED REINHOLD AND LANCE SCOTT
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Pinpointing one pivotal advancement in X-ray inspection technology over the past decade is impossible given the many noteworthy innovations in recent years. During a time when the industries served by X-ray inspection have experienced sweeping changes, X-ray equipment manufacturers were presented a formidable challenge - how to address the changing needs of current markets while preparing for the needs of exciting new ones.
The advancement of X-ray inspection technology is, in a sense, determined by its users. What imaging capabilities are needed? What system features are essential? The essence of success lies in anticipating the needs of end users. This is accomplished most effectively through close cooperation with key industry leaders and by understanding their core technologies.
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User Input, New Applications
A decade ago, market leader feedback revealed numerous critical insights. The electronics industry's trend toward miniaturization was rapidly accelerating. Its commitment to smaller, faster and less expensive devices demanded more sophisticated, higher-resolution inspection solutions for quality assurance and ongoing development efforts. The transition to grid array components with hidden solder connections beneath the integrated circuit package further cemented this need, as did increasing circuit densities and the development of increasingly complex packages.
There also were early indications that new markets would require X-ray inspection - markets whose needs would mirror no existing customers' thus far. The emergent front of micromechanics - microelectromechanical systems (MEMS) and micro-optoelectromechanical systems (MOEMS) - presented new inspection challenges due to small structure sizes and unique material characteristics.
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MEMS/MOEMS integration into optical components and medical devices compounded the already challenging inspection requirements of these aggressively developing markets. Optoelectronics was in its infancy at the time, and it quickly became apparent that X-ray inspection would serve a vital role in the ongoing development of this fledgling industry as manufacturing technologies transitioned from the laboratory to the production floor.
Finally, there were potential applications for X-ray inspection that had never before been considered. Cutting edge biological and pharmacological research suggested that entirely new inspection techniques would continue to be demanded. Studies of biological specimens and micro-organisms would require contrast ratios, resolution and magnification far supe rior to most available X-ray capabilities.
In short, markets were changing, new ones were developing and different solutions were necessary for each. Manufacturers listened and understood that these changes in customer requirements would force us to test the boundaries of X-ray technology. Clearly, the results have been remarkable.
10 Years of Technological Leaps
While there have been many X-ray technology milestones achieved within the past decade, a few stand out from the rest. These breakthroughs have changed not only X-ray inspection technology, but also the respective industries served.
Focal Spot Sizes/X-ray Intensities: As an X-ray focal spot decreases in size, detail detectability and image resolution increase. Higher operating power generally leads to more brilliant, higher contrast images. Since the early investigations of scientists V.E. Cosslett and W. Nixon in the 1950s, it was widely accepted that microfocus X-ray focal spot sizes would meet a physical limit at approximately 1 µm at very low power levels. The relentless research and development (R&D) efforts of industry pioneers have now led to submicron focal spots that have challenged the previously accepted physical limits and encouraged the design of a new generation of nanofocus systems.
These new systems offer detail detectability as minute as a few hundred nanometers, with multiple watts of X-ray intensity. The results are precisely detailed images of even the densest samples with brilliant contrast distinction, yielding much greater feature recognition for R&D, quality assurance, and production pass/fail interpretation.
Imaging Chain Developments: The imaging chain is responsible for the detection, capture and presentation of the X-ray image to the operator. The past decade has witnessed dramatic advancements in high-resolution/high-contrast image intensifiers, charge-coupled device (CCD) cameras, fiber optics, amorphous silicon and amorphous selenium flat panel detectors, complementary metal-oxide semiconductor detectors, and other unique imaging solutions. Coupled with the previously stated focal spot and power enhancements, present day X-ray systems offer real-time digital images that meet or even exceed the quality of traditional film-based imaging.
Software Innovations: Advancements in computing technologies, software programming capabilities and microprocessors have allowed great improvements in system ease-of-use and functionality. Hardware and software work together to manage system operation, allowing the operator to concentrate on the resulting images and facilitating image interpretation through simple yet comprehensive image enhancement software. Similarly, system functions such as X-ray generation, sample manipulation and image interpretation are integrated seamlessly. More advanced software also enables detailed visualization including 3-D microcomputer tomography (µCT) imaging.
The Next 10 Years
All signs suggest that the next 10 years will prove as dynamic and innovative for the X-ray inspection industry as the last. Also like the last decade, X-ray inspection innovators will remain those companies that understand how to listen and respond to customer needs. The industries served will, in many ways, continue to dictate the fast pace and direction within our own market.
The optoelectronics and micromechanics industries, while having made immense strides in the past decade, are still young.
As they mature and are deployed more widely in various applications, inspection techniques will need to be adjusted. The majority of printed circuit board assemblies soon will include photonics, embedded components, 3-D stacked packages and even wafer-level packages - none of which can be inspected easily with conventional X-ray inspection systems. They will require greater resolution, 3-D visualization capability, automatic defect recognition and image interpretation, and increased speed and ease-of-use for the production environment.
The electronics industry will continue on its path of miniaturization. Likewise, those of us in the industry will be able to continue on our path of increasingly powerful X-ray inspection systems. Now that long-accepted physical barriers of technology have been proven surmountable, ongoing feasibility studies show that even smaller focal spot sizes and higher X-ray intensities are attainable. Continued advancements in software development and imaging chain solutions will make X-ray inspection even more effective for virtually any R&D, quality assurance, or production environment.
Due to the increasingly pervasive use of grid arrays, MEMS and optoelectronic devices - all of which are best inspected by high-resolution X-ray - we can predict that the market will recognize growth rates that meet or exceed the historical average of the semiconductor and related industries. Further, the industry's inherent cyclical fluctuations will be moderated by the increasing need for X-ray inspection solutions within nontraditional markets. The past 10 years have yielded impressive technological strides for the X-ray inspection industry, and the next decade promises the same vitality, with the same successful results for our customers and ourselves.
Alfred Reinhold, managing director of FeinFocus Röntgen-Systeme GmbH, may be contacted at Im Bahlbrink 11-13, D 30827 Garbsen, Germany; E-mail: [email protected]. Lance A. Scott, president of FeinFocus USA Inc. may be contacted at 76 Progress Dr., Stamford, CT 06902; E-mail: [email protected].
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