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Publication Date: 05/1/2008
Archive >  May 2008 Issue >  Special Feature: Test and Measurement > 

Cost-Effective 3D X-Ray Inspection
Revolution X-ray inspection system.

In the fast-moving and highly competitive electronics manufacturing market, long term survival increasingly depends on developing relationships with customers and establishing a basis for repeat business. As a result, the ability to gain a reputation as a reliable and trustworthy supplier through the continual delivery of defect-free products has never been more important.

Customers are also becoming increasingly price-sensitive, so gaining cost advantages through reduced waste while using competitively priced machinery is imperative. In response to this need, X-Tek, manufacturer of real-time microfocus X-ray inspection equipment and recently acquired by Metris, has introduced the XT V160 Inspection System, also known as the "Revolution".

A fundamental part of X-ray inspection is the ability to view a product from different angles. Further, identification of product defects depends on the magnification the inspection equipment can offer. And to increase the likelihood of identifying product defects, inspection images need to be of the highest possible resolution.

Meeting all of these requirements, the smaller footprint and lower price micro-focus X-ray inspection system from X-Tek provides the highest resolution and magnification possible within a compact system for quality control, research and failure analysis. With the ability to inspect substrates at steep angles of up to 75°, it is designed for 100 percent BGA and µBGA inspection, multilayer board inspection and PCB solder joint inspection in production lines and failure analysis laboratories in many manufacturing areas.

True Concentric Imaging
The XT V160 uses true concentric imaging that enables the operator to choose a Region of Interest (ROI) to inspect, which is then positioned in the center of the screen. To stay focused on this region, the X-ray source and detector rotate, rather than the product. The Region of Interest therefore remains completely locked into the center of the field of view under any combination of rotate, tilt and magnification, regardless of the sample's position on the manipulator table. A further positioning feature is provided to view the region from any rotation (360° continuous freedom) and tilt angle of up to 75°. The XT V160 is therefore able to inspect around single or multiple BGA balls as the true concentric imaging feature operates over the entire scan area of the manipulator. Inspecting the rows of BGA balls is also less labor intensive than with standard manipulators as the XT V160's true parallel tracking maintains the X and Y axes parallel to the BGA. This allows the rows to be scanned using a single X or Y axis instead of requiring the simultaneous operation of 3 axes.
X-ray of ball-grid array.

If a sample is to be declared defect-free, internal structures also require thorough inspection. The XT V160 employs Computed Tomography (CT) which is the process of imaging an object from many different directions using penetrating radiation and a computer to calculate the interior structure of that object from the images. Many industries make use of CT including electronics, aviation, medical, advanced materials research, casting and a host of other manufacturing areas. The CT function allows the complete structure of an object to be stored and examined to give a reading of all internal dimensions and the precise size, shape and location of any internal feature or defect. The CT system can be upgraded for real 3D analysis of components. The upgrade simply plugs into the existing manipulator controller without the need for future re-wiring or other modifications.

Finding Product Defects
Identification of product defects depends on the magnification the inspection equipment can offer. The transmission target design fitted to the XT V160's X-Ray source has an ultra thin output window that enables samples to be safely placed within 250µ of the focal spot providing up to 13000x system magnification at all angles over the entire 410 x 410mm manipulator scan area. This facilitates 100 percent BGA, µBGA, multilayer board and PCB solder joint inspection, with quick analysis of BGA ball wetting, attachment, cracks and delaminations.

In addition, the patented X-Tek Xi "Open Tube" X-ray source is smaller than any other design and allows X-ray images of fine detail in thick and dense samples to be seen with ease. This high energy vacuum de-mountable unit enables views at steep angles through solder joints and heatsinks without ever running out of energy. Another attribute of this technology is the combination of the vacuum tube and the voltage generator. This has resulted in increased reliability and reduced maintenance costs as the extra charges typically associated with servicing separate voltage generators, cables and connections are avoided.
Inspecting PC board on sample tray.

To increase the likelihood of identifying product defects, inspection images need to be of the highest possible resolution. The XT V160 employs a tightly controlled microfocus X-ray spot and the latest digital imaging technology including a NanoTech target capable of feature recognition to approximately 500nM. The advanced electromagnetic lens is computer-controlled to ensure that the image remains in focus at all kV settings and the target does not burn when using high power. This enables the production of sharp images of micron level features of even the most challenging substrates.

Inspecting PC Boards
The photography equipment incorporates a dual field image intensifier with a digital camera. This combination (Impix) provides a large field of view, high sensitivity and high dynamic range (16 bit image processing). Combined with the On Chip Integration (OCI) feature, this equipment allows the user to take advantage of low energy X-ray photons for imaging low density features such as aluminum bond wires, thin copper traces, epoxy voids and more. This is achieved by a very sensitive image intensifier and by gating the digital camera to accumulate a greater signal.

The production of high resolution images is supported by Inspect-X, an advanced image capture and analysis software with special functions for inspection of semiconductor package voids, wire bonding and BGA solder bumps. Inspect-X runs under Windows XP Pro on the latest specification processing hardware which enables the resulting data to be saved or exported directly to any COM compliant package, such as MS Word, Excel, Access and SPC systems. A range of inkjet, laser or thermal printers can then be used to produce photo quality printouts. Inspect-X allows rapid software customization to suit specific inspection requirements and has been designed to enable quick transfer and sharing of information so that anyone can open and view the information from their PCs.
CT reconstruction of ball-grid array.

The need for user-friendly and flexible equipment in inspection requires common technology and platforms that are best suited for the purpose. The XT V160 is a versatile tool that allows an operator to easily make use of the system's manual and programmable inspection capabilities. The Windows control screen is laid out logically with all regularly used functions in view on single click buttons. Joysticks are also provided for very fine positioning and control to enable a direct and logical response from both sample manipulator and X-ray images. This enables operators to pick up on even the most demanding defects.

Inspection equipment should be designed for ease of use without compromising performance. To meet this need, the XT V160 provides advanced viewing capabilities including dual monitors that separate images from the software control and the Quad View that allows 4 images to be displayed at once. This process is useful for image comparison or reference for operators. The XT V160 is highly intuitive to operate and as a result, operator training time is significantly reduced. In addition, the XT V160 features advanced ergonomics including fully adjustable shelves that ensure all system controls are at the operator's fingertips whether standing or sitting and irrespective of the person's height.

During the inspection process of the manufacturing line there is a high risk of samples being damaged by static as sample trays are often made of anodized aluminum which is not ESD safe. To ensure this is avoided, the XT V160 has a carbon fiber static dissipative sample tray with an ESD-safe side control desk and an additional ESD clip in point. With the ESD control desk there is no need to worry about placing a sample on a work desk and risk static damage.

Contact: Metris USA, Inc., 12701 Grand River, Brighton, MI 48116 810-220-4360 fax: 810-220-4300 Web:

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