X-ray electronics inspection machine's innovative motion control is provided by versatile PCI card

The ground-breaking mouse-controlled positioning delivered by Dage’s new X-ray electronics inspection machines is handled by Baldor’s NextMove PCIbus motion controller card.

In order to provide revealing views of hidden solder joints on surface-mount printed-circuit boards (PCBs) - or internal views of the new generations of chip packages such as CSP and BGA - the card performs sophisticated correlations of up to five axes of movement in real-time. These allow the operator to orbit around an area of interest under the direction of simple hand movements. The motion controller translates these to three sets of synchronised motion that site the PCB or chip area of interest in the right position, while keeping it close against the X-ray source on one side and moving the imaging system as needed on the other.

Hardware costs were a major issue in the selection process, which the NextMove PCIbus card satisfied with its four axes of servo motor control, plus an add-on expansion module for the fifth axis. The onboard analog and digital I/O contributed further economy, providing enough inputs and outputs to handle all the associated machine control tasks - avoiding the need for any further modules in the form of PC cards or a PLC.

However, the determining factor in the choice of the motion controller was undoubtedly the capability of the associated Mint motion language, which Dage views as critical in delivering a predictable development cycle.

"Fast time to market is vital for a complex machine project like this", says Steve Ainsworth, Dage’s Engineering Manager, "and we look to the quality of the overall software development environment to minimise the risks involved. The Mint language and toolset is the best we have found, in this instance allowing the movement element of the control system to be developed in just over three months".
Dage's XL series X-ray machines are controlled by PCs. The NextMove motion controller card plugs into a PC’s PCIbus expansion slot, and works as a semi-autonomous subsystem. It receives double-click and click-and-drag requests to move to exact positions and/or perform controlled scans, and performs the real-time calculations and moves required to realise the positioning.

Programming these correlated and interpolated multi-axis movements was simplified by Mint’s large library of specialist keywords which make complex movements available as high-level commands. Dage utilise many of these in the new machine including SPLINE – which proved of particular value on this project as it effectively allowed the creation of custom movement profiles.

Dage had the option of using the Mint language in either its native interpreted form, or as a library of compatible 'C' language routines. It chose the latter for this particular machine project because of the computationally-intensive nature of the movements required. This approach allowed the final program to be made very compact and fast-executing, for use in the embedded system, providing the machine's operators with virtually immediate responses to positioning requests.

"The BASIC-style Mint language makes it very easy to get a prototype up and running quickly", adds Steve Ainsworth. "If you need higher execution speed, the software development environment then provides tools to transfer that code into 'C' - providing OEMs with a valuable range of options over the way that the Mint subsystem can operate in a machine, and the motion control performance that it can deliver".

BACKGROUND: THE XL SERIES OF X-RAY INSPECTION SYSTEMS
Designed for ease of use in a production environment, Dage's XL series of X-ray inspection systems deliver highly magnified, high resolution, all-around oblique-angle views of otherwise invisible solder bonds connecting array components to the printed circuit board (PCB) substrate. A straightforward 'point and click' software interface provides system control, enabling rapid inspection and analysis over areas up to 24 x 20-inches. Although the machines will find applications in the semiconductor industry, the XL series is primarily aimed at the PCB assembly sector where array packages are increasingly contributing to the higher density requirements of today's circuit boards. The new system enables manufacturers to check the integrity of terminations hidden beneath area array component packages, such as ball grid arrays (BGAs) and chip scale packages (CSPs), as well as those beneath flip-chip bare dice. Central to the ease-of-use and high productivity provided is the system's powerful software and its innovative hardware design. Interfacing with the system via colour LCD screen and mouse, the operator is able to rapidly select, display and retain the region of interest. The software provides full system control, including sample movement, data analysis and data output. The all-around oblique angle (0-45°) view of an array component presented is achieved by tilting the imaging system and not the sample, the latter remaining horizontal at all times. This design approach brings several benefits, not least the total avoidance of sample/imaging-system collisions. The approach also permits close imaging-system/board proximity which, in turn, facilitates the machines' high magnification specification of up to x2400.

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