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Recalibrating equipment improves placement yields.

Something wasn't quite right at Phoenix International, and although the engineers knew it, they couldn't quite put their fingers on the cause. It had to do with the pick-and-place equipment. Some components weren't where they should be, or were skewed or missing, even though the machines had been programmed correctly for each product. This meant defects. A bit of rework is expected, but this was too much, and the engineers began to suspect that it was because of more than just mechanical imprecision.

Phoenix International develops rugged electronics components and systems for industries that rely on the equipment to function under the most adverse conditions – industries such as on-highway, agriculture, heavy construction, industrial control, material handling and more. In 1999, Deere & Co. purchased Phoenix International.

The manufacturing environment is high-mix, low volume, with four SMT lines and one module line. The products are primarily SMT assemblies, and one production line is dedicated Pb-free.

Because Phoenix International is high-mix, there is much setup and changeover on the machines, and no opportunity to optimize the equipment. The product mix changes quickly. The approach, then, is to have the process perform on a high level and then have the products conform to that process, instead of modifying the process to conform to the product.

Problems with a rising rate of defect levels developed gradually. Emerging difficulties were primarily in the pick-and-place area. They included off-pad issues related to nozzles and head calibration issues.

The most common problems found on the chipshooter equipment, for example, were systematic offsets (80%). These included offsets per head, per nozzle, per angle or simply a general offset. Offsets negatively affect chipshooter accuracy, resulting in PCB defects, lower yields and manual rework.

As a test, Phoenix International recalibrated one particular machine with the help of CeTaQ Americas (cetaq-americas.com), which provides equipment and services for production machine process capability analysis. CeTaQ uses specialized technology to analyze machine capability, checking the basic settings and functions (in the case of placement equipment, this includes clamping, sensors, nozzles, camera, feeders, and more) to identify, control and correct failures, so that the machine can assemble product within the original quality specifications established by its manufacturer.

CeTaQ performs capability analysis using this machine and testing technology. The machine uses special vision algorithms, highly accurate glass plates and components to provide independent measurement of Cp and Cpk indices on production equipment. Proprietary software operates the measurement equipment and provides statistical specification-based results on machine quality performance. Comprehensive certification reports validate performance.

Before working with CeTaQ, Phoenix did not know whether its machines were performing to specification. In fact, they weren't: All the machines failed CeTaQ's initial specification check in 2003.

The first time CeTaQ tested the machines, the process was slowly getting out of control (Figure 1). Much time was spent examining the placement machines to analyze the root of the offset problems. Was it the software? Did settings need to be changed? The tests revealed nozzles in wrong locations, and heads that were out in no-man's land (Figures 2 and 3). Previously, the averages suggested the equipment was operating within its specified tolerances. The CeTaq analysis broke the equipment down per head, and revealed certain heads simply were not functioning correctly. As a result, a number of heads were8replaced Ð three last year on one older machine alone.

Correcting placement machine problems had a dramatic effect on defect levels and improved yields (Figure 4). Placement rates improved, and the net result was that the machines have performed better (Figure 5).

Phoenix International does not have the capability to go into the machines and interface on the machine level to implement recommendations generated by the analysis; generally when this is done, CeTaQ and the equipment manufacturer are present. CeTaQ generates the analysis and report, and the OEM's service personnel implement the fix.

From the initial work, it was discovered that this type of testing was something needed annually because there may be a difference between what the machine is reporting and what it is actually doing. Phoenix has its machines tested regularly, which reveals areas in need of special focus and overall trends. Then, performance is broken down into different areas. Parts may be replaced; for example, movable rails and pillow blocks might be grouped into an individual program maintenance schedule for replacement even before the scheduled test. Then, once the machine is tuned, it will perform flawlessly for the next 12 months.

Kary Voegele is senior process engineer at Phoenix International (phoeintl.com); kvoegele@phoeintl.com.