QMT Features: May 2007
Manufacturing probe needles
Point Technologies Inc. uses an integrated vision system for 100% automated inspection, resulting in increased manufacturing efficiency

Point Technologies Inc., a supplier of precision electrochemical pointing and micro machining services and products for small diameter wire and tubing to the semiconductor, medical and biotech communities has recently applied motion and vision to a new area in the semiconductor industry: probe needle inspection.

By integrating Cognex machine vision with motion control in an automated needle inspection station, called PointScanTM, the design team created a system that inspects needles faster, provides more accurate measurements, requires less operator training, automatically documents each measurement, all while improving repeatability and providing feedback for process improvements.

Because probe needle geometry is vital for a successful wafer-level test operation, Point Technologies, formerly relied on a combination of manual video inspection systems and optical comparators to provide probe card manufacturers with needles that meet stringent requirements. However, as IC production volumes and demand for probe needles increased, it became obvious that this process was far too labour-intensive. Because needle inspection accounted for a significant proportion of the total manufacturing time, it was a prime candidate for automation.

Setting sights on automation

Up-front work was done to evaluate the feasibility of using a machine vision system to improve the measurement efficiency and still get repeatable measurements within 0.00002 inches. The team had little to no machine vision experience, but concluded that it made sense to start with an In-Sight vision sensor from Cognex owing to its ease of use and the fact that it arrives complete with user software.

“The In-Sight system required a minimal investment to allow us to prove that machine vision would work for our application,” explained Steve Neely, semiconductor division manager at Point Technologies. “We were able to set up a prototype system to prove the concept in four or five weeks.”

In-Sight is a high-performance machine vision sensor that consists of a DSP-based vision processing unit, high-speed digital camera, onboard light control, and built-in discrete I/O. It also provides a standard VGA output for real-time display, built-in Ethernet communications, and an onboard serial port.

“Without formal training classes, it took approximately 30 hours to get comfortable enough with In-Sight to set up the inspection routine,” says Neely. “By reviewing the tutorials that came with the system and using the on-phone technical support provided by Cognex, the team became familiar with the vision spreadsheet development environment, library of vision software tools, and the built-in operator interface.”

In-Sight proved to be a good validation tool; however it wasn’t the right product for the final application. The design team instead chose to specify a Cognex VisionPro PC-based vision system. Moving up to the VisionPro platform took a lot more time to learn, and required a couple of weeks of help from a Cognex certified vision integrator, but according to Neely, “It was well worth the investment because the vision code was used many times over in subsequent systems.”

One of the most challenging parts of any machine vision application is selecting the image formation system to produce a good image. After some lighting and optics experimentation, the team implemented a high-magnification telecentric lens that eliminates optical distortions and a 2x2 inch diffuse LED backlight to provide suitable images with the necessary resolution.

Vision meets motion

“Our engineers blended the vision, motion, operator interface, network communications, and database using Microsoft Visual Basic to manage all logic and control,” says Neely. “Vision-guided motion applications such as this one require a very fast vision system that will synchronize image capture, analysis, and measurement with the motion required to find the needle, focus the needle, and move from needle to needle.”

In all, the team was able to go from concept to working system in about six months. Since late 2004, five systems have been built and are being used in production. The systems are primarily used for measuring probe needles, but they are also used for measuring electro-surgery electrodes and other components for the medical device industry.

Significant reduction in inspection time

Machine vision has enabled the design team to create an inspection system where a computer does all of the inspection and most of the data analysis. Tests indicate more than a ten-fold reduction in inspection time. It used to take a person about 20 minutes to measure 12 needles and record the data on paper. PointScan measures 12 needles in less than 2 minutes, records the data, and automatically graphs out the data for the operator.

Machine vision has proven invaluable for accurately gauging very small parts and providing quantitative results that can be used to track parts, productivity, and to help troubleshoot inefficiencies in the process.

The data gathered by the vision system provides great insight into the production process. In fact, PointScan provides the feedback needed for operators and the quality team to successfully “re-model” systems and processes with more built-in improvements and efficiencies.

As a result, Point Technologies sees machine vision and motion control as key for the future of manufacturing. Integrating vision with motion is not as difficult as some would have you believe. However, it does take time, money, and expertise, but done right, even the most challenging applications can pay off.  l

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