Automation

The importance of precise motion control

The downturn in 2001 hurt everyone in the semiconductor industry and the market has never returned to the giddy unrealistic heights of the dot com period. Dave Arguin of Kerk Motion Products discusses the impact these changes had on companies and industry as a whole. Using his own company as an example he discusses how other companies have had to change and become smarter to survive in a very different environment prior to 2000.

It may not be breaking news that the last five years have been somewhat of a roller coaster ride in the semiconductor industry – with an emphasis on downward motion.

According to a recent profile of the semiconductor industry, Yahoo Finance declared, "...the bottom dropped out [of the industry] in 2001 — and stayed dropped out through 2002 and much of 2003. By just about any measure, the decline was the sharpest in the history of the industry."

The profile blamed this bleak period on weak sales for all kinds of electronics gear; "from PCs to cell phones to networking equipment, [low sales] meant soft demand for the chips that make them work." While numbers were a little better for 2003, 2004 and slightly better still in 2005, the semiconductor's overall fiscal health is still struggling.

The point of this sobering economic outlook is no mystery: to remain competitive in the semiconductor industry, manufacturers must consider every possible way to maximize revenue and, perhaps more critically, to reduce expenses while improving quality. With profit margins already razor thin, keeping expenses as low as possible is a matter of corporate life and death.

While it may seem paradoxical, one viable way to save money would be to spend it. To its credit, the industry has never shied away from making sound investments, devoting an impressive $10 billion - 14 percent of sales – to the purchase of capital equipment. The key is to ensure that the equipment being purchased is not only sensibly priced, but also that it will translate to savings based on reduced downtime, lower maintenance costs, and improved throughput.

One of the best investments those in the semiconductor industry can make is in the field of precise motion control; certainly, there is ample evidence to support this contention. "Moore's Law," developed in 1965 by Gordon E. Moore, cofounder of Intel Corporation in 1968, predicted that the number of transistors the industry would be able to place on a computer chip would double every year. His prediction has proven to be incredibly accurate; consequently, each new generation of chip technology has driven the continual miniaturization of semiconductor process manufacturing. As this miniaturization continues, the need for better and more precise motion control becomes more essential.

Further evidence of this is found on the Future-fab website stating, "As semiconductor process technology approaches the theoretical limits of atomic physics, motion control solutions are becoming increasingly important to the design and performance of nextgeneration process tools and to the overall factory effectiveness (OFE) of the fab." Conversely, as precise motion control increases in importance, manual operator interaction with semiconductor tools becomes a less viable option because it introduces variables into a well controlled process. Any manual intervention cannot be performed with a high level of repeatability, and intervention can disturb the precisely controlled process and introduce foreign particles into the process.1

With the case for better motion control firmly established, the question of which system to use comes to the forefront. There are myriad assemblies that can be incorporated into any machine or system that is moving the product into, out of, or around the work area in a semiconductor manufacturing operation. While linear ways or ball slides have traditionally been the devices of choice to control this movement, there are now alternatives that offer comparable precision and efficiency. What's more, because they require far less maintenance, the alternatives can produce significant savings in the form of decreased operational downtime.

One of the most innovative devices now available for motion control in semiconductor manufacturing – in machines such as wire bonders, die bonders, magazine handlers, inspection equipment, dispensing systems, printers, and test handlers - is a "slide," which consists of a precision aluminum guide and carriage, driven by a precision rolled stainless steel leadscrew. These slides are available with a wear-compensating, anti-backlash driven carriage. Two rails can be used in parallel for a wider wheel base and additional driven or passive carriages can also be added.

More important than the slide's mechanical specifications are the cost-cutting benefits of the device. Ball slides require lubrication on a regular schedule, which is not only time-consuming but drives up the total cost of the manufacturing process. There are slides available that are selflubricating and thus require no lubrication throughout the life of the mechanism. This also makes them suitable for many wash-down environments.

Without the need for lubrication, another financial benefit is realized. Lubricants present a constant threat of work area contamination: if a device or part is lubricated, dust will be drawn to that product like a magnet. Ultimately, this can lead to increased wear and tear, which can diminish the life of the part and subsequently lead to increased downtime. As anyone connected to the semiconductor market can attest, "downtime" is dreaded in the industry. Semiconductor manufacturing is a high-volume exercise, and the ability to keep up with demand by maximizing operational uptime, tool utilization and efficiency – even when demand is sagging - is critical.

In this innovative, new slide, a lead screw drives the carriage, eliminating the need for a separate drive component. The lead screw is now captured within the slide, which, in turn, can be positioned to the side of the equipment rather than in the middle. The value of this design cannot be overstated, as the centre space is a key work area in many applications. Consequently, the machine designer is afforded greater flexibility to add features and accomplish tasks that would otherwise not be possible. Further, alignment concerns between the screw and guide are alleviated by the slide's integrated configuration.

With a performance that is comparable to ball slides in many ways, the slide is actually more economical - not just over the long-term with decreased downtime, but initially as well. Replacing traditional linear ways and a separate drive can represent a cost savings of about 50 percent.

Consider the savings that can be accrued when multiplied by the number of slide assemblies that might be used in a chip facility. In a given machine, anywhere from two to ten traditional assemblies may be utilized. Larger companies in the semiconductor marketplace may use as many as 1000 machines in their facility. A 50-percent cutback in parts costs over this number of machines will represent dramatic savings that can have a positive impact on a company's bottom-line profit.

The new, compact slide assembly is becoming a very popular alternative to linear ways, ball slides and square rails. As has already been seen in the medical and packaging markets, there is a place for it in the semiconductor industry. In fact, some 60 to 70 percent of all applications that are driving with a lead screw can use a slide as well, so the product's usage in the semiconductor industry is virtually limitless.