Control for critical precision
The manufacture of a semiconductor chip is a meticulous process requiring absolute perfection at each of the 672 steps necessary from beginning to end. In the first phase of this process, silicon is heated to a molten liquid and a tiny bit of solid silicon, called a "seed", is placed into it. A small amount of the liquid rises with the seed and cools, forming an ingot of crystal.
This ingot is then ground to a uniform diameter and cut into very thin wafers. Each wafer is then processed through a series of machines, where it is ground smooth and chemically polished. All of this requires a precisely controlled manufacturing environment, including clean room indoor air quality with precise contaminant and humidity control. Not only does the process demand precision, but it’s also remarkably unforgiving. Uptime is of paramount importance as any interruption in the numerous steps results in a significant loss. Whereas most other manufacturing processes measure the cost of downtime in hours, the stakes are considerably higher at Samsung. They estimate that mere minutes of downtime would measure in the millions of dollars. "The factory must run 24/7 for 365 days of the year, without exception," says Kevin Judd, Master Facilities Technician for Samsung in Austin, Texas.
The first of the two buildings that make up the Samsung plant in Austin opened in 1996. When construction started in 2006 on the Austin complex’s second manufacturing facility, "FAB2", VLT® drive units were installed throughout the new 148600 m2 facility.
Currently there are about 150 VLT® drives in new and retrofit installations throughout the Texas Samsung factory complex. This includes drives ranging from 3.7 kW units installed on fuel pumps for backup diesel generators to 75 – 200 kW units utilized in the environmental control and automation applications throughout the manufacturing process.
VLT® frequency converters help to maintain the high indoor air quality necessary for the clean room environment that is so crucial to Samsung’s manufacturing reliability. The drives are used in normal and critical exhaust systems, cooling tower fans, pure water system pumps, positive pressure control systems to prevent contamination, and systems to remove fumes and gases from the acid scrubber process.
For Samsung, the use of variable frequency drives provides both efficiency and a higher level of control over their processes. "The variable frequency drives replaced numerous mechanical controls," explains Mr. Judd. "For example, in the environmental control of the clean rooms, positive pressure is required to keep contaminants out of the facility. The system was originally designed with fixed speed fans and mechanical dampers and vents. Now, variable speed control of the fans provides more accurate pressure control, reduced energy consumption and longer life expectancy of the fan motors.
It also eliminates mechanical control of the dampers and vents, reducing the maintenance requirements".
The decision to utilize VLT® drives in both new and retrofit applications at the Samsung facility was primarily based on the reliability that Samsung has experienced since the original VLT® units were installed in "FAB1". Since uptime is so crucial to their business, the ability of VLT® drives to ride through disturbances on the AC line was a significant advantage. The plant occasionally experienced voltage sags ranging from 30 to 70 % over a period of 6–10 cycles of the AC line. VLT® units proved to be superior in this area over competitive frequency converters. Other features that were of particular importance included user-friendliness, low harmonics, and operation in high ambient temperatures.
Dean Sniatecki, Facilities Technician, added, "in addition, we have found that the ability to perform online programming while the VLT® unit is in operation and the Hand-Off-Auto functions that allow for optimal operation without interrupting manufacturing processes have been a huge advantage".
More to come
Samsung is currently proceeding with bringing phase 2 of the new "FAB2" factory online, which will result in the full utilization of its 148,600 m2 of space. The construction of the "FAB2" facility has already been recognized for its accomplishments by garnering an award from Texas Construction Magazine. Phase 2 of the plant will utilize the latest technology in the VLT® product line, the VLT® AutomationDrive. Samsung was impressed with advancements in the VLT® AutomationDrive’s local control panel (LCP), as well as the new serial communication protocols offered, particularly Ethernet IP. Also of importance were the built-in fuses and disconnects, and the overall quality, reliability, built-in protection, and performance of the new product line.
Due to the demanding nature of semiconductor manufacturing, it was imperative that Samsung receive not only a reliable and technologically advanced product, but the expertise and responsiveness needed to support it, as well. And Danfoss delivered both.
