Circuits Assembly - January 2008 - (Page 24)

ESD Control Walking on Water By Pierre Husson High-pressure humidification systems can improve quality and reduce energy costs. S tatic electricity and the potential for defects due to ESD is one of the biggest manufacturing headaches a board manufacturer can face,” says Itron’s Paul Anderson. In snowy Minnesota winters, the potential for ESD problems soars as icy outside air is heated to normal plant operating temperatures of around 70°F. Without proper humidity control, relative humidity in Anderson’s plant could plunge, creating ideal conditions for ESD problems. Anderson is facilities operations manager for Itron Inc.’s 540-employee, 110,000 sq. ft. manufacturing plant in Waseca, MN, which produces RF devices and automated meter reading equipment used by utilities and large water and power users. Anderson has managed the facility’s operations since 1999 and has 25 years of facilities management experience. Every year Anderson and Itron’s plant engineers huddle to make sure everything is working right. A constant discussion item has been process improvements aimed at continuing to reduce ESD damage to components. The physics is simple: Static builds as RH levels drop – the colder the air, the greater the potential for dry air and static buildup. As cold winter air is heated, it dries and loses its capacity for carrying moisture. For instance, when outside air with a temperature of 10°F and RH of 50% is heated to an internal temperature of 70°F, RH will drop to about 10%. Industry standards recommend minimum RH levels of at least 30% to avoid ESD problems, with levels of 40-50% RH considered desirable. Keeping RH at an acceptable level requires most plants add large amounts of water to the air through humidification systems. In warmer, drier climes like California, ESD problems are often a year-round issue, and maintaining consistently appropriate RH levels may require adding water to plant air all year. “Keeping ESD problems at bay was a topic that occupied our attention every year,” Anderson explains. “For years we operated a compressed air humidification system throughout the plant. It did a good job, but as humidification technology has moved forward, so has the capability to control RH levels tighter and more consistently, meaning ever tighter control of ESD.” The compressed air humidification system lacked the precise control Anderson and Itron personnel sought. It also came with other annoying, costly baggage: • Inefficiency. “The moisture it produced didn’t cover the area as uniformly as we wanted. That’s a tough problem here, because we have ceiling heights as low as 11' and 12' in some parts of our manufacturing area.” • Expense. “Compressed air is a very expensive commodity, and operating the humidification system had just about eaten up our compressor capacity, so manufacturing couldn’t use it. Adding compressor capacity wasn’t an option. 24 Circuits Assembly JANUARY 2008 circuitsassembly.com http://circuitsassembly.com

Table of Contents Feed for the Digital Edition of Circuits Assembly - January 2008

Circuits Assembly - January 2008 Contents Caveat Lector Industry News Market Watch Talking Heads Focus on Business On the Forefront Screen Printing Better Manufacturing Walking on Water Flux Selection for Lead-Free Wave Soldering An A-to-Z Guide to X-Ray Inspection, Part II Evolution in Action Research Priorities for the Electronics Industry Selective Soldering Process Doctor Pb-Free Lessons Learned Materials World Product Spotlight Ad Index Assembly Insider Technical Abstracts

Circuits Assembly - January 2008

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