Two industry trends—the continuing miniaturization of electronic products and an increasing expectation that manufacturers share accountability for product warranties—have led United Technologies (UT) Automotive to develop a comprehensive static-control program that includes regular training, continuous monitoring, and failure analysis.
UT Automotive, a business unit of United Technologies, designs and manufactures electronic control systems for automotive companies. The Tampa, FL plant is one of 73 UT Automotive manufacturing sites worldwide and, until 1996, the company’s only plant in the United States making electronic products.
The Tampa facility supplies products to Ford, BMW, General Motors, Honda, Nissan, Rover, and Isuzu. Its major products provide automobiles with features such as remote keyless entry, automatic door locks, illuminated entry, memory mirror and memory seat, immobilization control, climate control, wiper control, and four-wheel-drive transfer-case control.
Growing Sensitivity to ESD
In 1991, the plant, which has operated in Tampa since 1979, doubled in size to 100,000 square feet. Two years later, the plant was confronted with two alarm bells:
A 20% in-factory failure rate in the conformal coating area.
An audit by a major customer and a resulting recommendation for increased static protection throughout the plant.
Both events reflected the same trend—increased sensitivity to electrostatic discharge (ESD). Managers realized that the increased failure rate coincided with production of a new component more sensitive to ESD than any of the plant’s previous products. The new device could be damaged by static discharges of 500 V or less.
At the time, the plant had a checkered static-control program. Some of the plant’s workstations had static-protective table mats, and employees used wrist straps while working at those locations. The plant also had a few static-protective tote boxes for transporting sensitive parts.
As a first step, the conformal coating area was revamped for better ESD protection. Static-protective floor mats and air ionizers were added, and workers began wearing heel grounding straps and wrist grounding straps. As a result, the product failure rate dropped to 0%. This turnaround increased appreciation for controlling ESD and created a willingness to learn more.
At this point, UT Automotive contacted 3M to conduct an ESD awareness seminar. After attending the in-plant seminar, managers recognized the need for a more comprehensive approach.
It was not merely a matter of installing protective equipment, but rather a thorough, well-designed plan that included education, auditing, verification, prevention, and corrective action as needed. Subsequently, the company enrolled as a 3M Preferred Customer and appointed a site ESD coordinator with authority to assess existing static control and implement an expanded program.
With 3M’s assistance, the ESD coordinator developed in-house static-control procedures and documentation for every stage of plant operations: inventory, assembly, testing, and shipping. One major provision was training for all employees, including managers and office personnel. This training has evolved to include an orientation class for new employees and retraining every two years for current employees.
As the new procedures went into effect, workstations were modified as necessary. Many were equipped with charge-draining floor mats and personnel heel grounding straps. In a few areas, benchtop ionized air blowers were added to neutralize static charge on nonconductive materials. When sensitive items were moved from one place to another, workers used static-protective tote boxes and shielding bags.
As the plant gained experience with static control, deficiencies in the program became apparent. First, workers could not be certain they always were grounded, even when wearing a wrist strap. They learned a wrist strap can fail intermittently because of a loose fit, overstretching, or dry skin. Second, many workers routinely walked back and forth across areas not covered by static-control floor mats, which increased static charges to unpredictable levels.
About the same time, the plant set its sights on achieving ISO 9000 certification. This process dovetailed well with ongoing efforts to strengthen static control and helped persuade management to embrace the concept of continuous monitoring. So in early 1996, all the plant’s more than 200 workstations were equipped with workstation monitors which instantly alert a worker if proper grounding is lost for either the wrist strap or the static-control mat.
Corporate Emphasis on Quality
In the meantime, the parent company, United Technologies, appointed Yuzuru Ito, former quality manager at Matsushita Electric in Japan, as special advisor on quality to the corporation’s six businesses. During the first two years, 1993-94, he concentrated on ailing plants in other UTC units. In 1995, he began consulting with the plants in the UT Automotive group. Because of management’s eagerness to work toward quality improvement, Mr. Ito chose the Tampa plant as the focus of his efforts.
Mr. Ito agreed with the ESD safeguards implemented at that time and strongly encouraged more refinements. Among these was a requirement that workers wear ESD-protective smocks and shoes. Work areas were arranged so that arriving employees used a special entry area to exchange street shoes for protective shoes and to put on smocks. In addition, employees periodically tested their shoes to make sure they still provided effective grounding.
Visitors to the plant are included in the program. They must wear conductive heel straps over their shoes.
The plant’s static-control coordinator began conducting quarterly and yearly audits of ESD equipment and procedures as part of the performance evaluation for each assembly line. 3M and a local supplier conduct two audits a year and annually verify the balance and charge decay of the more than 60 air ionizers in us throughout the plant.
Workers were encouraged to assume responsibility for identifying areas where static damage might occur. Ideas for effectively preventing ESD damage were publicized among the entire work force.
By late 1996, the static-control program entered a still higher phase. ESD-protective flooring was installed throughout the plant. As static control became an important part of daily procedures, creative ideas began to emerge for enhancing static protection beyond commercially available products.
For example, static-protective foam was cut to form dividers between electronics products stored or carried in tote boxes for physical as well as static protection. As another example, dust covers for conveyors and bins were made from static-protective sheet material to reduce dust as well as static buildup.
Failure Analysis Laboratory
One of Mr. Ito’s initial recommendations for quality improvement was an on-site failure analysis laboratory. Such a facility was in keeping with his philosophy of seeking out the root cause of defects and taking corrective action.
The lab, which opened in April 1996, not only investigates possible static damage, but also the robustness of design, assembly methods, and construction of components. This investigation may occur at any point in the manufacturing cycle: incoming components, in-house assembly, pre-shipped product, and warranty returns. Today, the lab performs 60 analyses a month.
A critical piece of equipment for identifying possible ESD damage is the scanning electron microscope, which can provide an optical inspection magnified up to 400,000 times. Technicians look for ESD damage, which typically manifests as a small circular melt through the edge of the gate oxide at the hot-spot location. Defects are photographed digitally to document findings.
Having an in-house lab enables the plant to identify various kinds of defects promptly and expedite corrective action. The speed and accuracy of the response also help improve communications on defect issues with suppliers and customers.
Results
In almost two years of operation, the lab has not identified any in-house failures attributable to ESD damage. By reducing static discharge and preventing the damage that might have occurred, UT Automotive has saved rework costs and improved yields. An even more important savings—and more difficult to calculate—is the cost of latent defects, the premature field failures of devices weakened by ESD during production. Such product returns are costly in terms of both repairs and customer satisfaction. Besides the dollars spent for analysis and replacement of individual units, too many returned products may well reduce next year’s warranty contract or lose it altogether. In addition, customers increasingly expect product manufacturers to share a portion of the warranty costs.
At UT Automotive, the comprehensive static-control program combined with other quality improvements has contributed to a growth in annual plant sales from $80 million in 1996 to $204 million (signed contracts) for the year 2000.
Static control also has played an important role in earning recognition from customers, including:
Ford Q-1 Award.
BMW A rating.
Nissan Motors Master Quality Award.
General Motors Supplier of the Year.
Honda Motors Quality Performance, Delivery Performance, and Supplier Quality Awards.
In November 1996, the plant was certified as an ISO-9002 quality design and manufacturing facility. In January 1997, it received the QS-9000 quality system registration required by the Big Three automotive makers.
About the Author
Scott Templeton is the quality methods manager responsible for the factory static-control program and the failure analysis laboratory at UT Automotive in Tampa. He has more than 19 years of experience in the electronics product manufacturing field, including 14 years with Texas Instruments before joining UT Automotive. Mr. Templeton holds a B.S.M.E. degree from the University of Tennessee. United Technologies Automotive, 5100 W. Waters Ave., Tampa, FL 33634, (813) 885-4785.
Copyright 1998 Nelson Publishing Inc.
February 1998