INDUSTRY NEWS

Drive industry heads for showdown with microcontamination nemesis

With the advent of magnetoresistive (MR) head technology and increasingly lower flying heights, microcontamination has emerged as one of the disk drive industry's major concerns. Between 250 and 300 industry engineers and managers will tackle the crucial issue at a major symposium in Santa Clara, CA, on March 10. IDEMA, the trade association representing equipment and materials suppliers, is sponsoring the critical meeting.

Head-disk interface contamination and disk corrosion are among the topics of the March 10 IDEMA symposium. Photo Courtesy of Komag.

Topics such as head-disk interface (HDI) contamination, disk corrosion, and external contamination are on the agenda for the daylong symposium, which comes at a time when new types of failures and failure mechanisms are threatening the transition to drives with lower flying heights.

"Back in the old days when heads were flying at 10 µin. you could put a boulder in the drive and nothing would happen," says a half-joking Donald Perettie, who oversees standards committee and symposium operations as a member of IDEMA's board of directors. Today, with head heights lower than 1 µin., drive manufacturers and their suppliers are scrambling to develop ways of keeping contaminants from causing crashes and data loss.

The basic solution is improved particle control, says Perettie. There are at least two methods of ensuring the level of control needed, he adds. One is the use of either vapor-phase or polymer passivation coatings on drive components. Another solution is to use "more efficient filtration systems within the drive itself." A third concept—completely sealed drives—is impractical given the environmental stresses that a laptop's drive is likely to undergo in transit, for example, from the trunk of a cold car in Minneapolis to a warm airplane heading to Los Angeles, Perettie points out. Some manufacturers have developed a compromise, he says. It's a "semisealed drive with very good filtering systems made of porous polymer filters."

Perettie is the technical director for the disk drive materials business at Dow Chemicals. Dow sells a vapor-deposited passivation coating called Vitrinite. The product covers drive components with a 1-µm-thick coating. "It acts as a sealant to eliminate particle generation from components," says Perettie, who will be presenting a paper on the subject at the symposium.

The new types of failures caused by thermal asperities or by contaminants from the components within the drive can trigger random data loss. The contaminants can be dust particles or debris from the components, such as fine particles of aluminum oxide, Perettie says.

The problem is exacerbated by the nature of MR heads, notes Joan Pinder, IDEMA's executive director. "Because of the way they work, MR heads have a very thin stripe of magnetoresistive material that is very sensitive to magnetic flux in the disk. When it hits any kind of material it causes a high change in resistance, which in the head would look like a high signal change. . . . In the data stream you get these large spikes that come across as noise . . . of a very high amplitude that can corrupt data." Pinder adds: "An inductive head might just push the contaminant out of the way, go back and do a reread [of the disk]. In MR heads this corrupts the data stream."

Drive manufacturers working with MR technology are trying to develop software programs that would correct the misread by telling the computer, in effect, "Look for these kinds of properties. If you see this, ignore it, go back, and do a reread," Pinder says. "Of course, the best way to solve the problem is to try to keep the contamination out of there."

In addition to outgassing components and machined parts, workers are a prime source of contaminants, says Pinder. "People are always the worst offenders, so both the drive industry and the semiconductor industry are doing all they can in terms of cleanroom garments and filtration." The IDEMA executive also notes that drive manufacturers with plants in farming areas have had problems with fertilizer particles slipping past their cleanroom filtration systems. "Sulfurs from the fertilizers can actually grow particles."

IDEMA sponsors five to six symposia annually, and this one comes as the industry is in the midst of approving its first-ever set of microcontamination standards. Other topics to be addressed are cleaning techniques, cleanliness measurement methods, and cleanroom garments. Says Pinder of the meeting: "Certainly, microcontamination is a hot buzzword for the disk drive industry with the heads flying so much closer to the media. And with MR heads, thermal asperities and any kind of contamination in the drive are of concern. We're especially looking at where the contamination is coming from, how to test for it, how to prevent it, and the kind of filtration that might be needed."

The microcontamination symposium takes place at the Westin Hotel in Santa Clara, CA, on Tuesday, March 10. IDEMA may be reached at 408/720-9352; fax, 408/720-9380.

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