INDUSTRY NEWS

Packed disk drive contamination meeting highlights cleaning, corrosion concerns

An overflow audience at IDEMA's most recent symposium on microcontamination control heard 12 colleagues present potential solutions for head-disk interface contamination, disk corrosion, and related problems facing the industry as it shifts to drives with lower flying heights. The morning session covered cleaning and characterization; the afternoon session, corrosion and control methods.

"Attendance was excellent. It was basically a full house," said a clearly pleased Tom Coughlin, the director of heads and media at Syquest and chairman of the symposium's afternoon session. Held March 10 in Santa Clara, CA, the all-day meeting attracted more than 240 people. "We were really excited about that number of people turning out for a focused symposium on microcontamination," said Seth Ayers, standards manager for the trade association representing equipment and materials manufacturers. A meeting held in August 1997 drew a packed house as well, he added.

Coughlin said "a big reason" for the high level of interest is the industry's shift to magnetoresistive (MR) head technology. "With MR heads you've got the whole issue of asperities as well as particulate contamination and corrosion. One of the biggest issues with MR heads in general is the spacing between the head and the media it's recording on."

During the afternoon session Charles Wang addressed the issue of corrosion properties on thin-film aluminum disks. Wang, a senior staff engineer at Western Digital, said the industry lacks a "standardized functional, drive-level test to quantify the corrosion on the disk surface." Manufacturers typically use environmental chambers to test disks in "high-temperature, high-humidity conditions for a certain length of time." Wang said the industry needs to develop "very sensitive monitoring tools" and quantitative techniques to monitor metal corrosion on the disks.

"We do have techniques such as SIMS, but they're not standardized," said the engineer, adding that there's no movement to standardize the use of SIMS because the technique is expensive and its use is not widespread. "What the industry does most of the time now is [conduct] a drive-level or component-level test to monitor the signal degradation of the recording head. Another approach is to visually inspect the disk surface with optical magnification." Wang would like to see a quantitative technique for better examination of corrosion problems.

The use of quantitative analytical techniques "is a sensitive topic" in the industry, noted Filippo Radicati, who followed Wang. Radicati presented a paper on the application of time-of-flight (TOF) SIMS in the study of disk drive contamination issues. The senior scientist at Quantum said TOF-SIMS is able to recognize molecular structures not possible with Auger spectroscopy analysis, offers imaging capabilities that are complementary to techniques such as electron spectroscopy for chemical analysis (ESCA), and in general provides a higher sensitivity than either of these two analytical methods.

TOF-SIMS "is clearly a laboratory technique. . . particularly useful for failure analysis," explained Radicati. The method has been used "heavily for the past six or seven years in failure analysis as well as in more theoretical analysis...The next big area of use would be the application of this technique in conjunction with others for the control of airborne molecular contamination. It's now used mostly in a failure analysis mode to detect contaminants present on surfaces. At the moment it does not have a great deal of quantitative capability."

Radicati said TOF-SIMS has been combined with techniques such as surface acoustic wave (SAW) detection. "One can essentially use the SAW part to measure total loads of airborne molecular contamination and then the TOF-SIMS half of the technique to actually determine what species are present. The two techniques together offer a synergy."

Ten ballots have been issued by IDEMA's microcontamination committee for voting on the industry's first-ever set of standards dealing with the issue. Five proposals address terms and definitions, and five address test methodologies. Information: 408/330-8109.

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