Hard disk drive assembly manufacturers are striving for increased memory capacity for hard disks, but they don't want to sacrifice reliability. Unfortunately, better technology has also brought an increased potential for contamination. Here's an overview of the major contamination issues facing hard disk drive assembly manufacturers.
- Erratic flight height. The "slider," or head, "flies" just microinches above the disk reading or writing data. Any material on the disk--such as dust particles--will interfere with the slider and change it's flight path. The result: errors in reading or writing data. "What to a person is a speck of dust, to this head is a skyscraper," says Arnold Toxen, consultant and Chair of the Terms and Definitions Committee of IDEMA's Microcontamination Committee. The severity of this problem increases as the hard drive industry strives to write data to disks in higher density because the slider will have to fly closer to the disk.
- Head crashes. Contamination on the disk will eventually cause corrosion of the magnetic layer. Due to the minute distance above the disk at which the head flies, the head will often crash into the corrosion product. Corrosion on the surface of the disk also causes interference that eventually leads to disk failure.
- Stiction. In many HDD assemblies, the read head comes to rest on the disk when the drive is turned off. The presence of certain organic materials on the disk may prevent the head from taking off again. Why? They're sticky. Some corrosion products can cause this stiction as well.