During product development some Hewlett-Packard DDS tape drives experienced
a gradual increase in their uncorrected error rate when running a particul
ar operating test at low humidity. This was known as 'error rate drift'. A
combination of system-level testing, signal processing, and atomic force mi
croscopy showed that the degradation was caused by contamination on the sur
face of the heads. The 'stain' thickness increased each time tape was reuse
d, resulting in progressive attenuation of the readback signal amplitude. U
sing time-of-flight secondary ion mass spectroscopy the contaminant was ide
ntified as inorganic Fe, Si and Al, transferred from the media. (C) 1999 El
sevier Science Ltd. All rights reserved.