Absolute Imaging

Tape Stiction Overview
The word "stiction" was first coined during the mid 1970's to describe a critical tape/head condition that began to occur when the newer high speed tape drives were being introduced at that time. In effect, the computer tape that was manufactured prior to the mid-seventies was not completely compatible with the newer tape drives, and as a result, when certain conditions were present, the tapes would actually "stick" to the read-write heads, thus creating the term "stiction."

Its believed the cause is the effects of hydrolosis on certain specific types of computer tapes. The magnetic coating of half-inch computer tape is primarily a polyurethane-based binder system. All eurethane-based binder systems will experience hydrolosis when exposed to high humidity for an extended period of time. Hydrolosis is a reaction between the moisture in the air and the binder system, which results in degradation of the tape. Elevated temperatures will accelerate this reaction. Once the process of hydrolosis begins, the problem is further aggravated by the effects of tape tension and hug pressure. Typical drive rewind tension is about 11 to 13 ounces, and when combined with high storage temperature and humidity, acts to place excessive radial pressure on the tape surface, especially near the hub. This increased pressure can cause low molecular weight components within the magnetic coating (the by-products of hydrolosis) to exude, or be squeezed out to the tape surface. These components can then be transferred to the read-write heads during operation. During operation normal friction will develop at the point of head-to-tape interface, which produces a localized heating effect that facilitates the transfer of the tape components from the tape surface to the read-write head. Typically, no problems are encountered until the drive stops and these components have a chance to cool. The surface residue sometimes stays on the tape, sometimes transfers to the read-write head, and sometimes even bonds the tape to the read-write head.