Transfer film formation on helical scan data recording heads

The increasing demand for high density media requires decreasing the head-to-tape gap and reduction the track width. A problem very often encountered is the development of transfer film (stain) on the heads leading to an increase of space between the head and media, hence a decrease in the playback signal and increase in error rate. In this study, the development of transfer film on DDS3 (digital data storage) drives using DDS2 metal particulate tapes is investigated under several environmental conditions using the AFM microscope. The influence of stains on the playback signal of reading heads is studied using read after write tests and their influence on the wear of the heads by using indentation technique. The results confirm previous studies that stains appear and develop under low humidity conditions whereas at high humidity they tend to disappear. The stains are usually in between 10 and 20 nm in height but occasionally they can grow up to 40 nm. The playback signal has been found to vary and the errors to increase as stains form a patchy pattern and grow in size to form a continuous layer. The indentation technique shows that stains reduce the wear rate of the heads. In addition, the wear tends to be more pronounced at the leading edge of the head compared to the trailing one. This behaviour can be explained if one takes into account the chemical changes that occur on the tape and head side at different environmental conditions. Chemical analysis of the stains and ferrite poles previously performed (Nastasa and Sullivan, in press) clearly shows presence of the binder within stain formulation. The stability of the binder under high humidity and under high temperature (Nakamae et al., Int. J. Adhesion Adhesives 1996;16;277–280) as well as the chemical reactions that might occur on the ferrite poles of the heads influences the dynamic behaviour of stains.