Reducing for High Track Density Hard Disk Drives

The windage is the flow-induced vibration of the head gimbal assembly (HGA) affecting head slider positioning in its off-track direction. Reducing the windage is important for increasing the track density of hard disk drives (HDDs). To develop HGAs that have a smaller windage than conventional ones, we examined the characteristics of windage. We used a 12-mm (from the swage hole center to the dimple) HGA that had a maximum windage peak of 11 kHz. To measure its windage, we set the HGA in a spin stand and in an HDD. The windage was measured with a laser Doppler vibrometer. The airflow velocity in the HDD was measured with a laser Doppler anemometer. The windage amplitude correlated well with the mean airflow velocity, indicating that windage amplitude drops with reducing airflow velocity. The fluctuation of airflow velocity had less effect to the windage amplitude. Our results show that expanding the distances between the rotating disk and the top cover and the bottom base is effective for reducing the windage.