Effect of Mechanical Parameters for Loading Contact and Instability in HDD

Abstract

Ramp load/unload (L/UL) technology becomes core technology in mobile hard disk drive (HDD) because it enables higher areal density and stronger shock robustness. However, ramp L/UL has some instability because of the structural limit that a head should repeatedly move between a ramp and a disk. Among much instability, the slider-disk contact generated during L/UL process mainly affects the drive reliability. In particular, the slider-disk contact during the loading process has a critical effect on head-disk interface (HDI) failure due to difference of impact force by much higher height level despite of low frequency. Therefore, this paper mainly focused on the loading contact and instability. At first, we defined the loading contact, scratch and instability generated by the slider-disk contact. To do so, we verified the contact location considering the interaction of the air bearing surface (ABS) and the disk, and we analyzed the relations for the loading contact between the ABS and the slider motions. After definition for the loading contact and instability, we evaluated the effects of the head stack assembly (HSA) height, the ramp height and the disk height based on the ABS performance. The relations among the HSA, ramp, and disk height affected the main parameters related to the loading contact and instability such as the Z-height, the pitch/roll slider attitude, and the gramload. We focused on the effect of the mechanical parameters according to the loading contact and instability. Finally, we measured the height differences for passed and failed drive samples. We could find out how the height differences cause the loading contact and instability through the relation among mechanical parameters such as the height of the HSA, the ramp and the disk. Based on these results, this paper proposed that the mechanical parameters such as the height relations should also be considered in order to avoid the loading contact and instability and to improve the loading performance.