Spiral Defect Reduction of Hard Disk Drive Media

Abstract

The objective of this study is to reduce a number of defects in Hard Disk Drive (HDD) manufacturing due to spiral scratch on media by applying DMAIC steps of Six Sigma approach. The spiral scratch is firstly identified as the significant loss with 6.03% defective rate. Secondly, the paddle to disk space, top cover edge sharpness, pitch static attribute and number of load/unload cycle are found to be the key process input variables (KPIV). The experiment based on four KPIVs is then designed following Box Behnken design. With the results from the experiment, the response surface method is applied to determine the optimal setting for these four KPIVs with respect to the minimum percentage of the spiral scratch. Finally, the process with the optimal settings of the paddle to disk space at 3 mm, top cover edge sharpness at 0.002 inch, pitch static attitude at 0.01 inch and number of load/unload cycle at 10,000 times is implemented and monitored by the p control chart. After the improvement, the defective rate of the spiral scratch is decreased by 48.8% from 6.03% to 3.09%.