Process Improvement to Reduce Defects from Magnetic Reader Resistance Failure in Hard Disk Drive

This paper illustrates an application of the FMEA method to study and analyze the defect causes in order to reduce the defects from failure of the magnetic reader head used in the 3.5-inch desktop hard disk drive assembly process. The failure ratio of 11.27% was observed at the hard disk drive assembly operation. The solution approach started from identifying sub-processes, where the PCBA Assembly Process became the focus of the analysis since it presented the highest failure ratio among sub-processes. Experts were invited to be the FMEA team. Brainstorming, discussion and analyses indicated that the top three causes of failure arose from: the contact and separation events which induced electrostatic on PCBA, the change of material and packing of PCBA leading to an increase in sensitivity to electrostatic discharge, and the new design process which impacted the head resistance to electrostatic stress. The two actions to address these causes were experimented. The first solution was to implement a new process incorporating the prevention of contact and separation events, creating controlled document, and deionizing electrostatic discharge on PCBA before assembling to the hard disk drive. The second solution was to redesign magnetic reader head to enhance the resistance on electrostatic discharge flow and to improve head performance. The experimental results showed that each solution could reduce the failure rate to 1.67% and 5.33%, respectively, and the combined solutions could decrease the failure rate to 1.33%.