Bit Error Rate Improvement of Hard Disk Drive

Abstract

The objective of this research is to improve the performance of the read-write head process in Hard disk drive manufacturing with respect to Bit Error Rate (BER). With the preliminary survey, the process capability index (Cpk) of BER was 0.72 which is less than the one side acceptable value at 1.25. To improve Cpk of BER, five phases of Six sigma approach are applied starting from define, measure, analyze, improvement and control phases. At 95% confidence, thermal protrusion, writing current amplitude, writing current overshoot, number of defects on media and writing head width are the significant factors for Bit Error Rate due to their p-value less than 0.05. Since the number of defects and writing head width are uncontrollable factors, the experiment are designed and performed based of general factorial design with three levels of each controllable factor. At 5% significance level, there are the interaction effects between the thermal protrusion and the writing current amplitude as well as the interaction affects between the writing current amplitude and the writing current overshoot. With the general linear model (GLM), the suggested values for the thermal protrusion, writing current amplitude and writing current overshoot are 35 DAC, 10 mA and 9 mA, respectively. Under the suggested condition, Cpk of BER is increased from 0.72 to 2.38 and the percentage of defective due to head related failure is reduced from 21.85% to 9.86%.