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    Reliability of PMN-PT piezoelectric material as an actuator for high density hard disk drive
    (2018-07-02)
    Wattananukulchai, Parinya
    ;
    Isarakorn, Don
    In the latest high-density hard disk drives (HDDs), the piezoelectric actuator of head gimbal assembly (HGA) is the key technology for precisely positioning the magnetic head. To increase HDD's areal density, a smaller track pitch and a faster spindle speed should be used but the faster the spindle rotates the larger the disturbance is. Hence, a newer PMN-PT piezoelectric actuator is needed to overcome the displacement bandwidth limitation restricted by the current PZT piezoelectric actuator. This paper investigated the reliability and performance of PMN-PT piezoelectric single crystal that was implemented on the a commercial HGA for the first time in an experiment. The objectives were to ensure that PMN-PT would not crack during the HDD assembly process and the performance of HDD equipped with this material was still reliable under thermal degradation. From the experiments on a prototype HGA, it was found that PMN-PT had a high degradation temperature of 150<sup>0</sup>C and was 2 times harder than PZT piezoelectric.
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    Performance evaluation using laser doppler vibrometer sensing technique on advanced lead magnesium niobate-lead titanate piezoelectric-material-based microactuator for hard drive head
    (2018-01-01)
    Wattananukulchai, Parinya
    ;
    Isarakorn, Don
    This paper presents a microactuator for a dual-stage actuator (DSA) of hard disk drive (HDD) based on a lead magnesium niobate-lead titanate (PMN-PT) piezoelectric material and a comparative evaluation of its performance versus that of a traditional lead zirconate titanate (PZT) microactuator using the laser Doppler vibrometer (LDV) sensing technique. PZT microactuator technology has commonly been implemented in the read/write (R/W) magnetic head of HDD. It has a significant function, that is, it moves the magnetic head rapidly and accurately. In order to achieve both accurate positioning control on data tracks and high-speed access across another data track, advanced high-performance actuators and servo control technologies are necessary. An actuator with a wide stroke travel range is essential for HDD as it gives a high-speed access performance. In this study, we focused on comparing the proposed dual-stage PMN-PT head-based actuator with the existing PZT actuator that were mounted on a commercial head gimbal assembly (HGA) using an LDV to determine whether the proposed device could be a worthy replacement of the traditional PZT microactuator. Our experimental results show that the proposed PMN-PT microactuator provided more than twofold improvement in the stroke travel of the R/W magnetic head. Moreover, its dynamic behavior was suitable for assembling a high-density HDD in the future for big data storage without any needs to redesign the HGA nor to costly invest in new assembling machines in a production line. The comparative data of dynamic and static behaviors of PMN-PT versus PZT obtained in this study may be put to good use by sensor designers. Moreover, for many cyber-physical system designers, our data may make them take interest in PMN-PT as a better-performing sensor and an actuator for their systems.
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    A solder bridging rework study and an experimental investigation of the TuMR magnetic head
    (2012-01-01)
    Roajanasiri, Reangroaj
    ;
    Afzulpurkar, Nitin
    ;
    Boonsang, Siridech
    The TuMR reader was designed with high sensitivity for high areal density magnetic recording in the hard disk drive. The assembly process requires the use of solder jet welding on small connectors in the head circuit. The solder bridging problem is the cause of the major mechanical yield loss. This work considers how to resolve the bridging problem without degrading the TuMR sensor by examining the use of Nd:YAG laser reheating. The use of double laser pulses yields better results than the use of single pulses. The critical parameters of the TuMR sensor are monitored with the Quasi tester. © IEICE 2012.