Patent Publication Number: US-2003223154-A1

Title: Method for encapsulation of a U shape micro-actuator

Description:
BACKGROUND INFORMATION  
       [0001] The present invention relates to magnetic hard disk drives. More specifically, the present invention relates to a method of preventing particle generation by the actuator of the hard disk drive.  
       [0002] In the art today, different methods are utilized to improve recording density of hard disk drives. FIG. 1 provides an illustration of a typical drive arm configured to read from and write to a magnetic hard disk. Typically, voice-coil motors (VCM)  102  are used for controlling a hard drive&#39;s arm  104  motion across a magnetic hard disk  106 . Because of the inherent tolerance (dynamic play) that exists in the placement of a recording head  108  by a VCM  102  alone, micro-actuators  110  are now being utilized to ‘fine-tune’ head  108  placement. A VCM  102  is utilized for course adjustment and the micro-actuator then corrects the placement on a much smaller scale to compensate for the VCM&#39;s  102  (with the arm  104 ) tolerance. This enables a smaller recordable track width, increasing the ‘tracks per inch’ (TPI) value of the hard drive (increased drive density).  
       [0003]FIG. 2 provides an illustration of a micro-actuator as used in the art. Typically, a slider  202  (containing a read/write magnetic head; not shown) is utilized for maintaining a prescribed flying height above the disk surface  106  (See FIG. 1). Micro-actuators may have flexible beams  204  connecting a support device  206  to a slider containment unit  208  enabling slider  202  motion independent of the drive arm  104  (See FIG. 1). An electromagnetic assembly or an electromagnetic/ferromagnetic assembly (not shown) may be utilized to provide minute adjustments in orientation/location of the slider/head  202  with respect to the arm  104  (See FIG. 1).  
       [0004] The slider may be bonded with a ‘U’ shaped micro-actuator. The ‘U’-shaped micro-actuator may have a piezoelectric Lead Zirconate Titanate (PZT) beam (arm) on each side of a Zirconia support frame (actuator base). During excitation of the PZT, the PZT beam will deform, further causing the Zirconia support frame to deform. Since the PZT is an anisotropic structure, meaning the Weiss domains will increase the alignment proportionally, and since the top surface of the PZT is a soft, electric material (i.e., gold or platinum), the PZT does not generate any particles during this deformation. However, as the Zirconia support frame is a hard material lacking the Weiss domain properties, the inner force present during deformation generates particles. Particle generation is particularly heavy on the inside surface of the ‘U’ shaped micro-actuator where the interior forces are strongest. Particles generated on the ‘U’ shaped micro-actuator may interfere with the operation of the actuator. Additionally, these particles may be deposited on the magnetic disk surface, interfering with read/write operations. Also, the particles eventually cause damage to the micro-actuator arm as the hard drive ages. Further, since both arms of the “U” shape micro-actuator support the head, the arm may be broken due to shock or vibration. It is therefore desirable to decrease the amount of particle generation caused by the Zirconia support frame.  
     
    
    
     BRIEF DESCRIPTION Of The DRAWINGS  
     [0005]FIG. 1 provides an illustration of a drive arm configured to read from and write to a magnetic hard disk as used in the art.  
     [0006]FIG. 2 provides an illustration of a micro-actuator as used in the art.  
     [0007]FIG. 3 describes a hard disk drive head gimbal assembly (HGA) with a ‘U’-shaped micro-actuator under principles of the present invention.  
     [0008]FIG. 4 provides an illustration of a U shape micro-actuator design.  
     [0009]FIG. 5 provides an illustration of the U shape micro-actuator bending with slider.  
     [0010]FIG. 6 provides an illustration of an encapsulated U shape micro-actuator.  
    
    
     DETAILED DESCRIPTION  
     [0011] A system and method for preventing particle generation by the micro-actuator during deformation by partially encapsulating the micro-actuator with a coating is disclosed. In one embodiment, the coating, made of a soft and tenacious material, is applied to the rigid areas of the micro-actuator.  
     [0012] Illustrated in an upside-down orientation, FIG. 3 describes one embodiment of a hard disk drive head gimbal assembly (HGA) with a ‘U’-shaped micro-actuator. In one embodiment, a slider  302  is bonded at two points  304  to a ‘U’-shaped micro-actuator  306 . In a further embodiment, the ‘U’-shaped micro-actuator has a piezoelectric Lead Zirconate Titanate (PZT) beam (arm)  308  on each side of a Zirconia support frame (actuator base)  310 . The micro-actuator  306  is coupled to a suspension  312 .  
     [0013]FIG. 4 illustrates one embodiment of the ‘U’ shaped micro-actuator  306 . A support frame  310  supports two piezoelectric Lead Zirconate Titanate (PZT) beams  308 . In one embodiment, the support frame is Zirconia. While the PZT beams cover the exterior sides of each of the two arms of the ‘U’ shaped micro-actuator  306 , the Zirconia support frames on the interior sides of the arms are exposed.  
     [0014]FIG. 5 illustrates the interaction between the ‘U’ shaped micro-actuator  306  and a slider  302 . As the micro-actuator drives the slider, the arms of the micro-actuator deform. Because the PZT beams are anisotropic structures and the top surfaces of the PZT beams are typically a soft, electric material (i.e., gold or platinum), particle generation by the PZT beam is not sufficient to be problematic. However, the support frame is typically made of a rigid material and does not have the proper Weiss domain properties to reduce particle generation. The deformation of the arms of the micro-actuator causes the support frame to generate particles along the exposed interior of the arms  502 .  
     [0015] In one embodiment of the present invention, an encapsulation coating is applied to the ‘U’ shaped micro-actuator to prevent particle generation. FIG. 6 illustrates an example of a partially encapsulated ‘U’ shaped micro-actuator. According to an embodiment of the present invention, to avoid affecting the performance of the micro-actuator, the encapsulation coating  602  only partially covers the micro-actuator  306 . In one embodiment, the encapsulation covers the exposed support frame  310  on the interior side of the arms. In a further embodiment, the encapsulation coating is made of a soft and tenacious material, such as gold, platinum, epoxy resin, etc. The encapsulation coating can be applied to the support frame  310  with any of a variety of techniques including printing, spraying, sputtering, electric plating, electricless plating, or chemical vapor deposition. Other methods may also be used to apply the coating. In one embodiment, the coating operation occurs before the PZT arms are coupled to the support frame.  
     [0016] The encapsulation coating can increase the shock performance of the “U” shape micro-actuator. Such shocks include a tilt drop shock or a crash-stop shock during a head seek. The particle encapsulated method can increase the shock stiffness of the arms of the “U” shape micro-actuator and thereby improve shock performance.  
     [0017] Although several embodiments are specifically illustrated and described herein, it will be appreciated that modifications and variations of the present invention are covered by the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.