Abstract:
Amplifier chips for heads in a disk drive are interspaced adjacent to junctions between actuator arms and suspension arms that hold the heads. This allows decreased spacing between plural disks in the drive system and accelerated data rates. This also decreases assembly steps and damage to the chips as they are further removed from mechanical processes such as swaging that attach the suspension arms to the actuator arms. Damage to the disks or chips during operation is also averted, as the chips are removed from each other and from the rapidly spinning disk surfaces with which the suspension arms and heads are proximate. The interspacing can also improve performance characteristics of the preamplifier chips, which do not need to be made as thin in order to fit between disks, decreasing costs and problems such as overheating of the chips.

Description:
TECHNICAL FIELD 
     The present invention relates to arms or suspensions for positioning heads in information storage and retrieval systems, and electronics accompanying those arms for signal transmission. 
     BACKGROUND OF THE INVENTION 
     Information storage devices typically include semiconductor memories such as RAM or electromechanical memories such as hard disk drive systems. Electromechanical memories are sometimes termed mass storage devices, as they are typically more cost effective than semiconductor memories, but may suffer from slower access times and data rates. 
     Conventional hard disk drive systems employ at least one rotating disk having magnetic media layers adjacent to both its major surfaces. Transducers or heads are typically held adjacent to each major surface for writing and/or reading information on the media layers. An arm holding the transducers is moved by an actuator to position the transducers adjacent to various tracks of the rapidly spinning disk. A “linear actuator” typically moves an arm toward and away from a center of the disk along a radius of the disk with which the arm is aligned, whereas a “rotary actuator” rotates an arm about a pivot at a side of the disk to sweep the suspension and transducer across the disk surface. 
     For increased storage capacity, several disks are commonly provided in a single information storage system, each disk having an associated pair of heads for transducing information via each major surface of the disk. The suspension arms for each pair of these heads are commonly mounted to an actuator arm, with the actuator arms extending from an “E-block” and the connected heads, suspension arms and E-block forming a “head-stack assembly.” A rotary actuator moves the E-shaped block to cause all the suspension arms and heads to sweep across the disks in tandem. In addition to increasing overall storage capacity, multi-disk drives can decrease access time. More significant increases in data rates are afforded by improvements in transducer and drive electronics. 
     Conventional disk drives have signal amplifiers that are located on the E-block so that the mass and size of the amplifier chips do not interfere with the positioning of the heads on the disks. Signals between the heads and amplifiers have typically been carried by twisted wires which are held in tubing that runs along the sides of the suspension arm. Head-amplifier signals are modernly carried by electrical traces deposited on the suspension arms, or flexible circuit boards attached to the suspension arms, with additional flexible cables extending along the actuator arms to reach the amplifier. Inductance in the conductors between the heads and amplifiers is a bottleneck in high data rate applications, but can be reduced by shortening the length of the conductors, implying moving the amplifiers closer to the heads. 
     Some inventions have proposed placing an amplifier atop the suspension arm along with the conductors. Unfortunately, this can adversely affect the dynamic performance of the suspension arm, and it may be difficult to make the amplifier thin enough to avoid contact with the disk during operation. Other inventions propose inserting a signal booster element such as a transformer into the conductors that run along the flexures, held by the tubing. Proposals also exist to locate a preamplifier chip on each suspension arm, connected to conductive traces that run on the disk-facing side of each suspension arm. A difficulty with this approach is that the preamplifier chips are each exposed adjacent to a disk and during actuation sweep across the disk surface, which becomes more problematic in the event of a shock to the drive. This limits the size of the chips or, conversely, the size of the chips limits the spacing between disks. Many of these approaches are also constrained by manufacturing difficulties. 
     SUMMARY OF THE INVENTION 
     The present invention solves these problems by locating preamplifier chips adjacent to suspension arms that hold the heads, while fitting the chips into relatively inconspicuous and innocuous areas, interspaced adjacent to each actuator arm so that the chips are not affected by the thickness of the arm. Advantages of the present invention include the potential for decreased spacing between plural disks in a drive system and accelerated data rates. The interspacing can reduce damage to the preamplifier chips as they are further removed from mechanical processes such as swaging that attach the suspension arms to the actuator arms. Damage to the disks or preamplifier chips during operation is also averted according to the present invention, as the chips are removed from the rapidly spinning disk surfaces with which the suspension arms and heads are proximate, and removed from each other to avoid damage during a shock event. The interspacing can also improve performance characteristics of the preamplifier chips, which do not need to be made as thin in order to fit between disks, decreasing costs and problems such as overheating of the chips. Moreover, such larger chips can provide amplification for a pair of heads instead of a single head. The chips may be attached to a mounting end of the suspension arms, eliminating extra support pieces or manufacturing operations. 
     In a first embodiment a pair of preamplifier chips are located adjacent to a pair of baseplates that mount a pair of suspension arms to an actuator arm, the chips being disposed on the same side of the arm but at different distances from their respective heads. A second embodiment includes a preamplifier chip disposed adjacent opposite sides of the arms. In this case the conductors and chip can be attached to the same side of each suspension arm, which results in the chips for “up” and “down” suspension arms being located adjacent opposite sides after attachment of the suspension arms to the actuator arms. A third embodiment utilizes a single chip for both heads, with the chip disposed at the side of the arm adjacent both baseplates and removed from the disk-facing surfaces of the baseplates. The chip or chips may instead be mounted to an actuator arm that also holds the suspension arms, either on the side of the actuator arm or on an end between the suspension arms. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cutaway perspective view of a first embodiment of the present invention, with a pair of actuator arms from a head-stack assembly each having a pair of head suspension arms connected, and a pair of preamplifier chips disposed on one side of each arm, the chips disposed at variable distances from their respective heads. 
     FIG. 2 is a side view of a disk drive system including the heads, suspension arms, actuator arms and chips of FIG.  1 . 
     FIG. 3 is a top view of a second embodiment of the present invention in which a preamplifier chip attached to a top suspension arm is disposed on an opposite sides of an actuator arm than a preamplifier chip attached to a bottom suspension arm. 
     FIG. 4 is a side view of a third embodiment of the present invention in which a single preamplifier chip connected to a pair of heads is attached to a top suspension arm and disposed on a side of an actuator arm. 
     FIG. 5 is a cutaway side view of a fourth embodiment of the present invention in which a pair of preamplifier chips are mounted to a side of an actuator arm adjacent to a mounting end of a pair of suspension arms. 
     FIG. 6 is a cutaway side view of a fifth embodiment of the present invention in which an amplifier chip or chips are mounted to a tip of an actuator arm between a pair of suspension arms. 
     FIG. 7 is a top view of the actuator arm, suspension arms and chips of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a first embodiment of the present invention, in which a pair of actuator arms  20  and  22  forming part of an E-block extend from a pivot of rotary actuator which is not shown, with each of the actuator arms connected to a pair of load beams or suspension arms that each hold a head or slider. Thus actuator arm  20  is coupled at a base plate  25  to a mounting end of a first suspension arm  28 , which holds at its free end a first head or slider  30  having a disk-facing surface  31 . Actuator arm  20  is coupled to a mounting end of a second suspension arm  33  by a second base plate which is hidden in this perspective view, the second suspension arm  33  holding at its free end a second head or slider  35  having a disk-facing surface which is turned away from the viewer of this figure. A tab or flange  38  extends from the mounting end of the first suspension arm  28 , with a first preamplifier chip  40  attached to the flange and electrically connected by a flex cable or conductive traces  41  to the slider  30 . A second flange  43  provides support for a second preamplifier chip  44 , which is electrically connected by a second set of conductive traces  48  that run along a non-disk-facing side of the second suspension arm  33 . As shown below, the conductors can alternatively be attached to either or both a disk-facing side and a non-disk-facing side of the suspension arms. 
     Similarly, a third base plate  50  attaches a third suspension arm  52  to a third slider  55  which has a disk-facing surface  57 . A third flange  58  supports a third preamplifier chip  60  which is electrically connected to slider  55  via flex cable traces  62 . A fourth suspension arm  66  is likewise attached to actuator arm  22  and holds a fourth head  68  which is electrically connected to a fourth preamplifier chip  70  by a fourth set of flex cable traces  72 . A fourth flange  75  extends from the mounting end of the fourth suspension arm  66  to support and protect the fourth chip  70 . The flanges  38 ,  43 ,  58  and  75  may be made from the same sheet as the remainder of their respective suspension arms  28 ,  33 ,  52  and  66 , and do not need additional bending or forming steps to provide a supports for chips  40 ,  44 ,  60  and  70 . In a state free of interaction with the disks, the suspension arms have a slight bend (typically less than fifteen degrees) near the baseplates in order to bias the heads toward the disks, however this bend still leaves the flanges in substantially the same plane as their respective suspension arms. Similarly, side rails rise from the sides of the suspension arms, leaving the suspension arms as substantially flat and flexibly resilient beams. 
     As shown additionally in FIG. 2, preamplifier chips  40  and  44  are attached at significantly different distances from the first and second sliders  30  and  35 , allowing those chips to occupy most of the thickness of arm  20 . Stated differently, compared with having the chips equidistant from their respective sliders, the staggered positioning of the chips allows the actuator arm to be thinner, allowing disks to be positioned closer to each other. An information storage system  80  depicted in FIG. 2 includes three disks  82 ,  84  and  86 , with actuator arms  20  and  22  interspersed between the disks. Preamplifier chips  60  and  70  are also disposed at appreciably different distances from respective third and fourth sliders  55  and  68 , affording the use of full-size preamplifier chips on arm  22 . Each of the preamplifier chips in this system is electrically connected to a mother amplifier  90  attached to E-block  92 , the amplifier  90  in turn connected to a disk drive controller disposed outside system  80  and not shown in this figure. Although preamplifiers  40 ,  44 ,  60  and  70  are shown disposed on the same side of E-block  90  as mother amplifier  90  for clarity, the mother amplifier  90  can be located in alternative positions such as the on a back end of the E-block or actuator and interconnected to the preamps with flex cables. 
     The attachment of preamplifier chips on flanges extending from mounting ends of suspension arms offers a number of advantages over conventional and proposed arrangements. As mentioned above, the actuator arms can be thinner, providing for much thinner head-stack assemblies, yet the chips can be a relatively large size. Such large chips are more cost effective, lowering the price of the drive. Larger chips typically also generate less heat, which can be beneficial to the drive as well as chip performance. Additional forming of the suspension or other metal is not needed, yet the chips are removed from potential damage during swaging. This can lead to a large increase in the percentage of head-stack assemblies that are functional, or “yield” during manufacture, which can swing a project from loss to profit. Operational dynamics are also improved, as pairs of preamp chips are separated and the chance of their collision during a shock to the drive is substantially reduced. The flex circuits  41 ,  48 ,  62  and  72  are maintained essentially in a plane adjacent to their respective suspension arms, further simplifying mechanics. 
     An alternative embodiment of the present invention is shown in FIG. 3, in which a single actuator arm  100  from a drive system is attached to a top and bottom suspension arm, of which only top suspension arm  102  is visible. Top suspension arm  102  is attached to actuator arm  100  by base plate  108 . Top suspension arm  102  holds a head or slider  104 , while the bottom suspension arm holds a bottom head which is likewise not visible in this figure. Preamplifier chip  110  is connected by conductors  112  to head  104 , with preamplifier chip  110  attached to a tab or flange  114  of suspension arm  102 . Another set of conductors  116  connects the bottom head with preamplifier  120 , which is mounted on a flange  122  of the bottom suspension arm. Conductors  112  and  116  are attached along a disk-facing side of top and bottom suspension arms, but cross over to attach to non-disk-facing sides of flanges  114  and  122 , along with chips  110  and  120 . Conductors  112  and  116  may alternatively be attached along non-disk-facing sides of top and bottom suspension arms, as shown in FIG.  1 . Conductors  112  and  116  may be formed of flexible cables or traces, in accordance with disk drive trends toward trace suspension arms, cable interconnects, and flex circuits on suspension arms. Insulative material adjoining the conductors is typically translucent if not transparent and so is not shown for clarity. Another set of conductors  125  runs along a first side of arm  100  to provide electrical interconnection between preamp chip  110  and a mother amplifier disposed on a back end of the actuator, not shown, while conductors  127  are attached to a second side of arm  100  and provide electrical interconnection between preamp chip  120  and the mother amplifier. For the situation in which it is desirable for the sets conductors connecting the preamplifier chips and mother amplifier to be disposed on a single side of the arm, one of those conductor sets can cross over to the other side between the top and bottom suspension arms, and may be attached to the non-disk-facing side of its suspension arm. 
     FIG. 4 shows an another embodiment of the present invention in which a single preamplifier chip  150  provides signal amplification for a pair of heads  152  and  155  that are connected by associated suspension arms  157  and  158  to an actuator arm  160 . A top base plate  162  holds suspension arm  157  to actuator arm  160 , while a bottom base plate  164  holds bottom suspension arm  158  to the arm  160 . Although difficult to see in this side view, the chip  150  is glued or otherwise attached to a flange  166  that extends from a mounting end of suspension arm  157 , similar to the flanges depicted for other embodiments. No such flange extends from suspension arm  158 , allowing electrical interconnection to chip  150  after the suspension arms have been mounted to the actuator arm  160 . Conductors connecting chip  150  and slider  152  are too small to see in this figure; however, conductors  168  interconnecting chip  150  and slider  155  can be seen where they leave the plane of suspension arm  158  to meet the chip. Conductors  170  interconnect preamplifier chip  150  with a mother amplifier, the mother amplifier also interconnected with other preamplifier chips disposed adjacent to other actuator arms, and not shown in this figure. Chip  150  is large enough to combine the functions of split preamplifier chips for the two heads, yet fits adjacent a side of arm  100  while allowing that arm to be as thin as needed for closer disk spacing. 
     FIG. 5 shows an alternative embodiment in which a pair of preamplifier chips  200  and  202  or integrated circuits are mounted to a side of an actuator arm  205 , interspaced between a pair of suspension arms  208  and  210 . The location of such a chip or plurality of chips attached to an actuator arm can instead comprise the various examples listed above for attachment of such a chip to a suspension arm, such as having each of the chips attached to an opposite side of the actuator arm or having a single chip attached to a single actuator arm side. Attachment of the integrated circuit directly to the actuator arm has a number of advantages, including improvements in dynamic performance since the actuator arm is more rigid than the suspension arm, and better thermal conductivity and heat sink capacity for the chip through the large metal actuator arm. Additional advantages include the independence during manufacturing or repair of the amplifier and heads, allowing each to be tested and/or replaced more independently. 
     Electrical conductors such as flex circuits interconnect the preamplifier chips  200  and  202  with respective heads and an E-block mounted amplifier, both not shown in this figure. Thus conductors  212  are electrically connected to chip  200  and mounted to suspension arm  208  for connection to a head held at a far end of that suspension arm, while conductors  215  are electrically connected to chip  202  and mounted to suspension arm  210  for connection to a head held at a far end of that suspension arm. Another pair of conductive traces or the like connect the individual preamps with a mother amplifier, not shown, so that flex cables  217  are connected to preamp  200  and flex cables  220  are connected to preamp  202 . 
     Alternatively, an amplifier chip  230  or chips can be attached between a pair of suspension arms  233  and  235  to a distal end of an actuator arm  240 , as shown in FIG.  6 . This extension of the chips toward the heads can accelerate data transfer rates by shortening lengths of flexible circuits  242  and  244  or conductive traces connecting the heads and amplifier or amplifiers, without interfering with dynamic performance of the slider load beam since the chips are connected instead to the rigid actuator arm. Another pair of flexible conductive cables  246  and  248  connect the chip  230  or chips to a mother amplifier or other drive electronics, not shown. The attachment of the amplifier chip  230  or chips to the distal end of the actuator arm  240  can position the chip adjacent to a void  248  in the load beam  233  that adjoins a spring or hinge  250 , as shown in FIG. 7, so that electrical connections such as ball bonding between the chips and the conductive traces or flex circuits can occur through the voids. A pair of chips may be bonded to each other as well as to the actuator end. The conductors  242  can be disposed along a disk-facing or a non-disk-facing side of the beam to connect with slider  252 , and need not pass through the void when disposed along the non-disk-facing side. 
     While a number of embodiments have been described above, variations and modifications of those embodiments are possible in accordance with the spirit and teachings of the present invention. Thus the scope of the invention is not to be limited by the foregoing examples but defined according to the following claims.