Abstract:
A microactuator, or micromotor, ( 60 ) and method for making it are presented such that a symmetrical build up of material is performed on opposite sides of a substrate. This reduces mechanical stresses in the device. In its construction, respective layers of circuit portions ( 108, 110 ) are built on each side of the structure, thereby eliminating the need to stack complex patterns. Stacking one complex pattern on top of a similar pattern is difficult because the surface, which is the base for subsequent layers, is not flat. The photolithography process that forms these patterns is not very forgiving to non-flat surfaces. Avoiding the stacked layers also allows thicker conductors to be considered for each circuit. Thicker circuits increase current carrying capacity, which in one of the key variables increase the power of the micromotor.

Description:
CROSS REFERENCES TO RELATED PATENT APPLICATIONS 
     This invention is related to application Ser. No. 09/607,414 filed Jun. 28, 2000 application Ser. No. 09/607,087 filed Jun. 28, 2000 and application Ser. No. 09/607,413 filed Jun. 28, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates in part to improvements in methods and apparatuses for dynamic information storage or retrieval, and more particularly to improvements in methods and circuitry for positioning a transducer for writing or detecting data written onto a spinning data disk, and still more particularly to improvements in microactuator structures and methods for making same. This invention also relates in part to improvements in components used in microelectromechanical systems and methods for making same. 
     2. Relavant Background 
     Mass data storage devices include well known hard disk drives that have one or more spinning magnetic disks or platters onto which data is recorded for storage and subsequent retrieval. Hard disk drives may be used in many applications, including personal computers, set top boxes, video and television applications, audio applications, or some mix thereof. Many applications are still being developed. Applications for hard disk drives are increasing in number, and are expected to further increase in the future. Mass data storage devices may also include optical disks in which the optical properties of a spinning disk are locally varied to provide a reflectivity gradient that can be detected by a laser transducer head, or the like. Optical disks may be used, for example, to contain data, music, or other information. 
     In the construction of mass data storage devices, a data transducer, or head, is generally carried by an arm that is selectively radially positionable by a servo motor. Recently, micromotors, or microactuators, have been investigated to provide better, or more accurate, position control of the head. 
     In one design, a piezoelectric “I-beam” element has the actuator mounted on an arm or suspension element. The actuator may be co-located with the head on the end of a suspension to provide a fine positioning capability to the head. However, the piezoelectric element suffers several disadvantages. For example, voltages on the order of 30 volts are required for suitable operation. Such high voltages are undesirable in most hard disk drive applications. Also, the range of movement that can be achieved is on the order of only ±1 μm. This may be enough with sufficiently high disk rotation velocities, but it is generally seen as a limitation of this system. 
     In another design, a microactuators that has been investigated has a microactuator element co-located with the head on the end of the arm. The microactuator may be rectangular in shape, with a platform portion to which the head is attached, and a frame portion to which the platform is tethered. The platform and frame are designed to allow the platform to freely move in only one direction in response to a current applied to associated coils. The movement of the platform causes fine radial movement of the head, for example, on the order of ±5 μm, in an axis normal to the length of the arm. 
     Through the provision of fine head positioning, such as by the microactuators of the type described, the track density can be packed closer together since the head position can be more accurately controlled. Thus, the higher precision of head positioning can lead to a higher number of tracks per inch that can be created on the disk. Also, the speed of the motor can be increased, and the quality of the bearings can be decreased, since the head can be more accurately positioned. 
     From a three-dimensional perspective, when multiple disks are used with corresponding multiple heads, the ability to provide fine position control to individual heads of the stack of heads and disks enables each head to be individually positioned to tracks within its position control range. This is in contrast to structures that are required to track along the same paths as each of the other heads. This adds great flexibility and functionality to the drive that would not otherwise be available. Among other things, this would provide an ability to write to the disks with parallel data streams, greatly increasing its speed. 
     In the construction of microactuators in the past, one process that was used began with a silicon wafer about 24 mils thick. For example, a cross-section side view of a portion  10  of a microactuator is shown in FIG.  1 . As can be seen, a nickel-iron structure  12  is formed on a silicon wafer substrate  14 , on both sides of a gap  16 . The gap  16  shown is the gap separating the tethered wafer structure  18  and the surrounding arm structure  20 . 
     A dielectric material  22  is built up adjacent to the nickel-iron material  12 , and copper coils  24  and connection wiring  26  surround a portion of the nickel-iron structure  12 , encapsulated by the dielectric  22 . The various structures are built up in layers by photolithographic, material deposition, lapping, and other known processes. These layers of dielectric, copper, and nickel-iron were built up on the wafer to form a sandwich of materials. The nickel-iron provided a necessary magnetic material, and the copper formed the coils to which a positioning current may be applied. Then con wafer was lapped, sawed, or ground off to produce a microactuator which had a thickness on the order of about 100 μm. Once this was done, however, due to the significantly differences of thermal coefficients of expansion of the various materials, the extremely thin resulting part was extremely vulnerable to warping or buckling. The various parts also tend to delaminate from the remaining wafer substrate, and made the production yield extremely small. 
     Limited capability of either molding or a photographic process, which is utilized to construct the high aspect ratio (height-to-width) layers of metal and dielectric material, are also important problems. The thickness of these material layers is a primary factor in generating the required amount of magnetic force in the micromotor, or microactuator. This force, in turn, drives the amount of travel of the platform in the motor. Large travel is a key market desire. 
     What is needed, therefore, is a microactuator structure and method for constructing it that results in a device that is not as susceptible to the stresses caused by the differences in the thermal coefficients of expansions of the various required materials. 
     Additionally, recent interest has been devoted to microelectromechanical systems (MEMS), for many varied applications, such as accelerometers, mirror positioning, and the like. In many MEMS control devices, a platform is suspended by a hinge or tether in a window in a larger yoke or base. However, the substrates upon which such structures are constructed are generally very thin, on the order of a few to a few hundred microns. Consequently, they suffer the same distortion problems as described above with respect to the mass data storage device positioning arms. 
     SUMMARY OF THE INVENTION 
     In light of the above, therefore, it is an object of the invention to provide a microactuator or micromotor device that is less susceptible to distortion or warping, due to differences in thermal expansion of the various parts used to realize the structure. 
     It is another object of the invention to provide improved methods for manufacturing microactuator or micromotor devices, for use, for example, in mass data storage devices or microelectromechanical systems. 
     Thus, according to one aspect of the invention, a method for making a micromotor or microactuator is presented such that a symmetrical build up of material is allowed, thus reducing mechanical stress. More particularly, one layer of circuits is built; on each side of the structure, thereby eliminating the need to stack complex patterns. Stacking one complex pattern on top of a similar pattern is difficult, because the surface, which is the base for subsequent layers, is not flat. The photolithography process that forms these patterns is not very forgiving to non-flat surfaces. Avoiding the stacked layers also allows thicker conductors to be considered for each circuit. Thicker circuits increase current carrying capacity, which is one of the key variables that increases the power of the micromotor. 
     According to another aspect of the invention, a method is presented to build a balanced micromotor by starting with a thin silicon wafer, plasma etching the desired pattern for the coil traces into the silicon and then plating copper or other electrically conductive metal into that pattern. NiFe metal is then built up on the two sides of the silicon, at the interface between the movable and non-movable segments of the device, and through the middle of the coil traces. This completes the material set required to form an electromagnetic field that is the source of the force driving the movement of the micromotor. 
     In yet another embodiment, a manufacturing method is presented which is similar to previous methods except that the sequential layers are added to both sides of the silicon wafer. This provides a balanced mechanical stress structure. This alternative utilizes a variation of the above-described method to form the electrical path to connect the bottom and top circuits. The silicon will be removed and an electrically conductive material, such as copper, will be deposited in the via. The layers of circuits for the motor coils and the NiFe are added in an alternating, sequential manner to the two sides of the silicon. 
     In still another embodiment, a piece-part manufacturing approach is presented. In this approach, two NiFe parts and dielectric and copper piece-parts are manufactured separately. This method allows the NiFe parts to be designed in a manner to maximize the thickness of the metal, which in turn increases the magnetic properties of the motor. The dielectric and copper coils piece-part may be a thin-film interconnect or some derivative of a standard flex circuit printed wiring board. These piece-parts may be tested individually, defective parts discarded, and only functional units assembled. This not only produces a mechanically balanced construction, but has lower cost due to non-sequential manufacturing steps. The dielectric and copper coils piece-part also provides the path for electrical connections to the movable platform and a relatively easy method for electrical connection off the microactuator and onto the hard disk drive system. 
     Thus, according to a broad aspect of the invention, a microactuator of the type having base and a platform hinged or tethered thereto is presented. The microactuator has first microactuator elements constructed on the base and second microactuator elements mounted on the opposite side of the base. The first microactuator elements are located substantially symmetrically on either side of a plane along a centerline of the substrate base so that warpage of the parts due to thermal expansion of the parts on each side of the plane cancel. 
     According to another broad aspect of the invention, a microactuator for use in a mass data storage device of the type having an arm that carries a transducer that is selectively positioned adjacent a spinning rotating disk is presented. The microactuator has a first portion carried by the arm and a second portion tethered in an aperture in the first portion to form a platform therewithin. First microactuator elements are mounted in the first portion, and second microactuator elements are mounted in the second portion so that movement of the platform moves a position of the transducer. The first microactuator elements are located substantially symmetrically on either side of a plane along a centerline of the first portion. 
     According to another broad aspect of the invention, a method is presented for manufacturing a microactuator structure. The method includes providing a substrate having first and second opposing sides, and alternatively and sequentially building up structure layers of the microactuator on the first and second sides. 
     According to yet another broad aspect of the invention, a method for manufacturing a microactuator structure is presented. The method includes providing a substrate having first and second opposing sides, and simultaneously building up structure layers of the microactuator on the first and second sides. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is illustrated in the accompanying drawings, in which: 
     FIG. 1 is a side cross-section of a microactuator structure, according to the prior art. 
     FIG. 2A is a block diagram of a mass data storage device, illustrating the environment of the invention. 
     FIG. 2B is an exploded view of a portion of the arm structure of FIG. 2A that carries the read/write head. 
     FIG. 3 is a side cross-section of a microactuator structure, according to a preferred embodiment of the invention, constructed using a silicon mold technique, according to a preferred method embodiment of the invention. 
     FIG. 4 is a top plan view of the microactuator structure of FIGS. 3,  6 , and  8  according to a preferred embodiment of the invention. 
     FIGS. 5A-5I are side cross-section drawings illustrating the sequence of steps used in making the microactuator structure of FIG. 3, according to a preferred embodiment of the invention. 
     FIG. 6 is a side cross-section of a microactuator structure, according to a preferred embodiment of the invention, constructed using a double-sided sequential build up method, according to a preferred method embodiment of the invention. 
     FIGS.  7 A- 7 HH are side cross-section drawings illustrating the sequence of steps used in making the microactuator structure of FIG. 6, according to a preferred embodiment of the invention. 
     FIG. 8 is a side cross-section of a microactuator structure, according to a preferred embodiment of the invention, constructed using a piece-part method, according to a preferred method embodiment of the invention. 
     FIG. 9 is an exploded side cross-section of the microactuator structure of FIG.  8 . 
     FIGS. 10A-10E are side cross-section drawings illustrating the sequence of steps used in making Piece-part A used in the construction of the microactuator structure of FIG. 8, according to a preferred embodiment of the invention. 
     FIGS. 11A-11C are side cross-section drawings illustrating the sequence of steps used in making Piece-part B used in the construction of the microactuator structure of FIG. 8, according to a preferred embodiment of the invention. 
     FIGS. 12A-12D are side cross-section drawings illustrating the sequence of steps used in making Piece-part C used in the construction of the microactuator structure of FIG. 8, according to a preferred embodiment of the invention. 
     FIGS. 13A-13E are side cross-section drawings illustrating the sequence of steps used in assembling Piece-parts A-C used in the construction of the microactuator structure of FIG. 8, according to a preferred embodiment of the invention. 
    
    
     In the various Figures of the drawing, like reference numerals are used to denote like or similar parts. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 2A is a block diagram of a generic disk drive system  25 , which represents the general environment in which the invention may be practiced. The system  25  includes a magnetic media disk  26  that is rotated by a spindle motor  28  and spindle driver circuit  30 . A data transducer or head  32  is locatable along selectable radial tracks (not shown) of the disk  26  by a voice coil motor  34 , along a gross radial position  36 . A microactuator  38 , which may be constructed in accordance with one of the methods of the invention, described below in detail, may be co-located with the head  32  on the end of the arm  40 , as shown in detail in FIG.  2 B. The motion of the microactuator  38  may be a displacement to the left or right of the arm  40  axis, to provide fine radial positioning of the head  32  along fine radial position  42 . 
     The radial tracks may contain magnetic states that contain information about the tracks, such as track identification data, location information, synchronization data, as well as user data, and so forth. The head  32  is used both to a record user data to and read user data back from that disk  26 . The head  32  also detects signals that identify the tracks and sectors at which data is written, and to detect servo bursts that enable the head  32  to be properly laterally aligned with the tracks of the disk, as below described. 
     Analog electrical signals that are generated by the head  32  in response to the magnetic signals recorded on the disk  26  are preamplified by a preamplifier  44  for delivery to read channel circuitry  46 . Servo signals, below described in detail, are detected and demodulated by one or more servo demodulator circuits  48  and processed by a digital signal processor (DSP)  50  to control the gross  36  and fine  42  positions of the head  32  via a positioning driver circuit  52 . In the past, the servo data would that. is read and processed has been analog data that has been interpreted by the DSP  50  for positioning the head  32 . 
     A microcontroller  54  is typically provided to control the DSP  50 , as well as the interface controller  56  to enable data to be passed to and from the host interface (not shown) in known manner. A data memory  58  may be provided, if desired, to buffer data being written to and read from the disk  26 . 
     With reference additionally now to FIG. 2B, one microactuators environment that may be used includes a microactuator  38  that is co-located with the head  32  on the end of the arm  40 . The microactuator  38  may be rectangular in shape, and includes two parts. The first part is a platform  33  to which the head  32  is attached. The second part is a frame  35  around the platform  33 . These two parts are joined by tethers  37  that are designed to allow the platform  33  to freely move in only one direction  39 . 
     The frame  35  may be attached to a paddle  41  formed as a part of a flexure element  43 . The paddle  41  acts as a bearing or gimbal to allow movements of the frame  35  and head  32 , for example, due to changes in elevation of the disk surface, or other surface nonuniformity. 
     Typical tether sizes, for example, are on the order of 4 μm wide by 100 μm high by 180 μm long. Coils (not shown) are also located on and adjacent the frame  35  at strategic locations so that the application of a current to the coils causes the platform to move. The movement of the platform  33  causes fine radial movement of the head  32 , for example, on the order of ±5 μm, in an axis normal to the length of the arm  40 . 
     With respect to the manufacturing of the microactuator, to minimize warping caused by an unbalanced deposition of materials onto a substrate, a balanced or symmetrical arrangement of microactuator parts is provided, in accordance with a preferred embodiment of the invention. Thus, with additional reference now to FIG. 3, one balanced construction configuration of a microactuator is shown. FIG. 3 shows a portion of a microactuator  60 , which includes a first portion  62  that is constructed in the shape of a frame that is to be rigidly attached to the arm, and a second portion  64  that forms a platform located within a hole in the first portion  62  to be moveable to cause lateral movement of the platform and head (not shown) which has been rigidly attached and carried thereon. The platform  64  is spaced from the first portion  62  by a gap  66 . 
     An “I” shaped nickel-iron member  68  is formed extending through a central silicon substrate  70 . The nickel-iron member  68  has a downwardly extending portion  72  on the frame side  62 . A corresponding downwardly extending nickel-iron member  74  is also provided on the platform member  64 . 
     A plurality of copper coils  76  are provided surrounding the center portion of the nickel-iron structure  68  to generate a magnetic flux in the nickel-iron structure  68  when the copper coils are energized, for example, by a current passing therethrough. The flux in the nickel-iron member  68  is transferred between the downwardly extending portions  72  and  74  to cause the platform portion  64  to be moved to produce a resultant movement in the arm to move the head or transducer thereon. 
     It should be observed that the various structures in the embodiment  60  illustrated are substantially symmetrical about a plane  78  extending centrally through the silicon substrate  70 . with respect to the top and bottom thereof. Thus, in the embodiment illustrated, the coil members  76  are actually embedded in the silicon substrate  70 , contained between the top and bottom surfaces thereof. 
     A dielectric layer  77  is provided on the top and bottom portions of the silicon substrate  70  to isolate the nickel-iron member  68  from the conductive copper coils  76 . A hole  80  is formed in the dielectric member  77  to facilitate electrical contact to the copper coils  76  to enable an actuating current to be passed therethrough. 
     A plan view of the device  60  of FIG. 3 is shown in FIG. 4, to which reference is now additionally made. As can be seen, the center-platform portion  64  maybe held to the arm portion  68  by tethers  82  at the respective corners thereof to be spaced from the frame portion  62  by a surrounding gap  66 . The coils  76  are located on the frame portion to generate the magnetic flux in the nickel-iron members  68 . 
     One method for constructing the device  60  of FIGS. 3 and 4 is shown in the steps illustrated in FIGS. 5A-5I, to which reference is now additionally made. At the start, two silicon wafers  70  and  84  are provided. The silicon wafer  84  will serve as a base or carrier to enable processing of the silicon wafer  70 , which will become the final silicon substrate of the microactuator. One face of the silicon wafer  70  is coated with a layer  86  of a seed material, preferably copper, or the like. The copper layer  86  will serve both as an etch stop or indicator, as will be apparent from FIG. 5D described below in detail and as the electrically conductive path to allow electroplating of features as will be apparent from FIG. 5E described below in detail. The copper layer  86  may be, for example, 2000 Å to 4000 Å thick. The copper layer  86  is then coated with a layer of high sodium glass  88 . 
     Similarly, the silicon wafer  84  is coated with a similar layer of high sodium glass  90 . The high sodium glass layers  88  and  90  enable the silicon wafers  70  and  84  to be joined by bringing them into contact and heating them and/or passing a suitable current through them, until the high sodium glass layers join together, as shown in FIG.  5 B. Alternatively, the high sodium glass layers  88  and  90  may be replaced with a suitable cast film of adhesive material (not shown). If the thickness is held uniformly thick, the levelness of the resulting structure can be held to a suitable tolerance. 
     As next shown in FIG. 5C, the top portion of the wafer  70  is removed, for example, by lapping or other suitable technique to provide a wafer of desired thickness, that will be used in the final microactuator structure. A suitable thickness may be for example, between about 100 μm and 200 μm, and may preferably be about 125 μm. 
     As shown in FIG. 5D, the top silicon layer  70  is etched to form patterned trenches  92  into which the copper materials will be deposited to form the coils of the actuator, and trenches  94  into which the nickel-iron structures to provide the magnetic flux carrying member. The trenches  92  may be, for example, between about 5 μm and 15 μm, and may preferably be about 10 μm, and the trenches  94  may be, for example, between about 20 μm and 200 μm, and may preferably be about 75 μm. The spacers between the trenches  92  may be, for example, between about 5 μm and 10 μm, and may preferably be about 7 μm. 
     As shown in FIG. 5E, the copper  96  and nickel-iron  98  materials are then electroplated into the respective trenches  92  and  94  and the excess materials removed from the top surface  100  of the silicon substrate  70 . Although the copper and nickel-iron are shown to be deposited in a single step in FIG. 5E, it will be understood that the copper and nickel-iron would be deposited in sequential steps, using, for example, patterned photoresist to expose only those trenches or windows into which the respective copper or nickel-iron is to be deposited. 
     Thus, for example, a layer of photoresist may be applied overall and patterned to expose the windows into which copper to form at least a portion of the actuating coils is to be deposited. The copper is then deposited and etched back to-the desired top level. The photoresist is then removed and a second photoresist layer is applied and patterned to expose the windows where trenches  94  into which the nickel-iron material are to be deposited. The nickel-iron material is then deposited and etched back to form the desired height level. In the embodiment shown, the desire height level for both the copper and nickel-iron layers is the top and bottom surfaces of the substrate  70 . The photoresist layer is then removed. The coil and other interconnections  102  are then added, as shown in FIG.  5 F. 
     At this point, the bottom layers that include the silicon supporting base  84 , high sodium glass  88 , 90 , and copper layer  86  are then removed from the structure, for example, by lapping or other suitable technique, as shown in FIG.  5 G. As shown in FIG. 5H, dielectric layers  104  and  106  are respectively deposited on the top end bottom surfaces of the silicon substrate  70 , including the copper structures  96  thereon, but not over the nickel-iron structures  98 . The dielectric layer  104  is then suitably patterned to enable top and bottom patterned nickel-iron material  108  and  110  to be formed in contact with the nickel-iron structures  98  that remain in the silicon substrate  70 . The thickness of the nickel-iron layers  108  and  110  may be, for example, between about 20 μm and 100 μm, and may preferably be about 40 μm. 
     Finally, as shown in FIG. 5I, the dielectric and silicon materials are selectively removed from the gap  66  leaving only tethers which connect the platform  64  to the frame  62  to produce the final electromechanical actuator structure  60 . The dielectric and silicon materials may be removed from the gap  66 , for example, using one or more directional plasma etching techniques and appropriate masking. The gap  66  may be, for example, between about 3 μm and 15 μm wide, and may preferably be about 7 μm wide. 
     Another embodiment of a microactuator  120  is shown in FIG. 6, to which reference is now additionally made. The microactuator  120  is similar to the microactuator  60  shown in FIG. 3, except that the coil material is not imbedded in the silicon substrate. 
     More particularly, the microactuator  120  has a first portion  122  that forms a frame that is connected to a second portion that forms the tethered island or platform  124  for moving the head (not shown). The frame portion  122  and the platform portion are formed in a substantially symmetrical fashion about a plane  126  that is essentially located along the centerline of a silicon substrate  128 . The copper coils  130  are formed adjacent and above the top and bottom surfaces of the silicon substrate  128 , embedded in dielectric layers  132  also on the top and bottom of the silicon substrate  128 . The dielectric layers  132  and  134  isolate the copper coils  130  and their interconnection traces  131  electrically from other parts of the device. Finally, the nickel-iron “I” shaped member  136  is provided with an end piece  138  and a corresponding actuator receiving piece  140  to transfer the magnetic flux generated by the coils  130  across the gap  185  to move the platform  124 . 
     It is observed that the overall structure of the microactuator  120  is substantially symmetric with respect to the centerline plane  126  through the silicon substrate  128 . As a result, due to the differences in the coefficient of thermal expansion, changes one side of the silicon substrate  128  would be matched by similar changes of the materials on the opposite side. This results in a decrease in the likelihood of the overall structure or parts thereof cupping, bowing or otherwise distorting. 
     The plan view of the finished microactuator is substantially the same as the plan view of FIG. 4 described above with reference to the microactuator  60  of FIG.  3 . 
     One method for making the microactuator  120  is shown in sequential steps illustrated in the cross-section views of FIGS.  7 A- 7 HH, to which reference is now additionally made. In the method of this embodiment, the structures are formed first on one side of the substrate  128 , then on the other. The start of the construction of the microactuator  120  begins with the provision of two silicon wafers  128  and  142 . The wafer  142  provides a support or base to enable the construction of the various parts of the microactuator in and around the upper silicon wafer  128 , and serves as a sacrificial carrier wafer. The upper silicon wafer  128  has a coat of a seed material, such as copper, or the like  146  on a bottom face thereof. The copper layer may be, for example, 2000 Å to 4000 Å thick. The copper layer  146  is coated with a layer of high sodium glass  148 . Similarly, the top surface of the silicon wafer  142  has a layer of high sodium glass  150  formed thereover. 
     As shown in FIG. 7B, the top and bottom silicon wafers  128  and  142  are bonded together, by heating the structure to a temperature of about 300° C. and applying a voltage of a few hundred volts to create a single structure, as shown. Again, alternatively, the high sodium glass layers  148  and  150  may be replaced with a suitable cast film of adhesive material (not shown). If the thickness is held uniformly thick, the levelness of the resulting structure can be held to a suitable tolerance. 
     As shown in FIG. 7C the top silicon wafer  128  is thinned, for example, by lapping, or other appropriate process, to the desired thickness. A suitable thickness for the top wafer  128  may be for example, between about 100 μm and 200 μm, and may preferably be about 125 μm. The top silicon wafer  128  is then imaged and etched with a pattern to form a mold into which the required metal features will be formed, as shown in FIG.  7 D. The pattern includes a number of apertures or windows  152  that will receive the metal for the copper wiring and nickel-iron materials. The copper  154  and nickel-iron  156  features are then molded into the apertures  152 , as shown in FIG.  7 E. The width of the windows  152  and the nickel-iron features  156  molded thereinto may be, for example, between about 25 μm and 200 μm, and may preferably be about 75 μm. A second layer of seed material, such as copper,  158  is then formed overall, as shown in FIG.  4 F. The copper layer may be, for example, 2000Åto 4000 Å thick. 
     As shown in FIG. 7G, the copper layer  158  is then coated with a layer of photoresist material  160 , which is patterned to form a mold to contain the copper coils and interconnection traces. Thus, the photoresist layer  160  is patterned to form windows  162  into which the copper coil and copper traces will be subsequently molded or plated. The windows  162 , and the copper material that will be plated thereinto may be, for example, between about 5 μm and 15 μm, and may preferably be about 10 μm. The space between the windows  162  may be, for example, between about 5 μm and 10μm, and may preferably be about 75 μm. 
     Next, as shown in FIG. 7H, copper material is electroplated into the windows  162  of the photoresist layer  160 , as shown in FIG.  7 H. The copper material, denoted by the reference numeral  164 , will form one-half of the coils  130  (see FIG.  6 ). Following the formation of the copper in the apertures of the photoresist layer  160 , the photoresist layer  160  is removed or stripped as shown in FIG.  7 I. 
     As shown in FIG. 7J, the exposed portions of the seed, or copper layer,  158  are next etched away, and a permanent dielectric layer  134 , as shown in FIG. 7K, is formed over the structure and to the top level of the copper elements  164 . The thickness of the dielectric layer  134  may be, for example, between about 10 μm and 20 μm, and may preferably be about 15 μm. The portions of the dielectric layer  134  are patterned to form windows  168  exposing the underlying nickel-iron plugs  156 , as shown in FIG. 7L The nickel-iron plugs  170  are then formed in the windows  168  to contact the underlying nickel-iron plugs  156 , as shown in FIG.  7 M. The resulting nickel-iron plugs  170  extend to the top layer of the dielectric  134  to enable them to subsequently be contacted, as described below. An additional dielectric layer  172  is then formed overall to encapsulate the copper elements  164  and nickel-iron elements  170 , as shown in FIG.  7 N. 
     The dielectric layer on  172  is then imaged and etched to form windows  174  to expose the nickel-iron plugs  170 , as shown in FIG. 70. A seed material, or copper layer,  176  is then formed overall, contacting the nickel-iron plugs  170  within the windows  174 , as shown in FIG.  7 P. The copper layer may be, for example, 2000 Å to 4000 Å thick. In addition, a layer of photoresist  180  is formed overall and patterned to form windows  182  to enable the next layer of nickel-iron features to be formed. 
     The nickel-iron features  184  are subsequently formed in the windows  182 , as shown in FIG.  7 Q. The depth of the window  182  into which the nickel-iron structures  184 , and therefore the depth of the nickel-iron structure  184 , may be, for example, between about 20 μm and 100 μm, and may preferably be about 40 μm. It will be appreciated that the nickel-iron regions  184  contact the underlying nickel-iron regions  170  through the copper layer  176 , and form the top half of the “I” shaped nickel-iron structure  136  shown in FIG.  6 . The photoresist layer  182  is then stripped, as shown in FIG.  7 R. Next, as shown in FIG. 7S, the portions of the copper layer  176  and the dielectric  166  which lie between the two nickel-iron bars is removed, to form a portion of the gap  185 . The dielectric and silicon materials may be removed from the gap  185 , for example, using one or more directional plasma etching techniques and appropriate masking. The width of the gap  185  may be, for example, between about 3 μm and 15 μm, and may preferably be about 75 μm. 
     At this point, the entire assembly is flipped and mounted to another sacrificial carrier  186 , as shown in FIG.  7 T. The original silicon sacrificial carrier wafer  142  and the glass layers  148  and  150  are then removed, as shown in FIG.  7 U. 
     Following the removable of the original sacrificial carrier wafer  142 , the process is essentially repeated on the opposite side of the silicon substrate  128 . Thus, as shown in FIG. 7V, the copper layer  146  is coated with photoresist, which is patterned and selectively removed to enable copper material  190  to be plated into the patterned windows. The copper material  190  will complete the second half of the coils  130  to be constructed. Contact between the top and bottom coil members is made by the feedthrough conductor  154  formed in FIG. 7E above. The photoresist material is then removed. The top surface of the structure is then recoated with a another photoresist layer  192 , as shown in FIG.  7 W. 
     As shown in FIG. 7X, the photoresist layer  192  is patterned and etched to the copper layer  146  overlying the nickel-iron plugs  170 . The etching leaves windows  196 , as shown. Additional nickel-iron features  198  are formed in the windows  196 , as shown in FIG.  7 Y. The nickel-iron features  198  contact the copper layer  146  overlying the lower portion of the structure. 
     The top dielectric or photoresist layer  192  is then stripped from the structure, as shown in FIG.  7 Z. The exposed portions of the copper layer  146  are then removed, as shown in FIG.  7 AA. At this juncture, it should be observed that the nickel-iron structures are now continuous and isolated from the copper structures  164  and  190  forming the coils  130  of the microactuator. At this point, as shown in FIG.  7 BB, a layer of permanent dielectric material  132  is formed over the structure. The thickness of the dielectric layer  132  may be the same as that of the previously formed dielectric layer  134 . The dielectric layer  132  is then imaged, and a pattern is etched to expose the top portion of the nickel-iron plug  198  through window  202 , as shown in FIG.  7 CC. 
     A layer of a seed material  204 , preferably copper, or the like is deposited overall, as shown in FIG.  7 DD. The copper layer may be, for example, 2000 Å to 4000 Å thick. A nickel-iron top plate member  206  is patterned and formed on the copper layer  204  as shown is FIG.  2 EE. At this juncture, it should be observed that the top nickel-iron member  206  contacts the lower nickel-iron member  184  through the central nickel-iron and copper regions  198  and  170 , as shown, to form the “I” shaped nickel-iron member  136  described in FIG. 6, surrounded by the copper coils  130 . The remaining copper material of layer  204  which is exposed is then removed, as shown in FIG.  7 FF. 
     As shown in FIG.  7 GG, the dielectric and silicon separating the frame and platform structures is selectively removed from the gap  185 , leaving only the tethers connecting the frame to the platform. At this juncture, it should be observed that the structures  138  and  140  are completed to form the flux transfer structures for coupling the magnetic flux from the “I” nickel-iron structure to move the platform structure  124 . 
     Finally, the second sacrificial carrier wafer  186  is removed as shown in FIG.  7 HH, and the structure is inverted to complete the construction of the microactuator  120 . 
     Another technique for accomplishing a microactuator device having symmetry about a supporting substrate can be accomplished by a piece-part assembly technique. A device that results from a piece-part assembly technique, according to the invention, is shown in cross-section in FIG.  8 . The device, denoted by the reference numeral  220 , is formed on a substrate, which may be, for example, a flex printed wiring board (PWB)  222 . 
     It can be seen that the volume, modulus, and mass of the devices on either side of the centerline  224  are substantially the same. As will be seen, the construction of the actuator  220  is accomplished with three piece-parts, denoted piece-part A  221 , piece-part B  223 , piece-part C  225 . The resulting structure has an “I” shaped nickel-iron flux-conducting structure  226  that is excited by copper coils  228 . The copper coils  228  on top and bottom of the PWB  222  are interconnected by a feedthrough conductor  230 . 
     The frame portion  232  of the actuator assembly  220  is rigidly connected to the arm, for example, of a mass data storage device, with an internal tethered platform member  234  located within the window in the frame  232 . Corresponding nickel-iron flux-conducting members  236  and  238  are provided as a part of the respective piece-parts, which, when fabricated, are located through an aperture  240  in the PWB  222  to conduct the flux from the nickel-iron member  226  on the frame  232  to the nickel-iron member  238  on the platform member  234 . 
     More particularly, with reference now to FIG. 9, an exploded view of the microactuator  220  is shown illustrating the assembly of the respective three piece-parts. Thus, piece-part C  225  is first constructed using a PWB  222  having copper coils  228  and coil feedthrough conductor  230  constructed thereon. Piece-part A  221  is constructed of nickel-iron and has pillars  244  and a bar  246  outwardly extending from a top member  242 . The pillars  244  and the bar  246  are received in holes  248  and  250  formed through the PWB  222 . Piece part A  221  also includes a nickel-iron member having another bar  260  that extends downwardly from a horizontal member  258 . The bar  260  is received in a hole  264  through the PWB  222  to provide the flux receiving members on the platform  234  of the microactuator  220 . Piece-part B  223  is another nickel-iron member having a hole  254  therethrough to receive the pillars  244  extending through the hole  248  on the bottom side of the PWB  222 . Piece-part C  225  includes the PWB  222  and coil members  228 . 
     The method for the construction of piece-part A  221  is shown in the cross-section views of FIGS. 10A-10E. Thus, with reference first to FIG. 10A, in the construction in piece-part A  221 , a carrier silicon wafer  266  is plated with a seed metal layer  268 , such as copper or the like, and a nickel-iron layer  270  is formed thereover. The nickel-iron layer  270  may be, for example, of thickness of between about 20 μm and 120 μm, and may preferably be about 60 μm. The nickel-iron layer  270  is patterned to form windows  272  therein. The nickel-iron layer  270  will provide the bottom motor structure, as will become apparent. 
     As shown in FIG. 10B, a layer of photoresist  274  is deposited over the nickel-iron layer  270  and in the windows  272  thereof to temporarily immobilize the entire structure. Although the use of photoresist is presently preferred, other materials, such as polystyrene, benzoic acid, or the like may also be used to provide a dimensionally stable structure. Such other materials, however require consideration how they can be removed, such as through the use of particular solvents, vacuum sublimation techniques, and so forth. Windows or trenches  276  are etched in the silicon carrier  266  to form the nickel-iron core and motor gap pattern, as shown in FIG.  10 C. Nickel-iron elements  244 ,  246 , and  260  are then plated into the trenches  276  in the silicon carrier  266 , as shown in FIG.  10 D. The width of the nickel-iron elements  244 ,  246 , and  260  may be, for example, between about 25 μm and 200 μm, and may preferably be about 75 μm. Then, as shown in FIG. 10E, the silicon carrier material  266  is removed. It should be noted that the removal of the silicon material between frame  246  and the platform  260  forms the gap between the platform and frame portion of the structure. This completes the construction of piece-part A  221 . 
     The construction of piece-part B  223  is illustrated in the sequential steps shown in the cross-section views in FIGS. 11A-C to which reference is now additionally made. At the outset, a carrier silicon wafer  280  is provided, and coated with a seed material  282 , such as copper or the like. A nickel-iron layer  252  is formed on the copper layer  282  and patterned with a window  254  to form the top motor structure. The nickel-iron layer  252  may have approximately the same width as the nickel-iron member  242  of piece-part A  221 , described above. An immobilizing wafer mount layer  284 , which may be of a photoresist or other suitable material, is formed onto the top surface of the patterned nickel-iron layer  252 , as shown in FIG.  11 B. Again, Although the use of photoresist is presently preferred, other materials, such as polystyrene, benzoic acid, or the like may also be used to provide a dimensionally stable structure. Finally, as shown in FIG. 1C, the carrier silicon wafer  280  and copper layer  282  are removed, for example, using a wet or dry chemical etching method. This completes the construction of piece-part B  223 . 
     The construction of piece-part C  225  is illustrated in FIGS. 12A-12D to which reference is now additionally made. The structure again begins with the provision of a carrier silicon wafer  286  which has been coated with a seed material  288 , which may be copper or the like. The seed material  288  is coated with a photoresist material (not shown), which is patterned to provide the required shape mold for the subsequent deposition of copper to form the copper coils and system interconnects. 
     The photoresist is then removed leaving a portion of the copper coils and interconnects  290 , as shown in FIG.  12 A. As shown in FIG. 12B, a PWB material  292  is then formed onto the surface of the copper layer  288 . The PWB material may be of width, for example, between about 100 μm and 200 μm, and may preferably be about 125 μm. Additional copper regions are selectively formed to complete the coils  294  and interconnections  296 . The width of the copper elements  228  and  230  may be, for example, between about 5 μm and 15 μm, and may preferably be about 10 μm. The PWB material in the regions that will receive the nickel-iron piece-parts is then removed to form windows  240  and  248 . It is noted that portions of the PWB material forming the window  240  will remain in the area of the gap between the platform and transducer carrying arm structures; however, the stiffness of the PWB material is very low, and does not affect the operation of the resulting device. 
     Next an immobilizing layer  300  is formed over the exposed copper material of the coils  284  and interconnects  296 , as shown if FIG.  12 C. The immobilizing layer may be, for example, photoresist or other suitable material. Finally, as shown in FIG. 12D, the carrier silicon wafer  286  and copper layer  288  are removed, for example, using a wet or dry chemical etching method or another technique. This completes the construction of piece-part C. 
     Thus, as seen in FIG. 13A, piece-part A  221 , piece-part B  223 , and piece-part C  225  are provided to enable the assembly of the final microactuator. With reference additionally now to FIG. 13B, piece-part A  221  is first assembled into piece-part C  225 , with the upstanding leg members  244 ,  246  and  260  inserted through the apertures  248  and  240 . The carrier material  300  (see FIG. 12D) is then removed. 
     Piece-part B  223  is then placed over the upstanding leg  244  of piece-part A  221  and against the copper elements of piece part C  225 , as shown in FIG.  13 C. As shown in FIG. 13D, the nickel-iron components  244  and  252  are then electrolytically flash plated to connect to form a single structure. The carrier material  284  (see FIG. 1C) is then removed. 
     Finally, the temporary immobilization material  274  (see FIG. 10E) is removed from piece-part A  221  to complete the microactuator structure  220 , as shown in FIG.  13 E. 
     Although the invention has been described and illustrated with a certain degree of particularity, it is understood that the present disclosure has been made only. by way of example, and that numerous changes in the combination and arrangement of parts can be resorted to by those skilled in the art without departing from the spirit and scope of the invention, as hereinafter claimed.