Patent Publication Number: US-6700747-B2

Title: Integrated lead head suspension assembly having an etched laminated load beam and flexure with deposited conductors

Description:
REFERENCE TO RELATED APPLICATION 
     This application is a divisional of application Ser. No. 09/003,186 filed on Jan. 6, 1998, now U.S. Pat. No. 5,924,187 and which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present invention relates generally to suspensions for supporting read/write heads over recording media. In particular, the present invention is an integrated lead head suspension having a load beam etched from laminated sheets of material and a flexure additively fabricated by depositing conductors on a base layer. 
     2. Background of the Invention 
     Head suspensions are well known and commonly used with dynamic magnetic and/or optical storage devices or drives with rigid disks. The head suspension is a component within the disk drive which supports a read/write head over a desired position on the storage media (typically a data track on a spinning, rigid disk) where information is to be retrieved or transferred. A head suspension includes a load beam having a flexure to which a head slider having a read/write head is to be mounted. 
     The load beam includes a mounting region at a proximal end, a rigid region adjacent to a distal end and a spring region between the mounting region and rigid region. The spring region is relatively resilient and provides a downward bias force at the distal tip of the load beam for holding the read/write head near the spinning disk in opposition to an upward force created by an air bearing over the disk. The head slider allows the read/write head to “fly” above the disk on this air bearing. The flexure is to allow pitch and roll motion of the head slider and read/write head as they move over the data tracks of the disk. Via the mounting region of the load beam, the head suspension can be mounted to an actuator arm for coupling the head suspension to a voice coil or other type of actuator. Both linear and rotary type actuators are known in the art. 
     Manufacturers of head suspensions face competing design considerations. On one hand, it is important that head suspensions have relatively low mass and be relatively flexible. This is necessary to allow the head slider and read/write head to fly closely above the surface of the spinning data disk (on the order of 0.1 μm) without colliding with the disk (“crashing”) and still allow for imperfections in the disk surface and/or variations in the air bearing on which the head slider is flying. Flexibility is particularly important in the sensitive spring and flexure areas. Also, when the actuator stops the head suspension over a particular data track to read or write information, the deceleration can cause an inertial shock in the head suspension which causes transient vibrations. Data cannot be stored or retrieved until these vibrations substantially subside. In general, the lower the mass of the head suspension, the lower the inertial shock and ensuing transient vibrations. Therefore, a lower mass head suspension can decrease data access times. Finally, a lower mass head suspension requires less energy for the actuator to move the read/write head over the data disk surface. This can be particularly important in systems in which low energy consumption is advantageous, such as battery powered computer systems. In sum, a lower mass head suspension can either decrease access times, use less energy, or both. 
     On the other hand, head suspensions carry electrical components. For example, electrical read/write signals must be transferred to and from the read/write head, across the head suspension, to processing electronics. Electrical conductors can be included on the head suspension to facilitate this transfer of signals. These conductors can consist of copper wires encapsulated in a plastic tubing or coated with a dielectric material. Such standard conductors can have a large effect on head suspension performance. For example, a standard conductor placed atop a thin suspension can more than double a spring region&#39;s stiffness and detract from the ability of a spring region to adjust to variations in the surface of the disk. The effect of standard conductors on a flexure region, the thinnest and most delicate spring in the head suspension, is even more pronounced. Further, electrical components such as conductors add mass to the head suspension. 
     To help alleviate the difficulties in including electrical components on the head suspension, it is known to form such electrical components integrally with the head suspension. Such head suspensions are known as integrated lead or wireless head suspensions. Various methods exist for manufacturing head suspensions in this way. 
     One such method involves an additive or deposition process wherein multiple layers of different materials are built up on a substrate layer by sputtering, plating, chemical vapor deposition, ion beam deposition, evaporation, photolithographic techniques or other known processes. For example, a substrate layer can be formed from a rigid material such as stainless steel, an intermediate layer can be polyimide or other dielectric, and an upper layer can be an electrical conductor such as copper and formed in strips extending between the desired locations on the head suspension. Such additive techniques are known in the art and disclosed in, for example, U.S. Pat. No. 5,454,158 for Method of Making Integral Transducer-Suspension Assemblies for Longitudinal Recording, issued to Fontana, et al. on Oct. 3, 1995 and U.S. Pat. No. 5,111,351 for Integrated Magnetic Read/Write Head/Flexure/Conductor Structure, issued to Hamilton on May 5, 1992. 
     Using additive methods it is possible to form relatively thin, and therefore, flexible and relatively low mass electrical components. As such, the head suspension on which such components are formed can remain relatively flexible and low in mass. However, using additive methods can be relatively expensive because the equipment used to carry out additive processes is designed to accommodate relatively small semi-conductor components. Thus, relatively larger head suspension components can be manufactured in only relatively small batches. Accordingly, using additive methods to manufacture relatively large quantities of head suspension components can become time consuming and expensive. 
     A second method for forming electrical components integrally with a head suspension involves a subtractive method in which the starting material has a plurality of laminated layers which are chemically etched or otherwise removed to form the electrical components. For example, the starting material can be a laminated sheet having a lower layer of stainless steel or other rigid material, a middle layer of dielectric such a polyimide, and an upper layer of electrically conductive material such as copper. The layers may be successively chemically etched using known methods to form electrical leads or other electrical components from the conductive layer which are insulated from the rigid layer by the dielectric layer. Such methods are known in the art and disclosed in U.S. Pat. No 5,598,307, issued Jan. 28, 1997 to Bennin for Integrated Gimbal Suspension Assembly, which is hereby incorporated by reference in its entirety. 
     At present, using subtractive methods, it is problematic to produce electrical leads or other components that are as thin, low mass, and flexible as those which can be produced using additive methods. However, it is generally less expensive to manufacture head suspension using subtractive methods. 
     It is evident that there is a continuing need for improved methods for fabricating head suspensions and/or parts thereof. In particular, electrical components formed integrally with the head suspension should be suitably thin, low mass and flexible and yet relatively cost effective to manufacture. 
     SUMMARY OF THE INVENTION 
     The present invention is an integrated lead head suspension having a load beam and a flexure. The load beam is formed from a laminated sheet having a rigid base layer and an electrically conducting layer. The load beam includes a mounting region at a proximal end, a rigid region adjacent to a distal end, and a spring region between the mounting region and the rigid region. Electrical conductors are formed on the load beam by etching the electrically conducting layer. The flexure is for supporting a head slider and is formed by depositing electrical conductors over a base layer. The flexure is attached to the distal end of the load beam and the electrical conductors of the flexure are electrically interconnected with the electrical conductors of the load beam. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a bottom isometric view of a head suspension mounted to an actuator arm, the head suspension including a load beam and flexure and having integrated lead conductors formed thereon in accordance with the present invention. 
     FIG. 2 is a bottom view of the head suspension shown in FIG.  1 . 
     FIG. 3 is a bottom view of the load beam shown in FIG.  1 . 
     FIG. 4 is a bottom view of the flexure shown in FIG.  1 . 
     FIG. 5 is a sectional view of the load beam shown in FIG. 1 taken along section line  5 — 5  of FIG.  1 . 
     FIG. 6 is a sectional view of the flexure shown in FIG. 4 taken along section line  6 — 6  of FIG.  4 . 
     FIG. 7 is a side view of a sheet of laminated material from which the load beam shown in FIG. 1 can be fabricated. 
     FIG. 8 is a side view of a sheet of material which can be used in forming the flexure shown in FIG.  1 . 
     FIG. 9 is a side view of a built up laminated sheet having two layers which can be used in forming the flexure shown in FIG.  1 . 
     FIG. 10 is a side view of a built up laminated sheet having three layers which can be used in forming the flexure shown in FIG.  1 . 
     FIG. 11 is a side view of a built up laminated sheet having  4  layers which can be used to form the flexure shown in FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     Head suspension  6  in a first embodiment of the present invention, is shown in an isometric view in FIG.  1 . Head suspension  6  includes a load beam  12  having a base or mounting region  14  on a proximal end, a relatively rigid region  22  adjacent to a distal end, and a radius or spring region  18  between the mounting region  14  and rigid region  22 . Head suspension  6  also includes a flexure  16  at the distal end of load beam  12  for supporting a head slider (not shown) having a read/write head. Head suspension  6  is mounted to an actuator arm  8  for attachment to an actuator (not shown). Though not required in the embodiment shown in FIG. 1, it is contemplated that a base plate (not shown) can be mounted to mounting region  14 . 
     The spring region  18  of the load beam  12  typically includes a formed bend or radius. This radius provides the spring or load force and thus a desired load to a head slider for a predetermined offset height, the offset height being a measurement of the distance between the mounting surface of the head suspension at the actuator arm and the air bearing surface of the head slider at “fly” height, which is the distance above the surface of a spinning disk at which the head slider moves when transferring data to and from the disk. 
     A resilient connection is provided between the head slider and the distal end of the load beam  12  by the flexure  16 . Flexure  16  permits the head slider to move in pitch and roll directions so that it can compensate for fluctuations of a spinning disk surface above which the head slider “flies.” The illustrated embodiment of flexure  16  includes tongue  21  supported between spring arms  29   a  and  29   b  which extend from a mounting region  37  which is formed by a portion of the surface of flexure  16 . Flexure  16  also includes alignment apertures  60  and  62  in the mounting region  37  for alignment with load beam  12  when mounting flexure  16  thereto. Many different types of flexures, also known as gimbals, are known to provide the spring connection allowing for pitch and roll movement of the head slider and are contemplated to be used with the present invention. 
     Load beam  12  includes load beam electrical conductors  30 ,  32 ,  34 , and  36 , shown in FIG. 5, which is a section view of load beam  12  taken along line  5 — 5  of FIG. 1, extending from a location on a lateral edge  28  of actuator arm  8  to a location on the rigid region  22  of load beam  12 . At the lateral edge  28  of actuator arm  8 , electrical conductors  30 ,  32 ,  34 , and  36  terminate with electrical contacts  30   a ,  32   a ,  34   a , and  36   a , respectively. The opposite end of conductors  30 ,  32 ,  34 , and  36  terminate in the rigid region  22  with electrical contacts  30   b ,  32   b ,  34   b , and  36   b , respectively. At a location distal to the spring region  18 , conductors  30 ,  32 ,  34 , and  36  extend transversely across load beam  12  and off the load beam such that conductors  30 ,  32 ,  34 , and  36  primarily extend longitudinally adjacent to the radius region  18  rather than longitudinally thereover. Conductors  30 ,  32 ,  34 , and  36  then extend past the mounting region  14  and adjacent to actuator arm  8 . Conductors  30 ,  32 ,  34 , and  36  are attached to actuator arm  8  by tab  26 . 
     As shown in FIG. 5, a strip  27  of dielectric material extends beneath conductors  30 ,  32 ,  34 , and  36  and contacts  30   a ,  30   b ,  32   a ,  32   b ,  34   a ,  34   b ,  36   a , and  36   b  as they extend over load beam  12 . Strip  27  also supports electrical conductors  30 ,  32 ,  34 , and  36  in the regions where they extend off of load beam  12 . Strip  27  electrically insulates conductors  30 ,  32 ,  34 , and  36  and contacts  30   a ,  30   b ,  32   a ,  32   b ,  34   a ,  34   b ,  36   a , and  36   b  from load beam  12 . Tab  26  also extends from strip  27  in the region of contacts  30   a ,  32   a ,  34   a , and  36   a , for support thereof. 
     Flexure  16  includes flexure electrical conductors  40 ,  42 ,  44 , and  46 , shown in FIG. 4, extending from a proximal end of flexure  16  to a distal end thereof. Flexure electrical conductors  40 ,  42 ,  44 , and  46  terminate at the proximal end of flexure  16  with electrical contacts  40   a ,  42   a ,  44   a , and  46   a  and terminate at the distal end of flexure  16  with electrical contacts  40   b ,  42   b ,  44   b , and  46   b . As shown in FIG. 6, which is a sectional view of flexure  16  taken along line  6 — 6  of FIG. 4, a first strip  47   a  of dielectric material extends beneath flexure electrical conductors  40  and  42  and electrical contacts  40   a ,  40   b ,  42   a , and  42   b . Also, a second strip  47   b  of dielectric material extends beneath conductors  44  and  46  and contacts  44   a ,  44   b ,  46   a , and  46   b . Strips  47   a  and  47   b  merge into a single layer  47  of dielectric at the proximal and distal ends of flexure  16 . 
     Electrical contacts  30   b ,  32   b ,  34   b , and  36   b , are electrically connected to electrical contacts  40   a ,  42   a ,  44   a , and  46   a  by jumpers  50 ,  52 ,  54 , and  56 , respectively, shown in FIG.  2 . In this way, contacts  30   a ,  32   a ,  34   a , and  36   a , respectively, at the lateral edge  28  of actuator arm  8  are electrically connected to contacts  40   b ,  42   b ,  44   b , and  46   b , respectively, at the distal end of flexure  16 . A head slider (not shown) for supporting a read/write head (not shown) is to be mounted on flexure  16  and the read/write head is to be electrically connected to contacts  40   b ,  42   b ,  44   b , and  46   b . Accordingly, electrical read/write signals can be transmitted between the read/write head and contacts  30   a ,  32   a ,  34   a , and  36   a  located at the lateral edge  28  of actuator arm  8  via flexure electrical conductors  40 ,  42 ,  44 , and  46 , respectively, and load beam electrical conductors  30 ,  32 ,  34 , and  36 , respectively. 
     As noted above, flexure  16  provides for pitch and roll movement of the head slider attached thereto so that the read/write head can accurately follow the data tracks of a spinning storage disk over which the read/write head and head slider are “flying.” Typically, the head slider and read/write head fly extremely close to the disk on which information is stored. Manufacturers of disk drives currently strive to reach flying clearances close to 100 nm (0.1 μm). However, in most disk drives, the head assembly must not touch the disk (“crash”) since impact with the spinning disk (often rotating at 3600 RPM or faster) can destroy both the head, the surface of the disk, and the stored data. Imperfections on the surface of the rotating disk can make it even more difficult to avoid a crash of the head slider and read/write head into the disk. Accordingly, in order to avoid crashes, flexure  16  must remain relatively flexible so that it can fly close to the disk surface and quickly react to imperfections. 
     Further, if the mass of flexure  16  becomes too large, the inertial shock from stopping the read/write head over a data track can cause the read/write head to overshoot the correct data track and generate vibrations of flexure  16 . These vibrations then have to decay a certain amount before data can be reliably written or read from the data track. This can increase data storage and retrieval time. In general, to reduce the time for such vibrations to decay, flexure  16  should remain relatively light. Accordingly, flexure  16  and flexure conductors  40 ,  42 ,  44 , and  46  and contacts  40   a ,  40   b ,  42   a ,  42   b ,  44   a ,  44   b ,  46   a , and  46   b  are formed to be relatively thin and narrow such that they will be both relatively low mass and flexible and will thus have desirable dynamic characteristics. 
     To form flexure  16 , including distal conductors  40 ,  42 ,  44 , and  46  and contacts  40   a ,  40   b ,  42   a ,  42   b ,  44   a ,  44   b ,  46   a , and  46   b , to be relatively low mass and flexible, additive or sequential deposition fabrication methods such as known sputtering, evaporation, and/or photolithographic techniques are used. 
     Preferably, in one additive method for fabricating flexure  16  shown in FIGS. 8-12, a sheet  80  of stainless steel is coated and patterned with a standard photosensitive polyimide layer  82  as shown in FIG.  9 . As shown in FIG. 10, a seedlayer  84  of chromium or chromium and copper is then sputtercoated over the polyimide layer and coated and patterned with photoresist. A layer  86  of copper is plated thereon, as shown in FIG.  11 . The photoresist is stripped to form strip  47 , including strips  47   a  and  47   b , of polyimide coated with copper. The seedlayer  84  can then be etched to form conductors  40 ,  42 ,  44 , and  46  and contacts  40   a ,  40   b ,  42   a ,  42   b ,  44   a ,  44   b ,  46   a , and  46   b  which can be plated for protection thereof. Both sides of the stainless steel/polyimide/copper sheet are then coated with photoresist and exposed. The photoresist is developed, etched and stripped, to form tongue  21 , arms  29   a  and  29   b , and apertures  60  and  62  in sheet  80  of stainless steel. A dielectric cover coat is then preferably applied over flexure  16  including tongue  21 . The dielectric cover coat protects the electrical conductors  40 ,  42 ,  44  and  46 . In particular, the cover coat allows an electrical conductor or conductors  40 ,  42 ,  44  and/or  46  to be re-routed over the portion of tongue where  21  a head slider is mounted while preventing unintended direct contact, either electrical or otherwise, between the head slider and the re-routed electrical conductor or conductors  40 ,  42 ,  44 , and/or  46 . This allows routing of flexure electrical conductors as needed on tongue  21  to facilitate making of necessary electrical connections between flexure electrical conductors  40 ,  42 ,  44 , and  46  and a head slider supporting a read/write head. All of the above steps can be performed using conventional or otherwise known methods. Other standard additive methods known in the art can also be used to form flexure  16 . 
     Forming flexure  16  including flexure conductors  40 ,  42 ,  44 , and  46  and contacts  40   a ,  40   b ,  42   a ,  42   b ,  44   a ,  44   b ,  46   a , and  46   b  using the above described additive method or other known additive methods, allows flexure  16  to be relatively low mass and flexible. In this way, flexure  16  can possess desirable dynamic characteristics. 
     It is to be noted that the exact design of flexure  16  shown in FIGS. 1,  2 , and  4  is not critical to the present invention. Any design of a flexure having electrical components thereon and which can be manufactured using additive techniques is contemplated for use with the present invention. 
     Load beam  12  does not have the same dynamic requirements as flexure  16 . While it is desirable that load beam  12  be relatively low mass, it does not need to be as low mass as flexure  16 . Further, it is desirable that the rigid region  22  and mounting region  14  be relatively stiff. Also, it is desirable that the spring region  18  be resilient only in a direction normal to the planar surface of the load beam; allowance for pitch and roll motion of the read/write head and head slider is not necessary. As such, electrical components attached to load beam  12 , such as load beam conductors  30 ,  32 ,  34 , and  36  and contacts  30   a ,  30   b ,  32   a ,  32   b ,  34   a ,  34   b ,  36   a , and  36   b , can be less flexible and need not be as low mass as flexure conductors  40 ,  42 ,  44 , and  46  and contacts  40   a ,  40   b ,  42   a ,  42   b ,  44   a ,  44   b ,  46   a , and  46   b  attached to flexure  16 . Further, as shown in FIGS. 1,  2  and  3 , load beam conductors  30 ,  32 ,  34 , and  36  do not extend over the entire longitudinal length of spring region  18  but extend partially transversely across spring region  18  and off a lateral edge of load beam  12 . As such, conductors  30 ,  32 ,  34  and  36  have a reduced effect on the spring characteristics of load beam  12 . This makes the flexibility of conductors  30 ,  32 ,  34 , and  36  even less important to the mechanical performance of the load beam. In general, therefore, it is not as important to use components which are as low mass and flexible as those which can be produced using additive methods to produce desirable dynamic characteristics in load beam  12 . 
     Electrical conductors having greater cross sectional dimensions (that is, greater width and depth) can be desirable on load beam  12 . Conductors having greater cross sectional area have less electrical resistance per unit length. The lower the total electrical resistance of conductors  30 ,  32 ,  34 , and  36 , the lower the possibility of read/write signal degradation. Because load beam conductors  30 ,  32 ,  34 , and  36  extend over a greater distance than flexure conductors  40 ,  42 ,  44 , and  46 , it is advantageous for load beam conductors to have lower electrical resistance per unit length to reduce the possibility of read/write signal degradation. As noted above, additive methods can be relatively expensive to use in head suspension manufacture, and fabrication of larger electrical components using additive processes is commensurately more expensive. 
     Accordingly, load beam  12  is formed using subtractive methods, which can be less expensive than additive methods. Preferably, as shown in FIG. 7 load beam  12  of head suspension  6  can be formed from a laminated sheet  70  constructed of a first layer  72  of stainless steel overlaying a second layer  74  of polyimide overlaying third layer  76  of copper or copper alloy. Laminated sheets such as laminated sheet  70  are available from Rogers Corporation of Rogers, Conn. or NSCC (Nippon Steel Chemical Corp.) of Japan. Photoresist is applied to both sides of laminated sheet  70  and both sides are exposed. The photoresist on the third layer  76  of copper alloy is developed and etched to form electrical conductors  30 ,  32 ,  34  and  36  and electrical contacts  30   a ,  32   a ,  34   a ,  36   a ,  30   b ,  32   b ,  34   b , and  36   b . The photoresist on first layer  72  of stainless steel is then developed and etched to form the overall shape of load beam  12  and features of load beam  12  such as apertures. 
     The photoresist is stripped from both sides of sheet  70  and a dry film photoresist is applied to both sides of sheet  70 . The photoresist is exposed and developed and plasma etching techniques are used to form the second layer  74  of polyimide into strip  27 . A dielectric cover coat can then be applied to sheet  70  to protect the copper or copper alloy features. The above coating and etching processes can all be performed using conventional or otherwise known methods. To complete load beam  12 , edge rails can be bent up at the side of the rigid region. 
     It is also within the scope of the invention to form load beam  12  from a laminated sheet of material having greater or fewer than three layers. Further, any load beam design having electrical components thereon and which can be manufactured using subtractive techniques is contemplated for use with the present invention; it is not critical that the design of load beam  12  shown in FIGS. 1,  2 , and  3  be used. 
     Flexure  16  is attached to load beam  12  by adhesive, laser welding or other methods. Jumpers  50 ,  52 ,  54 , and  56  are soldered, laser welded, gold ball bonded, ultrasonic wedge bonded, hot bar reflow soldered, or otherwise adhered and electrically connected to contacts  40   a ,  42   a ,  44   a , and  46   a , respectively, and contacts  30   b ,  32   b ,  34   b , and  36   b , respectively, to electrically connect the two sets of contacts. Contacts  40   a ,  42   a ,  44   a , and  46   a  can also be electrically connected to contacts  30   a ,  32   a ,  34   a , and  36   a , respectively, by directly soldering the contacts, melting the contacts together, or using other known methods. Spring region  18  of load beam  12  can then be rolled to create the proper bias for head suspension  6  to allow a head slider and read/write head attached thereto to fly over the surface of a spinning disk at the correct height. Actuator arm  8  is formed of stainless steel or other rigid material and can be fabricated using known methods. Load beam  12  is mounted to actuator arm  8  by soldering, welding, adhesive, or other known methods. Tab  26  is connected to a lateral edge  28  of actuator arm  8  by welding, adhesive or other known methods. 
     By forming flexure  16  using additive methods and load beam  12  using subtractive methods, it is possible to optimize the manufacturing of a head suspension such as head suspension  6  having electrical components formed integrally therewith such as conductors  30 ,  32 ,  34 ,  36 ,  40 ,  42 ,  44 , and  46  and contacts  30   a ,  30   b ,  32   a ,  32   b ,  34   a ,  34   b ,  36   a ,  36   b ,  40   a ,  40   b ,  42   a ,  42   b ,  44   a ,  44   b ,  46   a , and  46   b . The flexure can be formed to have desirable physical characteristics such as low mass and flexibility while the load beam can be formed at a reduced cost while retaining important dynamic characteristics such as resiliency of the radius region. Further, because flexure  16  is relatively smaller than load beam  12 , a greater number of flexures such as flexure  16  can be fabricated in a single batch using additive methods than could load beams such as load beam  12 . Thus, is can be less expensive to manufacture only flexure  16  using additive methods than both load beam  12  and flexure  16 . 
     Though the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention.