Combined thin film magnetic head and suspension system for longitudinal recording and method of making same
U.S. patent 4624048 to Hinkel et al, assigned to the assignee of the present invention and issued 25/11 1986, discloses a method of manufacturing a magnetic head substrate for use in the present invention.
U.S. patent 3849800 to Cuzner et al, assigned to the assignee of the present invention and issued 11/19 1974, discloses a rotary actuator for use in the drive of the present invention.
U.S. patent 4251841 to Jacobs, assigned to the assignee of the present invention and issued on 1981, 2, 17, discloses a wafer-shaped substrate material for use in the present invention.
The present invention relates to a movable magnetic memory and a recording element thereof, and more particularly to a sensor-suspension device suitable for mass production and a method of manufacturing the same,
removable magnetic storage, and in particular magnetic disk drives, are quickly becoming the memory of choice. Because it has an extensible permanent memory storage capability and a relatively low cost. It is critical to accurately retrieve the stored information from these memories, requiring that the sensor be located as close to the medium as possible, preferably with the transducer in contact with the medium.
A disc file is an information storage device that uses at least one rotatable disc having concentric data tracks containing data information. The sensor-slider-suspension combination includes a sensor for reading data from or writing data to each track; a slider for holding the sensor adjacent a magnetic track which normally flies through the medium; and a suspension device for elastically holding the slider and the sensor on the magnetic track. A positioner is attached to the assembly to move the transducer to the desired track and to maintain the transducer on the track centerline during reading or writing. The transducer is mounted on an air bearing slider that supports the transducer adjacent the track with an air cushion generated by the rotating disk. However, the transducer may be brought into contact with the disk. The suspension has high spring stiffness and dimensional stability between the slider and the lever. The suspension is required to hold the transducer and slider against the data surface of the disk with as low a loading force as possible. The actuator is controlled to position the sensor on the correct track for the data placement in accordance with the data desired for the read operation, or in the write operation.
In a general magnetic disk drive, the transducer and its slider are constructed separately from the suspension and then connected by precise manipulation under the control of an operator. The components are small and must be positioned accurately with respect to each other. The sensor must be located precisely on the magnetic track, and correspondingly, the suspension must be located precisely on the slider. The suspension must be resilient, pitch, and roll the slider in the direction of disk rotation, yet resist wobble. Any error in the placement of the suspension on the slider is detrimental to its performance and longevity. Even if the suspension and slider are properly positioned, the wires connecting the sensors must be connected to the sensors. The wires are typically routed directly along the levitation device and connected to an amplifier located on the levitation device or on the actuator. The wire, while providing a good electrical interconnection, certainly does not enhance the spring stiffness of the slider.
Typically, the wires are connected by the operator by soldering, for example, to both the output of the sensor and the amplifier. Again, errors can cause the entire combination to fail.
A particular problem caused by the sensor/slider combination or the head coming into contact or kiss with the media is causing media wear and possibly media breakage. To reduce the possibility of wear and "crushing", it is known that the volume of the suspension system must be minimized. The small volume allows for good control of the "crash" of the head on the media, thereby reducing the likelihood of damage and wear to the media.
To this end, a number of mechanisms have been disclosed which use a "reed" approach to making the sensor-suspension. In a configuration that operates in a perpendicular recording application, the reed device allows the head and suspension to be easily formed: precise throat height control; (ii) precise placement of contact registration sensors or by formation of air bearings to achieve a specified flying height; (iii) the slider is connected to the suspension, and (iv) the conductor path is easily determined. These structures, as described in Hamilton U.S. patent 5041932, for example, include a level sensor having a horizontal first pole piece and a horizontal second pole piece having a vertical portion that forms a magnetic gap spaced from the first pole piece.
As described above, contact recording can achieve higher signals and greater resolution without being limited by changes in flying height. Unfortunately, the wear from contact recording is typically estimated to be 400 microinches over the life of the document, which is not allowable. Another major drawback is that previously such heads were only suitable for perpendicular recording and not for longitudinal media. All of these make the perpendicular recording head of the above design unsuitable for high density recording.
It is an object of the present invention to provide an enhanced removable magnetic memory having a head structure including an enhanced suspension-sensor combination.
It is another object of the present invention to provide an enhanced suspension-sensor combination head structure.
It is a further object of the present invention to make a sensor-suspension structure suitable for longitudinal recording.
It is a further object of the present invention to produce a longitudinal magnetic head that is wear resistant and has a varying contact bump profile.
The invention is a combination of a suspension and transducer head for longitudinal recording, which can be used for contact recording or flying over a medium. The sensor comprises a horizontal first pole piece and a second pole piece with a cross section having a horizontal part and a vertical part. A magnetic gap is formed between the vertical portions of the first and second pole pieces. The pole pieces are shaped to avoid magnetic saturation and have narrow pole tips. The suspension consists essentially of two layers, the first layer being an insulating layer that separates the horizontal portions of the first and second pole pieces. The second layer is an insulating layer that covers and protects the sensor layer.
In a method of manufacturing a sensor-suspension combination, a plurality of patterned photoresist contact bumps are formed in a row and column configuration on a substrate. A separation layer is then deposited on the substrate. A first pole piece is patterned over each contact bump in partial contact therewith. A thick post-gap layer of magnetic material is deposited over each first pole piece. A thick layer of electrically and magnetically insulating material is deposited after the wear layer. This layer is the main part of the suspension member in the composite structure. The suspension layer is ground flat and a primary coil layer is formed on the suspension film for each pole piece. A second pole piece of magnetic material layer is deposited on the insulating layer corresponding to each first pole piece and at least partially covering the primary coil layer. The second pole piece layer is covered with an insulating layer but allowed to contact the primary coil. The coil circuit is then formed on the insulating layer along the wires that are connected to the coil circuit. The wires and subsequently deposited conductive plugs are used for connection to the drive circuitry (not shown) of each sensor. A second layer of electrically and magnetically insulating material is then deposited, forming the second and final major part of the suspended portion of the composite structure, the top of which is ground away to make electrical contact with the conductive plugs that have been formed. Since the assemblies are deposited in rows and columns on a circular substrate, each assembly is then divided into a number of rows of assemblies.
The ends of some of the row assemblies are polished and a magnetic gap layer is deposited. Contact vias are then formed in the magnetic gap layer, exposing the second pole piece layer. A third pole piece of magnetic material is pattern deposited over each row to form vertical portions of the second pole piece. A protective coating is then deposited over the rows of the finished suspension and sensor assembly. The rows of components are then divided into a number of individual composite structures. Subsequently, the substrate is removed by dissolving or etching the separation, leaving a partially fabricated composite structure. The air gap portion, the third pole piece and the final protective layer extending below the original contact are removed to complete the composite structure. Preferably, deposited alumina (Al) is used2O3) The layers form a suspension. The alumina layer is cut and the formed suspension is then separated from the substrate surface to form the desired suspension structure. The removal of the substrate is preferably accomplished using a release layer.
Longitudinal recording is possible because the present invention provides a narrow air gap between the poles on the contact bump surface. This greatly increases the applicability of the invention, making its range of application significantly beyond the prior art. Furthermore, the present invention is essentially a planar deposition structure, allowing the main processing of its components to be performed directly on a circular substrate surface. This greatly enhances the utility of the invention and enables mass production of the combination.
Another advantage of the present invention is the use of wear-resistant materials in the head structure to protect the pole head region of the magnetic head.
The foregoing and other objects, features and advantages of the invention will be apparent from the following detailed description of preferred embodiments of the invention, which proceeds with reference to the accompanying drawings. Wherein,
FIG. 1 is a top plan view of a magnetic recording mechanism using a suspension assembly of the present invention positioned by a rotary actuator in a transducing relationship with a disc surface of a disc document;
FIG. 2 is a perspective view of a transducer-suspension assembly made in accordance with the present invention for use with the disk drive of FIG. 1;
FIG. 3 is a perspective view of a substrate on which a plurality of structures arranged in rows and columns to form the assembly of FIG. 2 are formed;
FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3;
FIG. 5 is a perspective view of a row of structures taken from the substrate of FIG. 3 and mounted for further processing;
FIGS. 6A and 6B are cross-sectional views of embodiments of sensors according to the present invention; and
fig. 7 is a perspective view of a sensor of the present invention without insulating and conductive layers.
The preferred embodiment of the present invention is preferably used with a large plurality of disk drives, but may be used with a single disk drive, typically used with a personal microcomputer, or any other form of media drive, such as a tape drive. The data recording disc file shown in figure 1 comprises a housing 8 in which is mounted a orbiting actuator 10, an associated storage disc 12 and drive means 13 for rotating the disc 12. The rotary actuator 10 drives the assembly of the present invention in an arcuate path over the disc 12. The rotary actuator 10 comprises a voice coil motor including a coil 14 movable in the magnetic field of a stationary permanent magnet assembly having a plunger 16. Actuator arm 20 is fixed to moving coil 14. The other end of actuator arm 20 is attached to a sensor-suspension assembly 22 of the present invention and formed as described above. Assembly 22 includes a sensor-slider 24 and a levitation segment 26. Flying section 26 may support transducer slider 24 on the surface of disk 12 on an air bearing or cushion of air generated by the rotation of disk 12. Preferably, flying section 26 supports transducer-slider 24 in contact with the surface of disk 12. An air bearing or air bearing surface refers to a surface where the transducer is parallel to and adjacent to the surface of the disk. It includes two configurations, one designed to fly over the disk during operation and one designed to contact the recording medium, the disk 12, during operation. Actuator arm 20 may comprise a plurality of arms, each arm supporting its respective assembly 22, each assembly 22 corresponding to a surface of a respective disk in a data recording disk drive assembly. Thus, for example, disk 12 may also have a sub-assembly 22 mounted on actuator arm 20 so as to correspond to the surface of the recording medium on the lower surface of disk 12. In addition, other assemblies also correspond to the top and bottom sides of other disks included in the disk drive assembly. Access to the transducers in the disc drive assembly is controlled by an actuator 10.
Levitation section 26 in transducer-levitation device assembly 22 imparts a load to transducer-slider 24 that is always perpendicular to the surface of disk 12. This vertical load holds transducer-slider 24 on or above disk 12. During rotation of the disk 12 by the drive unit 13, the assembly 22 is held in contact with the disk 12 for reading or writing data. Alternatively, assembly 22 may be designed to fly above disc 12 by using the buoyancy or upward force generated between transducer-slider 24 and disc 12 to oppose the load applied to transducer-slider 24 by levitation section 26. Contact recording is a preferred embodiment of the present invention.
In operation, transducer-slider 24 is moved by means of coils 14 to desired ones of the concentric data tracks on the data surface of disk 12, with coils 14 moving in the magnetic field of the magnet assembly. The sensor-slider 24 is required to move rapidly from one track to another. The sensor of slider 24 must be positioned exactly on the desired track in the shortest amount of time. The rotary actuator used in the present invention is as described in US 3849800. It should be noted that the actuator 10 shown in fig. 1 is a rotary actuator, and other types of linear actuators used with conventional magnetic disk files can be used with the present invention.
The flyable section 26 of assembly 22 must have radial stiffness and be substantially resilient in pitch and roll directions when its transducer holding slider 24 is above the data surface of disk 12. An integrated circuit component 28 may also be fabricated on the suspended section 26 of the assembly 22, if desired. Reference numeral 28 designates an integrated circuit amplifier. An enlarged view of the assembly 22 of figure 1 is shown in figure 2.
Referring now to FIG. 2, in which like numerals represent like features and structural elements throughout the several views. The assembly 22 is shown on the disc 12. The disk 12 rotates in the direction indicated by arrow 36. Transducer 38 (shown in vertical pole cross-section) of transducer-slider 24 is positioned adjacent disk 12 for reading or writing magnetic transitions on disk 12. The level transducer-suspension assembly of the present invention is positioned parallel to disk 12 to facilitate the description of the present invention since most disk drives have a disk mounted horizontally. Obviously, a vertically mounted disk is equally covered, and in such an assembly the "horizontal" and "vertical" units must be reversed, but the transducers still run parallel to the disk surface.
The fly section 26 causes the transducer 38 to fly above the disc 12. The levitation section 26 in this embodiment includes a first insulation layer 40 and a second insulation layer 42. An electrically conductive circuit layer (not shown) is encapsulated between the two layers. The support body formed by the suspended segments is held by first and second insulating layers 40 and 42. The sensor 38 is electrically connected to the conductive circuit layer. Electrical connection conductor bumps 48 are provided to provide interconnection to adjacently located amplifiers. An integrated circuit amplifier (not shown) may be provided in place of the conductive bumps. The deposited integrated circuit amplifier of fig. 1 is one possible example of an amplifier arrangement.
Insulating layers 40 and 42 insulate the conductive layers from the potentially conductive magnetic portions of sensor 38. The two layers of insulation 40 and 42 provide a floating support for positioning the clamp transducer 38 over a track of the disk 32.
Figure 3 illustrates the process steps for forming the assembly 22 of the structure shown in figure 2. Batch fabrication of the assembly 22 is accomplished with a non-magnetic, circular substrate 50. The thickness T of the substrate 50 should be sufficient to support the structure under fabrication. A plurality of assemblies 22 are deposited in rows and columns on a substrate 50. Each row 52, shown as 5 rows, and each column 54, shown as 4 columns, illustrates the structure of the components making up the rows, which may then be subdivided into individual cells. More or fewer assemblies than shown in rows 52 and columns 54 of fig. 3 can be fabricated on a single substrate 50, with the number of assemblies that can be fabricated depending on the size of the substrate used and the size of the individual assemblies.
Still referring to fig. 3, a row 52A is cut from the substrate 50 with a saw 56. Row 52A has sensor portion 38 at end face 59. The row 52A is reprocessed as shown in fig. 5 and 6 and then separated into individual units by a saw 58 or other cutting method, as shown in fig. 3. Figure 4 shows a cross-sectional view of a deposited layer deposited on a substrate 50 as a first part of the assembly 22.
Referring now to FIG. 4, assembly 22 includes a number of layers that make up sensor-slider 24 and suspended segments 26. In cross-section, the level sensor contemplated by the present invention constitutes all or at least a portion of the sensor slider 24 shown in FIGS. 1 and 2. The transducer includes a first pole piece 62 that is positioned horizontally, i.e., parallel to the contact plane of the disk (not shown). The first pole piece 62 is formed with an inclined contact area 63. the inclined contact area 63 may be formed by embossing the surface of the primary substrate 50, as shown in fig. 4. The surface of the circular substrate 50 is coated with a release layer 60 prior to deposition of the material from which the pole piece 62 is made. The release layer 60 is dissolved away in a later process to separate the circular substrate 50 from the pole piece 62. A magnetic element 64 is deposited in connection with pole piece 62. After the magnetic element 64 is formed, the entire release layer 60 surface of the circular substrate 50 is coated with a layer of abrasion resistant material 65 and an insulating layer 66. Wear layer 65 covers a majority of the interface between sensor portion 24 and disk 12 (see FIG. 2). The wear layer 65 and insulating layer 66 are polished flat after deposition to provide a smooth surface for the subsequently deposited layers and to expose the top surface of the component 64. A first set of conductor strips 68 for the sensor coil is then formed on the insulating layer 66 and coated with a coil insulating layer 70 of electrically insulating material. A horizontal portion 72 of the second pole piece is then formed on the insulating layer 70. The second pole piece horizontal portion 72 contacts the magnetic element 64 to form the back air gap of the sensor. An additional layer of coil insulation 74 is deposited over the entire surface of the circular substrate. A second set of coil conductor strips 76 is deposited on the coil insulation layer 74. A second set of coil conductor strips 76 interconnects the first set of coil conductor strips and provides excitation conductor coils around the horizontal portion 72 of the second pole piece of the sensor section 24. The conductor strips 68 and 76 are electrically connected to a conductor layer 78 deposited on the conductor coil insulation layer 74 to form a coil. The coil is integral with the magnetic element of the transducer, allowing the transducer to read and write magnetically transduced information on the disk 12. Signals induced by the coil are fed into the circuitry (not shown) from the conductor layer via a conductor peg 80 formed at the free end of the conductor layer 78. A second electrically insulating layer 82 is deposited over the conductor coil strip 76 and the conductor layer 78. The second insulating layer 82 and the first insulating layer 66 are the support structure for the levitation section 26. Conductor bumps 48 (see fig. 2) are then formed on the second insulating layer 82 and connected to the conductor plugs 80. The conductor bumps 48 may be interconnected with corresponding disk drive circuitry by the integrated circuit 28 as shown in FIG. 1.
After the deposition process shown in fig. 4 is completed, the circular substrate 50 is cut into rows as shown in fig. 3. In fig. 3, row 52A is separated from circular substrate 50 by saw 56. The row 52A is then secured, for example, to a vehicle 90, see fig. 5, with adhesive, leaving the end face 59 of the row 52A exposed. The end face 59 of row 52A is then ground flat. The sensor is further processed into one embodiment shown in fig. 6A.
Referring now to FIG. 6A, the end face 59 of row 52A is lapped and a magnetic gap layer 92 is formed. The end face of the horizontal portion of the second pole piece is exposed and a vertical portion 94 is deposited. The second pole piece, indicated by reference numeral 96, includes its horizontal portion 72 and its vertical portion 94. Thus, the sensor portion 24 includes a second pole piece 96, see FIG. 4, the first pole piece layer 62 and the magnetic element 64 integral with the magnetic gap 92. After the vertical portion 94 is formed, a protective layer 98 is deposited. The structure of row 52A is now completed and ready for division into individual assemblies 22 for disks 12, see fig. 2. As shown in fig. 3, the saw 58 divides the row 52A containing the plurality of manufactured sensors into a number of individual units. The second type of vertical portion for the second pole piece 96 is shown in fig. 6B.
Referring now to FIG. 6B, the magnetic gap layer 92 is also first deposited on the end surface 59 of row 52A. The magnetic gap layer 92 is then polished to form an angle X with the vertical, exposing the end of the horizontal portion 72 of the second pole piece. The deposited magnetic material layer forms the vertical portion 99. The second pole piece, indicated by reference numeral 96, includes a horizontal portion 72 and a vertical portion 99. Thus, the sensor portion 24 includes the second pole piece 96, the first pole piece layer 62, and the magnetic element 64 integral with the magnetic gap 92. After the vertical portion 99 is formed, the protective layer 98 is deposited as described above, and as with the description of fig. 6A and 3, the row 52A has now been formed ready for division into individual components 22.
Referring again to fig. 4, the completed assembly 22, including the sensor portion 24 and the suspended portion 26, is disclosed with the substrate 50 by dissolving the release layer 60. The separation layer 60 may be copper plated. Another separation layer material may be tungsten. The copper separation layer can be easily removed, for example, with ammonium persulfate, without causing corrosion to the alumina substrate typically used in sensor fabrication. Once the assembly is made, it is readily applied to a hard disk readout system, as will be apparent to those skilled in the art.
The circular substrate 50 may be any suitable material known in the art. It is not required that the substrate 50 be alumina-titanium-carbide or silicon. The separation layer 60, which may be, for example, a conductive material, serves as a seed or plating base for a subsequently deposited layer, such as a first pole piece layer 62 of the sensor. The conductive material is preferably copper plated, but may also be gold or other suitable conductor. The wire 78 is routed along the suspended section 26 to a conductor plug 80. The wire should be formed as a strip line from two flat thin wires because the suspended section 26 is thin and the required stress symmetry is compatible with the strip line design. The suspended segment 26 is preferably fabricated by depositing alumina as the first and second insulating layers 66 and 62. As is known in the art, the conductive studs 80 and conductive bumps 48 are fabricated using standard conductive stud and conductive bump fabrication techniques to form a thin film sensor-suspension assembly. The sensor with the sheath 98 may be encapsulated with thick deposited alumina. For example, a thin layer of alumina may form the magnetic gap 92, for example, permalloy may be used as the magnetic material, forming the pole piece portion of the sensor. The shape of the sensor pole piece is shown in fig. 7. To show the preferred shape of the magnetic portion of the sensor of the present invention, the figure portion shows the coil and the sensor.
Referring now to fig. 7, a preferred embodiment of the present invention includes a sensor that combines the advantages of U.S. patent 4190872 to Jones, Jr et al, issued and assigned to the assignee of the present invention on 26.2.1980. The sensor includes a first pole piece layer 62 magnetically coupled to a horizontal portion 72 of the second pole piece at the back air gap 100 by a magnetic element 64. The vertical portion 94 of the second pole piece is magnetically connected to the horizontal portion 72 thereof and is separated from the first pole piece 62 by the magnetic gap 92. The first pole piece has a greater width at its rear air gap 100 than at its pole head 102. Likewise, the horizontal portion of the second pole piece has a greater width at the rear air gap 100 than at the end 104 that connects with the vertical portion 94. The perpendicular portion 94 has a width greater at the end connected to the end 104 of the pole piece 72 than the width of its pole head 106, and the preferred shape of the sensor is shown in fig. 7, which has a narrow pole head configuration but avoids saturation of the magnetic field lines along the pole piece.
Although the present invention has been shown and described in detail with reference to the preferred embodiments, it is to be understood that sensors may be fabricated on a substrate in the form described in the embodiment of U.S. patent 4190872 by one skilled in the art without departing from the spirit and scope of the invention, and that other configurations may be used without departing from the scope of the invention. The substrate may be made of a material as described in the subject matter of U.S. patent 4251841 to Jacobs et al, entitled "head slider," and assigned to the assignee of the present invention. The suspension according to the preferred embodiment may be a bi-layer material of a polyimide material and a metal layer deposited thereon to provide sufficient resiliency and stiffness for the suspension. Care must be taken if the single layer material has the appropriate thickness and strength. The suspension can also be made from a single layer of material. It should also be appreciated that there are many conductive materials that can be used for the conductive circuit and sensor leads. Copper and gold are preferred, but many other materials are suitable as is well known in the art. Although air-bearing levitation is described herein, the present invention also includes contact recording where a levitation device brings a sensor into contact with a recording medium. The following claims set forth the scope of the claimed invention.