Abstract:
The structure for a closely spaced, coplanar tape head array is disclosed. Narrow pitch is obtained by utilizing an orthogonal backgap structure, wherein the width of the backgap is less than the depth, thereby narrowing the footprint of individual head structures. The increased cross sectional area of the orthogonal backgap and revised yoke design ensure sufficient magnetic field strength at the write gap of each head.

Description:
REFERENCES TO PRIOR APPLICATIONS  
       [0001]     This application is related to co-pending provisional application, reference No. 60/609,017, filed Sep. 9, 2004, entitled NARROW PITCH TAPE HEAD ARRAY USING AN ORTHOGONAL BACKGAP; co-pending provisional application, reference No. 60/609,009, filed Sep. 9, 2004, entitled HEAD DESIGN WITH OVERLAPPING COIL FOR NARROW PITCH TAPE HEAD; and claims benefit of both thereof. Provisional applications Nos. 60/609,017 and 60/609,009 are hereby incorporated by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates to the construction of magnetic media read and write heads. More specifically, the invention relates to the construction of multi-layer tape head arrays having a narrow pitch.  
         [0004]     2. Description of the Related Art  
         [0005]     A typical tape head consists of an array of writers and readers dispositioned across a row fabricated by thin-film wafer technology. The separation between adjacent elements in an array has constraints. Consequently adjacent elements stretch across multiple tracks written in the tape. Read and Write access to all tracks is achieved by indexing the array across the tape.  
         [0006]     One limitation on the separation between elements is to allow space for a wide coil on each write head. The width of the coil is constrained by magnetic requirements on the backgap size, number of turns and state-of-the-art coil photolithography. These limitation impose a separation much wider than the write track width and tape track pitch.  
         [0007]      FIG. 1  is a top view of a typical write head array  100  of the prior art, with insulating layers transparent to aid in viewing relevant details. Tape or other magnetic media contacts the head array at the air bearing surface (ABS)  112 . Write heads  102   a - 102   c  are located at a distance  122  from each other, which is about the width of five tracks in the example shown. Track position is determined by the center of write gap  110  of write head  102 . Track location diagram  114  shows the location of tracks  116   a - 116   c,  which correspond to the write track locations of heads  102   a - 102   c,  respectively. Distance  122  is primarily determined by the width  118  of backgap  106  in combination with the dimensions of coil  104 . Conventional backgaps  106  of the prior art are generally constructed with a width  118  of significantly larger dimension than the depth  120 . Yoke  108  returns the magnetic flux from write gap  110  to backgap  106 .  
         [0008]      FIG. 2  (prior art) is an air bearing surface (ABS) end view of tape head array  100  at section B-B in  FIG. 1 , with insulating layers  212  transparent to aid in viewing relevant details. Write heads  102   a - 102   c  are situated above shield layer  202  and insulating layer  204 , respectively. Bottom pole layer  206  is situated above insulating layer and is common for all writes heads in the array. Bottom pole tip  208  is coupled to bottom pole layer  206 . Upper pole tip  210  is separated from lower pole tip  208  by write gap  110 . Upper pole tip  210  is coupled to yoke  108 .  
         [0009]      FIG. 3  (prior art) is a cross section view through section A-A of  FIG. 1 , with insulating layers transparent to aid in viewing relevant details.  
         [0010]     U.S. Pat. No. 5,452,165 discloses a plurality of thin film magnetic heads which are arranged in a linear array with a spacing D between adjacent heads. The pole pieces of the magnetic heads are positioned in a side by side relationship in contrast to the normal pancake type of magnetic head. The linear array is angled at a skew angle theta with respect to the direction of travel of the magnetic medium. The track pitch is then D sin theta. The track width is substantially equal to the thickness of the pole tips P 1 T and P 2 T of the magnetic heads. This thickness can be in the order of 3 microns. With such a pole tip thickness the track pitch of each magnetic head in the linear array can be 3-4 microns. A plurality of narrow data tracks can then be provided with minimum pitch by a corresponding number of magnetic heads. The write signals are simultaneously fed to the heads or the read signals are simultaneously fed to the heads. This allows high data rates to be processed. The invention also provides different azimuth between adjacent heads to minimize cross talk between the tracks caused by track misregistration. Additional magnetic heads can be employed for servo control as needed.  
         [0011]     U.S. Pat. No. 5,546,650 discloses a method of manufacturing a thin-film magnetic head having a write element capable of producing a magnetic flux density sufficient to write the high coercivity magnetic tapes at high track density. The manufacturing process requires a minimum number of lithographic steps, thereby increasing the yield of the multiple track magnetic head module. A trench is cut into the ferrite substrate material and filled with an insulator to produce a more efficient write element. A recess is then formed in the ferrite substrate having a geometry sufficient to hold a deposited thin-film conductive coil below the surface of the ferrite substrate. An insulator is then deposited on the ferrite substrate to form a gap spacer as well as to insulate the conductive thin-film coils from the ferrite substrate. The conductive thin-film coil is then deposited on the ferrite substrate in the recesses. A high-saturation flux density magnetic material is deposited on a planar nonmagnetic closure section and formed into separate magnetic pole pieces for each individual track. The magnetic pole pieces are then insulated from each other to produce a closure section having a planar surface matable with the ferrite substrate. The closure section is attached to the substrate by aligning the metal pole piece on the closure section is attached to the substrate by aligning the metal pole piece on the closure section. The magnetic pole piece is positioned in the front gap and has a width which defines the track width on the magnetic tape. The magnetic pole piece is also positioned to substantially cover the back gap region to increase the flux density existing at the front gap region.  
         [0012]     U.S. Pat. No. 5,982,591 discloses integrated, juxtaposed head units of a magnetic head have transducing gaps directly adjacent a central plane transverse to the longitudinal direction of relative movement of a magnetic recording medium, adjacent transducing gaps being to opposite sides of the central plane. Head units adjoin each other so that a recording channel density of 100% is achieved. In one embodiment a common electrical conductor passes through a plurality of head units to one side of the central plane, and electrical connection tracks extending from a portion of the conductor form inductive transducing elements.  
         [0013]     U.S. Pat. No. 6,650,496 discloses a matrix array of recording heads, wherein each head is independent from another both in terms of its magnetic circuit and excitation conductors. Each individual head has a planar magnetic circuit and an helical coil wrapped around the lower part of the magnetic circuit. The matrix array is collectively fabricated using full thin film technology on non-magnetic substrates. Preferably, the heads are aligned in an oblique lattice with the write gaps aligned along rows and offset by a constant value along columns. Each individual head is connected to the control electronics through interconnects to the backside of the wafer, allowing independent control of the write parameters. The die forming the device is shaped on its edges and top surface to optimize head/medium positioning and minimize wear.  
         [0014]     U.S. Pat. No. 6,687,083 discloses a low profile inductive write head to improve track definition and head efficiency and to reduce overcoat and pole tip protrusion and cracking caused by thermal expansion. A first insulation layer of an insulation stack enclosing the coil layer is formed of an non-magnetic inorganic insulator material such as aluminum oxide, silicon dioxide or titanium dioxide having a thickness of in the range of 0.2-0.3 microns. The thinner first insulation layer results in a significantly reduced slope of the insulation stack which decreases reflective notching during processing of the second pole tip to improve track definition. Improved thermal conduction properties of the inorganic insulator material improves heat sinking of the write coil reducing overcoat and pole tip protrusion and cracking at the pole tip/write gap layer interface.  
         [0015]     U.S. Patent Application Publication 2002/0135918 A1 discloses a multi-magnetic recording head capable of increasing a magnetic recording density of information recorded on a magnetic recording medium. The multi-magnetic recording head includes a substrate, a pair of first thin film magnetic poles with a specific gap put therebetween, which are stacked over the substrate, and a pair of second thin film magnetic poles with a specific gap put therebetween, which are stacked over the pair of first thin film magnetic poles, wherein the pair of first thin film magnetic poles and the pair of second thin film magnetic poles are offset from each other in the direction nearly perpendicular to the stacking direction.  
         [0016]     U.S. Patent Application Publication 2004/0066576 A1 discloses a magnetic write head having a vertically laminated back gap structure and method of making the same. The magnetic head is formed with lower and upper pole pieces and a back gap structure which connects the lower and the upper pole pieces in a back gap region. In one illustrative example, the back gap is a vertically laminated structure having alternating layers of magnetic and non-magnetic materials. Each alternating layer is perpendicular to both the lower and the upper pole pieces. This vertically laminated structure significantly reduces the eddy currents in the back gap region at high operating frequencies as the layers are oriented in a direction parallel with the magnetic flux.  
         [0017]     U.S. Patent Application Publication 2002/0060879 A1 discloses a thin film magnetic head having a plurality of coils is capable of recording with higher density. A magnetic pole section for restricting a track width is formed between a lower core layer and an upper core layer, and two coil layers are tiered between a reference surface and a lower core layer through the intermediary of a coil insulating layer. This allows a magnetic path to be shortened. As a result, narrower tracks and lower inductance can be both achieved, and the narrower tracks combined with faster data transfer enable higher-density recording to be attained.  
         [0018]     Head arrays of the prior art having a relatively large spacing can exhibit a number of disadvantages. One is the possibility of track misregistration (TMR), which is an alignment or registration error from the first track position (i.e.  116   a ) to the last track position (i.e.  116   c ) due to expansion or contraction of the magnetic media. Magnetic media, particularly tape, can expand or contract as a function of temperature or humidity. The magnitude of this error is dependent on the total distance between the first and last head positions in the array, therefore the further the heads are apart, the greater the registration error. Another disadvantage of a widely spaced head array is that data write times can be longer for a given media width and number of tracks. Closely spaced heads produce arrays having more heads per unit media width, and therefore more tracks can be written in parallel, increasing total data rates to the storage media. This may be of considerable importance in computer data back-up applications, where large hard drives need to be backed up on tape media.  
         [0019]     In order to reduce adjacent head to head dimension  122 , some designs in the prior art have used a staggered head positioning, requiring adjacent heads to be located on different levels (when viewed in the ABS view). This construction can result in higher production costs, since proportionately more layers have to be added during fabrication.  
         [0020]     Of value would be an invention that allows a reduction of the spacing between the elements in the array while maintaining the same number of elements. Location of all elements within the same horizontal plane would be desirable to reduce fabrication costs.  
       SUMMARY OF THE INVENTION  
       [0021]     It is an object of the present invention to provide a magnetic head structure containing a lower pole, an upper pole, and a backgap structure magnetically coupling the lower pole and the upper pole. The backgap structure has a backgap depth greater than the backgap width.  
         [0022]     It is another object of the present invention to provide a magnetic head structure containing a lower pole including a lower pole layer magnetically coupled to a lower pole tip, an upper pole including a yoke magnetically coupled to an upper pole tip, a write gap disposed between the lower pole tip and the upper pole tip at an air bearing surface, and a backgap structure magnetically coupling the lower pole layer and the yoke. The backgap structure has a backgap depth greater than the backgap width.  
         [0023]     It is yet another object of the present invention to provide a magnetic head array containing a first magnetic head further containing a first lower pole including a lower pole layer magnetically coupled to a first lower pole tip, a first upper pole including a first yoke magnetically coupled to a first upper pole tip, a first write gap disposed between the first lower pole tip and the first upper pole tip at an air bearing surface, and a first backgap structure magnetically coupling the lower pole layer and the first yoke, the first backgap structure having a first backgap depth greater than a first backgap width. The magnetic head array further contains a second magnetic head including a second lower pole including the lower pole layer magnetically coupled to a second lower pole tip, a second upper pole including a second yoke magnetically coupled to a second upper pole tip, a second write gap disposed between the second lower pole tip and the second upper pole tip at the air bearing surface, and a second backgap structure magnetically coupling the lower pole layer and said second yoke, the second backgap structure having a second backgap depth greater than a second backgap width. The first magnetic head is adjacent to said second magnetic head.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     The present invention will be better understood when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings, wherein:  
         [0025]      FIG. 1  (prior art) is a top view of a typical write tape head array with insulating layers transparent;  
         [0026]      FIG. 2  (prior art) is an air bearing surface (ABS) end view at section B-B in  FIG. 1 , with insulating layers transparent;  
         [0027]      FIG. 3  (prior art) is a cross section view through section A-A of  FIG. 1 , with insulating layers transparent;  
         [0028]      FIG. 4  is a top view of a write head array having orthogonal backgaps, with insulating layers transparent, according to an embodiment of the present invention;  
         [0029]      FIG. 5  is an air bearing surface (ABS) end view at section D-D in  FIG. 4 , with insulating layers transparent, according to an embodiment of the present invention; and,  
         [0030]      FIG. 6  is a cross section view through section C-C of  FIG. 4 , with insulating layers transparent, according to an embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]      FIGS. 1-3  (prior art) have been discussed in the Background section above.  
         [0032]      FIG. 4  is a top view of a write head array  300  having orthogonal backgaps  306 , with insulating layers transparent to aid in viewing relevant details, according to an embodiment of the present invention. Head to head dimension  322  has been reduced by rotating the conventional backgap  106  by 90 degrees so that backgap  306  has a width  320  much less than width  120 , and a depth  318  much greater than depth  118  of the prior art design of  FIG. 1 . This allows compression of coil  304  and results in tighter head spacing. Backgap  306 , in combination with yoke  308 , provides adequate magnetic flux conductivity to write head gap  310  due in part to the larger cross sectional area of the backgap. The backgap  306  cross sectional area is roughly the width  320 × the depth  318 , which can be made equal to or greater than the conventional backgap  106  of the prior art. The shape of yoke  308  is also altered to enhance magnetic flux conductivity.  
         [0033]     In the example embodiment shown in  FIG. 4 , write heads  302   a - 302   c  are located to write tracks  316   a - 316   c  on the track diagram  314 . As shown, the head design of the present invention has a head to head spacing dimension  322  of three track widths. This is example is meant for illustration purposes, and does not imply any limitation on the actual head to head spacing achievable. Actual spacing would be determined by desired track widths and fabrication limits on coil geometry, such as those imposed by photolithography and metal deposition limitations.  
         [0034]      FIG. 5  is an air bearing surface (ABS) end view of tape head array  300  at section D-D in  FIG. 4 , with insulating layers transparent to aid in viewing relevant details, according to an embodiment of the present invention. Write heads  302   a - 302   c  are situated above shield layer  502  and insulating layer  504 , respectively. Bottom pole layer  506  is situated above insulating layer  504  and is common for all writes heads in the array. In an alternative embodiment (not shown), bottom pole layer.may be separated into discreet, isolated sections for each of heads  302   a - 302   c.  However, it is still desirable that these sections be located in the same plane above layer  504  to simplify construction and reduce fabrication costs. Bottom pole layer  506  is in contact with bottom pole tip  508 , and together comprise the lower pole. Upper pole tip  510  is in contact with yoke  308 , and together comprise the upper pole. The upper pole tip  510  and lower pole tip  508  are separated by write gap  310 , which is generally filled with a non-magnetic, insulator material. Upper pole tip  510 , yoke  308 , lower pole tip  508 , and lower pole layer  506  may be any suitable magnetic material, preferably one having a high magnetic moment such as Permalloy or various compositions of NiFe or CoFe alloys, which may contain dopants or other additives known by those of ordinary skill in the art to provide desirable material properties. The specific material compositions of the upper pole tip  510 , yoke  308 , lower pole tip  508 , and lower pole layer  506  may be different, in order to optimize the function of each component. Write gap  310  may be composed of alumina or other suitable non-magnetic material. Insulating material  512  may be composed of alumina, silica, baked photo-resist, or layers and combinations of any of the foregoing materials. Details are not shown for clarity.  
         [0035]      FIG. 6  is a cross section view through section C-C of  FIG. 4 , with insulating layers transparent to aid in viewing relevant details, according to an embodiment of the present invention. This view is taken through the center line axis of the write head perpendicular to the air bearing surface (ABS), and shows the extended depth  318  of the backgap  306  of the present invention. Backgap  306  is in contact with lower pole layer  506  and to yoke  308 , thus effectively magnetically coupling the upper and lower poles. Fabrication of the various structures  304 ,  508 ,  510 ,  310 ,  306 , and  308  are well known to those of ordinary skill in the art, and need not be covered in detail in this disclosure. Insulation  512  may be composed of various layers of different materials, deposited according to methods and processes well known to those skilled in the art.  
         [0036]     The present invention is not limited by the previous embodiments heretofore described. Rather, the scope of the present invention is to be defined by these descriptions taken together with the attached claims and their equivalents.