Abstract:
A read head is disclosed having a unitary formation of multiple elements for reading multi-track data from a magnetic tape. Included are a number of elements joined together in a matrix, where each element includes two electrical leads and a sensor. Each lead which is not the first lead in the matrix or the last lead in the matrix is simultaneously a member of a first element and a second element. Also included is are a positive terminal and a negative terminal for attaching to a current source. Also disclosed is a magnetic tape storage device having a read head having a unitary formation of multiple elements.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally to read and write heads for magnetic tape recorders and particularly to recorders of high density information on magnetic tape  
         [0003]     2. Description of the Prior Art  
         [0004]     Although magnetically recorded disks have largely surpassed magnetic tape as the preferred storage media for computers, magnetic tape is still used and is subject to the same quest for improved storage capacity that motivates the entire computer industry.  
         [0005]     Magnetic tape drives operate by passing magnetic tape across a tape recording head which includes a plurality of tape writing elements and tape reading elements. A typical tape drive includes an actuator means for moving the tape head laterally relative to the longitudinal axis of the tape, such that the tape head reading and writing elements may access different data tracks on the magnetic tape, and a typical magnetic tape may have many data tracks written on it. A typical magnetic tape also includes a plurality of servo tracks that are written onto the tape during manufacturing, and which are used by the tape drive for tape head alignment and control purposes.  
         [0006]     As the demand for increased storage goes on, the number of tracks recorded on a width of tape has increased from 8 to 16 to 32 and beyond. As the width of the tape used is fairly standardized, the reading and recording elements must become smaller and closer together in order to increase the number of tracks. This makes precise alignment increasingly crucial to prevent read/write errors. The tape medium additionally experiences a difficulty not experienced by disk media, namely that it stretches. With the increasing density of data storage upon the tape, the chances for read/write errors as stretched tape misaligns with the read heads are thus increased.  
         [0007]     Increased storage density and precise alignment of heads involve several parameters that are crucial. Traditional tape read heads are composed of a number of discrete elements that are configured with a pair of electrical leads for each track, as shown in  FIG. 1  (prior art). For the sake of this discussion, the read head  1  will be considered to be composed of a number of elements  2 , of which each element  2  includes a sensor  4  between two electrical leads  3 . There are thus a total of four elements shown for example in the read head  1  of  FIG. 1 . The track width  5  is shown as width of the sensor  4 , which corresponds also to the distance between each of the two electrical leads  3 . The element pitch  6  is defined as the distance measured from the center line  7  of each track  8 . In the traditional design, the discrete elements  2  are separated by a spacing gap  9 , which contributes to the width of the element pitch  6 .  
         [0008]     This traditional design has several disadvantages. As dimensions of the elements  2  become smaller, the resistance of the leads  3  relative to the resistance of the elements  2  becomes higher, and the likelihood of element-to-element shorting becomes higher. Also, as referred to above, stretch by the tape can be a problem, and it is a problem with complexities. In a tape having wider tracks which are spread out across the width of the tape, when there is a side-to-side stretch of the tape, it can be assumed that the stretch will be approximately proportional across it length, so that each track will be displaced a proportionate amount and thus misaligned from the tape read head by this proportionate amount. In newer designs of tape read heads however, there are more tracks closer together. When this tape is stretched, each track is displaced by a smaller distance and consequently, the tracks are less misaligned than in the previous style where the tracks are more spread out  
         [0009]     Thus there is a need for a read head in which the sensor elements are not individual and discrete, in which spacing gaps between elements are not required, and which can be fabricated in very small dimensions without creating relatively high resistance in the electrical.  
       SUMMARY OF THE INVENTION  
       [0010]     A preferred embodiment of the present invention is a read head having a unitary formation of multiple elements for reading multi-track data from a magnetic tape. It includes a number of elements joined together in a matrix, where each element includes two electrical leads and an MR sensor. Each lead which is not the first lead in the matrix or the last lead in the matrix is simultaneously a member of a first element and a second element. Also included are a positive terminal and a negative terminal for connecting to a current source.  
         [0011]     Also disclosed is a magnetic tape storage device having a read head with a unitary formation of multiple elements.  
         [0012]     It is an advantage of the present invention that multiple elements are combined into a single multi-tap head.  
         [0013]     It is another advantage of the present invention that fabrication can be performed more easily at smaller and smaller dimensions.  
         [0014]     It is a further advantage of the present invention that less stringent processing is required during fabrication.  
         [0015]     It is yet another advantage of the present invention that electrical leads with lower resistance are allowed and that issues of element-to-element shorting are eliminated.  
         [0016]     It is an additional advantage of the present invention that data tracks may be reduced in size and positioned close together, so that stretching of the tape produces fewer errors.  
         [0017]     It is an advantage of the present invention that tracks widths and locations can be established by a unified matrix of elements rather than by an assemblage of individual elements where the center-to-center spacing may be harder to control precisely.  
         [0018]     These and other features and advantages of the present invention will no doubt become apparent to those skilled in the art upon reading the following detailed description which makes reference to the several figures of the drawing.  
     
    
     IN THE DRAWINGS  
       [0019]     The following drawings are not made to scale as an actual device, and are provided for illustration of the invention described herein.  
         [0020]      FIG. 1  is a top plan view of a read head of the prior art;  
         [0021]      FIG. 2  is a top plan view of a read head of the present invention;  
         [0022]      FIG. 3  is a cross-sectional view of a read head of the present invention;  
         [0023]      FIG. 4  is a circuit diagram of a measurement circuit used to read data by the read head of the present invention;  
         [0024]      FIG. 5  is a cross-sectional view of a first stage in the fabrication process, as taken through line  5 - 5  in  FIG. 6 ;  
         [0025]      FIG. 6  is a top plan view of a first stage in the fabrication;  
         [0026]      FIG. 7  is a cross-sectional view of the next stage in the fabrication process, as taken through line  7 - 7  in  FIG. 8 ;  
         [0027]      FIG. 8  is a top plan view of the next stage in the fabrication;  
         [0028]      FIG. 9  is a cross-sectional view of the following stage in the fabrication process, as taken through line  9 - 9  in  FIG. 10 ;  
         [0029]      FIG. 10  is a top plan view of the following stage in the fabrication;  
         [0030]      FIG. 11  is a cross-sectional view of a next stage in the fabrication process, as taken through line  11 - 11  in  FIG. 12 ; and  
         [0031]      FIG. 12  is a top plan view of a next stage in the fabrication.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]     The present invention is a tape head having unitary formation of multiple elements, which will be designated by the element number  10 . The inventive features of the present invention may be best appreciated by a comparison with discrete element tape heads of the prior art as shown in  FIG. 1 .  
         [0033]     Traditional tape heads are composed of a number of discrete elements that are configured with a pair of leads and a sensor for each track, as shown in  FIG. 1  (prior art). For the sake of this discussion, the tape read head  1  will be considered to be composed of a number of elements  2 , of which each element  2  includes a sensor  4  and two leads  3 . There are thus a total of four elements shown for example in the read head  1  of  FIG. 1  which make up the head  1 . The track width  5  is shown as the width of the sensor  4 , which also corresponds to the distance between each of the two electrical leads  3 . The element pitch  6  is defined as the distance measured from the center line  7  of each track  8 . In the traditional design, the discrete elements  2  are separated by a spacing gap  9 , which contributes to the width of the element pitch  6 .  
         [0034]     The present invention has a number of elements which have been fabricated as a unitary structure. The term unitary structure shall be used for purposes of this discussion to mean that the elements are formed together as one electrically connected structure, rather than fabricated as electrically separated elements as is practiced in the prior art. The present tape head having a unitary structure of elements, will be referred to as a unitary read head  10 , and is shown in  FIGS. 2 and 3 . The unitary read head  10  is again considered to be composed of a number of elements  12  which have been fabricated together to form an element matrix  60 .  
         [0035]     These elements  12  each include a sensor  14 , and two electrical leads  13 . It will be noted that an electrical lead  13 , such as example lead  16  can be a member of both a first element  18  and a second element  20 , as shown. The unitary read head  10  is supplied with a constant current source  22  (see  FIG. 4 ), which is connected between the positive terminal I+  24  and the negative terminal I−  26 . The voltages on the various leads  13  are designated as V 1 -V n , and the figure is shown as being abbreviated after V 3  to indicate that the number of leads  13  and thus of elements  12  is not limited to the number shown, and may extend to number 32 elements or more. Voltage measurements are taken between any particular lead, designated as Vi  28  and the next lead to it, designated as Vi+1  30 . This method provides isolated resistance measurements for the “ith” element  32 . For example, the track between V 2  and V 3  is shown as being this “ith” element  32 , thus V 2  becomes lead Vi  28  and V 3  becomes Vi+1  30  for purposes of this example. Between I+  24  and the 1 st  voltage lead  34 , designated V 1 , there may be a first bridge portion  36 , and between I−  26  and the last voltage lead  35 , designated Vn, there may be a second bridge portion  38 .  
         [0036]      FIG. 2  also includes track width  55  is shown as the width of the sensor  14  and thus the distance between each of the two leads  13 . The element pitch  56  is the distance as measured from the center line  7  of each track  58 . It can be seen in comparing the relative widths of the element pitch of the present invention  56  and the prior art  6  that the element pitch  56  of the present invention is narrower, as allowed by the grouping of the elements onto a single matrix  60 . By electrically connecting the elements together, they can be fabricated with a closer spacing, or pitch  56 , than that allowed when elements are fabricated so as to be electrically isolated.  
         [0037]      FIG. 3  shows a top plan view of the unitary read head  10  in the larger context. Leads I+  24  and I−  26 , for connection to current source  22  ( FIG. 4 ) are shown, as well as leads  13  including V 1 -V n . This unitary read head  10  is sandwiched between a first gap layer G 1   40  and a second gap layer G 2   42 . These in turn are sandwiched between a first shield layer S 1   44  and a second shield layer S 2   46 . Again, the figure is shown as being abbreviated after V 3  to indicate that the number of electrical leads  13 , and sensors  14  and thus of elements  12  is not limited to the number shown, and may extend to number 32 elements or more. A first bridge portion  36  and a second bridge portion  38  are also again shown.  
         [0038]      FIG. 4  shows a circuit diagram of a measurement circuit  15  used to read data detected by the sensors  14 . Source current I s  is provided by the current source  22 . Leads  13  are modeled as the taps  17  on either side of the sensors  14 , modeled in the diagram as resistors  19 . Data is read by the various sensors  14  as they pass over the tape as a changing voltage which is read by a measurement current I m  in a series of detectors  21 , (of which only one is shown) each of which is connected in parallel with the sensor  14 . The detected change in current is then interpreted as data bits by the central processor (not shown).  
         [0039]      FIGS. 5-12  show stages in the fabrication of the unitary read head  10 . It will be noted that the figures are presented in pairs, with the first being a cross-sectional view of the second, so that, for example,  FIG. 6  is a top plan view of a first stage in the fabrication process, and  FIG. 5  is a cross-sectional view as taken through line  5 - 5  in  FIG. 6 . The figures will therefore be discussed in pairs.  
         [0040]      FIGS. 5 and 6  show a first shield layer S 1   44 , upon which a first insulation layer G 1   40  has been fabricated. The MR sensor material layer  70 , from which the sensors will be formed, is deposited on the insulation layer  40 . This MR sensor material layer  70  is made of a number of layers, but are shown here as one layer for simplicity. The MR sensor material layer  70  is formed on a continuous substrate layer  50 , which provides unitary positioning and location for the finished sensors and elements, to be discussed below. In this case, the continuous substrate layer  50  is the first gap layer  40 .  
         [0041]     Photoresist material  72  is deposited on the sensor material layer  70  and has been patterned into masks  74 . As is well known in the art, these masks  74  shield protected portions  78  of the sensor material layer  70  and leave exposed portions  80  to be shaped by fabrication processes. In the top plan view of  FIG. 6 , only the masks  74  and exposed portions  80  of the sensor material layer  70  are visible.  
         [0042]      FIGS. 7 and 8  show the effect of ion milling to pattern the sensor material  70  to form the MR sensors  14  of the read head. It will be understood that although only five sensors are shown in the figure for simplicity, the number in practice will likely be a power of two, such as 32 or 64, etc., although this is not to be considered a limitation. In the top plan view of  FIG. 8 , only the masks  74  and insulation material  40  is now visible.  
         [0043]      FIGS. 9 and 10  show the deposition of the hard bias and lead material  76 , from which the electrical leads  13  will be formed (see  FIG. 2 ). The lead material  76  covers the insulation material  40  and the masks  74 . The top plan view of  FIG. 10  shows only hard bias/lead material  76  covering all. This material serves the dual purpose of providing electrical connection to the elements and serving to provide a magnetic hard bias to the sensor material, thus the material is designated as hard bias/lead material  76 .  
         [0044]     In  FIGS. 11 and 12 , the masks  74  and excess lead material  76  have been removed, leaving the sensor material  70 , now formed into sensors  14  exposed. The top plan view of  FIG. 12  shows the alternating electrical leads  13  and sensors  14  which make up the unitary read head  10 . At this point, the matrix of leads  13  has been established, with the electrical leads  13  interleaved with the MR sensors  14  to make the unitary read head  10 .  
         [0045]     While the present invention has been shown and described with regard to certain preferred embodiments, it is to be understood that modifications in form and detail will no doubt be developed by those skilled in the art upon reviewing this disclosure. It is therefore intended that the following claims cover all such alterations and modifications that nevertheless include the true spirit and scope of the inventive features of the present invention.