Abstract:
In a magnetic head slider having a horizontal type head element which floats on or comes into contact with a recording medium, in which a portion  32  of the slider including the head element can be moved in a minute range in the tracking direction and the loading and unloading direction and is supported by a stationary section  31  forming a slider body via a support spring  34 , a leading wire  22  drawn out from the head element  43  is formed in the process of manufacturing the slider so that the motions of the movable section  32  of a microactuator with respect to the stationary section  31  are not obstructed. The lead wire  22  drawn out from the head element  43  mounted on the movable section  32  is composed of a flexible lead wire  22 , the rigidity of which is lower than that of the support spring  34 , and a leading wire (which is a flexible lead wire  22 ) is drawn from the movable section to the stationary section so that the movement of the movable section with respect to the stationary section is not restricted.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a magnetic head slider used for a magnetic disc unit. Also, the present invention relates to a method of forming lead wires inside the magnetic head slider, especially in a portion containing a microactuator. 
     In recent years, magnetic disc units have been made compact, their performance has been highly enhanced, and their cost has been reduced. In accordance with the recent tendency, it is desired to develop a thin film magnetic head of high performance and low cost. In order to meet the demand, a horizontal magnetic head (planar magnetic head) has been proposed in which a thin pattern forming surface is arranged in parallel with a flying surface. The reason is described as follows. In the case of a horizontal magnetic head, it is easy to form flying rails having specific shapes. Therefore, it is possible to realize a magnetic head capable of flying stably close to the disc surface, and further it is easy to reduce a portion to be machined in the manufacturing process. Therefore, the cost can be lowered. 
     In accordance with an increasing demand for enhancing the density of magnetic recording and also in accordance with an increasing demand for reducing the sizes of the head element and the magnetic head slider, problems occur in machining and handling. 
     2. Description of the Related Art 
     For the above reasons, the present inventors proposed a magnetic head slider which can be manufactured almost without being machined so that the manufacturing cost can be reduced. This magnetic head slider is disclosed in Japanese Unexamined Patent Publication No. 9-81924, the title of which is “Thin film magnetic head slider and electrostatic actuator”. A microactuator is incorporated into this magnetic head slider. Therefore, it is possible to accurately control the head element in the tracking direction and the loading and unloading direction. 
     The above prior art will be explained below. 
     FIGS. 1 and 2 are views showing a thin film magnetic head slider of the prior art. FIG. 1 is a perspective view of the slider  10  attached to the head suspension  30 , seen from the flying surface side. FIG. 2 is a perspective view of the slider  10 , seen from the back (opposite side to the flying surface) thereof, before the slider  10  is attached to the head suspension  30 . 
     A portion of the flying surface layer  11  made of SiO 2  or Al 2 O 3  protrudes onto the flying surface side of the slider  10  which is opposed to a recording medium not shown in the drawing. This protruding portion forms two flying rails  15  which extend from the leading end  13  to the trailing end  14  with respect to the recording medium moving in the direction of arrow A. On the leading end  13  side between the two flying rails  15 , there is provided a central rail  17 . Metallic plating of Ni is conducted on the main body  12  of the slider  10  formed on the back of the flying surface layer  11 , and also metallic plating of Ni is conducted on the terminal pad section  18  shown in FIG.  2 . 
     The electrostatic microactuator  20  (tracking mechanism) is formed in a portion of the flying surface  11  between the two flying rails  15  and also between the terminal pad  18  and the outflow end  14 . 
     Although the details are not shown in the drawings, the electrostatic microactuator  20 , which utilizes an electrostatic attraction force in its operation, is composed of a movable section and a stationary section. On a side of the movable section which is opposed to the recording medium, there is provided an element mount section. There are provided metallic electrodes between the movable and the stationary section in portions respectively opposed to each other. When voltage is impressed between the electrode on the stationary section side and the electrode on the movable section side, an attractive force is generated, and the head element is moved by the attractive force in a direction perpendicular to the track, and tracking is conducted. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a magnetic head slider, in which lead wires can be drawn from the head element, which is mounted on the movable station, to the stationary section (slider body) without interfering with movement of the microactuator, such as disclosed in the above Japanese Unexamined Patent Publication No. 9-81924. 
     According to the present invention, there is provided a magnetic head slider adapted to be opposed to a recording medium comprising: a medium opposing surface being in contact with or flying above a recording medium; a horizontal type head element having a head film which is parallel to said medium opposing surface; a movable section constituted by a part of said head slider including said head element, said movable section supported on a stationary section including a slider body by means of a support spring so as to be movable within a small limited range at least in a tracking direction or in a load-unload direction with respect to said recording medium; and a lead line extending from said head element mounted on said movable section and made of a flexible lead wire, said flexible lead wire extending from said movable section to said stationary section so as not to obstruct the movement of said movable section with respect to said stationary section. 
     As described above, the lead wires drawn out from the head element are composed of flexible lead wires, the rigidity of which is lower an that of the support spring. Therefore, movement of the movable section with respect to the stationary section is not obstructed by the lead wires. Further, the lead wires can be foamed simultaneously during the manufacturing process of the magnetic head slider. 
     The flexible lead wire comprises, in cross-section thereof, a conductor portion and a flexible insulator covering said conductor portion. Particularly, the flexible lead wire comprises three laminated layers including two, upper and lower, flexible insulating layers and a central conductor layer sandwiched between said two flexible insulating layers. 
     Due to the foregoing, the lead wires, the flexibility of which is sufficiently high, can be formed by means of patterning in the manufacturing process of the magnetic head slider. 
     The flexible lead wire comprising upper and lower flexible insulating layers and a conductor layer sandwiched between said two flexible insulating layers is substantially in parallel to said medium opposing surface. Also, the flexible lead wire has such a shape that it can be deformed within the same single surface or out of a single surface. In addition, the flexible lead wire is bent at least twice to form a U-shaped portion in the small space between the movable section and the stationary section. 
     The two, upper and lower, flexible insulating layers comprise a cured photoresist. The horizontal type head element comprises an information recording head element and a reproducing head element. 
     Due to the foregoing, the rigidity of the flexible lead wires can be further reduced. 
     According to another aspect of the present invention, there is provided a process for manufacturing a magnetic head slider, the process comprising: forming a sacrifice layer on a substrate; forming, on the sacrifice layer, a flying surface layer and a movable section including a head element layer and, in addition, forming a slider body defining a stationary section; and removing the sacrifice layer to separate the head slider from the substrate; characterized in that, after the flying surface layer and the movable section including the heat element layer are formed and before the slider body is formed, a lead line, which should be extended from the head element mounted on the movable section to the stationary section of the slider body, is formed by patterning. 
     Due to the foregoing, the formation of the lead wires can be conducted in the wafer patterning process when the slider is manufactured. 
     The lead line is formed in such a manner that: a first flexible insulating layer is patterned and hard baked; a conductor layer film is patterned on the first flexible insulating layer; and a second flexible insulating layer is patterned and hard baked on the conductor layer, so that said lead line comprises three layers including two, first and second, flexible insulating layers and a central conductor layer sandwiched between the two flexible insulating layers. 
     Due to the foregoing, it is possible to form flexible lead wires, the flexibility of which is high and the rigidity of which is low. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the conventional magnetic head slider, seen from the flying surface side; 
     FIG. 2 is a perspective view of the conventional magnetic head slider, seen from the back; 
     FIG. 3 is a plan view of the magnetic head slider of the present invention; 
     FIG. 4 is a plan view of the electrostatic actuator of the magnetic head slider of the present invention; 
     FIG. 5 is a cross-sectional view of the electrostatic actuator of the magnetic head slider of the present invention; 
     FIG. 6 is a cross-sectional view of a flexible lead wire; 
     FIGS. 7 to  16  are views showing a manufacturing process of the magnetic head slider of the present invention; wherein FIG. 7 shows a formation process of the sacrifice layer; FIG. 8 shows a formation of the flying surface layer; FIG. 9 shows a process in which the flying layer is made to be thick; FIG. 10 shows a formation process of the conductor layer (Au); FIG. 11 shows a process in which an additional sacrifice layer is formed; FIG. 12 shows the formation of the flexible lead wire; FIG. 13 is an enlarged view showing a primary portion of FIG. 12; FIG. 14 shows a formation of a plating base in the next process; FIG. 15 shows a state in which a magnetic head slider is formed on a sacrifice layer; and FIG. 16 shows a state in which a sacrifice layer is removed by etching and a magnetic head slider is completed; 
     FIG. 17 is a view showing another example of the magnetic head slider of the present invention; and 
     FIG. 18 is cross-sectional view showing the formation of a lead wire in the process successive to FIG.  17 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 3 is a plan view showing an outline of the magnetic head slider of the present invention. FIG. 4 is a plan view of the microactuator of the magnetic head slider. FIG. 5 is an enlarged cross-sectional view taken on line B—B in FIG. 4, wherein a lead wire portion drawn out from the head element is also shown in FIG.  5 . 
     As shown in FIG. 5, the entire magnetic head slider  10  is composed in such a manner that a plated layer of Ni, which is a slider body layer  42 , is provided on a layer of SiO 2  which is a flying layer  41 . 
     As shown in FIG. 4, the electrostatic microactuator  20  is fixed onto a substrate, not shown, when the stationary section  31 , the outer frame of which is formed by plating of Ni, is fixed to the substrate. On the inner wall of the stationary section  31 , there are provided teeth  31   a , which are arranged toward the inner circumference in parallel to each other at regular intervals, wherein these teeth  31   a  are formed by means of plating of Ni simultaneously with the formation of the stationary section  31 . These teeth  31   a  may be fixed onto the substrate or arranged such that a gap (not shown in the drawings) is left between the teeth and the substrate. 
     A central portion located inside the frame of the stationary section  31  is the movable section  32  which is formed by means of plating of Ni simultaneously with the formation of the stationary section  31 . The movable section  32  is arranged so that it can be relatively moved with respect to the stationary section  31  when a gap (not shown) is left between the movable section  32  and the substrate. In the movable section  32 , there are provided a plurality of teeth  32   a  at positions shifted from the centers of the teeth  31   a , which are arranged in parallel to each other in the stationary section  31 , and these teeth  32   a  are arranged in parallel to the teeth  31   a . 
     In the drawing, at an upper portion and a lower portion of the movable section  32 , there are provided supports  33  fixed to the substrate, and also there are provided support springs  34 , by which the movable section  32  can be moved in the upward and downward direction in the drawing and also in the direction perpendicular to the surface of the drawing, between the supports  33  and the movable section  32 . A head element (not shown) formed in the movable section  32  can be moved in the tracking direction, which is the upward and the downward direction in the drawing, and in the loading and unloading direction, which is a direction perpendicular to the drawing, by the action of the substantially C-shaped support springs  34  arranged at the four corners of the movable section  32 . 
     In the drawing, lead wires  35 ,  36  to be connected to terminals, not shown in the drawings, are formed by means of plating of Ni at the right lower portion of the stationary section  31  and at the support on the lower side. 
     When voltage is impressed between the two lead wires  35 ,  36 , an electrostatic attraction force generated between the teeth  31   a  of the stationary section  31  and the teeth  32   a  of the movable section  32 . The movable section  32  is attracted upward by this electrostatic attraction force and is moved to a position at which the electrostatic attraction force is balanced with a restoring force of the support spring  34 . In order to prevent the occurrence of a short circuit of the teeth  31   a  of the stationary section  31  with the teeth  32   a  of the movable section  32  when an excessively high voltage input is given, a stopper is arranged in a portion of the support  33  by reducing a gap between the support  33  and the movable section  32 . A cross section of the support spring  34  is determined as follows. For example, the width is 5 μm, the heigth is 5 μm, and the length is 100 μm. 
     As shown in FIG. 3, there are provided bent lead wires  22  at the four corners of the movable section  32 . Only two bent lead wires  22  are arranged on the lower side shown in FIG.  4 . The shape of the flexible lead wire  22  is formed in such a manner that two U-shape are connected with each other in a space between the movable section  32  and the stationary section  31 . Therefore, the rigidity in the upward and the downward direction in the drawings is low, and also the rigidity in the direction perpendicular to the surface of the drawing is low. The flexible lead wires  22  electrically connect the head element  43  (shown in FIG.  5 ), which is arranged on the movable section  32 , with the terminals  18  (shown in FIG.  3 ), which are arranged on the slider body. 
     As shown in FIG. 5, the electrostatic microactuator  20  is composed of a plated layer of Ni which is thinner than the slider body  42  including the support spring  34  (not shown in FIG.  5 ). 
     FIG. 6 is a cross-sectional view of the flexible lead wire  22 . As shown in the drawing, the flexible lead wire  22  is composed in such a manner that the conductor layer  23  is sandwiched between the upper flexible insulating layer  24  and the lower flexible insulating layer  25 . The thickness of the flexible lead wire  22  is sufficiently thinner than that of the support spring  34  that supports the movable section  32  so that the motion of the movable section  32  cannot be affected by the rigidity of the flexible lead wire  22  itself. For example, the thickness of the flexible lead wire  22  is determined to be 0.1 μm. The width is not more than that of the support spring  34 , for example, the width of which is 2 μm. Therefore, even the total rigidity of the four flexible lead wires  22  is sufficiently lower than the rigidity of support spring  34 . Accordingly, motion of the movable section  32  is not obstructed by the flexible lead wires  33 . 
     Since the flexible lead wire  22  is covered with the insulating layers  24 ,  25  from the upper and the lower sides, it is possible to arrange the flexible lead wire  22  to come into contact with the movable section  32  and the stationary section  31 . In the case of an inductive head, the head element  43  mounted on the movable section  32  has two terminals. When MR head is used for reading, two terminals (not shown) are further added. These terminals are connected to the terminal section  18  via the flexible lead wire  22 . Due to the above arrangement, it is possible to draw out the lead such as signal wires from the head element  43  arranged in the movable section  32 . 
     Next, referring to FIGS. 7 to  16 , a formation process of the magnetic head slider  10  of the present invention, especially, a formation process of its eletrostatic microactuator  29 , will be explained below. 
     (1) A sacrifice layer (Al layer)  51  is formed on the overall surface of the glass substrate  50 . This sacrifice layer is provided for separating the slider  10  from the substrate  50  by etching. Next, a head element  43  composed of a magnetic film is formed at a predetermined position on the sacrifice layer  51  as shown in FIG.  7 . 
     (2) A flying surface layer (SiO 2 )  41  is formed in all regions on the sacrifice layer  51  except for the position at which the head element  43  is formed and also except for the periphery of the head element  43 . Further, a second sacrifice layer (Al)  51   a  is formed in a region, in which the electrostatic microactuator  20  is formed, in the periphery of the head element  43  on the surface of the flying surface layer (SiO 2 ) as shown in FIG.  8 . 
     (3) Flying surface layers (SiO 2 )  41   a ,  41   b  are respectively formed in a region including the head element  43  in which the movable section  32  of the electrostatic microactuator  20  is formed and also in a region in which the stationary section  31  of the electrostatic microactuator  20  is formed, and these flying surface layers  41   a ,  41   b  are made thick so that the same thickness can be provided as shown in FIG.  9 . 
     (4) A conductor layer  53  made of Au is formed on the flying surface layer (SiO 2 )  41   b  on which the movable section  32  is formed, and one end of this conductor layer  53  is connected to the head element  43 , and the other end is exposed onto an upper surface of the flying surface layer (SiO 2 )  41   b  which is the movable section  32  as shown in FIG.  10 . 
     (5) Further, a third sacrifice layer (Al)  51   b  is formed on the second sacrifice layer (Al)  51   a  in a recessed portion between the flying surface layer (SiO 2 )  41   b , which forms the movable section  32 , and the flying surface layer (SiO 2 )  41   a , which forms the stationary section  31 . The thickness of this sacrifice layer  51   b  is increased so that the height of an upper surface of the sacrifice layer  51   b  can be the same as the height of the flying surface layers  41   a ,  41   b  as shown in FIG.  11 . 
     (6) A flexible conductor layer  22  shown in FIG. 6 is formed. As shown in FIGS. 12 and 13, a lower flexible insulating layer  25  made of polyimide or photoresist is formed into a bent pattern as shown in FIGS. 3 and 4. In this case, a connecting section of the movable conductor layer  22  with the conductor layer  53  of the head element  43  and a connecting section of the movable conductor layer  22  with the terminal  18  on the slider body side are opened by ion milling for the connection with a conductor  23 . Next, the conductor  23  is formed on the lower flexible insulating layer  25 . One end of the conductor  23  is electrically connected to the conductor layer  53  of the head element  43 , and the other end is electrically connected to the terminal  18  on the slider body side. Next, an upper flexible insulating layer  24  made of polyimide or photoresist is formed on the conductor  23 . In this way, a flexible conductor layer  22  is formed in which the conductor  23  is covered with the flexible insulating layers  24 ,  25  being sandwiched as shown in FIG.  12 . In this connection, FIG. 13 is an enlarged view showing a portion C in FIG.  12 . 
     (7) A plated base (Ni)  54  is formed on the overall upper surface as shown in FIG.  14 . 
     (8) Further, plating of Ni is conducted via the plated base (Ni)  54 , so that the thickness of the movable section  32  provided with the head element  43  (Ni-plating) and the thickness of the stationary section  31  in the periphery can be a predetermined value. Further, the thickness of the head slider body  42  in the periphery is further increased. In this connection, the teeth  31   a  of the stationary section  31  and the teeth  32   a  of the movable section  32  of the electrostatic microactuator  20  shown in FIG. 4 are also formed in this process of plating of Ni as shown in FIG.  15 . 
     (9) When the sacrifice layers  51 ,  51   a ,  51   b  are removed by etching in, for example, a solution of KOH, the magnetic head slider  10  is separated from the substrate  50 , and the magnetic head slider  10  (electrostatic microactuator  20 ) of the present invention is completed as shown in FIG.  16 . By the action of the flexible insulating layer  24 , the flexible lead wire  22  is supported in the air between the movable section  32  and the stationary section  31 . 
     Next, the operation of the magnetic head slider of the present invention will be explained below. When the movable section  32  of the electrostatic actuator  20  is loaded and unloaded by the magnetic head slider  10 , the head element  43  is made to come close to or contact a recording medium. On the other hand, when the electrostatic actuator  40   a  is driven into the tracking direction, the head element  43  can be positioned at a predetermined track position so as to record and reproduce information. 
     FIGS. 17 and 18 are views showing another embodiment of the formation process of the magnetic head slider  10  of the present invention, especially the formation process of the electrostatic microactuator  20 . In the formation process of the above embodiment, the third sacrifice layer (Al)  51   b  is formed and the thickness of the sacrifice layer  51   b  is made to be the same as the thickness of the flying surface layers  41   a ,  41   b  in the process shown in FIG.  11 . However, in this embodiment, instead of forming the third sacrifice layer (Al)  51   b , in the formation process of forming the flying surface layers  41   a ,  41   b  in FIG. 9, a step portion between the movable section  32  and the stationary section  31  is formed tapered so that the tapered shapes  41   a ′,  41   b ′ can be formed as shown in FIG.  17 . The flexible conductor layer  22  is formed along these tapered portions  41   a ′,  41   b ′ as shown in FIG.  18 . The flexible conductor layer  22  itself is formed by the same method as that of the above embodiment. In this case, the flexible lead wires  22  are formed along the tapered portions  41   a ′,  41   b ′ on the flying surface layer  41   a ,  41   b.    
     As explained above, according to the arrangement of the magnetic head slider of the present invention, the lead wires (flexible lead wires  22 ) such as signal wires drawn out from the head element provided in the movable section of the electrostatic microactuator can be formed in the wafer process in the formation of the magnetic head slider.