Patent Publication Number: US-7724478-B2

Title: Magnetic disk drive, wiring connection structure and terminal structure

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims priority from Japanese Patent Application No. JP2004-231948, filed Aug. 9, 2004, the full disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a magnetic disk drive, as well as a wiring connection structure and a terminal structure in the magnetic disk drive. Particularly, the present invention is concerned with a terminal structure and a wiring connection structure both able to attain a stable electric connection between terminals of a flexible printed circuit board and terminals of a wiring trace in a head suspension assembly, as well as a magnetic disk drive using those terminal structure and wiring connection structure. 
     With the recent tendency to the reduction in size of hard disk drives, the design and manufacture of various portions of a suspension for moving a magnetic head are becoming more and more difficult. In particular, the work for electrically connecting terminals of a flexible printed circuit board connected to an electronic part which is for controlling the operation of a magnetic disk drive and data transfer and terminals of a wiring trace in a head suspension assembly is now an important process which dominates product yield and reliability. Two types of methods are mainly adopted for the electric connection. According to the first method, the terminals of the flexible printed circuit board and the terminals of the wiring trace in the head suspension assembly are connected together somewhat apart through a solder bridge. According to the second method, both terminals are connected together in a contacted or sufficiently approached state by soldering or by ultrasonic bonding. 
     For mass production in accordance with the first method it is necessary to use an apparatus for melting and solidifying solder in a bridge shape. In case of adopting the second method, it is possible to effect mass production even by manual operation. 
       FIG. 7  is a plan view showing a multi-connector provided at one end of a wiring trace, in which (A) is a plan view of a soldering iron contacting side and (B) is a plan view of a side for contact with a flexible printed circuit board. A wiring trace  500  used in the second method comprises an insulating layer  502 , four conductor patterns  503   a ,  503   b ,  503   c , and  503   d , and a cover layer  504 . The four conductor patterns are arranged side by side on a surface of the insulating layer  502 . The cover layer  504  is formed on surfaces of the conductor patterns  503   a ,  503   b ,  503   c ,  503   d  and the surface of the insulating layer  502  so as to cover the conductor patterns  503   a ,  503   b ,  503   c , and  503   d . The wiring trace  500  is provided at one end thereof with a multi-connector  501 . The multi-connector  501  is provided with four terminals  505   a ,  505   b ,  505   c , and  505   d  at equal intervals in a longitudinal direction of the conductor patterns  503   a ,  503   b ,  503   c , and  503   d . The terminals  505   a ,  505   b ,  505   c , and  505   d  are portions of the conductor patterns  503   a ,  503   b ,  503   c , and  503   d , respectively, and are formed as somewhat wide patterns at front ends of the conductor patterns. In the insulating layer  502  of the multi-connector  501  is formed a single rectangular aperture  506  so that the four terminals  505   a ,  505   b ,  505   c , and  505   d  are partially exposed from the aperture. A cover layer  504   a  of the multi-connector  501  is formed separately from the cover layer  504  of the wiring trace  500 . In the cover layer  504   a , as is the case with the insulating layer  502  of the multi-connector  501 , a single rectangular aperture  507  is formed in the cover layer  504   a  so that the four terminals  505   a ,  505   b ,  505   c , and  505   d  are partially exposed from the aperture. 
       FIG. 8  is an explanatory diagram showing a connection structure in which the terminals  505   a ,  505   b ,  505   c , and  505   d  of the multi-connector  501  are soldered onto terminals  602   a ,  602   b ,  602   c , and  602   d  of a flexible printed circuit board  600 . The terminals  602   a ,  602   b ,  602   c , and  602   d  are provided on end sides of conductor patterns  601   a ,  601   b ,  601   c , and  601   d  serving as four lead wires. The multi-connector  501  is bent from the wiring trace  500  so that the aperture  506  of the insulating layer  502  (see  FIG. 7 ) faces up, and is placed on the flexible printed circuit board  600 . In  FIG. 8 , for convenience&#39; sake, the conductor patterns  601   a ,  601   b ,  601   c , and  601   d  of the flexible printed circuit board  600  are represented by solid lines except the portion covered with the multi-connector  501 . 
     The terminals  505   a ,  505   b ,  505   c , and  505   d  of the multi-connector  501  thus placed on the flexible printed circuit board  600  are aligned onto the terminals  602   a ,  602   b ,  602   c , and  602   d  of the same printed circuit board and are then heated with a soldering iron. As the terminals  505   a ,  505   b ,  505   c , and  505   d  are heated with the soldering iron, solder bumps formed on the terminals  602   a ,  602   b ,  602   c , and  602   d  melt, so that the terminals  505   a ,  505   b ,  505   c ,  505   d  and the terminals  602   a ,  602   b ,  602   c ,  602   d , which are exposed from the aperture  506  of the insulating layer  502 , are connected together by solder  508  so as to be covered substantially throughout the whole surface. All that is required for this soldering work is a mere fixing of the head suspension assembly to a jig. Thus, mass production can be effected even by manual operation, and therefore the device cost can be kept to a minimum. 
     BRIEF SUMMARY OF THE INVENTION 
     In the conventional wiring integrated type suspension referred to above in connection with the prior art, at the time of connecting the terminals  602   a ,  602   b ,  602   c ,  602   d  of the flexible printed circuit board  600  with the terminals  505   a ,  505   b ,  505   c ,  505   d  of the multi-connector  501  by soldering, the terminals  505   a ,  505   b ,  505   c , and  505   d  of the multi-connector  501  are in an uncovered state (flying leads) over the space within the aperture  506  formed in the insulating layer  502  and also over the space within the aperture  507  formed in the cover layer  504 . While soldering is performed from above the terminals of the multi-connector  501  with a soldering iron in such a state, if the terminals are subjected to aligning with the soldering iron or if they are displaced by mistake during the period after soldering the first terminal until soldering the next terminal, an edge portion of the aperture  506  in the insulating layer or of the aperture  507  in the cover layer may be cracked because the terminals of the multi-connector  501  are very thin (e.g., 0.012 mm), resulting in the entire suspension becoming defective. 
     Usually, solder bumps are formed on the terminals  602   a ,  602   b ,  602   c , and  602   d  of the flexible printed circuit board  600 , then the terminals  505   a ,  505   b ,  505   c , and  505   d  of the multi-connector  501  are aligned onto the solder bumps. The terminals  505   a ,  505   b ,  505   c , and  505   d  of the multi-connector  501  are heated with a soldering iron to melt the solder bumps and effect soldering thereby. In the connection structure shown in  FIG. 8 , however, with only the solder  508  formed by melting the solder bumps, there sometimes occurs a case where the strength is low. This is because the terminals of the multi-connector  501  are in an uncovered state (flying leads) over the space within the aperture  506  formed in the insulating layer  502  and also over the space within the aperture  507  formed in the cover layer  504   a . In this case, since soldering is performed so as to cover the whole of the terminals of the multi-connector  501  from above the terminals with solder, not only is it necessary to use solder other than the solder bumps, but also flux caused by contamination increases. 
     The present invention has been accomplished for solving the above-mentioned conventional problems. It is a feature of the present invention to provide a highly reliable terminal structure and wiring connection structure able to improve productivity. It is another feature of the present invention to prevent cracking of terminals of a wiring trace in a head suspension assembly at the time of connecting terminals of a flexible printed circuit board with the terminals of the wiring trace and also prevent the addition of solder. It is yet another feature of the present invention to provide a magnetic disk drive using those terminal structure and wiring connection structure. 
     In a first aspect of the present invention there is provided a terminal structure formed in a wiring trace including an insulating layer and a conductor pattern formed on a surface of the insulating layer. The conductor pattern comprises an exposed portion exposed from an aperture formed in part of the insulating layer and a lining portion adjacent to the exposed portion in a longitudinal direction of the conductor pattern and bonded to the insulating layer. 
     In a second aspect of the present invention there is provided a wiring connection structure connecting a flexible printed circuit board and a wiring trace with each other, the flexible printed circuit board including terminals, the wiring trace including an insulating layer and a conductor pattern formed on a surface of the insulating layer. The conductor pattern includes an exposed portion exposed from an aperture formed in part of the insulating layer and a lining portion bonded to the insulating layer in adjacency to the exposed portion in a longitudinal direction of the conductor pattern. The terminals of the flexible printed circuit board and the exposed portion of the conductor pattern are soldered to each other. 
     In a third aspect of the present invention there is provided a magnetic disk drive comprising a magnetic disk, a head for reading data from the magnetic disk, and an actuator head suspension assembly with the head attached thereto. Further the magnetic disk drive comprises a wiring trace including an insulating layer and a conductor pattern formed on a surface of the insulating layer and connected to the head. The conductor pattern includes an exposed portion exposed from an aperture formed in part of the insulating layer and a lining portion adjacent to the exposed portion in a longitudinal direction of the conductor pattern and bonded to the insulating layer. The magnetic disk drive still further comprises a flexible printed circuit board connected to the wiring trace. 
     The present invention is an improved invention of a terminal structure and a wiring connection structure in connection with terminals formed in a wiring trace and connected to terminals of a flexible printed circuit board. A terminal formed in a conductor pattern of the wiring trace is provided with an exposed portion exposed from an aperture formed in part of an insulating layer and a lining portion adjacent to the exposed portion in a longitudinal direction of the conductor pattern and bonded to the insulating layer. According to this construction it is possible to form a highly reliable terminal structure. For example, at the time of heating the terminal of the wiring trace with a soldering iron in the conventional terminal structure, the terminal may be cracked if it is aligned with a terminal of a flexible printed circuit board or if it is displaced after soldering. In the terminal structure of the present invention, since the lining portion of the terminal is bonded to the insulating layer, the exposed portion is strengthened and difficult to be cracked. Even if the exposed portion should be cracked, there is no fear that the crack may reach the lining portion. Thus, the conductivity of the terminal is ensured. If a through aperture extending through an area of the insulating layer adjacent to the exposed portion in the longitudinal direction of the conductor pattern is formed in the aperture formed in part of the insulating layer, solder comes to connect a heating surface and a contact surface of the exposed portion with each other through the through aperture. Once the solder thus connects the heating surface and the contact surface of the exposed portion with each other through the through area of the insulating layer, the solder connection by the lapping of solder becomes stronger. The “lining portion adjacent to the exposed portion and bonded to the insulating layer” as referred to herein means that the exposed portion and the lining portion are in contact with each other adjacently and continuously. 
     In connection with the first aspect there is provided a terminal structure wherein the conductor pattern includes a first conductor pattern provided with the exposed portion and the lining portion and a second conductor pattern also provided with the exposed portion and the lining portion, and the portions of the insulating layer corresponding to the lining portion of the first conductor pattern and the lining portion of the second conductor pattern are connected together on an end side of the wiring trace rather than the lining portions. 
     The aspect just described above is concerned with conductor patterns having plural terminals, and since the portions of the insulating layer corresponding to the lining portions of the first and second conductor patterns are connected together at a foremost end portion of the wiring trace rather than the lining portions, the strength of the insulating layer may be enhanced around the aperture. 
     According to the present invention it is possible to provide a magnetic disk drive able to connect terminals of a flexible printed circuit board and terminals of a wiring trace in a head suspension assembly with each other by soldering without giving rise to any soldering defect, as well as a wiring connection structure and a terminal structure both used in the magnetic disk drive. According to the present invention, moreover, it is possible to provide a magnetic disk drive able to improve productivity and superior in soldering function, as well as a wiring connection structure and a terminal structure both used therein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a magnetic disk drive according to an embodiment of the present invention, in which (A) is a plan view and (B) is a side view of an actuator head suspension assembly. 
         FIG. 2  is a perspective view for explaining the construction of an HGA according to the embodiment. 
         FIG. 3  is a plan view for explaining the structure of a gimbal assembly in a wiring trace according to the embodiment. 
         FIG. 4  is a plan view for explaining the structure of a multi-connector in the wiring trace according to the embodiment. 
         FIG. 5  is a plan view showing a wiring connection structure and a terminal structure of the multi-connector according to the embodiment. 
         FIG. 6  is a plan view for explaining a wiring connection structure and a terminal structure of a multi-connector according to another embodiment of the present invention. 
         FIG. 7  is a plan view showing a terminal structure of a conventional multi-connector. 
         FIG. 8  is a plan view showing a wiring connection structure and the terminal structure of the conventional multi-connector. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention will be described hereinunder with reference to the drawings. In all of the drawings, like numerals indicate like elements.  FIG. 1  illustrates a magnetic disk drive  1  according to an embodiment of the present invention, in which (A) is a plan view showing a schematic construction of the magnetic disk drive and (B) is a partially enlarged side view of an actuator head suspension assembly as seen in the direction of arrow A′ in (A). A base  2 , together with a base cover (not shown), forms a hermetically sealed space. An actuator head suspension assembly  3 , a magnetic disk  4 , a ramp  5 , and an external terminal  6  to be connected to a circuit board, are accommodated within the hermetically sealed space. The magnetic disk  4  is fixed to a spindle hub (not shown) so as to be rotated around a spindle shaft  7  by a spindle motor (not shown) disposed at a lower position. A magnetic layer is formed on at least one surface of the magnetic disk  4 . Two or more magnetic disks  4  may be stacked. A rotational direction of arrow A of the magnetic disk  4  is designated a forward rotation, while a rotational direction of arrow B of the disk is designated a reverse rotation, in relation to the actuator head suspension assembly  3 . The difference between the forward rotation and the reverse rotation appears mainly in the position of a head on a slider. However, the present invention is applicable to magnetic disk drives of both forward and reverse rotation types. 
     The actuator head suspension assembly  3  comprises an actuator assembly  31  and a head gimbal assembly (hereinafter referred to as “HGA”)  32  so as to be pivotable about a pivot shaft  8 . In this embodiment, two HGAs  32  are provided in a sandwiching relation to the magnetic disk  4  so that read and write of data may be done for both surfaces of the magnetic disk  4 . The actuator assembly  31  comprises actuator arms  33  for mounting the HGAs  32 , a coil support  34  for holding a voice coil (not shown), and a pivot housing which corresponds to a connection between the actuator arms  33  and the coil support  34 . To constitute a voice coil motor together with the voice coil, a voice coil yoke  35  is provided on the base  2 , and a voice coil magnet (not shown), which is a permanent magnet, is attached to a back side of the voice coil yoke  35 . 
     The HGAs  32  each comprise a load beam and a gimbal assembly which will be described in detail later. A merged lip  36  is formed at a front end of the load beam, and there is realized a so-called load/unload method wherein the merged lip  36  is allowed to slide on a retraction surface of the ramp  5  before stop of rotation of the magnetic disk  4  and the head/slider is retracted from above the surface of the magnetic disk  4 . However, the application of the present invention is not limited to the magnetic disk drive of the load/unload type, but the present invention is also applicable to a magnetic disk drive of a contact start/stop type. The merged lips  36 , HGAs  32  and actuator arms  33  are formed as a stack structure in a corresponding relation to the recording surfaces of the magnetic disk  4 . A relay terminal portion  37  is provided in the actuator assembly  31  to provide connection between a wiring trace  100  connected to the head and a flexible printed circuit board  10  connected to the external terminal  6 . The details of the wiring trace  100  and the flexible printed circuit board  10  will be described later. 
       FIG. 2  is an exploded perspective view illustrating the construction of each HGA  32 . Each HGA  32  comprises a mounting plate  321 , two pieces of load beams  322   a  and  322   b , a hinge  323 , and a gimbal assembly  100 A. The load beams need not always be two-piece load beams. A one-piece load beam will do. The gimbal assembly  100 A is provided at one end of the wiring trace  100  and adopts a wiring integrated type suspension structure as will be described later. The head/slider, indicated at  102 , is attached to a flexure tongue or gimbal tongue (see the reference numeral  103  in  FIG. 3 ) of the gimbal assembly  100 A on the side confronting a recording surface of the magnetic disk  4 . 
     In the gimbal assembly  100 A, the load beams  322   a  and  332   b  are fixed with a hinge  323  and the mounting plate  321  is fixed integrally by spot welding or by use of an adhesive. The mounting plate  321  is swaged to fix the HGA  32  to the actuator arm  33 . The load beams  322   a  and  322   b  pivot together with the actuator assembly  31  to carry the head/slider  102  up to a predetermined track and provide a pushing load for pushing the head/slider  102  against the opposed surface of the magnetic disk  4 . Under a balanced state between a positive pressure as a lifting force which an air bearing surface receives from an air flow and the pushing load induced by the load beam ( 322   a ,  322   b ) the head/slider  102  flies through a predetermined spacing from the surface of the rotating magnetic disk  4 . 
     In the wiring trace  100  of the actuator head suspension assembly  3  thus constructed, the gimbal assembly side as one end is connected (not shown) through a wiring pad to a slider pad formed on the head slider. The opposite end is connected through a multi-connector  100 B to the flexible printed circuit board  10 , as shown in  FIG. 1(B) . The wiring trace  100  having the gimbal assembly  100 A and the multi-connector  100 B is of a construction wherein a conductor layer which constitutes a conductor pattern and an insulating layer which insulates the conductor layer are stacked one on the other A cover layer as a dielectric for the prevention of corrosion is formed on the conductor layer to sandwich the conductor layer in between insulating layers. In the gimbal assembly  100 A, moreover, a metal layer as a structure for supporting the head/slider  102  is formed on an insulating layer. 
     As to the wiring trace  100  having such a stack structure, there are three types which are an additive type, a subtractive type, and a flexible board type, according to different manufacturing methods. 
     The additive type is a method in which various layers are stacked in order in accordance with the photolithography technique. The subtractive type is a method in which a sheet pre-formed with metal layer, insulating layer, conductor layer, and cover layer, is etched to form a predetermined structure. The flexible board type is a method in which a flexible printed circuit board formed in a predetermined shape by insulating layer, conductor layer, and cover layer, is affixed onto a metal layer. The wiring trace  100  used in this embodiment is the flexible board type, but the gimbal assembly  100 A is the additive type. 
       FIG. 3  illustrates a stack structure of the gimbal assembly  100 A which is a wiring integrated type suspension of the wiring trace  100 . As noted above, the gimbal assembly  100 A is formed by using a semiconductor processing technique such as a photolithographic etching process or a vapor deposition process.  FIG. 3(A)  shows the gimbal assembly  100 A completed by stacking plural layers, and the structures of the constituent layers of the gimbal assembly  100 A are shown in  FIGS. 3(B) to 3(E) .  FIG. 3(A)  shows the completed gimbal assembly  100 A as seen from the magnetic disk  4  side, in which the head/slider  102  is omitted for simplification of the drawing.  FIGS. 3(B) to 3(E)  are drawn in the order of stacking toward the magnetic disk surface. 
       FIG. 3(B)  shows a plane of a metal layer  111 A, in which as the material of the metal layer there is selected SUS 304 having a sheet thickness of 0.02 mm from among 300 Series stainless steels. The material of the metal layer  111 A is not limited to stainless steel, but there also may be selected another hard spring material such as beryllium, copper, or titanium. The metal layer  111 A includes a gimbal tongue  103 . 
       FIG. 3(C)  shows a plane of an insulating layer  113 A which is formed of a polyimide or epoxy resin for insulating the metal layer  111 A and conductor layer  115 A. The insulating layer  113 A is formed on the metal layer  111 A in a shape conforming to the pattern of the conductor layer  115 A. In this embodiment, the thickness of the insulating layer is set to 0.01 mm. Part of the insulating layer  113 A is formed also on the gimbal tongue  103 . 
       FIG. 3(D)  shows the conductor layer  115 A which is a wiring pattern for the head. In this embodiment, patterning is made by stacking pure copper to a thickness of 0.012 mm. The material of the conductor layer is not limited to copper, but may be another material such as aluminum or silver.  FIG. 3(E)  shows a pattern of a cover layer  117 A which is for protecting a surface of the conductor layer  115 A. The cover layer  117 A is formed by adhering a polyimide or epoxy layer of about 0.003 mm in thickness onto the conductor layer  115 A. 
       FIG. 4  shows a stack structure of the multi-connector  100 B of the wiring trace  100 . Like the gimbal assembly  100 A, the multi-connector  100 B is formed by a semiconductor processing technique such as a photolithographic etching process or a vapor deposition process. The multi-connector  100 B completed by stacking plural layers is shown in  FIG. 4(A)  and structures of constituent layers of the multi-connector  100 B are shown in  FIGS. 4(B) to 4(D) .  FIG. 4(A)  shows the completed multi-connector  100 B as seen from the flexible printed circuit board  10  side.  FIGS. 4(B) to 4(D)  are drawn in the order of stacking the constituent layers toward the flexible printed circuit board. 
       FIG. 4(B)  shows a plane of the insulating layer  113 B formed using a polyimide or epoxy resin for example. The insulating layer  113 B is formed in a shape conforming to the pattern of the conductor layer  115 B. The conductor layer  115 B is stacked on the insulating layer  113 B. In this embodiment, the thickness of the insulating layer is set at 0.01 mm. 
       FIG. 4(C)  shows the conductor layer  115 B which is a wiring pattern including terminals. In this embodiment, patterning is made by stacking pure copper to a thickness of 0.012 mm. The material of the conductor layer is not limited to copper, but may be another material such as aluminum or silver.  FIG. 4(D)  shows a pattern of a cover layer  117 B for protecting a surface of a conductor layer  115 B. The cover layer  117 B is formed by adhering a polyimide or epoxy layer of about 0.003 mm in thickness onto the conductor layer  115 B. The insulating layer  113 B, conductor layer  115 B and cover layer  117 B, as well as the insulating layer  113 A, conductor layer  115 A and cover layer  117 A of the gimbal assembly  100 A, conjointly constitute the wiring trace  100 . In both gimbal assembly  100 A and multi-connector  100 B, the thicknesses of the insulating layer  113 B, conductor layer  115 B and cover layer  117 B, as well as the metal layer  111 A, insulating layer  113 A, conductor layer  115 A, and cover layer  117 A, are illustrative and the scope of the present invention is not limited thereto. 
     In the terminal structure of the multi-connector  100 B having stacked insulating layer  113 B, conductor layer  115 B and cover layer  117 B, as shown in  FIG. 4 , the conductor layer  115 B is divided into two pairs, constituting a total of four conductor patterns  120   a ,  120   b ,  120   c , and  120   d  as four lead wires. At end portions of the conductor patterns  120   a ,  120   b ,  120   c , and  120   d  there are formed terminals  121   a ,  121   b ,  121   c , and  121   d , respectively, in a longitudinal direction of those conductor patterns. The terminals  121   a ,  121   b ,  121   c , and  121   d  are formed in a rectangular shape and are spaced at equal intervals so that their short sides are aligned with one another. 
     Four quadrangular apertures  122   a ,  122   b ,  122   c , and  122   d  are formed in the insulating layer  113 B of the multi-connector  100 B. The terminals  121   a ,  121   b ,  121   c , and  121   d  of the conductor patterns  120   a ,  120   b ,  120   c , and  120   d  in the conductor layer  115 B are respectively provided with exposed portions  131   a ,  131   b ,  131   c , and  131   d  exposed from the apertures  122   a ,  122   b ,  122   c , and  122   d  in the insulating layer  113 B and also provided with lining portions  132   a ,  132   b ,  132   c , and  132   d  adjacent to the exposed portions  131   a ,  131   b ,  131   c , and  131   d  and bonded to the insulating layer  113 B. 
     Since the lining portions  132   a ,  132   b ,  132   c , and  132   d  are areas bonded to the insulating layer  133 B and exhibiting an action of strengthening the terminals  121   a ,  121   b ,  121   c , and  121   d , the larger the area thereof, the better. As to the exposed portions  131   a ,  131   b ,  131   c , and  131   d , the larger the area thereof the easier the work, because they are areas to be heated with a soldering iron. On the other hand, it is necessary that the size of each of the terminals  121   a ,  121   b ,  121   c , and  121   d  comprising the lining portions  132   a ,  132   b ,  132   c ,  132   d  and the exposed portions  131   a ,  131   b ,  131   c ,  131   d  be set within a certain range, taking into account the necessity of ensuring a certain space between adjacent terminals and restrictions on the whole area of the multi-connector  100 B. If the area of the lining portions  132   a ,  132   b ,  132   c , and  132   d  relative to the total area of the area of the exposed portions  131   a ,  131   b ,  131   c ,  131   d  and the lining portions  132   a ,  132   b ,  132   c ,  132   d  is set in the range of 30% to 70%, preferably 40% to 60%, then the area which the exposed portions  131   a ,  131   b ,  131   c , and  131   d  require for appropriate soldering and the area which the lining portions  132   a ,  132   b ,  132   c , and  132   d  require for strengthening the terminal structure, may be set in a well-balanced manner. 
     The exposed portions  131   a ,  131   b ,  131   c , and  131   d  may be provided throughout the whole of the apertures  122   a ,  122   b ,  122   c , and  122   d . However, if the exposed portions  131   a ,  131   b ,  131   c , and  131   d  are provided so as to occupy only part of the areas of the apertures  122   a ,  122   b ,  122   c , and  122   d  and allow through apertures to remain in the apertures  122   a ,  122   b ,  122   c , and  122   d , it becomes easier to make a visual alignment at the time of connecting the terminals of the flexible printed circuit board  10  and the terminals  121   a ,  121   b ,  121   c ,  121   d , of the conductor patterns  120   a ,  120   b ,  120   c ,  120   d , and solder may be allowed to reach back surfaces from surfaces of the exposed portions  131   a ,  131   b ,  131   c , and  131   d , thereby making it possible to enhance the strength of those exposed portions. The areas of the exposed portions  131   a ,  131   b ,  131   c , and  131   d  corresponding to surfaces of the terminals  121   a ,  121   b ,  121   c , and  121   d  will hereinafter be referred to as “heating surfaces” and the areas of the exposed portions  131   a ,  131   b ,  131   c ,  131   d  and of the lining portions  132   a ,  132   b ,  132   c ,  132   d  corresponding to back surfaces of the terminals  121   a ,  121   b ,  121   c ,  121   d  will hereinafter be referred to as “contact surfaces.” 
     Further, a single rectangular aperture  123  is formed in a cover layer  117 B′ of the multi-connector  100 B in such a manner that the terminals  121   a ,  121   b ,  121   c , and  121   d  of the conductor patterns  120   a ,  120   b ,  120   c , and  120   d  are exposed except both of their longitudinal end portions. The cover layer  117 B′ of the multi-connector  100 B and the cover layer  117 B of the wiring trace  100  are separated in two from each other, centered on a bent portion  124 . The bent portion  124  is provided in the insulating layer  113 B. Three small apertures  125   a ,  125   b , and  125   c  are formed in the insulating layer  113 B along the long sides of the aperture  123  formed in the cover layer  117 B in order to make the multi-connector  100 B and the wiring trace  100  easier to be bent along a side face of the flexible printed circuit board  10  at the relay terminal portion  37 . By bending the flexible printed circuit board and the wiring trace along the apertures  125   a ,  125   b , and  125   c , it becomes easier to align and fix the terminals  121   a ,  121   b ,  121   c , and  121   d  of the multi-connector  100 B onto terminals  12   a ,  12   b ,  12   c , and  12   d  (see  FIG. 5 ) of the flexible printed circuit board  10  at the relay terminal portion  37 . The wiring trace  100  is not always required to have the cover layer  117 B. 
     Unlike the four apertures  122   a ,  122   b ,  122   c , and  122   d  formed in the insulating layer  113 B, the aperture  123  is formed as a single aperture. This is for close contact between the terminals  12   a ,  12   b ,  12   c ,  12   d  of the flexible printed circuit board  10  and the contact surfaces of the terminals  121   a ,  121   b ,  121   c ,  121   d  of the multi-connector  100 B. 
       FIG. 5  illustrates the wiring connection structure according to the present invention shown in  FIG. 1(B) , in which (A) is an enlarged plan view and (B) is a sectional view taken on line A-A in (A). In the flexible printed circuit board  10 , a conductor layer  11 , which is insulated sandwichingly by flexible sheets, is divided into pairs each for a single head. The conductor layer  11  is composed of conductor patterns  11   a ,  11   b ,  11   c , and  11   d  serving as four lead wires as a whole. On the flexible printed circuit board  10 , such conductor patterns are formed by the number corresponding to the number of heads. Terminals  12   a ,  12   b ,  12   c , and  12   d , which are exposed in a longitudinal direction of the conductor patterns  11   a ,  11   b ,  11   c , and  11   d , are formed at end portions of those conductor patterns on the side to be soldered to the contact surfaces of the terminals  121   a ,  121   b ,  121   c , and  121   d  of the multi-connector  100 B. The terminals  12   a ,  12   b ,  12   c , and  12   d  are formed in a rectangular shape and are spaced at equal intervals so that their short sides are aligned with one another. Solder bumps are formed on the terminals  12   a ,  12   b ,  12   c , and  12   d  of the flexible printed circuit board  10 . In  FIG. 5 , for convenience sake, the conductor patterns  11   a ,  11   b ,  11   c , and  11   d  of the flexible printed circuit board  10  are indicated by broken lines at their portions covered with the multi-connector  100 B and by solid lines at their uncovered portions. 
     The terminals  121   a ,  121   b ,  121   c , and  121   d  of the multi-connector  100 B thus constructed and the terminals  12   a ,  12   b ,  12   c , and  12   d  of the flexible printed circuit board  10  are soldered together at the relay terminal portion  37  of the actuator assembly  31 . This soldering step will be described below with reference to  FIGS. 4 and 5 . 
     First, the actuator head suspension assembly  3 , which is assembled in advance, is installed in a working jig (not shown) in such a manner that the relay terminal portion  37  faces up. The portion of the flexible printed circuit board  10  where the terminals  12   a ,  12   b ,  12   c , and  12   d  are formed is bonded to the relay terminal portion  37  with use of, for example, a thermosetting adhesive. For example, an epoxy resin is used as the thermosetting adhesive. The wiring trace  100  with the terminals on the gimbal assembly  100 A side soldered beforehand to the head/slider  102  of the HGA  32  is disposed along the actuator arm  33 . In this state, the wiring trace  100  is hooked to a hook portion (not shown) provided near the relay terminal portion  37  of the actuator arm  33 . Then, the wiring trace  100  and the multi-connector  100 B are bent along the bent portion  124 . More particularly, the cover layer  117 B side is bent in a valley shape so that the cover layer  117 B side of the multi-connector  100 B confronts the terminals  12   a ,  12   b ,  12   c , and  12   d  of the flexible printed circuit board  10 . 
     The terminals  121   a ,  121   b ,  121   c , and  121   d  of the multi-connector  100 B are aligned onto the terminals  12   a ,  12   b ,  12   c , and  12   d  of the flexible printed circuit board  10  with use of a tool such as tweezers, and the terminals  121   a ,  121   b ,  121   c , and  121   d  are soldered in this order. At this time, the cover layer  117 B is positioned between the terminals  12   a ,  12   b ,  12   c  and  12   d  and the terminals  121   a ,  121   b ,  121   c , and  121   d  to form a gap therebetween. However, since the cover layer  117 B is about 0.003 mm in thickness and not separated plural apertures, but a single large aperture  123  is formed, the contact surfaces of the terminals may come into close contact with the terminals of the flexible printed circuit board  10 . 
     This soldering step is carried out in the following manner. The heating surfaces of the terminal exposed portions  131   a ,  131   b ,  131   c , and  131   d  are heated with a soldering iron (not shown) to melt the solder bumps on the terminals of the flexible printed circuit board  10 . At this time, since the apertures formed in the insulating layer  113 B extend through the area of the insulating layer  133 B adjacent to the exposed portions  131   a ,  131   b ,  131   c , and  131   d  to constitute through apertures, solders  200   a ,  200   b ,  200   c , and  200   d  connect the heating surfaces and the contact surfaces of the exposed portions  131   a ,  131   b ,  131   c , and  131   d  with each other through the through apertures, as shown in  FIG. 5 . Once the solders  200   a ,  200   b ,  200   c , and  200   d  thus connect the heating surfaces and the contact surfaces of the exposed portions  131   a ,  131   b ,  131   c , and  131   d  with each other through the through area of the insulating layer  113 B, not only the soldered connections are made strong but also the strength of the terminals is enhanced by lapping of the solders  200   a ,  200   b ,  200   c , and  200   d.    
     While the heating surfaces of the exposed portions  131   a ,  131   b ,  131   c , and  131   d  of the terminals are heated with a soldering iron to melt the solder bumps on the terminals of the flexible printed circuit board  10 , if the terminals are aligned or displaced by mistake with the soldering iron, the terminals of the multi-connector  100 B may be cracked because they are very thin (e.g., 0.012 mm). However, the terminals of the multi-connector  100 B are partially bonded as lining portions  132   a ,  132   b ,  132   c , and  132   d  to the insulating layer  113 B and it is only the exposed portions  131   a ,  131   b ,  131   c , and  131   d  that are uncovered (flying leads) over the spaces of the apertures formed in the insulating layer  113 B. Therefore, at edges of the apertures, the exposed portions are difficult to be cracked and thus it is possible to strengthen the terminals. Even if the exposed portions are cracked, the cracks do not reach the lining portions  132   a ,  132   b ,  132   c , and  132   d  and hence conductivity is ensured. If such a terminal structure is adopted, it becomes no longer necessary to use a preliminary solder so far provided on heating surfaces for lapping of solder between the heating surfaces and contract surfaces in order to strengthen the terminal structure. 
     Further, in the multi-connector  100 B of the wiring trace  100 , the insulating layer  113 B connects at the foremost end of the multi-connector  100 B rather than the lining portions  132   a ,  132   b ,  132   c , and  132   d . In the multi-connector  100 B, therefore, the strength of the insulating layer  113 B may be enhanced around the apertures  122   a ,  122   b ,  122   c , and  122   d , and it is possible to strengthen the terminals  121   a ,  121   b ,  121   c , and  121   d.    
     In the multi-connector  100 B constructed as above, for example, the terminals  121   a ,  121   b ,  121   c , and  121   d  of the conductor patterns  120   a ,  120   b ,  120   c , and  120   d  are 0.35 mm in width and 1.4 mm in length. The apertures  122   a ,  122   b ,  122   c , and  122   d  formed in the insulating layer  113 B of the multi-connector  100 B are 0.5 mm wide and 0.7 mm long. Under these dimensional conditions of various portions, the width of each of the apertures  122   a ,  122   b ,  122   c , and  122   d  formed through the area of the insulating layer  113 B adjacent to the exposed portions  131   a ,  131   b ,  131   c , and  131   d  is set at 0.3 mm. 
     According to the above embodiment, in the terminals  121   a ,  121   b ,  121   c , and  121   d  of the conductor patterns  120   a ,  120   b ,  120   c , and  120   d  in the multi-connector  100 B, the lining portions  132   a ,  132   b ,  132   c , and  132   d  are provided on one sides of the exposed portions  131   a ,  131   b ,  131   c , and  131   d . But this constitutes no limitation and those lining portions may be provided on both sides of the exposed portions  131   a ,  131   b ,  131   c , and  131   d.    
       FIG. 6  shows another embodiment of the present invention in connection with the exposed portions  131   a ,  131   b ,  131   c ,  131   d  and the lining portions  132   a ,  132   b ,  132   c ,  132   d  in the multi-connector  100 B. As shown in  FIG. 6(A) , also in the case where the lining portions  132   a ,  132   b ,  132   c , and  132   d  are provided on both sides of the exposed portions  131   a ,  131   b ,  131   c , and  131   d , since both sides of the exposed portions  131   a ,  131   b ,  131   c , and  131   d  are bonded as lining portions  132   a ,  132   b ,  132   c , and  132   d  to the insulating layer  113 B, the terminals of the multi-connector are difficult to be cracked and it is possible to strengthen the terminals. Even if the exposed portions are cracked, the cracks do not reach the lining portions  132   a ,  132   b ,  132   c , and  132   d  which are bonded to the insulating layer  113 B, so that conductivity is ensured. Such through apertures  133   a ,  133   b ,  133   c , and  133   d  as shown in  FIG. 6(B)  may be formed in the exposed portions  131   a ,  131   b ,  131   c , and  131   d  with lining portions  132   a ,  132   b ,  132   c , and  132   d  formed on both sides thereof. By forming the through apertures  133   a ,  133   b ,  133   c , and  133   d  in the exposed portions  131   a ,  131   b ,  131   c , and  131   d , it becomes easier to make a visual alignment of terminals. In addition, the solder used in soldering may connect the heating surfaces and the contact surfaces of the exposed portions  131   a ,  131   b ,  131   c , and  131   d  with each other and thus the solder connection becomes stronger. The through apertures  133   a ,  133   b ,  133   c , and  133   d  may take any of various shapes including circular and quadrangular shapes insofar as the solder may connect the heating surfaces and the contact surfaces of the exposed portions  131   a ,  131   b ,  131   c , and  131   d  with each other through the through apertures  133   a ,  133   b ,  133   c , and  133   d.    
     Although in the above embodiment the heating surfaces of the exposed portions  131   a ,  131   b ,  131   c , and  131   d  of the exposed portions are heated with a soldering iron to melt the solder bumps on the terminals of the flexible printed circuit board  10 , thereby soldering the multi-connector  100 B and the flexible printed circuit  10  with each other, this constitutes no limitation and thread-like solder or the like may be used. In this case, thread-like solder is melted and placed onto the exposed portions  131   a ,  131   b ,  131   c , and  131   d . If the area of the insulating layer  133 B adjacent to the exposed portions  131   a ,  131   b ,  131   c , and  131   d  is a through area, the solder used in soldering may connect the heating surfaces and the contact surfaces of the exposed portions  131   a ,  131   b ,  131   c , and  131   d  with each other. Even if such through apertures  133   a ,  133   b ,  133   c , and  133   d  as shown in  FIG. 6(B)  are formed in the exposed portions  131   a ,  131   b ,  131   c , and  131   d , the solder used in soldering may connect the heating surfaces and the contact surfaces of the exposed portions  131   a ,  131   b ,  131   c , and  131   d  with each other. 
     Although in the above embodiment the terminals of conductor patterns and the apertures of the insulating layer  133 B and of the cover layer  117 B in the multi-connector  100 B are all formed rectangularly, no limitation is made thereto and they may be in any other shape insofar as the exposed portions are exposed from the apertures of the insulating layer  113 B, the lining portions are bonded to the insulating layer  113 B and the terminals of the multi-connector  100 B and the terminals of the flexible printed circuit board  10  may be soldered to each other. 
     Although in the above embodiment the multi-connector  100 B is provided at an end of the wiring trace  100 , no limitation is made thereto, and the multi-connector  100 B may be provided at a certain intermediate position of the wiring trace  100 . 
     Although in the above embodiment the terminals of the multi-connector  100 B and the terminals of the flexible printed circuit board  10  are soldered to each other, no limitation is made thereto and both may be connected by ultrasonic bonding. In ultrasonic bonding there is used a bonding tool which comes into contact with an object to be bonded and which imparts an ultrasonic oscillation to the object. More specifically, the tip of a bonding tool used in place of the soldering iron is put in contact with a terminal of the multi-connector  100 B which is superimposed on a terminal of the flexible printed circuit board  10 , under a predetermined pressure, and produces an ultrasonic oscillation between both terminals. With a friction induced between both terminals by the oscillation, an oxide layer on the contacted surface is removed, a local temperature rise is added, and a bonding force is created between atoms of the bonded metals. Thus the terminal of the multi-connector  100 B and that of the flexible printed circuit board  10  are bonded together. The terminal structure described in this embodiment is difficult to be cracked even under oscillation and the force applied by the bonding tool and is thus also suitable for ultrasonic bonding. 
     It is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims alone with their full scope of equivalents.