JPH1116139A - Assembly method of carriage assembly and head unit used in the assembly - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of the damage to a magnetic head caused by static electricity. SOLUTION: Plural head lead wires 46 extended from a magnetic head are connected to first repeater pads 74 of a flexible printed circuit substrate (FPC) 70. Second repeater pads 76 of the FPC 70 are mutally short circuited by a bar shaped soldering member 90. Then, the short circuited pads 76 are positioned and mounted on the connection pads of the flexible printed circuit substrate, the member 90 is melted and the pads 76 are soldered to the connection pads and the short circuits of the pads 76 are removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method of assembling a carriage assembly having a magnetic head, and a head unit used in the method.

[0002]

2. Description of the Related Art In recent years, magnetic disks have been widely used as memories for storing large amounts of information in computers such as personal computers, laptop computers, and book computers.

A magnetic disk device of this type generally includes a plurality of magnetic disks arranged in a stacked state, a magnetic head assembly having a plurality of magnetic heads for recording and reproducing information on and from the magnetic disks, A carriage assembly that movably supports these magnetic head assemblies with respect to the magnetic disk; and a voice coil motor that rotates the carriage assembly to move the magnetic head to a desired track position on the magnetic disk. I have.

A plurality of magnetic disks are fixed to a hub of a spindle motor, and are supported coaxially with one another at predetermined intervals in a stacked state. Then, by driving the spindle motor, the magnetic disk is rotated at a predetermined speed.

A magnetic head assembly having a magnetic head includes:
Two magnetic disks are provided for one magnetic disk, and are respectively located opposite to the upper and lower surfaces of the magnetic disk.
For example, in a magnetic disk drive having two magnetic disks, four magnetic head assemblies are provided.

Each magnetic head assembly has a slider on which a magnetic head is formed, and a suspension for applying a predetermined load to the magnetic head. The carriage includes a bearing assembly and a plurality of arms extending from the bearing assembly, and the magnetic head assemblies are fixed to the corresponding arms.

Further, the magnetic disk drive has a circuit board for processing signals to the magnetic head, and this circuit board is electrically connected to a plurality of magnetic heads by the following configuration.

That is, the flexible printed circuit board extends from the circuit board, and the front end thereof is fixed to the bearing assembly of the carriage. Also, a number of connection pads are formed at the tip of the flexible printed circuit board.

On the other hand, for example, four lead wires extend from each magnetic head. These leads extend along the suspension and the arm to the vicinity of the bearing assembly, and their extending ends are soldered one by one to connection pads of the flexible printed circuit board, or a pre-connected relay flexible printed circuit. It is connected to the connection pad via the substrate.

[0010]

Conventionally, a protection circuit has been provided to prevent a magnetic head from being damaged by static electricity or the like during an assembling operation of a magnetic disk drive. This protection circuit is provided on the side of the flexible printed circuit board fixed to the carriage assembly. On the other hand, due to dimensional restrictions and functional restrictions, the magnetic head before connection to the flexible printed circuit board side is not provided with a protection circuit. Therefore, there is a problem that the magnetic head before being connected to the flexible printed circuit board is susceptible to static electricity or the like and is easily damaged before assembling the carriage assembly.

The present invention has been made in view of the above points, and has as its object to provide a method of assembling a carriage assembly capable of preventing damage to a magnetic head due to static electricity or the like, and a magnetic head unit used in the assembling method. Is to provide.

[0012]

In order to achieve the above object, a method of assembling a carriage assembly according to the present invention is characterized in that the extending ends of a plurality of head lead wires derived from a magnetic head are electrically connected to each other by a conductive material and short-circuited. Then, the extended end of the short-circuited head lead wire is positioned and mounted on the connection pad of the flexible printed circuit board fixed to the carriage body, and the extended end of the positioned lead wire is connected to the connection pad. It is characterized by soldering.

Another method of assembling according to the present invention provides a relay flexible printed circuit board including a plurality of first relay pads and a plurality of second relay pads respectively connected to the first relay pads. The extending ends of the plurality of head lead wires derived from the magnetic head are connected to the first relay pads of the relay flexible printed circuit board, and the second relay pads of the relay flexible printed circuit board are electrically connected to each other by a conductive material. Short-circuiting, positioning and mounting the short-circuited second relay pad on the connection pad of the flexible printed circuit board fixed to the carriage body, and soldering the positioned second relay pad to the connection pad; It is characterized by.

According to the method of assembling the carriage assembly constructed as described above, a protection circuit is formed by short-circuiting the head lead wires of the magnetic head with a conductive member in advance, so that static electricity or the like does not flow to the magnetic head. To
Thereafter, the head lead wires are soldered to connection pads provided on the flexible printed circuit board on the carriage body side.

Further, according to the present invention, a solder material is used as the conductive member. When a solder material is used, at the time of connection, it is melted by heat to electrically connect the head lead wire or the second relay pad to the connection pad, and by melting, the short circuit between the head lead wires is automatically released. I do.

Further, the head unit according to the present invention includes:
A head unit used for assembling a carriage assembly, comprising a magnetic head, a plurality of head lead wires derived from the magnetic head, and a conductive member that is connected to the extending ends of the head lead wires and short-circuited to each other. It is characterized by.

Another head unit according to the present invention includes a relay flexible printed circuit board connected to an extended end of a head lead wire, and second relay pads of the relay flexible printed circuit board are connected to each other by a conductive member. Have been short circuited.

According to the head unit having the above-described structure, a protection circuit is formed by short-circuiting the head lead wires with the conductive member, thereby preventing static electricity and the like from flowing to the magnetic head.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for assembling a carriage assembly according to the present invention will be described below in detail with reference to the drawings. First, a configuration of a hard disk drive (hereinafter referred to as an HDD) including a carriage assembly to which the assembly method of the present invention is applied will be described.

As shown in FIG. 1, the HDD has a rectangular box-shaped case 10 having an open upper surface, and a top cover (not shown) which is screwed to the case with a plurality of screws to close an upper end opening of the case. doing.

In the case 10, three magnetic disks 12a, 12b and 12c as magnetic recording media, a spindle motor 13 for supporting and rotating these magnetic disks, and recording and reproducing of information with respect to the magnetic disks. A plurality of magnetic heads, a carriage assembly 14 that movably supports these magnetic heads with respect to the magnetic disks 12a, 12b, 12c, and a voice coil motor (hereinafter VC) for rotating and positioning the carriage assembly
M) 16 and a substrate unit 17 having a preamplifier and the like.

A printed circuit board (not shown) for controlling operations of the spindle motor 13, the voice coil motor 16, and the magnetic head is screwed to the outer surface of the case 10 via a board unit 17, and is connected to the bottom wall of the case. It is located opposite.

Each magnetic disk 12a, 12b, 12c
Has a diameter of 65 mm (2.5 inches) and has magnetic recording layers on the upper and lower surfaces. Three magnetic disks 12
a, 12b, and 12c are coaxially fitted to a hub (not shown) of the spindle motor 13, and are stacked at predetermined intervals along the axial direction of the hub. Then, the magnetic disks 12a, 12b, 12c are driven to rotate at a predetermined speed by the spindle motor 13.

As shown in FIGS. 1-3, the carriage assembly 14 includes a bearing assembly 18 fixed on the bottom wall of the case 10. The bearing assembly 18 includes a pivot 20 erected on the bottom wall of the case 10 and a cylindrical hub 22 rotatably supported on the pivot via a pair of bearings.
And An annular flange 23 is formed on the upper end of the hub 22, and a screw portion 24 is formed on the outer periphery of the lower end.

The carriage assembly 14 includes six arms 26a, 26b,
26c, 26d, 26e, 26f, two spacer rings 27a, 27b, and six magnetic head assemblies 28 supported by each arm.

Each of the arms 26a to 26f is formed of, for example, a stainless steel material such as SUS304 into a thin flat plate having a thickness of 0.3 mm or less, and has a circular through hole 31 at one end, that is, at the base end. Are formed.

Each magnetic head assembly 28 has an elongated suspension 30 formed by a leaf spring, and a magnetic head 32 fixed to the suspension. The base of the suspension 30 is fixed to the distal ends of the arms 26a to 26f by spot welding or bonding, and extends from the arm.

Each magnetic head 32 has a substantially rectangular slider (not shown) and a recording / reproducing MR (magnetoresistive) head formed on the slider.
Is fixed to a gimbal part formed at the tip of the head. Note that the suspension 30 may be formed integrally with the arm using the same material as the arm.

For example, four head lead wires 46 extend from each magnetic head 32 and extend along the side edges of the arm to the base end of the arm. Then, the magnetic head assembly 28
The fixed arms 26a to 26f are fitted on the outer periphery of the hub in a state of being stacked on the flange 23 by inserting the hub 22 into the through hole 31. The spacer ring 27a is fitted to the outer periphery of the hub 22 with the spacer ring 27b sandwiched between the arms 26e and 26f, and the spacer ring 27b is fitted between the arms 26e and 26f. Further, a support ring 34 is fitted to the hub 22 and is sandwiched between the arms 26c and 26d.

The bearing assembly 18, the spacer rings 27a and 27b, and the support ring 34 constitute a main body of the carriage assembly 14. Hub 22
Six arms 26a to 26f fitted to the outer periphery of
The two spacer rings 27 a and 27 b and the support ring 34 are connected to the nut 3 screwed into the thread portion 24 of the hub 22.
6 and the flange 23, and is fixed and held on the outer periphery of the hub 22. Thereby, six arms 26
a to 26d are spaced apart and parallel to each other and extend in the same direction from the hub 22.

The magnetic heads 32 of the magnetic head assembly 28 attached to the arms 26a, 26b are located opposite each other, and the magnetic heads 32 of the magnetic head assembly 28 attached to the arms 26c, 26d are located opposite each other. Further, the magnetic heads 32 of the magnetic head assembly 28 attached to the arms 26e and 26f are located facing each other. The arms 26a to 26f and the magnetic head assembly 28 fixed to these arms are rotatable integrally with the hub 22.

The support ring 34 has two support frames 3 extending in opposite directions to the arms 26a to 26f.
8 and a coil 44 constituting a part of the VCM 16 is fixed on these support frames.

As can be clearly understood from FIG. 1, when the carriage assembly 14 constructed as described above is incorporated in the case 10, the magnetic disk 12a is located between the arms 26a and 26b, and the magnetic disk 12b is connected to the arms 26c and 26c. The magnetic disk 12c is located between the arms 26e and 26f. Then, the magnetic head assembly 28 attached to the arms 26a, 26b
The magnetic head 32 contacts the upper and lower surfaces of the magnetic disk 12a, respectively, and holds the magnetic disk 12a from both sides.

Similarly, the magnetic heads 32 attached to the arms 26c and 26d contact the upper and lower surfaces of the magnetic disk 12b, respectively, and hold the magnetic disk 12b from both sides. Further, the magnetic heads 32 attached to the arms 26e and 26f contact the upper and lower surfaces of the magnetic disk 12c, respectively, and
Is sandwiched from both sides. A predetermined head load is applied to each magnetic head 32 by the spring force of the suspension 30, and is pressed against the surface of the magnetic disk when the magnetic disk is stopped.

On the other hand, as shown in FIG. 1, in a state where the carriage assembly 14 is incorporated in the case 10,
The coil 44 fixed to the support frame 38 is the case 1
The VCM 16 is located between a pair of yokes 48 fixed on the upper side of the motor and together with these yokes and a magnet (not shown) fixed to one of the yokes. Therefore, the coil 44
, The carriage assembly 14 rotates, and the magnetic head 32 moves the magnetic disks 12a and 12a.
b and 12c are moved and positioned on the desired track.

As shown in FIGS. 1 and 4, the board unit 17 has a rectangular board body 52 fixed on the bottom wall of the case 10, and a plurality of electronic components 53 are provided on the board body. And a connector 54 and the like are mounted. Also,
The board unit 17 is a belt-shaped main flexible printed circuit board (hereinafter referred to as a main FPC) 5 in which the board body 52 and the carriage assembly 14 are electrically connected.
6. The main FPC 56 extends from the board main body 52, and a reinforcing plate 50 is attached to the back surface of the connection portion 56a. The main FPC 56 is formed integrally with the substrate main body 52 by a flexible printed wiring board.

As shown in FIGS. 4 and 5, the main FP
C56 has a large number of conducting wires 58 extending parallel to each other along the axial direction of the FPC. Further, six sets 60 a to 60 f of connection pads 60 corresponding to the number of the magnetic heads 32 are formed in the connection portion 56 a located at the extension end of the FPC 56, and each of the connection pads 60 a is electrically connected to the substrate main body 52 through the conductor 58. ing. The connection pads 60 of each set are provided four by four in accordance with the number of the head lead wires 46 of the magnetic head 32, and are arranged in a predetermined arrangement, for example, at a predetermined interval, for example, in the main F.
They are provided in a straight line in the axial direction of the PC 56. The plurality of sets 60 a to 60 f are provided in parallel with each other and at predetermined intervals in a direction orthogonal to the axial direction of the main FPC 56.

Each connection pad 60 is formed, for example, in a circular shape, and the surface thereof is precoated with a preliminary solder 61 in a convex shape. The connecting portion 56a has a through hole 62 and a notch 64 for screwing the connecting portion to the bearing assembly 18 of the carriage assembly 14.
Further, the distal end of the connection portion 56a is bent at a right angle to form a guide portion 56b for guiding the head lead wire.

The connecting portion 56a of the main FPC 56 has screw holes 65a formed in the spacer rings 27a and 27b.
65b (see FIG. 3), the through hole 62 and the notch 6 respectively.
It is secured to the bearing assembly 18 of the carriage assembly 14 by screwing a screw 66 through 4.

On the other hand, the four head lead wires 46 derived from each magnetic head 32 are electrically connected to a corresponding connection pad set of the main FPC 56 via a relay flexible printed circuit board (hereinafter referred to as a relay FPC) 70. Have been. As shown in FIGS. 7 and 8, each relay FPC 7
Reference numeral 0 denotes a base plate 72 made of an insulating material formed in an elongated rectangular shape, and a conductor pattern 73 formed on the surface of the base plate.
And The length of the base plate 72 is the main FPC
The connecting portion 56a is formed smaller than the length of the connecting portion 56a.

The conductor pattern 73 has four first relay pads 74, four second relay pads 76, and four conductive wires 78 electrically connecting the first and second relay pads. The portion of the conductor 78 in the conductor pattern 72 is covered with the insulating layer 80.

The first relay pads 74 are formed on one end of the base plate 72 in the longitudinal direction in parallel along the longitudinal direction. The second relay pad 76 is connected to the base plate 72.
Are formed at predetermined intervals along one long side of the base plate, and extend in parallel with each other along the width direction of the base plate. In particular, the four second relay pads 76
Are provided in the same arrangement state as the corresponding set of four connection pads 60 on the main FPC 56 side.

Each of the second relay pads 76 of the base plate 72
The opening 82 is formed in the part located on both sides of. Each second relay pad 76 is formed on a bridge portion 83 extending between the openings 82.

The leading ends of the four head lead wires 46 derived from each magnetic head 32 are soldered to first relay pads 74 of the relay FPC 70, respectively. In order to increase the mechanical strength of the connection part, the soldering part is covered with a coating material (not shown). Note that a conductive adhesive may be used to connect the head lead wire 46 to the first relay pad 74.

Each relay FPC 70 to which the four head lead wires 46 are connected, connects the second relay pad 76 to the main FP
It is fixed to the connection portion 56a of the main FPC by soldering to a corresponding set of connection pads 60 on the C56 side. Thus, each magnetic head 32 is electrically connected to the board unit 17 via the head lead wire 46, the relay FPC 70, and the main FPC 56.

When assembling the carriage assembly 14 configured as described above, first, as shown in FIG. 9, a relay FPC 70 having the above-described configuration is prepared.
Further, an elongated rod-shaped solder material 90 is placed on the four second relay pads 76. Then, the solder material 90 is pressed against the second relay pad 76 by pressing the solder material 90 against the second relay pad 76 in a heated state.
As a result, the four second relay pads 76 are electrically connected to each other via the solder material 90 as a conductive material and short-circuited.

Subsequently, the four head lead wires 46 derived from the magnetic head 32 are connected to the first relay pads 74 of the relay FPC 70. Thereby, the magnetic head 32,
A head unit 92 having the head lead wire 46 and the relay FPC 70 is formed. In the head unit 92,
The four head lead wires 46 are in conduction with each other via the relay FPC 70 and are short-circuited, and constitute a protection circuit. Then, six sets of such head units 92 are prepared.

Next, after the head assemblies 28 are formed using the respective head units 92, these head assemblies are attached to the arms 26a to 26f. Subsequently, after the fixed arms 26a to 26f of the magnetic head assembly 28, the spacer rings 27a and 27b, and the like are fixed to the bearing assembly 18, the connecting portion 56 of the main FPC 56 is attached to the bearing assembly 18.
a is screwed with a pair of screws 66.

Thereafter, as shown in FIG. 10, the relay FPC 70 of each head unit 92 is positioned and arranged on the corresponding set of connection pads 60 on the main FPC 56 side, and the solder material 90 is formed using a pulse heater or a soldering iron. Heat. In this case, each relay FPC 70 is located on a set of four connection pads 60 corresponding to four bridge portions 83. Thereby, the solder material 90 is melted and the short circuit of the second relay pad 76 is released, and at the same time, the four second relay pads 76 are soldered to the corresponding connection pads 60 by the melted solder. At the time of soldering, the molten solder material 90 flows favorably onto the connection pad 60 through the opening 82 of the relay FPC 70.

Therefore, the magnetic head 32 is electrically connected to the board unit 17 via the head lead wire 46, the relay FPC 70, and the main FPC 56. By similarly connecting the relay FPCs 70 of the six head units 92 to the main FPC 56 in a similar manner, the assembly of the carriage assembly 14 is completed.

According to the method of assembling the carriage assembly configured as described above, in the state before the magnetic head 32 is connected to the main FPC on the carriage body side,
The second relay pad 7 of the relay FPC 70 by the solder material 90
6 is short-circuited to form a protection circuit for the magnetic head. Therefore, it is possible to prevent static electricity and the like from flowing to the magnetic head 32 during the assembling work, and to prevent damage to the magnetic head due to the static electricity and the like.

Further, as a short-circuiting conductive material, a solder material 9 is used.
Since the relay FPC is used to connect the relay FPC to the connection pad of the main FPC, the solder material 90 is melted by heat and can be used for electrical connection between the relay FPC and the main FPC. As a result, the short circuit of the magnetic head 32 is released, and the protection circuit on the magnetic head side which becomes unnecessary after the carriage assembly is assembled can be automatically deleted. Therefore, it is possible to shorten the connection work time and improve the workability. When the solder material 90 is used as the conductive material, the spare solder 61 provided on the connection pad 60 side of the main FPC can be omitted.

Further, the second relay pad 7 of the relay FPC 70
6 are provided in the same arrangement state as the corresponding set of connection pads 60, so that the four second relay pads 76 can be simultaneously and easily aligned with the four connection pads 60, and the four 2 Connect the relay pad 76 to the connection pad 60
Can be soldered simultaneously.

In the above embodiment, the relay FP
Connect the head lead wire 46 to the main FPC 5 via C70.
6 has been described, but the relay FPC
Alternatively, the extension end of the head lead wire 46 may be directly soldered to the connection pad on the main FPC side without using the above.

That is, according to the second embodiment shown in FIGS. 11 and 13, the head unit 92 is an elongated rod-shaped solder material that is short-circuited by conducting between the extending ends of the four head lead wires 46. 90. Head lead wire 4
The extended end portions 6 are held at predetermined intervals by the solder material 90, that is, at the same arrangement intervals as the connection pads 60 of each set of the main FPC 56.

When the solder material 90 is attached to the extension end of the head lead wire 46 as described above, the extension of the head lead wire is positioned by using a jig 94 as shown in FIG. The jig 94 includes four positioning grooves 96 provided in parallel at predetermined intervals, and a solder material mounting groove 97 extending through these positioning grooves. First, the extending ends of the four head lead wires 46 are mounted in the positioning grooves 96 of the jig 94 and are held at predetermined intervals. Subsequently, the solder material 90 is mounted on the mounting groove 97 from above, and is mounted on the head lead wire 46. In this state, the solder material 90 is pressed against the head lead wire 46 at a predetermined pressure while being heated, and is fixed to the head lead wire.
The head unit 92 is completed.

In the head unit 92, the four head lead wires 46 are short-circuited by the solder material 90 to form a protection circuit. At the same time, the extending end of the head lead wire 46 is held in the same arrangement state as the connection pads 60 on the main FPC 56 side.

As shown in FIG. 13, when the head lead wire 46 of the head unit 92 is connected to the connection pad 60 of the main FPC 56 when assembling the carriage assembly, the length of the head lead wire 46 connected by the solder material 90 is extended. The protruding ends are positioned and arranged on the corresponding pairs of connection pads 60, and the solder material 90 is heated using a pulse heater or a soldering iron. Thereby, the solder material 90 is melted and the short circuit of the head lead wire 46 is released, and at the same time, the four head lead wires are soldered to the corresponding connection pads 60 by the melted solder. Therefore, the magnetic head 32 is connected to the head lead wire 46 and the relay FPC.
70, and is electrically connected to the board unit 17 via the main FPC 56.

The other structure is the same as that of the above-described embodiment, and the same parts are denoted by the same reference numerals and detailed description thereof will be omitted. According to the method of assembling the carriage assembly and the head unit 92 configured as described above, the head lead wire 46 is short-circuited by the solder material 90 to form a protection circuit for the magnetic head, as in the above-described embodiment. This can prevent damage to the magnetic head due to static electricity or the like during the assembly operation. Also,
By using the solder material 90, the soldering of the head lead wire and the connection pad and the release of the short circuit of the head lead wire can be simultaneously performed, so that the connection work time can be reduced and the workability can be improved.

Further, the extending end portion of the head lead wire can be held in the same arrangement state as the corresponding set of connection pads 60 by the solder material 90, so that the positioning and soldering of the head lead wire with respect to the connection pads can be performed. This can be easily performed.

The present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the present invention. For example, in the above-described embodiment, a method of assembling a carriage assembly having six magnetic heads has been described. However, it goes without saying that the assembly method of the present invention can be applied to a carriage assembly having different numbers of magnetic heads. No. Further, the number of head lead wires, the arrangement structure of the connection pads on the main FPC side and the arrangement of the second relay pads on the relay FPC side can be changed as necessary.

[0062]

As described in detail above, according to the present invention, after the head leads are short-circuited to form a protection circuit for the magnetic head, the head leads are connected to the main flexible printed circuit board. Therefore, it is possible to provide a method of assembling a carriage assembly capable of preventing the magnetic head from being damaged by static electricity or the like, and a magnetic head unit used in the assembling method.

[Brief description of the drawings]

FIG. 1 is an exemplary perspective view showing the inside of an HDD provided with a carriage assembly to which an assembling method according to an embodiment of the present invention is applied;

FIG. 2 is an exploded perspective view of a carriage assembly provided in the HDD.

FIG. 3 is a side view of the carriage assembly.

FIG. 4 is a perspective view of the board unit.

FIG. 5 is an enlarged plan view showing a connection portion of a main FPC of the board unit.

FIG. 6 is a plan view schematically showing a state where a connection portion of a main FPC is fixed to the carriage assembly.

FIG. 7 is a perspective view showing a relay FPC.

FIG. 8 is a side view showing a state where the relay FPC is soldered to a main FPC.

FIG. 9 is a perspective view showing a relay FPC portion of the head unit.

FIG. 10 is a side view showing a connection process of the head unit.

FIG. 11 is a perspective view showing a head unit according to another embodiment of the present invention.

FIG. 12 is a perspective view showing a jig for fixing a solder material to a head lead wire of the head unit.

FIG. 13 is a side view showing a step of connecting the head unit according to the other embodiment to a main FPC.

[Explanation of symbols]

12a, 12b, 12c Magnetic disk 14 Carriage assembly 16 Voice coil motor 17 Substrate unit 18 Bearing assembly 26a, 26b, 26c, 26d, 26e, 26f Arm 27a, 27b Spacer ring 28 Magnetic head assembly Solid 32 ... Magnetic head 46 ... Head lead wire 56 ... Main FPC 60 ... Connection pad 70 ... Relay FPC 72 ... Base plate 73 ... Conductor pattern 74 ... First relay pad 76 ... Second relay pad 90 ... Solder material 92 ... Head unit

Claims (7)

[Claims] An extended end of a plurality of head lead wires derived from a magnetic head is electrically connected to each other by a conductive material and short-circuited, and the extended end of the short-circuited head lead wire is fixed to a carriage body. A method of assembling a carriage assembly, comprising: positioning and mounting the connection lead on a printed circuit board; and soldering the extended end of the positioned lead wire to the connection pad. 2. A head-shaped lead wire is short-circuited by joining a bar-shaped solder material to the extended end while maintaining the extended ends of the plurality of head lead wires in the same arrangement relationship as the connection pads. 2. The carriage assembly according to claim 1, wherein, at the time of the soldering, the solder material is melted to solder an extended end of the head lead wire to the connection pad, and the short circuit is released. Assembly method. 3. A relay flexible printed circuit board provided with a plurality of first relay pads and a plurality of second relay pads respectively connected to the first relay pads, and a plurality of head lead wires derived from a magnetic head. Are connected to the first relay pads of the relay flexible printed circuit board, respectively, and the second relay pads of the relay flexible printed circuit board are electrically connected to each other by a conductive material to be short-circuited. A method of assembling a carriage assembly, comprising: positioning a pad on a connection pad of a flexible printed circuit board fixed to a carriage body; and soldering the positioned second relay pad to the connection pad. 4. A bar-shaped solder material is joined to the plurality of second relay pads to short-circuit the head lead wires. At the time of soldering, the solder material is melted and
The method according to claim 3, wherein the relay pad is soldered to the connection pad and the short circuit is released. 5. A head unit used for assembling a carriage assembly, comprising: a magnetic head; a plurality of head lead wires derived from the magnetic head; and a conductive member short-circuited by connecting extending ends of the head lead wires to each other. A head unit comprising: 6. A head unit used for assembling a carriage assembly, comprising: a magnetic head; a plurality of head leads derived from the magnetic head; and a plurality of first leads connected to extending ends of the plurality of head leads. A relay flexible printed circuit board having a relay pad, a plurality of second relay pads respectively connected to the first relay pads, and a conductive member short-circuited by connecting the plurality of second relay pads to each other. A head unit, characterized in that: 7. The head unit according to claim 5, wherein the conductive member is made of a rod-shaped solder material.