JPH11250593A - Magnetic disk device and flexible printed circuit board unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic disk device and a flexible printed circuit board unit in which electrostatic breakdown of a magnetic head at the time of manufacturing can be effectively prevented. SOLUTION: A FPC unit 17 of a magnetic disk device is provided with FPC 32, a connection end part 32a of the FPC 32 is mounted to a carriage assembly 14, while connected electrically to a magnetic head 26. A base end part 32b of the FPC 32 is fixed to a stiffener plate 34, and mounted to a case through this stiffener plate 34. This reinforce plate 34 has a base material consisting of a metal and a surface layer coating a surface of a base material, and the surface layer is formed with a material of volume resistivity 10<2> -10<9> Ωcm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic disk drive, and more particularly to a magnetic disk drive in which a magnetic head supported by a carriage assembly is connected to a control unit via a flexible printed circuit board unit, and a flexible printed circuit board unit. .

[0002]

2. Description of the Related Art In general, a magnetic disk drive includes a magnetic disk disposed in a case, a spindle motor for supporting and rotating the magnetic disk, a carriage assembly for supporting a magnetic head, a voice coil motor for driving the carriage assembly, A flexible printed circuit board unit (hereinafter, referred to as an FPC unit) for electrically connecting the magnetic head to the control unit is provided.

[0003] The carriage assembly includes a bearing mounted on a case, and a plurality of arms extending from the bearing. A magnetic head is mounted on each arm via a suspension. The signal line of each magnetic head is routed on the arm to the bearing.

[0004] The FPC unit has an elongated flexible printed circuit board (hereinafter, referred to as FPC) having a connection end portion fixed to the arm side of the carriage assembly and a base end portion fixed to the case side. The signal line extending from the FPC is soldered to the connection end of the FPC. In addition, a reinforcing plate is attached to the base end of the FPC, and a head IC, a connector, a preamplifier, and the like are mounted. The base end of the FPC is fixed to the case via a reinforcing plate, and the connector is connected to a control circuit board mounted on the outer surface of the bottom wall of the case. Thus, each magnetic head is electrically connected to the control circuit board via the FPC unit, and is controlled by the control circuit board.

[0005] Generally, the reinforcing plate of the FPC unit is formed of plastic, aluminum, or the like, and is fixed to the FPC via an adhesive layer. As the adhesive layer, a resin adhesive, a double-sided tape, or the like is used. Further, when the base material of the reinforcing plate is formed of a metal such as stainless steel, F
The PC and the reinforcing plate can also be thermocompression bonded.

[0006]

When the reinforcing plate is made of a general plastic, the plastic has a high volume resistivity of 10 ¹² Ωcm or more. Therefore, once the reinforcing plate is charged once, it generates ions such as an ionizer. The charged state is maintained unless the electricity is forcibly removed by a container. When manufacturing a magnetic disk drive, an operator uses conductive gloves to
If the reinforcing plate of the FPC unit is frictionally charged by gloves when the PC unit is gripped, the reinforcing plate continues to maintain a charged state, so that the signal line of the FPC connecting the magnetic head and the head IC performs induction charging. Wake up. And F
If the FPC and the magnetic head are connected while the signal line of the PC is inductively charged, the magnetic head may be damaged by static electricity.

When the reinforcing plate is made of a metal such as aluminum, the volume resistivity of the metal such as aluminum is as low as 10 ⁻⁵ Ωcm or less, so that when the charged reinforcing plate comes into contact with another metal object. Then, the electric charge is rapidly moved by the discharge, and the reinforcing plate is discharged. During the manufacture of a magnetic disk drive, when a worker grips an FPC unit using conductive gloves and frictionally charges a reinforcing plate made of metal with the gloves, the reinforcing plate is made of another metal object, for example, a metal. When it comes into contact with the jig, the charged electric charge of the reinforcing plate rapidly flows into the metal object before being discharged through the conductive gloves of the worker. Therefore, in the signal line of the FPC,
Induction charging due to frictional charging of the reinforcing plate and discharge due to contact with a metal object occur instantaneously and continuously. Therefore, the magnetic head may be damaged by static electricity due to this effect.

In particular, a magnetic head using an ultrathin film, such as an MR head or a GMR head, is very weak against static electricity, and when a reinforcing plate made of plastic or aluminum is used as described above, static electricity is There is a problem that destruction easily occurs.

An object of the present invention is to provide a magnetic disk drive and a flexible printed circuit board unit which can effectively prevent electrostatic damage of a magnetic head.

[0010]

To achieve the above object, a magnetic disk drive according to the present invention includes a case, a drive motor provided in the case and supporting and rotating the magnetic disk. A magnetic head for recording and reproducing information on and from the magnetic disk, a carriage assembly provided in the case and supporting the magnetic head movably with respect to the magnetic disk, and a magnetic head mounted on the carriage assembly and mounted on the magnetic head. A flexible printed circuit comprising: a connected printed end, a flexible printed circuit board having a base end on which circuit components are mounted, and a reinforcing member fixed to the base end and attached to the case. And a circuit board unit, wherein at least the exposed surface of the reinforcing member has a volume resistivity of 1 It is characterized in that it is formed in ² to 10 ⁹ [Omega] cm.

The reinforcing member has a base made of metal or insulating resin, and a surface layer covering the base.
The surface layer is formed of a material having a volume resistivity of 10 ² to 10 ⁹ Ωcm.

Further, the surface layer is formed of one of a conductive plastic film using a conductive polymer or a conductive filler and a conductive paint film using a conductive filler.

Further, according to the present invention, the reinforcing member is formed entirely of a conductive plastic having a volume resistivity of 10 ² to 10 ⁹ Ωcm.

According to the magnetic disk drive and the flexible printed circuit board unit having the above-described structure, the surface or the whole of the reinforcing member has a volume resistivity of 10 ² to 10 ⁹ Ωcm. Even when the plate is in contact with a metal jig or the like in a charged state, the plate is gradually discharged. Therefore, a sudden discharge current does not flow through the signal line of the flexible printed circuit board, and electrostatic breakdown of the magnetic head can be effectively prevented.

After the discharge, the reinforcing plate itself remains uncharged, so that the signal lines and circuit components of the flexible printed circuit board are not inductively charged, thereby preventing the magnetic head from being damaged by static electricity.

According to the present invention, when a base material made of metal is used for the reinforcing member, it is possible to shield the noise that tends to enter from the circuit components of the flexible printed circuit board by the reinforcing member. Further, when the entire reinforcing member is formed of conductive plastic, the manufacturing cost can be reduced by simplifying the structure.

The conductivity of the reinforcing member is determined by the physical properties of the material used. The conductivity does not change due to humidity or the like, the discharge current is stabilized, and contamination by bleed such as a surfactant is prevented. it can.

Further, when an insulating resin is used as the base material of the reinforcing member, for example, when a general-purpose plastic is used as the insulating resin, the physical properties of the general-purpose plastic such as specific gravity, strength, and expansion coefficient can be used as it is. it can.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a magnetic disk drive of the present invention is applied to a hard disk drive (hereinafter referred to as an HDD) will be described in detail with reference to the drawings. As shown in FIG. 1, the HDD has a rectangular box-shaped case 10 with an open upper surface, and a top cover (not shown) that is screwed to the case with a plurality of screws and closes an upper end opening of the case. .

In the case 10, two magnetic disks 12a and 12b as magnetic recording media, a spindle motor 13 for supporting and rotating these magnetic disks,
A plurality of magnetic heads for recording and reproducing information on and from a magnetic disk;
a carriage assembly 14 movably supported with respect to a and 12b, a voice coil motor (hereinafter referred to as VCM) for rotating and positioning the carriage assembly.
16 and a flexible printed circuit board unit (hereinafter, referred to as an FPC unit) 17 on which circuit components such as a head IC and a preamplifier are mounted.

On the outer surface of the case 10, a spindle motor 13, a VCM 16,
And printed circuit board 1 for controlling operation of magnetic head
5 is screwed and located opposite the bottom wall of the case.

Each of the magnetic disks 12a and 12b has a diameter of 6
It is formed to 5 mm (2.5 inches) and has a magnetic recording layer on the upper and lower surfaces. Two magnetic disks 12a,
Numerals 12b are coaxially fitted to a hub (not shown) of the spindle motor 13, and are laminated at predetermined intervals along the axial direction of the hub. Then, the magnetic disk 12
a and 12b are driven to rotate at a predetermined speed by a spindle motor 13.

As shown in FIGS. 1 and 2, the carriage assembly 14 extends from the bearing assembly 18 in parallel with the bearing assembly 18 as a bearing fixed on the bottom wall of the case 10. Four arms 20a, 20b, 20c, and 20d rotatably supported with each other, and four magnetic head assemblies 22 supported at the tips of the arms.
And

Each magnetic head assembly 22 includes an elongated suspension 24 formed by a leaf spring, and a magnetic head 26 fixed to the suspension. The suspension 24 has its base end fixed to the distal ends of the arms 20a to 20d by spot welding or bonding, and extends from the arm. Each magnetic head 26 is configured as, for example, an MR (magnetoresistive) head, and a signal line 28 derived from the magnetic head is connected to the bearing assembly 18 along the suspension 24 and the arms 20a (20b to 20d).
Extending to

The carriage assembly 14 has a support frame (not shown) extending from the bearing assembly 18 in a direction opposite to the arms 20a to 20d. The support frame has a voice (not shown) constituting a part of the VCM 16. The coil is fixed.

With the carriage assembly 14 configured as described above incorporated in the case 10, the magnetic disk 12a is positioned between the arms 20a and 20b.
The magnetic disk 12b is located between the arms 20c and 20d. The magnetic head 26 attached to the arms 20a and 20b 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 26 attached to the arms 20c and 20d contact the upper and lower surfaces of the magnetic disk 12b, respectively, and hold the magnetic disk 12b from both sides.

The voice coil fixed to the support frame of the carriage assembly 14 is located between a pair of yokes 30 fixed on the case 10, and is provided together with these yokes and a magnet (not shown) fixed to one of the yokes. The VCM 16 is configured. Then, by energizing the voice coil, the carriage assembly 14 rotates, and the magnetic head 26 moves the magnetic disks 12a, 12b
It is moved and positioned on the desired track above.

On the other hand, the FPC unit 17 is an elongated flexible printed circuit board (hereinafter, referred to as FPC) 3.
2 and a reinforcing plate 34 fixed to one end of the FPC. Specifically, the FPC 32 is formed in a substantially strip shape, and has a connection end portion 32a attached to the bearing assembly 18 of the carriage assembly 14 and an L-shaped bent end portion 32b. . And FPC32
Is formed of a conductor pattern and has a connection end 32a and a base end 32.
b and a large number of signal lines 36 extending between them.

A large number of connection pads (not shown) are formed at the connection end 32a, and head signal lines 28 derived from the magnetic head 26 are soldered to these connection pads. In addition, at the base end 32b of the FPC 32,
A plurality of circuit components, for example, a head IC 40 for controlling a current for performing recording and reproduction of the magnetic head 26, a connector 42, and the like are mounted. These circuit components are connected to the signal line 36 of the FPC 32 and the head signal line 2.
8 and is electrically connected to each magnetic head 26.

The reinforcing plate 34 functioning as a reinforcing member is formed in a substantially L-shape, and is bonded and fixed to the surface of the base end 32b of the FPC 32 opposite to the surface on which the circuit components are mounted. The reinforcing plate 34 is bonded and fixed on the inner surface of the bottom wall of the case 10. By providing the reinforcing plate 34, the FPC
32 can be fixed to the case 10 stably, and when the carriage assembly 14 rotates,
The smooth movement of the PC 32 can be maintained.

The connector 42 is connected to the printed circuit board 15 through the reinforcing plate 34 and the bottom wall of the case 10. Thus, the magnetic head 26 is electrically connected to the printed circuit board 15 via the FPC unit 17.

As shown in FIG. 2 and FIG.
Is composed of a base material 50 made of a metal such as stainless steel and a surface layer 52 formed so as to cover the surface of the base material. The surface layer 52 has a volume resistivity of 10 ² to 1.
⁰⁹ , desirably, a material having a volume resistivity of 10 ⁶ to 10 ⁸ . In the present embodiment, the surface layer 52 is made of, for example, a volume resistivity 1 having an electron conjugated system.
A conductive plastic film using a conductive polymer or a conductive filler of 0 ² to 10 ⁹ , or a volume resistivity of 10 ²
It is formed of a conductive coating film using 10 ⁹ of the conductive filler.

The base end 32b of the FPC 32 is adhered to the reinforcing plate 34 by an adhesive layer 54. As the adhesive layer 54, for example, a resin adhesive or a double-sided tape is used. In addition, since the base material 50 of the reinforcing plate 34 is formed of metal, the reinforcing plate 34 and the FPC 32 can be fixed by thermocompression bonding without using the adhesive layer 54.

According to the HDD configured as described above,
The surface layer 52 of the reinforcing member 34 has a volume resistivity of 10 ² to 10 ^9.
For example, when assembling the carriage assembly 14 or assembling the carriage assembly into the case 10, the metal jig is held in a state in which the reinforcement plate is frictionally charged by gripping the reinforcement plate 34 when the carriage assembly 14 is assembled or the carriage assembly is incorporated into the case 10. In such a case, the charged electric charges accumulated in the reinforcing plate are gradually discharged without being rapidly discharged. for that reason,
Head IC 40-FPC signal line 36-Head signal line 28
-Induction charging in the electric path of the magnetic head 26 is also gradually released, so that no sudden discharge current flows through the magnetic head 26. Therefore, electrostatic breakdown of the magnetic head 26 can be effectively prevented.

After the discharge, the reinforcing plate 34 itself is kept uncharged, so that the signal line 36 of the FPC 32 and the circuit components are not inductively charged, thereby preventing the magnetic head 26 from being damaged by static electricity. By preventing partial electrostatic destruction during HDD manufacturing, deterioration or change in electromagnetic conversion characteristics such as generation of Barghausen noise of the magnetic head, asymmetry of output, and shortening of the life of the MR film is reduced, and reliability is reduced. A high HDD can be provided.

The reinforcing plate 34 is provided with a base material 50 made of metal.
In the case where is used, it is possible to shield the noise that is going to enter from the circuit components of the FPC unit 17 by the reinforcing member 34. Furthermore, the conductive performance of the reinforcing plate 34 is:
It is determined by the physical properties of the material forming the surface layer 52, so that the conductive performance of the reinforcing plate does not change due to humidity, the discharge current can be stabilized, and contamination by bleed such as a surfactant can be prevented. Becomes possible.

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, the base material 50 of the reinforcing plate 34 is not limited to metal,
An insulating resin may be used. The reinforcing plate 3 having such a configuration
4, the same operation and effect as in the above embodiment can be obtained. When a general-purpose plastic is used as the insulating resin, for example, the physical properties of the general-purpose plastic such as specific gravity, strength, and expansion coefficient can be used as it is.

As shown in FIG. 4, the reinforcing plate 34 may be entirely formed of a conductive plastic having a volume resistivity of 10 ² to 10 ⁹ Ωcm. In this case, the same operation and effect as those of the above-described embodiment can be obtained. In addition, since the reinforcing plate 34 is formed only of the conductive plastic, the manufacturing cost can be reduced, and compared with the case where metal is used,
The weight of the reinforcing plate can be reduced.

In addition, the material for forming the reinforcing plate 34 or the surface layer 52 is not limited to the above-described material as long as it has a volume resistivity of 10 ² to 10 ⁹ Ωcm, and can be variously deformed as necessary. It is. Also, the number of magnetic disks, the number of magnetic heads, and the like can be increased or decreased as necessary.

Further, in the above embodiment, the reinforcing plate 34 is provided only at the base end portion 32b of the FPC 32.
A reinforcing plate having the same configuration as described above may be fixed to the connection end portion 32a of the FPC, and may be attached to the carriage assembly via the reinforcing plate.

[0041]

As described above in detail, according to the present invention, at least the exposed surface of the reinforcing member fixed to the base end of the flexible printed circuit board has a volume resistivity of 10 ² to 1.
With 0 ⁹ [Omega] cm, can provide effectively prevent possible magnetic disk device and a flexible printed circuit board unit electrostatic breakdown of the magnetic head at the time of manufacture.

[Brief description of the drawings]

FIG. 1 is an exemplary perspective view showing the inside of an HDD according to an embodiment of the present invention;

FIG. 2 shows the carriage assembly and F of the HDD.
FIG. 3 is a perspective view showing a PC unit.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a cross-sectional view of a reinforcing plate according to a modification of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Case 12a, 12b ... Magnetic disk 14 ... Carriage assembly 16 ... Voice coil motor 17 ... FPC unit 18 ... Bearing assembly 22 ... Magnetic head assembly 26 ... Magnetic head 28 ... Head signal line 32 ... FPC 32a ... Connection end part 32b ... base end part 34 ... reinforcing plate 36 ... signal line 40 ... head IC 50 ... base material 52 ... surface layer 54 ... adhesive layer

Claims (10)

[Claims] 1. A case, a drive motor provided in the case and supporting and rotating the magnetic disk, a magnetic head for recording and reproducing information on and from the magnetic disk, A flexible assembly having a carriage assembly that movably supports the magnetic head with respect to the magnetic disk, a connection end attached to the carriage assembly and connected to the magnetic head, and a base end on which circuit components are mounted. A flexible printed circuit board unit comprising: a printed circuit board; and a reinforcing member fixed to the base end and attached to the case, wherein the reinforcing member has at least an exposed surface having a volume resistance. Rate 10 ²
A magnetic disk drive formed to have a thickness of from 10 to 10 ⁹ Ωcm. 2. The reinforcing member has a base made of metal and a surface layer covering the base, and the surface layer is formed of a material having a volume resistivity of 10 ² to 10 ⁹ Ωcm. 2. The magnetic disk drive according to claim 1, wherein: 3. The reinforcing member has a substrate formed of an insulating resin and a surface layer covering the substrate, wherein the surface layer has a volume resistivity of 10 ² to 10 ⁹ Ωcm. 2. The magnetic disk drive according to claim 1, wherein the magnetic disk drive is formed of a material having the same. 4. The surface layer is formed of any one of a conductive plastic film using a conductive polymer or a conductive filler, and a conductive paint film using a conductive filler. 4. The magnetic disk drive according to claim 2, wherein: 5. The magnetic disk drive according to claim 1, wherein the reinforcing member is entirely formed of a conductive plastic having a volume resistivity of 10 ² to 10 ⁹ Ωcm. 6. A flexible printed circuit board unit for electrically connecting a magnetic head to a circuit component in a magnetic disk drive, comprising: a connection end connected to the magnetic head; and a base end on which the circuit component is mounted. A flexible printed circuit board, and a reinforcing member fixed to the base end and attachable to the case of the magnetic disk drive, wherein the reinforcing member has at least an exposed surface with a volume resistivity of 10 ² to 10 ^9.
A flexible printed circuit board unit formed in Ωcm. 7. The reinforcing member has a base made of metal and a surface layer covering the base, and the surface layer is formed of a material having a volume resistivity of 10 ² to 10 ⁹ Ωcm. The flexible printed circuit board unit according to claim 6, wherein 8. The reinforcing member has a substrate formed of an insulating resin and a surface layer covering the substrate, wherein the surface layer has a volume resistivity of 10 ² to 10 ⁹ Ωcm. 7. The magnetic disk drive according to claim 6, wherein the magnetic disk drive is formed of a material having the same. 9. The method according to claim 1, wherein the surface layer is formed of one of a conductive plastic film using a conductive polymer or a conductive filler and a conductive paint film using a conductive filler. Item 7. The magnetic disk device according to item 7 or 8. 10. The magnetic disk drive according to claim 6, wherein the reinforcing member is entirely formed of a conductive plastic having a volume resistivity of 10 ² to 10 ⁹ Ωcm.