JP2832148B2 - Optical pickup device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device and, more particularly, to a structure of a coil unit suitable for increasing the sensitivity and reducing the size of the optical pickup device.

[0002]

2. Description of the Related Art Conventionally, in a drive apparatus for an optical recording medium such as a CD-ROM, and a magneto-optical recording medium such as an MO disk, an optical pickup device for reading or writing information recorded on the disk is used. Is provided. This optical pickup device is provided with a movable unit containing a lens body supported movably in a focus direction and a tracking direction, and the movable unit is operated by a magnetic force of a drive coil to focus on a recording layer of a disk. And a tracking operation. This drive coil is disclosed in
As disclosed in No. 3, a plurality of power supply wirings are formed on the outer peripheral surface of the movable unit, and power supply wiring formed by a printed wiring pattern or the like is mounted on these drive coils.

[0003]

In the above-described conventional optical pickup device, the power supply wiring is conductively connected to the winding end of the drive coil by solder or the like after the drive coil is fixed on the outer peripheral surface of the movable unit. , The production work is complicated,
Since automation of assembly is also difficult, there is a problem in that mass production is lacking and manufacturing costs increase. On the other hand, due to the recent increase in density of recording media and speeding up and miniaturization of drive devices, high sensitivity and miniaturization of optical pickups are also required. However, conventionally, a circularly wound coil or a sheet coil has been used as a driving coil,
High sensitivity because the coil occupancy rate is low and the drive coil thickness is large because of the insulating film of the winding in the case of a round coil and the multilayer structure to secure the number of turns in the case of a sheet coil. There is a problem that both miniaturization and miniaturization are difficult. Therefore, the present invention has been made in view of the above problems, and its problems are as follows.
An object of the present invention is to realize a coil unit having high mountability, being thinner, and having high magnetic characteristics, and using the coil unit to achieve both high sensitivity and miniaturization of an optical pickup.

[0004]

Means taken by the present invention to solve the above-mentioned problem is that a flexible wiring board provided with a power supply wiring layer and a conductive film are wound around one end face. A coil unit fixedly abutted on the surface of the substrate, and a coil unit in which the power supply wiring layer is conductively connected to a winding end of the ribbon coil.
The knitted flexible wiring board is connected to the axis of the movable unit.
The coil unit is mounted on the peripheral surface formed around the wire.
Drive coil of the movable unit
An optical pickup apparatus is characterized in that the the. Here, the peripheral surface includes an outer peripheral surface of the movable unit itself or an inner peripheral surface of a member surrounding the movable unit.

[0005] Here, an exposed portion for connection of the power supply wiring layer is disposed immediately below or inside the inner peripheral surface of the ribbon coil and directly below or outside the outer peripheral surface of the ribbon coil. It is preferable to conduct conductive connection between the inner peripheral surface and the outer peripheral surface using a conductive connection material.

It is preferable that the end surface of the ribbon coil is formed so as to conform to the shape of the mounting surface of the flexible wiring board.

In some cases, the coil unit may have at least a pair of strip coils opposing or opposed to each other on the peripheral surface.

[0008]

[0009]

According to the first aspect, the ribbon coil is fixed on the flexible substrate, and the power supply wiring layer and the winding end of the ribbon coil are conductively connected, so that the connection operation of the coil unit is easy. In addition, the thinning of the coil unit and the high magnetic properties can be achieved at a high level. In addition, since the coil unit is mounted on the movable unit of the optical pickup device by mounting the flexible wiring board, automation of production or improvement in mass production efficiency can be achieved by improving the mounting property, and the production cost can be reduced. In addition, the thinning of the coil unit and the high magnetic properties make it possible to achieve both miniaturization and high sensitivity of the optical pickup device.

According to the second aspect, the inner peripheral surface or the outer peripheral surface of the ribbon coil and the connecting exposed portion disposed immediately below, inside or outside the inner peripheral surface or the outer peripheral surface are formed by the conductive connecting material. Since the conductive connection is made, the conductive connection work becomes extremely easy and reliable connection is possible, the connection work can be automated, and disconnection due to poor connection or bending of the flexible wiring board can be prevented. it can.

According to the third aspect, since the end surface of the thin coil is formed so as to conform to the shape of the mounting surface of the flexible wiring board, the mountability on the mounting surface is improved, and the flexible wiring board is bonded to the mounting surface. When the flexible wiring board is mounted, it is possible to avoid applying stress to the conductive connecting portion or the fixed portion between the ribbon coil and the flexible wiring board due to the bending of the flexible wiring board. Can be prevented.

[0012]

More specifically, in order to increase the space factor (volume ratio of the conductor) and the number of turns of the ribbon coil, a semi-curing insulating resin layer having an adhesive function is used as the ribbon coil. Is preferably adhered to a conductive foil and wound on the conductive foil. Further, it is desirable to form an electric insulating film on the end face of the thin coil in order to secure insulation.

[0014] The coil unit is, in particular, a step of forming the end face of the ribbon coil according to the mounting surface shape of the flexible wiring board, and forming the ribbon coil in a state where the end face is in contact with the surface of the flexible wiring board. The step of attaching to the flexible wiring board, and the inner and outer peripheral surfaces of the ribbon coil,
Conducting a conductive connection with a conductive connecting material between the power supply wiring layer and the exposed portion for connection of the power supply wiring layer disposed immediately below or inside the inner peripheral surface and directly below or outside the outer peripheral surface, respectively. Is preferred.

In this case, in the step of conductively connecting, a step of applying a conductive heat-flowable material such as cream solder to the inner and outer peripheral surfaces of the ribbon coil, It is preferable that the material be fluidized to conduct conductive connection between the inner and outer peripheral surfaces of the ribbon coil and the exposed portion for connection. A conductive connection may be made between the inner and outer peripheral surfaces of the ribbon coil and the exposed portion for connection by applying or dropping a conductive paste. By doing so, the connection process can be automated and reliable conductive connection can be made, so that poor connection, disconnection accident, etc. can be prevented.

In the step of forming the end face of the ribbon coil in conformity with the shape of the mounting surface of the flexible wiring board, it is preferable to press-mold the end surface of the thin coil using a forming die which is formed substantially identical to the mounting surface. However, when cutting out the ribbon coil, it is also possible to cut the wound body of the conductive film in accordance with the mounting surface shape. In the step of attaching the thin coil to the flexible wiring board, it is preferable to extend the flexible board on the surface of the holder formed substantially in the same shape as the mounting surface, and bond the formed thin coil in this state. In this case, if the ribbon coil whose end surface is not formed and the flexible wiring board on the holder are brought into contact with each other via an adhesive material and pressed by the above-mentioned mold, the end surface of the ribbon coil can be formed. And the step of attaching the ribbon coil to the flexible wiring board can be performed simultaneously.

[0017]

Next, an embodiment of a coil unit according to the present invention will be described with reference to the drawings. As shown in FIG. 1, this coil unit is fixed on a flexible wiring board FPC in which a wiring pattern 2 made of a plurality of copper foils is formed on a base 1 made of a strip-shaped polyimide resin, and on the flexible wiring board FPC. And a pair of tracking drive coils 32, 32 similarly fixed. As shown in FIG. 2, the flexible wiring board FPC has a wiring pattern 2 formed by printing on a base 1 and a resist 3 covering the wiring pattern 2.

At the center of the flexible printed circuit board FPC,
A terminal portion 1a having a narrow width shown in FIG. 1 is formed, and an end portion of the wiring pattern 2 is arranged in a concentrated manner, and an input pad 20 not covered with the resist 3 is formed thereon. The other ends of the wiring pattern 2 are disposed inside and outside the focus driving coil 31 and the tracking driving coil 32, respectively, and the connection pads 2 not covered with the resist 3
1 and 22 are formed.

The focusing drive coil 31 and the tracking drive coil 32 are thin ribbon coils formed by winding a conductive metal foil such as a copper foil. This ribbon coil is manufactured as follows. One or both surfaces of the metal foil are coated with a resin insulating layer and a resin adhesive layer, and are wound around a core jig to form a rod-shaped wound body. This wound body is completely adhered and solidified by curing the resin adhesive layer with heat or ultraviolet rays in the firing step. Thereafter, the core jig is removed, and the wound body is sliced with a wire saw or the like to obtain a thin coil. Is formed.
After slicing, burrs are removed by etching or the like in order to prevent a short circuit at the coil end surface (cut).

In a thin coil, the thickness of the metal foil is usually about several tens of microns, and the total thickness of the resin insulating layer and the resin adhesive layer is about 7 to 8 μm. In order to increase the space factor of the coil, it is necessary to reduce the total thickness of the resin insulating layer and the resin adhesive layer, and to increase the number of turns, it is necessary to reduce the thickness of the metal foil. Particularly, a mixture of a semi-curing insulating material having an adhesive function, for example, an epoxy resin, a rubber-modified epoxy resin, and imidazole was mixed (for example, in a weight ratio of 70:30:45 or 5 in order of weight ratio).
0:50:40, particularly preferably 70:30:45. ) When resin is used as an insulating material and an adhesive, a high-quality coil can be manufactured even if the thickness of the metal foil is reduced to about 4 to 5 μm and the thickness of the resin layer is reduced to about 1 to 2 μm. , A high space factor of 80% or more can be obtained.

In this case, the manufacturing steps include a step of coating the above-mentioned resin on a metal foil, and
A step of pre-baking at about 150 ° C. to semi-harden the resin, a step of winding around a core jig to form a roll, a step of firing the roll at 120 to 200 ° C., and a roll Is provided. In addition, PA
A high-density insulating layer made of I (polyamideimide) resin having a thickness of about 1 μm is formed, and one or other surface of the metal foil is coated with the semi-curable resin to a thickness of about 1 μm to form an insulating layer. In addition, it is possible to avoid poor insulation due to pinholes and the like while suppressing the thickness of the adhesive layer. However, in this case, it is a matter of course that other adhesives may be used instead of the semi-curable resin as long as the adhesive layer can be made sufficiently thin. In addition, as the adhesive layer,
Instead of the semi-curable resin, a method of using a thermoplastic resin such as a nylon-based, polyolefin-based, or esterimide resin and curing the wound body by a curing process may be employed.

The focus driving coil 31 and the tracking driving coil 32 are formed and attached as follows. On one or both end faces of the ribbon coil formed as described above (the slice width, that is, the thickness of the ribbon coil is about 0.2 mm), an electric material made of an epoxy resin or a phenol resin shown in FIG. An insulating film 35 is formed. Next, the ribbon coil is press-formed using a mold formed according to the shape of the ribbon coil. This molding step is performed, for example, when the mounting surface of the focus driving coil 31 and the tracking driving coil 32 is a curved surface.
Molding is performed so that the end surface of the ribbon coil on which the electric insulating film is applied has a similar curved surface.

In this case, when slicing the wound body, it is possible to cut the wound body so that the end face has the same shape as the mounting surface. For example, when cutting with a multi-wire saw, the direction of movement of a support that is movably mounted to support the wound body and gradually press the wound body against the wire is moved toward the wire. Not only that, but also by moving the wound body obliquely back and forth in the axial direction, the cut surface (the end surface of the ribbon coil) can be cut into a cylindrical shape.

Finally, in accordance with the positions of the connection pads 21 and 22 formed on the surface of the flexible wiring board FPC, the insulating film on the winding end surface existing on the inner and outer peripheral surfaces of the ribbon coil is removed. The tracking drive coil 32 having the connection surface portions 32a and 32b shown in FIG. 2 is formed by removing by a physical treatment such as polishing or a chemical treatment such as etching. The same applies to the processing for the focus drive coil 31.

The focus driving coil 31 and the tracking driving coil 32 formed in this manner are electrically insulated from the electric insulating film 3 corresponding to the positions of the connection pads 21 and 22.
5 is adhered with an adhesive or the like so that the end surface (the end surface formed into a shape corresponding to the mounting surface) is aligned with the surface of the flexible wiring board FPC. At this time, as shown in FIG. 3, a holder H having a surface formed according to the shape of the mounting surface of the flexible printed circuit board FPC is used.
Is prepared, a flexible wiring board FPC is temporarily attached to the surface of the holder H by an adhesive or the like, and the end faces of the drive coils 31 and 32 are adhered to the temporarily attached substrate surface, thereby providing a flexible wiring. The board FPC and the drive coil can be securely fixed. It should be noted that it is also possible to form the ribbon coil simultaneously with mounting on the flexible wiring board. That is, an adhesive is applied to the end surface of the ribbon coil, the end surface to which the adhesive is applied is housed in the molding die M such that the end surface is exposed, and the molding die M is temporarily attached to the holder H on the flexible wiring board FPC. When the ribbon coil is pressed against the flexible wiring board, the ribbon coil is pressed and adhered, and at the same time, the ribbon coil is formed into a desired shape by being sandwiched between the mold M and the surface of the flexible wiring board.

The connection surface portions 32a and 32b of the focus drive coil 31 and the tracking drive coil 32 fixed on the flexible printed circuit board FPC are connected to the connection pads 2
The connection pads 22 are located above the edges of the connection surface portions 1 and 22, that is, directly below or inside the connection surface portion 32 a as shown in FIG. 2 or FIG.
The connection pads 22 are respectively disposed so as to be located immediately below or outside of “b”. For example, in the tracking drive coil 32, the connection between the connection surface portions 32 a and 32 b and the connection pads 22 and 22 is conductively connected by the solders 33 and 34. In this connection method, for example, as shown in FIG. 4 (a), cream solder is supplied to the connection surface portion 32b from a nozzle having an outlet facing the connection surface portion 32b, and is applied thereto. As shown in (b), the cream solder is melted by the reflow process and flows down onto the connection pad 22, thereby allowing the connection between the connection surface portion 32b and the connection pad 22 to be naturally connected. Here, as the connection material, a conductive paste such as silver wax can be used. In this case, the conductive paste is applied between the connection surface portions 32a, 32b and the connection pads 22, 22, or the nozzle N
It is dripped from.

Since the coil unit manufactured as described above is formed of a thin ribbon coil conductively connected to the flexible substrate FPC, the number of turns is smaller than that of a conventional round wound coil or sheet coil even if it is made thinner. As a result, a remarkable effect that both miniaturization of various devices and high sensitivity can be achieved can be achieved. When compared with drive coils having the same drive performance, for example, a round wound coil has a thickness of 0.5 mm due to winding of a coated wire, and a sheet coil has a thickness of 0.22 mm in two or more layers in order to secure the number of turns. It is necessary to laminate four layers, and in any case, a thickness of about 0.5 mm or more is required. On the other hand, in the present embodiment, it is possible to achieve a driving characteristic exceeding that of a round-wound coil or a sheet coil having the above-described dimensions even with a thin coil having a thickness of 0.2 mm as described later.

FIG. 5 is a schematic plan view showing a state where the coil unit of this embodiment shown in FIG. 1 is applied to an optical pickup device of a CD-ROM drive. Here, the outer yoke plate 43, the inner yoke plate 44, and the support shaft 45 are integrated with each other, and the movable unit 4 supported by the support shaft 45 is supported.
Reference numeral 6 is attached so as to be movable in the axial direction of the support shaft 45 and to be rotatable around the axis. The movable unit 46 has a holding frame 47, and the objective lens 48 is accommodated in the holding frame 47. A pair of focusing magnets 49, 49 facing each other and a pair of similar tracking magnets 50, 50 are fixed to the inner peripheral surface of the outer yoke plate 43. The coil unit CU includes the movable unit 46.
The drive coil 3 for focusing is adhered to the outer peripheral surface of the
Reference numerals 1 and 31 are disposed so as to face the focusing magnets 49 and 49, and the tracking drive coils 32 and 32 are disposed so as to face the tracking magnets 50 and 50, respectively.

When the coil unit CU is mounted on the optical pickup device shown in FIG. 5, the coil unit CU is bonded and fixed in a state of being curved along the outer peripheral surface of the movable unit 46. A stress due to the deformation of the substrate is applied to the connection portions of the coils 32, 32, which may cause disconnection of the connection portions and peeling of the coils. Therefore, as described above, by forming the fixed-side end surface of the ribbon coil into a circumferential surface corresponding to the curvature of the outer peripheral surface of the movable unit 46 by press molding during coil production, disconnection accompanying mounting to the movable unit 46 is performed. And peeling can be prevented.

As described above, the ribbon coil formed into a shape conforming to the movable unit 46 is a flexible wiring board C
As shown in FIG. 6, the flexible wiring board is bent according to the curvature of the end surface of the thin coil, so that poor adhesion between the coil and the board does not occur. In addition, since the flexible wiring board itself is also bent in accordance with the deformation of the ribbon coil, the attaching operation becomes easy particularly when the flexible wiring board is attached on a curved surface.

As described above, since the present embodiment has a structure in which the thin coil is fixed on the flexible substrate, it is possible to easily attach the thin coil and connect the wiring, and also to make the coil unit thin. And high magnetic characteristics can be compatible. In addition, since the end surface of the ribbon coil is shaped to match the mounting surface of the flexible board, it is possible to improve the mounting properties, and it can be securely mounted on any mounting surface, and even if the mounting surface with a small curvature is disconnected, Accidents such as peeling can be prevented.

By using such a coil unit in an optical pickup device (lens actuator), the complexity in mounting the coil can be avoided and automation can be performed, so that the manufacturing cost can be reduced. Further, based on the thinness and high magnetic performance of the coil unit, the size and sensitivity of the optical pickup device can be reduced, and high-speed operation of the pickup can be realized. By the way, when the coil unit CU provided with the 0.2 mm-thick ribbon coil of the present embodiment is used for the optical pickup device, a round-wound coil or a sheet coil having a thickness of about 0.5 mm is used. The operation speed can be obtained about 1.5 to 1.7 times as fast as that of the first embodiment.

[0033]

As described above, according to the present invention, the ribbon coil is fixed on the flexible substrate, and the power supply wiring layer and the winding end of the ribbon coil are conductively connected. The mounting and connection work of the unit can be facilitated to reduce the manufacturing cost, and the coil unit can be made thinner and have high magnetic characteristics at a high level.

[Brief description of the drawings]

FIGS. 1A and 1B are a plan view and a sectional view showing the structure of an embodiment of a coil unit according to the present invention.

FIG. 2 is an enlarged cross-sectional view showing, on an enlarged scale, a mounting portion of the thin coil in the embodiment.

FIG. 3 is an explanatory view showing a method of bonding a flexible wiring board and a drive coil in the embodiment.

FIGS. 4A and 4B are explanatory diagrams showing a method for electrically connecting a drive coil and a wiring pattern in the embodiment. FIGS.

FIG. 5 is a schematic plan view showing a schematic structure of an embodiment of an optical pickup device equipped with an embodiment of a coil unit according to the present invention.

FIG. 6 is a side view showing a shape of a coil unit adapted to the optical pickup device shown in FIG.

[Explanation of symbols]

 FPC flexible wiring board CU Coil unit 1 Base 2 Wiring pattern 3 Resist 20 Input pad 21, 22 Connection pad 31 Focus drive coil 32 Tracking drive coil 32a, 32b Connection surface 33, 34 Solder 46 Movable unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) G11B 7/08-7/095 H01F 5/00-5/06 H01F 15/02 H05K 1/18

Claims (4)

(57) [Claims] 1. A flexible wiring board provided with a power supply wiring layer, and a ribbon coil formed by winding a conductive film and fixed with one end face in contact with the substrate surface, A coil unit in which the power supply wiring layer is conductively connected to a winding end of the ribbon coil;
The flexible wiring board is formed around the axis of the movable unit.
On the formed peripheral surface, and
An optical pickup device , wherein a band coil is a driving coil of the movable unit . 2. The connection exposure section according to claim 1, wherein a connection exposure portion of the power supply wiring layer is disposed immediately below or inside an inner peripheral surface of the ribbon coil and directly below or outside an outer peripheral surface of the ribbon coil. An optical pickup device , wherein a portion and an inner peripheral surface and an outer peripheral surface of the ribbon coil are conductively connected with a conductive connecting material. 3. The method of claim 1, wherein the end face of the ribbon coil, light pitch, characterized in that it has been formed into a shape is matched to the mounting surface shape of the flexible wiring board
Backup device . 4. The coil unit according to claim 1, wherein
In addition, on the peripheral surface,
An optical pickup device, wherein a pair of ribbon coils are fixed .