JPH07240032A - Coil unit and optical pickup device using the same - Google Patents

Abstract

PURPOSE:To miniaturize a device and to provide a high sensitive lens actuator by realizing a coil unit with a higher loading property to various devices, capable of thinning and provided with a higher magnetic characteristic and using it to an optical pickup device. CONSTITUTION:This device is provided with a flexible wiring board forming a wiring pattern 2 on a base 1, focusing drive coils 31, and tracking drive coils 32 stuck and fixed to the board. These drive coils 31, 32 are made by winding a metal foil and slicing it, and are provided with end surfaces beforehand press formed matching with the shape of the loading surface of the flexible wiring board. The inner peripheral surfaces and the outer peripheral surfaces of the drive coils 31, 32 are conduction connected to connecting pads 21, 22 of the wiring pattern 2 by soldering.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in a drive device for an optical recording medium such as a CD-ROM or a magneto-optical recording medium such as an MO disc, an optical pickup device for reading or writing information recorded on the disc is used. It is provided. This optical pickup device is provided with a movable unit that accommodates a lens body that is supported so as to be movable in the focus direction and the tracking direction. The movable unit is operated by the magnetic force of a drive coil to focus on the recording layer of the disc. Also, the tracking operation is performed. This drive coil is the actual Kai 61-18702
As disclosed in No. 3, a plurality of them are attached to the outer peripheral surface of the movable unit, and power supply wiring formed by a printed wiring pattern or the like is attached to these drive coils.

[0003]

In the above-mentioned conventional optical pickup device, after the drive coil is fixed on the outer peripheral surface of the movable unit, the power supply wiring is conductively connected to the winding end of the drive coil by soldering or the like. , The manufacturing work is complicated,
Since automation of assembly is also difficult, there is a problem that mass productivity is insufficient and manufacturing cost increases. On the other hand, due to the recent increase in the density of recording media and the increase in speed and size of drive devices, there is a demand for higher sensitivity and size reduction in optical pickups. However, conventionally, wound coils, sheet coils, etc. have been used as drive coils,
In the case of a round coil, the winding insulation film is used, and in the case of a sheet coil, the multilayer structure to secure the number of turns reduces the space factor of each coil and increases the thickness of the drive coil, resulting in high sensitivity. There is a problem in that both miniaturization and miniaturization are difficult. Therefore, the present invention has been made in view of the above problems, and its problems are
The object is to realize a coil unit that has high mountability, can be made thin, and has high magnetic characteristics, and to achieve both high sensitivity and downsizing of an optical pickup by using this coil unit.

[0004]

Means for Solving the Problems The means taken by the present invention to solve the above problems are formed by winding a flexible wiring board having a power supply wiring layer and a conductive film on one end surface. A thin strip coil fixed in contact with the surface of the substrate is provided, and the power supply wiring layer is conductively connected to the winding end of the thin strip coil.

Here, the exposed portion for connection of the power supply wiring layer is arranged immediately below or inside the inner peripheral surface of the thin strip coil and directly below or outside the outer peripheral surface, respectively. It is preferable to electrically connect the inner peripheral surface and the outer peripheral surface with a conductive connecting material.

Further, it is preferable that the end surface of the thin strip coil is formed in conformity with the shape of the mounting surface of the flexible wiring board.

Further, it is preferable that the flexible wiring board of the coil unit is mounted on the peripheral surface formed around the axis of the movable unit, and the thin coil of the coil unit is used as the driving coil of the movable unit. Here, the peripheral surface includes the outer peripheral surface of the movable unit itself or the inner peripheral surface of a member surrounding the movable unit.

In this case, at least one pair of thin ribbon coils, which are diametrically opposed or face each other on the peripheral surface, may be fixed to the coil unit.

[0009]

According to the first aspect of the present invention, since 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 coil unit can be easily connected. In addition, it is possible to make the coil unit thin and have high magnetic characteristics at a high level.

According to the second aspect, the inner peripheral surface or the outer peripheral surface of the ribbon coil and the exposed connection portion arranged immediately below or inside or outside the inner peripheral surface or the outer peripheral surface are formed by the conductive connecting material. Conductive connection makes conductive connection work extremely easy and reliable connection is possible, it is possible to automate connection work, and it is possible to prevent disconnection due to poor connection or bending of flexible wiring board etc. it can.

According to the third aspect of the present invention, the end face of the thin strip coil is formed so as to conform to the shape of the mounting surface of the flexible wiring board, so that the mounting ability on the mounting surface is improved and the flexible wiring board is bonded to the mounting surface. When mounting by, etc., it is possible to avoid applying stress to the conductive connection portion or the fixed portion between the thin coil and the flexible wiring board due to the bending of the flexible wiring board, so there is no accident such as disconnection of the conductive connection portion or peeling of the coil. Can be prevented.

According to the present invention, since the coil unit is mounted by mounting the flexible wiring board on the outer peripheral surface of the movable unit of the optical pickup device, it is possible to improve the mountability to automate the manufacturing or improve the mass production efficiency. Therefore, the manufacturing cost can be reduced, and at the same time, the coil unit can be made thin and the magnetic properties can be made small, and the optical pickup device can be made compact and highly sensitive.

More specifically, in order to increase the space factor (volume ratio of the conductor) and the number of turns of the thin strip coil, the thin strip coil is a semi-curable insulating resin layer which also has an adhesive function. It is preferable to use a product which is produced by coating the conductive foil on a conductive foil and winding the conductive foil. Further, it is desirable to form an electrically insulating film on the end face of the thin coil in order to secure the insulation.

In the above coil unit, in particular, the step of forming the end face of the thin strip coil in conformity with the shape of the mounting surface of the flexible wiring board and the thin strip coil in the state where the end face is brought into contact with the surface of the flexible wiring substrate. A step of attaching to the flexible wiring board, an inner peripheral surface and an outer peripheral surface of the ribbon coil,
Being manufactured by a step of conductively connecting with a conductive connecting material between the exposed portion for connection of the power supply wiring layer arranged directly below or inside the inner peripheral surface and directly below or outside the outer peripheral surface. Is preferred.

In this case, in the conductive connection step, a step of applying a conductive heating fluid material such as cream solder to the inner peripheral surface and the outer peripheral surface of the ribbon coil and heating fluidity by heating. It is desirable to fluidize the material to electrically conductively connect the inner peripheral surface and the outer peripheral surface of the thin coil to the exposed connection portion. The inner and outer peripheral surfaces of the thin coil may be electrically connected to the exposed connection portion by applying or dropping a conductive paste. In this way, the connection process can be automated, and since reliable conductive connection can be made, connection failure, disconnection accident, etc. can be prevented.

In the step of forming the end face of the thin strip coil in conformity with the shape of the mounting surface of the flexible wiring board, it is preferable to perform press molding using a molding die formed substantially the same as the mounting surface. However, when the thin strip coil is cut out, it is possible to cut the wound body of the conductive film in accordance with the shape of the mounting surface. In the step of attaching the thin strip coil to the flexible wiring substrate, it is preferable that the flexible substrate is extended to the surface of the holder formed to have substantially the same shape as the mounting surface and the thin strip coil formed in this state is bonded in this state. In this case, the end face of the thin strip coil is formed by pressing the thin strip coil whose end face is not formed and the flexible wiring board on the holder in contact with each other with an adhesive, by the above-mentioned forming die. It is also possible to simultaneously perform the step of attaching and the step of attaching the thin strip coil to the flexible wiring board.

[0017]

Embodiments of the coil unit according to the present invention will now 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 strip-shaped polyimide resin, and on the flexible wiring board FPC. It also has a pair of focusing drive coils 31 and 31 and a pair of tracking drive coils 32 and 32 that are similarly fixed. In the flexible wiring board FPC, as shown in FIG. 2, the wiring pattern 2 is formed by printing on the base 1, and the resist 3 covers the wiring pattern 2.

In the center of the flexible wiring board FPC,
The terminal portion 1a formed in the narrow width shown in FIG. 1 is formed, and the end portion of the wiring pattern 2 is centrally arranged therein, and the input pad 20 not covered with the resist 3 is formed. The other end of the wiring pattern 2 is arranged inside and outside the focus drive coil 31 and the tracking drive coil 32, respectively, and is not covered with the resist 3 for the connection pad 2.
1, 22 are formed.

The focusing drive coil 31 and the tracking drive coil 32 are thin strip coils formed by winding a conductive metal foil such as copper foil. This ribbon coil is manufactured as follows. A resin insulating layer and a resin adhesive layer are coated on one surface or both surfaces of the metal foil, and the metal foil is wound around a winding jig to form a rod-shaped wound body. This winding body is completely adhered and solidified by heating or ultraviolet curing the resin adhesive layer in the firing process, and then the winding jig is removed and the winding body is sliced with a wire saw or the like to form 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 end).

In the 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. In particular, a semi-curable insulating material having an adhesive function, for example, an epoxy resin, a rubber-modified epoxy resin, and an imidazole is mixed (the compounding ratio is, for example, 70:30:45 or 5 in order of weight ratio).
It is 0:50:40, particularly preferably 70:30:45. When a 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 4 to 5 μm and the thickness of the resin layer is suppressed to about 1 to 2 μm. It is possible to obtain a high space factor of 80% or more while ensuring the above.

In this case, as the manufacturing process, a step of coating the metal foil with the above resin,
A step of pre-baking at about 150 ° C. to semi-cure the resin, a step of forming a wound body by winding around a winding jig, a step of main baking the wound body at 120 to 200 ° C., and a wound body Is provided. PA on one side of the metal foil
An insulating layer is formed by forming a high-density insulating layer of I (polyamideimide) resin with a thickness of about 1 μm, and coating one side or the other side of the metal foil with the semi-curable resin with a thickness of about 1 μm. Also, it is possible to prevent the insulation failure due to the occurrence of pinholes and the like while suppressing the thickness of the adhesive layer. However, in this case, it goes without saying that another adhesive 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 above semi-curable resin, a thermoplastic resin such as nylon-based, polyolefin-based, or ester-imide may be used, and a method of hardening the wound body by curing may be adopted.

The focus drive coil 31 and the tracking drive coil 32 are formed and attached as follows. On one or both end surfaces of the thin strip coil (slice width, that is, the thickness of the thin strip coil is about 0.2 mm) formed as described above, an electric resin made of epoxy resin or phenol resin shown in FIG. 2 is formed. The insulating film 35 is formed. Next, the ribbon coil is press-molded using a die formed in conformity with the shape of the ribbon coil. This molding step is performed, for example, when the mounting surfaces of the focus drive coil 31 and the tracking drive coil 32 are curved surfaces.
Molding is performed so that the end surface of the thin coil on which the electrical insulating coating is applied has a similar curved surface.

In this case, when slicing the wound body, it is also possible to cut it so that the end surface has the same shape as the mounting surface. For example, in the case of cutting with a multi-wire saw, the winding base is supported, and the moving direction of the support base that is attached so that the winding body is gradually pressed against the wire moves toward the wire. In addition to the above, the cut surface (the end surface of the ribbon coil) can be cut into a cylindrical shape by moving the wound body obliquely forward and backward in the axial direction.

Finally, the insulating film on the surface of the winding end existing on the inner peripheral surface and the outer peripheral surface of the thin coil is made to correspond to the positions of the connection pads 21 and 22 formed on the surface of the flexible wiring board FPC. By removing by a physical treatment such as polishing or a chemical treatment such as etching, the tracking drive coil 32 having the connection surface portions 32a and 32b shown in FIG. 2 is formed. The process for the focus drive coil 31 is similar.

The focus drive coil 31 and the tracking drive coil 32 formed in this manner correspond to the positions of the connection pads 21 and 22 and are electrically insulating.
The end face formed with 5 (the end face formed into a shape matching the mounting surface) is attached to the surface of the above-mentioned flexible wiring board FPC with an adhesive or the like. 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 wiring board FPC.
Is prepared, the flexible wiring board FPC is temporarily attached to the surface of the holder H with an adhesive or the like, and the end faces of the drive coils 31 and 32 are attached to the temporarily attached substrate surface. The substrate FPC and the drive coil can be securely fixed to each other. It is also possible to form the thin coil at the same time as mounting on the flexible wiring board. That is, an adhesive is applied to the end face of the thin coil, and the end face to which the adhesive is applied is housed in the forming die M so that the forming die M is temporarily attached to the holder H on the flexible wiring board FPC. By pressing against, the ribbon coil is pressed and adhered to the flexible wiring board, and at the same time, the ribbon coil is sandwiched between the molding die M and the surface of the flexible wiring board to be molded into a desired shape.

The connection surface portions 32a and 32b of the focus drive coil 31 and the tracking drive coil 32 fixed on the flexible wiring board FPC are connected to the connection pad 2
1, 22 so that the connection pad 22 is located directly above or below the edge of the connection surface 32a, as shown in FIG. 2 or FIG.
They are arranged so that the connection pads 22 are located immediately below or outside b. Then, for example, in the tracking drive coil 32, the connection surface portions 32a, 32b and the connection pads 22, 22 are conductively connected by the solders 33, 34. In this connection method, for example, as shown in FIG. 4A, cream solder is supplied to and adhered to the connection surface portion 32b from a nozzle having an outlet facing the connection surface portion 32b. As shown in (b), the cream solder is melted by the reflow process and allowed to flow down onto the connection pad 22, so that the connection surface portion 32b and the connection pad 22 are naturally connected. Here, a conductive paste such as silver wax can also be used as the connecting material. In this case, the conductive paste is applied between the connection surface portions 32a and 32b and the connection pads 22 and 22, or the nozzle N.
Dripped from.

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

FIG. 5 is a schematic plan view showing a state in which 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 pivotally supported by the support shaft 45.
6 is attached so as to be movable in the axial direction of the support shaft 45 and rotatable about the axis. The movable unit 46 includes a holding frame 47, and an objective lens 48 is housed in the holding frame 47. On the inner peripheral surface of the outer yoke plate 43, a pair of focusing magnets 49, 49 facing each other and a pair of similar tracking magnets 50, 50 are fixed. The coil unit CU is a movable unit 46.
Focusing drive coil 3 is attached to the outer peripheral surface of the
1, 31 are arranged so as to face the focusing magnets 49, 49, and the tracking drive coils 32, 32 are arranged so as to face the tracking magnets 50, 50, respectively.

When mounted on the optical pickup device shown in FIG. 5, since the coil unit CU is bonded and fixed in a curved state in conformity with the outer peripheral surface of the movable unit 46, the focus drive coils 31 and 31 and the tracking drive coil. The stress due to the deformation of the substrate may be applied to the connecting portions of the coils 32, 32, which may cause disconnection of the connecting portions or peeling of the coils. Therefore, as described above, when the coil is manufactured, the end face on the fixed side of the thin strip coil is formed into a circumferential surface that matches the curvature of the outer peripheral surface of the movable unit 46, so that the disconnection due to the attachment to the movable unit 46 is caused. And peeling can be prevented.

As described above, the thin strip coil formed in the shape adapted to the movable unit 46 is the flexible wiring board C.
Although it is adhered to U, the flexible wiring board bends according to the curvature of the end surface of the thin strip coil due to its flexibility as shown in FIG. 6, so that no adhesion failure occurs between the coil and the board. In addition, since the flexible wiring board itself is also bent according to the deformation of the ribbon coil in this manner, the sticking work becomes easy especially when the flexible wiring board is stuck on a curved surface.

As described above, in this embodiment, since the ribbon coil is fixed on the flexible substrate, the ribbon coil can be easily attached and the wiring can be connected, and the coil unit can be made thin. And high magnetic properties can be achieved at the same time. Also, since the end face of the thin ribbon coil is shaped to match the mounting surface of the flexible board, it is possible to improve the mounting property and to securely mount it on any mounting surface, and to prevent the disconnection of the mounting surface with a small curvature. Accidents such as peeling can be prevented.

By using such a coil unit in the optical pickup device (lens actuator), the complexity at the time of mounting the coil can be avoided and automation can be performed, so that the manufacturing cost can be reduced. Further, based on the thinness of the coil unit and the high magnetic performance, the optical pickup device can be downsized and the sensitivity can be increased, and high-speed operation of the pickup can be realized. By the way, in the case where the coil unit CU including the 0.2 mm-thick ribbon coil of the present embodiment is used in the optical pickup device, when the round coil or the sheet coil having the thickness of about 0.5 mm is used. It is possible to obtain an operating speed of about 1.5 to 1.7 times that of the above.

[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 manufacturing cost can be reduced by facilitating the attachment / connection work of the unit, and at the same time, the thinning of the coil unit and the high magnetic characteristics can be achieved at a high level.

[Brief description of drawings]

FIG. 1 is a plan view and a cross-sectional view showing a structure of an embodiment of a coil unit according to the present invention.

FIG. 2 is an enlarged cross-sectional view showing an enlarged mounting portion of the ribbon coil in the embodiment.

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

FIG. 4 is explanatory views (a) and (b) showing a conductive connection method between a drive coil and a wiring pattern in the same example.

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

6 is a side view showing the 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

Claims (5)

[Claims] 1. A flexible wiring board having a power supply wiring layer, and a thin strip coil formed by winding a conductive film and fixed in a state where one end face of the conductive film is in contact with the substrate surface. A coil unit, wherein the power supply wiring layer is conductively connected to a winding end of the thin strip coil. 2. The exposed portion for connection of the power supply wiring layer is arranged directly below or inside the inner peripheral surface of the thin ribbon coil and directly below or outside the outer peripheral surface of the thin strip coil, and the exposed connection portion is exposed. A coil unit, characterized in that the portion and the inner peripheral surface and the outer peripheral surface of the ribbon coil are conductively connected with a conductive connecting material. 3. The coil unit according to claim 1, wherein the end surface of the ribbon coil is formed in a shape that matches the shape of the mounting surface of the flexible wiring board. 4. The thin strip of the coil unit, wherein the flexible wiring board of the coil unit according to any one of claims 1 to 3 is mounted on a peripheral surface formed around an axis of a movable unit. An optical pickup device, wherein the coil is a coil for driving the movable unit. 5. The optical pickup device according to claim 4, wherein the coil unit is fixed to at least a pair of thin ribbon coils that are diametrically opposed or face each other on the peripheral surface.