JP4692272B2 - Laser integrated device and optical pickup device - Google Patents

Description

  The present invention relates to a laser integrated device that generates laser light, an optical pickup device that can read a signal of an optical recording medium, and a method of manufacturing the laser integrated device.

  Conventionally, for example, an optical pickup device for recording a signal on an optical disc such as a CD (Compact Disc) or a DVD (Digital Versatile Disk) or reproducing the recorded signal includes a semiconductor integrated device including a semiconductor laser, An optical component such as an objective lens is mounted (see, for example, Patent Document 1).

In the semiconductor integrated device of Patent Document 1, a semiconductor laser (7) is mounted on a base body (3) made of ceramics via a semiconductor substrate (5) and a submount (6). Further, a prism (10) for raising the laser beam emitted from the semiconductor laser (7) substantially vertically is placed on the semiconductor substrate (5). Generally, such a semiconductor integrated device is electrically connected to an external driver IC (Integrated Circuit) through a flexible printed wiring board. Therefore, the semiconductor integrated device includes an electrode for making electrical contact with the flexible printed wiring board on the back surface side of the base body (3).
Japanese Patent Laying-Open No. 2004-220675 (FIG. 3)

  If the area of the ground electrode is small among the electrodes, there is a problem that noise increases. Also, when the conductive wire of the flexible printed wiring board is elongated, another unnecessary noise is picked up by the antenna effect. Conventionally, for example, the influence of noise has been reduced by making the conductive wire of the flexible printed wiring board thick, but the size of the flexible printed wiring board has a limit, and noise reduction cannot be expected so much.

  In view of the circumstances as described above, an object of the present invention is to provide a laser integrated device optical pickup device and a method for manufacturing the laser integrated device that can reduce noise of an electric signal.

  In order to achieve the above object, a laser integrated device according to the present invention comprises a substrate having a surface, a conductor film formed on the surface, a laser generating element mounted on the conductor film, and the surface. And a ground electrode used when the laser generating element is driven.

  In the present invention, since the ground electrode is formed on the surface on which the laser generating element is mounted, the surface area of the ground electrode can be increased as much as possible compared to the case where it is formed on the back surface of the substrate. Thereby, noise can be reduced.

  In the present invention, the laser integrated device further includes a signal electrode formed on the back surface of the substrate and used when the laser integrated element is driven, and the surface area of the ground electrode is greater than the surface area of the signal electrode. large. Thereby, noise is further reduced. In the present invention, both the meaning that the surface area of one ground electrode is larger than the surface area of one signal electrode, or that the surface area of one ground electrode is larger than the total surface area when there are a plurality of signal electrodes. Is included.

  In the present invention, the laser integrated device is a device mounted on a base frame of an optical pickup device including an optical system that guides laser light generated by the laser generating element to an optical recording medium, and the surface of the substrate is It is a reference surface for making contact with the base frame. In other words, since the ground electrode is formed on the reference surface, the ground electrode is in contact with the base frame itself or the ground conducting portion of the base frame, and the base electrode is reliably conducted to the extent that the ground electrode is formed larger. Can do. When the ground electrode contacts the base frame itself, the base frame is made of a conductive material.

  Furthermore, it is advantageous if the conductor film and the ground terminal have substantially the same thickness. For example, when the optical axis of the laser beam from the laser generating element extends in the film thickness direction of the conductor film and the ground electrode, the optical path length of the laser beam when the ground electrode comes into contact with the base frame (or the conductive portion of the base frame) Alternatively, the focal length of the optical system can be set to a desired value. In other words, when the optical pickup is manufactured, the ground electrode formed on the reference surface is simply brought into contact with the base frame, and positioning with respect to the focal length can be easily performed.

  In this case, the conductor film is a film including a tungsten film, a nickel film, and a gold film. In particular, the variation in the thickness of the tungsten film or nickel film is relatively large. Therefore, when there is no ground electrode on the substrate surface and only the conductor film is present, the variation in the optical path length or the focal length also becomes large. However, if a ground electrode is formed on the substrate surface, the optical path length or focal length can be adjusted with high accuracy as described above.

  The ground terminal is made of the same material as that of the conductor film, but is not necessarily the same. If the same material is used, the laser integrated device can be easily manufactured.

  An optical pickup device according to the present invention includes a substrate having a surface, a conductor film formed on the surface, a laser generating element mounted on the conductor film, and formed on the surface, and the laser generating element is driven A laser integrated element having a ground electrode to be used, an optical system for guiding a laser beam generated by the laser generating element to an optical recording medium, and a conductive portion to which the ground electrode is electrically connected. And a base frame on which the laser integrated element and the optical system are mounted.

  A method for manufacturing a laser integrated device according to the present invention is a method for manufacturing a laser integrated device comprising a substrate having a surface and a laser generating element provided on the substrate, wherein the laser generating element is mounted on the surface. A step of forming a conductor film in a region to be placed, and a step of forming on the surface a ground electrode used when the laser generating element is driven. In the present invention, the step of forming the conductor film and the step of forming the ground electrode may be performed in the same step (at the same time) or may be performed in different steps (at different times).

  As described above, according to the present invention, it is possible to reduce noise of electric signals generated in the laser integrated device.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic perspective view showing an optical pickup device according to an embodiment of the present invention. FIG. 2 is a schematic plan view showing a part of the optical pickup device 30 of FIG.

  The optical pickup device 30 includes a base frame 22 that moves in the radial direction of an optical disc 200 as an optical recording medium. The movement of the base frame 22 in the radial direction is performed by a so-called thread motor or a motor called a feed motor. The base frame 22 is made of a conductor, for example. The laser integrated element 1 is mounted on the side surface 22a of the base frame 22, and the objective lens 23 is mounted. The base frame 22 is also equipped with a biaxial actuator (not shown) for moving the objective lens 23 in the tracking direction (Y direction) and the focusing direction (Z direction) of the optical disc 200. In addition to the objective lens 23, the base frame 22 is also equipped with an optical system that guides the laser light generated from the laser integrated element 1 to the signal recording surface of the optical disc 200. The “optical system” here includes, in addition to the objective lens 23, for example, a mirror (not shown) that raises the laser light emitted from the laser integrated element 1 in the X direction almost perpendicularly to the objective lens Z direction. As shown in FIG. 2, a hole or notch 22 b for holding the laser integrated device 1 by inserting the case 17 of the laser integrated device 1 or the like is formed in the side surface 22 a of the base frame 22.

  Even if the actuator is not a biaxial actuator, a triaxial actuator including a tilt actuator that tilts the objective lens 23 with respect to the signal recording surface of the optical disc 200 in the ZY plane or the ZX plane may be mounted. is there.

  FIG. 3 is a perspective view showing a state in which a flexible printed wiring board (hereinafter referred to as FPC (Flexible Printed Circuit board)) 24 is connected to the laser integrated element 1. A conductive wire 25 is printed on the FPC 24, and one end 24a of the FPC 24 is connected to an electrode provided on the base substrate 3 of the laser integrated element 1 described later. The other end 24b of the FPC 24 is connected to an integrated circuit (not shown) that drives the laser integrated element 1 and inputs a reproduction signal from a photodetector (described later) mounted on the laser integrated element 1, for example.

  FIG. 4 is a perspective view showing the laser integrated device 1. FIG. 5 is a cross-sectional view of the laser integrated device 1 as seen in the XY plane.

  The laser integrated element 1 is configured by disposing predetermined parts on a package 2. The package 2 includes a base substrate 3 formed in a flat plate shape by, for example, a ceramic material, and the above-described case 17 formed by, for example, a resin material. For example, as shown in FIG. 5, the case 17 includes a housing 4 for housing other components such as a semiconductor laser 7 constituting a part or all of the laser generating element, and various optical units provided on the housing. And a block 13 on which components are mounted. The base substrate 3 is, for example, a multilayer wiring substrate, but may not be a multilayer wiring substrate.

  The housing 4 is formed, for example, in a box shape opened downward with a highly heat-insulating resin material, and a transmission hole 4b is formed on the upper surface 4a. A semiconductor substrate 5 is mounted on a surface 3 a that is a reference plane A of the base substrate 3 in the housing 4 via a conductor film 21. A submount 6 is placed on the semiconductor substrate 5, and a semiconductor laser 7 is disposed on the submount 6. Laser light is emitted from the semiconductor laser 7. This laser light is emitted in the direction (Y direction) toward the prism 10 disposed on the semiconductor substrate 5 and next to the semiconductor laser 7.

  For example, the semiconductor laser 7 emits a laser beam having a first wavelength and a laser beam having a second wavelength shorter than the first wavelength. The first wavelength is red laser light of, for example, about 650 to 780 nm, and the second wavelength is blue laser light of, for example, about 405 nm. However, the semiconductor laser 7 may be a semiconductor laser that emits only one of the first and second wavelengths. Alternatively, the semiconductor laser 7 may emit laser light having a wavelength shorter or longer than 405 nm, or may emit laser light having a wavelength longer than 780 nm. Alternatively, it may be a semiconductor laser that emits laser light having a wavelength other than visible light, for example, a wavelength longer than the visible light wavelength or shorter than the visible light wavelength.

  The prism 10 is attached to the semiconductor substrate 5 with, for example, an adhesive. The prism 10 is arranged so as to cover a monitor light receiving element (not shown) having an APC (Automatic Power Controller) function for controlling the light amount of laser light emitted from the semiconductor laser 7 to be constant, for example. The prism 10 is formed with a light reflecting surface 10a formed with an inclination of about 45 degrees and a substantially vertical light transmitting surface 10b. The laser light emitted from the semiconductor laser 7 is reflected by being bent by about 90 degrees on the light reflecting surface 10 a, and the reflected laser light is directed to the optical disc 200. Part of the laser light from the semiconductor laser 7 is transmitted through the light transmission surface 10b, and the transmitted laser light is directed to the monitoring light receiving element.

  On the semiconductor substrate 5, a photodetector (not shown) that receives the return light reflected from the optical disk and converts it into an electrical signal is further mounted.

  The block 13 provided on the upper surface 4a of the housing 4 is formed of, for example, a transparent resin material, the grating 14 is disposed at the center of the lower end, and the quarter wavelength plate 15 is disposed at the center of the upper end. Has been. Further, a hologram 16 is arranged on the block 13 at a predetermined interval below the quarter wavelength plate 15. The hologram 16 is an element having an optical path changing function for changing the optical path of the laser light and an optical splitting function for splitting the laser light.

  FIG. 6 is a plan view showing the back surface 3 b of the base substrate 3. On the back surface 3b of the base substrate 3, as described above, the electrodes 18 and 19 are provided for electrical connection with the electrode (not shown) of the FPC 24. For example, the electrode 18 disposed substantially at the center in FIG. 5 is a ground electrode, and the plurality of electrodes 19 disposed around the ground electrode 18 are signal electrodes. The arrangement of the ground electrode 18 and the signal electrode 19 on the back surface 3b of the base substrate 3 is not limited to the arrangement shown in FIG. The conductor film 21 between the base substrate 3 and the semiconductor substrate 5 is electrically connected to the ground electrode 18 on the back surface 3b through the base substrate 3, for example. The bonding wire 20 extending from the semiconductor substrate 5 or the like is connected to, for example, a terminal 9 provided on the base substrate 3, and the terminal 9 is electrically connected to the signal electrode 19 or the like on the back surface 3 b through the base substrate 3.

  As shown in FIGS. 4 and 5, ground electrodes 26 a and 26 b are formed on the surface 3 a of the base substrate 3 outside the case 17. The ground electrodes 26a and 26b are disposed on both sides of the case 17, for example, and are electrically connected to the ground electrodes 26a and 26b on the back surface 3b.

  Thus, by forming the ground electrodes 26a and 26b on the surface 3a of the base substrate 3, the surface area of the ground electrode 26a or the ground electrode 26b is made as large as possible as compared with the case where it is formed on the back surface of the base substrate 3 or the like. be able to. Thereby, the noise of a signal can be reduced. In particular, in the present embodiment, the surface area of the ground electrode 26 a or the ground electrode 26 b is formed larger than the surface area of the signal electrode 19.

  Further, for example, as shown in FIG. 7, the laser integrated element 1 is inserted from the hole or notch 22a of the base frame 22, and the side surface 22a of the conductor base frame 22 and the ground electrodes 26a and 26b come into contact with each other. That is, since the ground electrodes 26a and 26b are formed larger on the surface 3a which is the reference plane A, the ground electrodes 26a and 26b can be reliably connected to the base frame 22.

  In the case where the base frame 22 is an insulator such as a resin that is not a conductor, the base frame is provided with an electrically conducting portion at a portion where the ground electrodes 26a and 26b are in contact, and the conducting portion is further conducted to another ground. If it is.

  Here, the conductor film 21 is composed of tungsten, nickel, gold or the like in order from the base substrate 3 side to the semiconductor substrate 5 side. Tungsten is formed because tungsten has a high melting point and is difficult to oxidize and is stable. Gold is formed by plating, for example. The reason why the gold plating is formed is that gold has good conductivity and is not easily oxidized. However, since gold has a weak bonding force with tungsten, nickel is interposed as an intermediate layer.

  The ground electrodes 26a and 26b are also made of a multi-layered conductor film made of the same material as the conductor film 21, but this is not always necessary. For example, when the conductor film 21 and the ground electrodes 26a and 26b are formed in the same process by a printing process after the base substrate 3 is covered with a mask (not shown) as described above, the conductor film 21, the ground electrodes 26a and 26b are formed. The materials will be the same.

  Specifically, in the manufacturing process of the conductor film 21 and the like, the variation in the thickness of the tungsten layer is about 8 to 20 μm. Moreover, the variation in the thickness of the nickel layer is about 1 to 9 μm. Gold is flash plating, and the variation is on the order of nanometers and is small. Therefore, variations in the thickness of tungsten or nickel adversely affect the optical path length or focal length of the laser light. That is, if the film thickness varies, the positions of the semiconductor substrate 5, the submount 6, the semiconductor laser 7, etc. in the X direction in FIG.

  As shown in FIG. 8, when the surface 3 a of the base substrate 3 does not have the ground electrodes 26 a and 26 b, the surface 103 a serving as the reference plane A directly contacts the base frame 22, so that the laser integrated device 100 is attached to the base frame 22. Positioned against. However, in this case, the surface 103a of the base substrate 103, which is the reference surface A, and the lower surface of the semiconductor substrate 5 (that is, the upper surface 21a of the conductor film 21) are at different positions (different heights). In this case, the optical path length or focal length of the laser light varies as described above, and the quality of the recording signal to the optical disc 200 or the reproduction signal from the optical disc 200 may be reduced.

  However, in the present embodiment, since the ground electrodes 26a and 26b are formed on the surface 3a of the base substrate 3, the reference plane is in place of the reference plane A, that is, the upper surface B of the ground electrodes 26a and 26b. The position becomes a new reference plane (see FIGS. 5 and 7). Therefore, as shown in FIG. 7, the ground electrodes 26a and 26b are brought into contact with the base frame 22, and the optical path length or focal length of the laser light can be set to an intended value. That is, when the optical pickup device 30 is manufactured, the ground electrodes 26 a and 26 b formed on the reference plane A are simply brought into contact with the base frame 22, and positioning with respect to the focal length can be easily performed. Since the control of the focal length becomes more difficult as the wavelength of the laser light is shorter, the effect is greater as the wavelength of the laser light is shorter. As described above, when the conductor film 21 and the ground electrodes 26a and 26b are formed in the same process, the film thicknesses of the conductor film 21 and the ground electrodes 26a and 26b are almost equal, which is particularly advantageous.

  Conventionally, as shown in FIG. 9, for example, gold plating 105 or the like is applied to the V-shaped groove 103 b of the base substrate 103. When the laser integrated device 100 is in contact with the base frame 22, the gold plating 105 of the V-groove 103b and the base frame 22 are joined by solder, thereby achieving ground conduction. However, in this case, as described above, there are problems that the size of the ground electrode is reduced, noise is increased, and it is difficult to adjust the focal length.

  FIG. 10A shows an eye pattern of a reproduction signal of the optical disc 200 when the ground electrodes 26 a and 26 b are provided on the surface 3 a of the base substrate 3. FIG. 10B shows an eye pattern of a reproduction signal of the optical disc 200 in the case where the ground electrodes 26 a and 26 b are not provided on the surface 3 a of the base substrate 3. The wavelength of the laser beam in this experiment is about 650 nm in red. From these figures, it can be seen that the eye pattern with the ground electrodes 26a and 26b is of higher quality.

  FIG. 11 is a plan view showing a laser integrated device according to another embodiment of the present invention. In the laser integrated device 50, a case 17 similar to the laser integrated device 1 is provided on the surface 3 a of the base substrate 3, and a plurality of ground electrodes 56 are formed on both sides of the case 17. For example, four ground electrodes 56 are formed, but are not limited thereto. Thus, the number and arrangement of the ground electrodes may be any form.

  FIG. 12 is a plan view showing a laser integrated device according to still another embodiment of the present invention. In the laser integrated device 60, the case 17 is disposed so as to be brought closer to one side of the surface 3a of the base substrate 3, and one ground electrode 66 is formed on the surface 3a adjacent to the case. Thus, the ground electrode does not necessarily have to be formed on both sides of the case 17.

  The present invention is not limited to the embodiment described above, and various modifications are possible.

  For example, in the above embodiment, the laser light from the semiconductor laser 7 is reflected by the prism 10, but this is merely an example. Instead of the prism, a configuration in which the light is simply reflected by a mirror may be used.

  The shapes of the base frame 22, the base substrate 3, the case 17, and the like are not limited to the above-described embodiment, and the size and the like are not limited.

1 is a schematic perspective view showing an optical pickup device according to an embodiment of the present invention. FIG. 2 is a schematic plan view showing a part of the optical pickup device in FIG. 1. It is a perspective view which shows the state by which the flexible printed wiring board was connected to the laser integrated element. 1 is a perspective view showing a laser integrated device according to an embodiment of the present invention. It is sectional drawing seen in the XY plane of the laser integrated element. It is a top view which shows the back surface of a base substrate. It is a figure which shows the state which the base frame and the ground electrode contacted. FIG. 5 is a diagram showing a state where a laser integrated element is positioned with respect to a base frame by a surface directly contacting the base frame when there is no ground electrode in the related art. FIG. 10 is a perspective view showing a conventional laser integrated device in which a V-groove of a base substrate is plated with gold. FIG. 10A is a diagram showing an eye pattern of a reproduction signal of an optical disk when a ground electrode is present on the surface of the base substrate, and FIG. 10B is a diagram when no ground electrode is present on the surface of the base substrate. It is a figure which shows the eye pattern of the reproduction signal of an optical disk. It is a top view which shows the laser integrated element which concerns on other embodiment of this invention. It is a top view which shows the laser integrated element which concerns on another embodiment of this invention.

Explanation of symbols

A, B: Reference surface 1, 50, 60 ... Laser integrated element 3 ... Base substrate 3a ... Front surface 3b ... Back surface 3a ... Back surface 5 ... Semiconductor substrate 6 ... Submount 7 ... Semiconductor laser 10 ... Prism 11 ... Case 13 ... Block 14 ... Grating 15 ... Wave plate 16 ... Hologram 17 ... Case 21 ... Conductor film 22 ... Base frame 23 ... Objective lens 26a, 26b, 56, 66 ... Ground electrode 30 ... Optical pickup device 200 ... Optical disk

Claims (5)

A substrate having a surface;
A conductor film formed on the surface;
A laser generating element mounted on the conductor film;
A ground electrode formed on the surface and used when the laser generating element is driven ;
A signal electrode formed on the back surface of the substrate and used when the laser integrated element is driven;
The laser integrated device , wherein the ground electrode has a surface area larger than that of the signal electrode . The laser integrated device according to claim 1,
A laser integrated device in which the conductor film and the ground terminal have substantially the same thickness. The laser integrated device according to claim 2 ,
The conductive film is a film including a tungsten film, a nickel film, and a gold film. A substrate having a surface;
A conductor film formed on the surface;
A laser generating element mounted on the conductor film;
A ground electrode formed on the surface and used when the laser generating element is driven ,
The laser integrated device is a device mounted on a base frame of an optical pickup device including an optical system that guides laser light generated by the laser generating element to an optical recording medium,
The laser integrated device , wherein the surface of the substrate is a reference surface for contacting the frame body . A substrate having a surface; a conductor film formed on the surface; a laser generating element mounted on the conductor film; a ground electrode formed on the surface and used when the laser generating element is driven; A laser integrated device comprising:
An optical system for guiding laser light generated by the laser generating element to an optical recording medium;
An optical pickup device, comprising: a base frame on which the laser integrated element and the optical system are mounted, each having a conducting portion to which the ground electrode is electrically connected.