JP2004172194A - Optical transmission module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmission module which prevents electromagnetic wave from invading into a device, and also prevents the optical component from being affected by the electromagnetic wave. <P>SOLUTION: The optical transmission module 1 incorporates: an optical component 40 for effecting optical transmission, optical reception or optical transmission and reception for an optical fiber 60; a driving circuit component 30 for driving the optical component 40 based on the light-electric conversion of the optical signal or an electric signal from the optical component 40; a multilayer substrate 20; and a metallic case 10. Ground layers 27a, 27c exposed at the ends of the multilayer substrate 20 are contacted with the peripheral surface of an opening for the metallic case 10, and the opening of the metallic case 10 is electromagnetically shielded by the ground layers, whereby EMC performance is improved. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical transmission module, and more particularly to an optical transmission module that prevents circuit components such as a light emitting element, a light receiving element, and an IC from being affected by external electromagnetic waves.
[0002]
[Prior art]
Conventionally, a means for connecting electronic devices to each other has been a cable. However, in recent years, high-speed and large-capacity transmission has been required, and optical transmission has attracted attention. Signal transmission by cable has drawbacks such as being easily affected by external noise and large transmission loss. On the other hand, optical transmission using an optical fiber has features such as a wide band, a high-speed large-capacity transmission, and a light transmission line. When connecting electronic devices by optical transmission, an optical transmission module that converts an optical signal from an optical fiber into an electrical signal, or converts an electrical signal into an optical signal and outputs the optical signal to the optical fiber is used.
[0003]
The optical transmission module is a reception-only type using a combination of a connector, a light-receiving element, and an electronic circuit, a transmission-only type using a combination of a connector, a light-emitting element, and an electronic circuit, and a transmission / reception using a combination of a connector, a light-emitting element, a light-receiving element, and an electronic circuit. There are types and the like, and they are combined into one unit (optical transmission module). The optical transmission module can be used as an external adapter of a certain device, mounted as a single component on a printed circuit board on which circuit components are mounted in the device, or can be arranged together with the printed circuit board. .
[0004]
The electronic circuit in the optical transmission module is configured using an LSI or the like, and is easily affected by electromagnetic waves from the outside and the inside of the device. When affected by electromagnetic waves, there is a possibility that a transmission signal error or transmission failure may occur. Therefore, in order to secure EMC (Electromagnetic Compatibility) characteristics and transmission characteristics, the optical transmission module is provided with a shield structure. For example, a printed circuit board, and a transmitting and receiving circuit component mounted on the printed circuit board may be covered with a metal shield cover, or may be formed into a box shape by resin molding or the like. A structure has been proposed which covers the upper and lower surfaces of a printed circuit board and a mounted component, for example (see, for example, Patent Document 1).
[0005]
Also, in an optical module having an optical array having a predetermined width and length, ground strips made of a conductive material are provided at predetermined intervals in the length direction, and at least one end of each ground strip is grounded. However, a method of reducing the electromagnetic interference leaked from the opening by the ground strip has also been proposed (for example, see Patent Document 2).
[0006]
[Patent Document 1]
JP-A-11-261273 (Pages 1 to 3, FIGS. 1 and 4)
[0007]
JP-A-2002-223093 (Pages 6 to 9, FIGS. 1 and 2)
[0008]
[Problems to be solved by the invention]
However, according to the conventional optical transmission module, in the case of the configuration disclosed in Japanese Patent Application Laid-Open No. H11-261273, the mounting portion of the optical component becomes an opening for the electromagnetic wave, and the electromagnetic wave penetrates through this opening, so that sufficient EMC performance is obtained. Can not get. In particular, it becomes remarkable when the transmission speed is increased or an optical component in which a large number of optical elements are arrayed is used. In the configuration of Japanese Patent Application Laid-Open No. 2002-223093, a ground strip made of a conductive material is provided in the opening. However, it is technically difficult to provide this ground strip, and it is thought that the cost of the optical array is increased. Can be Further, it is difficult to obtain a sufficient EMC effect because the connection between the ground strip and the surroundings is difficult.
[0009]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical transmission module that prevents electromagnetic waves from entering the inside of a device and prevents optical components from being affected by electromagnetic waves.
[0010]
[Means for Solving the Problems]
The present invention provides an optical transmission module for transmitting or receiving an optical signal through an aperture, in order to achieve the above object,
An optical transmitting and receiving unit that performs at least one of transmission or reception of the optical signal,
A circuit unit electrically connected to the optical transmitting and receiving unit;
A case part having the electromagnetic shielding property to accommodate the optical transmitting and receiving part and the circuit part, provided with the opening,
An optical transmission module, comprising: a substrate unit that electrically connects the optical transmission / reception unit and the circuit unit and a part of a ground layer electromagnetically shields the opening.
[0011]
According to this configuration, since the opening of the case portion is arranged so as to be electromagnetically shielded by a part of the ground layer of the substrate portion, electromagnetic noise intrudes from the outside through the gap in the mounting portion of the optical transceiver. Can be prevented, and a sufficient EMC effect can be obtained.
[0012]
In addition, the case portion is formed of a metal material and accommodates the light emitting surface or the light receiving surface of the light transmitting and receiving portion in the opening, so that the optical transmission member connected to the light transmitting and receiving portion can be attached and detached without impairing the electromagnetic shielding property. Nature can be secured.
[0013]
In addition, the opening has an optical input / output opening for transmitting or receiving an optical signal and an electric signal input / output opening for inputting / outputting an electric signal to / from the circuit portion, so that the opening to the case portion without impairing the electromagnetic shielding property. Removability of the connected device can be secured.
[0014]
Further, the light input / output opening includes a flange formed having a short side and a long side, and a distance from a front end surface to a light emitting surface or a light receiving surface of the light transmitting / receiving unit is equal to or longer than the length of the short side. With such a configuration, it is possible to effectively prevent electromagnetic waves from entering the inside of the opening.
[0015]
In addition, by setting the distance of the flange to be at least 1/3 of the long side, the above-described intrusion of the electromagnetic wave can be more efficiently prevented.
[0016]
Further, the substrate portion is formed of a flexible substrate member having flexibility and a plurality of rigid substrate members mechanically and electrically connected via the flexible substrate member, so that the substrate portion can be accommodated in the case portion. This makes it possible to use the ground layer as a part of the electromagnetic shield without restricting the performance.
[0017]
Further, the optical transmitting and receiving unit may be provided by arranging a plurality of photodiodes, laser diodes, or both.
[0018]
In addition, since the ground layer is formed with a ground pattern corresponding to the shape of the portion that comes into contact with the opening, the opening of the case portion can be shielded by the ground layer.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a cross section of the optical transmission module of the present invention, and FIG. 2 shows the appearance of FIG.
[0020]
The optical transmission module 1 includes a box-shaped metal case 10 having rectangular tubular flanges 10a and 10b at both ends, a multilayer substrate 20 housed therein, and a drive as a circuit unit mounted on the multilayer substrate 20. An optical transmitting and receiving unit that performs optical communication between the circuit component 30 and the connected optical fiber 60 (61 is a connector attached to an end of the optical fiber 60 and is not shown in FIG. 2). And a connector 50 for inputting / outputting an electric signal to / from the drive circuit component 30.
[0021]
The metal case 10 is processed using a metal material having excellent mechanical strength and electrical characteristics. More specifically, a metal material such as copper, copper alloy, iron, and iron alloy, which has an electromagnetic interference shielding property (a property that can be shielded or reduced) with respect to an electromagnetic wave and has conductivity, is sufficiently shielded from the electromagnetic wave. Or it is processed to a reduced thickness. It is desirable that the metal case 10 has a hermetically sealed structure at the joint surface and the like except for the connection port of the optical fiber and the connector so that electromagnetic waves do not enter the case from the outside. Further, the metal case 10 is configured with a combination such as a lid and a main body or an upper main body and a lower main body in consideration of workability at the time of housing the built-in components, workability at the time of replacement and inspection, and the like. Parts are fixed by screws or the like.
[0022]
The multilayer substrate 20 is formed of a sheet-shaped flexible substrate 21 made of an insulating resin such as polyimide, a wiring layer 22 formed of copper foil on one surface of the flexible substrate 21, and formed of copper foil on another surface. A ground layer 23, three glass epoxy substrates 24 a, 24 b, 24 c (printed substrates), which are rigid substrates integrally provided via a flexible portion A and a flexible portion B as substrate portions, and provided on the ground layer 23. Three glass epoxy substrates 25a, 25b, and 25c, which are rigid substrates, wiring layers 26a, 26b, and 26c made of copper foil provided on the glass epoxy substrates 24a, 24b, and 24c, and on the glass epoxy substrates 25a, 25b, and 25c. , Ground layers 27a, 27b, 27c, and ground layers 27a, 27b, 27c With 3 and a through hole 28 for electrically connecting the.
[0023]
The optical component 40 includes a light emitting element such as a laser diode and a light receiving element such as a photodiode, and is provided in a number corresponding to the number of the optical fibers 60.
[0024]
FIG. 3 shows the multilayer board 20 in an unfolded state before being assembled to the metal case 10.
[0025]
FIG. 3A shows a cross section of the multilayer substrate 20. The multilayer substrate 20 has a length and a width that can be accommodated in the metal case 10 when bent by the flexible portion A and the flexible portion B. It is folded at the two places shown in. No rigid members are mounted on both sides of the flexible part A and the flexible part B in order to enable bending. The surface of the copper foil is preferably plated with gold or the like to avoid corrosion and the like.
[0026]
FIG. 3B shows the bottom surface of the multilayer board 20. The ground layers 27a and 27c are formed in the shape of a square, and the illustration of the ground layer 27a and the glass epoxy board 25a is omitted. However, through holes for connecting the terminals of the optical component 40 and the wiring pattern of the wiring layer 22 are provided. Similarly, although illustration is omitted in the portion of the glass epoxy substrate 25c in the portion of the ground layer 27c, a plurality of portions between the wiring pattern of the wiring layer 22 and the number of terminals of the connector 50 and the terminal position are omitted. Through holes are provided. Further, as shown in FIG. 1, a nut member 70 is attached to the ground layer 27b by soldering or the like, so that the nut member 70 can be screwed and fixed from outside the metal case 10.
[0027]
In FIG. 3A, when the flexible portion A is bent 90 ° in the direction of the arrow, it becomes the position shown by the dotted line. Similarly, the flexible portion B can be bent upward by 90 °. As shown in FIG. In the following description, the left side of the flexible portion A in FIG. 3 is referred to as a first rigid portion, the portion between the flexible portions A and B is referred to as a second rigid portion, and the right side of the flexible portion B is referred to as a third rigid portion.
[0028]
4 and 5 show a state in which the multilayer substrate 20 on which the drive circuit component 30, the optical component 40, and the connector 50 are mounted is bent into a U-shape or a U-shape.
[0029]
The optical component 40 is mounted on the first rigid portion, the drive circuit component 30 is mounted on the second rigid portion, and the connector 50 is mounted on the third rigid portion. A plurality of drive circuit components 30 are mounted at predetermined positions on the wiring layer 26b of the second rigid portion, and each terminal thereof is soldered to a wiring pattern (not shown) of the wiring layer 26b.
[0030]
An optical component 40 is mounted at a predetermined position on the glass epoxy board 25a in the first rigid portion, and each terminal of the optical component 40 penetrates the glass epoxy board 25a and the flexible board 21 (further, the wiring layer 26a has ), And is connected to a wiring pattern on the wiring layer 22 or the wiring layer 26a (or both wiring layers). The ground terminal of the optical component 40 is connected to the ground layer 23 or to one of the ground patterns of the wiring layers 26c and 22.
[0031]
Further, in the third rigid portion, pins 51 constituting the connector 50 are erected at predetermined positions on the glass epoxy board 24c, the flexible board 21 and the glass epoxy board 25c, and the wiring layers 26c or 22 are passed through the through holes. It is connected to the. However, the ground terminal of the pin 51 is connected to the ground layer 23 or to the ground pattern of the wiring layer 26c or 22. Further, the nut member 70 is soldered to a predetermined position of the ground layer 27b of the second rigid portion.
[0032]
The multilayer board 20 assembled as described above is housed in the metal case 10 as shown in FIG. As shown in FIGS. 4 and 5, the multilayer substrate 20 is placed in the metal case 10 while the first and third rigid portions are bent vertically to form a U-shape. The optical component 40 of the first rigid part is housed in the flange 10a, and the connector 50 of the third rigid part is housed in the flange 10b. Next, the entire surface of the ground layer 27a is soldered to the base of the flange 10a. Alternatively, a configuration in which the first rigid portion is pressed against the base of the flange 10a by a pressing member or a configuration in which the first rigid portion is screwed may be used. Similarly, the entire surface of the ground layer 27c of the third rigid portion is soldered to the root of the flange 10b, and connected by means such as pressing with a pressing member or screwing. Next, the multi-layer board 20 is fixed by screwing the nut member 70 of the second rigid portion with a screw (not shown).
[0033]
As described above, since the optical component 40 is mounted on the ground plane connected to the metal case 10 by 360 °, a stable ground potential can be secured. Will be possible. In addition, since the heat generated by the drive circuit component 30 is transferred to the metal case 10, the optical component 40 is less likely to be affected by the heat generated by the drive circuit component 30. In particular, a structure in which the drive circuit component 30 and the optical component 40 are separated by the ground layer 23 (the drive circuit component 30 and the optical component 40 are arranged on both surfaces of the multilayer substrate 20) is effective. In addition, there is a concern that the optical component 40 is affected by external noise. However, in the present invention, since the flange 10a is provided, the external noise is shielded, and electromagnetic noise can be reduced. The effect of providing the flange 10a can be considered in the same manner as general waveguide attenuation. When the height (short side) is h and the width (long side) is d (d> h), the effect of the flange 10a is Satisfactory results (approximately 10 dB or more) can be obtained if the distance L from the tip to the optical component 40 is not less than the short side h, specifically, not less than 1/3 of d.
[0034]
Further, by arranging the connector 50 in the opening through the flange 10b in the metal case 10, it becomes possible to use a surface mount type connector, and it is possible to reduce the size of the optical transmission module, improve mass productivity, reduce noise, and the like. Become.
[0035]
FIG. 6 shows a state where the optical transmission module 1 according to the present invention is mounted on a printed circuit board 80 of an electronic device.
[0036]
A ground pattern (not shown) for mounting the light transmission module 1 is formed on the printed circuit board 80, and the light transmission module 1 is fixed to this ground pattern by a fixing method such as soldering or screwing. . Further, an electronic circuit section 81 including ICs 82 and 83, a capacitor 84, a resistor 85, a transistor 86, and the like is mounted on the printed board 80. A connector 87 connected to an interface (not shown) of the electronic circuit unit 81 is mounted on the printed circuit board 80. For example, a flat cable 88 is connected to the connector 87, and an end of the connector 87 is connected to the connector 87. Is connected to the connector 50, and the optical transmission module 1 and the electronic circuit section 81 are connected.
[0037]
The electric signal transmitted from the electronic circuit section 81 to the optical fiber 60 is converted into a signal for driving the optical component 40 in the drive circuit component 30 of the optical transmission module 1. Here, when the transmission-side optical component 40 is a laser diode and the reception-side optical component 40 is a photodiode, the laser diode emits a laser beam to the optical fiber 60 by performing electro-optical conversion of the above-described signal. On the other hand, the laser light incident from the optical fiber 60 is received by the photodiode, photoelectrically converted, converted into a signal format accepted by the electronic circuit unit 81 by the drive circuit component 30, and transmitted to the electronic circuit unit 81 via the flat cable 88. Sent.
[0038]
In the above embodiment, the multi-layer substrate 20 is fixed by the nut member 70 and the screw. For example, a double-sided adhesive tape is attached to the entire surface of the ground layer 27b, and the double-sided adhesive tape is used to attach the bottom surface of the metal case 10 to the bottom surface. You may make it stick. Alternatively, a plurality of holes may be formed in the bottom surface of the metal case 10 and soldered to the ground layer 27b. Further, if the connection between the ground layers 27a and 27c of the first and third rigid portions and the metal case 10 is guaranteed, the connection between the ground layer 27b and the metal case 10 may be omitted.
[0039]
Further, in the above embodiment, the metal case is used because the mechanical strength, the conductivity and the electromagnetic interference shielding properties are easily obtained, but a conductive layer such as a copper foil is adhered to the entire inner surface of the resin case. Or, even if it is a conductive case in which a metal film is deposited, it is not limited to metal as long as necessary mechanical strength, conductivity and electromagnetic interference shielding characteristics can be secured.
[0040]
Further, in the above-described embodiment, the connector 50 is provided and connected to the mounting printed board or another electronic device. However, the connector 50 is not necessarily required, and an optical transmission module with a cable may be used. For example, if the core wire at the end of the cable is directly connected to the wiring layers 22 and 26c by soldering, the connector 50 is not required, and the flange 10b can also be a small opening having a size matching the outer shape of the cable. it can.
[0041]
Further, in the present invention, the multilayer substrate 20 is bent in a U-shape (or U-shape). However, in the case of an optical transmission module having no connector, the multilayer substrate 20 is bent in an L-shape. It is stored in the metal case 10 in the state.
[0042]
【The invention's effect】
As is clear from the above, according to the optical transmission module of the present invention, since the opening of the optical transmitting / receiving section is electromagnetically shielded by the substrate on which the optical component and the circuit component are mounted, the mounting section of the optical transmitting / receiving section is provided. Can be prevented from entering the inside of the device through the gap, and a sufficient EMC effect can be obtained. Furthermore, noise can be reduced by arranging the optical transmitting / receiving unit and the circuit components separately from each other with respect to the ground layer.
[Brief description of the drawings]
FIG. 1 is a sectional view of an optical transmission module according to the present invention.
FIG. 2 is a perspective view showing the appearance of FIG.
3A and 3B show a configuration of a multilayer substrate in an unfolded state before being assembled to the metal case of FIG. 1, wherein FIG. 3A is a sectional view and FIG. 3B is a bottom view.
FIG. 4 is a perspective view showing a multilayer substrate on which a drive circuit component, an optical component, and a connector have been mounted.
FIG. 5 is a cross-sectional view showing a multilayer substrate on which a drive circuit component, an optical component, and a connector have been mounted.
FIG. 6 is a front view showing a state where the optical transmission module according to the present invention is mounted on a printed circuit board of an electronic device.
[Explanation of symbols]
1 Optical transmission module 10 Metal case 10a, 10b Flange 20 Multilayer substrate 21 Flexible substrate 22 Wiring layer 23 Ground layers 24a, 24b, 24c Glass epoxy substrates 25a, 25b, 25c Glass epoxy substrates 26a, 26b, 26c Wiring layers 27a, 27b, 27c Ground layers 28, 29 Through hole 30 Drive circuit component 40 Optical component 50 Connector 51 Pin 60 Optical fiber 61 Connector 70 Nut member 80 Printed circuit board 81 Electronic circuit sections 82, 83 IC
84 capacitor 85 resistor 86 transistor 87 connector 88 flat cable 89 connector

Claims (8)

In an optical transmission module that transmits or receives an optical signal through an aperture,
An optical transmitting and receiving unit that performs at least one of transmission or reception of the optical signal,
A circuit unit electrically connected to the optical transmitting and receiving unit;
A case part having the electromagnetic shielding property to accommodate the optical transmitting and receiving part and the circuit part, provided with the opening,
An optical transmission module, comprising: a substrate unit that electrically connects the optical transmission / reception unit and the circuit unit and a part of a ground layer electromagnetically shields the opening. The optical transmission module according to claim 1, wherein the case portion is formed of a metal material, and accommodates a light emitting surface or a light receiving surface of the light transmitting and receiving unit in the opening. The aperture is an optical input / output aperture for transmitting or receiving the optical signal,
The optical transmission module according to claim 1, further comprising an electric signal input / output opening for inputting / outputting an electric signal to / from the circuit unit. The light input / output opening includes a flange formed having a short side and a long side, and a distance from a tip surface to the light emitting surface or the light receiving surface of the light transmitting / receiving unit is equal to the length of the short side. The optical transmission module according to claim 3, wherein: The optical transmission module according to claim 4, wherein the flange has the distance that is equal to or more than １ ／ of the long side. 7. The device according to claim 6, wherein the substrate portion includes a flexible substrate member having flexibility and a plurality of rigid substrate members mechanically and electrically connected via the flexible substrate member. An optical transmission module as described in the above. The optical transmission module according to claim 1, wherein the optical transmission / reception unit includes a plurality of photodiodes, laser diodes, or both. The optical transmission module according to claim 1, wherein the ground layer is formed with a ground pattern corresponding to a shape of a portion that contacts the opening.

Images