JP2009010026A - Optical communication module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently reduce the influence of a radiation noise on a frame ground. <P>SOLUTION: This optical transceiver module 2 is provided with: a TOSA (transmitter optical sub-assembly) 4a having a package 8a and a plurality of lead pins 12a, 12b, 12c, 12d including the lead pin 12a electrically connected to the package 8a; a main circuit board 5a having conductive portions 20a, 20b, 20c for electrically connecting the lead pins 12a, 12b, 12c, 12d to an electronic circuit 24 for driving the TOSA and to an SG electrode; and a sub-circuit board 5b having a capacitance component formed between a conductive portion 30 formed on a main surface M3 and a conductive portion 28 formed on a main surface M2, and mounted on the main circuit board 5a so as to be electrically connected in a state where the conductive portion 28 faces the conductive portion 20a of the main circuit board 5a. The lead pin 12a extends toward the main surface M3, thereby being electrically connected to the conductive portion 30. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical communication module that transmits an optical transmission signal via an optical transmission medium.

2. Description of the Related Art Conventionally, there is known a radiation noise reduction device for reducing the influence of radiation noise generated from a cable connected to a printed board on a frame ground (FG) (see Patent Document 1 below). This radiation noise reduction device includes an FG electrode provided on a printed circuit board and connected to a shielded cable, an SG electrode (SG: signal ground), and a capacitor element provided between the FG electrode and the SG electrode. The noise current generated by radiation noise and flowing to the frame ground is shunted to the signal ground.
JP 2003-283177 A

  In general, an optical communication module such as an optical transceiver module operates at a high speed on the order of GHz. Therefore, in order to reduce the influence of the radiation noise on the frame ground (generation of noise current), between the FG electrode and the SG electrode. It is desirable to set the capacitance of the capacitor to be inserted into several pF or more. However, chip-type capacitors used in optical communication modules do not have the above-described capacitance, and it is difficult to develop such capacitors.

  In addition, when connecting the case pin connected to the package (FG) of the optical transceiver module and the printed circuit board, there are cases where the positional relationship between the case pin and the printed circuit board is restricted from the viewpoint of standards and manufacturing efficiency. When the case pin needs to have a certain length due to such a restriction, the case pin has an inductance component, and as a result, a configuration close to an LC series resonance circuit due to the capacitance component between FG and SG and the case pin. May occur. As a result, the capacitance component may not function as a noise filter above a certain frequency.

  Accordingly, the present invention has been made in view of such problems, and an object thereof is to provide an optical communication module that can effectively reduce the influence of radiation noise on the frame ground.

  In order to solve the above-described problems, an optical communication module of the present invention is an optical communication module that transmits an optical transmission signal via an optical transmission medium, and is used for a metal package and a ground electrically connected to the package. An optical transmission module having a plurality of lead pins including a lead pin and generating an optical transmission signal in response to an electric signal applied through the plurality of lead pins, and a circuit unit for driving the optical transmission module and a ground. A main circuit board having a conductive portion for electrically connecting to a potential; a first conductive portion provided on the first main surface; and a second conductive portion provided on the second main surface; A sub-circuit board mounted on the main circuit board so that the second conductive part and the conductive part of the main circuit board are electrically connected to each other. Equipped with ground lee Pins are electrically connected to the first conductive portion by extending toward the first major surface.

  According to such an optical communication module, the ground lead pin of the optical transmission module connected to the FG is connected to the first conductive portion formed on the first main surface of the sub circuit board, and the sub circuit. The sub circuit board is placed on the main circuit board in a state where the second conductive part formed on the second main surface of the board faces and is connected to the conductive part of the main circuit board. As a result, the capacitance component formed by the sub circuit board is connected between the ground lead pin and the conductive portion of the main circuit board, and it becomes easy to secure the capacitance component of the noise filter. Even if the distance between the conductive part of the main circuit board and the ground lead pin is increased due to the arrangement restriction, the length of the ground lead pin itself can be shortened by connecting via the sub circuit board. The inductance of the ground lead pin is reduced, and high frequency noise can be effectively released from FG to SG. As a result, the influence of radiation noise such as crosstalk in the package can be sufficiently suppressed.

  The sub-circuit board is formed by laminating a plurality of insulating layers, and the first and second conductive portions are respectively a plurality of first and second conductive layers formed independently on the plurality of insulating layers. Each of the plurality of first conductive layers and the plurality of second conductive layers are electrically connected to each other, and the first conductive layer and the second conductive layer adjacent to the first conductive layer It is preferable that a capacitive component is formed by disposing an insulating layer therebetween.

  In this case, since the capacitance component is formed by disposing the insulating layer between the plurality of first conductive layers and the plurality of second conductive layers in the sub circuit board, the sub circuit board can be downsized. Capacitance component can be easily increased in capacity, and even if the sub circuit board interposed between the ground lead pin and the main circuit board is small, the influence of radiation noise such as crosstalk in the package can be sufficiently suppressed. In addition, the thickness and area of the sub circuit board can be variously changed, and the degree of freedom in arrangement of the optical transmission module and the main circuit board is increased.

  In addition, it is also preferable that each of the plurality of first conductive layers and the second conductive layers is electrically connected to each other through a through hole penetrating the insulating layer. By adopting such a configuration, even when the thickness of the sub circuit board or the number of stacked layers is changed, the processing when connecting the first conductive layer or the second conductive layer becomes easy.

  According to the optical communication module of the present invention, it is possible to effectively reduce the influence of radiation noise on the frame ground.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of an optical communication module according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a partially broken perspective view showing a configuration of an optical transceiver module 2 according to a preferred embodiment of the present invention. The optical transceiver module 2 is a small optical transceiver including a TOSA 4a (TOSA: Transmitter Optical Sub-Assembly) that is an optical transmission module, a ROSA 4b (ROSA: Receiver Optical Sub-Assembly) that is an optical reception module, a circuit board 5, and a case 6. is there. The TOSA 4 a and the ROSA 4 b are fixed to the side wall 6 a of the case 6, and the circuit board 5 is accommodated in the case 6. The case 6 is made of a metal material and has a role as an FG. The circuit board 5 is formed using an insulating prepreg as a main material, and a circuit pattern is formed on the surface thereof.

  The TOSA 4a is an optical transmission module having a laser diode 7 and a metal package 8a that houses the laser diode 7. The laser diode 7 has an anode terminal and a cathode terminal (not shown), and a laser beam (optical transmission signal) according to a bias current and a modulation current (electric signal) supplied / applied from outside the package 8a. Is generated. The package 8a is a coaxial package made of a metal material, and a flange 16a and a flange 16b are formed on the side surfaces thereof, and a groove 18 is provided between the flange 16a and the flange 16b. The package 8a is electrically insulated from all electric elements (for example, the laser diode 7) included in the TOSA 4a. The laser diode 7 is accommodated in the end 10a of the package 8a, and the laser light emitted from the laser diode 7 is transmitted to the outside from the end 10a through an optical transmission medium such as an optical fiber.

  The TOSA 4a further includes a stem 10a provided at the other end portion 10 of the package 8a and four lead pins 12a, 12b, 12c, and 12d extending from the stem 10a. The lead pins 12a are FG terminals electrically connected to the package 8a, and are insulated from any of the electric elements of the TOSA 4a housed in the package 8a. The lead pins 12b and 12c are light emission drive terminals connected to the anode terminal and the cathode terminal of the laser diode 7, respectively. The lead pin 12d is a monitor output terminal for monitoring the light output of the laser diode 7. is there.

  The TOSA 4 a having the above configuration is fixed to the side wall 6 a by fitting the side wall 6 a of the case 6 into the groove 18. In this way, the case 6 of the optical transceiver module 2 and the package 8a of the TOSA 4a are electrically connected.

  The ROSA 4b is an optical receiver subassembly having a photodiode (not shown) and a package 8b made of a metal material that accommodates the photodiode (the portion excluding the sleeve from the optical receiver subassembly corresponds to the optical receiver module). .) The package 8b is covered with a sleeve made of a resin material. The package 8b is electrically insulated from any of the electric elements accommodated by the ROSA 4b. The ROSA 4b is provided with a groove 18a similarly to the TOSA 4a, and the side wall 6a of the case 6 is fitted into the groove 18a. Thereby, ROSA4b is fixed to the side wall 6a. The ROSA 4b package 8b is insulated from the side wall 6a by a sleeve made of a resin material covering the package. Further, the ROSA 4b has a plurality of lead pins 12e, and each lead pin 12e is connected to a plurality of electrodes made of a metal material provided on the main surface M1 of the circuit board 5.

  The circuit board 5 is a circuit board for electrically connecting the TOSA 4a and the ROSA 4b to an electronic circuit (circuit unit) 24 described later, and includes a main circuit board 5a and a sub circuit board 5b. On the main surface M1 of the main circuit board 5a, a plurality of electrode patterns such as conductive portions 20a to 20c made of a metal material are formed. The conductive portions 20b and 20c are electrically connected to the electronic circuit 24, and the conductive portion 20a is electrically connected to the SG electrode provided in the main circuit board 5a. The lead pins 12b and 12c of the TOSA 4a are electrically connected to the conductive portions 20b and 20c by solder bonding, respectively.

  The electronic circuit 24 has a signal ground potential (SG potential) and is provided on the main surface M1 of the circuit board 5 on which the conductive portions 20a to 20c are provided. The electronic circuit 24 is equipped with an amplifier circuit for amplifying the received signal from the ROSA 4b, a drive circuit for driving the laser diode 7 of the TOSA 4a, and the like.

  Next, the configuration of the sub circuit board 5b will be described. FIG. 2 is a longitudinal sectional view along the central axis direction of the TOSA 4a of the sub circuit board 5b in FIG.

  Sub circuit board 5b is placed on main surface M1 of main circuit board 5a, and substrates (insulating layers) 26a, 26b, 26c, and 26d made of an insulating material such as a sheet-like prepreg are arranged on main surface M1. The layers are stacked in this order as viewed from the side. A conductive layer 28a, which is an electrode pattern made of a metal material, is formed on one main surface M2 of the sub circuit board 5b on the main circuit board 5a side, that is, on the surface of the board 26a. A conductive layer 30a as an electrode pattern is formed on the other main surface M3, that is, on the surface of the substrate 26d. The conductive layer 30a is an electrode for connecting the lead pin 12a of the TOSA 4a, and the conductive layer 28a is an electrode for connecting to the conductive portion 20a of the main circuit board 5a.

  Further, the sub circuit board 5b includes a metal conductive layer 28b formed on the boundary surface between the board 26a and the board 26b so as to face the conductive layer 28a with the board 26a interposed therebetween, and a board 26c and a board 26d. Further, a metal conductive layer 28c formed to face the conductive layer 28b across the substrates 26b and 26c on the boundary surface is formed. The conductive layer 28c is connected to the conductive layer 28a and the conductive layer 28b through a through hole 32 formed so as to penetrate the three substrates 26a, 26b, and 26c. The conductive layer 28b penetrates the substrate 26a. The conductive layer 28a is also electrically connected through the formed through hole 34. The through holes 32 and 34 may be filled with a metal material, or may be coated with a metal material only on the inner surface. Accordingly, the conductive layers 28a, 28b, and 28c constitute one conductive portion 28 that is electrically connected to each other.

  Further, on the sub circuit board 5b, a metal conductive layer 30b is formed on the boundary surface between the board 26b and the board 26c so as to face the conductive layer 30a with the boards 26c and 26d interposed therebetween. The conductive layer 30b is electrically connected to the conductive layer 30a through a through hole 36 formed so as to penetrate the two substrates 26c and 26d. The through hole 36 may be filled with a metal material or may be coated with a metal material only on the inner surface. Therefore, the conductive layers 30a and 30b constitute one conductive portion 30 that is electrically connected to each other.

  Thus, the conductive layers 28b and 28c of the conductive portion 28 and the conductive layers 30b and 30a of the conductive portion 30 are formed on the sub circuit board 5b so as to face each other. Further, the insulating substrate 26b is disposed between the conductive layer 28b and the conductive layer 30b adjacent to the conductive layer 28b, so that a capacitance component is formed between the conductive layer 28b and the conductive layer 30b. become. Similarly, substrates 26d and 26c are respectively disposed between the conductive layer 28c and the two conductive layers 30a and 30b adjacent to the conductive layer 28c, so that the space between the conductive layer 28c and the conductive layers 30a and 30b is set. Capacitance components are formed.

  FIG. 3 is a longitudinal sectional view taken along the central axis of the TOSA 4a showing a connection form between the sub circuit board 5b, the TOSA 4a and the main circuit board 5a. As shown in the figure, the sub circuit board 5b is placed on the main surface M1 of the main circuit board 5a with the conductive part 20a and the conductive layer 28a of the sub circuit board 5b facing each other. The layer 28a is electrically connected by solder bonding. The conductive portion 20a of the main circuit board 5a is connected to an SG electrode formed inside the main circuit board 5a through a through hole. Here, the sub circuit board 5b is arranged so that an end thereof protrudes from the main surface M1 of the main circuit board 5a toward the TOSA 4a. Further, the TOSA 4a is disposed so that the lead pin 12a extends substantially linearly along the main surface M3 toward the conductive layer 30a on the main surface M3 of the sub circuit board 5b. The lead pin 12a and the conductive layer 30a are It is electrically connected by solder joint.

  According to the optical transceiver module 2 described above, the FG lead pin 12a of the TOSA 4a connected to the FG is connected to the conductive layer 30a formed on the main surface M3 of the sub circuit board 5b and the sub circuit board 5b. The sub circuit board 5b is placed on the main circuit board 5a with the conductive layer 28a formed on the main surface M2 facing and connected to the conductive portion 20a of the main circuit board 5a. As a result, the capacitance component formed by the sub circuit board 5b is connected between the FG lead pin 12a and the conductive portion 20a of the main circuit board 5a, and the capacitance component of the noise filter can be easily secured. Further, even when the distance between the conductive portion 20a of the main circuit board 5a and the FG lead pin 12a is increased due to the arrangement restrictions, the length of the FG lead pin 12a itself is shortened by connecting via the sub circuit board 5b. Therefore, the inductance of the FG lead pin 12a is reduced, and high frequency noise can be effectively released from the FG to the SG. As a result, the influence of radiation noise such as crosstalk in the TOSA 4a package can be sufficiently suppressed. Particularly, since the sub circuit board 5b is arranged so that the end thereof protrudes from the main surface M1 of the main circuit board 5a to the TOSA 4a side, the length of the lead pin 12a can be further shortened.

  In addition, since the capacitance component is formed by disposing the insulating layer between the conductive layers 30a and 30b and the conductive layers 28b and 28c in the sub circuit board 5b, the capacitance component can be reduced even if the sub circuit board 5b is downsized. The capacity can be easily increased, and even if the sub circuit board 5b interposed between the FG lead pin 12a and the main circuit board 5a is small, the influence of radiation noise such as crosstalk in the TOSA package can be sufficiently suppressed. . In addition, the thickness and area of the sub circuit board 5b can be variously changed, and the degree of freedom in arrangement of the TOSA 4a and the main circuit board 5a is increased.

  Further, since each of the conductive portion 28 and the conductive portion 30 is electrically connected to each other through a through hole penetrating the insulating layer, the conductive portion 28 and the conductive portion 30 are conductive even if the thickness of the sub circuit board 5b or the number of stacked layers is changed. Processing when connecting the layers becomes easy.

  FIG. 4 shows a connection form of a conventional optical transceiver module. Here, according to SFP-MSA (Small Form Factor Pluggable Multi-Source Agreement) which is an industry standard for small optical transceivers, the thickness of the connector portion of the circuit board of the optical communication module is defined as 1 mm. Therefore, in order to produce a circuit board at low cost, it is desirable to unify the thickness of the circuit board to 1 mm. In SFP-MSA, the total height of the transceiver (the total height of the main body, excluding structures protruding from the main body for engagement with the cage) is 8.6 mm to 8.5 mm, and the total width (the total width of the main body) is It is specified as 13.7 mm, and the LC connector used is also specified as 2.29 mm from the bottom of the receptacle to the optical axis. Therefore, assuming that the outer diameter of the TOSA is about 5.5 mm and the lead pin for FG is arranged on the circumference having a diameter of 4.0 mm, the lead pin is positioned at a height of about 4.5 mm at the maximum from the bottom of the transceiver. .

  In the conventional connection form shown in FIG. 4, when the above-mentioned standard is followed, the thickness D1 of the circuit board 905 is set to 1 mm, and the distance D2 from the transceiver bottom surface to the optical axis of the TOSA 904a is set to 2.29 mm. In this case, the height from the base end portion of the lead pin 912a of the TOSA 904a to the surface of the circuit board 905 is about several millimeters. Accordingly, the lead pin 912a becomes longer and the inductance of the FG lead pin 912a becomes larger. As a result, noise in the TOSA 904a package cannot be sufficiently released above a certain frequency.

  On the other hand, in order to shorten the lead pin, a method of designing a short distance in the optical axis direction of the TOSA 904a between the stem of the TOSA 904a and the circuit board 905 in FIG. However, in this case, it is necessary to bend the lead pin 912a toward the circuit board 905 at 90 degrees or more, which increases EMI (electromagnetic noise), which is not preferable. Although it is conceivable to arrange pins on the stem so that the forming of the lead pins 912a is not necessary, the circuit arrangement on the circuit board and the arrangement of the electrode patterns may be modified at any time to improve the characteristics. Therefore, it is not practical in cost to correct the pin arrangement of the TOSA each time the correction is made. In addition, from the viewpoint of component arrangement inside the TOSA, it may be impossible to correct the pin arrangement of the TOSA following the board correction. On the other hand, in the optical transceiver module 2, since the sub circuit board 5b can be connected after being created separately from the main circuit board 5a, the length of the lead pin can be shortened without causing an increase in manufacturing cost. Can do.

1 is a partially broken perspective view showing a configuration of an optical transceiver module according to a preferred embodiment of the present invention. It is a longitudinal cross-sectional view along the central axis direction of TOSA of the sub circuit board in FIG. It is a longitudinal cross-sectional view along the central axis line of TOSA which shows the connection form of the sub circuit board of FIG. 1, TOSA, and the main circuit board. It is a figure which shows the connection form of the conventional optical transceiver module.

Explanation of symbols

  2 ... Optical transceiver module, 5a ... Main circuit board, 5b ... Sub circuit board, 8a ... Package, 12a ... Lead pin for FG, 12b, 12c, 12d ... Lead pin, 20a, 20b, 20c ... Conductive part, 24 ... Electronic circuit ( Circuit portion), 26a, 26b, 26c, 26d ... substrate (insulating layer), 28, 30 ... conductive portion, 28a, 28b, 28c ... conductive layer, 30a, 30b ... conductive layer, 32, 34, 36 ... through hole, M2 , M3 ... main surface.

Claims (3)

An optical communication module for transmitting an optical transmission signal via an optical transmission medium,
An optical transmission having a metal package and a plurality of lead pins including a ground lead pin electrically connected to the package, and generating an optical transmission signal according to an electric signal applied through the plurality of lead pins Modules,
A main circuit board having a conductive portion for electrically connecting the plurality of lead pins to the circuit portion for driving the optical transmission module and a ground potential;
A capacitive component is formed between the first conductive portion provided on the first main surface and the second conductive portion provided on the second main surface, and the second conductive portion and A sub circuit board mounted on the main circuit board so as to be electrically connected in a state of facing the conductive portion of the main circuit board,
The ground lead pin is electrically connected to the first conductive portion by extending toward the first main surface.
An optical communication module comprising: The sub circuit board is formed by laminating a plurality of insulating layers,
Each of the first and second conductive portions includes a plurality of first and second conductive layers independently formed on the plurality of insulating layers,
Each of the plurality of first conductive layers and the plurality of second conductive layers is electrically connected to each other, and the second conductive layer is adjacent to the first conductive layer and the first conductive layer. The capacitive component is formed by disposing the insulating layer between
The optical communication module according to claim 1. Each of the plurality of first conductive layers and the second conductive layer is electrically connected to each other through a through hole penetrating the insulating layer.
The optical communication module according to claim 1 or 2.

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