JP2009054758A - Optical communication apparatus and its shielding structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical communication apparatus suppressing transmission of high frequency noise to a photoelectric conversion circuit and transmitting data with high reliability, and also to provide its shielding structure. <P>SOLUTION: The apparatus is provided with an FG pattern 3, and a photoelectric conversion module 2 and control IC are loaded. The photoelectric conversion module 2 converting an optical signal into an electric signal and having a sub-shielding case 28 are loaded on a base substrate 1 fixed to a housing 7. The FG pattern 3 is ground-connected to the photoelectric conversion module 2 through wiring patterns 4A and 4B and resistance chips 27A and 27B. Skin effect attenuation members 8A and 8B constituted by applying an adhesion material containing metallic particles to a conductive tape are formed in the wiring patterns 4A and 4B, and they suppress high frequency current conducting the wiring patterns 4A and 4B by a skin effect. A skin effect attenuation member 13 is formed in a place where the FG pattern 3 is connected to the housing 7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical communication device and a shield structure thereof.

  In recent years, with rapid progress of digital information processing technology, high-speed, large-capacity, high-reliability digital communication technology is required. Signal transmission using printed wiring boards and metal wires has limitations in data transfer speed and transmission distance due to signal quality degradation and electromagnetic noise. Therefore, image data or the like is transmitted as an optical signal.

  When transmitting as an optical signal, on the transmission side, the electrical signal is converted into an optical signal by an electro-optical conversion device such as a semiconductor laser and incident on one end of an optical transmission medium such as an optical fiber or an optical waveguide. A method is used in which an optical signal is returned to an electrical signal by a photoelectric conversion device such as a photodiode (PD) optically coupled to the other end or a photoelectric conversion circuit.

  For example, the photoelectric conversion circuit receives an optical signal with a photodiode and converts it into a current, further converts the current into a differential electrical signal with a TIA (Transfer Impedance Amplifier), further amplifies it with an LA (limiting Amplifier), It is configured to output a dynamic signal.

  The input of the TIA is high impedance, and the optical system has an opening that cannot be shielded to cover the whole, so that noise propagates through the space. In addition, there is noise that disturbance noise received by the housing enters through transmission of GND (ground).

  In general, a metal shield case that covers an electronic circuit on a substrate is known as means for preventing external noise (see Patent Document 1). In addition, a high-frequency suppressor made of a high-permeability conductive soft magnetic film is provided on the outer periphery of the lead frame to suppress noise by the skin effect (see Patent Document 2), pin contact, and socket contact. There is known a connector (see Patent Document 3) that suppresses high-frequency conduction noise by providing a high-frequency current suppressing body on the surface of an insulator that holds the coil.

Further, in electronic devices, countermeasures against ESD (electrostatic discharge) are required. ESD is a phenomenon in which a high-voltage discharge occurs when a conductive object such as a charged human body or insulator comes into contact with or approaches another conductive object (such as an electronic device). When ESD occurs in an electronic device, it may cause a malfunction or damage to a semiconductor element.
Japanese Utility Model Publication No. 60-190097 JP 2007-43096 A JP 2001-283986 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical communication apparatus and its shield structure capable of suppressing transmission of high-frequency noise to a photoelectric conversion circuit and performing highly reliable data transmission.

  In order to achieve the above object, one embodiment of the present invention provides the following optical communication device.

[1] A photoelectric conversion module that converts an optical signal into an electric signal, a conductor that is derived from the photoelectric conversion module and connected to the ground, and a high frequency that is provided on the conductor and that conducts the conductor by a skin effect An optical communication device comprising: a skin effect attenuation member that suppresses current.

[2] The optical communication device according to [1], wherein the photoelectric conversion module includes a shield case, and the conductor is connected to the shield case.

[3] The photoelectric conversion module is mounted on a substrate, the conductor is formed on the substrate, and the skin effect attenuation member is provided on the substrate so as to cover the conductor. The optical communication device according to [1], which is characterized in that

[4] The optical communication according to [1], wherein the skin effect attenuation member includes a conductive tape and an adhesive material applied to the conductive tape and having metal particles dispersed therein. apparatus.

[5] The optical communication device according to [1], wherein the skin effect attenuating member is provided at an end of the conductor on the photoelectric conversion module side.

[6] The optical communication device according to [1], wherein the skin effect attenuating member is provided at a portion where a substrate on which the photoelectric conversion module is mounted is fixed to the ground with a screw. .

  One embodiment of the present invention provides the following shield structure in order to achieve the above object.

[7] A module that outputs a weak electrical signal is mounted, a substrate having a ground conductor connected to the module, and a ground conductor on the substrate are provided so as to cover the substrate, And a skin effect attenuating member that suppresses a high-frequency current conducted through the conductor by a skin effect.

  According to the optical communication device of the first aspect, it is possible to suppress high-frequency noise from being transmitted to the photoelectric conversion circuit and to perform highly reliable data transmission.

  According to the optical communication device of the second aspect, it is possible to suppress high frequency noise for the photoelectric conversion module including the shield case.

  According to the optical communication device of the third aspect, it is possible to suppress high-frequency noise in the configuration in which the photoelectric conversion module and the conductor are provided on the substrate.

  According to the optical communication device of the fourth aspect, the skin effect attenuation member can be configured easily and inexpensively.

  According to the optical communication apparatus of the fifth aspect, it is possible to identify the optimum place for suppressing noise.

  According to the optical communication device of the sixth aspect, it is possible to identify the optimum place for suppressing noise.

  According to the shield structure of the seventh aspect, it is possible to suppress the transmission of the external noise and the noise during the ESD test to the photoelectric conversion circuit, so that the data transmission can be performed with high reliability.

[First Embodiment]
(Configuration of optical communication device)
FIG. 1 is a plan view showing an optical communication apparatus according to the first embodiment of the present invention. 2 is a cross-sectional view taken along line AA of the optical communication apparatus of FIG.

  The optical communication apparatus 100 includes a base substrate 1, a photoelectric conversion module 2 mounted on the base substrate 1, an FG (frame ground) pattern 3 provided on the base substrate 1, and a photoelectric conversion provided on the base substrate 1. The wiring patterns 4A and 4B as conductors for electrically connecting the ground of the conversion module 2 and the FG pattern 3, the control LSI 5 for processing the received signal, and the photoelectric conversion module 2 are connected via the optical connector 62. An optical transmission medium 6 and a metal housing 7 that houses the base substrate 1 and the photoelectric conversion module 2 are provided.

  The base substrate 1 is made of an insulating substrate such as glass epoxy resin, and is fixed to the housing 7 with screws 11 and conductive spacers 12. The FG pattern 3 and the housing 7 of the base substrate 1 are electrically connected to each other. It is connected. The screw 11 is screwed to the spacer 12 via a ring-shaped skin effect attenuation member 13. The structure of the skin effect attenuating member 13 will be described later with reference to FIG. The base substrate 1 is further fixed to the housing 7 by a plurality of sets of screws 11 and spacers 12.

  The photoelectric conversion module 2 is disposed on the lower side of the base substrate 1, and the holder 21 into which the optical connector 62 of the optical transmission medium 6 is inserted, and the light receiving device 22 disposed to face the optical connector 62 of the optical transmission medium 6. A rigid board 23 on which the light receiving device 22 is mounted, a flexible board 24 connected to the rigid board 23, a rigid board 25 connected to the flexible board 24, a board connector 26 connected to the rigid board 25, and wiring Resistor chips 27A and 27B having one ends connected to the ends of the patterns 4A and 4B, and a sub-shield case 28 having ground connection portions 28a and 28b connected to the other ends of the resistor chips 27A and 27B. Has been.

  The light receiving device 22 includes a light receiving element such as a photodiode (not shown), a TIA (Transfer Impedance Amplifier) that converts a minute current change from the light receiving element into a differential electric signal of a voltage change, and a TIA differential output signal. LA (Limiting Amplifier) to be amplified. The TIA has a high-impedance configuration in which its input section is susceptible to noise.

  The rigid substrate 23 connects the light receiving device 22 and the flexible substrate 24 and is attached to the holder 21.

  The rigid board 25 connects the flexible board 24 to the board connector 26 and is attached to the board connector 26.

  The board connector 26 outputs a signal from the rigid board 25 to the control LSI 5 by a wiring pattern (not shown) provided on the lower surface (back surface) of the base substrate 1.

  The resistor chips 27A and 27B are provided for the purpose of setting the ground reference potential of the sub-shield case 28 and suppressing radiation noise, for example, 5 to 10Ω.

  The sub shield case 28 is formed by processing a metal plate such as brass into a box shape, and covers the holder 21, the light receiving device 22, the rigid substrate 23, the flexible substrate 24, the rigid substrate 25, and the optical connector 62, and prevents external noise. While having a shape to suppress, the ground connection portions 28a and 28b are provided.

  The wiring patterns 4A and 4B are conductors made of copper foil or the like, and skin effect attenuation members 8A and 8B having the same configuration as the skin effect attenuation member 13 are attached. The skin effect attenuation members 8A and 8B are attached to predetermined positions of the wiring patterns 4A and 4B so as to cover the wiring patterns 4A and 4B. The structure of the skin effect attenuation members 8A and 8B will be described later with reference to FIG.

  The optical transmission medium 6 is, for example, an optical fiber, and an optical plug adapter 61 is connected to an end of the optical transmission medium 6. Further, the optical connector 62 is connected to the optical plug adapter 61, and the optical connector 62 is connected to the photoelectric conversion module 2. Photocoupled.

  The housing 7 serves as a main body of the optical communication device 100, and includes a power supply device (not shown).

(Structure of skin effect damping member)
FIG. 3 is a cross-sectional view showing the skin effect attenuation member. The skin effect attenuating members 8A and 8B and the skin effect attenuating member 13 have different external shapes but the same cross-sectional structure, and are adhered to one surface of the conductive tape 201 in a state where the conductive tape 201 and the metal particles 202 are dispersed. The adhesive material 203 is used and cut into a desired shape for use.

  The skin effect attenuation members 8 </ b> A, 8 </ b> B, and 13 are attached between the housing 7 and the subshield case 28 of the photoelectric conversion module 2. The size (surface area) of the skin effect attenuation members 8A and 8B is, for example, 20 × 20 mm, and the outer diameter of the skin effect attenuation member 13 is, for example, 20 mm in diameter (in this case, the spacer 12 has a diameter of 6 mm). is there.

  The thickness of the skin effect attenuating members 8A, 8B, 13 is not less than the skin depth (skin depth: the depth of current flowing through the conductor due to the skin effect). The skin depth varies depending on the material, operating frequency, and the like, but is, for example, 4.6 μm at 300 MHz in the case of aluminum.

  For example, the conductive tape 201 has a thickness of 250 μm, and a metal foil, a metal thin plate, a conductive cloth, or the like can be used. Specifically, “conductive cloth tape” such as “TR series” manufactured by Takeuchi Kogyo Co., Ltd. and “CSTK” manufactured by Kitagawa Kogyo Co., Ltd. is optimal.

  The adhesive material 203 has a thickness of 50 μm, for example. In this case, the metal particles 202 having a diameter of 50 μm or less are used.

  The metal particles 202 are conductive and have a shape excellent in the degree of bonding with the adhesive material 203, for example, a copper-made granular material having irregularities and stabs on the surface. By providing the metal particles 202, the current flowing by the skin effect flows to the conductive tape 201 and is also dispersed and conducted on the surface of the metal particles 202, thereby enhancing the effect of attenuating the high-frequency current.

(Operation of optical communication device)
Next, the operation of the optical communication apparatus 100 shown in FIG. 1 will be described. When an optical signal enters the optical transmission medium 6 from the transmission side (not shown), the optical signal propagates through the optical transmission medium 5 and enters the light receiving device 22 via the optical plug adapter 61 and the optical connector 62 shown in FIG. .

  The light receiving device 22 converts the optical signal from the optical transmission medium 6 into an electric signal by the light receiving element, and outputs the amplified signal to the rigid substrate 23 as a received signal. The received signal is transmitted to the board connector 26 via the rigid board 23, the flexible board 24, and the rigid board 25, and further transmitted to the control LSI 5 via a wiring pattern (not shown) on the back surface of the base board 1. The control LSI 5 generates, for example, an image signal based on the received signal.

  On the other hand, noise from the housing 7 tries to enter the photoelectric conversion module 2 through the spacer 12, the FG pattern 3, the wiring patterns 4A and 4B, and the resistance chips 27A and 27B, but high frequency noise is generated on the surface of the conductor. Since the skin effect concentrated on the surface becomes remarkable, noise conduction is blocked by the skin effect attenuation member 13 provided on the screw 11 and the skin effect attenuation members 8A and 8B provided on the wiring patterns 4A and 4B. Transmission to the module 2 is suppressed. According to the study by the present inventors, it was possible to confirm the attenuation of the skin effect up to 300 MHz or more.

(ESD test)
Next, the ESD test will be described. The ESD test is, for example, “IEC61000-4-2” or the like, and a contact discharge test is applied to a conductive part such as metal and an air discharge test is applied to a non-conductive part. The test conditions are set according to a predetermined level, but a high voltage of 2 to 8 kV for contact discharge and 2 to 15 kV for air discharge is applied.

  The rise time of the discharge current is 0.7 to 1 ns, which is extremely fast, and the discharge period is as short as several tens of ns. If the operation of the electronic device is affected, even if the normal operation is temporarily lost, it may be necessary to return to the normal state again, but if the data transmission is temporarily disturbed, a fatal transmission error will occur. There is a case.

  The influence of the ESD test on the photoelectric conversion module 2 appears on a minute current signal from the light receiving element of the photoelectric conversion module 2. For this reason, a normal differential signal causes signal disturbance in the opposite phase corresponding to the ESD application period. However, the discharge current that flows from the spacer 12 to the FG pattern 3 during the ESD test is blocked by the skin effect attenuation members 8A, 8B, and 13 in the same manner as normal noise, and the transmission of the discharge current to the photoelectric conversion module 2 is suppressed. The

[Second Embodiment]
(Configuration of optical communication device)
FIG. 4 is a plan view showing an optical communication apparatus according to the second embodiment of the present invention.

  The optical communication device 100 includes a base substrate 80, ICs 81A, 81B, 81C provided on the base substrate 80, photoelectric conversion modules 82A, 82B, 82C, 82D provided on one side of the base substrate 80 at predetermined intervals, Wiring pattern 83A connected to photoelectric conversion module 82A, wiring pattern 83B connecting photoelectric conversion module 82B and photoelectric conversion module 82C, wiring pattern 83C connected to photoelectric conversion module 82D, and wiring patterns 83A to 83D are provided. And a plurality of studs 84 grounded to the housing 7, skin effect attenuation members 85A, 85B, 85C, 85D, 13 provided at predetermined positions of the wiring patterns 83A to 83D, and photoelectric conversion modules 82A to 82D. Between the wiring patterns 83A, 83B and 83C. Vignetting resistor chips 87A, 87B, 87C, and 87D, the photoelectric conversion module 82A~82D optical transmission medium by an optical fiber connected like in 88A, 88B, 88C, is configured to include a 88D, a.

  The ICs 81A to 81C are semiconductor devices including circuits that process electric signals from the photoelectric conversion modules 82A to 82D.

  The photoelectric conversion modules 82A to 82D have the same specifications, and have the same configuration as the photoelectric conversion module 2 in the first embodiment. Therefore, description of the details of the configuration is omitted.

  The wiring patterns 83A to 83D are grounded to the housing 7 via the studs 84. Accordingly, the wiring patterns 83A to 83D are for the ground.

  The skin effect attenuation members 85A to 85D have the same configuration as the skin effect attenuation members 8A and 8B. The skin effect attenuation member 85A is provided at the end of the wiring pattern 83A on the photoelectric conversion module 82A side, and the skin effect attenuation member 85B, 85C is provided at both ends of the wiring pattern 83B on the photoelectric conversion module 82B, 82C side, The skin effect attenuation member 85D is provided at the end of the wiring pattern 83C on the photoelectric conversion module 82D side, and the skin effect attenuation member 13 is provided at the other end of the wiring pattern 83A.

(Operation of optical communication device)
Next, the operation of the optical communication apparatus 100 shown in FIG. 4 will be described. Assuming that optical signals are simultaneously transmitted to the optical transmission media 88A to 88D from the transmission side (not shown), the four optical signals enter the photoelectric conversion modules 82A to 82D from the optical transmission media 88A to 88D.

  The photoelectric conversion modules 82 </ b> A to 82 </ b> D convert the incident optical signal into an electrical signal, and output this as a received signal from the board connector 26 to the control LSI 5. The control LSI 5 generates, for example, an image signal based on the received signal. At this time, the sub-shield cases (28) of the photoelectric conversion modules 82A to 82D are grounded via the resistor chips 87A to 87D, the wiring patterns 83A to 83C, and the stud 84.

  On the other hand, noise from the housing 7 tries to enter the photoelectric conversion modules 82A to 82D via the studs 84, the wiring patterns 83A to 83C and the resistor chips 87A to 87D, but high frequency noise is concentrated on the surface of the conductor. Therefore, the skin effect is suppressed by the skin effect attenuation members 85A to 85D provided in the vicinity of the resistor chips 87A to 87D, and the transmission to the photoelectric conversion module 2 is suppressed. In the long wiring pattern 83 </ b> A, the skin effect attenuation member 13 suppresses noise from the housing 7 in addition to the skin effect attenuation member 85 </ b> A.

  Also in the ESD test, as in the first embodiment, the discharge current flowing from the stud 84 to the wiring patterns 83A to 83C during the ESD test is blocked by the skin effect attenuation members 85A to 85D. Transmission to the conversion modules 82A to 82D is suppressed.

[Third Embodiment]
(Configuration of optical communication device)
FIG. 5 is a plan view showing an optical communication apparatus according to the third embodiment of the present invention.

  The optical communication apparatus 100 according to the present embodiment includes the housing 7, the base substrate 90, the IC 81A and the driving IC 91 mounted on the base substrate 90, and light provided at predetermined intervals on one side of the base substrate 90. A transmission module (TX) 92 and photoelectric conversion modules 82A to 82C, the optical transmission media 88A to 88D connected to these modules, and the optical transmission module 92 and the photoelectric conversion modules 82A to 82C are provided on the base substrate 90. The strip-shaped FG pattern 93, the plurality of studs 84 that electrically connect the FG pattern 93 and the housing 7, and the wiring pattern that connects the FG pattern 93, the photoelectric conversion modules 82A to 82C, and the optical transmission module 92. 94A, 94B, 94C, 94D and the wiring patterns 94B to 94D provided above The skin effect attenuating members 85A, 85B, and 85C, and the resistor chips 87A, 87B, and 87C that connect the wiring patterns 94B to 94D to the ground terminals of the optical transmission module 92 and the photoelectric conversion modules 82A to 82C are configured. ing.

  Since the wiring pattern 94A is for transmission and is not affected by noise, it is not necessary to provide a skin effect attenuation member.

(Operation of optical communication device)
Next, the operation of the optical communication apparatus 100 shown in FIG. 5 will be described. When the drive IC 91 operates, the optical transmission module 92 outputs an optical signal to the optical transmission medium 88A. The optical signal propagated through the optical transmission medium 88A is received by a photoelectric conversion module provided on a reception-side substrate (not shown).

  On the other hand, if optical signals are transmitted simultaneously to the optical transmission media 88A to 88C from the transmission side (not shown), the four optical signals enter the photoelectric conversion modules 82A to 82C from the optical transmission media 88A to 88C.

  The photoelectric conversion modules 82 </ b> A to 82 </ b> C convert the incident optical signal into an electrical signal, and output this as a received signal from the board connector 26 to the control LSI 5. The control LSI 5 generates, for example, an image signal based on the received signal. At this time, the sub-shield cases (28) of the photoelectric conversion modules 82A to 82C are grounded via the resistor chips 87A to 87C, the wiring patterns 94A to 94C, the FG pattern 93, and the stud 84.

  On the other hand, noise from the housing 7 tries to enter the photoelectric conversion modules 82A to 82C via the stud 84, the FG pattern 93, the wiring patterns 94A to 94C, and the resistor chips 87A to 87C. Since the skin effect concentrated on the surface of the substrate becomes remarkable, noise conduction is blocked by the skin effect attenuation members 85A to 85C provided in the vicinity of the resistor chips 87A to 87C, and transmission to the photoelectric conversion module 2 is suppressed. .

  For the ESD test, as in the second embodiment, the discharge current flowing from the stud 84 to the wiring patterns 94B to 94D through the FG pattern 93 during the ESD test is blocked by the skin effect attenuation members 85A to 85C. The transmission of the discharge current to the photoelectric conversion modules 82A to 82C is suppressed.

[Other embodiments]
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. For example, the combination of the components between the embodiments can be arbitrarily performed.

FIG. 1 is a plan view showing an optical communication apparatus according to the first embodiment of the present invention. 2 is a cross-sectional view taken along line AA of the optical communication apparatus of FIG. FIG. 3 is a cross-sectional view showing the skin effect attenuation member. FIG. 4 is a plan view showing an optical communication apparatus according to the second embodiment of the present invention. FIG. 5 is a plan view showing an optical communication apparatus according to the third embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base substrate 2 Photoelectric conversion module 3 FG patterns 4A and 4B Wiring pattern 5 Control LSI
6 Optical transmission medium 7 Case 8A, 8B, 13 Skin effect attenuation member 11 Screw 12 Spacer 21 Holder 22 Light receiving device 23 Rigid substrate 24 Flexible substrate 25 Rigid substrate 26 Substrate connector 27A, 27B Resistor chip 28 Sub shield case 28a, 28b Ground Connection part 61 Optical plug adapter 62 Optical connector 80 Base substrate 81A, 81B, 81C IC
82A, 82B, 82C, 82D Photoelectric conversion module 83A, 83B, 83C Wiring pattern 84 Stud 85A, 85B, 85C, 85D Skin effect attenuation member 87A, 87B, 87C, 87D Resistance chips 88A, 88B, 88C, 88D Optical transmission medium 90 Base substrate 91 Drive IC
92 Optical transmission module 93 FG patterns 94A, 94B, 94C, 94D Wiring pattern 100 Optical communication device 201 Conductive tape 202 Metal particle 203 Adhesive

Claims (7)

A photoelectric conversion module that converts an optical signal into an electrical signal;
A conductor derived from the photoelectric conversion module and connected to the ground;
A skin effect attenuating member that is provided on the conductor and suppresses a high-frequency current conducted through the conductor by a skin effect;
An optical communication device comprising: The photoelectric conversion module includes a shield case,
The optical communication device according to claim 1, wherein the conductor is connected to the shield case. The photoelectric conversion module is mounted on a substrate,
The conductor is formed on the substrate;
The optical communication device according to claim 1, wherein the skin effect attenuation member is provided on the substrate so as to cover the conductor.   2. The optical communication apparatus according to claim 1, wherein the skin effect attenuating member includes a conductive tape and an adhesive material applied to the conductive tape and dispersed with metal particles.   The optical communication device according to claim 1, wherein the skin effect attenuating member is provided at an end of the conductor on the photoelectric conversion module side.   2. The optical communication apparatus according to claim 1, wherein the skin effect attenuating member is provided at a portion where a substrate on which the photoelectric conversion module is mounted is fixed to the ground with a screw. A board having a module for outputting a weak electric signal and having a ground conductor connected to the module,
A shield structure comprising a skin effect attenuating member provided on the substrate so as to cover the conductor for ground and suppressing a high-frequency current conducted through the conductor by a skin effect.

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