Abstract:
A method of assembling a photoelectric conversion module is disclosed. The photoelectric conversion module includes a circuit board on which are mounted a light emitting element, a light receiving element, and an optical element optically connected to the light emitting element and the light receiving element. The light emitting element is positioned on the circuit board based on a positioning mark formed on the circuit board beforehand. The light receiving element and the optical element are positioned based on a position of a light emission point of the light emitting element.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to photoelectric conversion modules, assembling methods thereof, high-speed transmission connectors, and mounting systems, and more particularly to a photoelectric conversion module, an assembling method thereof, a high-speed transmission connector, and a mounting system for connecting a telecommunication line and an optical communication line. 
     2. Description of the Related Art 
     Conventional transmission lines employed as global standard interfaces for standards such as 10GFC and 10GBASE-CX4 have limitations in that the transmission distance is short, at around 20 m. 
     Accordingly, methods have been proposed for increasing the transmission distance by combining high-speed transmission lines with optical transmission lines using these interfaces. 
     However, conventional photoelectric conversion units installed in transceivers used for optical communication are large and expensive. The photoelectric conversion units need to be turned into modules and reduced in size. 
     SUMMARY OF THE INVENTION 
     The present invention provides a photoelectric conversion module, an assembling method thereof, a high-speed transmission connector, and a mounting system in which one or more of the above-described disadvantages is eliminated. 
     A preferred embodiment of the present invention provides a photoelectric conversion module that can be made compact, an assembling method thereof, a high-speed transmission connector having the photoelectric conversion module mounted therein, and a mounting system. 
     An embodiment of the present invention provides a method of assembling a photoelectric conversion module including a circuit board on which are mounted a light emitting element, a light receiving element, and an optical element optically connected to the light emitting element and the light receiving element, the method including the steps of (i) positioning the light emitting element on the circuit board based on a positioning mark formed on the circuit board beforehand; (ii) positioning the light receiving element based on a position of a light emission point of the light emitting element positioned at step (i); and (iii) positioning the optical element based on the position of the light emission point of the light emitting element positioned at step (i). 
     An embodiment of the present invention provides a method of assembling a photoelectric conversion module including a circuit board on which are mounted a light emitting element, a driver IC that drives the light emitting element, a light receiving element, a receiver IC that receives signals from the light receiving element, and an optical element optically connected to the light emitting element and the light receiving element, the method including the steps of (i) mounting bare chips on the circuit board, wherein the light emitting element, the driver IC, the light receiving element, and the receiver IC are the bare chips; (ii) covering the bare chips with the optical element; and (iii) sealing a periphery of the optical element with a resin so that the bare chips are sealed by the optical element and the resin. 
     An embodiment of the present invention provides a mounting system for mounting on a circuit board a light emitting element, a light receiving element, and an optical element optically connected to the light emitting element and the light receiving element, the mounting system including an imaging device configured to pick up an image of a stage on which the circuit board is mounted; a mounting device configured to mount the light emitting element, the light receiving element, and the optical element on the circuit board; and a control device configured to recognize, based on the image picked up by the imaging device, a positioning mark formed on the circuit board beforehand, cause the mounting device to position the light emitting element on the circuit board based on the recognized positioning mark, recognize, based on the image picked up by the imaging device, a position of a light emission point of the light emitting element positioned by the mounting device, cause the mounting device to position the light receiving unit on the circuit board based on the recognized position of the light emission point, and cause the mounting device to position the optical element on the circuit board based on the recognized position of the light emission point. 
     An embodiment of the present invention provides a photoelectric conversion module including an electric connector to which a telecommunication line is to be connected; a circuit board mounted with a converting unit configured to convert an electric signal supplied to the electric connector from the telecommunication line into an optical signal to be supplied to an optical communication line, and convert an optical signal supplied from the optical communication line into an electric signal to be supplied to the telecommunication line via the electric connector; and a waveguide configured to connect the converting unit and the optical communication line; wherein the circuit board is a single board, and the electric connector and the waveguide are mounted on the circuit board. 
     An embodiment of the present invention provides a photoelectric conversion module including a circuit board, a light emitting element, a driver IC that drives the light emitting element, a light receiving element, a receiver IC that receives signals from the light receiving element, and a waveguide member optically connected to the light emitting element and the light receiving element, wherein the light emitting element, the driver IC, the light receiving element, and the receiver IC are bare chips and are mounted on the circuit board as the bare chips, the waveguide member covers the bare chips, and a periphery of the waveguide member is sealed with a resin so that the bare chips are sealed by the waveguide member, the circuit board, and the resin. 
     According to one embodiment of the present invention, a photoelectric conversion module that can be made compact, an assembling method thereof, a high-speed transmission connector having the photoelectric conversion module mounted therein, and a mounting system are provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of an embodiment of the present invention; 
         FIGS. 2A-2D  are schematic diagrams of an embodiment of the present invention; 
         FIG. 3  is an exploded perspective view of an embodiment of the present invention; 
         FIG. 4  is a block diagram of an embodiment of the present invention; 
         FIG. 5  is a schematic diagram of a circuit board; 
         FIG. 6  is a schematic diagram of relevant parts of the circuit board; 
         FIG. 7  is a perspective view of a waveguide array; 
         FIGS. 8A-8E  are schematic diagrams of the waveguide array; 
         FIG. 9  is a block diagram of a mounting system; and 
         FIG. 10  is a flowchart of a process performed by a control device. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     A description is given, with reference to the accompanying drawings, of embodiments of the present invention. 
       FIG. 1  is a perspective view of an embodiment of the present invention,  FIGS. 2A-2D  are schematic diagrams of an embodiment of the present invention,  FIG. 3  is an exploded perspective view of an embodiment of the present invention, and  FIG. 4  is a block diagram of an embodiment of the present invention. 
     A high-speed transmission connector  100  according to an embodiment of the present invention includes an electric connector  111 , a circuit board  112 , a waveguide array  113 , and an optical socket connector  114 , which are housed in a housing  117 . The housing  117  includes a case  115  and a cover  116 . The housing  117  is thus a sealed container within which built-in circuits are sealed. 
     The electric connector  111  is, for example, a socket connector, which is used for performing high-speed balanced transmission. The electric connector  111  is soldered and surface mounted onto one side of the circuit board  112  at one edge. A plug connector attached to a high-speed balanced transmission cable is to be inserted in the electric connector  111 . The electric connector  111  supplies electric signals received from the high-speed balanced transmission cable to the circuit board  112 , and also supplies electric signals received from the circuit board  112  to the high-speed balanced transmission cable. 
       FIG. 5  is a schematic diagram of the circuit board  112 . 
     The circuit board  112  is configured by, for example, one multilayer printed wiring board. On one side of the circuit board  112 , the electric connector  111 , a driver IC  121 , a light emitting element  122 , a light receiving element  123 , a receiver IC  124 , and the waveguide array  113  are surface mounted. On the other side of the circuit board  112 , various IC and chip components configuring a microcomputer  125  and a power supply circuit  126  are surface mounted. 
     The electric connector  111  is soldered to a pad P formed at the edge of the circuit board  112  in the direction denoted by an arrow X 1 . The pad P is connected to the driver IC  121 , the receiver IC  124 , the microcomputer  125 , and the power supply circuit  126  via a balanced transmission pattern L. The balanced transmission pattern L is connected to the driver IC  121 , the receiver IC  124 , the microcomputer  125 , and the power supply circuit  126  via through holes H and through a middle layer of the circuit board  112 . 
     The paths of the balanced transmission pattern L are adjusted in a middle layer of the circuit board  112 . For example, the paths are adjusted so that the wiring distance between the pad P and the driver IC  121  and the wiring distance between the pad P and the receiver IC  124  are substantially the same. Accordingly, the transmission properties can be made uniform between plural balanced transmission lines for transmission and plural balanced transmission lines for reception. Therefore, other adjustments are not necessary for making transmission properties uniform between balanced transmission lines at the circuit board  112 . As a result, the number of components can be reduced, such that the circuit board  112  can be made compact. 
       FIG. 6  is a schematic diagram of relevant parts of the circuit board  112 . 
     The driver IC  121  and the receiver IC  124  are configured of bare chips, and are directly wire-bonded to patterns  131  formed on the circuit board  112 . 
     The driver IC  121  is connected to the light emitting element  122 , and drives the light emitting element  122  according to signals received from the electric connector  111 . The light emitting element  122  is configured with a vertical-cavity surface-emitting laser (VCSEL) diode including plural light emitting points  132  arranged linearly. The light emitting element  122  is arranged so that the light emitting points  132  are located on a predetermined axis I of the circuit board  112 . 
     The light receiving element  123  is, e.g., a PD including plural light receiving points  133  arranged linearly. The light receiving points  133  convert light received from the waveguide array  113  to electric signals, and supply the electric signals to the receiver IC  124 . The light receiving element  123  is arranged so that the light receiving points  133  are located on the predetermined axis I of the circuit board  112 . 
     In the present embodiment, the light emitting points  132  of the light emitting element  122  and the light receiving points  133  of the light receiving element  123  are aligned in one row on the axis I. However, the emitting points  132  of the light emitting element  122  and the light receiving points  133  of the light receiving element  123  need not be aligned in one row; they can be arranged in two or more rows or in a matrix. 
     The receiver IC  124  amplifies electric signals received from the light receiving element  123 , and supplies the amplified electric signals to the electric connector  111  via the balanced transmission pattern L. 
     The driver IC  121  is adjacent to the light emitting element  122 , and is located in the direction indicated by the arrow X 1  with respect to the predetermined axis I. The receiver IC  124  is adjacent to the light receiving element  123 , and is located in the direction indicated by an arrow X 2  with respect to the predetermined axis I, on the side opposite to the driver IC  121 . 
     In the present embodiment, the driver IC  121  is located across the light emitting element  122  and the light receiving element  123  from the receiver IC  124 , to reduce the layout area and the mounting area, and to suppress noise therebetween. However, the driver IC  121  and the receiver IC  124  can be adjacent to each other, arranged on the same side, so that the transmission distances of the driver IC  121  and the receiver IC  124  can be made equal. Accordingly, the impedance can be easily matched, which is advantageous for a high-speed balanced transmission line. 
     The circuit board  112  has plural positioning marks M 1 , M 2  near the driver IC  121 , the light emitting element  122 , the light receiving element  123 , and the receiver IC  124  for determining positions of the driver IC  121 , the light emitting element  122 , the light receiving element  123 , the receiver IC  124 , and the waveguide array  113 . 
     The marks M 1 , M 2  and the light emitting element  122  are recognized by an imager, the light emitting element  122  is positioned by using the marks M 1 , M 2  as references, and is fixed to the circuit board  112 . The light emitting points  132  of the light emitting element  122  are recognized by an imager, and the light receiving element  123  and the waveguide array  113  are positioned by using the light emitting points  132  of the light emitting element  122  as references. 
     Accordingly, the plural light emitting points  132  of the light emitting element  122  and the plural light receiving points  133  of the light receiving element  123  are arranged facing the edge surfaces of the waveguides of the waveguide array  113 . 
     The driver IC  121 , the light emitting element  122 , the light receiving element  123 , and the receiver IC  124  are arranged beneath the waveguide array  113 , and the periphery of the waveguide array  113  is sealed by sealing resin. Thus, the driver IC  121 , the light emitting element  122 , the light receiving element  123 , and the receiver IC  124  are shielded from outside, so that even bare chips can be protected from outside influences. 
     The power supply circuit  126  is arranged on an opposite surface of the circuit board  112 , at a position corresponding to the driver IC  121 , the light emitting element  122 , the light receiving element  123 , and the receiver IC  124 . Therefore, the power supply circuit  126  is located close to the driver IC  121 , the receiver IC  124 , and the microcomputer  125 . 
     The microcomputer  125  controls the driver IC  121  and the receiver IC  124  and adjusts the communication status and laser output in order to stabilize communications. 
       FIG. 7  is a perspective view of the waveguide array  113 , and  FIGS. 8A-8E  are schematic diagrams of the waveguide array  113 . 
     The waveguide array  113  is formed by molding transparent resin, and is configured of a waveguide body  141  and a flange part  142 . 
     The waveguide body  141  is a substantially concave shape, in which the base side, i.e., the side of the direction indicated by an arrow Z 1 , is an aperture, and the top side, i.e., the side of the direction indicated by an arrow Z 2 , is a curved surface. The top curved surface of the waveguide body  141  includes a waveguide unit  151  including plural waveguides used for transmission and a waveguide unit  152  including plural waveguides used for reception. The curved surface is a substantially cylindrical surface, and the curvature thereof is specified such that light does not leak outside from the waveguide units  151 ,  152 . 
     The waveguide units  151 ,  152  each include plural waveguides. Each waveguide of the waveguide units  151 ,  152  is arranged so that one end extends in a direction orthogonal to the circuit board  112 , i.e., the direction indicated by the arrow Z 1 , and the other end extends in a direction parallel to the circuit board  112 , i.e., the direction indicated by the arrow X 2 . The cross-sectional shapes of the waveguides of the waveguide units  151 ,  152  are squares having substantially 50 μm sides. 
     There are three protruding parts  153  provided on the rim of the base side of the waveguide body  141 . Each protruding part  153  has a hemispherical shape. When the waveguide array  113  is mounted on the circuit board  112 , the three protruding parts  153  abut on the circuit board  112 . As the three protruding parts  153  abut on the circuit board  112 , the contact area between the waveguide array  113  and the circuit board  112  is minimized. Accordingly, the waveguide array  113  can be slid on the circuit board  112 . This facilitates the process of determining the position of the waveguide array  113 . 
     Because of the protruding parts  153 , a gap is formed between the circuit board  112  and the base side of the waveguide array  113  when the waveguide array  113  is mounted on the circuit board  112 . This gap is sealed by sealing resin. Accordingly, the driver IC  121 , the light emitting element  122 , the light receiving element  123 , and the receiver IC  124  are sealed inside. 
     Lens units  154 ,  155  are provided where the waveguide units  151 ,  152  meet the base side of the waveguide body  141 . The lens units  154 ,  155  each include plural lenses. Surfaces of the lenses of the lens unit  154  have spherical shapes. Light beams emitted by the light emitting points  132  of the light emitting element  122  are condensed at these lenses and are incident on the edge faces of the waveguides of the waveguide unit  151 . Surfaces of the lenses of the lens unit  155  have spherical shapes. The lens unit  155  causes light beams irradiated from the edge faces of the waveguides of the waveguide unit  152  to condense at the light receiving points  133  of the light receiving element  123 . 
     The lens units  154 ,  155  are arranged opposite to the light emitting points  132  of the light emitting element  122  and the light receiving points  133  of the light receiving element  123 , respectively. 
     Due to the protruding parts  153 , the lens units  154 ,  155  of the waveguide array  113  can be spaced apart from the light emitting/receiving elements  122 ,  123  by precise distances. 
     The flange part  142  protrudes from the edge of the base in the direction indicated by the arrow X 1  of the waveguide body  141 . The driver IC  121  is arranged beneath the flange part  142 . 
     Lens units  156 ,  157  are provided where the waveguide units  151 ,  152  meet the side surface of the waveguide body  141  in the direction indicated by the arrow X 2 . The lens units  156 ,  157  each include plural lenses. 
     On the side surface of the waveguide body  141  in the direction indicated by the arrow X 2 , holes  158  are formed on both sides of the lens units  156 ,  157 . An optical connector attached to the end of an optical communication line engages with the holes  158 , so that waveguides of the optical communication line face the lenses of the lens units  156 ,  157 . The optical connector attached to the end of the optical communication line is inserted through the optical socket connector  114  and held by the housing  117 . 
     Surfaces of the lenses of the lens unit  156  have spherical shapes. The lens unit  156  causes light beams irradiated from the edge faces of the waveguides of the waveguide unit  151  to condense at the edge face of the optical communication line. Surfaces of the lenses of the lens unit  157  have spherical shapes. The lens unit  157  causes light beams irradiated from the edge face of the optical communication line to condense at the edge face of the waveguide unit  152 . 
     The above-described lens units  154 ,  155 ,  156 ,  157  can prevent diffusion and attenuation of light, so that communications are performed efficiently. 
     As described above, the waveguide array  113  can introduce light beams from the optical communication line to the circuit board  112 , and also introduce light beams from the circuit board  112  to the optical communication line. 
     In the present embodiment, the receiver IC  124  is arranged beneath the waveguide body  141  and the driver IC  121  is arranged beneath the flange part  142 ; however, the driver IC  121  can be arranged beneath the waveguide body  141  and the receiver IC  124  can be arranged beneath the flange part  142 . 
     The driver IC  121  and the receiver IC  124  can be arranged next to each other, and arranged together beneath the waveguide body  141  or the flange part  142 . 
       FIG. 9  is a block diagram of a mounting system. 
     A mounting system  200  includes a control device  211 , a mounting device  212 , an imaging device  213 , and a stage  214 . 
     The control device  211  can communicate with an upper-level device, and acquires an image from the imaging device  213  according to a command from the upper-level device. Based on the acquired image, the control device  211  drives the mounting device  212  so as to mount the driver IC  121  for emitting light, the light emitting element  122 , the light receiving element  123 , the receiver IC  124  for receiving light, and the waveguide array  113  on the circuit board  112  mounted on the stage  214 . 
       FIG. 10  is a flowchart of a process performed by the control device  211 . 
     In step S 1 - 1 , the circuit board  112  is mounted on the stage  214 , and the control device  211  receives a mounting instruction from the upper-level device. In step S 1 - 2 , the control device  211  causes the imaging device  213  to pick up an image of the circuit board  112 , and recognizes the marks M 1 , M 2  from the picked up image. Specifically, the control device  211  performs a process such as binarization on the picked up image, performs image analysis on the binarized image, and recognizes the marks M 1 , M 2 . 
     Next, the control device  211  recognizes the position at which the light emitting element  122  is mounted by using the recognized marks M 1 , M 2  as reference coordinates. In step S 1 - 3 , the control device  211  controls the mounting device  212  to handle the light emitting element  122 . In steps S 1 - 4  and S 1 - 5 , the operation of controlling the position of the light emitting element  122  is continued until the light emitting element  122  is positioned at a predetermined position. The control device  211  analyzes images being picked up by the imaging device  213  to recognize the position of the light emitting element  122  from the shape of the light emitting element  122 . 
     In step S 1 - 6 , the control device  211  causes the imaging device  213  to pick up images of the circuit board  112  to recognize the light emitting points  132  of the light emitting element  122  based on the picked up images. The control device  211  analyzes the images being picked up by the imaging device  213  to recognize the position of the light emitting points  132  of the light emitting element  122  from the shape of the light emitting element  122  and the shapes of the light emitting points  132 . In step S 1 - 7 , the control device  211  controls the mounting device  212  to handle the light receiving element  123 . In steps S 1 - 8  and S 1 - 9 , the operation of controlling the position of the light receiving element  123  is continued until the light receiving element  123  is positioned at a predetermined position. 
     In step S 1 - 10 , the control device  211  causes the imaging device  213  to pick up images of the circuit board  112  to recognize the light emitting points  132  of the light emitting element  122  based on the picked up images. The control device  211  analyzes the images being picked up by the imaging device  213  to recognize the position of the light emitting points  132  of the light emitting element  122  from the shape of the light emitting element  122  and the shapes of the light emitting points  132 . In step S 1 - 11 , the control device  211  controls the mounting device  212  to handle the waveguide array  113 . In steps S 1 - 12  and S 1 - 13 , the operation of controlling the position of the waveguide array  113  is continued until the waveguide array  113  is positioned at a predetermined position. 
     According to the present embodiment, images picked up by the imaging device  213  are analyzed to recognize the marks M 1 , M 2  and the light emitting element  122  from shapes thereof. The light emitting element  122  is positioned by using the recognized marks M 1 , M 2  as references. Accordingly, the light emitting element  122  can be precisely positioned on the circuit board  112 . The imaging device  213  is caused to pick up images of the light emitting element  122  precisely positioned on the circuit board  112 , the light emitting points  132  are recognized from the picked up images, and the light receiving element  123  is positioned by using the recognized light emitting points  132  as references. Accordingly, the light emitting points  132  and the light receiving points  133  of the light receiving element  123  can be positioned even more precisely. 
     Further, the imaging device  213  is caused to pick up images of the light emitting element  122  precisely positioned on the circuit board  112 , the light emitting points  132  are recognized from the picked up images, and the waveguide array  113  is positioned by using the recognized light emitting points  132  as references. Accordingly, the lens units  154 ,  155  formed on the base side of the waveguide array  113  can be precisely positioned with respect to the light emitting points  132  of the light emitting element  122 . Therefore, the lens units  154 ,  155  can be even more precisely positioned with respect to the light emitting units  132 . 
     As a result, the light emitting points  132  of the light emitting element  122 , the light receiving points  133  of the light receiving element  123 , and the lens units  154 ,  155  of the light receiving points  133  can be precisely positioned. 
     By employing the mounting method according to the present embodiment, elements can be positioned relatively precisely with reduced errors. Furthermore, elements can be positioned and mounted while recognizing positions from images. Therefore, production can be performed at low cost. 
     After mounting the waveguide array  113 , the periphery of the waveguide array  113  is sealed with sealing resin. Accordingly, the bare chips, namely the driver IC  121 , the light emitting element  122 , the light receiving element  123 , and the receiver IC  124  can be sealed beneath the waveguide array  113 , so that the elements and the ICs are protected. 
     The present embodiment describes a photoelectric conversion module including four lines for transmission and four lines for reception, to which the present invention is not limited. There can be one transmission line, or more transmission lines than described above. There is no constraint on the number of lines. 
     According to one embodiment of the present invention, elements of a photoelectric conversion module can be miniaturized, so that a photoelectric conversion module and a high-speed transmission connector can be made compact. 
     Further, according to one embodiment of the present invention, production efficiency is enhanced, and therefore, manufacturing is performed at low cost. 
     The present invention is not limited to the specifically disclosed embodiment, and variations and modifications may be made without departing from the scope of the present invention. 
     The present application is based on Japanese Priority Patent Application No. 2006-186883, filed on Jul. 6, 2006, Japanese Priority Patent Application No. 2006-186884, filed on Jul. 6, 2006, and Japanese Priority Patent Application No. 2006-186885, filed on Jul. 6, 2006, the entire contents of which are hereby incorporated by reference.