Signal transmission device

A signal transmission device includes a base plate and a photoelectric converter-sealed member. The base plate is structured to have an optical waveguide formed internally, an opening formed to expose the optical waveguide, and a mounting surface provided to allow an electronic part to be mounted thereon. The photoelectric converter-sealed member is placed in the opening of the base plate to include a photoelectric conversion module for making conversion between an electric signal and a light signal and provided by sealing at least the photoelectric conversion module with a predetermined material to expose at least part of a wiring from the photoelectric conversion module on a substantially identical plane with an opening end face of the opening of the base plate. The opening is either a recess or a through hole. This arrangement desirably ensures the higher-speed transmission of electric signals between the photoelectric conversion module and the LSI package.

TECHNICAL FIELD

The present invention relates to a signal transmission device.

BACKGROUND ART

One proposed structure of a signal transmission device has a base plate with an internally formed optical waveguide. A light emitting element, such as a laser diode, of inputting light into the optical waveguide is placed in a recess formed in the direction of depth of the base plate from its surface (see, for example, Patent Document 1). In the signal transmission device of this prior art structure, an electronic part with a driving circuit for driving the light emitting element is mounted on a rear face of the base plate. This arrangement aims to shorten the wiring length of an electrical connection between the driving circuit of the electronic part and the light emitting element placed in the recess and thereby reduce a response delay of the light emitting element.Patent Document 1: Japanese Patent Laid-Open No. 2001-174657 (FIG. 6)

DISCLOSURE OF THE INVENTION

The signal transmission device is generally desired to input and output electric signals at a higher speed from and to an electronic part, for example, an LSI (large scale integration) package, mounted on the base plate. The signal transmission device is also desired to be readily made an electrical connection with the mounted LSI package.

In the signal transmission device, there would thus be a demand for ensuring the higher-speed input and output of electric signals from and to a mounted electronic part. In the signal transmission device, there would also be a demand for facilitating an electrical connection with a mounted electronic part.

The present invention accomplishes at least part of the demand mentioned above and the other relevant demands by the following configurations applied to the signal transmission device.

According to one aspect, the invention is directed to a signal transmission device constructed to transmit a signal. The signal transmission device has: a base plate structured to have an optical waveguide formed internally, an opening formed to expose the optical waveguide, and amounting surface provided to allow an electronic part to be mounted thereon; and a photoelectric converter-sealed member placed in the opening of the base plate to include a photoelectric conversion module for making conversion between an electric signal and a light signal and provided by sealing at least the photoelectric conversion module with a predetermined material to expose at least part of a wiring from the photoelectric conversion module on a substantially identical plane with an opening end face of the opening of the base plate.

In the signal transmission device according to this aspect of the invention, the photoelectric converter-sealed member is placed at the opening of the base plate having the mounting surface for mounting the electronic part. The photoelectric converter-sealed member has the photoelectric conversion module designed to make conversion between electric signals and light signals. At least the photoelectric conversion module is sealed with the predetermined material in such a manner that at least part of the wiring from the photoelectric conversion module is exposed on the substantially same plane as the opening end face of the opening of the base plate. Since at least part of the wiring from the photoelectric conversion module is exposed on the substantially identical plane with the opening end face of the opening of the base plate, an electrical connection between the wiring from the photoelectric conversion module and the electronic part mounted on the base plate is made on the substantially same plane as the opening end face of the opening of the base plate. This arrangement ensures the higher-speed input and output of electric signals from and to the mounted electronic part. The exposure of the wiring from the photoelectric conversion module on the substantially same plane as the opening end face of the opening of the base plate facilitates the electrical connection with the electronic part mounted on the base plate. The predetermined material may be any of various materials, for example, a translucent epoxy resin or a non-translucent epoxy resin. Typical examples of the electronic part include an LSI, an IC (integrated circuit), a capacitor chip, a resistor chip, and an electric connector electrically connectable with a cable of another device.

In one preferable application of the signal transmission device according to this aspect of the invention, the photoelectric converter-sealed member is formed by sealing the opening of the base plate with the predetermined material to locate the opening of the base plate on a substantially identical plane with the mounting surface of the base plate for mounting the electronic part in such a manner that the photoelectric conversion module and the wiring, which are placed in the opening of the base plate. Sealing the opening of the base plate with the predetermined material to make the opening on the substantially same plane as the mounting surface for mounting the electronic part allows the electronic part to be hung over the opening on the base plate. This arrangement desirably increases the packaging density of the electronic part.

In one preferable embodiment of the invention, the signal transmission device further has: a radiator member attached to a rear face of the base plate opposed to the mounting surface of the base plate for mounting the electronic part; and a heat radiation wiring arranged to connect the radiator member with the photoelectric conversion module in a thermally conductive manner. This arrangement enables heat produced by the photoelectric conversion module to be released by the radiator member via the heat radiation wiring and prevents a significant temperature rise of the photoelectric conversion module.

In another preferable application of the signal transmission device according to the above aspect of the invention, the photoelectric converter-sealed member has a module mount designed to have the photoelectric conversion module and the wiring attached thereto and to work in cooperation with the predetermined material to seal the photoelectric conversion module. The use of the module mount enables the wiring from the photoelectric conversion module to be arranged on the substantially same plane as the opening end face of the opening. This arrangement allows an electrical connection with the electronic part mounted on the base plate to be made on the substantially same plane as the opening end face, thus ensuring the higher-speed input and output of electric signals from and to the electronic part. In this application, the module mount may have a connection terminal arranged to electrically connect the wiring with a terminal provided at an outer circumference of at least part of the opening on the mounting surface of the base plate. The use of the connection terminal provided on the module mount facilitates the electrical connection of the wiring from the photoelectric conversion module with the mounted electronic part.

In one preferable embodiment of the signal transmission device of the invention, the photoelectric conversion module has a photoelectric conversion element arranged to allow input and output of a light signal from and to the optical waveguide and make conversion between the light signal and an electric signal, and an electronic circuit designed to input and output the electric signal from and to the photoelectric conversion element. In this embodiment, the photoelectric conversion module has the electronic circuit located close to the photoelectric conversion element and linearly connected with the photoelectric conversion element by means of an inner-module wiring. This arrangement desirably shortens the wiring length of the inner-module wiring and ensures the high-speed input and output of electric signals between the photoelectric conversion element and the electronic circuit, compared with an arrangement of the electronic circuit at a position relatively farther from the photoelectric conversion element and a non-linear connection between the photoelectric conversion element and the electronic circuit by the inner-module wiring. The ‘photoelectric conversion element’ includes a light emitting element of converting an input electric signal into a light signal and a light receiving element of converting an input light signal into an electric signal. The ‘electronic circuit’ includes a driving circuit designed to output the electric signal to the light emitting element and thereby drive the light emitting element and an amplification circuit designed to amplify the electric signal input from the light receiving element.

In one preferable embodiment of the signal transmission device of the invention having any of the above configurations, the opening is either a recess formed in a direction of depth of the base plate from the mounting surface for mounting the electronic part or a through hole pierced from the mounting surface to a rear face of the base plate opposed to the mounting surface.

In the signal transmission device of the invention having any of the above configurations, the optical waveguide may be formed in a planar direction of the base plate. This arrangement enables propagation of the light signal in the planar direction of the base plate.

BEST MODES OF CARRYING OUT THE INVENTION

Some modes of carrying out the invention are described below as preferred embodiments with reference to the accompanied drawings.

FIG. 1is a plan view showing the schematic configuration of a signal transmission device20equipped with LSI packages10aand10bhaving multiple data input and output pins and power supply pins and designed to transmit signals input from and output to the LSI packages10aand10bas a first embodiment of the invention.FIG. 2is a sectional view showing a cross section of the signal transmission device20, taken on a line A-A inFIG. 1. The signal transmission device20has a base plate30, photo electric converter-sealed members40and60, and radiator members90aand90battached to a rear face of the base plate30. The base plate30has recesses32aand32bformed in its depth direction from its mounting surface. The LSI packages10aand10bare mounted on the signal transmission device20to be partially hung over the recesses32aand32b. Photoelectric conversion modules42and62are respectively arranged in the recesses32aand32bto make conversion between electric signals and light signals input from and output to the LSI packages10aand10band are sealed in the photoelectric converter-sealed members40and60.

The base plate30is constructed as a multi-layered circuit board with six optical waveguides34arranged substantially in parallel in its planar direction for propagation of light. The recesses32aand32bare formed to expose respective opposite ends of the six optical waveguides34. Each of the optical waveguides34is constructed as a light waveguide where a core (not shown) made of a material having a relatively high refractive index is surrounded by a clad (not shown) made of a material having a lower refractive index than the material of the core. Light is propagated mainly through the core. The base plate30also has power supply wirings36aand36bconnected with a power supply source (not shown) mounted on the surface of the base plate30and with a ground (not shown) and laid internally to supply a power supply potential and a ground potential to the photoelectric conversion modules42and62. The base plate30further has heat radiation wirings38a,38b,38c, and38darranged to connect the photoelectric conversion modules42and62with the radiator members90aand90bon the rear face of the base plate30in a thermally conductive manner.

In the photoelectric converter-sealed members40and60, the recesses32aand32bare sealed with resin sealers45and65of a translucent epoxy resin in such a manner that wirings44and64extended upward from the photoelectric conversion modules42and62are exposed to opening end faces of the recesses32aand32b, that is, top faces of the recesses32aand32bplaced in the practically same plane as the surface of the base plate30. Any suitable method may be adopted to seal the recesses32aand32bwith the resin sealers45and65. One available method places the photoelectric conversion modules42and62on the bottoms of dies having a substantially identical shape with that of the recesses32aand32b, pours the translucent epoxy resin into the dies to be cured, and inserts the cured resin parts including the photoelectric conversion modules42and62in the recesses32aand32b. Another available method places the photoelectric conversion modules42and62in the bottoms of the recesses32aand32band pours the translucent epoxy resin into the recesses32aand32bto be cured. The detailed structures of the photoelectric conversion modules42and62will be discussed later.

A terminal14ais provided on the wiring44exposed on the opening end face of the recess32a, and a signal pin12aof the LSI package10ais placed on the terminal14a. The wiring44, the terminal14a, and the signal pin12are thus electrically connected to allow the photoelectric conversion module42to input and output electric signals from and to the LSI package10avia the wiring44, the terminal14a, and the signal pin12a. Similarly a terminal14band a signal pin12bof the LSI package10bare sequentially placed on the wiring64exposed on the opening end face of the recess32b. The wiring64, the terminal14b, and the signal pin12bare thus electrically connected to allow the photoelectric conversion module62to input and output electric signals from and to the LSI package10bvia the wiring64, the terminal14b, and the signal pin12b. In the structure of the first embodiment, the wirings44and64from the photoelectric conversion modules42and62are exposed on the respective opening end faces of the recesses32aand32bto be arranged in the substantially same plane. It is thus not necessary to make wirings from the photoelectric conversion modules42and62internally laid in the base plate30as in the conventional structure of the base plate. This arrangement desirably shortens the wiring lengths from the photoelectric conversion module42to the LSI package10aand from the photoelectric conversion module62to the LSI package10b, compared with the conventional structure with the wirings from the photoelectric conversion modules internally laid in the base plate. The shorter wiring lengths allow relatively high-speed input and output of electric signals between the photoelectric conversion module42and the LSI package10aand between the photoelectric conversion module62and the LSI package10b. The recesses32aand32bare sealed to make the opening end faces of the recesses32aand32bin the substantially same plane as the mounting surface of the base plate30. As shown inFIGS. 1 and 2, the LSI packages10aand10bmay thus be arranged to be partially hung over the recesses32aand32b. This arrangement effectively increases the packaging density, compared with the conventional structure of the base plate that does not allow LSI packages to be hung over the recesses32aand32b. The signal pins12aand12bof the LSI packages10aand10bhaving the relatively high-speed signal input and output capabilities are placed over the corresponding recesses32aand32b. Among signal pins of the LSI packages10aand10b, pins (not shown) connecting with the power supply source, grounded pins (not shown), and signal pins (not shown) having the relatively low-speed signal input and output capabilities are arranged not to be placed over the recesses32aand32b. These pins arranged not to be placed over the recesses32aand32bare connected with an electrode pattern formed on the surface of the base plate30. The reason for such arrangement of the LSI packages10aand10bon the base plate30will be explained later.

The detailed structures of the photoelectric conversion modules42and62are described below.

Each of the photoelectric conversion modules42and62has an electric-optical converter46designed to convert electric signals to light signals and an optical-electric converter66designed to convert light signals to electric signals. The electric-optical converter46of the photoelectric conversion module42is arranged to face the optical-electric converter66of the photoelectric conversion module62across three optical waveguides34among the six optical waveguides34. The optical-electric converter66of the photoelectric conversion module42is arranged to face the electric-optical converter46of the photoelectric conversion module62across the other three optical waveguides34.

The electric-optical converter46of the photoelectric conversion module42and the optical-electric converter66of the photoelectric conversion module62are described in detail below.

The electric-optical converter46has laser diodes47positioned to enable light to enter the corresponding optical waveguides34exposed to the recess32a, a driving IC48used to drive the laser diodes47, and an interposer49provided as a printed circuit board with the laser diodes47and the driving IC48placed on the surface thereof.

The laser diodes47are electrically connected with the driving IC48by patterned wirings50formed on the surface of the interposer49or by wire bonding (not shown). The laser diodes47are electrically connected with internal wiring for power supply (not shown) in the interposer49, which is electrically connected with the power supply wirings36aand36bof the base plate30, and receive a required supply of electric power through the power supply wirings36aand36b. The main body of each laser diode47is attached to a heat radiation electrode54formed on the surface of the interposer49to allow transmission of heat of the laser diode47. The heat radiation electrode54is connected in a thermally conductive manner with heat radiation internal wiring56of the interposer49, which is connected in a thermally conductive manner with the heat radiation wiring38aof the base plate30. Heat is accordingly conducted from the laser diodes47to the radiator member90avia the heat radiation electrodes54, the heat radiation internal wirings56, and the heat radiation wirings38a. Namely the radiator member90areleases the heat of the laser diodes47and accordingly prevents a significant temperature rise of the laser diodes47.

The driving IC48is electrically connected with the wiring44exposed on the recess32a. A relatively high-speed electric signal is input from the signal pin12aof the LSI package10ainto the driving IC48. The driving IC48is electrically connected with the internal wiring for power supply (not shown) in the interposer49, which is electrically connected with the power supply wirings36aand36bof the base plate30, and receives a required supply of electric power through the power supply wirings36aand36b. The main body of the driving IC48is attached to a heat radiation electrode59formed on the surface of the interposer49. The heat radiation electrode59is connected in a thermally conductive manner with heat radiation internal wiring61of the interposer49, which is connected in a thermally conductive manner with the heat radiation wiring38bof the base plate30. Heat is accordingly conducted from the driving IC48to the radiator member90avia the heat radiation electrode59, the heat radiation internal wiring61, and the heat radiation wiring38b. Namely the radiator member90areleases the heat of the driving IC48and accordingly prevents a significant temperature rise of the driving IC48.

The optical-electric converter66has photo diodes67positioned to receive light emitted from the end faces of the corresponding optical waveguides34exposed to the recess32b, an amplification IC68used to amplify electric signals output from the photo diodes67, and an interposer69provided as a printed circuit board with the photo diodes67and the amplification IC68placed on the surface thereof.

The photo diodes67are electrically connected with the amplification IC68by patterned wirings70formed on the surface of the interposer69or by wire bonding (not shown). The photo diodes67are electrically connected with internal wiring for power supply (not shown) in the interposer69, which is electrically connected with the power supply wirings36aand36bof the base plate30, and receive a required supply of electric power through the power supply wirings36aand36b. The main body of each photo diode67is attached to a heat radiation electrode74formed on the surface of the interposer69. The heat radiation electrode74is connected in a thermally conductive manner with heat radiation internal wiring76of the interposer69, which is connected in a thermally conductive manner with the heat radiation wiring38cof the base plate30. Heat is accordingly conducted from the photo diodes67to the radiator member90bvia the heat radiation electrodes74, the heat radiation internal wirings76, and the heat radiation wirings38c. Namely the radiator member90breleases the heat of the photo diodes67and accordingly prevents a significant temperature rise of the photo diodes67.

The amplification IC68is electrically connected with the wiring64exposed on the recess32bto output an electric signal to the signal pin12bof the LSI package10b. The amplification IC68is electrically connected with the internal wiring for power supply (not shown) in the interposer69, which is electrically connected with the power supply wirings36aand36bof the base plate30, and receives a required supply of electric power through the power supply wirings36aand36b. The main body of the amplification IC68is attached to a heat radiation electrode79formed on the surface of the interposer69in a thermally conductive manner. The heat radiation electrode79is connected in a thermally conductive manner with heat radiation internal wiring81of the interposer69, which is connected in a thermally conductive manner with the heat radiation wiring38dof the base plate30. Heat is accordingly conducted from the amplification IC68to the radiator member90bvia the heat radiation electrode79, the heat radiation internal wiring81, and the heat radiation wiring38d. Namely the radiator member90breleases the heat of the amplification IC68and accordingly prevents a significant temperature rise of the d amplification IC68.

In the signal transmission device20of the first embodiment constructed as described above, the electric signal output from the signal pin12aof the LSI package10aenters the signal pin12bof the LSI package10baccording to a series of operations described below.

The electric signal output from the signal pin12aof the LSI package10aenters the driving IC48of the electric-optical converter46in the photoelectric conversion module42. The driving IC48drives the laser diode47, in response to the input electric signal. The driven laser diode47then outputs a light signal corresponding to the input electric signal. The electric signal input from the signal pin12ais thus converted into the light signal by the electric-optical converter46. The converted light signal passes through the exposed end of the optical waveguide34to the recess32ato enter the optical waveguide34, is propagated through the optical waveguide34, and is output from the opposite exposed end of the optical waveguide34on the recess32b. The light signal output from the optical waveguide34is received by the photo diode67of the optical-electric converter66in the photoelectric conversion module62. The photo diode67outputs an electric signal corresponding to the received light signal to the amplification IC68. The amplification IC68amplifies the input electric signal. The light signal output from the optical waveguide34is thus converted into the electric signal by the optical-electric converter66. The converted electric signal is input into the signal pin12bof the LSI package10b. The signal transmission device20of the embodiment transmits the electric signal in the form of the light signal in the above manner on the route from the signal pin12aof the LSI package10ato the signal pin12bof the LSI package10b. This characteristic of the signal transmission device20accomplishes the higher-speed signal transmission, compared with the conventional printed circuit board with only the standard electric wirings.

The photoelectric conversion modules42and62and the optical waveguides34of the base plate30are activated to transmit only the relatively high-speed signals from the signal pin12aof the LSI package10ahaving the relatively high-speed signal input and output capability. The electrode pattern formed on the mounting surface of the base plate30is used, on the other hand, to transmit the power supply potential from the power supply pin and the low-speed signals from the signal pin having the low-speed signal input and output capability. Namely the photoelectric conversion modules42and62and the optical waveguides34are used only for the signals requiring high-speed transmission.

As described above, in the signal transmission device20of the first embodiment, the wirings44and64from the photoelectric conversion modules42and62are exposed on the respective opening end faces of the recesses32aand32bto be arranged in the substantially same plane. This arrangement desirably shortens the wiring lengths from the photoelectric conversion module42to the LSI package10aand from the photoelectric conversion module62to the LSI package10b, compared with the conventional structure with the wirings from the photoelectric conversion modules internally laid in the base plate. The shorter wiring lengths allow the higher-speed input and output of electric signals between the photoelectric conversion module42and the LSI package10aand between the photoelectric conversion module62and the LSI package10b. The wirings44and64from the photoelectric conversion modules42and62are exposed on the respective opening end faces of the recesses32aand32bto be arranged in the substantially same plane. Such exposure facilitates the connection of the photoelectric conversion module42with the signal pin12aof the LSI package10avia the terminal14a, as well as the connection of the photoelectric conversion module62with the signal pin12bof the LSI package10bvia the terminal14b. The recesses32aand32bare sealed to make the opening end faces of the recesses32aand32bin the substantially same plane as the mounting surface of the base plate30for the LSI packages10aand10b. The LSI packages10aand10bcan thus be placed to be partially hung over the corresponding recesses32aand32b. This increases the packaging density. The radiator members90aand90battached to the rear face of the base plate30are used respectively to release the heat of the laser diodes47and the driving IC48and to release the heat of the photo diodes67and the amplification IC68. This arrangement desirably prevents a significant temperature rise of the laser diodes47and the driving IC48, as well as a significant temperature rise of the photo diodes67and the amplification IC68.

In the signal transmission device20of the first embodiment, the LSI packages10aand10bare arranged to be partially hung over the respective recesses32aand32b. This arrangement is, however, neither essential nor restrictive. The LSI packages10aand10bmay be arranged not to be hung over the respective recesses32aand32b.

In the signal transmission device20of the first embodiment, the recesses32aand32bare sealed such as to make the wirings44and64from the photoelectric conversion modules42and62extended upward from the interposers49and69of the photoelectric conversion modules42and62and exposed on the respective opening end faces of the recesses32aand32b. This arrangement is, however, neither essential nor restrictive. Any other suitable arrangement or route is allowed, as long as the wirings44and64from the photoelectric conversion modules42and62are at least partly exposed on the respective opening end faces of the recesses32aand32b. For example, the wirings44and64from the photoelectric conversion modules42and62may be laid inside the interposers49and69to go through the respective bottoms of the recesses32aand32band may be extended upward from spaces between a side wall of the recess32aand the photoelectric conversion module42and between a side wall of the recess32band the photoelectric conversion module62to be exposed on the substantially same plane as the respective opening end faces of the recesses32aand32b. In another example, the wirings44and64from the photoelectric conversion modules42and62may be laid inside the interposers49and69and may be extended horizontally along the respective bottoms of the recesses32aand32band upward along the respective side faces of the recesses32aand32bto be exposed on the substantially same plane as the respective opening end faces of the recesses32aand32b.

In the signal transmission device20of the first embodiment, the radiator members90aand90bare attached to the rear face of the base plate30. The radiator members90aand90band the heat radiation wirings38a,38b,38c, and38dmay be omitted, when the heat generated by the laser diodes47, the driving IC48, the photo diodes67, and the amplification IC68is a relatively small amount and does not require heat release. In this modified structure, the interposers49and69may not be equipped with the heat radiation electrodes54,59,74, and79or the heat radiation internal wirings56,61,76, and81.

In the signal transmission device20of the first embodiment, the power supply wirings36aand36bare extended from the mounting surface of the base plate30for the LSI packages10aand10bto be laid inside the base plate30and arranged in the bottom faces of the recesses32aand32b. As long as the arrangement ensures the supply of electric power to the photoelectric conversion modules42and62, the power supply wirings36aand36bmay be extended from the surfaces of the photoelectric converter-sealed members40and60to be laid inside the resin sealers45and65and arranged on the surfaces of the interposers49and69.

A signal transmission device120is described below as a second embodiment of the invention.FIG. 3is a plan view showing the schematic configuration of the signal transmission device120of the second embodiment.FIG. 4is a sectional view showing a cross section of the signal transmission device120, taken on a line B-B inFIG. 3. The signal transmission device120of the second embodiment has the common structure to that of the signal transmission device20of the first embodiment, for example, the LSI packages10aand10bmounted on a base plate. In order to avoid the repeated explanation, the like elements of the signal transmission device120of the second embodiment to those of the signal transmission device20of the first embodiment are expressed by the like numerals and are not specifically described here.

The signal transmission device120has a base plate130with through holes132aand132bpenetrating from its mounting surface for the LSI packages10aand10bto its rear face, and photoelectric converter-sealed members140and160to seal therein photoelectric conversion modules142and162, which are respectively arranged in the through holes132aand132bto make conversion between electric signals and light signals input from and output to the LSI packages10aand10b.

As illustrated, the base plate130is constructed as a multi-layered circuit board with six optical waveguides34and power supply wirings36aand36bin a similar manner to the structure of the base plate30in the signal transmission device20of the first embodiment. The through holes132aand132bare formed to expose respective opposite ends of the six optical waveguides34. Terminals14aand14bare electrically connected with signal pins12aand12bof the LSI packages10aand10band are provided on the respective outer circumferential faces of the through holes132aand132bon the surface of the substrate130. The power supply wirings36aand36bpass through via holes137aand137b, which are formed in the base plate130to the depth of a wiring layer of internal wiring for power supply (not shown) and are exposed on the surface of the base plate130.

The photoelectric conversion modules142and162of the photoelectric converter-sealed members140and160have similar structures to those of the photoelectric conversion modules42and62of the first embodiment, except omission of the interposers49and69. As illustrated, in the photoelectric converter-sealed members140and160, the photoelectric conversion modules142and162are sealed in the through holes132aand132bby means of module mounts192aand192bwith the photoelectric conversion modules142and162mounted thereon and resin sealers145and165for sealing the through holes132aand132b. Wirings44and64from the photoelectric conversion modules142and162are exposed on the surfaces of the resin sealers145and165, are extended to the outer circumferences of the throughholes132aand132b, and are attached to the module mounts192aand192b. Any suitable method may be adopted to form the photoelectric converter-sealed members140and160. One available method places the photoelectric conversion modules142and162mounted on the module mounts192aand192bon the bottoms of dies having a substantially identical shape with that of the through holes132aand132b, pours a translucent epoxy resin into the dies to be cured, and inserts the cured resin parts including the photoelectric conversion modules142and162in the through holes132aand132b. In the illustration ofFIG. 4, there are height differences between the opening end faces of the through holes132aand132bor the surface of the base plate130and the surfaces of the resin sealers145and165. But the illustration of these height differences aims to clearly show the mounting positions of the wirings44and64. In the actual state, however, the thicknesses of the wirings44and64and of connection terminals194aand194bare negligible compared with the thickness of the base plate130. The surface of the base plate130or the opening end faces of the through holes132aand132bcan thus be regarded to be in the substantially same plane as the surfaces of the resin sealers145and165.

The extended ends of the wirings44and64to the outer circumferences of the through holes132aand132bare provided with the connection terminals194aand194bthat are electrically connected to the terminals14aand14bof the base plate130and with connection terminals196aand196bthat are electrically connected to internal wiring for power supply (not shown) to the photoelectric conversion modules142and162and to the power supply wirings36aand36bof the base plate130. The photoelectric conversion module142inputs and outputs electric signals from and to the LSI package10avia the wiring44, the connection terminal194a, the terminal14a, and the signal pin12a. Similarly the photoelectric conversion module162inputs and outputs electric signals from and to the LSI package10bvia the wiring64, the connection terminal194b, the terminal14b, and the signal pin12b. The connection terminals194a,194b,196a, and196balso have a function of inputting light signals from the laser diodes47of the photoelectric conversion modules142and162into the optical waveguides34and a function of adjusting the heights of the photoelectric conversion modules142and162to input the light signals from the optical waveguides34into the photo diodes67. The wirings44and64from the photoelectric conversion modules142and162are exposed on the substantially same plane as the surface of the base plate130or the opening end faces of the through holes132aand132b. The wirings44and64are extended to the outer circumferences of the through holes132aand132bto connect the photoelectric conversion modules142and162with the LSI packages10aand10bon the surface of the base plate130. This arrangement ensures the higher-speed input and output of electric signals between the photoelectric conversion module142and the LSI package10aand between the photoelectric conversion module162and the LSI package10b. It is thus not necessary to make wirings from the photoelectric conversion modules internally laid in the base plate as in the conventional structure of the base plate. This arrangement also ensures the higher-speed input and output of electric signals between the photoelectric conversion module142and the LSI package10aand between the photoelectric conversion module162and the LSI package10b. The wirings44and64from the photoelectric conversion modules142and162are exposed on the surfaces of the resin sealers145and165and are extended to the outer circumferences of the through holes132aand132b. The wirings44and64are then electrically connected with the signal pins12aand12bof the LSI packages10aand10bvia the connection terminals194aand194bprovided on the extended ends of the wirings44and64to the outer circumferences of the through holes132aand132b. This arrangement facilitates the connection between the wiring44and the signal pin12aof the LSI package10aand between the wiring64and the signal pin12bof the LSI package10b.

As described above, in the signal transmission device120of the second embodiment, the wirings44and64from the photoelectric conversion modules142and162are exposed on the substantially same plane as the opening end faces of the through holes132aand132b. The wirings44and64are extended to the outer circumferences of the through holes132aand132bto connect the photoelectric conversion modules142and162with the LSI packages10aand10bon the surface of the base plate130. This arrangement ensures the higher-speed input and output of electric signals between the photoelectric conversion module142and the LSI package10aand between the photoelectric conversion module162and the LSI package10b. It is thus not necessary to make wirings from the photoelectric conversion modules and internally laid in the base plate as in the conventional structure of the base plate. This arrangement also ensures the higher-speed input and output of electric signals between the photoelectric conversion module142and the LSI package10aand between the photoelectric conversion module162and the LSI package10b. The wirings44and64from the photoelectric conversion modules142and162are exposed on the surfaces of the resin sealers145and165and are extended to the outer circumferences of the through holes132aand132b. The use of the connection terminals194aand194bprovided on the extended ends of the wirings44and64to the outer circumferences of the through holes132aand132bfacilitates the connection between the wiring44and the signal pin12aof the LSI package10aand between the wiring64and the signal pin12bof the LSI package10b.

In the signal transmission device120of the second embodiment, the connection terminals194a,194b,196a, and196bfunction to electrically connect the LSI packages10aand10bwith the photoelectric conversion modules142and162, while adjusting the heights of the photoelectric conversion modules142and162to allow input of light signals from the laser diodes47of the photoelectric conversion module142to the optical waveguides34and output of light signals from the optical waveguides34to the photo diodes67of the photoelectric conversion module162. The connection terminals194a,194b,196a, and196bmay be designed to simply make electrical connections of the LSI packages10aand10bwith the photoelectric conversion modules142and162. The connection terminals194a,194b,196a, and196bmay, however, not have the additional function of adjusting the heights of the photoelectric conversion modules142and162to allow input of light signals from the laser diodes47of the photoelectric conversion module142to the optical waveguides34and output of light signals from the optical waveguides34to the photo diodes67of the photoelectric conversion module162. One example of such modification is given as a signal transmission device220shown inFIG. 5. In this modified structure, spacers283are attached to the module mounts192aand192bto adjust the heights of the laser diodes47of the photoelectric conversion module142and the photo diodes67of the photoelectric conversion module162.

In the signal transmission device120of the second embodiment, the base plate130has the through holes132aand132b.FIG. 6shows the structure of a signal transmission device320as one modified example with a base plate330and photoelectric converter-sealed members340and360. Recesses332aand332bare formed from the surface of the base plate330in the direction of depth, in place of the through holes132aand132b. The photoelectric converter-sealed members340and360are designed arbitrarily to be placed in the recesses332aand332band to seal the photoelectric conversion modules142and162with the resin sealers345and365and the module mounts192aand192b. There may be gaps392between the resin sealer345and the bottom of the recess332aand between the resin sealer365and the bottom of the recess332b. There is accordingly a large degree of freedom in the depths of the recesses332aand332bformed in the base plate330.

In the signal transmission device120of the second embodiment, the through holes132aand132bhaving a substantially fixed width are formed from the surface of the base plate130in the direction of depth.FIG. 7shows the structure of a signal transmission device420as one modified example with a base plate430. Through holes432aand432bformed from the surface of the base plate430in the direction of depth have varied widths. The through holes432aand432bhave an identical width with the width of the module mounts192aand192bfrom the surface of the base plate430to a certain depth corresponding to the height of the module mounts192aand192band have an identical width with the width of the resin sealers145and165from the certain depth corresponding to the height of the module mounts192aand192bto the rear face of the base plate430. This arrangement causes the surfaces of the photoelectric converter-sealed members140and160to be arranged in the substantially same plane as the surface of the base plate430.

In the signal transmission device120of the second embodiment, the via holes137aand137bare formed in the base plate130to the depth of the wiring layer of internal wiring for power supply (not shown). The via holes137aand137bmay be formed to penetrate from the surface to the rear face of the base plate130. These penetrating via holes137aand137bare connectable with all wiring layers (not shown) of the base plate130.

In the signal transmission device120of the second embodiment, the photoelectric conversion modules142and162and the wirings44and64are attached to the module mounts192aand192b. In one modified structure, various electronic parts, for example, a capacitor chip, a resistor chip, an IC, and LSI, are arranged on faces of the module mounts192aand192bopposed to the mounting surfaces of the module mounts192aand192bwith the photoelectric conversion modules142and162and the wirings44and64. The electronic parts may be electrically connected with the photoelectric conversion modules142and162attached to the module mounts192aand192bthrough wirings passing through via holes (not shown) formed in the module mounts192aand192b. The module mounts192aand192bmay be constructed as multi-layered circuit boards.

In the signal transmission device120of the second embodiment, the wirings44and64from the photoelectric conversion modules142and162are connected via the connection terminals194aand194bwith the LSI packages10aand10bmounted on the surface of the base plate130. In one modification, the wirings44and64from the photoelectric conversion modules142and162may be connected with signal wiring layers provided inside the base plate130for transmission of high-frequency signals by means of predetermined wirings, which are arranged in via holes formed from the surface of the base plate130to the signal wiring layers and are electrically connected with the wirings44and64from the photoelectric conversion modules142and162. In another modification, the wirings44and64from the photoelectric conversion modules142and162may be connected with the LSI packages10aand10bmounted on the rear face of the base plate130by means of predetermined wirings, which are arranged in via holes penetrating from the surface to the rear face of the base plate130and are electrically connected with the wirings44and64from the photoelectric conversion modules142and162. Such modification allows the connection of the wirings44and64from the photoelectric conversion modules142and162with the signal wiring layers provided inside the base plate130or with the LSI packages10aand10bmounted on the rear face of the base plate130by simply forming the via holes. This arrangement desirably enhances the high frequency characteristics of signal transmission.

In the signal transmission device120of the second embodiment, the laser diodes47and the driving IC48of the photoelectric conversion module142and the photo diodes67and the amplification IC68of the photoelectric conversion module162are sealed with the resin sealers145and165and the module mounts192aand192b. The resin sealers145and165may be formed in any shape to work in cooperation with the module mounts192aand192band seal at least the laser diodes47, the driving IC48, the photo diodes67, and the amplification IC68. For example, one resin sealer may be provided in a shape of covering over the laser diodes47of the photoelectric conversion module142, and another resin sealer may be provided in a shape of covering over the driving IC48of the photoelectric conversion module142. The laser diodes47and the driving IC48of the photoelectric conversion module142are sealed with these resin sealers and the module mount192a.

FIG. 8shows the structure of a signal transmission device120B as one modified example with regard to the electric-optical converters46and the optical-electric converters66included in the photoelectric conversion modules42and62in the signal transmission device20of the first embodiment or included in the photoelectric conversion modules142and162in the signal transmission device120of the second embodiment. In the electric-optical converter46of this modified example, the driving IC48is placed close to the laser diodes47. The driving IC48is then linearly connected with the laser diodes47by patterned wirings50or by wire bonding (not shown). In the optical-electric converter66of this modified example, the amplification IC68is placed close to the photo diodes67. The amplification IC68is then linearly connected with the photo diodes67by patterned wirings70or by wire bonding (not shown). This modified structure relatively shortens the wiring lengths of the patterned wirings50and70to, for example, several millimeter levels and allows relatively high-speed transmission of electric signals between the laser diodes47and the driving IC48and between the photo diodes67and the amplification IC68. In this modified example, two wirings44aand44barranged close to each other and in parallel to each other are used for connecting the driving IC48with the LSI package10a, in place of the wiring44in the signal transmission device120of the second embodiment. Similarly two wirings64aand64barranged close to each other and in parallel to each other are used for connecting the amplification IC68with the LSI package10b, in place of the wiring64in the signal transmission device120of the second embodiment. There is accordingly differential signal transmission between the driving IC48and the LSI package10aand between the amplification IC68and the LSI package10b. The differential signal transmission desirably prevents the quality of the signal from being worsened, while allowing high-speed signal transmission between the driving IC48and the LSI package10aand between the amplification IC68and the LSI package10b. This arrangement thus ensures signal transmission from the LSI package10ato the LSI package10bat a high speed of, for example, several hundred Mbps to several ten Gbps. The laser diodes47and the driving IC48are mounted on one identical photoelectric conversion module42, so that the temperature of the laser diodes47is practically equivalent to the temperature of the driving IC48. The temperature-based operational change is thus subject to feedback control on the assumption that the laser diodes47and the driving IC48have the same temperature condition. Similarly the photo diodes67and the amplification IC68are mounted on one identical photoelectric conversion module62. The temperature-based operational change is thus subject to feedback control on the assumption that the photo diodes67and the amplification IC68have the same temperature condition. These photoelectric conversion modules42and62are sealed with the resin sealers145and165. There are relatively short wiring lengths of the patterned wirings50between the laser diodes47and the driving IC48and the patterned wirings70between the photo diodes67and the amplification IC68. This arrangement effectively reduces electromagnetic interferences from the photoelectric conversion modules42and62to the outside, as well as electromagnetic interferences from the outside to the photoelectric conversion modules42and62.

In the signal transmission device20of the first embodiment or the signal transmission device120of the second embodiment, each of the photoelectric conversion modules42and62or the photoelectric conversion modules142and162has one electric-optical converter46and one optical-electric converter66. Each of the photoelectric conversion modules42and62or the photoelectric conversion modules142and162may have multiple electric-optical converters46and multiple optical-electric converters66. Each of the photoelectric conversion modules42and62or the photoelectric conversion modules142and162may have only either the electric-optical converter46or the optical-electric converter66. In the last case, one module converts electric signals into light signals and inputs the light signals to the optical waveguides34, while the other module receives light signals from the optical waveguides34and converts the received light signals into electric signals. For example, the photoelectric conversion module42has only the electric-optical converter46, while the photoelectric conversion module62has only the optical-electric converter66. In another example, the photoelectric conversion module62has only the electric-optical converter46, while the photoelectric conversion module42has only the optical electric converter66.

In the signal transmission device20of the first embodiment or the signal transmission device120of the second embodiment, the photoelectric conversion modules42and62or the photoelectric conversion modules142and162are connected with the signal pins12aand12bof the LSI packages10aand10bhaving the relatively high-speed data output capabilities. The photoelectric conversion modules42and62or the photoelectric conversion modules142and162may alternatively be connected with signal pins of the LSI packages10aand10bhaving relatively low-speed data output capabilities.

In the signal transmission device20of the first embodiment or the signal transmission device120of the second embodiment, the recesses32aand32bor the through holes132aand132bare sealed with the resin sealers45and65or the resin sealers145and165made of the translucent epoxy resin. The resin sealers45and65or the resin sealers145and165may be made of any other suitable translucent material. In a modified structure where the resin sealers45and65or the resin sealers145and165are not interposed between the laser diode47and the optical waveguide34or between the photo diode67and the optical waveguide34, the light signal from the laser diode47is directly input into the optical waveguide34and the light signal from the optical waveguide34is directly input into the photo diode67. In this modified structure, the resin sealers45and65or the resin sealers145and165may be made of a non-translucent epoxy resin or any other suitable non-translucent material.

In the signal transmission device20of the first embodiment or the signal transmission device120of the second embodiment, the electric-optical converter46included in the photoelectric conversion modules42and62or the photoelectric conversion modules142and162has the laser diodes47arranged to emit the light signal in the planar direction of the base plate30or the base plate130. The laser diode47may be replaced with another suitable light emitting element driven by an electric signal to emit the light signal in the planar direction of the base plate30or130or with a light emitting element driven to emit the light signal in a depth direction perpendicular to the planar direction of the base plate30or130. In this latter modification, a mirror should be provided to change the direction of the light signal emitted from the light emitting element from the depth direction to the planar direction and input the light signal of the changed direction into the optical waveguide34.

In the signal transmission device20of the first embodiment or the signal transmission device120of the second embodiment, no lens for focusing the light onto the optical waveguide34or onto the photo diode67is provided at a site of inputting the light signal from the laser diode47in the electric-optical converter46of the photoelectric conversion module42,62,142, or162into the optical waveguide34or at a site of inputting the light signal from the optical waveguide34into the photo diode67. Such focusing lenses may, however, be provided at these sites.

In the signal transmission device20of the first embodiment or the signal transmission device120of the second embodiment, the optical-electric converter66included in the photoelectric conversion modules42and62or the photoelectric conversion modules142and162has the photo diodes67arranged to receive the light signal in the planar direction of the base plate30or the base plate130. The photo diode67may be replaced with another suitable light receiving element designed to receive the light signal in the planar direction of the base plate30or130and convert the received light signal into an electric signal or a light receiving element designed to receive the light signal in a depth direction perpendicular to the planar direction of the base plate30or130. In this latter modification, a mirror should be provided to change the direction of the light signal output from the optical waveguide34from the planar direction to the depth direction and input the light signal of the changed direction into the light receiving element.

In the signal transmission device20of the first embodiment or the signal transmission device120of the second embodiment, the multiple optical waveguides34are arranged in parallel with one another in the planar direction of the base plate30or130. As illustrated in a signal transmission device520ofFIG. 9given as a modified example with a base plate530and photoelectric converter-sealed members540and560, multiple optical waveguides34may be arranged in parallel with one another in a depth direction of the base plate530. In this modified structure, multiple laser diodes47and multiple photo diodes67are arrayed in the depth direction of the base plate530and are attached to upright jigs596aand596bin each of photoelectric conversion modules542and562of the photoelectric converter-sealed members540and560.

The signal transmission device20of the first embodiment or the signal transmission device120of the second embodiment has the six optical waveguides34. There is, however, no limit in number of the optical waveguides34. There may be more than six optical waveguides34or less than six optical waveguides34, even only one optical waveguide34. Each of the photoelectric conversion modules42and62or142and162is require to have a corresponding number of the laser diodes47and a corresponding number of the photo diodes67to the number of the optical waveguides34. For example, when there is only one optical waveguide34, the photoelectric conversion module42may have only one laser diode47, while the photoelectric conversion module62may have only one photo diode67.

In the signal transmission device20of the first embodiment or the signal transmission device120of the second embodiment, the optical waveguides34are formed in the planar direction of the base plate30or the base plate130. The optical waveguides34may, however, be formed in any suitable direction of the base plate30or130. In such modification, the recesses32aand32bof the base plate30or the through holes132aand132bof the base plate130should be arranged to expose the respective ends of the optical waveguides34. The photoelectric converter-sealed members40and60or140and160should then be placed in the recesses32aand32bor in the through holes132aand132bto ensure input and output of light signals between the photoelectric conversion modules42and62or142and162and the optical waveguides34.

In the signal transmission device20of the first embodiment or the signal transmission device120of the second embodiment, the LSI packages10aand10bare mounted on the base plate30or the base plate130, and the photoelectric conversion modules42and62or142and162are connected with the LSI packages10aand10b. Any other suitable electronic parts, for example, ICs, capacitor chips, resistor chips, or electric connectors electrically connectable with a cable of another device, may be mounted on the base plate30or the base plate130.

The embodiments and their modified examples discussed above are to be considered in all aspects as illustrative and not restrictive. There may be many other modifications, changes, and alterations without departing from the scope or spirit of the main characteristics of the present invention.

INDUSTRIAL APPLICABILITY

The technique of the present invention is preferably applied to the manufacturing industry of signal transmission devices.