Abstract:
An optical coupling device of the present invention includes: a light emitting device for converting an electric signal into an optical signal and outputting the optical signal; and a light receiving device for receiving the optical signal output from the light emitting device and converting the optical signal into the electric signal, wherein: the light emitting device has a light emitting surface for outputting the optical signal; the light receiving device has a light receiving surface for receiving the optical signal: and the light emitting device and the light receiving device are arranged so that the light emitting surface and the light receiving surface oppose each other, the optical coupling device further including: a first insulative substrate on which the light emitting device is mounted; and a second insulative substrate on which the light receiving device is mounted, wherein: the first insulative substrate has a first cross section; and the second insulative substrate has a second cross section; and at least one of the first cross section and the second cross section is substantially L-shaped.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optical coupling device having a function of electrically isolating an input side and an output side from each other by converting an electrical signal into an optical signal by means of a light emitting device and converting the optical signal back into the electrical signal by means of a light receiving device. 
     2. Description of the Related Art 
     An opposed-type optical coupling device in which a light emitting device and a light receiving device are arranged to oppose each other is known in the art. FIG. 20 illustrates an optical coupling device  2000  having such a structure. The optical coupling device  2000  includes a light emitting device  1  and a light receiving device  2  which are mounted on header sections of respective lead frames  14 . The light emitting device  1  and the light receiving device  2  are wire-bonded to the respective lead frames  14  via gold wire  3 . The light emitting device  1 , the light receiving device  2  and the lead frames  14  are molded together with a light transmissive resin  5  into a rectangular parallelepiped shape. The rectangular parallelepiped structure is further molded in a light blocking resin  16 . Thus, the resulting device has a double-molded structure. 
     FIG. 21 illustrates a structure of another opposed-type optical coupling device  2100  known in the art. In the optical coupling device  2100 , substantially U-shaped insulative substrates  2106 A and  2106 B are used instead of the lead frames  14 . The light emitting device  1  and the light receiving device  2  are placed respectively in the substantially U-shaped insulative substrate  2106 A on the light emitting side and the substantially U-shaped insulative substrate  2106 B on the light receiving side. The two substantially U-shaped insulative substrates  2106 A and  2106 B are attached together so that the devices  1  and  2 , opposing each other, are optically coupled together. Wiring patterns  2104 A and  2104 B are provided on the insulative substrates  2106 A and  2106 B for the devices  1  and  2 , respectively. In FIG. 21, a line  2104 C running substantially through the center of the optical coupling device  2100  denotes an adhesive with which the insulative substrates  2106 A and  2106 B are attached together. 
     FIG. 22 illustrates a structure of still another optical coupling device  2200  using insulative substrates. The optical coupling device  2200  includes a substantially U-shaped insulative substrate  2206 A and a plate-like insulative substrate  2206 B. Wiring patterns  2204 A and  2204 B are provided on the substantially U-shaped insulative substrate  2206 A, and a wiring pattern  2204 C is provided on the plate-like insulative substrate  2206 B. The wiring pattern  2204 A extends from an area of the substantially U-shaped insulative substrate  2206 A on which the light emitting device  1  is mounted to the outside of the optical coupling device  2200 , where the wiring pattern  2204 A functions as a soldering section. The wiring pattern  2204 B extends from the bottom of one end of the plate-like insulative substrate  2206 B to the outside of the optical coupling device  2200 , where the wiring pattern  2204 B functions as a soldering section. The wiring pattern  2204 C extends from an area of the plate-like insulative substrate  2206 B where the light receiving device  2  is mounted to the bottom of one side surface of the plate-like insulative substrate  2206 B. The plate-like insulative substrate  2206 B is structurally connected to the wiring patterns  2204 A and  2204 B via solder bumps  2208 A and  2208 B. The solder bump  2208 B electrically connects the wiring pattern  2204 C to the wiring pattern  2204 B. 
     However, when a lead frame is used in an opposed-type optical coupling device, the following problems arise. The thickness of a lead frame is 0.2 mm at minimum. For the light emitting side and the light receiving side in combination, a total thickness of 0.4 mm is required for the lead section, whereby it is difficult to reduce the overall thickness of the optical coupling device. For example, in the conventional example illustrated in FIG. 20, which employs the double-molded structure, the thickness of the optical coupling device  2000  is currently 2.1 mm at minimum. 
     Moreover, in the optical coupling device  2000 , an electrical signal is first transferred to the light emitting side lead frame  14  and then to the light emitting device  1  mounted on the header section of the light emitting side lead frame  14 . The electrical signal is converted into an optical signal at the junction plane  1 A of the light emitting device  1 , and then propagated to the light receiving device  2 . The optical signal which has been emitted from the junction plane  1 A of the light emitting device  1  toward a side surface thereof is absorbed by the light transmissive resin  5 , whereby substantially no portion of the optical signal reaches the light receiving device  2 . Moreover, substantially all of the optical signal which has reached the periphery of the light transmissive resin  5  is absorbed by the light blocking resin  16  and thus is not propagated to the light receiving device  2 . Thus, the transmission efficiency is poor in this conventional example. 
     The conventional example illustrated in FIG. 21, which does not use a lead frame, is quite useful in reducing the overall thickness of the optical coupling device. However, in this structure, it is difficult to solder the wiring patterns  2104 A and  2104 B to the insulative substrates  2106 A and  2106 B, respectively, thereby complicating the production process. Moreover, the devices  1  and  2  are mounted in the substantially U-shaped insulative substrates  2106 A and  2106 B, respectively, which makes the die-bonding or wire-bonding process more difficult. 
     The conventional example illustrated in FIG. 22 is also quite useful in reducing the overall thickness of the optical coupling device. However, it is necessary to make an electrical connection between the wiring pattern  2204 C of the upper, plate-like insulative substrate  2206 B and the wiring pattern  2204 Bon the lower, substantially U-shaped insulative substrate  2206 A, thereby complicating the production process. Moreover, since the devices are mounted in the lower, substantially U-shaped insulative substrate  2206 A, which makes the die-bonding or wire-bonding process more difficult. 
     SUMMARY OF THE INVENTION 
     According to one aspect of this invention, there is provided an optical coupling device, including: a light emitting device for converting an electric signal into an optical signal and outputting the optical signal; and a light receiving device for receiving the optical signal output from the light emitting device and converting the optical signal into the electric signal, wherein: the light emitting device has a light emitting surface for outputting the optical signal; the light receiving device has a light receiving surface for receiving the optical signal; and the light emitting device and the light receiving device are arranged so that the light emitting surface and the light receiving surface oppose each other, the optical coupling device further including: a first insulative substrate on which the light emitting device is mounted; and a second insulative substrate on which the light receiving device is mounted, wherein: the first insulative substrate has a first cross section; and the second insulative substrate has a second cross section; and at least one of the first cross section and the second cross section is substantially L-shaped. 
     In one embodiment of the invention, the first insulative substrate has a wiring pattern connected to the light emitting device; and the wiring pattern includes a soldering terminal section. 
     In one embodiment of the invention, the light emitting device is connected to the wiring pattern by way of wire bonding. 
     In one embodiment of the invention, the second insulative substrate has a wiring pattern connected to the light receiving device; and the wiring pattern includes a soldering terminal section. 
     In one embodiment of the invention, the light receiving device is connected to the wiring pattern by way of wire bonding. 
     In one embodiment of the invention, the soldering terminal section is provided on an opposite side from a leg of the substantially L-shaped cross section with respect to the light receiving device. 
     In one embodiment of the invention, the first insulative substrate and the second insulative substrate are molded together with a light blocking resin. 
     In one embodiment of the invention, the light blocking resin includes an epoxy resin. 
     In one embodiment of the invention, at least one of the first insulative substrate and the second insulative substrate has a protrusion which is provided along an edge of a device mount surface on which either the light emitting device or the light receiving device is mounted, the protrusion being substantially perpendicular to the device mount surface; and a side surface of the protrusion is in contact with an inner surface of the other insulative substrate. 
     In one embodiment of the invention, the first insulative substrate has a slope portion for reflecting the optical signal output from the light emitting device toward the light receiving device. 
     In one embodiment of the invention, the optical signal which has been emitted toward a side surface of the light emitting device is reflected by the slope portion toward the light receiving device. 
     In one embodiment of the invention, the first insulative substrate has a through hole; the first insulative substrate has a wiring pattern connected to the light emitting device; and the wiring pattern extends from an inner surface of the first insulative substrate via the through hole to an outer surface of the first insulative substrate. 
     In one embodiment of the invention, the second insulative substrate has a through hole: the second insulative substrate has a wiring pattern connected to the light receiving device; and the wiring pattern extends from an inner surface of the second insulative substrate via the through hole to an outer surface of the second insulative substrate. 
     In one embodiment of the invention, the optical coupling device further includes a light transmissive resin filled the first insulative substrate and the second insulative substrate. 
     In one embodiment of the invention, the light transmissive resin includes a silicone resin. 
     The present invention provides an opposed-type optical coupling device which employs an insulative substrate having a wiring pattern provided by plating, or the like, as a substrate on which a light emitting device and a light receiving device are mounted. In this way, it is possible to eliminate the need to use thick lead frames, thereby significantly reducing the overall thickness of the device. Moreover, the substantially L-shaped cross section of the insulative substrate facilitates the die-bonding or wire-bonding process as compared with the case where a substantially U-shaped insulative substrate as in the prior art. 
     Moreover, the light emitting device side insulative substrate can be provided with a light emitting side soldering terminal section (electrode), and the light receiving device side insulative substrate can be provided with a light receiving side soldering terminal section (electrode). Therefore, it is possible to eliminate the need to connect the wiring pattern on the upper substrate to the wiring pattern on the lower substrate, as in the prior art, thereby significantly improving the productivity. 
     The light emitting device side insulative substrate and the light receiving device side insulative substrate can be molded together with a light blocking resin. Particularly, when the junction between the light emitting device and the light receiving device has a complicated configuration, the resin molding improves the productivity. Using an adhesive can further stabilize the product quality. 
     Furthermore, a protrusion may be provided at the tip of the device mount surface of a substantially L-shaped structure of one insulative substrate, so that the protrusion extends in a direction substantially perpendicular to the device mount surface and that a side surface of the protrusion is in contact with an inner side surface of the other insulative substrate. In this way, it is possible to increase the creepage distance along the boundary between the periphery of the light transmissive resin structure and the inner surface of the insulative substrates, thereby increasing the withstand voltage of the optical coupling device. This is because when a high voltage is applied between the light emitting side and the light receiving side, a discharge, if any, would occur in a location where the withstand voltage is lowest, and such a location (within the optical coupling device itself excluding the ambient space) corresponds to the boundary between the periphery of the light blocking resin structure and the inner surface of the insulative substrates. 
     The leg (herein, the term “leg” is used to refer to the shorter one of the two linear segments of the substantially L-shaped configuration) of the substantially L-shaped cross section of the lower insulative substrate may be provided opposite from the soldering terminal section with respect to the device. In this way, it is possible to increase the creepage distance along the boundary between the periphery of the light transmissive resin structure and the inner surface of the insulative substrates, thereby increasing the withstand voltage of the optical coupling device. 
     The light receiving device side insulative substrate may be provided with a slope portion so that the optical signal which has been emitted toward a side surface of the light emitting device is reflected by the slope portion toward the light receiving device. In this way, it is possible to significantly improve the optical transmission efficiency. 
     Moreover, the insulative substrate may be provided with a through hole so that the wiring pattern can extend from the inner surface of the insulative substrate through the through hole to the outside of the optical coupling device. In this way, it is possible to increase the creepage distance along the boundary between the periphery of the light transmissive resin structure and the inner surface of the insulative substrates, i.e., the distance along such a boundary between the electrically active portion on the light emitting side and the electrically active portion on the light receiving side. Herein, the term “electrically active portion” is used to mean any portion of the light emitting side or the light receiving side which is electrically connected to the terminal of the light emitting side or the light receiving side, respectively. In the present specification, the term “electrically active portion” is used to refer to the wiring pattern itself. 
     Thus, the invention described herein makes possible the advantages of: (1) providing an optical coupling device capable which can be produced with a reduced thickness and an improved productivity, and in which the optical transmission efficiency can be improved. 
     These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view illustrating a structure of an optical coupling device according to Embodiment 1 of the present invention; 
     FIGS. 2A to  2 H illustrates a method for producing the optical coupling device according to Embodiment 1 of the present invention; 
     FIG. 3 is a cross-sectional view illustrating a structure of an optical coupling device according to Embodiment 2 of the present invention; 
     FIG. 4 is a cross-sectional view illustrating a structure of an optical coupling device according to Embodiment 3 of the present invention; 
     FIG. 5 is a cross-sectional view illustrating a structure of an optical coupling device according to Embodiment 4 of the present invention: 
     FIG. 6 is a cross-sectional view illustrating a structure of another optical coupling device according to Embodiment 4 of the present invention; 
     FIG. 7 is a cross-sectional view illustrating a structure of still another optical coupling device according to Embodiment 4 of the present invention; 
     FIG. 8 is a cross-sectional view illustrating a structure of an optical coupling device according to Embodiment 5 of the present invention; 
     FIG. 9 is a cross-sectional view illustrating a structure of another optical coupling device according to Embodiment 5 of the present invention; 
     FIG. 10 is a cross-sectional view illustrating a structure of still another optical coupling device according to Embodiment 5 of the present invention; 
     FIG. 11 is a cross-sectional view illustrating a structure of still another optical coupling device according to Embodiment 5 of the present invention; 
     FIG. 12 is a cross-sectional view illustrating a structure of still another optical coupling device according to Embodiment 5 of the present invention; 
     FIG. 13 is a cross-sectional view illustrating a structure of still another optical coupling device according to Embodiment 5 of the present invention; 
     FIG. 14 is a cross-sectional view illustrating a structure of an optical coupling device according to Embodiment 6 of the present invention; 
     FIG. 15 is a cross-sectional view illustrating a structure of another optical coupling device according to Embodiment 6 of the present invention: 
     FIG. 16 is a cross-sectional view illustrating a structure of still another optical coupling device according to Embodiment 6 of the present invention; 
     FIG. 17 is a cross-sectional view illustrating a structure of still another optical coupling device according to Embodiment 6 of the present invention: 
     FIG. 18 is a cross-sectional view illustrating a structure of still another optical coupling device according to Embodiment 6 of the present invention; 
     FIG. 19 is a cross-sectional view illustrating a structure of still another optical coupling device according to Embodiment 6 of the present invention; 
     FIG. 20 is a cross-sectional view illustrating a structure of a conventional optical coupling device; 
     FIG. 21 is a cross-sectional view illustrating a structure of another conventional optical coupling device; and 
     FIG. 22 is a cross-sectional view illustrating a structure of still another conventional optical coupling device. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Various embodiments of the present invention will now described with reference to the accompanying drawings. 
     Embodiment 1 
     FIG. 1 is a cross-sectional view illustrating the general structure of an opposed-type optical coupling device  100  according to Embodiment 1 of the present invention. The optical coupling device  100  includes insulative substrates  6 A and  6 B each having a substantially L-shaped cross section. A light emitting device  1  and a light receiving device  2  are mounted on the insulative substrates  6 A and  6 B, respectively. The light emitting device  1  and the light receiving device  2  are wire-bonded via a gold wire  3  to respective wiring patterns  4 A and  4 B which are provided by plating, or the like. The insulative substrates  6 A and  6 B are attached together so that the devices  1  and  2  oppose each other. The inner gap between the insulative substrates  6 A and  6 B is filled with a light transmissive resin  5  which may be a silicone resin or an epoxy resin. 
     The optical coupling device  100  may be produced as follows, for example. First, a light receiving side insulative substrate  206 B including a number of light receiving devices  2  mounted thereon (die-bonding or wire-bonding of the light receiving devices  2  has been completed), as illustrated in the perspective view of FIG. 2A, and a light emitting side insulative substrate  206 A including a number of light emitting devices  1  mounted thereon (die-bonding or wire-bonding of the light emitting devices  1  has been completed), as illustrated in the perspective view of FIG. 2B, are provided. The insulative substrates  206 A and  206 B are attached together as illustrated in the perspective view of FIG.  2 C. The light emitting side insulative substrate  206 A has a hole  201  therein for resin injection at a position in the approximate middle between two adjacent optical coupling devices. A transparent resin is injected into the gap between the insulative substrates  206 A and  206 B through the hole  201 , as illustrated in the cross-sectional view of FIG.  2 D. Then, using a disc-shaped cutter  202 , as illustrated in the perspective view of FIG. 2E, half cuts  203  are made in the obtained structure along the boundary between each pair of adjacent optical coupling devices so as to leave the lower substrate uncut, as illustrated in the cross-sectional view of FIG.  2 F. During the cutting process, the resin injection hole  201  is cut away. Then, the obtained half cuts  203  are filled with a light blocking resin  204 , as illustrated in the cross-sectional view of FIG. 2G, and the light blocking resin  204  is allowed to cure. Then, a disc-shaped cutter is used to sever the obtained structure into individual optical coupling devices, as illustrated in the cross-sectional view of FIG.  2 H. Thus, the optical coupling device  100  is produced. 
     Since the optical coupling device  100  of the present embodiment which is obtained as described above employs the insulative substrates  6 A and  6 B which are provided with the wiring patterns  4 A and  4 B, respectively, there is no need to use thick lead frames. Thus, it is possible to significantly reduce the overall thickness of the optical coupling device  100  to be about 1.4 mm. Moreover, each of the insulative substrates  6 A and  6 B has a substantially L-shaped cross section, thereby facilitating the process of die-bonding or wire-bonding the light emitting device  1  and the light receiving device  2 . Moreover, each of the insulative substrate  6 A for the light emitting device  1  and the insulative substrate  6 B for the light receiving device  2  can be provided with a soldering terminal section  4 C, thereby eliminating the need to connect the wiring pattern on the upper substrate to the wiring pattern of the lower substrate as in the conventional examples illustrated in FIGS. 21 and 22, thereby facilitating the manufacturing process. 
     Alternatively, only one of the light emitting device  1  and the light receiving device  2  may have a substantially L-shaped cross section. 
     Embodiment 2 
     FIG. 3 is a cross-sectional view illustrating the general structure of an opposed-type optical coupling device  300  according to Embodiment 2 of the present invention. In FIG. 3, those elements which are also included in the optical coupling device  100  and shown in FIG. 1 are provided with the same reference numerals, and will not be further described below. The optical coupling device  300  has a structure similar to that of the optical coupling device  100  illustrated in FIG. 1 except that slope sections  36 C are provided in a substantially L-shaped insulative substrate  36 A for the light emitting device  1 . 
     The optical signal which has been emitted from a junction plane  1 A of the light emitting device  1  toward side surfaces of the light emitting device  300  is reflected by the slope sections  36 C toward the light receiving device  2  so as to be received by the light receiving device  2 . Thus, the optical transmission efficiency can be significantly improved. 
     Embodiment 3 
     FIG. 4 is a cross-sectional view illustrating the general structure of an opposed-type optical coupling device  400  according to Embodiment 3 of the present invention. In FIG. 4, those elements which are also included in the optical coupling device  100  and shown in FIG. 1 are provided with the same reference numerals, and will not be further described below. The optical coupling device  400  has a structure similar to that of the optical coupling device  100  illustrated in FIG. 1 except that through holes  46 C and  46 D are provided in the substantially L-shaped insulative substrates  46 A and  46 B, respectively, and that wiring patterns  44 A and  44 B extend respectively from the inner surface of the insulative substrates  46 A and  46 B through the through holes  46 C and  46 D to the outside of the optical coupling device  400 . 
     In this way, the wiring patterns  44 A and  44 B can be extended along the outer surface of the insulative substrates  46 A and  46 B, respectively. Thus, it is possible to increase the creepage distance along the boundary between the periphery of the light transmissive resin structure  5  and the inner surface of the insulative substrates, i.e., the distance along such a boundary between the electrically active portion on the light emitting side and the electrically active portion on the light receiving side, thereby significantly improving the withstand voltage. 
     Alternatively, only one of the light emitting device side and the light receiving device side may be provided with such a through hole. 
     Embodiment 4 
     FIG. 5 is a cross-sectional view illustrating the general structure of an opposed-type optical coupling device  500  according to Embodiment 4 of the present invention. In FIG. 5, those elements which are also included in the optical coupling device  100  and shown in FIG. 1 are provided with the same reference numerals, and will not be further described below. The optical coupling device  500  has a structure similar to that of the optical coupling device  100  illustrated in FIG. 1 except that substantially L-shaped insulative substrates  56 A and  56 B on which the light emitting device  1  and the light receiving device  2  are mounted, respectively, are molded together with a light blocking resin  7  such as an epoxy resin. 
     In this way, the light emitting side and the light receiving side can be attached together without using an adhesive. 
     As a variation of the present embodiment, FIG. 6 illustrates an optical coupling device  600  in which an insulative substrate  66 A is provided with a slope section  66 C so that the optical signal which has been emitted from the junction plane  1 A of the light emitting device  1  toward side surfaces of the light emitting device  600  can be reflected by the slope section  66 C toward the light receiving device  2  so as to be received by the light receiving device  2 . 
     As another variation of the present embodiment, FIG. 7 illustrates an optical coupling device  700  in which insulative substrates  76 A and  76 B are provided with through holes  76 C and  76 D, respectively, so that wiring patterns  74 A and  74 B can extend respectively from the inner surface of the insulative substrates  76 A and  76 B through the through holes  76 C and  76 D to the outside of the optical coupling device  700 . 
     Embodiment 5 
     FIG. 8 is a cross-sectional view illustrating the general structure of an opposed-type optical coupling device  800  according to Embodiment 5 of the present invention. In FIG. 8, those elements which are also included in the optical coupling device  100  and shown in FIG. 1 are provided with the same reference numerals, and will not be further described below. The optical coupling device  800  has a structure similar to that of the optical coupling device  100  illustrated in FIG. 1 except that protrusions  86 C and  86 D are provided respectively at the tip of the device mount surfaces of the substantially L-shaped insulative substrates  86 A or  86 B. The protrusions  86 C and  86 D extend in respective directions substantially perpendicular to the device mount surfaces, and each of side surfaces  86 E and  86 F of the protrusions  86 C and  86 D of the insulative substrates  86 A and  86 B, respectively, is in contact with an inner side surface  86 G or  86 H of the other insulative substrate  86 B or  86 A via the wiring pattern  4 B or  4 A, respectively. 
     In this way, it is possible to increase the creepage distance along the boundary between the periphery of the light transmissive resin structure  5  and the inner surface of the insulative substrates  86 A and  86 B, thereby significantly increasing the withstand voltage of the optical coupling device  800 . 
     Alternatively, only one of the light emitting device side and the light receiving device side may be provided with such a protrusion. 
     As variations of the present embodiment, FIGS. 9 and 12 illustrate optical coupling devices  900  and  1200  in which insulative substrates  96 A and  126 A are provided with slope sections  96 B and  126 B, respectively, so that the optical signal which has been emitted from the junction plane  1 A of the light emitting device  1  toward side surfaces of the light emitting devices  900  and  1200  can be reflected by the slope section  96 B and  126 B, respectively, toward the light receiving device  2  so as to be received by the light receiving device  2 . 
     As further variations of the present embodiment, FIGS. 10 and 13 illustrate optical coupling devices  1000  and  1300  in which insulative substrates  106 A and  106 B, and  136 A and  136 B are provided with through holes  106 C and  106 D, and  136 C and  136 D, respectively, so that wiring patterns  104 A and  104 B, and  134 A and  134 B can extend respectively from the inner surface of the insulative substrates  106 A and  106 B, and  136 A and  136 B through the through holes  106 C and  106 D, and  136 C and  136 D to the outside of the optical coupling devices  1000  and  1300 , respectively. 
     As still other variations of the present embodiment, FIGS. 11,  12  and  13  respectively illustrate optical coupling devices  1100 ,  1200  and  1300  in which substantially L-shaped insulative substrates  86 A and  86 B,  126 A and  126 C, and  136 A and  136 B are respectively molded together with the light blocking resin  7 . 
     Embodiment 6 
     FIG. 14 is a cross-sectional view illustrating the general structure of an opposed-type optical coupling device  1400  according to Embodiment 6 of the present invention. In FIG. 14, those elements which are also included in the optical coupling device  100  and shown in FIG. 1 are provided with the same reference numerals, and will not be further described below. The optical coupling device  1400  has a structure similar to that of the optical coupling device  100  illustrated in FIG. 1 except that a leg  146 D of the substantially L-shaped cross section of a lower insulative substrate  146 B is provided opposite from a soldering terminal section  144 B with respect to the light receiving device  2 . 
     In this way, it is possible to increase the creepage distance along the boundary between the periphery of the light transmissive resin structure  5  and the inner surface of the insulative substrates  146 A and  146 B, thereby improving the withstand voltage of the optical coupling device  1400 . 
     As variations of the present embodiment, FIGS. 15 and 18 illustrate optical coupling devices  1500  and  1800  in which insulative substrates  166 A and  186 A are provided with slope sections  166 C and  186 C, respectively, so that the optical signal which has been emitted from the junction plane  1 A of the light emitting device  1  toward side surfaces of the light emitting devices  1500  and  1800  can be reflected by the slope section  166 C and  186 C, respectively, toward the light receiving device  2  so as to be received by the light receiving device  2 . 
     As further variations of the present embodiment, FIGS. 16 and 19 illustrate optical coupling devices  1600  and  1900  in which insulative substrates  166 A and  196 A are provided with through holes  166 B and  196 B, respectively, so that wiring patterns  164 A and  194 A can extend respectively from the inner surface of the insulative substrates  166 A and  196 A through the through holes  166 B and  196 B to the outside of the optical coupling devices  1600  and  1900 , respectively. 
     As other variations of the present embodiment, FIGS. 17,  18  and  19  illustrate optical coupling devices  1700 ,  1800  and  1900  in which substantially L-shaped insulative substrates  176 A and  146 B,  186 A and  146 B, and  196 A and  146 B are respectively molded together with the light blocking resin  7 . 
     In Embodiments 1-6 described above, the light emitting device  1  is mounted on the upper insulative substrate while the light receiving device  2  is mounted on the lower insulative substrate. Alternatively, the light emitting device  1  may be mounted on the lower insulative substrate while the light receiving device  2  may be mounted on the upper insulative substrate. 
     As described above in detail, the present invention employs a substantially L-shaped cross section for an insulative substrate of an optical coupling device. In this way, it is possible to provide a low-cost opposed-type optical coupling device, while significantly reducing the overall thickness of the optical coupling device, facilitating the die-bonding or wire-bonding process, and improving the optical transmission efficiency or the withstand voltage of the optical coupling device. 
     Various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of this invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but rather that the claims be broadly construed.