JP5253083B2 - OPTICAL TRANSMISSION BOARD, OPTICAL MODULE, AND OPTICAL TRANSMISSION BOARD MANUFACTURING METHOD - Google Patents

Description

  The present invention relates to an optical transmission board for transmitting an optical signal, an optical module including the same, and a method for manufacturing the optical transmission board.

  In recent years, with the improvement of information processing capability of computers, in an integrated circuit (IC) such as a semiconductor large scale integrated circuit element (LSI, VLSI) used as a microprocessor, the degree of integration of transistors has been increased. The operating speed of the IC has reached the GHz level at the clock frequency. Accordingly, there is a demand for higher density and finer electrical wiring that electrically connects electrical elements.

  However, conventional wiring boards such as printed wiring boards, which have been the mainstream in the past, and that transmit signals only with electrical wiring, have the problem that electrical signal crosstalk and propagation loss are likely to occur. It is said that the limit of miniaturization is approaching, and as an alternative to this, an optical transmission board in which optical wiring is formed in addition to electric wiring is widely known.

  The optical transmission board performs signal exchange between semiconductor elements mounted on the optical transmission board by transmitting an optical signal to an optical wiring such as an optical waveguide formed on a surface layer or an inner layer. In addition to semiconductor elements, photoelectric conversion elements that convert electrical signals into optical signals or optical signals into electrical signals are mounted near the semiconductor elements on the optical transmission board. The signal is converted at.

  In such an optical transmission board, not only light is transmitted substantially parallel to the board, such as an optical waveguide formed on the surface of a circuit board, but for example, light is also transmitted in the thickness direction of the board. By doing so, an optical transmission technique for performing three-dimensional transmission of an optical signal as well as an electrical signal is known. A large number of such optical wirings are usually provided, and these optical wirings are connected at the same time at the connecting portion of the optical wiring.

For example, in Patent Document 1, a package substrate (corresponding to an optical transmission substrate) is mounted on a motherboard substrate, an optical semiconductor element mounted on the package substrate, and an optical waveguide W formed on the motherboard substrate. The optical transmission line V that penetrates the front and back surfaces of the package substrate and the optical path conversion body that optically converts the light emitted from the optical waveguide W formed on the mother board and couples it to the optical transmission path V, and the optical transmission path. A conventional example of an optical transmission board and an optical module using the same including a microlens provided at an end of V is disclosed (an assembly of a mother board, a package board, and an optical semiconductor element corresponds to the optical module) ).
JP 2006-019526 A

  However, in the conventional optical transmission substrate as disclosed in Patent Document 1, since a laminated substrate such as a build-up method is preferably used industrially, in order to provide an optical transmission path in the substrate thickness direction, After providing a through hole in the substrate by post-processing, a light guide part that becomes an optical transmission path will be inserted into the through hole, but in the production of such an optical transmission path in the thickness direction of the laminated substrate, Since the accuracy of post-processing tends not to be practically high compared to the optically required accuracy, the arrangement of optical transmission lines is likely to vary among multiple optical signals. Since it is difficult to make the intensity uniform, there is a problem that the optical transmission quality tends to become unstable.

  That is, the conventional optical transmission board as disclosed in Patent Document 1 is good when a plurality of optical connections are made between a package board having a plurality of optical transmission paths formed in the board thickness direction and the motherboard board. Since it is difficult to make a reliable optical connection, there is a problem that it is difficult to ensure stable optical transmission quality.

  The present invention has been devised to solve the above-described problems in the prior art, and the object is to provide a good optical connection in the thickness direction of the substrate with a simple configuration, and a plurality of optical transmissions. An object of the present invention is to provide an optical transmission board having uniform and good optical transmission quality on the road, an optical module using the same, and a method for manufacturing the optical transmission board.

An optical transmission board according to the present invention includes a substrate having a first through hole group in which through holes penetrating the front and back surfaces are provided in a row, and an electric wiring formed on a surface layer or an inner layer, and either of the front and back surfaces Or a second through hole group in which either of the upper and lower surfaces are joined to each other, and through holes penetrating the upper and lower surfaces are provided in a row, each extending part of the first through hole group; A light guide unit having a second through hole group that is narrower than the first through hole group, and continuously provided in each of the first through hole group and the second through hole group; A plurality of optical waveguides made of a photosensitive material .

  In the optical transmission board of the present invention, the board is a build-up wiring board, and the light guide unit has a smaller volume than the build-up wiring board.

  In the optical transmission board according to the present invention, in each of the above configurations, the optical waveguide is provided around a core portion and the core portion, and the first cladding portion of the optical waveguide having a lower refractive index than the core portion. And a second clad portion that fills the gap between the light guide portion and the substrate near the optical waveguide.

  Moreover, the optical transmission board | substrate of this invention further contains the guide hole provided in the surface opposite to the said joint surface of the said light guide part in said each structure.

  The optical module of the present invention is provided at any one of the above-described optical transmission boards, other optical waveguides formed on a surface layer or an inner layer, and end portions of the other optical waveguides, Another optical transmission board having an optical path changer coupled to one end of the optical waveguide of the optical transmission board, and an optical semiconductor element coupled to the other end of the optical waveguide of the optical transmission board.

  The method for manufacturing an optical transmission board according to the present invention includes a step A for forming a first through hole group in which through holes penetrating the front and back surfaces are formed in a row on a substrate having an electrical wiring formed on a surface layer or an inner layer; A second through hole group in which through holes penetrating the upper and lower surfaces are provided in a row is formed in advance with the second through hole group of the light guide section and the second through hole group having a smaller diameter than the first through hole group. The first light-transmitting portion group is aligned so that the end portions overlap each other, and the light guide portion is bonded to the substrate on which the first through-hole group is formed, and the light guide portion is bonded. A step C of injecting a clad member to be a clad portion of an optical waveguide into the first through hole group and the second through hole group of the substrate; the first through hole group into which the clad member is injected; A third through hole group having a diameter smaller than that of the cladding portion is provided at the center of the two through hole group. , And a step D of injecting a core member comprising a core portion of the optical waveguide to the third through-hole group.

  According to the optical transmission board of the present invention, the first through-hole group and the second through-hole group that is an extended portion of each of the first through-hole groups and each of which is narrower than the first through-hole group. Therefore, even if the position accuracy of each through hole of the first through hole group provided in the substrate is lower than the position accuracy of each through hole of the second through hole group provided in the light guide portion, the first through hole The hole diameter of each through-hole of the group is larger than the hole diameter of each corresponding through-hole of the second through-hole group, so that errors in positional accuracy are absorbed and each hole constitutes a continuous through-hole. When the optical waveguide that transmits in the thickness direction of the substrate is extended from the front surface or the back surface of the substrate and coupled to the optical waveguide of another optical transmission substrate, the optical waveguide on the substrate side and the extension portion Connection loss due to alignment errors with the optical waveguide on the light guide side It is possible to average small between several, substrate thickness direction can be a good optical connection, the optical transmission quality of a plurality of optical transmission paths are uniform and favorable ones with a simple configuration.

  According to the optical transmission board of the present invention, the board is a build-up wiring board, and the build-up wiring board has a hole in the board thickness direction when the light guide portion has a smaller volume than the build-up wiring board. Misalignment errors are likely to occur because the processing accuracy is lower than the planar processing accuracy, but the light guide unit works to mitigate and improve the error by interposing the light guide unit, and also guides light more than the substrate. By reducing the size of the part, it is possible to efficiently mass-produce what has been precisely processed by injection molding or the like, and therefore, it is possible to efficiently mass-produce those having good optical transmission quality as a whole.

  According to the optical transmission board of the present invention, the optical waveguide has a core portion and a first cladding portion of the optical waveguide provided around the core portion and having a refractive index lower than that of the core portion. When the second clad portion that fills the gap between the substrate near the optical waveguide and the light guide portion is further included, the second through hole group provided in the light guide portion serves as an accurate template. Since the core portions are provided in the center of them, the precise arrangement of the core portions makes the optical connection loss absolutely small and uniform among a plurality of them. In addition, even if the substrate is slightly warped or otherwise deformed, the clad member fills the gap formed between the light guide unit and the substrate, so that light leakage from the optical waveguide can be eliminated, and temperature fluctuations can be avoided. Even if there is, it works to suppress structural deformation, so the quality becomes more stable.

  Further, when the optical transmission board of the present invention further includes a guide hole provided on the opposite surface of the joint surface of the light guide unit, the optical transmission board is mounted on another optical transmission board, and the other optical transmission board is provided. Since it functions as a guide hole when optically coupling with other optical waveguides, it is possible to make a good optical connection in the substrate thickness direction with a simple configuration when transmitting light to another optical transmission substrate. The optical transmission quality in the plurality of optical transmission lines is uniform and good.

  The optical module of the present invention is provided at any one of the above-described optical transmission boards, other optical waveguides formed on a surface layer or an inner layer, and end portions of the other optical waveguides, Since it includes another optical transmission substrate having an optical path changer coupled to one end of the optical waveguide of the optical transmission substrate, and an optical semiconductor element coupled to the other end of the optical waveguide of the optical transmission substrate, the light guide The optical waveguide provided in the section functions as an optical waveguide of the extension that connects the optical transmission board to other optical transmission boards, and the optical transmission quality in these multiple optical waveguides is uniform and good, so it is almost in the thickness direction of the board. It is possible to provide an optical confinement structure for optically connecting a plurality of optical transmission boards arranged in parallel with a simple mounting process, and to improve the optical transmission quality between the plurality of optical transmission boards. Can be

  In the optical module of the present invention, when the metal film is formed on the other optical transmission board in a region surrounding the optical path changer, the metal film is mounted when the optical transmission board is mounted on the other optical transmission board. However, since it functions as a marker with good visibility, it can be easily mounted while optically connecting these optical transmission boards.

  The method for manufacturing an optical transmission board according to the present invention includes a step A for forming a first through hole group, and a light guide unit in which the second through hole group is formed in advance with a smaller hole diameter than the first through hole group. Aligning the second through-hole group and the first through-hole group so as to overlap each other, and joining the light guide unit to the substrate on which the first through-hole group is formed; A step C of injecting a clad member to be a clad portion of the optical waveguide into the first through hole group and the second through hole group of the substrate to which the light guide unit is bonded; and the clad member is injected. A third through hole group having a diameter smaller than that of the clad portion is provided at the center of the first through hole group and the second through hole group, and a core member serving as a core portion of the optical waveguide is injected into the third through hole group. Step D is included, so that the light is guided on the basis of the second through hole group in which the holes are precisely formed. Since the clad portion and the core portion of the path are formed, the optical waveguide that penetrates the substrate and the light guide portion can be manufactured with relatively high accuracy even if the positional accuracy of the holes of the first through hole group is low. Thus, it is possible to provide a process that can be stably manufactured with relatively high accuracy by a simple process as a whole without complicating the manufacturing process.

  The optical transmission board of the present invention will be described below with reference to the drawings.

  FIG. 1 is a partial cross-sectional view showing an example of an embodiment of a package substrate as an optical transmission substrate of the present invention. 2 is a cross-sectional view showing a region including a plurality of optical waveguides in the package substrate shown in FIG. FIG. 3 is a perspective view showing an example of an embodiment of the optical module of the present invention, where (a) is an overall perspective view of the optical module, and (b) is a package substrate constituting the optical module, and other optical transmissions. The perspective view which shows a mode before mounting on the board board | substrate which is a board | substrate, (c) is an expansion perspective view which shows a mode when a package board | substrate is mounted on a board board | substrate. FIG. 4 is an enlarged perspective view showing a package substrate having fitting pins. FIG. 5 is an enlarged perspective view showing the light guide.

  1 to 5, 1 is a substrate, 11 is a front surface, 12 is a back surface, 13 is a first through hole group, 2 is an optical waveguide, 21 is a core portion, 22 is a first cladding portion, and 23 is a second cladding. , 24 is another optical waveguide, 3 is a protruding portion, 31 is an optical path, 32 is a cladding portion of the protruding portion, 33 is an edge portion, 4 is a light guide portion, 41 is an upper surface, 42 is a lower surface, and 43 is a second Through hole group, 5 is electrical wiring, 6 is a package substrate as an optical transmission substrate, 7 is an optical semiconductor element, 8 is a joint portion, 9 is a board substrate as another optical transmission substrate, 10 is an optical path changer, M Is an optical module.

  An example of an embodiment of a package substrate 6 as an optical transmission substrate of the present invention shown in cross-sectional views in FIGS. 1 and 2 is a first through hole in which through holes penetrating from the front surface 11 to the back surface 12 are provided in a row. A substrate 1 having a group 13 and an electric wiring 5 formed on a surface layer or an inner layer (surface layer in this example), and a second through hole group 43 in which through holes penetrating from the upper surface 41 to the lower surface 42 are provided in a row. The second through-hole groups 43 that are the extended portions of the first through-hole group 13 and have the widths d1, d2, and d3 narrower than the respective widths w1, w2, and w3 of the first through-hole group 13 are The light guide part 4 to which either the upper surface 41 or the lower surface 42 is joined to either or both of the front surface 11 and the rear surface 12, and the first through-hole group 13 and the second through-hole group 43. Multiple rows of optical waveguides 2 It is configured to include a. Note that the width of the through hole refers to the diameter of the circle when the through hole is cylindrical, for example.

  The package substrate 6 shown in FIGS. 1 and 2 has a preferred configuration in which the substrate 1 is a build-up wiring substrate and the light guide portion 4 is smaller than the substrate 1. The build-up wiring board is composed of a laminate composed of a plurality of layers, and an electric circuit pattern is printed on a surface layer or an inner layer, and each layer is electrically connected by a through-hole conductor at a necessary portion (not shown). The optical waveguide 2 includes a core portion 21 and a cladding portion 22 of the optical waveguide 2 that is provided around the core portion 21 and has a refractive index lower than that of the core portion 21. The clad part 23 which fills the gap with the light guide part 4 is further included. A guide hole (not shown in FIGS. 1 and 2) is provided on the opposite surface (the lower surface 42 in this example) of the light guide 4. In the substrate 1, the protruding portion 3 is provided on the surface 11 opposite to the surface to which the light guide portion 4 is joined, that is, the surface 11, and the optical waveguide 2 is also formed on the protruding portion 3.

  The manufacturing method of the package substrate 6 shown in FIGS. 1 and 2 may be as follows.

  In the first step A, the first through-hole group 13 is formed in the substrate 1 having the electrical wiring 5 formed on the surface layer, and through-holes penetrating from the front surface 11 to the back surface 12 are provided in a row.

  In the next step B, the second through hole group 43 in which through holes penetrating from the upper surface 41 to the lower surface 42 are provided in a row is formed in advance with a hole diameter having a smaller volume than the first through hole group 13. The second through-hole group 43 and the first through-hole group 13 are aligned so that the end portions overlap each other, and the light guide unit 4 is joined to the substrate 1 on which the first through-hole group 13 is formed.

  In the next step C, a clad member to be the clad part 22 of the optical waveguide 2 is injected into the first through hole group 13 and the second through hole group 43 of the substrate 1 to which the light guide part 4 is bonded, and cured.

  In the next step D, a third through hole group having a diameter smaller than that of the clad portion 22 is provided at the center of the first through hole group 13 and the second through hole group 43 into which the clad member has been injected. A core member to be the core portion 21 of the optical waveguide 2 is injected and cured.

  Since the package substrate 6 shown in FIGS. 1 and 2 has the above-described configuration, the package substrate 6 is provided on the substrate 1 in comparison with the positional accuracy of each through hole of the second through hole group 43 provided in the light guide unit 4. Even if the position accuracy of each through hole of the first through hole group 13 is low, the hole diameters w1, w2, and w3 of each through hole of the first through hole group 13 are the hole diameters of the corresponding through holes of the second through hole group 43. Since it is larger than d1, d2, and d3, it absorbs errors in positional accuracy and acts so that each hole constitutes a continuous through hole. In the case where the waveguide 2 is extended from the substrate front surface 11 or the substrate back surface 12 and coupled to the optical waveguide of another optical transmission substrate (board substrate 9 in FIG. 3), the optical waveguide 2 on the substrate 1 side and the light guide that is an extension portion. Due to an alignment error with the optical waveguide 2 on the side of the section 4 Since the connection loss can be reduced on average among a plurality of units, a good optical connection can be made in the thickness direction of the substrate 1 with a simple configuration, and the optical transmission quality in the plurality of optical transmission lines is uniform and good. It will be a thing.

  In addition, since the build-up wiring board has a lower hole processing accuracy in the substrate thickness direction than the planar processing accuracy, a misalignment error is likely to occur. The light guide 4 can be mass-produced efficiently by means of injection molding or the like by reducing the size of the light guide 4 while reducing the size of the substrate 1, so that the optical transmission quality as a whole is improved. Good products can be mass-produced efficiently.

  In addition, since the second through hole group 43 provided in the light guide part 4 serves as an accurate template and the core part 21 is provided in the center thereof, the core part 21 can be precisely arranged. The optical connection loss is absolutely small and uniform among the plurality. Further, even if the substrate is slightly warped or the like, the gap formed between the light guide portion 4 and the substrate 1 is filled with the clad member and the clad portion 23 is provided, so that light leaks from the optical waveguide 2. In addition, even if there is a temperature fluctuation, it functions to suppress structural deformation, so that the quality becomes more stable.

  Further, the package substrate 6 is mounted on the board substrate 9 (see FIG. 3 and the following description), and functions as a guide hole when optically coupling with the optical waveguide of the board substrate 9. In the case of transmission, a good optical connection can be made in the thickness direction of the substrate 1 with a simple configuration, and the optical transmission quality in the plurality of optical waveguides is uniform and good.

  Moreover, since the clad part 22 and the core part 21 of the optical waveguide 2 are formed on the basis of the second through hole group 43 in which the holes are precisely formed by employing the manufacturing method having the above configuration, the first through hole group Since the optical waveguide 2 penetrating the substrate 1 and the light guide portion 4 can be manufactured with relatively high accuracy even if the position accuracy of the holes 13 is low, the manufacturing process of the substrate 1 is simple as a whole without complicating the manufacturing process. It is possible to provide a process that can be stably manufactured with relatively high accuracy in the process.

  In more detail, the package substrate 6 shown in FIGS. 1 and 2 may be configured as follows.

(Substrate 1)
As the substrate 1, for example, a printed substrate made of a resin material such as ceramics or glass epoxy resin may be used. Especially, it is preferable to use the same resin substrate as the resin that forms the optical waveguide 2 and the protruding portion 3 from the viewpoint of compatibility with the resin that forms the optical waveguide 2 and the protruding portion 3. A substrate having a symmetric layer structure in which a resin insulating layer having the same thickness is formed on both sides is desirable because the substrate can be effectively prevented from warping. The thickness of the substrate 1 can be 0.4 to 2 mm.

  In addition, it is preferable to use a multilayer wiring board as the substrate 1. Here, the multilayer wiring board may be any one in which a plurality of electrical wiring layers and insulating layers are alternately laminated, and includes, for example, a core board and a buildup layer formed on the front and back sides of the wiring board. A substrate is also included. The substrate 1 preferably has a connection portion (for example, an element mounting pad, a solder resist layer, etc.) for electrical connection with the outside. In addition, in the board | substrate 1, the surface 11 of the board | substrate 1 means the side in which the protrusion part 3 is provided, and the back surface 12 of the board | substrate 1 means the main surface on the opposite side to the side in which the protrusion part 3 is provided.

(Optical waveguide 2)
The optical waveguide 2 is provided inside the substrate 1, the projecting portion 3, and the light guide portion 4, and constitutes a portion that transmits light from the front surface 11 to the lower surface 42. The optical waveguide 2 has a circular cross section with respect to the optical transmission direction. In that case, the diameter of the optical waveguide 2 is about 50 to 200 μm.

  The optical waveguide 2 preferably includes a core portion 21 having a high refractive index at the center and a clad portion 22 provided around the core portion 21 and having a refractive index lower than that of the core portion 21. By taking such a structure, a sufficient light confinement effect can be obtained in the optical waveguide 2.

  In addition, the diameter of the core part 21 is about 35-100 micrometers.

  The optical waveguide 2 is formed using polysilane which causes a photo bleaching phenomenon in which the refractive index decreases when irradiated with light, or a photosensitive acrylic resin, epoxy resin, or the like that can be removed by developing the irradiated portion. Can do. For example, when the photo bleaching phenomenon is used, a through hole is provided in the substrate 1, and after filling the through hole with polysilane and heat-curing, a photomask (light shielding of a circular pattern having a smaller diameter than the light transmission hole) is performed. The optical waveguide 2 having the core portion 21 and the clad portion 22 is formed by lowering the refractive index of the ultraviolet light irradiation portion and finally performing post-baking. In this method, in order to obtain the refractive index difference between the core and the clad, it is necessary to divide into an exposed part and an unexposed part. However, if the exposure thickness is thick, the light at the time of exposure spreads, so that a sufficient refractive index difference can be obtained. It becomes difficult.

  When a photosensitive material such as an ultraviolet curable acrylic resin or epoxy resin is used, a through hole is provided in the substrate 1 and then the photosensitive polymer material to be the cladding is filled from the lower surface 42 side of the light guide 4. . An optical semiconductor element can be mounted on the substrate 1 and above the optical waveguide 2. At this time, a solder resist opening (not shown) of the element mounting part is used as a flow-out prevention dam when filling the material. Thus, it is possible to prevent the filling resin from spreading on the substrate in a wide range. Thereafter, a necessary area as the edge portion 33 is exposed using a photomask, and cured by performing pre-baking, developing, and post-baking. After that, a core material having a higher refractive index than that of the initially filled material is filled from the back surface 12 side of the substrate 1 into the portion drilled by a drill, a laser, or the like (the center portion of the light transmission hole). Also in this case, by using a solder resist opening (not shown) of the element mounting portion as a flow-out prevention dam at the time of material filling, it is possible to prevent the filling resin from spreading on the substrate in a wide range. Thereafter, a necessary area is exposed using a photomask and cured by pre-baking / developing / post-baking. When the core material can be filled only in the core portion 21 and the optical transmission hole central portion to be the optical path 31, the above-described mask exposure is not necessary, but it is necessary to fill a very small hole. There is an advantage that it is easy to produce by exposing only a portion. Finally, the surface is polished so as to have a thickness necessary for the protruding portion. As described above, the optical waveguide 2 having the core portion 21 and the cladding portion 22 and the protruding portion 3 having the optical path 31 and the protruding portion cladding 32 can be formed at a time.

  When the optical transmission path is made of an epoxy resin and a glass epoxy substrate is used as the substrate 1 and both are made of an epoxy material (referred to as a polymer material having an epoxy group), the substrate 1 and the optical transmission path are made of epoxy. Since hydrogen bonding is performed between groups, adhesion is good and defects such as peeling are suppressed.

  For the formation of the above-described through holes, a drill, a laser, or the like used in a normal printed circuit board drilling process is preferably used. And a through-hole is formed by letting the board | substrate 1 penetrate from one main surface to the other main surface. The through hole provided in the substrate 1 preferably has a circular cross section, and the diameter is preferably 50 to 200 μm.

(Protrusion 3)
As shown in FIGS. 1 and 2, the protrusion 3 is provided so as to protrude on the substrate 1. The thickness of the protrusion part 3 is 10-100 micrometers.

  Since the protruding portion 3 protrudes from the substrate 1, it has good visibility and serves as a marker when mounting external components. The protruding portion 3 can be formed with high accuracy by a photo process. In this case, the protruding portion 3 also serves as a fitting part and can perform mounting positioning so that highly efficient optical transmission can be performed without alignment. Make it possible. Further, the distance between the optical paths can be shortened at the time of mounting, and the optical loss can be reduced. If the height of the convex part is sufficient, it is possible to connect the optical parts, and even if there is a gap, the thickness when the underfill is performed after mounting the element is thin, so bubbles are involved or foreign matter is mixed in. Can also be prevented.

  The protrusion 3 has an optical path 31. The optical path 31 optically couples the outside of the optical transmission board 6 and the optical waveguide 2. The optical path 31 is made of a transparent resin capable of transmitting light in the same manner as the optical waveguide 2. The material is the same as that of the optical waveguide 2. The optical path 31 refers to a portion having a high refractive index (so-called core portion) in the refractive index distribution of the protruding portion 3. A portion of the protruding portion 3 other than the optical path 31 is a clad portion 32 having a refractive index lower than the refractive index of the optical path 31. In FIGS. 1 and 2, the part other than the optical path 31 is a clad portion 32.

  The diameter of the optical path 31 is about 35 to 100 μm.

  The optical path 31 is provided so as to correspond to the core portion 21 of the optical waveguide 2. Specifically, when the optical transmission board 6 is seen through from above, the optical path 31 and the core portion 21 of the optical waveguide 2 are provided so as to overlap each other. Moreover, it is preferable that the diameter of the optical path 31 and the diameter of the core part 21 are equal.

  The protrusion 3 has an edge 33. The edge portion 33 refers to a portion in contact with the second main surface 12 of the substrate 1 in the protruding portion 3. The edge portion 33 is provided on the substrate 1 by, for example, photolithography. In particular, when an epoxy material (referred to as a polymer material having an epoxy group) is used, such as an epoxy resin as the edge 33 and a glass epoxy substrate as the substrate 1, the substrate 1 and the edge 33 are made of epoxy. Since hydrogen bonding is performed between groups, adhesion is good and defects such as peeling are suppressed. As described above, since the edge 33 is in close contact with the substrate 1, the edge 33 can be used over a long period of time in order to hold the optical transmission path composed of the optical waveguide 2 and the protrusion 3. The optical transmission line is not easily peeled off from the substrate 1, and low-loss optical transmission can be performed over a long period of time.

  The length of the edge 33 is about 1-1000 μm. In addition, the length of the edge part 33 means the length from the boundary between the outer peripheral edge part of the optical waveguide 2 and the second main surface 12 to the end of the edge part 33 (the length of a in FIG. 1).

  Next, an optical module M as an example of an embodiment of the optical module of the present invention shown in FIG. 3 is an optical waveguide 24 formed substantially parallel to the surface layer or the inner layer of the package substrate 6 shown in FIGS. And a board substrate 9 having an optical path changer 10 provided at an end of the optical waveguide 24 and converting the optical path by about 90 degrees and coupled to one end of the optical waveguide 2 of the package substrate 6, and the optical waveguide of the package substrate 6 2 and an optical semiconductor element 7 coupled to the other end.

  In the above configuration, a metal film such as gold (Au) is formed in a region surrounding the optical path changer 10 as a preferable configuration. In addition, when the metal film and the optical path changer are viewed from above, the metal film region is preferably oval. With such a shape, it is possible to reduce the concentration of stress at the corners of the region, so that the metal film is difficult to peel off from the optical path changer 10.

  According to the optical module shown in FIG. 3, the optical waveguide 2 provided in the light guide unit 4 functions as the optical waveguide 2 of the extension part that connects the package substrate 6 to the board substrate 9. Since the optical transmission quality is uniform and good, it is possible to provide an optical confinement structure for optically connecting between the package substrate 6 and the board substrate 9 arranged substantially parallel to the thickness direction of the substrate 1 by a simple mounting process. In addition, the optical transmission quality between the package substrate 6 and the board substrate 9 can be improved.

  Further, when the package substrate 6 is mounted on the board substrate 9, the metal film functions as a marker with good visibility, so that it is easy to mount the package substrate 6 while optically connecting to the board substrate 9. It can be made.

  Therefore, according to the present invention, it is possible to make a good optical connection in the substrate thickness direction with a simple configuration, and an optical transmission board having uniform and good optical transmission quality in a plurality of optical transmission lines, and an optical module using the same In addition, a method for manufacturing an optical transmission board can be provided.

(Production of optical transmission substrate (package substrate 6))
As the substrate 1, CPCore (registered trademark) which is a build-up substrate was used. A wiring pattern for element mounting was formed on the front surface of the substrate 1, and a BGA pattern was formed on the back surface. The element mounting wiring pattern is such that VCSEL and PD can be flip-chiped, and a through hole (first through hole group 13) with a diameter of 250 μm and 12 channels of φ0.15 mm is formed by a drill.

  An MT connector was used as the base material of the light guide unit 4. Cut the tip of the MT connector where no fiber is inserted, and insert it into a 2.4 x 6.3 x 0.35 mm plate-shaped end with a φ0.7 mm positioning fitting hole (guide hole) and this pin The light guide part 4 which is a positioning component having an optical via hole (second through hole group 43) of φ0.125 mm × 12 was produced (see FIG. 5).

  For alignment between the substrate 1 and the light guide unit 4, wires are used to pass through the both ends of the first through hole group 13 and the second through hole group 43, and an adhesive is applied to the substrate 1 and the light guide unit. After curing 4, the wire was pulled out and the substrate 1 and the light guide 4 were bonded together.

The optical waveguide 2 was formed in the first through hole group 13 and the second through hole group 43. First, a UV curable transparent epoxy resin having a refractive index of 1.531 that is clad with a dispenser was filled from the element mounting surface of the substrate 1. In order to expose the electrical wiring for mounting the device in the immediate vicinity of the through hole, exposure and development were performed using a photomask to remove unnecessary resin. Next, a through hole serving as a core was formed from the light guide 4 side to the substrate 1 side using a 3 ^rd -YAG laser. In addition, by forming a through-hole from the light guide 4 side to the substrate 1 side in this way, by irradiating a laser from the second through-hole group side in the formation, the wide first through-hole group side As compared with the case where the laser was irradiated from the laser beam, the emission position of the laser was limited, and the through hole could be manufactured more precisely.

  The core diameter was designed to be φ50 μm on the transmitting side because it is coupled with the optical waveguide, and the light receiving diameter of the PD was φ70 μm on the receiving side. Next, the core was filled with a UV curable transparent epoxy resin having a refractive index of 1.593 and formed in the same manner as the clad. Finally, the surface was polished to form coaxial light Via having a core / cladding structure. The diameter of the through hole provided for the core was 59 μm on the transmitting side and 77 μm on the receiving side.

  Next, a UV curable transparent resin having a refractive index of 1.593 was filled in the core hole and patterned. Finally, the surface was polished, and the optical waveguide 2 (coaxial optical Via) having a length of about 1 mm was completed on the package substrate 6.

  The insertion loss of the produced coaxial light Via was measured. As a result of using GI-50 / 125MMF for the input side optical fiber, GI-50 / 125MMF for transmission on the light receiving side, and GI-62.5 / 125MMF for receiving, the loss is 2.3dB on the transmission side and reception The side was 1.4dB.

(Production of optical module)
A substrate used for a board substrate (another optical transmission substrate) having optical wiring such as another optical waveguide 24 and a mirror is a CPCore (registered trademark) having a size of 100 × 100 × 0.8 mm.

  The other optical waveguide 24 was formed directly on the substrate of the board substrate 9. As the material of the other optical waveguide 24, a UV curable transparent epoxy resin was used. The refractive index is 1.615 for the core, 1.593 for the cladding, non-refractive index difference Δn = 1.4%, and NA = 0.27.

  The other optical waveguide 24 was prepared by first applying a transparent epoxy resin to be a lower clad by spin coating, and pre-baking / exposure / development / post-baking. In the same manner, a core and an upper clad were formed, and an optical waveguide was produced. By patterning not only the core but also the clad, an optical waveguide was formed at an arbitrary location on the surface of the substrate.

  The core of the other optical waveguide 24 has a size of 50 × 50 μm and a pitch of 250 μm. The substrate thickness is 0.8 mm, the lower clad thickness is 15 μm, and the upper clad thickness is 20 μm.

The propagation loss of the optical waveguide measured by the cutback method using 850 nm VCSEL and GI-50 / 125MMF was 0.12 dB / cm ² .

  The optical waveguide pattern had 90 ° bends with a radius of curvature R = 10 mm in two places, and the total length was 10 cm. Six BGA mounting parts for package mounting were provided. This time, a total of 16 optical wires were installed, each consisting of four linear optical waveguides on the top and bottom, and eight curved optical waveguides connecting the upper left and lower right.

  A 45-degree mirror was fabricated as an optical path changer 10 at the end of another optical waveguide 24. The mirror used a blade with a 45 ° tip, and a vertical plane and a 45 ° plane were formed inside another optical waveguide 24. Next, 2000 mm of Au was vapor-deposited on the 45 ° slope to form a reflective film. Finally, a vertical surface was cut out by dicing using a blade having a thickness of 20 μm.

  In order to increase the optical coupling efficiency, a second cladding part 23 was produced as a light confinement structure in a space cut out by dicing. For the optical confinement structure, the same core and clad material as those of the other optical waveguides 24 were used. An optical waveguide core was formed to extend between the 45 degree plane of the mirror and the vertical end face of the other optical waveguide 24, and the periphery of the core was filled with a clad material to form an optical confinement structure.

  When the distance between the mirror and the end of the optical waveguide is measured, the loss is 3.5 dB on the transmission side and 2.8 dB on the reception side in the case of an open mirror, whereas it becomes 2.1 dB on the transmission side and 1.5 dB on the reception side due to the optical confinement structure. The loss improvement of about 1.3 dB was confirmed. The insertion loss of the board in which the confined mirrors were formed at both ends including the bent optical waveguide was 5.5 dB.

  Finally, a fitting pin for fitting with a positioning component of the package was formed using SU-8 which is a thick film resin. Two fitting pins having a thickness of 200 μm and φ697 μm were formed at both ends on the mirror line of the optical waveguide. Specifically, a thick film resin was spin-coated, pre-baked and temporarily cured, exposed using a photomask, developed, and post-baked to form a fitting pin (see FIG. 4).

  Using a metal mask for the package substrate 6, solder paste application and solder ball transfer were performed, and the balls were attached by a reflow furnace. After applying the sealing material to the light confinement portion, the fitting pin on the board substrate 9 and the guide hole of the light guide portion 4 were fitted, and reflow mounting was performed using a mounting jig.

  As described above, the optical module was manufactured, the optical transmission board 6 and the board board 9 were electrically joined, and the optical connection was realized.

It is a fragmentary sectional view showing an example of an embodiment of a package substrate as an optical transmission substrate of the present invention. It is sectional drawing which shows the area | region containing the some optical waveguide in the package board | substrate shown in FIG. It is a perspective view which shows an example of embodiment of the optical module of this invention, (a) is a whole perspective view of an optical module, (b) is a board which is a board | substrate which is another optical transmission board | substrate as a package board | substrate which comprises an optical module. The perspective view which shows the mode before mounting on a board | substrate, (c) is an enlarged photograph which shows a mode when a package board | substrate is mounted on a board board | substrate. It is an enlarged photograph which shows the package board | substrate which has a fitting pin. It is an enlarged photograph which shows a light guide part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 11 The surface 12 of the board | substrate 1 The back surface 13 of the board | substrate 1 The 1st through-hole group 2 Optical waveguide 21 Core part 22 The clad part (1st clad part) of the optical waveguide 2
23 Clad part of optical waveguide 2 provided between substrate 1 and light guide part 4 (second clad part)
24 Other optical waveguides (optical waveguides formed on the board substrate 9)
DESCRIPTION OF SYMBOLS 3 Projection part 31 Optical path 32 Clad part 33 of a projection part Edge part 4 Light guide part 41 Upper surface 42 of the light guide part 4 Lower surface 43 of the light guide part 4 2nd through-hole group 5 Electrical wiring 6 Package board as an optical transmission board 7 Optical Semiconductor Element 8 Joint 9 Board Board as Other Optical Transmission Board 10 Optical Path Changer M Optical Module

Claims (6)

A substrate having a first through-hole group in which through-holes penetrating the front and back surfaces are provided in a row, and electrical wiring formed on the surface layer or the inner layer;
Each of the first through hole groups is a second through hole group in which either of the upper and lower surfaces are joined to either or both of the front and back surfaces, and through holes penetrating the upper and lower surfaces are provided in a row. A light guide portion having a second through-hole group that is an extended portion of the first through-hole group and each of which is narrower than the first through-hole group;
An optical transmission board comprising: a plurality of rows of optical waveguides made of a photosensitive material , provided continuously in each of the first through hole group and the second through hole group.   The optical transmission board according to claim 1, wherein the board is a build-up wiring board, and the light guide unit has a smaller volume than the build-up wiring board.   The optical waveguide includes a core portion and a first cladding portion of an optical waveguide provided around the core portion and having a refractive index lower than that of the core portion, and the substrate near the optical waveguide; The optical transmission board according to claim 1, further comprising a second clad portion that fills a gap with the light guide portion.   The optical transmission board according to claim 1, wherein the light guide portion further includes a guide hole provided on a surface opposite to the joint surface. An optical transmission board according to any one of claims 1 to 4,
Other having another optical waveguide formed on the surface layer or the inner layer and an optical path changer provided at an end of the other optical waveguide and converting an optical path to be coupled to one end of the optical waveguide of the optical transmission board An optical transmission board,
An optical semiconductor element coupled to the other end of the optical waveguide of the optical transmission board;
Including optical module. Forming a first through hole group in which through holes penetrating the front and back surfaces are formed in a row on a substrate having an electrical wiring formed on a surface layer or an inner layer; and
A second through hole group in which through holes penetrating the upper and lower surfaces are provided in a row is formed in advance with the second through hole group of the light guide section and the second through hole group having a smaller diameter than the first through hole group. A step B in which the first through-hole group is aligned so that the end portions overlap each other, and the light guide unit is joined to the substrate on which the first through-hole group is formed;
Injecting a clad member to be a clad part of an optical waveguide into the first through hole group and the second through hole group of the substrate to which the light guide part is bonded; and
A third through hole group having a diameter smaller than that of the clad portion is provided in the center of the first through hole group and the second through hole group into which the clad member is injected, and an optical waveguide core is provided in the third through hole group. A step D of injecting a core member to be a part;
A method of manufacturing an optical transmission board including: