JP4960519B2 - Optical transmission line holding member and optical module - Google Patents

Description

  Embodiments described herein relate generally to an optical semiconductor module used for optical communication technology, optical transmission technology, and the like, and more particularly, to an optical transmission line holding member and an optical module with an improved electrical wiring portion.

  In recent years, in optical communication technology and optical transmission technology, transmission of signals using light as a carrier wave by intensity modulation or phase modulation has been widely performed. For such optical transmission, an optical coupling device for optically coupling an optical semiconductor element such as a light emitting element or a light receiving element and an optical transmission path such as an optical fiber is required.

  As one of this type of equipment, the mounting cost is reduced by a so-called direct optical coupling (butt joint), in which the optical fiber and the optical semiconductor element are opposed to each other in the nearest position to obtain optical coupling without using a lens. The technology to measure is researched and developed. When direct optical coupling is used, it is necessary to reduce the distance between the optical fiber and the optical semiconductor element to about several tens of μm. For this reason, electrical wiring is prepared directly on the main surface of an optical transmission line holding member (so-called optical fiber ferrule) that holds an optical fiber or the like so that the light receiving / emitting region of the optical element faces the optical fiber on the main surface. There has been proposed a method of mounting on a computer (see, for example, Patent Document 1).

  In this method, the optical semiconductor element and the optical fiber can be arranged very close to each other. In addition, since optical semiconductor elements can be mounted on the optical transmission line holding member based on the optical fiber, it can be mounted with high accuracy in the horizontal direction by using normal flip chip mounting, but the number of parts is reduced and the cost is reduced. It can be set as the structure suitable for. Furthermore, by using a resin as the base material of the holding member, it is possible to significantly reduce the component manufacturing cost. In addition, by forming the electrical wiring from the side with the opening of the hole for the optical fiber to the side, orthogonal transformation is realized, and the mounting direction of the mounting substrate is kept parallel to the direction in which the optical fiber extends It is possible to prevent the optical fiber from rising perpendicular to the surface.

JP 2001-159724 A

  However, according to the structure described in (Patent Document 1), in order to arrange the optical fiber in parallel to the mounting surface of the mounting substrate, the electrical surface of the main surface on which the optical semiconductor element of the optical transmission path holding member is mounted. It is necessary to form the wiring three-dimensionally from the main surface to the side surface. Therefore, there is a problem that a three-dimensional process is interposed in the manufacturing process of the electrical wiring, resulting in complicated processes and increased costs.

  Further, in the structure described in (Patent Document 1), the electrical wiring is formed in an L shape along the outer surface of the optical transmission path holding member and performs electrical connection on the side surface. The base material of the transmission path holding member as a base is subjected to inward distortion due to direct bonding. On the other hand, in order to manufacture the optical transmission line holding member at a low cost, it is effective to use a resin as a base material, which is adopted in many products. In this case, since the base material is resin, the base material under the electrode is distorted so that the base material under the electrode is sunk inside, so that stable bonding becomes difficult, and in the worst case, the electrode itself is disconnected due to the strain. There was a problem.

  The present invention has been made in consideration of the above circumstances, and the object of the present invention is to enable direct optical coupling between an optical semiconductor element and an optical transmission line such as an optical fiber at low cost, and to mount an optical element. To provide an optical transmission line holding member capable of stably and easily realizing three-dimensional electrical wiring between a surface and a mounting surface, and capable of arranging an optical fiber and a mounting substrate in parallel, and an optical module using the same. It is in.

  One aspect of the present invention is an optical transmission line holding member having a holding hole for holding an optical transmission line, on a first surface where one opening of the holding hole of the optical transmission line holding member is located. An electrical lead embedded so that at least a part of the longitudinal direction is exposed, and at least one of both end surfaces of the electrical lead is exposed on a second surface adjacent to the first surface. And

  According to another aspect of the present invention, there is provided an optical module including an optical transmission line holding member having a holding hole for holding an optical transmission line and an optical semiconductor element, wherein the optical transmission line holding member includes the optical module. An electrical lead embedded in the optical element mounting surface where one opening of the holding hole is located so that at least a part of the longitudinal direction is exposed, and at least one of both end faces of the electrical lead is on the optical element mounting surface It is exposed on an adjacent surface, and a portion of the electrical lead exposed on the optical element mounting surface is connected to an electrode of the optical semiconductor element.

The perspective view which shows schematic structure of the optical-transmission-path holding member concerning 1st Embodiment. The top view which shows the relationship between an optical transmission path holding member and a lead frame for demonstrating the optical transmission path holding member concerning 1st Embodiment. The perspective view which is for demonstrating the optical-transmission-path holding member concerning 1st Embodiment, and shows the relationship between an optical-transmission-path holding member and a lead frame. Sectional drawing which shows the cross-sectional structure of the optical-transmission-path holding member concerning 1st Embodiment. The perspective view which shows schematic structure of the optical module concerning 2nd Embodiment. The perspective view which shows the example which mounted the optical module of 2nd Embodiment on the mounting board | substrate. Sectional drawing which shows the example which performed flip chip mounting with respect to the optical module of 2nd Embodiment. The perspective view which shows schematic structure of the optical-transmission-path holding member concerning 3rd Embodiment. The top view which shows the example of the electrode pattern of the optical-transmission-path holding member of 3rd Embodiment. The top view which shows the example of the electrode pattern of the optical-transmission-path holding member of 3rd Embodiment. The perspective view which shows schematic structure of the optical-transmission-path holding member concerning 4th Embodiment. Sectional drawing which shows schematic structure of the optical-transmission-path holding member concerning 5th Embodiment. Sectional drawing which shows schematic structure of the optical-transmission-path holding member concerning 5th Embodiment.

  The details of the present invention will be described below with reference to the illustrated embodiments.

(First embodiment)
FIG. 1 is a perspective view showing a schematic configuration of an optical transmission line holding member according to the first embodiment of the present invention.

  In the figure, reference numeral 1 denotes an optical transmission path holding member. The holding member 1 has a holding hole 2 and an electrical lead 3 for the optical transmission path. The holding hole 2 is provided through the holding member 1, and has an opening 4 on the main surface (optical element mounting surface) 8 for exposing the light input / output end of the optical transmission path.

  The optical transmission line holding member 1 is formed, for example, by injection molding using a mold with an epoxy resin mixed with about 80% of a glass filler of about 3 to 30 μm. The electrical lead 3 is made of, for example, Cu, Cu alloy, 42 alloy, or Invar, and has a single layer or combination of any one of Ni, Au, AgSn, AuSn, SnAgCu, SnZnBi, SnAgIn, SnBiAg, and SnPb on the surface. Plating consisting of multiple layers may be applied.

  At least a part of the electrical lead 3 is exposed in order to mount the optical semiconductor element on the optical element mounting surface 8. The electrical lead 3 preferably has a structure in which signal wirings 5 for extracting high-speed signals and common wirings 7 for power supply or GND are alternately arranged, thereby preventing crosstalk between the signal wirings. Reduced. Both ends (cut surfaces) of the common wiring 7 are exposed on the side surface 32 adjacent to the optical element mounting surface 8 to form an exposed portion 31. Further, the exposed portion 31 is similarly formed on one end face of the signal wiring 5. The surface of the exposed portion 31 may be plated. The plated metal is made of, for example, a single layer or a combination of any one of Ni, Au, AgSn, AuSn, SnAgCu, SnZnBi, SnAgIn, SnBiAg, and SnPb.

  Here, a driving element for driving the optical semiconductor element is connected to the end faces of the wirings 5 and 7 exposed on the side surface 32 of the optical transmission line holding member 1 by bonding or the like, and is exposed on another side surface facing the side surface 32. The end surface of the wiring 7 to be connected is connected to the mounting substrate via bumps or the like.

  With such a structure, a pseudo orthogonal wiring from the optical element mounting surface 8 to the side surface 32 can be formed without going through a special three-dimensional process, and the optical transmission line holding member 1 can be connected to the optical transmission line. It becomes easy to mount on a plane parallel to the. Furthermore, with this structure, stress due to bonding on the side surface 32 can be received in the longitudinal direction of the electrical lead 3, thus realizing stable three-dimensional electrical connection that does not cause disconnection or bonding failure due to substrate sinking. can do.

  The above structure can be formed as follows. This will be described with reference to FIGS.

  In FIG. 2, 10 is a lead frame made of Cu or the like, and a pattern of electrical leads 3 is formed. Pattern formation may be performed by etching or punching. Preferably, by forming by etching, irregularities are easily formed in the cross section of the lead frame 10, and the anchor effect when insert molding is performed on resin or the like is high.

  Initially, the signal wiring 5 and the common wiring 7 constituting the electrical lead 3 are all connected by a tie bar 13. Further, as the electrode pattern becomes finer, the electrode width becomes very narrow and it is difficult to ensure the strength. Therefore, the reference numeral 11 in FIG. It may be connected with an auxiliary tie bar. Reference numeral 12 denotes an alignment hole of the lead frame 10. Here, only the pattern for one optical transmission line holding member is shown, but similar patterns are formed in the vertical direction in the drawing.

  The optical transmission line holding member 1 is aligned with the lead frame 10 as shown in FIG. For the molding, continuous injection molding using a hoop can be used. After molding, the lead frame 10 having the optical transmission line holding member 1 formed thereon is connected as shown in FIG. By cutting this according to the outer shape of the optical transmission path holding member 1, an individual piece of the optical transmission path holding member 1 is produced. Thereafter, the side surface is polished to remove burrs and then plated with Au or the like to complete.

  FIG. 4 shows a cross-sectional structure of the optical transmission line holding member 1. As shown in this figure, the signal wiring 5 has a structure in which one cut surface is exposed and the common wiring 7 has both cut surfaces exposed on the side surface of the optical transmission line holding member 1.

  Both the signal wiring 5 and the common wiring 7 are cut from the lead frame 10 in the immediate vicinity of the optical transmission path holding member 1 and then polished for the purpose of deburring. In this case, since the materials of the electrical leads 3 forming the wirings 5 and 7 and the base material of the optical transmission path holding member 1 are different, the polishing speed is different and the polished surface is not necessarily flat. In addition, since plating is performed after polishing, the electrodes (wiring portions) tend to protrude beyond the side surfaces. Therefore, when the side surface is used as the mounting surface, the flatness may be lost and the surface may be inclined. Therefore, a step (not shown: about 50 μm is preferable) may be provided in advance on the side surface of the optical transmission line holding member 1, and the flatness of the mounting surface is achieved by performing polishing on the surface with the lower step. Can be secured.

  As described above, according to the present embodiment, an inexpensive structure capable of directly assembling the optical semiconductor element is realized simply by embedding the electrical lead 3 in the main surface (optical element mounting surface) 8 of the optical transmission line holding member 1. can do. In this case, the linear electrical leads 3 are embedded in the optical element mounting surface 8 without forming the electrical leads on which the optical semiconductor element is mounted from the optical element mounting surface 8 to the side surface 32 in a three-dimensional manner. The electrode pad for drawing out the electrode can be provided on the side surface 32 only by exposing it to 32. For this reason, it is possible to mount the optical fiber in parallel with the mounting surface at low cost without requiring a special process.

  Furthermore, with this structure, stress due to bonding on the side surface 32 can be received in the longitudinal direction of the electrical lead 3, thus realizing stable three-dimensional electrical connection that does not cause disconnection or bonding failure due to substrate sinking. can do.

(Second Embodiment)
FIG. 5 is a perspective view showing a schematic configuration of an optical module according to the second embodiment of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The optical transmission line holding member 1 is configured similarly to the first embodiment. The optical semiconductor element 14 is Au stud bumped so that the light receiving / emitting surface faces the opening 4 side to the electrical wiring 3 (signal wiring 5 and common wiring 7) on the optical element mounting surface 8 of the optical transmission line holding member 1. Mount with (not shown). Then, the optical module 16 is manufactured by inserting and fixing the optical fiber 15 or the like in the holding hole 2. With this structure, the electrical lead for mounting the optical semiconductor element is embedded in the optical element mounting surface 8 without the three-dimensional wiring formation from the optical element mounting surface 8 to the side surface 32. The electrode pad for drawing out the electrode can be provided on the side surface 32 only by exposing it to 32. For this reason, it is possible to provide an optical module in which an optical fiber is mounted in parallel with the mounting surface at low cost without requiring a special process.

  Furthermore, with this structure, stress due to bonding on the side surface 32 can be received in the longitudinal direction of the electrical lead 3, thus realizing stable three-dimensional electrical connection that does not cause disconnection or bonding failure due to substrate sinking. can do.

  FIG. 6 is a perspective view illustrating a case where the optical module of the present embodiment is mounted on a mounting board. The optical module 16 shown in FIG. 5 is assembled on the mounting substrate 17, and the lead exposed on the side surface of the optical module 16 is used as an electrode pad, and the electrode pad 19 and the Au wire of the optical semiconductor element driving IC 18 placed closest to the optical module 16. 20 or the like. By adopting such a configuration, the same effect as when the orthogonal wiring is formed in three dimensions can be obtained, so that it is possible to form a very small and inexpensive optical assembly.

  FIG. 7 shows an example in which flip-chip mounting for shortening the wiring length as much as possible is performed as a structure that can cope with a higher-speed signal. An electrical wiring 40 is formed on the mounting substrate 17, and each member is connected to the electrical wiring 40. That is, the optical module 16 shown in FIG. 5 is mounted by connecting the end face of the electrical lead 3 exposed on the side surface to the electrical wiring 40 by the bump 42. Here, the optical semiconductor element 14 is pre-mounted on the electrical lead 3 by a bump 43. Similarly, the optical semiconductor element driving IC 18 is mounted by being connected to the electric wiring 40 by the bump 41.

  With such a configuration, the length of the path of the analog signal flowing between the optical semiconductor element driving IC 18 and the optical semiconductor element 14 can be shortened, so that a higher-speed signal can be handled.

(Third embodiment)
FIG. 8 is a perspective view showing a schematic configuration of an optical transmission line holding member according to the third embodiment of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the figure, reference numeral 1 denotes an optical transmission path holding member, which has a holding hole 2 and an electrical wiring 3 for the optical transmission path, for exposing the optical input / output end of the optical transmission path on the optical element mounting surface 8. An opening 4 is provided. The optical transmission line holding member 1 is formed of an epoxy resin by injection molding using a mold, and the electric lead 3 may be made of Cu, for example, and may be plated with solder such as Au or SnAg. At least a part of the electrical lead 3 is exposed in order to mount the optical semiconductor element on the optical element mounting surface 8. The electrical lead 3 has a structure in which signal wirings 5 for extracting high-speed signals and common wirings 7 for power supply or GND are alternately arranged.

  The configuration up to this point is the same as that of the first embodiment. In this embodiment, in addition to this, a dummy wiring 6 is provided. That is, the dummy wiring 6 is formed at a position facing the signal wiring 5 with respect to the opening 4 on the optical element mounting surface 8 side. The common wiring 7 is wired so as to cross the optical element mounting surface 8 in the vertical direction in the drawing, and therefore, the asymmetry with respect to the opening 4 is eliminated as much as possible.

  As described above, the present embodiment basically has the same structure as that of the first embodiment. The difference from the first embodiment is that a dummy wiring 6 is newly provided and the electrical lead 3 is connected to the opening 4. This is because the symmetry is improved. Accordingly, the following effects can be obtained by arranging the electric wiring as well as the same effects as those of the first embodiment.

  That is, the stress caused by the difference in thermal expansion coefficient between the base material of the optical transmission path holding member 1 and the metal of the electrical lead 3 during the heat process when forming the optical transmission path holding member 1 is the axis of the holding hole 2 of the optical transmission path. It can be made symmetric in the plane of the main surface 8 orthogonal to the direction. Therefore, the deformation of the holding hole 2 is axisymmetric, and at least the amount of displacement of the relative position in the plane 8 of the central axis of the holding hole 2 can be minimized. Further, since the deformation of the shape and size of the holding hole 2 is also axisymmetric, there is an advantage that the design of deformation due to stress is greatly simplified.

  Further, as shown in FIG. 9, each of the electrical wirings 5, 6, and 7 is formed in an arc shape by matching the shape of the opening 4 with a portion close to the opening 4 so that the distance from the edge of the opening 4 is as equal as possible. It may be formed. FIG. 9 shows a case where the signal wiring 5 and the dummy wiring 6 are closer to the opening 4 than the common wiring 7, and a wiring 23 partially drawn out from the common wiring 7 is formed in order to increase symmetry. Thus, the distance from the opening 4 is made equal. By doing so, the stress distribution in the thermal process becomes highly symmetrical in the vertical direction and the horizontal direction, so that the deformation of the outer shape due to the distortion of the holding hole 2 can be further suppressed.

  Furthermore, as shown in FIG. 10, when the signal wiring 5 and the dummy wiring 6 are farther from the opening 4 than the common wiring 7, a shape 24 in which a part of the common wiring 7 is recessed may be formed. In this case as well, since the stress distribution in the thermal process is highly symmetrical in the vertical direction and the horizontal direction, the deformation of the outer shape due to the distortion of the holding hole 2 can be further suppressed.

(Fourth embodiment)
11A and 11B are perspective views showing a schematic configuration of an optical transmission line holding member according to the fourth embodiment of the present invention, wherein FIG. 11A is an overall configuration diagram, and FIG. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As the pitch of electrical leads becomes finer, the width of the leads themselves tends to become very narrow. For this reason, the area of the optical transmission line holding member 1 that contacts the substrate when embedded in the optical transmission line holding member 1 is reduced, and the tensile strength in the normal direction of the main surface tends to be insufficient. Therefore, in the present embodiment, the cross section of the electrical lead is not a simple rectangle but a polygonal shape, and the tensile strength in the principal surface normal direction is increased.

  Specifically, in the cross section of the electric lead, the width of the portion embedded in the optical transmission line holding member 1 is made wider than the width of the exposed portion on the main surface 8. In other words, the cross-sectional shape along the main surface 8 of the electrical lead 3 (wirings 5 and 7) is used to have a portion that expands in the embedded deep portion rather than the embedded surface portion.

  With such a configuration, since the exposed portion 31 of the electrical lead 3 is formed to have a wide width inside, it is possible to enhance the tensile strength in the main surface normal direction. For this reason, it is possible to prevent the electrical lead 3 from falling off the optical transmission line holding member 1, and to improve the reliability. The cross-sectional shape as described above can be easily formed by performing double-sided etching when forming a lead frame including the electrical leads 3 as shown in FIG.

(Fifth embodiment)
FIG. 12 is a sectional view showing a schematic configuration of an optical transmission line holding member according to the fifth embodiment of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  Although the basic configuration is the same as that of the first embodiment, in this embodiment, in addition to this, the electric lead 3 has a structure having a partial recess 33 in the longitudinal direction. According to such a structure, the dent 33 is in the form of biting into the base material of the optical transmission line holding member 1, and the tensile strength in the direction parallel to the main surface can be increased. This structure can be easily formed by half-etching a part when forming the electrical lead 3.

  As shown in FIG. 13, the recessed portion 33 of the electrical lead 3 may be in a direction exposed on the main surface where the opening 4 of the holding hole 2 is located. In this case, the pattern can be formed by the electrical leads 3 partially exposed on the main surface 8. If this pattern is matched with the bonding pattern of the optical semiconductor element, solder plating can be performed only on this portion. In this case, it is possible to prevent failures such as chip position shift and short circuit due to solder flow.

(Modification)
The present invention is not limited to the above-described embodiments. In the embodiment, the cut surface of the electric lead is flush with the side surface adjacent to the optical element mounting surface, but the electric lead may protrude outward from the side surface. In the embodiment, an optical fiber is used as the optical transmission line, but an optical waveguide can also be used. Furthermore, the material as the base material of the optical transmission path holding member and the material such as the electrical wiring can be appropriately changed according to the specifications.

  In addition, various modifications can be made without departing from the scope of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Optical transmission path holding member, 2 ... Optical transmission path holding hole, 3 ... Electric lead, 4 ... Opening, 5 ... Signal wiring, 6 ... Dummy wiring, 7 ... Common wiring, 8 ... Main surface (Optical element mounting surface) 10 ... Lead frame, 11 ... Auxiliary tie bar, 12 ... Alignment hole, 13 ... Tie bar, 14 ... Optical semiconductor element, 15 ... Optical fiber (optical transmission line), 16 ... Optic module, 17 ... Mounting substrate, 18 ... IC for optical semiconductor element drive, 19 ... electrode pad, 20 ... Au wire, 23 ... wiring, 24 ... depression, 31 ... exposed portion, 32 ... side, 33 ... depression, 40 ... electric wiring, 41, 42, 43 …bump.

Claims (9)

An optical transmission line holding member having a holding hole for holding an optical transmission line,
An electrical lead embedded in the first surface where one opening of the holding hole of the optical transmission path holding member is located so that at least a part of the longitudinal direction is exposed, and at least both end faces of the electrical lead One of the optical transmission line holding members is exposed on a second surface adjacent to the first surface.   2. The optical transmission line holding member according to claim 1, wherein the exposed portion of the end face of the electric lead serves as a connection terminal for electrically connecting the electric lead to the outside.   3. The optical transmission line holding member according to claim 1, wherein metal plating is applied to a portion exposed on the first surface of the electric lead and an exposed portion of an end surface of the electric lead.   The optical transmission line holding member is made of a resin material containing glass filler, the electric lead is made of Cu, Cu alloy, 42 alloy, or Invar material, and the metal plating is Ni, Au, AgSn, AuSn, SnAgCu, SnZnBi, 4. The optical transmission line holding member according to claim 3, wherein the optical transmission line holding member is composed of a single layer or a combination of SnAgIn, SnBiAg, and SnPb.   5. The optical transmission line holding member according to claim 1, wherein the electrical leads are disposed point-symmetrically with respect to a center of the opening in the first plane.   The cross-sectional shape along the second surface of the electrical lead has a portion that extends in the embedded deep portion rather than the embedded surface portion of the first surface. The optical transmission line holding member as described.   The optical transmission according to any one of claims 1 to 6, wherein the electrical lead has a partial recess in the longitudinal direction, and the recess is not exposed on the first surface. Road holding member. An optical module comprising an optical transmission line, an optical transmission line holding member having a holding hole for holding the optical transmission line, and an optical semiconductor element,
An electrical lead embedded in the optical element mounting surface on which one opening of the holding hole of the optical transmission path holding member is located so that at least a part of the longitudinal direction is exposed; One of the optical modules is exposed on a surface adjacent to the optical element mounting surface, and a portion of the electrical lead exposed on the optical element mounting surface is connected to an electrode of the optical semiconductor element.   9. The optical module according to claim 8, wherein the exposed portion of the end face of the electrical lead is electrically connected to a drive element that drives the optical semiconductor element.

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