JP2016001237A - Optical transmission module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transmission module with which it is possible to align optical cables with high accuracy.SOLUTION: An optical transmission module 100 comprises: a surface emission laser 10 having a light-emitting unit 11 for outputting an optical signal; a circuit board 20 provided with a through-hole 21 for letting the optical signal outputted from the surface emission laser 10 pass through; an optical cable 30 for propagating the optical signal outputted from the surface emission laser 10; and a guide holding member 40 having a through-hole 41 for inserting the optical cable 30 therethrough, and a bottom face by which it is mounted on the circuit board 20 and is optically polished, with a recess formed on the bottom face. The surface emission laser 10 is flip-chip mounted on the circuit board 20 so that the light-emitting unit 11 is located above the through-hole 21, and the guide holding member 40 for holding the optical cable 30 is mounted so as to face the surface emission laser 10 via the circuit board 20.

Description

  The present invention relates to an optical transmission module.

  Conventionally, medical endoscopes enable observation of lesions by inserting the insertion part deeply into the body, and also enables inspection and treatment of the body by using a treatment tool as needed It is said. As such an endoscope, there is an endoscope provided with an imaging device having a built-in imaging element such as a CCD at the tip of an insertion portion. In recent years, an image sensor having a high pixel number that enables clearer image observation has been developed, and the use of an image sensor having a high pixel number for an endoscope has been studied. When an imaging device having a high pixel count is used in an endoscope, an optical transmission module using an optical cable may be incorporated in the endoscope in order to transmit a signal between the imaging device and a signal processing device at high speed. Necessary. In such an optical transmission module, it is desired to reduce the outer diameter of the distal end and the length of the distal end as much as possible in consideration of reducing the burden on the patient, and an image sensor such as a CCD and an optical cable are used to improve image quality. It is required to propagate the optical signal with accurate alignment.

  As a method for fixing the optical fiber with high accuracy, a stopper for guiding and holding the optical fiber is formed by a transparent member, and the polarization holding surface of the optical fiber is oriented by illuminating and observing from a transparent side surface. A technique is disclosed (for example, see Patent Document 1).

Japanese Patent Application Laid-Open No. 08-320423

  However, in Patent Document 1, the polarization maintaining surface of the optical fiber in the tube is set in a desired direction while observing from the transparent side surface of the fastener, and the optical fiber is fixed to the fastener by penetrating an adhesive into the tube. After that, the optical component and the optical fiber are positioned by sliding each other until the ideal coupling position with the positioning surfaces facing each other. However, any means for positioning at the ideal coupling position is disclosed. Absent.

  The present invention has been made in view of the above, and an object of the present invention is to provide an optical transmission module capable of accurately aligning an optical cable.

  In order to solve the above-described problems and achieve the object, an optical transmission module according to the present invention includes an optical element having a light receiving unit that inputs an optical signal or a light emitting unit that outputs an optical signal, and an input or output to the optical element. A substrate having a through hole for passing the optical signal to be output; an optical cable for propagating an optical signal input or output from the optical element; and a through hole for inserting the optical cable; And a guide holding member having a recess formed on the bottom surface, and flips so that the light receiving portion or the light emitting portion of the optical element is positioned on the through hole of the substrate. The guide holding member for holding the optical cable is mounted so as to face the optical element through the substrate while being mounted in a chip.

  Moreover, the optical transmission module according to the present invention is characterized in that, in the above invention, the recess is formed in two symmetrical positions with respect to the center of the through hole.

  The light transmission module according to the present invention is characterized in that, in the above invention, the guide holding member is optically polished on an upper surface facing the bottom surface and has a recess formed on the upper surface.

  Further, in the optical transmission module according to the present invention, in the above invention, two concave portions formed on the upper surface are formed symmetrically with respect to a center of the through hole, and the two concave portions on the upper surface are formed by the guide holding member. It is characterized in that it is formed symmetrically with the concave portion of the bottom surface around the center of gravity.

According to the present invention, the bottom surface, which is the mounting surface of the guide holding member on the substrate, is optically polished, and a concave portion that can be visually recognized is formed on the bottom surface. Can be implemented. Accordingly, the optical cable inserted through the through hole of the guide holding member can be accurately aligned, and an optical transmission module in which the amount of light input and output between the optical element and the optical cable is stable can be obtained.
In addition, when the guide holding member is mounted on the substrate, the adhesive enters into the recess when there is an excess adhesive, so that the adhesive can be prevented from protruding into the through hole.

FIG. 1 is a cross-sectional view of an optical transmission module according to an embodiment of the present invention. FIG. 2 is a perspective view of the guide holding member according to the embodiment of the present invention. FIG. 3 is a bottom view of the guide holding member according to the embodiment of the present invention. FIG. 4 is a side view of the optical transmission module according to the embodiment of the present invention. FIG. 5 is a flowchart of the manufacturing process of the optical transmission module according to the embodiment of the present invention. FIG. 6 is a perspective view of a guide holding member according to Modification 1 of the embodiment. FIG. 7 is a perspective view of a guide holding member according to Modification 2 of the embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “embodiments”) will be described with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments. In the description of the drawings, the same parts are denoted by the same reference numerals. The drawings are schematic, and it is necessary to note that the relationship between the thickness and width of each member, the ratio of each member, and the like are different from the actual ones. Also in the drawings, there are included portions having different dimensional relationships and ratios.

  FIG. 1 is a cross-sectional view of the optical transmission module according to Embodiment 1 of the present invention. FIG. 2 is a perspective view of a guide holding member used in the optical transmission module of FIG. FIG. 3 is a bottom view of the guide holding member according to the embodiment of the present invention. FIG. 4 is a side view of the optical transmission module according to the embodiment of the present invention.

  An optical transmission module 100 according to an embodiment of the present invention includes a surface emitting laser 10 that is an optical element, a substrate 20 on which the surface emitting laser 10 is mounted, an optical cable 30 that transmits an optical signal, and a guide that holds the optical cable 30. Holding member 40. In the optical transmission module according to the present invention, any of a light receiving element such as a photodiode and a light emitting element such as a surface emitting laser can be adopted as an optical element. The case where the optical element is a surface emitting laser 10 will be described. .

  The substrate 20 is an FPC substrate, ceramic substrate, glass epoxy substrate, glass substrate, Si substrate, or the like, and has a through hole 21 through which light emitted from the light emitting portion 11 of the surface emitting laser 10 passes. In the present embodiment, the inner diameter of the through hole 21 is the same as or slightly larger than the outer diameter of the optical cable 30 described later.

  A connection electrode 22 is formed on the substrate 20, and an electrical signal is transmitted to the surface emitting laser 10 through the connection electrode 22. The surface emitting laser 10 is a flip chip type mounted on the substrate 20 so that the light emitting unit 11 faces the substrate 20. The surface-emitting laser 10 is mounted on the substrate 20 by, for example, forming Au bumps 12 on the surface-emitting laser 10 and bonding them on the connection electrodes 22 of the substrate 20 by ultrasonic waves, or underfill material at the bonding portion. Then, an adhesive 13 such as a side fill material is injected, and the adhesive 13 is cured and mounted. Alternatively, the solder bumps may be printed on the substrate 20 without using the Au bumps 12, and the surface emitting laser 10 may be disposed, and then solder may be melted and mounted by reflow or the like. Alternatively, solder bumps may be formed on the surface emitting laser 10, placed on the connection electrode 22 of the substrate 20 by a mounting device, and mounted by melting the solder.

  In mounting the surface emitting laser 10 on the substrate 20, the center of the light emitting unit 11 of the surface emitting laser 10 and the center of the through hole 21 are aligned using a two-field optical system, and the through hole 21 is directly below the light emitting unit 11. Implement to be located.

  The guide holding member 40 has a through hole 41 through which the optical cable 30 is inserted. The through hole 41 may have a prismatic shape in addition to a cylindrical shape. The guide holding member 40 is formed of a transparent material in the ultraviolet and visible light regions such as glass. As shown in FIG. 2, the guide holding member 40 according to the present embodiment has a rectangular parallelepiped shape, and the through hole 41 is formed at the center of the upper surface 51 and the bottom surface 50 and perpendicular to the upper surface 51 and the bottom surface 50. Yes. At both ends of the through hole 41, a taper 45 and a taper 46 are formed.

  When the supply amount of the adhesive 43 on the substrate 20 is supplied more than a predetermined amount, or when a load larger than a predetermined load is applied when the guide holding member 40 is mounted on the substrate 20, the adhesive 43 is However, by forming the taper 46, the adhesive 43 can be prevented from protruding into the through hole 21. Further, by forming the taper 45 on the insertion side of the optical cable 30 in the through hole 41, the insertion of the optical cable 30 into the through hole 41 is facilitated, and the adhesive 44 is supplied into the taper 45 so that the optical cable 30 and the guide are provided. Since the holding member 40 is bonded, the bonding area between the guide holding member 40 and the optical cable 30 can be increased, and the bonding strength can be improved.

  The bottom surface which is a mounting surface on the substrate 20, that is, the surface 50 shown in FIG. 2 is optically polished. Further, a recess 42a and a recess 42b are formed on the surface 50 which is the bottom surface. In the present embodiment, the recess 42a and the recess 42b have a function of an alignment mark. The guide holding member 40 is mounted by aligning the center of the light emitting portion 11 of the surface emitting laser 10 and the center of the through hole 41 using a two-field optical system, and the through hole is formed from the positions of the concave portion 42a and the concave portion 42b. By recognizing the center of 41, the guide holding member 40 can be mounted on the substrate 20 with high accuracy.

  The concave portion 42a and the concave portion 42b have a hemispherical groove shape, but may have a conical shape, and the shape is not limited as long as the shape is the same when viewed from the surface 50 side. Since the concave portion 42a and the concave portion 42b are groove-shaped, when the amount of the adhesive 43 applied on the substrate 20 is large, the adhesive 43 can be taken into the concave portion 42a and the concave portion 42b. The protrusion to 41 can be prevented.

  The recess 42a and the recess 42b are preferably formed at symmetrical positions with respect to the center C of the through hole 41 as shown in FIG. Moreover, since it is preferable to form the recessed part 42a and the recessed part 42b in the position as distant as possible, they are each formed in the corner vicinity on a diagonal.

  For example, in the state of a wafer (glass plate), the guide holding member 40 is singulated by forming a plurality of through holes 41, tapers 45 and 46, and concave portions 42a and 42b on the optically polished surface and dicing. do it. The through hole 41, the tapers 45 and 46, and the recesses 42a and 42b are formed in a grain shape because they are formed by drilling, etching, or the like. Accordingly, when the concave portion 42a and the concave portion 42b formed on the surface 50 are imaged by the optical system, the contrast difference between the optically polished surface 50 and the grain-like concave portion 42a and the concave portion 42b becomes large, and image recognition becomes easy. . Further, the recess 42a and the recess 42b are formed in the same process as the through hole 41 by drilling or etching, so that the positional relationship with the through hole 41 can be processed with high accuracy.

  It is preferable that at least one of the side surfaces of the guide holding member 40, that is, the surfaces 52, 53, 54, 55 parallel to the optical axis of the optical cable 30 inserted through the through hole 41 is optically polished. When the two surfaces are optically polished surfaces, the opposing surfaces, for example, the surfaces 52 and 54 are preferably optically polished surfaces, and the surfaces 53 and 55 are preferably grained surfaces that are not optically polished. By optically polishing a surface parallel to the optical axis of the guide holding member 40, insertion of the optical cable 30 into the through hole 41 can be observed from the optical surface.

  When the guide holding member 40 is separated from the wafer by dicing, the optical polishing surface can be formed by adjusting (slowing) the dicing speed. By dicing the wafer in the X direction (lateral direction) at a normal speed and dicing in the Y direction (longitudinal direction) at a slow speed that is optically polished, the two opposing surfaces are optically polished surfaces, and the other two surfaces Can obtain a grained (polished glass) guide holding member 40.

  For example, the guide holding member 40 is formed by applying the adhesive 43 to the mounting surface of the substrate 20, and then using the two-field optical system to guide the guide holding member 40 to the center of the light emitting portion 11 and the center of the through hole 41 of the surface emitting laser 10. Are mounted on the adhesive 43 by a device such as a bonder, and the adhesive 43 is cured and mounted. The guide holding member 40 is mounted so as to face the surface emitting laser 10 through the substrate 20.

  The optical cable 30 is obtained by coating an optical fiber that propagates an optical signal from the surface emitting laser 10 with a jacket made of resin or the like. The optical fiber includes a core that transmits light and a clad provided on the outer periphery of the core. The optical cable 30 according to the present embodiment is preferably inserted through the through hole 41 of the guide holding member 40 in a state of being covered with a jacket from the viewpoint of protecting the optical fiber. 41 may be inserted.

  Next, a method for manufacturing the optical transmission module 100 according to Embodiment 1 will be described with reference to FIG. FIG. 5 is a flowchart of the manufacturing process of the optical transmission module according to Embodiment 1 of the present invention.

  First, the surface emitting laser 10 is mounted on the substrate 20 (step S1). Mounting is performed so that the through hole 21 of the substrate 20 is positioned immediately below the light emitting portion 11 of the surface emitting laser 10, and then the Au bumps 12 and the like formed on the surface emitting laser 10 and the connection electrodes 22 of the substrate are arranged. Are connected by an adhesive 13 or the like.

  Next, the center of the through hole 41 is recognized based on the positions of the recess 42a and the recess 42b of the guide holding member 40 (step S2). The optical system confirms the image of the concave portion 42a and the concave portion 42b on the surface 50 which is the bottom surface, recognizes the coordinates with the intermediate point between the concave portion 42a and the concave portion 42b as the center of the through hole 41, and the inclination (θ) of the guide holding member 40. Also check.

  Subsequently, the guide holding member 40 is mounted on the substrate 20 (step S3). The guide holding member 40 is mounted on the substrate 20 by adjusting the inclination of the guide holding member 40 based on the coordinates of the center of the through hole 41 recognized in step S2 and the inclination of the guide holding member 40. It mounts on the board | substrate 20 with apparatuses, such as a bonder, so that the center of the through-hole 41 may be located in the center of the light emission part 11 of the surface emitting laser 10, and the adhesive agent 43 previously apply | coated to the board | substrate 20 is hardened and mounted. That's fine.

  After the guide holding member 40 is mounted on the substrate 20, the optical cable 30 is inserted into the through hole 41, and alignment is performed (step S4). The optical cable 30 inserted into the through hole 41 is observed from an optical polishing surface parallel to the optical axis of the guide holding member 40, and the end of the optical cable 30 is aligned with the target position. In the present embodiment, since the end position of the optical cable 30 can be confirmed from the optical polishing surface parallel to the optical axis of the guide holding member 40, the positioning becomes easy.

  In the present embodiment, the recess 42a and the recess 42b are formed on the bottom surface (surface 50) that is the mounting surface of the guide holding member 40 with the substrate 20, but optical polishing parallel to the optical axis of the guide holding member 40 is performed. Since the grain-like concave portions 42a and the concave portions 42b can be observed from the surface, the top portions of the concave portions 42a and the concave portions 42b can be set as positioning targets of the end portions of the optical cable 30. Further, since the adhesive 43 entering the recess 42a and the recess 42b can be observed from the optical polishing surface parallel to the optical axis of the guide holding member 40, the amount of the adhesive 43 entering the recess 42a and the recess 42b is determined from the amount of the adhesive 43. It is also possible to determine the excess or deficiency of 43, that is, the adhesive strength between the substrate 20 and the guide holding member 40.

  The optical cable 30 may be fixed after the optical cable 30 is aligned in the optical axis direction by observing the end of the optical cable 30 from the optical polishing surface parallel to the optical axis of the guide holding member 40. After alignment, after aligning the optical cable 30 in a plane perpendicular to the optical axis direction, the optical cable 30 is fixed, whereby an optical transmission module with a more stable light quantity can be obtained. The alignment in the plane perpendicular to the optical axis direction of the optical cable 30 is such that the amount of light input to the optical cable 30 is measured while emitting light from the light emitting unit 11 of the surface emitting laser 10 so that the amount of light is equal to or greater than a specified value. The optical cable 30 is aligned. The amount of light input to the optical cable 30 may be measured by connecting the other end of the optical cable 30 to a photodiode, power meter, oscilloscope or the like.

  Alternatively, when a guide holding member whose surface parallel to the optical axis is not optically polished is used, both the optical cable direction of the optical cable 30 inserted into the through hole and the alignment on the surface perpendicular to the optical axis are both optical cables. The amount of light input to 30 may be measured and aligned so that the amount of light exceeds a specified value.

  After positioning of the optical cable 30, the optical cable 30 is fixed with the adhesive 44 (step S5). The optical cable 30 may be fixed by filling the taper 45 with the adhesive 44 and irradiating the optical polishing surface with UV light or the like to cure the adhesive 44. The optical cable 30 is bonded and fixed to the optical transmission module 100 by the curing of the adhesive 44. UV light may be irradiated from a grainy surface that is not optically polished, but UV light should be irradiated from the optically polished surface in order to prevent UV-high diffused reflection and cure the adhesive efficiently. Is preferred. In this embodiment, since the adhesive 44 is supplied into the taper 45 to join the optical cable 30 and the guide holding member 40, the joining area between the guide holding member 40 and the optical cable 30 can be increased, and the joining strength is improved. can do.

  The light transmission module 100 produced as described above emits light from the light emitting portion 11 of the surface emitting laser 10, and the emitted light enters the optical cable 30 through the through hole 21 formed in the substrate 20. To do. The optical signal propagated through the optical cable 30 is processed by an optical element module including a photodiode, a transimpedance amplifier, and the like to which the other end of the optical cable 30 is connected, and an external signal processing circuit.

  Since the optical transmission module 100 according to the present embodiment is provided with the groove-shaped recess 42a and the recess 42b that function as alignment marks on the bottom surface (surface 50) that is a mounting surface with the substrate 20, the guide holding member 40 is provided. The center of the through hole 41 can be accurately recognized, and the mounting accuracy of the guide holding member 40 on the substrate 20 can be improved. Further, even when the amount of the adhesive 43 that fixes the substrate 20 and the guide holding member 40 is large, the adhesive 43 can be taken into the recess 42a and the recess 42b, so that the adhesive 43 does not protrude into the through hole 41. can do.

  In the present embodiment, the guide holding member 40 optically polishes the bottom surface (surface 50), which is the mounting surface on the substrate 20, to form the recesses 42a and the recesses 42b. A concave portion may be formed also on the upper surface by optical polishing. FIG. 6 is a perspective view of a guide holding member according to Modification 1 of the embodiment. In the guide holding member 40A according to the first modification, the upper surface (surface 51) facing the bottom surface is optically polished, and a recess 42c and a recess 42d are formed on the upper surface (surface 51). The recess 42 c and the recess 42 d are formed at positions symmetrical with respect to the center of the through hole 41. According to the modification 1, it can be mounted on either the upper surface or the lower surface of the guide holding member.

  Further, it is preferable that the two concave portions formed on the upper surface of the guide holding member are formed so as to be symmetrical with the two concave portions on the bottom surface with the center of gravity of the guide holding member as the center. FIG. 7 is a perspective view of a guide holding member according to Modification 2 of the embodiment. In the guide holding member 40B according to the modified example 2, the two concave portions 42e and the concave portions 42f formed on the upper surface (surface 51) of the guide holding member 40B are 2 on the bottom surface (surface 50) with the center of gravity of the guide holding member 40B as the center. It is symmetrical with the two concave portions 42a and the concave portions 42b, that is, formed so as to be positioned at the concave portions 42a and the concave portions 42b when the guide holding member 40B is rotated 180 °. According to the second modification, the mounting can be performed on either the upper surface or the lower surface of the guide holding member, and the position of the concave portion on the mounting surface is the same on any surface, so that processing is easy when observing with the optical system. It becomes.

DESCRIPTION OF SYMBOLS 10 Surface emitting laser 11 Light emission part 12 Au bump 13, 43, 44 Adhesive 20 Board | substrate 21 Through hole 22 Connection electrode 30 Optical cable 40, 40A, 40B Guide holding member 41 Through-hole 42a, 42b, 42c, 42d, 42e, 42f Recessed part 45, 46 Taper 50, 51, 52, 53, 54, 55 Surface 100 Optical transmission module

Claims (4)

An optical element having a light receiving portion for inputting an optical signal or a light emitting portion for outputting an optical signal;
A substrate comprising a through hole that allows the optical signal that is input to or output from the optical element to pass therethrough;
An optical cable for propagating the optical signal;
A guide holding member having a through hole for inserting the optical cable, a bottom surface which is a mounting surface on the substrate is optically polished, and a recess is formed on the bottom surface,
The light receiving part or the light emitting part of the optical element is flip-chip mounted so as to be positioned on the through hole of the substrate, and the guide holding member that holds the optical cable is interposed between the optical element and the optical element. An optical transmission module, which is mounted so as to be opposed to the optical transmission module.   2. The optical transmission module according to claim 1, wherein two of the recesses are formed at symmetrical positions with respect to the center of the through hole.   3. The optical transmission module according to claim 1, wherein the guide holding member has an upper surface facing the bottom surface that is optically polished and a recess is formed on the upper surface. 4.   Two recesses formed on the upper surface are formed at symmetrical positions with respect to the center of the through hole, and the two recesses on the upper surface are symmetrical with the two recesses on the bottom surface around the center of gravity of the guide holding member. The optical transmission module according to claim 2, wherein the optical transmission module is formed as follows.

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