JP2009053280A - Optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical module in which optical axes at light incidence and light exiting are changed in an inexpensive configuration without using a lens or the like and further, and which is significantly reduced in height. <P>SOLUTION: The optical module is equipped with: an upper structure 5 having an optical transmission body 7 which has a structure bent into an arc and in which the optical axis on an external side and the optical axis on an optical element side are perpendicular to each other, and a holding member 6 holding the optical transmission body 7; and a lower structure 25 on which an optical element 40 is mounted, and in which the upper structure 5 is positioned and placed at an upper side so as to optically connect the optical transmission body 7 of the upper structure 5 to the optical element 40. When the upper structure 5 is placed on the lower structure 25, the end face 7a of the optical transmission body 7 is placed facing the optical element 40, and thus, the optical transmission body 7 and the optical element 40 are optically connected to each other. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical module.

  In the field of optical communication using light as an information transmission medium, an optical module including an optical element that mutually converts an optical signal and an electrical signal is used to receive or transmit an optical signal transmitted through an optical fiber or the like. ing. A surface emitting element typified by a vertical cavity surface-emitting laser (VCSEL) is used for the conversion from an electrical signal to an optical signal, and a PIN is used for the conversion from an optical signal to an electrical signal. A surface light receiving element typified by a photodiode is used. These optical elements are electrically connected to the substrate, and optical fibers and the like are optically connected to the optical elements.

  Such an optical module has an optical transmission body such as an optical fiber from the viewpoint of workability when optical wiring such as an optical fiber is performed on a wiring board (printed wiring board or board), and ease of maintenance and replacement. It is desirable to be detachable via a connector.

  In addition, when an optical fiber or the like is attached to or detached from the optical element, a structure for attaching or detaching the optical fiber or the like around the component on which the optical element is mounted should be provided if it is configured to be attached to and detached from the wiring board in the horizontal direction. Since it cannot be obtained, there is a problem that other parts cannot be mounted in the space, and the mounting density cannot be increased. Therefore, it is desirable that attachment / detachment of an optical fiber or the like can be performed in a direction perpendicular to the wiring board.

Conventionally, in order to meet such demands, an optical element is mounted so that its light emitting / receiving surface is horizontal with respect to the wiring board, and a reflection mirror is provided on the end face of an optical fiber or the like to vertically align the optical axis. There has been proposed an optical module that optically connects an optical fiber or the like and an optical element so as to be detachable in a vertical direction by using a connector converted into (see Patent Document 1).
JP 2006-65358 A

  However, when a reflection mirror is used to convert the optical axis of the connector to a vertical position, there are problems that the cost of the optical module is increased and light loss occurs on the reflection surface.

  Further, in the structure in which the optical transmission body is attached / detached by the connector, a lens is generally arranged in order to increase the optical alignment accuracy and the optical coupling efficiency, but the lens is expensive, and a plurality of wiring boards For example, when the connectors are stacked, it is desired to reduce the height of the connector by reducing the thickness in the vertical direction. However, when a lens is used, there is a problem that it is difficult to reduce the height of the connector.

  The present invention has been made in view of the circumstances as described above, and can convert the incident and outgoing optical axes with a low-cost configuration without using a lens or the like. The problem is to provide an optical module.

  The present invention is characterized by the following in order to solve the above problems.

  1stly, the optical module of this invention optically connects the optical transmission body which transmits an optical signal, and the optical element which converts an optical signal into an electrical signal, or converts an electrical signal into an optical signal. An upper portion having a structure bent in an arc shape and having an optical transmission body in which an optical axis on the outer side and an optical axis on the optical element side are perpendicular to each other, and a holding member for holding the optical transmission body A structure and a lower structure on which the optical element is mounted and the upper structure is positioned and arranged so that the optical transmission body of the upper structure is optically connected to the optical element. When the upper structure is arranged on the lower structure, the end face of the optical transmission body is arranged to face the optical element, so that the optical transmission body and the optical element are optically connected. It is characterized by that.

  Second, in the first optical module, the radius of curvature of the optical transmission body is 5 mm or less.

  Third, in the first or second optical module, the optical transmission body is an optical fiber, and an outer peripheral portion of the optical fiber is covered with a resin material.

  Fourth, in any one of the first to third optical modules, the refractive index ratio (core refractive index / cladding refractive index) of the core and the cladding in the optical transmission body is 1.5% or more. To do.

  Fifth, in any one of the first to fourth optical modules, the optical element mounted on the lower structure is electrically connected to the outside by a bonding wire, and the optical transmission body of the upper structure is The inner side of the arc in the vicinity of the end face is exposed from the holding member, and the upper structure has at least a part of the bonding wire when the upper structure is disposed on the lower structure along the exposed region. A relief portion of a bonding wire, which is a space in which is located, is formed.

  According to the first aspect of the present invention, in the upper structure, the optical transmission body is bent in an arc shape to convert the incident / exit optical axis, so that the optical transmission element of the lower structure is changed with respect to the optical element of the lower structure. Since the optical connection is made with the end faces facing each other, the input and output optical axes can be converted with a low-cost configuration, and the height of the upper structure can be greatly reduced. As a result, a low profile can be realized.

  According to the second aspect of the invention, since the radius of curvature of the optical transmission body is set to a specific value or less, in addition to the effect of the first aspect of the invention, the upper structure can be significantly reduced in height and the entire optical module can be reduced. As a result, a significant reduction in height can be realized.

  According to the third aspect of the invention, since the outer peripheral portion of the optical fiber is coated with the resin material, in addition to the effects of the first or second aspect of the invention, a small diameter is used to reduce the radius of curvature of the optical fiber. Even when an optical fiber is used and the fiber is bent tightly, the strength of the optical fiber can be sufficiently secured.

  According to the fourth aspect of the invention, since the refractive index ratio between the core and the clad in the optical transmission body is set to a specific value or more, in addition to the effects of the first to third aspects, the radius of curvature of the optical fiber is reduced. Even when a thin optical fiber is used and the fiber is bent tightly, leakage of signal light from the optical transmission body can be sufficiently suppressed.

  According to the fifth aspect of the present invention, since the inside of the arc in the vicinity of the end face of the optical transmission body is exposed from the holding member, the relief portion of the bonding wire connected to the optical element of the optical element mounting substrate is provided. In addition to the effects of the first to fourth inventions, when the optical connection is made, it is possible to prevent the lower surface of the upper structure and the bonding wire from contacting each other. Furthermore, since the escape portion is formed by exposing only the inner side of the arc in the vicinity of the end face of the optical transmission body from the holding member, the positioning accuracy of the optical transmission body is not impaired.

  In this specification, the “optical transmission body” includes an optical fiber made of glass or resin, an optical waveguide made of resin, or the like. In the following embodiment, an example using an optical fiber will be described. However, the optical transmission body applied in the present invention is not limited to this, and various types of optical transmission lines such as an optical waveguide can be configured. Things can be applied.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 are perspective views showing an optical module according to an embodiment of the present invention. FIG. 1 shows a state in which the optical connection and the electrical connection are disconnected, and FIG. 2 shows a state in which the optical connection and the electrical connection are made. Yes.

  As shown in FIG. 1, the optical module 1 of this embodiment includes an upper structure 5 in which an optical fiber 7 is held by a holding member 6, an optical element mounting substrate 30 on which an optical element 40 is mounted, and an anisotropic conductive sheet. The lower structure 25 which consists of 60, and the fitting member 50 fixed on the wiring board 70 (printed wiring board or board) are provided.

  In this optical module 1, an anisotropic conductive sheet 60 is disposed in an opening 51 in a fitting member 50 on a wiring substrate 70, an optical element mounting substrate 30 is disposed thereon, and an upper structure is further formed thereon. 2 is fitted vertically as shown in FIG. 2, and the optical fiber 7 of the upper structure 5 and the optical element 40 of the optical element mounting substrate 30 are optically connected, and the optical element mounting substrate 30 and the wiring are connected. The substrate 70 is electrically connected via the anisotropic conductive sheet 60. The mounted optical module 1 shown in FIG. 2 constitutes a compact module having a width of 10 mm × 10 mm and a thickness of 6.4 mm, for example.

  3A is a top view of the upper structure 5, FIG. 3B is a bottom view, and FIG. 3C is a side view. In the upper structure 5, a tape fiber 8 in which a plurality of (in this embodiment, 12) optical fibers 7 are arranged in parallel enters the holding member 6 from the back surface of the resin-made holding member 6. Thus, the optical fiber 7 is bent into an arc shape, and the end surface 7a of the optical fiber 7 is vertically exposed from the lower surface of the holding member 6 as shown in FIG.

  A pair of shoulder portions 12 forming a tapered surface along the peripheral edge portion are provided on both peripheral edge portions parallel to the optical fiber 7 on the upper surface of the holding member 6, and are fitted into the fitting member 50 of FIG. 1. The pair of protrusions 52 provided on the upper portion of the fitting member 50 abuts against the shoulder 12 of the holding member 6 and presses downward.

  Further, as shown in FIG. 3B, two positioning holes 11 are provided on the front side of the lower surface of the holding member 6 at symmetrical positions on both side surfaces of the holding member 6. When the optical element mounting substrate 30 is fitted and fitted into the member 50, the positioning pins 42 erected on the optical element mounting substrate 30 are inserted into the positioning holes 11 of the holding member 6 so that the upper structure 5 and the optical element mounting substrate 30 are horizontal. It is positioned in the direction.

  The holding member 6 includes an upper member 10 and a lower member 20 as shown in FIGS. 4A and 4B, and the optical fiber 7 is sandwiched between the upper member 10 and the lower member 20. It comes to hold. As shown in FIG. 4B, guide grooves 14 having a V-shaped cross section, for example, are provided in parallel on the curved surface corresponding to the arc shape of the optical fiber 7 on the lower surface side of the upper member 10. One optical fiber 7 is arranged and guided in each of the guide grooves 14.

  On the other hand, as shown in FIG. 4A, an optical fiber holding surface 22 having a curved surface corresponding to the arc shape of the optical fiber 7 is provided on the upper surface side of the lower member 20, and the upper member 10 and the lower side By sandwiching the optical fiber 7 by the member 20, the optical fiber 7 is held in a state of being bent in an arc shape between the guide groove 14 of the upper member 10 and the optical fiber holding surface 22 of the lower member 20. ing.

  When assembling the upper structure 5, two engaging claws 21 provided on both side surfaces of the lower member 20 are engaged with two engaging holes 13 provided on both side surfaces of the upper member 10. After the upper member 10 and the lower member 20 are fixed to each other, the tip end portion exposed from the tape fiber 8 of the optical fiber 7 and separated into one piece is inserted along the guide groove 14 of the upper member 10. The end face 7a of the optical fiber 7 is aligned using a jig or the like and fixed with an adhesive. FIGS. 5A and 5B show the arrangement of the upper member 10, the optical fiber 7, and the lower member 20 of the upper structure 5 thus manufactured.

  As shown in FIG. 5 (b), the optical fiber 7 held by the holding member 6 is bent into an arc shape, so that the optical axis moves from the horizontal external optical axis 65a downward to the optical element side optical axis 65b. The direction has been changed. The radius of curvature R of the arc portion is preferably 5 mm or less, more preferably 1 to 3 mm. Thus, the radius of curvature R of the arc portion is very small, the vertical direction of the upper structure 5 is reduced in height, and the horizontal direction is also reduced in size. In addition, you may make it provide the linear part of the optical fiber 7 of 500 micrometers or less, for example between the part bent to the circular arc shape of the optical fiber 7, and the end surface 7a.

  Thus, in order to reduce the radius of curvature R of the arc portion of the optical fiber 7, a glass fiber having a diameter of 80 μm is used as the optical fiber 7. The diameter of a glass fiber that is generally used is 125 μm. However, if the glass fiber is bent to a radius of curvature of about 15 to 30 mm, for example, signal light leaks to the outside. However, leakage of signal light to the outside can be suppressed by using the thin glass fiber as described above.

  The outer peripheral portion of the optical fiber 7 is covered with a resin material, so that the thin optical fiber 7 is reinforced. This resin coating is as thin as 22.5 μm, thereby ensuring the accuracy of optical alignment of the optical fiber 7.

  The refractive index ratio between the core and the clad in the optical fiber 7 (core refractive index / cladding refractive index) is preferably 1.5% or higher to increase the refractive index ratio. By setting the refractive index ratio to be high in this way, leakage of signal light to the outside can be further suppressed.

  FIG. 6 is a top perspective view of the optical element mounting substrate 30. The optical element mounting substrate 30 shown in the figure includes a box-shaped ceramic substrate 31 having a wall portion 32 erected along the outer periphery, and the optical fiber 7 and the optical fiber 7 are positioned on the front side of the ceramic substrate 31. The same number of optical elements 40 are mounted side by side. The plurality of optical elements 40 includes a VCSEL as a surface light emitting element and a PIN photodiode as a surface light receiving element. The upper surface 32a of the wall portion 32 forms an optical reference surface, and the end surface 7a of the optical fiber 7 and the optical element 40 are positioned in the vertical direction by contacting the lower surface of the upper structure 5.

  A driver integrated circuit device 41 of the optical element 40 is mounted behind the optical element 40 on the ceramic substrate 31, and the optical element 40 and the driver integrated circuit device 41 are connected by a bonding wire. In addition, other electronic components are mounted on the ceramic substrate 31, and the electronic components on the ceramic substrate 31 are connected to the printed wiring 33 and the like through a through hole that passes through the ceramic substrate 31 (not shown). The electrode is electrically connected to a pad electrode having a pitch of 500 μm, a diameter of 300 to 350 μm, and a height of 10 μm provided on the back surface of the ceramic substrate 31.

  A pair of positioning pins 42 having a protruding height of 2 mm and a protruding portion diameter of 0.7 mm are erected at positions on both sides of the optical element 40 on the ceramic substrate 31, and these positioning pins 42 serve as the upper structure 5. The optical element mounting substrate 30 and the upper structure 5 are positioned in the horizontal direction by being inserted into the positioning holes 11.

  When the optical module 1 is assembled from the state where the optical connection and the electrical connection are disconnected as shown in FIG. 1 to the state where the optical connection and the electrical connection are made as shown in FIG. 2, first, the optical module 1 is fixed on the wiring board 70 of FIG. The anisotropic conductive sheet 60 is disposed in the opening 51 of the fitting member 50 that has been made. Next, the optical element mounting substrate 30 is disposed thereon, and the upper structure 5 is vertically fitted into the fitting member 50 from above.

  At this time, the positioning pins 42 of the optical element mounting substrate 30 are inserted into the positioning holes 11 of the upper structure 5, and the upper structure 5 is in a horizontal direction with respect to the optical element mounting substrate 30 with a predetermined accuracy, for example 3 to 5 μm. In addition, the side surface of the holding member 6 is regulated by the side plate portion 53 of the fitting member 50, and the optical element mounting substrate 30 is indirectly positioned with respect to the wiring substrate 70 in the horizontal direction. Solder bumps having a pitch of 500 μm and a diameter of 300 to 350 μm are formed on the wiring substrate 70, and a pitch of 500 μm and a diameter of 300 to 350 μm provided on the lower surface of the optical element mounting substrate 30 with respect to these solder bumps. The back electrode is aligned.

  Then, the upper structure 5 is pressed downward by the elasticity of the fitting member 50, whereby the anisotropic conductive sheet 60 is pressurized and becomes conductive. Thereby, the back electrode of the optical element mounting substrate 30 and the solder bump on the wiring substrate 70 are electrically connected via the anisotropic conductive sheet 60.

  Further, when the positioning pins 42 of the optical element mounting substrate 30 are inserted into the positioning holes 11 of the upper structure 5, the end surface 7 a of the optical fiber 7 and the optical element 40 are horizontally aligned as shown in the sectional view of FIG. 7. In addition to the positioning of the direction, the lower surface 6a of the holding member 6 and the upper surface 32a of the wall portion 32 of the optical element mounting substrate 30 come into contact with each other, whereby the end surface 7a of the optical fiber 7 and the optical element 40 are perpendicular to each other. Once positioned, they are optically connected.

  At this time, as shown in an enlarged view in FIG. 8, the optical elements 40 arranged on the optical element mounting substrate 30 are electrically connected to the outside via bonding wires 34. When the height of the lower surface is matched with the end surface 7a of the optical fiber 7, the height is, for example, about 70 μm when the end surface 7a of the optical fiber 7 and the optical element 40 are brought close to each other to be optically connected. The lower surface of the upper structure 5 comes into contact with the bonding wire 34.

  Therefore, a space is provided by exposing the inner side of the arc in the vicinity of the end face 7 a of the optical fiber 7 from the holding member 6, and this space is used as a relief portion 75 of the bonding wire 34. The escape portion 75 is formed, for example, by exposing the vicinity of the end face 7a of the optical fiber 7 so that the aspect ratio with the diameter of the optical fiber 7 is about 1: 1. For example, when the optical fiber 7 having a diameter of 125 μm combined with the resin coating is used, it is preferable that the exposure height inside the circular arc of the optical fiber 7 is about 100 μm. If the height of the escape portion 75 is excessively increased, the positioning accuracy of the optical fiber 7 is lowered.

  As described above, the optical module 1 is electrically and optically connected in the vertical direction in the state shown in FIG. 2 and is capable of transmitting and receiving optical signals transmitted to the outside through the optical fiber 7. The

  For example, during maintenance replacement, the optical connection can be easily disconnected by pulling out the upper structure 5 vertically from the fitting member 50, and then the optical element mounting substrate 30 is removed from the anisotropic conductive sheet 60. Electrical connection can be easily disconnected by taking out vertically.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. For example, in the above-described embodiment, the example in which the lower structure 25 is configured by the optical element mounting substrate 30 and the anisotropic conductive sheet 60 has been described. However, in addition, the structure in which the optical element mounting substrate 30 is solder-connected to the wiring substrate 70. Various structures can be adopted.

  In the above embodiment, the upper structure 5 is detachably mounted in the vertical direction using the fitting member 50, and the optical transmission path of the upper structure 5 is optically connected to the optical element 40 of the optical element mounting substrate 30. However, as a mounting body having such a function, an attachment by another mechanism may be used.

  As the optical element 40, a surface light emitting element other than a VCSEL such as a laser diode may be used, or a surface light receiving element other than a PIN photodiode may be used.

FIG. 1 is a perspective view showing an optical module according to an embodiment of the present invention, and shows a state where an optical connection and an electrical connection are disconnected. FIG. 2 is a perspective view showing a state where optical connection and electrical connection are made in the optical module of FIG. 3A and 3B are views showing the upper structure, in which FIG. 3A is a top view, FIG. 3B is a bottom view, and FIG. 3C is a side view. 4A and 4B are diagrams showing an upper member and a lower member of the holding member, wherein FIG. 4A is a perspective view of the upper surface side, and FIG. 4B is a perspective view of the lower surface side. 5A and 5B are views showing the arrangement of the upper member, the optical fiber, and the lower member of the upper structure, in which FIG. 5A is a perspective view and FIG. 5B is a cross-sectional view. FIG. 6 is a perspective view of the optical element mounting substrate. FIG. 7 is a cross-sectional view showing a state where the optical fiber of the upper structure and the optical element of the optical element mounting substrate are optically connected. FIG. 8 is a view showing the periphery of the optical connection portion when the optical fiber of the upper structure and the optical element of the optical element mounting substrate are optically connected.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical module 5 Upper structure 6 Holding member 6a Lower surface 7 Optical fiber 7a End surface 8 Tape fiber 10 Upper member 11 Positioning hole 12 Shoulder part 13 Engaging hole 14 Guide groove 20 Lower member 21 Engaging claw 22 Optical fiber holding surface 25 Lower structure 30 Optical element mounting substrate 31 Ceramic substrate 32 Wall 32a Upper surface 33 Printed wiring 34 Bonding wire 40 Optical element 41 Driver integrated circuit 42 Positioning pin 50 Fitting member 51 Opening 52 Projection 53 Side plate 60 Anisotropic conduction Sheet 65a External side optical axis 65b Optical element side optical axis 70 Wiring board 75 Relief part

Claims (5)

  An optical module that optically connects an optical transmission body that transmits an optical signal and an optical element that converts the optical signal into an electrical signal or converts the electrical signal into an optical signal, and is bent in an arc shape And an optical element mounted with an optical transmission body in which the optical axis on the external side and the optical axis on the optical element side are perpendicular to each other, and a holding member for holding the optical transmission body. The upper structure is positioned so that the optical transmission body of the upper structure is optically connected to the optical element, and the upper structure is disposed on the upper side. An optical module, wherein the optical transmission body and the optical element are optically connected by arranging the end face of the optical transmission body so as to face the optical element when arranged on the top.   The optical module according to claim 1, wherein a radius of curvature of the optical transmission body is 5 mm or less.   The optical module according to claim 1, wherein the optical transmission body is an optical fiber, and an outer peripheral portion of the optical fiber is covered with a resin material.   The optical module according to any one of claims 1 to 3, wherein a refractive index ratio (core refractive index / cladding refractive index) of the core and the clad in the optical transmission body is 1.5% or more.   The optical element mounted on the lower structure is electrically connected to the outside by a bonding wire, and the optical transmission body of the upper structure is exposed from the holding member at the inner side of the arc in the vicinity of the end surface. In this case, a bonding wire escape portion is formed along the exposed region, which is a space in which at least a part of the bonding wire is located when the upper structure is disposed on the lower structure. 5. The optical module according to claim 1, wherein the optical module is characterized in that:

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