JP2009198923A - Optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical module that is significantly reduced in size, and in which both of optical connection and electric connection are detachably achieved perpendicularly to a wiring board face, and can achieve stable electric connection. <P>SOLUTION: An upper structure 5 having an optical transmission body such as an optical fiber 7, an electronic component mounting substrate 30 mounting an optical element 40 and an anisotropic conductive sheet 60 are fixed by pressing in a perpendicular direction to a wiring board 70 by use of an attachment body such as a fastening member 50 so as to optically connect the optical transmission path of the upper structure 5 with respect to the optical element 40 on the electronic component mounting substrate 30, as well as to electrically connect an under-face pad 34 of the electronic component mounting substrate 30 with a top-face pad 71 of the wiring board 70 via the anisotropic conductive sheet 60. Both of the under-face pad 34 of the electronic component mounting substrate 30 and the top-face pad 71 of the wiring board 70 are protruding from the respective substrate surfaces and have flat faces on the contact faces to the anisotropic conductive sheet 60. <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 carried out on a wiring board (printed wiring board or board) and ease of maintenance and replacement. It is desirable that it is 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).

  However, the optical element is mounted on the wiring board as a whole component such as a board or a package on which a driver integrated circuit device is mounted, for example, and such components are electrically connected to pads on the wiring board. As a general method, there is a connection by reflow of a solder ball such as BGA (Ball Grid Array). However, with such a solder connection method, light is transmitted on a wiring board on which many other components are mounted. When a part on which an element is mounted needs to be repaired and replaced, it is difficult to replace the part or the replacement work becomes complicated.

  Thus, from the viewpoints of workability for maintenance and replacement and securing of mounting density on the wiring board, not only optical connection but also electrical connection can be attached to and detached from the wiring board vertically, and a structure that can be easily attached and detached is desired. It was. Furthermore, further miniaturization of the optical module itself is desired from the viewpoint of improving the mounting density, and it is also desired to produce a product that satisfies these requirements at a low cost.

In order to solve such problems, the present inventors have disclosed an optical transmission body that forms a continuous optical transmission path in which the optical axis on the outside side and the optical axis on the optical element side are perpendicular to each other, and the optical transmission body An electronic component mounting in which an upper structure including a holding member that holds the optical element and an electronic component including an optical element are mounted on the upper surface and a pad that is electrically connected to an electrode of the electronic component through a through hole is provided on the lower surface By pressing and fixing the substrate and the anisotropic conductive sheet with a mounting body such as a clamp spring installed on the wiring substrate, the optical transmission path of the upper structure is made to the optical element of the electronic component mounting substrate. An optical module having a structure in which the pads on the lower surface of the electronic component mounting substrate and the pads on the upper surface of the wiring substrate are electrically connected via an anisotropic conductive sheet while being optically connected is proposed (see Patent Document 2). ).
JP 2006-65358 A Japanese Patent Application No. 2007-217574

  According to the above optical module, it is possible to greatly reduce the size, and it is possible to attach and detach both the optical connection and the electrical connection perpendicularly to the wiring board surface. There was room for further improvement.

  The present invention has been made in view of the circumstances as described above, and is greatly reduced in size, and both optical connection and electrical connection can be attached to and detached from the wiring board surface vertically, and is stable. It is an object of the present invention to provide an optical module that can be electrically connected.

  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 line 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 electronic component including an optical transmission body and an upper structure including a holding member for holding the optical transmission body, a wiring board provided with a pad on an upper surface, an anisotropic conductive sheet, and an optical element. An electronic component mounting board mounted on the upper surface and electrically connected to an electrode of the electronic component on the lower surface, and an upper structure, the electronic component mounting board, and an anisotropic conductive sheet on the wiring board. By pressing and fixing in the vertical direction, the optical transmission path of the upper structure is optically connected to the optical element of the electronic component mounting substrate, and the lower pad of the electronic component mounting substrate and the upper pad of the wiring substrate And through an anisotropic conductive sheet And a pad on the lower surface of the electronic component mounting board and a pad on the upper surface of the wiring board both project from the board surface, and the contact surface to the anisotropic conductive sheet is a flat surface. It is characterized by being.

Second, in the first optical module, the vertical pressing force by the mounting body on the anisotropic conductive sheet sandwiched between the electronic component mounting board and the wiring board is 0.5 kgf / cm ² or more. It is characterized by.

  Thirdly, in the first or second optical module, the protruding height of the pad on the lower surface of the electronic component mounting substrate and the pad on the upper surface of the wiring substrate is 20 μm or more.

  According to the first aspect of the present invention, both optical connection and electrical connection can be attached / detached perpendicularly to the wiring board surface, and can be disconnected both optically and electrically at the time of maintenance and replacement. Therefore, maintenance replacement and the like are easy, and it is not necessary to provide a work space for attachment and detachment around the electronic component mounting board, so that the mounting density on the wiring board can be increased and high While the components are mounted at a high density, it is possible to improve the selectivity and expandability of the place where the user places the optical module on the wiring board. And by setting it as said structure, an optical module can be significantly reduced as a whole and an optical module can be manufactured at low cost.

  Furthermore, the pads on the lower surface of the electronic component mounting substrate and the pads on the upper surface of the wiring substrate are both projected from the substrate surface, and the contact surface to the anisotropic conductive sheet is a flat surface. The entire surface can be sufficiently brought into contact with the anisotropic conductive sheet, and a stable electrical connection can be achieved during operation of the optical module.

According to the second aspect of the present invention, the pressing force in the vertical direction by the mounting body on the anisotropic conductive sheet sandwiched between the electronic component mounting substrate and the wiring substrate is 0.5 kgf / cm ² or more. The surface contact of the pad on the lower surface of the component mounting board and the pad on the upper surface of the wiring board with the anisotropic conductive sheet can be sufficiently secured, and more stable electrical connection can be achieved during the operation of the optical module.

  According to the third invention, the protrusion height of the pads on the lower surface of the electronic component mounting board and the pads on the upper surface of the wiring board is set to 20 μm or more. It is possible to ensure sufficient contact with the biting surface and to prevent contact failure due to warpage of the substrate. That is, since the height variation in the substrate surface direction can be sufficiently absorbed, more stable electrical connection can be achieved during the operation of the optical module.

  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.

  In the present specification, the “optical element” includes not only one having a single light receiving / emitting surface but also one having a plurality of light receiving / emitting surfaces arranged in an array or the like. Specific examples of the optical element include a surface light emitting element such as a VCSEL and a surface light receiving element such as a PIN photodiode. The surface light emitting elements and / or the light receiving and emitting surfaces of the surface light receiving elements are arranged in an array. It may be integral.

  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 electronic component mounting board 30 on which an optical element 40 is mounted, and anisotropic conductivity. A sheet 60, a wiring board 70 (printed wiring board or board), and a fitting member 50 fixed on the wiring board 70 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 electronic component mounting substrate 30 is disposed thereon, and an upper structure is 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 electronic component mounting substrate 30 are optically connected, and the electronic component 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.

  As shown in FIGS. 3A and 3B, the upper structure 5 includes a plurality of (in this embodiment, 12) optical fibers 7 arranged in parallel from the back surface of the resin holding member 6. The tape fiber 8 enters the holding member 6 horizontally, the optical fiber 7 is bent in an arc shape in the holding member 6, and the end face 7 a of the optical fiber 7 is vertically exposed from the lower surface of the holding member 6. Yes.

  As shown in FIG. 1, a pair of shoulder portions 12 that form 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. When the fitting member 50 is fitted and attached, the pair of protrusions 52 provided on the upper part of the fitting member 50 abuts against the shoulder 12 of the holding member 6 and presses downward.

  Further, as shown in FIG. 1, the holding member 6 is provided with two positioning holes 11, which are erected on the electronic component mounting substrate 30 when fitted into the fitting member 50 of FIG. The positioning pins 42 thus inserted are inserted into the positioning holes 11 of the holding member 6 so that the upper structure 5 and the electronic component mounting board 30 are positioned in the horizontal direction.

  The holding member 6 includes an upper member 10 and a lower member 20 as shown in FIGS. 3A and 3B, and the optical fiber 7 is sandwiched between the upper member 10 and the lower member 20. It comes to hold. On the lower surface side of the upper member 10, guide grooves having a V-shaped cross section, for example, are provided in parallel on a curved surface corresponding to the arc shape of the optical fiber 7, and the optical fiber 7 is 1 in each of these guide grooves. Each book is arranged and guided. On the other hand, an optical fiber holding surface 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 by sandwiching the optical fiber 7 between the upper member 10 and the lower member 20, The optical fiber 7 is held in a state bent in an arc shape between the guide groove of the upper member 10 and the optical fiber holding surface of the lower member 20.

  The radius of curvature R of the arc portion between the outer optical axis 65a and the optical element side optical axis 65b of the optical fiber 7 is preferably 5 mm or less, more preferably 1 to 3 mm. Thus, the radius of curvature of the arc portion is very small, the vertical direction of the upper structure 5 is reduced, and the horizontal direction is also reduced in size. As the optical fiber 7, for example, a glass fiber having a diameter of 80 μm can be used.

  4 is a top perspective view of the electronic component mounting board, FIG. 5 is a cross-sectional view showing a state where the upper structure and the electronic component mounting board are optically connected, and FIG. 6 shows the lower surface of the electronic component mounting board. 7 and 7 are enlarged cross-sectional views of pads on the lower surface of the electronic component mounting substrate. As shown in FIG. 4, the electronic component mounting substrate 30 includes a box-shaped ceramic substrate 31 in which a wall portion 32 is erected along the outer peripheral portion, and a light is placed at a front position on the ceramic substrate 31. An optical element 40 in which the same number of light receiving and emitting surfaces as the fiber 7 are arranged is mounted.

  The electronic component mounting board 30 mounts electronic components such as the optical element 40 and the driver integrated circuit device 41 in a cavity surrounded by the wall portion 32.

  The optical element 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 constitutes an optical reference surface, and comes into contact with the lower surface of the upper structure 5 so that the end surface 7a of the optical fiber 7 and the optical element 40 are vertically aligned as shown in FIG. Positioned.

  As shown in FIG. 4, 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. By inserting the positioning pins 42 into the positioning holes 11 of the upper structure 5, the electronic component mounting substrate 30 and the upper structure 5 are positioned in the horizontal direction.

  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 electrodes of the electronic components on the ceramic substrate 31 penetrate the ceramic substrate 31 directly below the electronic components or via the printed wiring 33 or the like. The through holes 35 are electrically connected to the pads 34 shown in FIGS. 6 and 7 provided on the lower surface of the ceramic substrate 31.

  As shown in FIG. 7, the pad 34 protrudes downward from the lower surface of the ceramic substrate 31, and the tip is a flat surface 34a. The diameter d of the pad 34 is, for example, 300 to 350 μm, and the protruding height h from the ceramic substrate 31 is preferably 20 μm or more, more preferably 50 μm or more. For example, the pad 34 is disposed on the lower surface of the ceramic substrate 31 with a pitch of 500 μm. .

  8 and 9 are cross-sectional views showing a state before and after electrical connection of the electronic component mounting board, the anisotropic conductive sheet, and the wiring board. FIG. 8 shows a state before electrical connection, and FIG. 9 shows a state after electrical connection. Show. As shown in the figure, the electronic component mounting board 30 is electrically connected to the wiring board 70 via an anisotropic conductive sheet 60.

  The anisotropic conductive sheet 60 ensures conduction in the vertical direction by pressurization, and various kinds of sheets can be used without particular limitation. For example, the anisotropic conductive sheet 60 can be used as an insulating base material having elasticity such as silicone rubber. A conductive wire 61 embedded therein can be used. The thickness of the anisotropic conductive sheet 60 is, for example, 0.1 to 1 mm.

  The upper surface of the wiring board 70 is provided with a pad 71 serving as an electrode for wiring on the board. The pad 71 has the same shape as the pad 34 of the electronic component mounting board 30 and protrudes upward from the board surface. The leading end is a flat surface 71a. The diameter of the pad 71 is, for example, 300 to 350 μm, and the protruding height from the wiring board 70 is preferably 20 μm or more, more preferably 50 μm or more. For example, the pad 71 is arranged on the upper surface of the wiring board 70 with a pitch of 500 μm.

  When assembling the optical module 1 having the above configuration from the state in which the optical connection and the electrical connection are disconnected as shown in FIG. 1 to the state in which the optical connection and the electrical connection are made as shown in FIG. An anisotropic conductive sheet 60 is disposed in the opening 51 of the fitting member 50 fixed on the wiring board 70. Next, the electronic component mounting board 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 electronic component mounting board 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 electronic component mounting board 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 electronic component mounting substrate 30 is indirectly positioned in the horizontal direction with respect to the wiring substrate 70. As a result, as shown in FIG. 9, the pads 34 on the lower surface of the electronic component mounting substrate 30 are aligned with the pads 71 on the upper surface of the wiring board.

  Then, the upper structure 5 is pressed downward by the elasticity of the fitting member 50, thereby pressing the anisotropic conductive sheet 60, and the pads 34 and the wiring board of the electronic component mounting board 30 as shown in FIG. 9. The pad 71 is sufficiently brought into contact with the anisotropic conductive sheet 60 over the projected flat surfaces 34a and 71a, and becomes conductive. Thereby, the pads 34 of the electronic component mounting board 30 and the pads 71 of the wiring board 70 are electrically connected via the anisotropic conductive sheet 60.

Also, the positioning pins 42 of the electronic component mounting board 30 of FIG. 1 are inserted into the positioning holes 11 of the upper structure 5, whereby the end face 7 a of the optical fiber 7 and the optical element 40 as shown in the cross-sectional view of FIG. 5. And 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 are in contact with each other, so that the end surface 7a of the optical fiber 7 and the optical element 40 are in contact with each other. They are positioned vertically and connected optically. The pressing force in the vertical direction by the fitting member 50 on the anisotropic conductive sheet 60 sandwiched between the electronic component mounting substrate 30 and the wiring substrate 70 is sufficient contact between the anisotropic conductive sheet 60 and the pads 34a and 71a. From the point of securing the electrical connection, it is preferably 0.5 kgf / cm ² or more, more preferably 1 kgf / cm ² or more.

  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 embodiment, the upper structure 5 is detachably mounted in the vertical direction using the fitting member 50 as the mounting body, and the light of the upper structure 5 is attached to the optical element 40 of the electronic component mounting substrate 30. Although the transmission line is optically connected, various types of mounting structures such as a clamp spring, a screwing structure, a leaf spring structure, a latch structure, and an open / close clamp spring can be used. it can.

  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.

  The optical element 40 and the driver integrated circuit device 41 may be flip-chip connected to the electronic component mounting board 30.

  As the anisotropic conductive sheet 60, various kinds of sheets can be used without particular limitation as long as the conduction in the vertical direction is ensured by pressurization. For example, as shown in FIG. A pad 34 of the electronic component mounting board 30 and a pad of the wiring board 70 are pressed by a mounting body in the vertical direction using an anisotropic conductive sheet 60 in which conductive particles 62 such as metal are dispersed in an insulating base material. 71 may be electrically connected via an anisotropic conductive sheet 60.

  The flat surfaces 34a and 71a of the pads 34 of the electronic component mounting board 30 and the pads 71 of the wiring board 70 may be subjected to Au plating, Ni / Au plating, or the like.

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 arrangement of the upper member, the optical fiber, and the lower member of the upper structure, in which FIG. 3A is a perspective view and FIG. 3B is a cross-sectional view. FIG. 4 is a top perspective view of the electronic component mounting board. FIG. 5 is a cross-sectional view showing a state in which the upper structure and the electronic component mounting substrate are optically connected. FIG. 6 is a view showing the lower surface of the electronic component mounting board. FIG. 7 is an enlarged cross-sectional view of a pad on the lower surface of the electronic component mounting board. FIG. 8 is a cross-sectional view showing a state before electrical connection of the electronic component mounting board, the anisotropic conductive sheet, and the wiring board. FIG. 9 is a cross-sectional view showing a state in which the electronic component mounting substrate, the anisotropic conductive sheet, and the wiring substrate are electrically connected. FIG. 10 is a cross-sectional view showing a state before electrical connection of the electronic component mounting board, the anisotropic conductive sheet, and the wiring board. FIG. 11 is a cross-sectional view showing a state in which the electronic component mounting board, the anisotropic conductive sheet, and the wiring board are electrically 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 20 Lower member 30 Electronic component mounting substrate 31 Ceramic substrate 32 Wall part 32a Upper surface 33 Printed wiring 34 Pad 34a Flat surface 35 Through hole 40 Optical element 41 Driver integrated circuit device 42 Positioning pin 50 Fitting member 51 Opening portion 52 Projection portion 53 Side plate portion 60 Anisotropic conductive sheet 61 Conductive wire 62 Conductive particle 65a External side light Shaft 65b Optical element side optical axis 70 Wiring board 71 Pad 71a Flat surface

Claims (3)

  An optical module that optically connects an optical transmission path for transmitting 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, the optical transmission body and the optical transmission An upper structure having a holding member for holding the body, a wiring board provided with a pad on the upper surface, an anisotropic conductive sheet, and an electronic component including an optical element are mounted on the upper surface and used as an electrode of the electronic component. By pressing and fixing the electronic component mounting board provided with the electrically connected pads on the lower surface, the upper structure, the electronic component mounting board, and the anisotropic conductive sheet on the wiring board in the vertical direction, The optical transmission path of the upper structure is optically connected to the optical element of the electronic component mounting substrate, and the lower surface pad of the electronic component mounting substrate and the upper surface pad of the wiring substrate are electrically connected via an anisotropic conductive sheet. With an attached body Cage, the lower surface of the pad and the wiring upper surface of the pad of the substrate of the electronic component mounting board, an optical module, characterized in that both contact surfaces of the substrate surface to the anisotropic conductive sheet protrudes is a flat surface. ^2. The optical module according to claim 1, wherein the pressing force in the vertical direction by the mounting body on the anisotropic conductive sheet sandwiched between the electronic component mounting board and the wiring board is 0.5 kgf / cm ² or more. .   3. The optical module according to claim 1, wherein the protrusion height of the pad on the lower surface of the electronic component mounting substrate and the pad on the upper surface of the wiring substrate is 20 μm or more.

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