The present application claims the benefit of priority to Japanese Patent Application No. 2017-131453, filed on Jul. 4, 2017, the content of which is incorporated herein by reference in its entirety.
The present invention relates to an optical coupling member, and an optical module.
Japanese Unexamined Patent Publication No. JP2000-347072 discloses an optical module where a supporting member into which an optical fiber is inserted is embedded with an optical device. In the optical module, the supporting member positions the optical fiber and the optical device with respect to each other such that an end surface of the optical fiber faces the optical device. In order to improve the position accuracy of the optical fiber with respect to the supporting member in this optical module, a resin in a melted or softened state is prepared, the distal end of the optical fiber is provided therein and is covered therewith, and the supporting member made of the resin in close contact with the optical fiber is formed.
This disclosure provides an optical coupling member. The optical coupling member comprises a main body consisting essentially of glass, and an electrode. The main body comprises a first surface, a second surface opposite to the first surface, and a plurality of holes or grooves each extending from the second surface toward the first surface. The electrode is disposed on the first surface of the main body.
This disclosure also provides an optical module. The optical module comprises the above optical coupling member, and an optical device disposed on the first surface of the main body to face the plurality of holes or grooves.
The foregoing and other purposes, aspects and advantages will be better understood from the following detailed description of embodiments of the invention with reference to the drawings, in which:
The optical module described in JP2000-347072 improves the position accuracy of the optical fiber with respect to the supporting member. However, the supporting member of this module is formed of a resin and the heat resistance of the supporting member is low. Consequently, when the optical module is mounted on a circuit board or the like through reflowing, the supporting member is thermally deformed to cause a strain. Accordingly, the optical module has a possibility that mounted portions exfoliate and members which are included in the optical module and whose heat resistances are low deteriorate. In addition, since the resin generally absorbs sound waves, flip chip bonding through ultrasonic waves whose mounting accuracy is high cannot be used when the optical device is mounted in the supporting member, and thermal flip chip bonding is used instead. Consequently, it is sometimes difficult to embed the optical device on the supporting member accurately. Furthermore, since heat is applied to the supporting member during the reflowing, thermal deformation occurs in the supporting member. Thus, there is a possibility that coupling between the optical fiber held by the supporting member and the optical device cannot be made in conformity with the design, and the coupling efficiency decreases.
The optical coupling member and the optical module according to this disclosure can improve the optical coupling efficiency.
In accordance with an embodiment of the present invention, an optical coupling member of one aspect of the present invention comprises a main body consisting essentially of glass, and an electrode. The main body comprises a first surface, a second surface opposite to the first surface, and a plurality of holes or grooves each extending from the second surface toward the first surface. The electrode is disposed on the first surface of the main body.
In the above optical coupling member, the main body consists essentially of glass. Accordingly, in comparison with a case where a main body is formed of a resin, the heat resistance of the optical coupling member can be improved to make this member resistant to thermal deformation. The heat resistance is thus provided, thereby suppressing the thermal deformation of the main body during mounting the main body on the circuit board or the like through heat application (for example, reflowing or the like). Consequently, the exfoliation of the mounted components and the deterioration of the members whose heat resistances are low are suppressed. In addition, as the material of the main body is glass, absorption of the ultrasonic waves by the main body is suppressed. Accordingly, the optical device can be mounted on the main body using flip chip bonding through ultrasonic waves, for example. The optical device can be accurately mounted on the main body. Thus, this optical coupling member can improve the optical coupling efficiency.
In an embodiment, the plurality of holes or grooves each may have tapered shapes becoming smaller from the second surface toward the first surface. In this aspect, the diameters of the holes or grooves on the second surface can be slightly larger than the diameters of the optical fibers. Consequently, this embodiment prevents the distal ends of the optical fibers from coming into contact with the main body and being chipped when the optical fibers are inserted from the second surface into the holes or grooves.
In an embodiment, inner surfaces of the plurality of holes or grooves may have tapered shapes having an inclination of 1° or more from central axes of the respective holes or grooves. In this aspect, alignment is gradually made when the optical fibers are inserted from the second surface into the respective holes or grooves. Consequently, this embodiment can achieve smooth insertion of the optical fibers.
In an embodiment, the plurality of holes or grooves may each penetrate from the second surface to the first surface. This embodiment can easily form the holes or grooves in the main body.
In an embodiment, the plurality of holes or grooves may extend from the second surface to the middles of the paths reaching the first surface and be non-penetrated. In this aspect, the distal end of the optical fiber can be in contact with the bottom surface of the hole or groove, thereby facilitating the positioning of the optical fiber. Furthermore, this aspect can prevent the distal end of the optical fiber from coming into contact with the optical device. Consequently, the embodiment prevents optical device from being broken or the like.
In an embodiment, the main body may comprise lenses at the distal ends of the respective holes or grooves. In this aspect, the lenses condense light between the optical fibers mounted in the respective holes or grooves in the main body and the optical device disposed on the first surface of the main body. Accordingly, this embodiment can achieve a high optical coupling efficiency.
In an embodiment, the main body may further comprise a positioning hole extending from the second surface toward the first surface. This aspect facilitates the position adjustment with an optical connector that comprehensively holds the plurality of optical fibers, and can easily achieve insertion of the optical fibers into the respective holes or grooves in the main body.
In an embodiment, the main body may have a rectangular shape, and a distance between the first and second surfaces facing each other may be smaller than 2 mm. This embodiment provides a small optical coupling member.
In an embodiment, the first surface may include a recess for arranging the electrode therein, the electrode may be accommodated in the recess so that an outer surface of the electrode may be flush with an outer surface of the first surface other than the recess. This embodiment provides a smaller optical coupling member. Further, when the optical device is mounted on the optical coupling member, the mounting can be easily performed by this embodiment.
In accordance with another embodiment of the present invention, an optical module of one aspect of the present invention comprises the optical coupling member described in the above and an optical device disposed on the first surface of the main body so as to face the plurality of holes or grooves. This aspect provides the optical module comprising the optical device.
In an embodiment, the optical module may further comprise a circuit board, and the optical coupling member may be joined to the circuit board. This embodiment provides the optical module comprising the circuit board.
In an embodiment, the optical module may further comprise a drive circuit driving the optical device. The drive circuit may be mounted on the circuit board, and be electrically connected to the optical device via the electrode. This embodiment provides the optical module comprising the drive circuit.
In an embodiment, the optical module may further comprise a drive circuit driving the optical device. The drive circuit may be accommodated in a recess provided on the outer surface of the main body other than the first and second surfaces, and be electrically connected to the optical device via the electrode. This embodiment can further downsize the optical module, and can treat this module as a module component that integrally includes the drive circuit.
In an embodiment, the optical module may further comprise a plurality of optical fibers arranged in the respective holes or grooves of the optical coupling member. This embodiment provides the optical module comprising the optical fibers.
In an embodiment, the plurality of optical fibers may be fixed to the respective holes or grooves with a photocurable resin adhesive. According to this aspect, since the material of the main body is glass, the plurality of optical fibers can be preferably fixed into the respective holes or grooves with the photocurable resin adhesive.
Hereinafter, an optical module having an optical coupling member according to an embodiment is described in detail with reference to the drawings. The present invention is not limited to these examples, and is indicated by the scope of claims, and meanings equivalent to the scope of claims and all the modifications within the scope are intended to be included. In each drawing, the same or corresponding parts are assigned the same symbols. Redundant description is omitted.
The optical fibers 5 are optically coupled to the optical device 4 by the optical coupling member 3. The outer diameter of the optical fiber 5 may be, for example, about 125 μm, and is an outer diameter substantially equivalent to (slightly smaller than) the diameter of each of holes 33 (see
Next, the details of the optical coupling member 3 are described.
The first surface 3a of the optical coupling member 3 is provided with the plurality of (eight in this embodiment) electrodes 31, and a plurality of (four in this embodiment) mechanical pads 32. The second surface 3b disposed opposite to the first surface 3a of the optical coupling member 3 is provided with a plurality of holes 33 that extend toward the first surface 3a. The plurality of holes 33 each penetrate from the second surface 3b to the first surface 3a. The plurality of holes 33 are holes for allowing the optical fibers 5 to be inserted therein. The plurality of holes 33 are each chamfered on the second surface 3b. However, chamfering is not necessarily applied. The plurality of holes 33 are formed in series along a Y-axis direction. The numbers of electrodes 31, mechanical pads 32 and holes 33 correspond to the number of light receivers or light emitters (hereinafter also represented as “light receiving/emitting devices”) (four light emitters or light receivers in this embodiment), which are included in the optical device 4. One light receiving/emitting device is provided with a pair of electrodes 31, one mechanical pad 32, and one hole 33.
The second surface 3b of the optical coupling member 3 is provided with a pair of positioning holes 34 extending toward the first surface 3a. The positioning holes 34 each penetrate from the second surface 3b to the first surface 3a. The positioning holes 34 are holes for allowing the positioners 513 of the holding member 51 to be inserted thereinto. The positioning holes 34 are each chamfered on the second surface 3b. However, chamfering is not necessarily applied.
The first surface 3a of the main body 30 is provided with a plurality of (eight in this embodiment) recesses 35 for allowing the plurality of electrodes 31 to be arranged thereon. The plurality of recesses 35 extend lower than the holes 33 on the first surface 3a along a Z-axis direction to a lower surface 3c. The plurality of recesses 35 are formed along the Y-axis direction. A pair of recesses 35 correspond to one hole 33. The depth of the concave 35 is equivalent to the thickness of the electrode 31. The plurality of electrodes 31 are accommodated in the respective recesses 35. The outer surfaces of the electrodes 31 accommodated in the respective recesses 35 are flush with the outer surface which is of the first surface 3a and is other than the recesses 35.
The first surface 3a of the main body 30 is provided with a plurality of (four in this embodiment) recesses 36 for allowing the plurality of mechanical pads 32 to be arranged thereon. The plurality of recesses 36 have circular shapes as viewed in an X-axis direction. The plurality of recesses 36 are formed along the Y-axis direction. One recess 36 corresponds to a pair of electrodes 31 and one hole 33. The depth of the recess 36 is equivalent to the thickness of the mechanical pad 32. The plurality of mechanical pads 32 are accommodated in the respective recesses 36. The outer surfaces of the mechanical pads 32 accommodated in the respective recesses 36 are flush with the outer surfaces of the mechanical pads 32 and the outer surface which is of the first surface 3a and is other than the recesses 36.
Here,
The optical device 4 is disposed on the first surface 3a of the optical coupling member 3 such that the plurality of element planes 42 (light emitting regions 46 or light receiving regions) face the respective holes 33 shown in
Cu bumps. The mechanical pads 32 of the optical coupling member 3 and the mechanical pads 45 of the optical device 4 are joined to each other via the bumps 47a, which are, for example, AuSn solder layers using flip chip bonding through ultrasonic waves. Alternatively, joining may be made via bumps 47a made of Au or Cu. The bumps 47b are formed to electrically and mechanically join the electrode pads 44 of the optical device 4 and the electrodes 31 of the optical coupling member 3 to each other, and protrude from the element planes 42 in the X-axis direction by 20 to 30 μm, for example. In the case of using the optical device 4 as shown in
The optical module 1 is fabricated as follows. First, the optical device 4 is joined to the optical coupling member 3 using flip chip bonding through ultrasonic waves. Next, through reflowing, the optical coupling member 3, to which the optical device 4 is joined, is joined to the circuit board 2, and the drive circuit 6 is joined to the circuit board 2. Next, the holding member 51 is attached to the optical coupling member 3, thus constituting the optical module 1. The optical module 1 is joined, as a subassembly, to a separately provided main substrate (not shown), through reflowing. To join the optical module 1 as the subassembly to the main substrate, a ball grid array can be provided on a rear surface of the circuit board 2 opposite to the principal surface 2a, a part of the rear surface can be formed as an edge connector, or a substrate-to-substrate connector or a printed connector can be implemented on the rear surface. The plurality of optical fibers 5 may be preliminarily implemented on the holding member 51 before the holding member 51 is attached to the optical coupling member 3. Alternatively, after the holding member 51 is attached to the optical coupling member 3, the optical fibers 5 may be implemented on the holding member 51.
In the optical module 1 having the configuration described above, for example, the drive circuit 6 that comprises an integrated circuit (IC) is electrically connected to the optical device 4 via the electrodes 61, the electrodes 31 and the electrode pads 44. The light emission of the optical device 4 is controlled by electric signals from the drive circuit 6. In the optical module 1, light from the optical device 4 enters the optical fibers 5. More specifically, first, when drive signals are input into the optical device 4 via the electrodes and the like by the drive circuit 6, light emission is executed by the light emitting regions 46 of the optical device 4, and the light enters the cores of the optical fibers 5. On the other hand, in a case where the optical device 4 is the light receiving device, the light having propagated through the optical fibers 5 enters the optical device 4 which is the light receiving device. The light having entered the optical device 4 is photoelectrically converted by the optical device 4, and electrical signals are output to the drive circuit 6. In the optical module 1, the optical device 4 and the drive circuit 6 are connected to each other via the electrodes 61 and the like on the circuit board 2. The configuration is not that provided with bonding wires between the optical device 4 and the drive circuit 6. Consequently, the device can have a low profile and achieve a high reliability.
The action and effects obtained by the optical module 1 described above are described. In the optical coupling member 3, the material of the main body 30 is glass. That is, the main body is formed of glass. Accordingly, the main body 30 has a higher heat resistance more resistant to thermal deformation than in the case where the material is a resin. When the main body 30 is mounted on the circuit board 2 or the like through reflowing, the thermal deformation of the main body 30 is suppressed. Consequently, the exfoliation of the mounted components and the deterioration of the members whose heat resistances are low are suppressed. As the material of the main body 30 is glass, absorption of the ultrasonic waves by the main body 30 is suppressed. Accordingly, the optical device 4 can be efficiently mounted on the main body 30 using flip chip bonding through ultrasonic waves. Consequently, the optical device 4 can be accurately mounted on the main body 30. Furthermore, the thermal deformation of the main body 30 is suppressed. Consequently, the optical coupling efficiency between the optical fibers 5 mounted into the respective holes 33 of the main body 30 and the optical device 4 arranged on the first surface 3a of the main body 30 is improved. Thus, the optical coupling member 3 can improve the optical coupling efficiency.
In the optical module 1, the plurality of holes 33 each penetrate from the second surface 3b to the first surface 3a. This aspect can easily form the holes 33 in the main body 30.
In the optical module 1, the main body 30 includes the positioning holes 34. This aspect can accurately mount the optical fibers 5 into the respective holes 33 of the main body 30. When the plurality of optical fibers 5 are mounted into the respective holes 33 at the same time, the optical fibers 5 can be easily and reliably mounted into the holes 33.
In the optical module 1, the main body 30 has a rectangular shape, and can be made as a module where the distance between the first and second surfaces 3a and 3b facing each other is less than 2 mm. This aspect provides a small optical coupling member 3.
In the optical module 1, the outer surfaces of the electrodes 31 are flush with the outer surfaces of the first surface 3a other than the recesses 35. This aspect provides a smaller optical coupling member 3. When the optical device 4 is attached to the main body 30, this device can be accurately attached.
Although the embodiment of the present invention has been described, the present invention is not limited to the embodiment described above, and can be modified in a range without departing from the spirit of the present invention. For example, the optical module may have the following configuration. In the following modification example, the points different from those of the embodiment described above are mainly described, and description of the common points is omitted.
The main body 30A is not provided with the positioning holes 34. On the other hand, the first surface 3a of the main body 30A is provided with a plurality (a pair in this embodiment) of non-through holes 37. In the non-through holes 37, protrusions 38 are respectively provided. The non-through holes 37 and the protrusions 38 constitute fiducial marks that serve as references of the position of the main body 30A when the optical device is joined. Note that the fiducial mark is not necessarily formed. Here, the holes 33A serve as the reference of the position of the main body 30A.
As described above, the optical module 1 including such an optical coupling member 3A can allow the light from the optical device 4 (light emitting device) to enter the core of the optical fiber 5, and allow the light from the optical fiber 5 to enter the optical device 4 (light receiving device).
In the optical module 1, the plurality of holes 33A each penetrate from the second surface 3b to the first surface 3a. However, as shown in
As shown in
The lens 39 is provided with a lens surface 39a on a side of the first surface 3a. The lens surface 39a is convex toward the first surface 3a, and has a function of condensing light from the optical device 4 and allowing the light to enter the optical fiber 5. The length of such a lens 39 along the X-axis direction may be, for example, about 200 μm. The outer diameter may be, for example, about 125 μm. To allow the light from the optical device 4 to enter the optical fiber 5 with a high optical coupling efficiency, the optical coupling member 3 is configured so that the central axis L of the hole 33A (the optical axis of the optical fiber 5) and the optical axis of the lens surface 39a of the lens 39 are disposed on the identical axis. In this case, the lenses 39 condense light between the optical fibers 5 mounted in the respective holes 33A in the main body 30A and the optical device 4 disposed on the first surface 3a of the main body 30A. Accordingly, a high optical coupling efficiency can be achieved.
Number | Date | Country | Kind |
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2017-131453 | Jul 2017 | JP | national |