JP2008041772A - Optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical interconnection module having at least one of a surface light emitting element and a surface light receiving element, and capable of making compact and thin while reducing transmission loss of high frequency electric signal in the module. <P>SOLUTION: A flexible substrate 2 mounting a VCSEL 3 is bent with a curvature larger than a predetermined value, wherein the diameter at the bend of the flexible substrate 2 is larger than the level difference between the surface at a portion of the flexible substrate 2 mounting the VCSEL 3 and the surface at a portion for making electrical connection with a circuit board 19. At the bend of the flexible substrate 2, the level difference between a portion closest to the circuit board 19 and the surface for making electrical connection with the circuit board 19 is smaller than the level difference between a portion farthest from the circuit board 19 and the surface mounting the VCSEL 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to the structure of an optical module used for intra-device optical interconnection.

In recent years, with the expansion of broadband networks, the amount of information transmitted and received via the network has increased, and it has been demanded to improve the information processing capacity inside information devices such as routers and servers.
However, the limit of the transmission speed of the electric board used in the information equipment does not increase compared to the increase in network traffic and the progress of the processing speed of the signal processing LSI (CPU, switch, etc.), and the information processing capacity It has become an obstacle to improve.

  In order to overcome this obstacle and further improve the information processing capacity inside the information equipment, the ports accommodated in the equipment or between the LSIs mounted on the board are interconnected by optical signals, that is, “ “Intra-device optical interconnection” is effective.

In order to realize in-device optical interconnection, an optical module that converts an electrical signal processed by an LSI into light is required. However, an optical module for in-device optical interconnection is a conventional optical module for communication. More compact, higher integration, lower cost, and lower power consumption are required.
For this reason, the VCSEL (Vertical Cavity Surface Emitting Laser) is used as a light emitting element used in an optical module for in-device optical interconnection, instead of the edge-emitting laser diode used in the conventional optical module. Laser) is advantageous and is expected to be widely applied.

Several mounting structures have been proposed for assembling a small and thin optical module to which a VCSEL is applied at low cost. One of them is “a photoelectric composite module and an optical input / output device including the module as a constituent element” disclosed in Patent Document 1.
As shown in FIG. 5, the invention disclosed in Patent Document 1 mounts an optical element 72 and a driver IC 73 on a transparent plate 74 using metal bumps 76, and transmits light emitted from the VCSEL 72 to the transparent plate 74. Then, the light is condensed by an optical coupling member (lens or the like) (not shown) and coupled to the optical transmission path.

  The advantage of this structure is that a metal plate 76 connects flip-chip bonding, that is, an element and a substrate, having a characteristic of low high-frequency loss to a transparent plate 74 in which a line having good high-speed signal transmission characteristics is formed using a low dielectric constant material. By mounting the optical element 72 and the driver IC 73 by the joining method, the high frequency characteristics of the optical module can be improved.

When an optical module including a mounting structure in which the optical element 72 and the driver IC 73 are mounted on the transparent plate 74 is mounted on a circuit board and the light is input and output upward, the VCSEL and the driver IC are placed under the flexible board. Since joining is performed, a height difference equal to or greater than the chip thickness of the VCSEL or driver IC occurs at least between the flexible substrate and the circuit substrate. In order to electrically connect the flexible substrate having a height difference and the circuit substrate, a transparent flexible sheet 111 as shown in FIG. Patent Document 2 discloses a structure that can be bent into a square shape and connected to a circuit board (not shown).
JP 2004-31508 A JP 2006-5192 A

  However, in the structure shown in FIG. 6, since the flexible substrate through which the high-speed signal passes is bent substantially at right angles at two locations to form a “U” shape, there is a concern that transmission loss may occur at the bent portion. Therefore, in order to prevent transmission loss, a method of bending the flexible substrate in a curved shape as shown in FIG. 7 can be considered.

  However, even if it is bent into a curved surface, if the curvature of the bent part is small, the effect of reducing transmission loss is small, and it becomes difficult to mount components on the side part. Therefore, in order to reduce transmission loss and mount components on the bent portion, it is necessary to make the curvature large to some extent. As a result, the height difference between the surface of the flexible substrate on which the VCSEL or the driver is mounted and the surface to be joined to the circuit substrate increases, and the thickness dimension of the optical module increases.

  That is, in an optical module having a structure in which a VCSEL or other surface emitting light-receiving element is mounted on a flexible substrate and the flexible substrate is bent and joined to a circuit board, transmission loss of high-frequency electrical signals inside the module is prevented, and the module is compact. It has been difficult to achieve both reduction in thickness and thickness.

  The present invention has been made in view of such problems, and includes an optical interface that includes at least one of a surface light emitting element and a surface light receiving element, reduces transmission loss of a high-frequency electric signal inside the module, and can be reduced in size and thickness. The purpose is to provide a connection module.

  In order to achieve the above object, according to the present invention, as a first aspect, at least one of a surface light emitting element and a surface light receiving element, and at least one of the surface light emitting element and the surface light receiving element are electrically connected to a circuit board. An optical module having a flexible substrate, wherein the flexible substrate is mounted with at least one of a surface light emitting element and a surface light receiving element, and is bent with a curvature larger than a predetermined value, and a diameter of a bent portion of the flexible substrate Is larger than the difference in height between the surface of the portion of the flexible substrate on which at least one of the surface light emitting element and the surface light receiving device is mounted and the portion that makes electrical connection with the circuit board, The part is the part farthest from the circuit board than the difference in height between the part closest to the circuit board and the surface that makes electrical connection with the circuit board. There is provided an optical module characterized in that the larger height difference between the at least one by the mounting portion of the surface of the surface light-emitting device and the surface light-receiving device and.

  In order to achieve the above object, as a second aspect, the present invention provides an electrical connection between at least one of the surface light emitting element and the surface light receiving element, at least one of the surface light emitting element and the surface light receiving element, and the circuit board. An optical module having a flexible substrate having a contact point and a plate-like support member having a curved surface on at least a part of a side surface, wherein at least one of the surface light emitting element and the surface light receiving element is electrically And is bent along the side surface of the support member and fixed to the support member. The diameter of the bent portion is a surface on which at least one of the flexible substrate, the surface light emitting element, and the surface light receiving element is mounted. Greater than the difference in height between the surface and the part that makes electrical connection with the circuit board, and the bent part of the flexible board is closest to the circuit board The difference in height between the part farthest from the circuit board and the surface of the part on which at least one of the surface light emitting element and the surface light receiving element is mounted is larger than the difference in height between the part and the part that electrically connects the circuit board. An optical module characterized by the above is provided.

  In the second aspect of the present invention, the support member is preferably made of a metal material, and at least one of the surface light emitting element and the surface light receiving element is preferably in contact with the support member. Alternatively, the support member is preferably made of a dielectric material. Alternatively, in the support member, it is preferable that a portion along the flexible substrate is formed of a dielectric material, and a portion where at least one of the surface light emitting element and the surface light receiving element is in contact with a metal material.

  In any of the above-described configurations of the first and second aspects of the present invention, the flexible substrate is bent so that it is formed between a portion that is electrically connected to the circuit board and a portion that is farthest from the circuit board. It is preferable that an electronic component is mounted on the side portion.

In the first or second aspect of the present invention, the flexible substrate on which the surface light-emitting element or the surface light-receiving element is mounted is bent by approximately 180 degrees into a curved surface and joined to the circuit board to thereby remove the surface light-emitting element or the surface light-receiving element. High-speed electrical wiring between circuit boards can be achieved with low loss.
In addition to this, the diameter of the bent portion of the flexible substrate is set to be larger than the height difference between the surface of the flexible substrate where the surface light emitting element or the surface light receiving element is mounted and the surface where the circuit board is electrically connected. Accordingly, the curvature of the bent portion can be increased and the portion on which the surface light emitting element or the surface light receiving element is mounted can be thinned. For this reason, components such as a lens and an optical connector receptacle are mounted on the portion on which the surface light emitting element or the surface light receiving element is mounted, so that the height of the entire optical module can be kept low. Furthermore, by increasing the curvature of the bent portion, it becomes easy to mount components on the side portion that appears by bending.

  In addition, as in the second aspect, the shape of the flexible substrate can be stabilized by bending the flexible substrate into a curved shape along the curved surface of the plate-like support member having a curved surface at the side surface portion. In addition, the support member is made of a metal material and the surface light emitting element or the surface light receiving element is in contact with the support member, so that heat from the surface light emitting element or the surface light receiving element can be radiated through the support member.

  In addition, when the support member is made of metal, in order to stably maintain the transmission characteristics of the high-speed signal transmission line on the flexible substrate, the distance between the transmission line and the support member is controlled with high accuracy to form a strip line. In this state, it is necessary to bend the flexible substrate along the curved surface of the support member, and a difficult case is assumed. On the other hand, if the support member is made of a dielectric material as in the second aspect of the present invention, the high-speed signal transmission line is not a strip line structure with a metal support member, for example, a coplanar line is formed. As a result, stable signal transmission characteristics can be obtained more easily than when the support member is made of metal.

  However, if all of the support members are made of a dielectric material, most of the dielectric materials generally have low thermal conductivity, so that the heat dissipation characteristics from the light emitting element are deteriorated. On the other hand, the material of the support member is made of a dielectric only in the portion of the flexible substrate along the high-speed signal transmission line, and made of metal in the portion in contact with the surface light emitting element, so that the high-speed transmission line having stable high-frequency characteristics. And the heat dissipation from the light emitting element can be achieved. In addition, by increasing the bending radius of the flexible substrate, it is possible to mount electronic components on the side surface that appears by bending the flexible substrate. Thereby, size reduction of a module can be achieved.

  According to the present invention, it is possible to provide an optical interconnection module that includes at least one of a surface light emitting element and a surface light receiving element, reduces transmission loss of a high-frequency electric signal inside the module, and can be reduced in size and thickness.

[First Embodiment]
A first embodiment in which the present invention is suitably implemented will be described.
FIG. 1 is a perspective view of an optical module according to the present embodiment. A light incident / exit portion 51 is provided on the upper surface of the optical module 1, and guide pins 52 are disposed on both sides of the light incident / exit portion 51. The optical module 1 and the optical connector 13 are optically connected by inserting and fitting the guide pins 52 into the guide holes 53 provided on the optical connector 13 side.

Since circuit boards mounted on an information processing apparatus are mounted in a stack, there are many restrictions on the height of components to be mounted. Therefore, in order to realize in-device optical interconnection, it is desirable that the fiber take-out direction to the optical module mounted on the circuit board is parallel to the circuit board.
Further, securing a dead space for inserting and removing a connector around the optical module is disadvantageous when components are mounted on the circuit board at a high density. Therefore, it is desirable that the optical connector 13 is inserted and removed in a direction perpendicular to the circuit board.
In order to meet these requirements, the optical connector 13 includes a right-angle optical path conversion unit.

  FIG. 2 shows a cross section of the optical module according to the present embodiment. The illustrated surface is a cross section taken along line A-A ′ in FIG. 1 in a state where the optical module 1 and the optical connector 13 are connected.

  In the optical module 1, a VCSEL 3, a driver IC 5, and a chip capacitor 7 are mounted on the lower surface of a flexible substrate 2 made of a polymer material. The joining of the VCSEL 3 or the driver IC 5 and the flexible substrate 2 can be realized, for example, by joining a gold stud bump and a solder or conductive paste applied on a pad on the flexible substrate 2.

  In a portion where the VCSEL 3 and the driver IC 5 are mounted on the flexible substrate 2, an underfill 6 is interposed in the gap between these elements and the flexible substrate 2. The underfill 6 has adhesiveness and functions to reinforce the bonding strength between these elements and the flexible substrate 2. As a material for the underfill 6, an epoxy resin or the like is generally used.

  Solder bumps 8 for joining to the circuit board 19 are also formed on the flexible board 2. As the material of the solder bump 8, an alloy made of a metal material selected from a plurality of tin, gold, silver, lead, bismuth and the like is used. In the region in contact with the circuit board 19, the solder resist 9 is applied to portions other than the predetermined positions where the solder bumps 8 are formed, so that the adhesion of solder to unnecessary portions is prevented.

  The pad on which the chip capacitor 7 is mounted and the solder bump 8 are connected by a signal transmission line 11 and a via 17. The flexible printed circuit board 2 is bent approximately 180 degrees in a curved shape at two positions on the left and right sides of the figure, and the surface on which the VCSEL 3 and the driver IC 5 are mounted and the surface on which the solder bumps 8 are formed are substantially parallel to each other while maintaining a predetermined height difference. It is comprised so that it may become.

In the portion of the flexible substrate 2 where the signal transmission line 11 is bent, the space between the upper lid 10 and the circuit substrate 19 is widened, and the diameter of the bent portion includes the VCSEL 3 and the driver IC 5. The surface is inflated so as to be larger than the height difference between the surface and the surface on which the solder bumps 8 are formed.
That is, the flexible substrate 2 has a large bending curvature without increasing the height difference between the surface on which the VCSEL 3 and the driver IC 5 are mounted and the surface on which the solder bumps 8 are formed.

  As a result, since the bending curvature of the flexible substrate 2 can be expanded without increasing the overall height of the module 1 and the optical connector 13, the connector is connected to the module. It is possible to achieve both a reduction in thickness and prevention of loss due to bending of high-speed signal lines.

On the upper surface of the flexible substrate 2, the optical axis of the lens of the flat microlens array 12 fixed to the upper lid 10 made of metal is positioned and bonded and fixed so that the optical axis of the VCSEL 3 is aligned.
As the flat microlens array 12, for example, a flat glass material or a resin material in which a plurality of curved protrusions are formed in an array shape can be applied. The optical connector 13 is connected to the upper surface of the optical module 1, and the positioning of the optical module 1 and the optical connector 13 is performed by the guide pins 52 shown in FIG. The optical connector 13 is provided with a 45-degree mirror 14 that changes the optical path of the outgoing light from the VCSEL 3 at a right angle and enters the optical fiber. As the optical fiber 16, for example, a multimode fiber made of quartz or a polymer material can be applied.

  The lower edge of the upper lid 10 is joined to the circuit board 19 by a solder material 18. As a result, the module 1 is fixed to the circuit board 19 and at the same time, unnecessary electromagnetic radiation from the signal transmission path can be shielded by the side surface of the upper lid 10.

The operation of the optical module according to this embodiment will be described.
When a high-speed electrical signal is input from the circuit board 19 to the optical module 1 through the solder bump 8, the signal is input to the driver IC 5 through the signal transmission line 11 and the chip capacitor 7 on the flexible substrate 2. The electric signal reaching the driver IC 5 is amplified by the driver IC 5 and output toward the VCSEL 3. The electrical signal that has reached the VCSEL 3 is converted into an optical signal by the VCSEL 3. By connecting the optical connector 13 and the optical module 1, the upward emitted light 15 from the VCSEL 3 is collected by the flat microlens array 12, and the collected light is changed in the horizontal direction by the 45-degree mirror 14. And enters the optical fiber 16. When a surface light receiving element is used instead of the VCSEL 3, the light path is changed in the vertical direction by the 45-degree mirror 14 emitted from the optical fiber 16, and is incident on the surface light receiving element.

With such a configuration, the transmission path loss of the high-speed electric signal wiring between the surface light emitting element or the surface light receiving element and the circuit board can be kept low.
Further, even when a component such as a lens or an optical connector releasable is mounted on the portion on which the surface light emitting element or the surface light receiving element is mounted, the height of the entire optical module can be kept low. Furthermore, by increasing the curvature of the bent portion, it becomes easy to mount components on the side portion that appears by bending.

[Second Embodiment]
A second embodiment in which the present invention is suitably implemented will be described. FIG. 3 shows the configuration of the optical module according to this embodiment. The flexible substrate 2 is bent into a curved surface along curved surfaces provided on two side surfaces of the support member 20. The support member 20 is made of a metal such as copper, aluminum, copper-tungsten alloy, brass, or stainless steel, but the portion of the flexible substrate 2 where the signal transmission line 11 is formed is bent along a curved surface such as an epoxy resin. The dielectric material 21 is used.

  By applying such a structural device, the signal transmission line 11 is not affected by the support member 20, and high-speed signal transmission with little loss is possible.

  The flexible substrate 2 is bonded and fixed to the support member 20 with an epoxy-based adhesive or the like while being bent into a curved surface along the curved surface provided on the support member 20, or the flexible substrate 2 has adhesiveness and is supported. Adhering and fixing to the member 20.

  The surfaces of the VCSEL 3 and the driver IC 5 opposite to those on which the bumps 4 are formed are in contact with the support member 20 via the heat radiating gel 22 so that heat conduction is performed. Thereby, the heat generated from the VCSEL 3 and the driver IC 5 is efficiently released to the support member 20. As the heat dissipating gel 22, a silicone-based resin filled with a filler such as aluminum oxide can be used.

  Since other configurations and operations are the same as those in the first embodiment, a redundant description is omitted.

  The shape of the flexible substrate 2 can be stabilized by bending the flexible substrate 2 into a curved surface along the curved surface of the plate-like support member 20 having a curved surface at the side surface.

  The support member 20 is formed of a metal material, and the surface light-emitting element or the surface light-receiving element is in contact with the support member 20 (via the heat radiating gel 22), whereby heat from the surface light-emitting element is transmitted through the support member 20. Dissipate heat.

However, when the support member 20 is made of metal, in order to stably maintain the transmission characteristics of the high-speed signal transmission line on the flexible substrate 2, the distance between the transmission line and the support member 20 is controlled with high accuracy, and the strip It is necessary to bend the flexible substrate 2 along the curved surface of the support member 20 in a state where the line is formed.
On the other hand, by forming the support member 20 from a dielectric material, for example, by forming a coplanar line, stable signal transmission characteristics can be obtained more easily than when the support member 20 is a metal. In many cases, since the thermal conductivity is low, if the entire support member 20 is formed of a dielectric material, the heat radiation from the surface light emitting element or the surface light receiving element is lowered.

  For this reason, the support member 20 is made of a dielectric only in the portion of the flexible substrate 2 along the high-speed signal transmission line, and the portion in contact with the surface light-emitting element and the surface light-receiving element is made of metal, so that high-speed transmission with stable high-frequency characteristics is achieved. It is possible to achieve both the formation of the line and the heat dissipation from the element.

[Third Embodiment]
A third embodiment in which the present invention is preferably implemented will be described. FIG. 4 shows the configuration of the optical module according to this embodiment.
In the present embodiment, the flexible substrate 2 is bent into a curved shape, but a side portion formed by bending is provided with a flat portion, and the chip capacitor 7 is mounted on the portion.

  Since other configurations and operations are the same as those in the first embodiment, a redundant description is omitted.

  By increasing the bending curvature of the flexible substrate 2, the electronic component can be mounted on the curved surface portion that appears by bending the flexible substrate 2. Thereby, the optical module can be miniaturized.

In addition, the said embodiment is an example of suitable implementation of this invention, and this invention is not limited to this.
For example, in each of the above embodiments, the optical transmission module including the VCSEL and the driver IC is described as an example. However, the optical reception module can be created by replacing the VCSEL with the PD and the driver IC with the receiver IC. An optical transceiver module in which both a VCSEL and a PD, and both a driver IC and a receiver IC are mounted on a single optical module can be configured in the same manner as described above.
As described above, the present invention can be variously modified.

1 is a perspective view of an optical module according to a first embodiment in which the present invention is preferably implemented. It is a figure which shows the structure of the optical module concerning 1st Embodiment which implemented this invention suitably. It is a figure which shows the structure of the optical module concerning 2nd Embodiment which implemented this invention suitably. It is a figure which shows the structure of the optical module concerning 3rd Embodiment which implemented this invention suitably. It is a figure which shows the structure of the conventional optical module. It is a figure which shows the structure of the conventional optical module. It is a figure which shows the structure of the conventional optical module.

Explanation of symbols

1 Optical module 2 Flexible substrate 3 VCSEL
4 Bump 5 Driver IC
6 Underfill 7 Chip capacitor 8 Solder bump 9 Solder resist 10 Upper lid 11 Signal transmission line 12 Micro lens array 13 Optical connector 14 45 degree mirror 15 Emission light 16 Optical fiber 18 Solder material 19 Circuit board 20 Support member 21 Dielectric material 22 Heat dissipation Gel 51 Light incident / exit section 52 Guide pin 53 Guide hole

Claims (6)

At least one of a surface light emitting element and a surface light receiving element;
An optical module having a flexible substrate that electrically connects at least one of the surface light emitting element and the surface light receiving element and a circuit board,
The flexible substrate is
At least one of the surface light emitting element and the surface light receiving element is mounted and bent with a curvature larger than a predetermined value,
The diameter of the bent portion of the flexible substrate is a surface formed by a surface of a portion of the flexible substrate on which at least one of the surface light emitting element and the surface light receiving element is mounted and a portion that is electrically connected to the circuit board. Greater than the elevation difference,
The bent portion of the flexible substrate has a portion farthest from the circuit board, the surface light emitting element, and the surface light receiving than a difference in height between a portion that is closest to the circuit board and a surface that electrically connects the circuit board. An optical module characterized in that a difference in height from a surface of a portion on which at least one of the elements is mounted is larger. At least one of a surface light emitting element and a surface light receiving element;
A flexible board provided with a contact for making electrical connection between at least one of the surface light emitting element and the surface light receiving element and a circuit board;
An optical module having a plate-like support member having a curved surface on at least a part of a side surface,
The flexible substrate is
At least one of the surface light emitting element and the surface light receiving element is electrically connected, and is bent along the side surface of the support member and fixed to the support member,
The diameter of the bent portion is higher than the height difference between the surface formed by the flexible substrate, the surface on which at least one of the surface light emitting element and the surface light receiving element is mounted, and the portion that makes electrical connection with the circuit board. big,
The bent portion of the flexible substrate has a portion farthest from the circuit board than the height difference between the portion closest to the circuit board and the portion that makes electrical connection with the circuit board, the surface light emitting element, and the surface light receiving. An optical module characterized in that a difference in height from a surface of a portion on which at least one of the elements is mounted is larger. The support member is made of a metal material,
The optical module according to claim 2, wherein at least one of the surface light emitting element and the surface light receiving element is in contact with the support member.   The optical module according to claim 2, wherein the support member is made of a dielectric material.   3. The light according to claim 2, wherein the support member is formed of a dielectric material at a portion along the flexible substrate, and a metal material at a portion where at least one of the surface light-emitting element and the surface light-receiving element is in contact with the support member. module.   The electronic component is mounted on a side surface portion formed between a portion that is electrically connected to the circuit board and a portion that is farthest from the circuit board by bending the flexible substrate. The optical module according to any one of 1 to 5.

Images