JPWO2009001822A1 - Optical module - Google Patents

Abstract

In the optical module, the direction in which light is emitted or incident is the same as the direction of heat radiation from the optical module. The optical transmission path optically coupled to the optical element and the heat sink are in direct contact or via a good thermal conductor. Heat generated from the optical module is effectively radiated through the optical transmission path 14 and the heat sink 19.

Description

  The present invention relates to an optical module, and more particularly to an optical module having a light emitting element or a light receiving element.

  In recent years, the speeding up of LSI has been further advanced. However, it is considered that there is a limit in transmission capability in the electrical wiring that connects these LSIs and the like. Optical interconnection is expected as a technology to overcome this limitation. Optical interconnection is a technique that uses an optical transmission line in place of conventional electrical wiring, and research and development have been progressing in recent years. Optical interconnection converts the electrical signal output from the LSI at the transmission source into an optical signal, transmits the target distance using an optical transmission line such as an optical waveguide or optical fiber, and converts the optical signal into an electrical signal on the receiving side. Then, a signal transmission form of inputting to the input pin of the LSI is adopted.

A high-performance LSI is equipped with a large number of input / output electrical terminals, more than 100,
In optical interconnection, it is necessary to replace all the terminals with optical signals. Also,
Since a high-speed signal of about 10 Gbps has a large loss in the electrical wiring, it is desirable to convert it to an optical signal in a situation where it is not lost as much as possible. In order to convert a large number of electric signals into optical signals while the loss in the electric wiring is small, it is a realistic solution to make the optical / electrical conversion part as small as possible and install it near the LSI. That is, it is very important to reduce the size of the optical module that is an optical / electrical conversion component.

  FIG. 8 shows an optical module described in Non-Patent Document 1, which is an example of optical interconnection. In the figure, an optical module 30 includes an optical element 32 having a light emitting function, a driver IC 33 for driving the optical element 32, a heat sink 34 made of a metal plate, and a mirror surface 35 for guiding light emitted from the optical element 32. And a lens block 36. The optical element 32 is accommodated in the ceramic package 31, and the heat sink 34 is disposed on the back surface of the ceramic package 31.

  In the optical module 30, when viewed from the optical element 32 and the driver IC 33, the extraction of the signal light is directed downward, the propagation of the electrical signal is directed in the left-right direction, and the heat dissipation (cooling) is directed in different directions. That is, in the optical module 30 having this structure, the direction in which the light from the optical element 32 is emitted, the direction in which the electrical signal propagates to the optical element, and the direction in which the optical module 30 radiates (cools) are directed in different directions. ing. With this configuration, interference can be avoided with respect to the arrangement of components for extracting each signal from the optical element and heat dissipation components.

Patent Document 1 describes an optical module having an improved heat dissipation structure. This optical module is shown in FIG. The optical module 40 has an electronic component 42 and a light emitting element 43 mounted on a printed board 41, and has an upper heat radiating plate 44 and a lower heat radiating plate 45 sandwiching the printed board 41. A hole 46 is formed in the upper radiator plate 44, and the light emitted from the light emitting element 43 is
It passes through the hole 46 and heads upward.
The above documents are as follows.
C-3-71 “Low Profile 10Gbit / sX4channel Parallel Optical Transmitter / Receiver” at the 2006 Electronics Society Conference of the Society of Electronics, Information and Communication Engineers Japanese Patent Laid-Open No. 2004-200533

  In the structure of Non-Patent Document 1, a component that extracts signal light, a component that extracts electrical signals, and a heat dissipation component are arranged in different directions as viewed from the optical element in order to avoid mutual arrangement interference. There was a limit to conversion. In particular, components for optical coupling such as optical lenses and mirrors are arranged in the direction in which signal light is extracted, and heat radiation components such as metal plates are arranged in the direction in which the optical module radiates (cools). Since these components are arranged in the opposite direction when viewed from the light emitting element or the light receiving element of the optical module, miniaturization of the optical module has been hindered.

In the heat dissipation structure of the optical module described in Patent Document 1, a hole is formed in the upper heat sink, the light of the light emitting element is emitted through the hole, and the emission direction and the heat dissipation direction of the signal light are viewed from the light emitting element. Since they can be arranged on the same side, the arrangement efficiency is improved and the optical module can be miniaturized.
However, since the light-emitting element and the upper heat sink are arranged with a space therebetween, and heat generated by the light-emitting element is dissipated mainly by radiation or convection, improvement of the heat dissipation effect is limited.

  In view of the above, the object of the present invention is to arrange the light emission or incidence direction and the heat radiation direction in the same direction as viewed from the optical element, so that the arrangement efficiency of the components is high and the heat generated by the optical element is generated. An object of the present invention is to provide an improved optical module that can be efficiently transmitted to a heat sink.

The present invention relates to an optical module comprising: an optical element having a light emitting function or a light receiving function; an optical transmission path optically coupled to the optical element by an optical connector; and a heat sink that dissipates heat generated by the optical element.
Provided is an optical module, wherein at least a part of the optical connector is formed of a good heat conductor material and is in direct contact with the heat sink or through a good heat conductor material.

  According to the optical module of the present invention, heat generated from the optical module is efficiently transmitted to the heat sink by heat conduction, and can be efficiently radiated from the heat sink.

  The above and other objects, features, and advantages of the present invention will become apparent from the following description with reference to the drawings.

Sectional drawing of the transmission side optical module of 1st Embodiment. Sectional drawing of the receiving side optical module of 1st Embodiment. Sectional drawing of the optical module of 2nd Embodiment. Sectional drawing which shows an example of the optical module of 3rd Embodiment. Sectional drawing of the optical module of 4th Embodiment. Sectional drawing of the optical module of 5th Embodiment. Sectional drawing of the optical module of 6th Embodiment. Sectional drawing of the conventional optical module. The perspective view of another conventional optical module.

  Hereinafter, embodiments of the present invention will be described. In addition, in order to make an understanding of invention easy, the same referential mark was attached | subjected and shown about the same component in each embodiment.

First Embodiment The first embodiment is an example in which the present invention is applied to a small optical module of a type connected to an optical fiber. 1 and 2 are cross-sectional views of the optical module of the present embodiment, respectively. First, the structure will be described. In the optical module shown in FIG. 1, a vertical cavity surface emitting laser (VCSEL) 12 constituting an optical element and an optical element driving IC (VCSEL) are formed on an electric wiring board (hereinafter simply referred to as a wiring board) 11. Driver) 13 is mounted. The VCSEL 12 and the optical element driving IC 13 are connected to an electric wiring (not shown) in the wiring board. A surface emitting laser is generally used in combination with a VCSEL driver and constitutes a transmission side optical module. In the optical module of FIG. 2, a surface light receiving element 21 that constitutes an optical element and an amplifier (amplifier IC) 22 that amplifies an electric signal are mounted on the wiring board 11. The surface light emitting element 21 and the amplifier IC 22 are connected by an electric wiring (not shown). The surface light receiving element is generally used in combination with an amplifier IC and constitutes a receiving side optical module.

In the optical modules 10 and 10A shown in FIGS. 1 and 2, the electrical connection between the optical elements 12 and 21, the optical element driving IC 13 or the amplifier 22 and the wiring board 11 is made with a connecting material such as solder or gold.
The optical elements 12 and 21 may be a single channel or a multi-channel having about 12 channels. Above the optical elements 12 and 21, a short optical fiber (intra-module optical fiber) 14 formed in the optical module is provided. The centers of the light receiving and emitting portions of the optical elements 12 and 21 and the core center of the short optical fiber 14 are aligned. The short optical fiber 14 includes an optical fiber fixing component 15 that is a material having good thermal conductivity such as silicon, and the like. The lid 16 is supported from both sides.

  The short optical fiber 14 is formed only in the optical module, and is fixed using a V-groove or the like processed in silicon of the optical fiber fixing component 15. The short optical fiber 14 is connected to an external optical fiber 18 using an optical connector 17. A heat sink 19 is disposed above the optical element driving IC 13 and the amplifier 22, and the heat sink 19 and the optical fiber fixing component 15 are fixed by an adhesive or the like. The lower surface of the heat sink 19 is disposed in contact with the upper surfaces of the optical element driving IC 13 and the amplifier 22, and a part of the outer edge portion of the lower surface of the heat sink 19 is fixed to the wiring substrate 11. The optical element driving IC 13 and the amplifier 22 and the heat sink 19 may be in direct contact with each other, or a material such as a compound having high thermal conductivity, grease, or a heat radiation sheet may be inserted therebetween.

  Next, functions will be described. In the transmission side optical module 10 of FIG. 1, an electrical signal from an LSI outside the module (not shown) is input to the VCSEL driver 13 via the wiring board 11. The VCSEL driver 13 supplies a drive current to the VCSEL 12. An optical signal is output from the VCSEL 12 with a light intensity corresponding to the amount of drive current. For example, the optical signal corresponds to the digital signal “0” when the light intensity is weaker than a predetermined value, and corresponds to the digital signal “1” when the light intensity is higher than the predetermined value. The optical signal output from the VCSEL 12 is coupled to the short optical fiber 14, and then optically coupled to the optical fiber 18 having a target length before being transmitted. The heat generated by the VCSEL driver 13 is radiated mainly through the heat sink 19. The heat generated by the VCSEL 12 is radiated from the heat sink 19 mainly through the optical fiber fixing component 15 having good thermal conductivity. At this time, the optical fiber fixing component 15 functions as a so-called heat spreader and diffuses heat generated from the VCSEL 12 in a direction perpendicular to the VCSEL 12. For this reason, a heat dissipation structure with high cooling efficiency is obtained. The optical module 10 is cooled to the target temperature by air cooling when the total calorific value of the VCSEL driver 13 and the VCSEL 12 is small, and by water cooling when the total calorific value is large.

  In the receiving-side optical module 10A of FIG. 2, an optical signal transmitted via the optical fiber 18 having a target length is coupled to the short optical fiber 14 and coupled to the surface light receiving element 21 at the end. In the surface light receiving element 21, the optical signal is converted into an electric signal and is electrically amplified by the amplifier 22. The amplified electrical signal is output to an LSI (not shown) outside the optical module via the wiring board 11. The light receiving element 21 and the amplifier 22 are cooled in the same manner as the transmission side optical module 10 described above.

  A ceramic substrate or a printed circuit board is suitable for the wiring substrate 11. For the heat sink 19, a metal having good thermal conductivity, particularly copper, aluminum, etc., which are easy to shape, are suitable. For the optical fiber fixing part 15, silicon that is easy to process a V-groove and has good thermal conductivity is particularly suitable.

  Next, a manufacturing method will be described. Since the manufacturing method of the transmission-side optical module 10 and the reception-side optical module 10A are the same, the manufacturing method is described only for the transmission-side optical module 10, and the description of the reception-side optical module 10A is omitted. There are the following two manufacturing methods.

  First, the first manufacturing method will be described. A VCSEL 12 and a VCSEL driver 13 are mounted on the wiring board 11. Separately, the short optical fiber 14 is aligned with the optical fiber fixing part 15, and the lid 16 is put on and fixed. The short optical fiber 14 is aligned in a V-groove formed in the optical fiber fixing component 15 and fixed with an adhesive or the like. There may be a plurality of short optical fibers 14 depending on the purpose. A combination of the short optical fiber 14, the optical fiber fixing component 15, and the lid 16 is referred to as an optical fiber unit. This optical fiber unit is bonded to the heat sink 19 and the two are collectively referred to as an “optical fiber / heat sink unit”. The optical fiber / heat sink unit is mounted on the wiring substrate 11 on which the VCSEL 12 and the VCSEL driver 13 are mounted. At that time, the light emitting part of the VCSEL 12 and the core of the short optical fiber 14 are aligned. Here, “alignment” means that the optical axis of the VCSEL 12 and the optical axis of the short optical fiber 14 coincide with each other within 10 μm, for example, and the distance between both parts is as short as 10 to 50 μm.

  Hereinafter, the second manufacturing method will be described. First, an optical fiber unit is assembled, and the VCSEL 12 is connected to the tip of the optical fiber. At that time, the alignment of the VCSEL 12 and the short optical fiber 14 is the same as described above. Next, the heat sink 19 is bonded to the optical fiber unit. A composite part in which the VCSEL 12, the optical fiber unit, and the heat sink 19 are integrated is referred to as an “optical fiber / VCSEL / heat sink unit”. Separately, the VCSEL driver 13 is mounted on the wiring board 11. The optical fiber / VCSEL / heat sink unit is mounted on the wiring board 11 on which the VCSEL driver 13 is mounted. At that time, the electrodes of the VCSEL 12 and the electrodes of the wiring board 11 are connected using solder, gold bumps, or the like. In this manufacturing method, the optical coupling efficiency can be inspected when the short optical fiber 14 and the VCSEL 12 are bonded. For this reason, there is an advantage that only non-defective products can be selected and mounted on the wiring board. In this manufacturing process, when the signal speed is as high as 10 Gbps, for example, the loss budget between transmission and reception of optical signals decreases, so it is important to be able to reduce the coupling loss between the VCSEL and the optical fiber.

Second Embodiment The second embodiment is an example in which the present invention is applied to an optical waveguide type small optical module.
The optical module 10B of the second embodiment is obtained by changing the short optical fiber 14 to a short optical waveguide (intra-module optical waveguide) 23 in the optical module 10 of FIG. 1, and its structure is shown in FIG. In the optical module 10B of the present embodiment, it is desirable to use glass or polymer for the optical waveguide material when the optical signal is in single mode, and to use polymer for the optical waveguide material in the case of multimode. It is desirable.

  Regarding the function of the optical module 10B, the short optical waveguide takes over the function of the short optical fiber 14 in the previous embodiment. That is, the VCSEL 12 and the short optical waveguide 23 constituting the optical element are optically coupled.

  In the manufacturing method of the optical module of this embodiment, there are two methods for forming the short optical waveguide 23. In the first method, an optical waveguide is first formed on a silicon substrate, and the short optical waveguide 23 is manufactured by dicing the optical waveguide. In the second method, a polymer optical waveguide film is first manufactured, and then the polymer optical waveguide film is bonded to silicon that is the optical fiber fixing component 15. The structure of the present embodiment is particularly suitable for producing a multi-channel short optical waveguide, and has an advantage that the pitch between a plurality of short optical waveguides can be accurately controlled by using a photolithography technique.

Third Embodiment The present embodiment is an example in which the present invention is applied to an optical module in which an optical lens is disposed between an optical element and a short optical fiber. FIG. 4 shows the optical module of this embodiment. In the optical module 10 </ b> C, an optical lens 24 is disposed on the VCSEL 12. In this structure, an optical lens 24 as a component made of glass or transparent resin is provided between the VCSEL 12 and the short optical fiber 14. As another example, the VCSEL 12 itself may have an optical lens. The structure in which the VCSEL 12 itself has an optical lens is produced by, for example, processing the GaAs substrate of the VCSEL 12 into an optical lens shape by etching.

  In the present embodiment, the spread of light emitted from the VCSEL 12 can be suppressed, and thereby the optical coupling efficiency with the short optical fiber can be increased. The heat dissipating structure is such that a minute gap is formed between the VCSEL 12 and the optical fiber unit, and the positional relationship between the upper and lower parts does not change, so that the heat dissipating effect is not greatly reduced.

Fourth Embodiment The present embodiment is an example in which the present invention is applied to an optical module in which a vertical optical waveguide extending in a direction perpendicular to the substrate is formed on an optical element. FIG. 5 shows an optical module 10D of this embodiment. First, the structure will be described. A VCSEL and a light receiving element having a wavelength of 850 nm are manufactured using a GaAs substrate.

  The GaAs substrate is not transparent to the wavelength 850 nm band. For this reason, the configuration of the VCSEL 12 having the optical lens adopted in the third embodiment is not suitable for the wavelength band because the optical signal passes through the substrate of the optical element and the optical signal intensity is attenuated. For this reason, in a conventional optical element that operates in that wavelength band, there is an example in which a structure in which the remaining optical element portion is formed of glass while leaving a thickness of several μm necessary for light emission or light reception is employed. In this embodiment, such a structure is adopted, and the glass portion includes an optical waveguide in the same direction as the short optical fiber.

  As a function of this embodiment, in the VCSEL of the transmission side optical module, the emitted light propagates through the vertical optical waveguide 25 in the glass and is coupled to the short optical fiber at the tip. If the in-glass vertical optical waveguide is not provided, the light may spread greatly upon exiting the VCSEL 12. By adopting the longitudinal optical waveguide in the glass, the light size does not expand beyond the width of the optical waveguide, so that highly efficient optical coupling between the VCSEL 12 and the short optical fiber 14 is possible.

  The manufacturing method of this embodiment can be produced by drawing an optical waveguide in glass using, for example, a femtosecond laser.

Fifth Embodiment This embodiment is an example in which the present invention is applied to an optical module in which a wiring board has cavities. FIG. 6 shows an optical module 10E of this embodiment. The wiring board 11 includes a cavity 26, and the VCSEL 12 and the VCSEL driver 13 constituting the optical element are mounted in the cavity 26. The heat sink 19 has a rectangular parallelepiped shape having a lower surface in contact with the upper surface of the wiring board 11. A ceramic substrate or the like is suitable for the wiring substrate 11, and a material such as Kovar is suitable for the heat sink 19.

  By adopting the above structure, an optical module can be manufactured using the heat sink 19 using Kovar, which is a material close to the thermal expansion coefficient of the ceramic constituting the wiring board 11. The coefficients of thermal expansion are 5.0 for ceramic, 4.7 for kovar, and 24.0 for aluminum. The thermal expansion coefficients of ceramic and Kovar are almost the same. As a result, the expansion and contraction of the wiring board and the heat sink due to the thermal expansion are substantially equal, and the thermal stress generated therebetween is reduced. For this reason, the damage in both components and its junction can be prevented.

Sixth Embodiment This embodiment is an example in which the present invention is applied to an optical module having a transparent resin between an optical element and an optical fiber. FIG. 7 shows an optical module 10F of this embodiment. When air is interposed between the short optical fiber 14 and the VCSEL 12 constituting the optical element, interfaces having different reflectivities are formed between the VCSEL 12 and the air, and between the air and the short optical fiber 14, Light loss occurs. For example, a loss of 1.5 dB occurs at the interface between the GaAs substrate of the VCSEL 12 (with a refractive index of about 3.4) and air with a refractive index of 1. Further, a loss of 0.2 dB occurs at the interface between the air and the short optical fiber 14. The total is 1.7 dB.

  By interposing the transparent resin 27, the loss at the interface between the VCSEL 12 and the transparent resin 27 having a refractive index of 1.5 is reduced to 0.8 dB. Further, since the loss at the interface between the transparent resin 27 and the short optical fiber 14 is almost zero, the loss is 0.8 dB in total. That is, in this embodiment, 0.9 dB loss reduction is possible.

  The optical element according to the present invention includes a laser that generates light toward the outside of the module, and a light receiving element that receives light from the outside into the module, such as an optical modulator. The optical transmission line includes an optical fiber and an optical waveguide, and may partially include an optical element such as an optical branching device and an optical device. The good thermal conductor includes ceramic, silicon and the like in addition to metal.

  Although the invention has been particularly shown and described with reference to illustrative embodiments, the invention is not limited to these embodiments and variations thereof. It will be apparent to those skilled in the art that various modifications can be made to the present invention without departing from the spirit and scope of the invention as defined in the appended claims.

This application is based on and claims the priority of Japanese Patent Application No. 2007-167288 filed on Jun. 26, 2007, the entire disclosure of which is incorporated herein by reference. join.

Claims (8)

An optical module comprising: an optical element having a light emitting function or a light receiving function; an optical transmission path optically coupled to the optical element by an optical connector; and a heat sink that dissipates heat generated by the optical element,
An optical module, wherein at least a part of the optical connector is formed of a good heat conductor material and is in direct contact with the heat sink or through a good heat conductor material.   The optical transmission path includes an optical fiber in the module, and a fixing member for fixing the optical fiber in the module and the optical connector is formed of a heat conductive material and is disposed in direct or indirect contact with the heat sink. The optical module according to claim 1.   The optical module according to claim 2, wherein the fixing member is made of silicon.   The optical module according to claim 1, wherein an optical lens is disposed between the optical element and the optical connector.   The optical module according to claim 1, wherein the optical element includes an optical lens at an interface with the optical connector.   The optical module according to claim 1, wherein the optical element includes an optical waveguide formed in glass, and is optically coupled to the optical transmission line via the optical waveguide.   The light according to claim 1, wherein the optical element is disposed inside a cavity formed on a surface of the wiring board, and the heat sink is fixed on the wiring board outside the cavity. module. The optical module according to claim 1, wherein a transparent resin is interposed between the optical element and the optical transmission line.

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