JP2007273497A - Heat dissipation structure of optical module and optical communication module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the heat dissipation structure of an optical module that can effectively establish downsizing and low power consumption of an optical communication module, and to provide an optical communication module. <P>SOLUTION: A heat dissipation structure 1 is provided in an optical module 2 wherein a semiconductor laser element is mounted. The heat dissipation structure 1 includes a pair of heat transmission members 11 and 12 and a frame member 13. The heat transmission members 11 and 12 are respectively provided with heat receiving surfaces 11a and 12a along the side surface 21a of a stem 21 in the optical module 2, and they are facing each other with the stem 21 in between. The frame member 13 couples the heat transmission members 11 and 12. The coefficient of thermal expansion of the frame member 13 is smaller than those of the heat transmission members 11 and 12 and the stem 21. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat dissipation structure for an optical module and an optical communication module.

  In a wavelength division multiplexing (WDM) optical communication system, a plurality of communication channels communicate with optical signals having different wavelengths on the same optical transmission line. Therefore, it is desirable for the optical communication module that the wavelength of the optical signal does not fluctuate excessively due to a change in ambient temperature or the like. This is because if the wavelength of the optical signal fluctuates excessively, the optical signals of adjacent wavelengths will interfere with each other. However, the emission wavelength of the laser diode that generates the optical signal is shifted to the longer wavelength side due to the temperature change. For this reason, various configurations for suppressing the temperature change of the laser diode have been devised.

  For example, in the laser module disclosed in Patent Document 1, in a so-called butterfly type laser module, a laser diode is mounted on a Peltier element, and the temperature of the laser diode is controlled to be constant using the thermoelectric effect of the Peltier element. Yes. Further, in the laser diode module disclosed in Patent Document 2 and the semiconductor laser module described in Patent Document 3, a Peltier element is arranged outside the CAN package containing the laser diode. In each of the modules disclosed in Patent Documents 4 to 6, a Peltier element is arranged inside the CAN package, and a laser diode is mounted on the Peltier element.

Japanese Patent Laid-Open No. 2004-134776 JP-A-2005-050844 JP-A-7-131106 JP-A-2005-303242 Japanese Patent Laying-Open No. 2005-086094 US Patent Application Publication No. 2003/021310

  Each of the modules described in Patent Documents 1 to 6 uses a Peltier element to control the temperature of the laser diode. However, the optical communication module is required to have low power consumption and miniaturization for further high-density mounting of the optical communication device. If a Peltier element is provided, a relatively large installation space including its drive circuit is required, which is a factor that hinders downsizing. In addition, the power consumed in the Peltier element is much larger than the power consumed in the laser diode and its peripheral circuits, which is a factor that hinders the reduction in power consumption.

  The present invention has been made in view of the above problems, and an object thereof is to provide an optical module heat dissipation structure and an optical communication module that can effectively realize downsizing and low power consumption of the optical communication module. .

  In order to solve the above-described problems, an optical module heat dissipation structure according to the present invention is an optical module heat dissipation structure including a semiconductor optical element and a stem on which the semiconductor optical element is mounted, and a heat receiving surface along a side surface of the stem. A plurality of heat transfer members disposed around the stem and a frame member that connects the plurality of heat transfer members to each other, and the coefficient of thermal expansion of the frame member is the heat of each of the heat transfer member and the stem. It is characterized by being smaller than the expansion coefficient.

  In the heat dissipation structure of the optical module described above, the thermal expansion coefficient of the frame member is smaller than the thermal expansion coefficients of the heat transfer member and the stem. Therefore, even if the ambient temperature (environmental temperature) decreases and the heat transfer member and the stem contract, the frame member does not contract so much, and the position of each heat transfer member connected to the frame member becomes substantially constant. As a result, the heat receiving surface of the heat transfer member and the side surface of the stem contract in a direction away from each other, and the contact pressure between the heat receiving surface of the heat transfer member and the side surface of the stem decreases. The lower the contact pressure between the heat transfer member and the stem, the greater the thermal resistance between the heat transfer member and the stem. Therefore, according to the heat dissipation structure of the optical module described above, the lower the ambient temperature, the more difficult the heat from the semiconductor optical device is transmitted to the heat transfer member via the stem, so the temperature of the semiconductor optical device is higher than the ambient temperature. Kept.

  On the other hand, when the ambient temperature rises and the heat transfer member and the stem expand, the heat receiving surface of the heat transfer member and the side surface of the stem expand in a direction in which they are pressed against each other. Contact pressure with the side increases. And the higher the contact pressure between the heat transfer member and the stem, the smaller the thermal resistance between the heat transfer member and the stem. Therefore, according to the heat dissipation structure of the optical module described above, the higher the ambient temperature, the easier the heat from the semiconductor optical device is transferred to the heat transfer member through the stem, so the temperature of the semiconductor optical device approaches the ambient temperature. It becomes.

  As described above, according to the heat dissipation structure of the optical module described above, the temperature of the semiconductor optical device can be adjusted by a configuration that does not require power supply or a control circuit, such as a plurality of heat transfer members and frame members. Therefore, as compared with a conventional configuration using a Peltier element, it is possible to effectively realize downsizing and low power consumption of the optical communication module on which the optical module is mounted.

  The stem is disc-shaped, and the heat receiving surfaces of the plurality of heat transfer members are formed in a curved shape along the side surface of the stem, and the curvature radius of the heat receiving surface is the same as the curvature radius of the side surface of the stem or the stem It may be characterized by being smaller by a difference of 10% or less than the radius of curvature of the side surface. Thereby, since the adhesiveness of the heat-transfer member with respect to a disk shaped stem increases, the above-described relationship between the contact pressure and the thermal resistance can be realized more suitably.

  Further, the heat dissipation structure of the optical module may be characterized in that a pair of heat transfer members are disposed to face each other with a stem interposed therebetween, and a frame member connects the pair of heat transfer members to each other. Thereby, the heat dissipation structure mentioned above is realizable by simple structure. In the heat dissipation structure of the optical module, a pair of heat transfer members may be connected to one frame member, or a pair of frame members may connect both ends of the pair of heat transfer members.

  An optical communication module according to the present invention includes a semiconductor optical device, an optical module including a stem on which the semiconductor device is mounted, and a heat receiving surface along a side surface of the stem, and a plurality of components disposed around the stem. A heat transfer member, a frame member that couples the plurality of heat transfer members to each other, an optical module, a plurality of heat transfer members, and a housing that houses the frame member. And at least one heat transfer member that is smaller than the coefficient of thermal expansion of each of the stems and is in thermal contact with the housing. Thereby, the temperature of the semiconductor optical device can be suitably adjusted, and the optical communication module can be effectively reduced in size and power consumption. In addition, since the heat transfer member is in thermal contact with the housing, the heat escaped from the optical module to the plurality of heat transfer members can be suitably released to the outside of the optical communication module through the housing.

  In the optical communication module described above, the heat transfer member is in thermal contact with the housing means that the heat transfer member and the housing are in direct contact with each other, or a member having a thermal conductivity equal to or higher than that of the housing. In which the heat transfer member is interposed between the heat transfer member and the housing, or the heat transfer member and a member such as a heat dissipation sheet that can be in close contact with the housing are sandwiched between the heat transfer member and the housing. Including.

  Further, the optical communication module may further include a heat radiating sheet provided between the heat transfer member and the housing. Thereby, since the thermal resistance between the heat transfer member and the housing can be reduced, the heat from the optical module can be released more efficiently to the outside of the optical communication module.

  According to the heat dissipation structure of an optical module and the optical communication module according to the present invention, it is possible to effectively realize downsizing and low power consumption of the optical communication module.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of an optical module heat dissipation structure and an optical communication module according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

  FIG.1 and FIG.2 is a figure which shows the structure of the thermal radiation structure 1 of the optical module which concerns on this embodiment. FIG. 1 is a perspective view of the heat dissipation structure 1, and FIG. 2 is an exploded perspective view of the heat dissipation structure 1.

  The heat dissipation structure 1 is a structure for releasing heat generated in the optical module 2 containing the semiconductor optical element to the outside of a device (such as an optical communication module) on which the optical module 2 is mounted. Here, the optical module 2 includes, for example, a semiconductor laser element (laser diode) as a semiconductor optical element. The optical module 2 may incorporate a light receiving element such as a photodiode as a semiconductor optical element. The optical module 2 to be radiated in the present embodiment is an optical module having a CAN type package, and includes a disc-shaped stem 21 for mounting a semiconductor optical device, and a semiconductor optical device on the stem 21. And a cylindrical portion 23 made of metal. The stem 21 is provided with a plurality of lead pins 22 used for supplying a drive current to the laser diode (or taking out a signal current from the photodiode) and the like except for some lead pins 22. It has been.

  The heat dissipation structure 1 includes a plurality (a pair in this embodiment) of heat transfer members 11 and 12 and a frame member 13. In this embodiment, the frame member 13 has a rectangular pipe shape. The heat transfer members 11 and 12 are block-like members having approximately the same size as the stem 21, and are arranged side by side around the stem 21 of the optical module 2. In this embodiment, since the heat transfer members 11 and 12 are paired, the heat transfer members 11 and 12 are opposed to each other with the stem 21 in between.

  The heat transfer members 11 and 12 have heat receiving surfaces 11a and 12a along the side surface 21a of the stem 21, respectively. The heat receiving surfaces 11 a and 12 a are formed in a curved shape along the side surface 21 a of the stem 21. As shown in FIG. 1, the heat dissipation structure 1 and the optical module 2 are in a positional relationship in which the stem 21 is fitted in the space surrounded by the heat receiving surfaces 11a and 12a. Note that a heat radiating member such as a heat radiating sheet or silicon grease is not interposed between the heat receiving surfaces 11 a and 12 a and the side surface 21 a of the stem 21.

  More preferably, the curvature radii of the heat receiving surfaces 11a and 12b are the same as the curvature radius of the stem 21 or slightly smaller than the curvature radius of the side surface 21a of the stem 21 (specifically, one of the curvature radii of the side surface 21a). It is good if the difference is less than 10%. And when the heat dissipation structure 1 rises in temperature, the heat transfer members 11 and 12 may be configured to tighten the stem 21.

  Moreover, the heat-transfer members 11 and 12 have the heat radiating surfaces 11b and 12b on the opposite side to the heat receiving surfaces 11a and 12a, respectively. The heat radiating surfaces 11b and 12b are in direct contact with a housing or the like of a device (such as an optical communication module) on which the heat radiating structure 1 and the optical module 2 are mounted or through a heat radiating sheet, and the heat generated in the optical module 2 is It is a surface for transmitting to the housing. The heat radiating surfaces 11b and 12b are preferably flat in order to secure a contact area with the casing or the like that comes into contact, but may have undulations corresponding to the shape of the casing or the like that comes into contact.

  The frame member 13 is a member for connecting the heat transfer members 11 and 12 to each other. In the present embodiment, an annular frame member 13 connects the pair of heat transfer members 11 and 12 to each other. Specifically, a part of the annular frame member 13 passes through the heat transfer member 11, and another part of the frame member 13 passes through the heat transfer member 12. Further, the frame member 13 is exposed from a rod-shaped portion exposed from one end face (one end) 11c and 12c of the heat transfer members 11 and 12, and from the other end face (other end) 11d and 12d of the heat transfer members 11 and 12. And another bar-shaped part. These rod-shaped portions extend in the direction in which the heat transfer members 11 and 12 are juxtaposed.

  The material constituting the frame member 13 has a smaller coefficient of thermal expansion (linear expansion coefficient) than the materials constituting the heat transfer members 11 and 12 and the stem 21. Specifically, the frame member 13 is preferably configured to mainly include, for example, super invar (also referred to as super invar, invariable steel: the thermal expansion coefficient is about 0.8 ppm) having a very small thermal expansion coefficient. In addition, the heat transfer members 11 and 12 may be configured to mainly include, for example, a high thermal conductivity resin (polyphenylene sulfide (PPS) resin or the like: the coefficient of thermal expansion is about 12 to 26 ppm). The stem 21 is generally made of a metal material having a low thermal expansion coefficient such as a Kovar material (an alloy in which nickel and cobalt are mixed with iron: a thermal expansion coefficient is about 5 ppm).

  In addition, the thermal radiation structure 1 which has the said structure can be easily manufactured with what is called an insert mold technique. That is, the frame member 13 is housed in a casting mold, and the resin to be the heat transfer members 11 and 12 is poured into the mold and cured, so that the heat transfer members 11 and 12 and the frame member 13 are made. The integrated heat dissipation structure 1 can be easily manufactured.

  Subsequently, an optical communication module including the heat dissipation structure 1 and the optical module 2 described above will be described. 3-6 is a figure which shows the structure of the optical communication module 10 of this embodiment. Among these, FIG. 3 is a perspective view showing an appearance of the optical communication module 10. FIG. 4 is an exploded perspective view showing a detailed configuration of the optical communication module 10. FIG. 5 is an enlarged perspective view showing an enlarged configuration in the vicinity of the heat dissipation structure 1 in the optical communication module 10. FIG. 5 shows a state in which the cover 53 (described later) of the optical communication module 10 is removed for easy understanding. FIG. 6 is an enlarged cross-sectional view of the optical communication module 10 taken along line II in FIG.

  The optical communication module 10 of the present embodiment is a pluggable transceiver that is employed as a pluggable optical data link in optical communication, and includes an optical (transmission) module 2 equipped with a semiconductor laser element and an optical (reception) equipped with a light receiving element. Both of the modules 3 are provided, and an optical signal can be transmitted and received via an optical network. The optical communication module 10 can be removably inserted into a cage (slot) of a host device, and is detachably connected to a host connector disposed in the cage (slot).

  As shown in FIG. 4, the optical communication module 10 includes a heat dissipation structure 1, optical modules 2 and 3, a circuit board 4 electrically connected to the semiconductor laser element of the optical module 2 and the light receiving element of the optical module 3. , Optical modules 2 and 3, and a housing 5 that houses the circuit board 4.

  The housing 5 includes a frame member 51 that forms a basic skeleton of the optical communication module 10, a heat dissipating plate 52 that constitutes the upper surface wall of the optical communication module 10 and that radiates heat from the circuit board 4, and a bottom wall 53 a of the optical communication module 10. And a cover 53 having a pair of side walls 53b and 53c orthogonal to the bottom wall 53a. The frame material 51 is made of resin, for example, and the cover 53 is made of metal, for example.

  The frame member 51 is integrated with a receptacle 54 that detachably receives an optical connector optically coupled to the semiconductor laser element of the optical module 2 and an optical connector optically coupled to the light receiving element of the optical module 3 (both not shown). Is formed. A bail (handle) 57 and an actuator 58 for facilitating insertion / removal of the optical communication module 10 are attached to the outer surface of the receptacle 54. An opening 51 a is formed at the center of the frame member 51. The heat radiating plate 52 has a thick part 52 a protruding toward the circuit board 4, and the thick part 52 a is inserted into the opening 51 a of the frame member 51 and fixed to the frame member 51. The thick part 52 a of the heat radiating plate 52 is in contact with the circuit board 4, and the heat radiating plate 52 radiates heat from the electronic component 41 or the like mounted on the circuit board 4 to the outside of the optical communication module 10.

  Lead pins 22 and 32 projecting from the optical modules 2 and 3 are fixed to the front end of the circuit board 4 with solder or the like. The rear end portion of the circuit board 4 is a card edge portion (card edge connector) 4a that fits into the host connector. The optical modules 2 and 3 and the circuit board 4 are fixed to a frame member 51. The optical modules 2 and 3 are fixed by a tab plate 56 in a state where the optical modules 2 and 3 are arranged at predetermined positions of the receptacle 54.

  Inside the housing 5, the heat dissipation structure 1 is arranged around the optical module 2 in the form shown in FIG. 1. In this embodiment, the heat dissipation structure 1 is provided in the optical module 2 on which the semiconductor laser element is mounted. However, a similar heat dissipation structure may be provided in the optical module 3 on which the light receiving element is mounted, or the optical modules 2 and 3. Both of them may be provided with the same heat dissipation structure.

  Further, the heat transfer members 11 and 12 of the heat dissipation structure 1 are in thermal contact with the housing 5. That is, the heat transfer members 11 and 12 are in direct contact with the housing 5, for example. Alternatively, a member having a thermal conductivity equal to or higher than that of the housing 5 is interposed between the heat transfer members 11 and 12 and the housing 5. Alternatively, a member that can be in close contact with both the heat transfer members 11 and 12 and the housing 5 is sandwiched between the heat transfer members 11 and 12 and the housing 5. For example, as shown in FIG. 6, the optical communication module 10 of the present embodiment includes a heat radiation sheet 9 a between the heat radiation surface 11 b of the heat transfer member 11 and the bottom wall 53 a of the cover 53. The heat radiating sheet 9a has a structure in which an adhesive substance is applied to both surfaces of a sheet-like member having good thermal conductivity, and is provided in close contact with each of the heat radiating surface 11b and the bottom wall 53a. The heat radiating sheet 9a is made of a gel-like viscoelastic substance having a higher thermal conductivity than a general plastic material, and the viscoelastic substance is formed along minute irregularities present on the bottom wall 53a and the heat radiating surface 11b. Is closely attached to the bottom wall 53a and the heat radiating surface 11b, thereby expanding the area contributing to heat transfer and contributing to an increase in the amount of heat transfer. Further, the optical communication module 10 includes a heat radiating sheet 9 b between the heat radiating surface 12 b of the heat transfer member 12 and the heat radiating plate 52. The heat radiating sheet 9b has the same structure as the heat radiating sheet 9a, and is provided in close contact with each of the heat radiating surface 12b and the heat radiating plate 52.

  Next, the function and effect of the optical communication module 10 including the heat dissipation structure 1 will be described. In the heat dissipation structure 1 of the present embodiment, the thermal expansion coefficient of the frame member 13 is smaller than the thermal expansion coefficients of the heat transfer members 11 and 12 and the stem 21. Therefore, even if the ambient temperature of the optical communication module 10 decreases and the heat transfer members 11 and 12 and the stem contract, the frame member 13 does not contract so much, and the heat transfer members 11 and 12 connected to the frame member 13 do not contract. The position (specifically, the position of the coupling point between the heat transfer members 11, 12 and the frame member 13) is substantially constant. Accordingly, the heat transfer members 11 and 12 and the stem 21 contract in the direction in which the heat receiving surfaces 11a and 12a and the side surface 21a are separated from each other. Therefore, when the ambient temperature decreases, the contact pressure between the heat receiving surfaces 11a and 12a of the heat transfer members 11 and 12 and the side surface 21a of the stem 21 decreases.

  Conversely, when the ambient temperature of the optical communication module 10 rises and the heat transfer members 11 and 12 and the stem 21 expand, the heat transfer members 11 and 12 and the stem 21 are pressed against each other by the heat receiving surfaces 11a and 12a and the side surface 21a. Each expands in the direction of fit. Therefore, when the ambient temperature rises, the contact pressure between the heat receiving surfaces 11a and 12a of the heat transfer members 11 and 12 and the side surface 21a of the stem 21 increases.

  Here, FIG. 7 shows a typical example of the correlation between the ambient temperature (environment temperature, unit [° C.]) of the optical communication module 10 and the contact pressure (unit [MPa]) of the heat transfer members 11 and 12 and the stem 21. It is a graph. FIG. 7 shows the calculation results when the heat transfer members 11 and 12 are made of high thermal conductivity PPS resin, the frame member 13 is made of super invar, and the stem 21 is made of Kovar material.

  As shown in FIG. 7, in this calculation example, the heat transfer members 11 and 12 and the stem 21 are in contact with each other at around 25 ° C., and thereafter, the contact pressure between both increases linearly as the temperature rises. Recognize. Thus, if the heat transfer members 11 and 12 and the stem 21 are in contact with each other, the contact pressure increases and decreases in proportion to the ambient temperature. This calculation result is calculated on the assumption that the heat transfer members 11 and 12 and the stem 21 are separated from each other at an ambient temperature lower than 25 ° C., but the curvature radius of the heat receiving surfaces 11a and 12a is set to the value of the side surface 21a of the stem 21. By making it smaller than the radius of curvature and utilizing the elastic effect of the shape of the heat transfer members 11 and 12, the boundary between the contact state and the non-contact state can be made more gentle. Further, when the stem 21 has a disc shape as in the present embodiment, even if slight slip of the heat receiving surfaces 11a, 12a of the heat transfer members 11, 12 with respect to the side surface 21a is taken into consideration, these contact pressures are almost equal. Proportional to ambient temperature.

  FIG. 8 is a graph showing a typical example of the correlation between the contact pressure (unit [MPa]) between the heat transfer members 11 and 12 and the stem 21 and the thermal resistance (unit [° C./W]). In FIG. 8, the same materials as those in FIG. 7 are used for the heat transfer members 11 and 12, the frame member 13, and the stem 21.

  As shown in FIG. 8, as the contact pressure between the heat transfer members 11 and 12 and the stem 21 increases, the thermal resistance between the heat transfer members 11 and 12 and the stem 21 decreases. This phenomenon can be explained as follows. In other words, the heat receiving surfaces 11a and 12a of the heat transfer members 11 and 12 and the side surface 21a of the stem 21 have microscopic unevenness even when processed flat. Therefore, heat transfer between the heat transfer members 11 and 12 and the stem 21 is performed by direct contact between the fine irregularities and heat transfer via the air in the space generated by the irregularities. , The former becomes dominant. And as the contact pressure between the heat transfer members 11 and 12 and the stem 21 increases, the unevenness of each other deforms and the contact area increases.

In general, it is known that the thermal resistance decreases in proportion to the power of -0.95 of the contact pressure. When the thermal resistance due to contact is Rs, the thermal resistance due to air convection is Rg, and the combined thermal resistance is R, the following equation (1) is established.
(1 / R) = (1 / Rs) + (1 / Rg) (1)
The thermal resistances Rs and Rg are
Rs = B × P− ^0.95 / A (2)
Rg = C × P− ^0.097 / D (3)
It can be expressed as. However, in the formulas (2) and (3), B, C, and D are constants composed of the hardness and surface roughness of the contact object, the average distance between the contact surfaces, the thermal conductivity of the convection gas, and the like. Is the facing area and P is the contact pressure. From the above equations (2) and (3), it can be seen that the thermal resistance Rs due to contact is sufficiently larger than the thermal resistance Rg due to air convection. Therefore, from equation (1), the total thermal resistance R can be approximated by the thermal resistance Rs due to contact.

  As described above, the contact pressure between the heat transfer members 11 and 12 and the stem 21 varies depending on the ambient temperature, and the contact pressure and the heat resistance between the heat transfer members 11 and 12 and the stem 21 are constant. Has a correlation. That is, the lower the ambient temperature of the optical communication module 10, the lower the contact pressure between the heat transfer members 11, 12 and the stem 21, and the greater the thermal resistance between the heat transfer members 11, 12 and the stem 21, Heat from the semiconductor laser element is hardly transmitted to the heat transfer members 11 and 12 via the stem 21, and the temperature of the semiconductor laser element is kept higher than the ambient temperature. On the contrary, the higher the ambient temperature of the optical communication module 10, the higher the contact pressure between the heat transfer members 11, 12 and the stem 21, and the lower the thermal resistance between the heat transfer members 11, 12 and the stem 21. The heat from the semiconductor laser element is easily transferred to the heat transfer members 11 and 12 through the stem 21, and the temperature of the semiconductor laser element approaches the ambient temperature.

  FIG. 9 is a graph showing the relationship between the housing temperature of the optical communication module (that is, the temperature close to the ambient temperature) and the stem temperature (that is, the temperature near the semiconductor laser element) when the driving current of the semiconductor laser element is constant. It is. In FIG. 9, a graph G1 is a graph when the heat dissipation structure 1 of the present embodiment is provided, and a graph G2 is a graph when the temperature control means such as the heat dissipation structure 1 and the Peltier element of the present embodiment is not provided. In order to facilitate the explanation, the influence of an increase in the amount of heat generated due to a decrease in the light emission efficiency of the semiconductor laser element due to a temperature rise is omitted.

  When a heat dissipation structure or a Peltier element is not provided (Graph G2), a temperature difference of about 3 ° C. occurs between the case temperature and the stem temperature due to the heat generated by the semiconductor laser element. The value is almost close over the range (−40 ° C. to 85 ° C.). Therefore, the temperature change width ΔTb of the semiconductor laser element when the ambient temperature changes from −40 ° C. to 85 ° C. is about 125 ° C.

  On the other hand, when the heat dissipation structure 1 of the present embodiment is provided (graph G1), in a certain section A (between 0 ° C. and 45 ° C. in this example), the slope of the graph (with respect to the unit change width of the housing temperature). The rate of change in stem temperature is greatly relaxed. This is because the heat resistance between the heat transfer members 11 and 12 and the stem 21 changes according to the ambient temperature due to the above-described action of the heat dissipation structure 1. In addition, in the section B that is hotter than the section A (between 45 ° C. and 85 ° C. in this example), the slope of the graph G1 substantially matches the slope of the graph G2. This is because, in the section B, due to the thermal expansion of the heat transfer members 11, 12 and the stem 21, the contact pressure increases until both can be regarded as one in terms of heat conduction. Further, in the section C (−40 ° C. to 0 ° C. in this example) lower in temperature than the section A, the graph G1 follows the graph G2 while maintaining a substantially constant temperature difference (about 25 ° C.). This is because, in the section C, the heat transfer members 11 and 12 and the stem 21 are contracted to substantially leave a gap therebetween. In the example shown in FIG. 9, when the heat dissipation structure 1 of the present embodiment is provided, the temperature change width ΔTa of the temperature of the semiconductor laser element (the temperature of the stem 21) is 95 ° C., and the temperature when no temperature control means is provided. An improvement of 24% is recognized with respect to the change width ΔTb.

  The difference between the temperature of the semiconductor laser element (the temperature of the stem 21) and the ambient temperature (the temperature of the casing 5) is the amount of heat generated from the semiconductor laser element and the thermal resistance and heat generation between the semiconductor laser element and the casing 5. It depends on the quantity. In the present embodiment, the thermal resistance between the stem 21 and the heat transfer members 11 and 12 that are a part of the thermal resistance is passively changed using changes in the ambient temperature. As a result, the heat dissipation can be reduced to increase the temperature of the semiconductor laser element in a low temperature environment, and the heat dissipation can be increased to suppress the temperature increase of the semiconductor laser element in a high temperature environment. As a result, as described above, the temperature change width ΔTa of the semiconductor laser element is reduced, and the fluctuation range of the wavelength of the laser light output from the semiconductor laser element can be reduced.

  As described above, according to the heat dissipation structure 1 and the optical communication module 10 of the present embodiment, the optical module 2 has a configuration that does not require power supply or a control circuit, such as the plurality of heat transfer members 11 and 12 and the frame member 13. The amount of heat released from can be adjusted. Accordingly, the temperature of the semiconductor laser element can be suitably adjusted, and the optical communication module 10 on which the optical module 2 is mounted can be reduced in size, power consumption, and cost as compared with a conventional configuration using a Peltier element. Can be realized effectively.

  Among the WDM systems, in the DWDM (Dense Wavelength Division Multiplexing) system, the wavelength interval between adjacent channels is relatively short (for example, 0.8 nm), and the temperature of the semiconductor laser element must be substantially constant (for example, 30 ° C.). There is. On the other hand, in the CWDM (Coarse Wavelength Division Multiplexing) method, the wavelength interval between adjacent channels is longer than that in the DWDM method (for example, 20 nm), so that the temperature change width of the semiconductor laser element is kept at about 85 ° C. Communication can be suitably performed while suppressing interference between channels. Therefore, the heat dissipation structure 1 of the present embodiment showing the characteristics as shown in FIG. 9 is most suitable for the CWDM system. Further, when it is necessary to further suppress the temperature change width of the semiconductor laser element as in the DWDM method, the heat dissipation structure 1 of the present embodiment and the temperature control by the Peltier element may be used in combination. Generally, the Peltier element becomes difficult to control when the temperature difference between the two electrodes exceeds 50 ° C. In such a case, if the Peltier element and the heat dissipation structure 1 are used in combination, the temperature of the semiconductor laser element can be controlled over a wider ambient temperature range. Even when the required ambient temperature range is not wide, by using the Peltier element and the heat dissipation structure 1 in combination, the load on the Peltier element can be reduced, and the optical communication module 10 can be reduced in size and power consumption. Can contribute.

  Further, as in the present embodiment, the stem 21 has a disk shape, and the heat receiving surfaces 11a and 12a of the heat transfer members 11 and 12 are formed in a curved shape along the side surface 21a of the stem 21, and the heat receiving surface The curvature radii of 11a and 12a are preferably the same as the curvature radius of the side surface 21a of the stem 21 or smaller by a difference of 10% or less than the curvature radius of the side surface 21a of the stem 21. Thereby, since the adhesiveness of the heat-transfer members 11 and 12 with respect to the disk shaped stem 21 increases, the above-mentioned relationship between contact pressure and thermal resistance can be realized more suitably.

  Further, as in the present embodiment, the pair of heat transfer members 11 and 12 may be disposed to face each other with the stem 21 interposed therebetween, and the frame member 13 may connect the pair of heat transfer members 11 and 12 to each other. Thereby, one form of the heat dissipation structure according to the present invention can be realized with a simple configuration.

  Further, as in the present embodiment, the optical communication module 10 preferably includes heat radiation sheets 9 a and 9 b provided between the heat transfer members 11 and 12 and the housing 5. Thereby, since the thermal resistance between the heat transfer members 11 and 12 and the housing 5 can be reduced, the heat from the optical module 2 can be released to the outside of the optical communication module 10 more efficiently. In addition, a stable heat dissipation path can be obtained while absorbing dimensional variations such as the dimensional error of the housing 5 and the alignment error of the optical module 2.

  The optical module heat dissipation structure and the optical communication module according to the present invention are not limited to the above-described embodiments, and various modifications are possible. For example, in the above embodiment, the heat dissipation structure of the present invention is applied to the optical module 2 (laser module) on which the semiconductor laser element is mounted. In addition to this, the heat dissipation structure of the present invention can be applied to, for example, the optical module 3 on which a light receiving element is mounted. In this case, the temperature range inside the optical module can be made smaller than the ambient temperature range, and fluctuations in output characteristics due to temperature changes of the light receiving element can be suppressed. Alternatively, it is possible to operate in a wider ambient temperature range while maintaining output characteristics equivalent to those of the prior art.

  Moreover, although the said embodiment demonstrated the structure provided with a pair of heat-transfer member and one frame member as an example of the heat-radiation structure of this invention, the heat-radiation structure of this invention is provided with three or more heat-transfer members. Alternatively, a plurality of frame members may be provided. By arranging these heat transfer members around the stem and connecting them with a frame member, the effects of the above-described embodiment can be suitably obtained.

  In the above embodiment, each of the pair of heat transfer members is in thermal contact with the housing. However, in the heat dissipation structure of the present invention, at least one of the plurality of heat transfer members is a housing. By making thermal contact with the body, heat from the semiconductor optical device can be suitably released to the outside of the optical communication module.

FIG. 1 is a perspective view showing the configuration of the heat dissipation structure of the optical module according to the present embodiment. FIG. 2 is an exploded perspective view showing the configuration of the heat dissipation structure of the optical module according to the present embodiment. FIG. 3 is a perspective view showing the appearance of the optical communication module. FIG. 4 is an exploded perspective view showing a detailed configuration of the optical communication module. FIG. 5 is an enlarged perspective view showing an enlarged configuration near the heat dissipation structure in the optical communication module. FIG. 6 is an enlarged cross-sectional view of the optical communication module taken along line II in FIG. FIG. 7 is a graph showing a typical example of the correlation between the ambient temperature of the optical communication module and the contact pressure of the heat transfer member and the stem. FIG. 8 is a graph showing a typical example of the correlation between the contact pressure between the heat transfer member and the stem and the thermal resistance. FIG. 9 is a graph showing the relationship between the housing temperature of the optical communication module (that is, the temperature close to the ambient temperature) and the stem temperature (that is, the temperature near the semiconductor laser element) when the driving current of the semiconductor laser element is constant. It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Heat dissipation structure, 2 ... Optical (transmission) module, 3 ... Optical (reception) module, 4 ... Circuit board, 5 ... Housing, 6 ... Tab plate, 7 ... Bail, 8 ... Actuator, 9a, 9b ... Radiation sheet DESCRIPTION OF SYMBOLS 10 ... Optical communication module 11, 12 ... Heat-transfer member, 11a, 12a ... Heat-receiving surface, 11b, 12b ... Heat-radiation surface, 13 ... Frame member, 21 ... Stem, 22 ... Lead pin, 23 ... Cylindrical part, 41 ... Electron Components 51, frame material 52, heat sink 53, cover 54, receptacle

Claims (5)

An optical module heat dissipation structure comprising a semiconductor optical device and a stem on which the semiconductor optical device is mounted,
A plurality of heat transfer members having a heat receiving surface along a side surface of the stem and disposed around the stem;
A frame member connecting the plurality of heat transfer members to each other;
The heat dissipation structure of an optical module, wherein a thermal expansion coefficient of the frame member is smaller than a thermal expansion coefficient of each of the heat transfer member and the stem. The stem is disc-shaped;
The heat receiving surfaces of the plurality of heat transfer members are formed in a curved shape along the side surface of the stem, and the curvature radius of the heat receiving surface is the same as the curvature radius of the side surface of the stem or the side surface of the stem 2. The heat dissipation structure for an optical module according to claim 1, wherein the heat radiation structure is smaller by a difference of 10% or less than the radius of curvature. A pair of the heat transfer members are arranged opposite to each other with the stem interposed therebetween,
The heat dissipation structure for an optical module according to claim 1, wherein the frame member connects the pair of heat transfer members to each other. An optical module comprising a semiconductor optical element and a stem on which the semiconductor element is mounted;
A plurality of heat transfer members having a heat receiving surface along a side surface of the stem and disposed around the stem;
A frame member connecting the plurality of heat transfer members to each other;
A housing that houses the optical module, the plurality of heat transfer members, and the frame member;
The thermal expansion coefficient of the frame member is smaller than the thermal expansion coefficient of each of the heat transfer member and the stem,
The optical communication module, wherein at least one of the heat transfer members is in thermal contact with the housing. The optical communication module according to claim 4, further comprising a heat dissipation sheet provided between the heat transfer member and the housing.

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