JP2011077192A - Optical module, and temperature control structure thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the size of a temperature control structure of an optical module while suppressing formation of a solder ball. <P>SOLUTION: The temperature control structure of the optical module includes a temperature control element having an element upper surface whose temperature is controlled, a thermally conductive carrier having a carrier lower surface disposed on a predetermined region on the element upper surface and a carrier side face inclined to the outside upward from the carrier lower surface, and solder filled into a hollow formed of the element upper surface and carrier side face outside the predetermined region. The hollow functions as a solder pool to suppress formation of a solder ball. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a temperature control structure for an optical module.

  In recent years, with the increase in speed and capacity of optical communication systems, highly functional optical communication modules such as wavelength division multiplex communication (D-WDM) are required. Furthermore, miniaturization of the module for optical communication is also demanded as in the case of general electronic components. In order to meet such a demand, miniaturization of each component of the module for optical communication is required.

  The soldering of the temperature control element of the optical module will be described below. Patent documents 1 to 3 are examples of prior art in this technical field.

JP 2008-193003 A JP-A-11-295560 Special table 2008-504701 gazette

  In order to control the temperature of the optical module, the following structure is generally formed. A thermally conductive carrier is fixed on the temperature control element with solder. Optical components are mounted on the thermally conductive carrier. The temperature of the optical component is controlled by the temperature control element via the thermally conductive carrier.

  When the carrier and the temperature control element are fixed with solder, if the outer shape of the carrier has a size larger than that of the temperature control element, a problem such as the reference example shown in FIG. 2 may occur. FIG. 2 is a side view showing the temperature control element 103 and the larger carrier 102. The carrier 102 is fixed on the temperature control element 103 by the solder 104a. At this time, excessive solder may adhere to the back surface of the carrier 102 that protrudes from the temperature control element 103 to form solder balls 108.

  Such a solder ball 108 is particularly prominent when the carrier 102 and the temperature control element 103 are scrubbed (= rubbed together) in order to perform stronger solder adhesion. The formed solder balls 108 may fall off due to vibration or impact, causing an electrical short circuit in the package or physically damaging the optical components.

  FIG. 1 shows an optical module in a reference example for avoiding such a problem. As in this reference example, the outer dimension of the carrier 102 is generally designed to be sufficiently smaller than the temperature control element 103. In this case, the solder 104 adheres to the upper surface of the peripheral region of the temperature control element 103 and the side surface of the carrier 102. Therefore, the formation of the solder balls 108 can be avoided.

  However, since the size of parts of recent high-performance optical communication modules is increased, the carrier 102 having a large area may be required. On the other hand, the module size may not be increased due to product specifications. Therefore, it is necessary to store the large carrier 102 in a small module. Therefore, it is required to reduce the dimensional difference between the carrier 102 and the temperature control element 103 as much as possible.

  It is desired to reduce the dimensional difference between the carrier and the temperature control element while suppressing the generation of solder balls.

  The temperature control structure of the optical module includes a temperature control element having an element upper surface whose temperature is controlled, a carrier lower surface disposed on a predetermined region of the element upper surface, and a carrier side surface inclined outward from the carrier lower surface upward. And a solder filled in a recess formed by the element upper surface and the carrier side surface outside the predetermined region. Generation of solder balls is suppressed by the depression functioning as a solder pool.

  According to the present invention, by using a structure in which a solder pool is provided on the side surface of the carrier, the generation of solder balls can be suppressed, and the dimensional difference between the carrier and the temperature control element can be reduced.

FIG. 1 shows an optical module in a reference example. FIG. 2 shows an optical module in a reference example. FIG. 3 shows the optical module in the first embodiment. FIG. 4 shows an optical module in the second embodiment. FIG. 5 shows an optical module according to the third embodiment. FIG. 6 shows one process of the manufacturing method of the optical module.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 3 is a side view showing the temperature control structure of the optical module in the first embodiment of the present invention. The optical module 1 includes a temperature control element 3, a heat conductive carrier 2, and an optical device 5. On the upper surface of the temperature control element 3, a low melting point plating 6 for improving wettability is applied. Examples of the material of the plating 6 include gold, tin, and solder. The lower surface of the carrier 2 (the surface facing the upper surface of the temperature control element 3) is similarly subjected to plating 7 that improves wettability.

  A thermally conductive carrier 2 is disposed on the temperature control element 3. The carrier 2 is fixed on the temperature control element 3 by solder 4. An optical device 5 is arranged on the carrier 2. The optical device 5 has its optical characteristics controlled by the temperature being controlled by the temperature control element 3 via the carrier 2.

  The upper surface of the carrier 2 has a planar shape large enough to mount the optical device 5. The side surface of the carrier 2 is processed into a taper shape so that the side surface is inclined outward (opposite to the side where the temperature control element 3 is disposed), that is, the planar cross-sectional area becomes smaller toward the lower side. Is done. The sectional view is a trapezoid with the top surface as the bottom surface. As a result, the width and length of the back surface of the carrier 2 (the surface fixed by the temperature control element 3 and the solder 4) are designed to be smaller than the top surface of the temperature control element 3.

  In such a configuration, the lower surface of the carrier 2 is disposed on a predetermined region of the upper surface of the element whose temperature is controlled by the temperature control element 3. A recess is formed by the peripheral region outside the predetermined region on the upper surface of the element and the side surface of the carrier 2. When soldering to fix the carrier 2 and the temperature control element 3, the solder 4 is filled in this recess. As a result, the recess functions as a solder pool in which the solder 4 is accumulated. The lower surface of the carrier 2 is plated 7, and the side surface of the carrier 2 is not plated 7, and the material forming the carrier 2 is exposed on the side surface. The solder 4 does not adhere to these side surfaces. Therefore, the solder 4 adheres to the height of the lower end of the carrier 2 on the plating 6 of the temperature control element 3 as shown in FIG.

  Since the solder that has escaped when the carrier 2 and the temperature control element 3 are fixed is collected in the solder pool, the generation of solder balls 108 can be suppressed. Furthermore, the dimensional difference between the carrier 2 (particularly its upper surface) and the temperature control element 3 can be reduced. Therefore, even when a large laser light source and other optical components are mounted as the optical device 5 on the upper surface of the carrier, the size of the temperature control element 3 can be suppressed smaller than the size of the optical device 5.

[Second Embodiment]
FIG. 4 shows an optical module according to the second embodiment of the present invention. In the optical module 1a in this embodiment, in addition to the optical module 1 in the first embodiment, a plating 7a for improving the wettability of the solder 4a is applied to the side surface of the carrier 2. The carrier 2 and the temperature control element 3 are fixed by a low melting point solder 4a. Similar to the first embodiment, the carrier 2 has a structure in which the upper surface is wide and the lower surface is narrow. Its cross section is trapezoidal with the upper side at the bottom. The width of the lower surface of the carrier 2 (the vertical and horizontal dimensions) is narrower than the width of the upper surface of the temperature control element 3.

  With such a structure, the solder 4 a that escapes when the carrier 2 and the temperature control element 3 are fixed adheres to the side surface of the carrier 2. With this structure, generation of solder balls on the lower surface of the carrier 2 can be avoided and the area of the upper surface of the carrier 2 can be increased. Therefore, a large laser light source and other optical components can be mounted on the upper surface of the carrier 2 as the optical device 5.

  In the second embodiment, since the solder 4a adheres to the side surface of the carrier 2, the capacity of the solder pool is larger than that in the first embodiment. Therefore, it is possible to suppress the formation of solder balls even when the amount of excess solder is large. Further, since the area difference between the upper surface and the lower surface of the carrier 2 can be designed to be larger, an optical device 5 that is larger than the size of the temperature control element 3 can be mounted.

  On the other hand, the structure in which the plating 7 is not applied to the side surface of the carrier 2 as in the first embodiment has an advantage that the number of manufacturing steps is small. As shown in FIG. 6, when the carrier 2 is manufactured, the carrier base material 10 is formed by applying plating 12 and 13 to both surfaces of the material 11 of a single plate in advance. Thereafter, the carrier base material 10 is cut along the tapered cutting surface 14. As a result, the carrier 2 is formed in which the side surface is not plated 7 and the bottom surface is plated 7. Such manufacturing has fewer steps than the method of manufacturing the carrier in the second embodiment by plating the individual carriers 2. Therefore, when it is considered that the capacity of the solder pool is sufficient, the structure of the first embodiment is desirable.

[Third Embodiment]
FIG. 5 shows an optical module according to the third embodiment of the present invention. The carrier 2a of the optical module 1b in this embodiment has at least two stepped side surfaces instead of the tapered side surfaces. The upper stage 8 has side surfaces perpendicular to the upper and lower surfaces of the carrier 2a. The upper stage 9 also has side surfaces perpendicular to the upper and lower surfaces of the carrier 2a. The planar shape of the upper stage 8 is formed larger than the planar shape of the lower stage 9. Plating 7b is applied to the periphery of the carrier 2a, at least the lower surface thereof, and the side surface of the lower stage 9. Even with such a configuration, it is possible to form a solder pool by the step of the carrier 2a and the upper surface of the temperature control element 3, thereby suppressing the formation of solder balls.

  In the optical module having the temperature control structure according to the first to third embodiments, as the optical device 5, a ring resonator type laser light source configured by a planar optical waveguide (PLC) is preferably used. In general, a ring resonator type laser light source composed of PLC has a larger footprint than a semiconductor laser light source. By adopting the structure of the above embodiment, the area of the carrier upper surface can be made larger than the size of the temperature control element 3, and it becomes easy to mount an optical device having a large footprint.

  Furthermore, in the optical module having the temperature control structure of the first to third embodiments, as the optical device 5, an optical device having a laser light source having a wavelength variable function as a laser light source is also preferably used. In general, in an optical transmission module having a wavelength variable function, high-precision temperature control is required for a laser light source and a wavelength locker that are constituent parts thereof. In addition, the number of optical components is increased as compared with a single wavelength laser. Therefore, by adopting the structure of the above embodiment, it is possible to reduce the module size while mounting many optical components on a temperature-controlled carrier.

  Furthermore, in the optical module having the temperature control structure of the first to third embodiments, an optical receiver module in which an APD (avalanche photodiode) is mounted as the optical device 5 is also preferably used. In such an optical receiver module, an avalanche photodiode generates an electrical signal in response to incident light, thereby receiving an optical signal. Since the multiplication factor of APD changes depending on the temperature, temperature control is necessary. Further, in order to handle high frequencies, it is required to shorten the signal line and the package. Therefore, the structure of the above embodiment that can reduce the module size is effective.

DESCRIPTION OF SYMBOLS 1, 1a, 1b Optical module 2, 2a Carrier 3 Temperature control element 4, 4a, 4b Solder 5 Optical device 6 Plating 7, 7a, 7b Plating 8 Upper stage 9 Lower stage 10 Carrier base material 11 Material 12, 13 Plating 14 Cutting surface 102 Carrier 103 Temperature control element 104, 104a Solder 108 Solder ball

Claims (6)

A temperature control element having an upper surface of the element whose temperature is controlled;
A thermally conductive carrier having a carrier lower surface disposed on a predetermined region of the element upper surface, and a carrier side surface inclined outward from the carrier lower surface;
A temperature control structure of an optical module, comprising: a solder filled in a recess formed by the upper surface of the element and the side surface of the carrier outside the predetermined region. A temperature control structure for an optical module according to claim 1,
A temperature control structure of an optical module, wherein the lower surface of the carrier and the side surface of the carrier are plated to improve the wettability of the solder. A temperature control structure for an optical module according to claim 1,
A temperature control structure of an optical module, wherein the lower surface of the carrier is plated to improve the wettability of the solder, and the side surface of the carrier is not plated. The temperature control structure of the optical module according to any one of claims 1 to 3,
An optical module comprising: an optical planar waveguide disposed on an upper surface of the carrier. The temperature control structure of the optical module according to any one of claims 1 to 3,
An optical module comprising: a laser light source having a wavelength variable function disposed on an upper surface of the carrier. The temperature control structure of the optical module according to any one of claims 1 to 3,
An optical module comprising: an optical receiver disposed on an upper surface of the carrier and receiving an optical signal by an avalanche photodiode generating an electrical signal in response to incident light.

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