JP2009049333A - Heat dissipater, and optical transceiver with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transceiver equipped with a heat dissipater which dissipates heat generated by an electronic component to the outside through a case, is not brought into contact with the electronic component, and can keep force applied to a package of the electronic component within a predetermined range. <P>SOLUTION: The optical transceiver 10 includes: the heat dissipater which dissipates the heat generated by the electronic component (IC) 20a mounted on a circuit board 20 to the outside through the case containing the circuit board 20, wherein the heat dissipater has: a heat conduction sheet 21 disposed on a heat dissipation surface of the IC 20a; a metal plate 22 disposed over the heat conduction sheet 21; and heat conduction paste interposed between the metal plate 22 and an internal wall surface of the case. The heat dissipater conducts the heat generated by the IC 20a to the case through the heat conduction sheet 21, metal plate 22, and heat conduction paste. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heat radiating device that radiates heat generated by an electronic component mounted on a circuit board to the outside through a housing that houses the circuit board, and an optical transceiver including the heat radiating device.

  An optical transceiver is used for optical communication for transmitting and receiving optical signals. As an optical subassembly (OSA: Optical Sub-Assembly), an optical subassembly (TOSA: Transmitter Optical Sub-Assembly) for transmitting optical signals is used. A receiving optical sub-assembly (ROSA) that receives an optical signal is mounted. Furthermore, the optical transceiver includes an integrated circuit (IC) as an electronic component that exchanges electrical signals with the TOSA or ROSA. In addition, industry standards have been established for optical transceivers. For example, small optical transceivers conforming to industry standards XENPAK and X2 adopt a structure that can be inserted into and removed from the host system cage (pluggable structure). is doing.

  Heat is generated from the IC mounted on the optical transceiver, and when this amount of heat generation increases, it causes the reliability and malfunction of the IC. For this reason, an optical transceiver using a pluggable structure (pluggable optical transceiver) includes a heat dissipation device that radiates heat generated from an IC mounted on a circuit board to the outside through the housing of the optical transceiver.

  For example, an optical transceiver disclosed in Patent Document 1 is a heat conductive sheet between an IC 20a mounted on a circuit board 20 and a housing 50 of the optical transceiver, as shown in an enlarged view of a main part of the optical transceiver in FIG. (Sheet on rubber with soft thermal conductivity) 21 is provided with a heat dissipating device assembled with 21 sandwiched therebetween. The optical transceiver of Patent Document 1 is configured to transmit heat generated from the IC 20a to the housing 50 via the heat conductive sheet 21 and radiate the heat to the outside by this heat dissipation device.

  However, in a general optical transceiver, the interval between the upper surface of the IC package and the housing (heat sink) varies depending on variations in IC mounting height, component dimensions, and the like. Therefore, in the optical transceiver of FIG. 4, if the thickness of the heat conductive sheet 21 sandwiched between the package upper surface of the IC 20a and the housing (heat sink) 50 is constant, the amount of compression of the heat conductive sheet 21 varies.

  For example, in the optical transceiver of FIG. 4, the distance between the IC 20 a and the housing 50 is designed to be 0.3 mm, and an elastic 0.5 mm-thick heat conductive sheet 21 is sandwiched therebetween. In the configuration as described above, the interval between the IC 20a and the casing 30 varies by about ± 0.1 mm due to dimensional variations of the casing 50, the circuit board 20, and the IC 20a. The value varies between 4 mm. Therefore, the amount of compression in the thickness direction of the 0.5 mm thick heat conductive sheet 21 also varies from 0.1 to 0.3 mm.

  As described above, the amount of compression of the heat conductive sheet varies. As a result of increasing the force applied to the package upper surface of the IC 20a by compressing the heat conductive sheet 21, a BGA (Ball Grid Array) that is weak against an external force. An IC having a large package size such as the above is not preferable because the package may be damaged and its function may be impaired.

  In order to suppress variation in the compression amount of the heat conductive sheet, it is only necessary to measure the IC mounting height and component dimensional variation and select a heat conductive sheet having a thickness corresponding to the measured value. As a result, variations in the compression amount of the heat conductive sheet can be suppressed, and as a result, the pressing force applied to the upper surface of the package of the IC 20a by the heat conductive sheet 40 falls within a predetermined range, that is, the pressing force can be suppressed. it can. However, this method is time consuming and impractical.

As a method of suppressing the pressing force, in addition to the above, there is a method of filling and using a heat radiation paste (thermal conductive paste) between the IC and the housing. FIG. 5 is an enlarged view of a main part of an optical transceiver employing this method. When heat generated in the IC 20a is radiated from the housing 50 through the heat conductive paste 60 as in the optical transceiver of FIG. 5, the heat conductive paste 60 is usually applied on the IC 20a mounted on the circuit board 20. After the circuit board 20 is spread to a certain extent, the circuit board 20 is assembled into the housing 50, and the heat conductive paste 60 is spread and adhered to the gap between the IC 20a and the housing 50. This promotes heat conduction and ensures heat dissipation.
JP 2005-316484 A

  In the optical transceiver, the risk of applying excessive pressure to the IC as in the case of using a heat conductive sheet can be reduced by using the heat conductive paste as described above. However, when the housing is opened for maintenance purposes such as component replacement, the thermal paste is attached to the IC, which not only takes time for maintenance work, but also between the IC and other components and the board. It is difficult to completely remove the heat conductive paste that has entered the fine gaps in the gap, which hinders maintenance work. When removing the heat conductive paste by cleaning, it is necessary to remove TOSA, ROSA, etc., which cannot be cleaned, from the components of the optical transceiver, and there is a problem in workability.

  The present invention has been made in view of the above-described circumstances, and dissipates heat generated in the electronic component to the outside through the housing, and does not come into contact with the electronic component. It is an object of the present invention to provide a heat radiating device capable of keeping a force applied to a component package within a predetermined range and an optical transceiver including the heat radiating device.

  In order to solve the above problems, the heat dissipation mechanism of the present invention dissipates heat generated by electronic components mounted on a circuit board to the outside through a housing that houses the circuit board. A heat conductive sheet was placed on the heat radiating surface of the component, a metal plate was placed on top of the heat conductive sheet, and a heat conductive paste was interposed between the metal plate and the inner wall surface of the housing, generating electronic components. Heat is transmitted to the housing through a heat conductive sheet, a metal plate, and a heat conductive paste.

Further, the metal plate may be provided with a groove in the peripheral portion of the surface facing the housing.
In addition, this invention can also be used as the optical transceiver provided with the said heat radiating device.

  According to the present invention, the heat applied to the IC is not greatly compressed regardless of the mounting height of the IC on the circuit board and the dimensional variation of the components, so that the force applied to the IC can be suppressed. . In addition, since the heat conductive paste is not directly attached to the IC, maintenance workability can be improved.

An example of an optical transceiver to which a heat dissipation device according to the present invention is applied will be described with reference to FIGS. FIG. 1 is an external view of an optical transceiver, and FIG. 2 is an exploded view of the optical transceiver.
The optical transceiver 10 is used by being mounted in an opening of a face panel of a host device (not shown) for optical communication. For example, as shown in FIG. A housing 12 and a cover 13 are provided.

  The upper housing 11 and the lower housing 12 form an optical receptacle R into which an optical connector (not shown) for optical communication is inserted. The cover 13 is attached to the lower part of the optical transceiver 10 to cover a circuit board and the like which will be described later. A circuit board is sandwiched between the upper casing 11 and the lower casing 12, the lower casing 12 is attached to the upper casing 11, and the cover 13 is assembled from the lower side of the upper casing 11, In the transceiver 10, XENPAK and X2 casings are formed.

  A latch end 15a is formed on the side surface of the housing. The optical transceiver 10 is housed in a metal rail provided on a circuit board (hereinafter referred to as a host board) of a host device (not shown). The latch end 15a engages with an engagement hole on a side surface of the rail. By this engagement, the optical transceiver 10 is engaged and held in the host device.

A grip 14 is attached to the front part of the housing. By sliding the grip 14 back and forth around the optical receptacle R, the latch end 15a is projected and retracted on the side of the housing, and the optical transceiver 10 and the rail of the host device are engaged or disengaged. can do.
On the upper part of the upper casing 11 constituting the casing, a radiation fin 11a is integrally formed as a heat sink (radiator). The optical transceiver 10 radiates heat from electronic components and the like housed in the casing mainly through the heat radiation fins 11a.

  As shown in FIG. 2, the optical transceiver 10 includes a latch member 15, a transmission optical subassembly (TOSA) 16, a reception optical subassembly (ROSA) 17, an OSA holder 19, A circuit board 20, an IC heat conductive sheet 21, a metal plate 22 and the like are provided.

  The latch member 15 has a part of the latch end 15a described above, and includes a leaf spring 15b that urges the latch end 15a toward the outside of the housing. The latch end 15a is pushed outward by the leaf spring 15b, so that the latched end 15a and the rail on the host board can be kept engaged.

  The TOSA 16 converts an electrical signal into an optical signal and transmits it to an optical fiber included in an optical connector inserted into the optical receptacle R (see FIG. 1). The TOSA 16 is a semiconductor laser (LD: Laser Diode) or the like. The optical transmission device is installed inside. The ROSA 17 converts an optical signal emitted from an optical fiber included in an optical connector inserted into the optical receptacle R (see FIG. 1) into an electric signal, and a photodiode (PD: Photodiode) is provided therein. Equipped with optical receiving devices such as. These OSAs have a coaxial package, and exchange electric signals with an IC (described later) on the circuit board 20. In order to exchange this electric signal, the OSA and the circuit board 20 are electrically connected by a flexible circuit board (not shown).

  The OSA holder 19 is for holding the TOSA 16 and the ROSA 17, and the TOSA 16 and the ROSA 17 are held by the lower housing 12 via the OSA holder 19. The OSA holder 19 is integrally formed with an SC latch 19a that holds an SC type optical connector (SC connector) inserted into the optical receptacle R (see FIG. 1).

The circuit board 20 is mounted with an integrated circuit (IC) 20a as an electronic component for exchanging electrical signals with the TOSA 16 / ROSA 17, and mounted with many other passive components such as an LD driver 20b. Wired by a wiring pattern (not shown) on the substrate 20. Further, the circuit board 20 is housed in the housing, and is fixed to the upper housing 11 by screws (not shown). The lower housing 12 is assembled to the upper housing 11 with a plurality of screws 18 so as to sandwich the circuit board 20.
The heat conductive sheet 21 for IC constitutes the heat dissipation device of the present invention (that is, for dissipating heat generated in the IC 20a), and directly on the heat dissipation surface (the upper surface in FIG. 2) of the IC 20a package. It is provided in the optical transceiver 10 so as to come into contact.

  The heat radiating metal plate (metal member) 22 is a heat transfer member constituting the heat radiating device of the present invention together with the IC heat conductive sheet 21, and is in direct contact with the side opposite to the IC 20a side of the IC heat conductive sheet 21. . The surface of the heat radiating metal plate 22 opposite to the IC heat conduction sheet 21 side faces the upper housing 11, and a heat conductive paste (not shown) is provided between the opposite surface and the upper housing 11. Filled with. Therefore, the metal plate 22 can transfer heat to the upper housing 11 that functions as a heat sink. Further, the metal plate 22 has a groove 22a formed in a closed curve shape having a shape substantially equivalent to the heat dissipation surface of the IC 20a in the peripheral portion of the surface facing the upper housing 11. By forming the groove 22a in this way, the heat conductive paste 23 can be stored in the groove 22a, so that the application amount of the heat conductive paste 23 can be easily controlled.

  Next, the heat dissipation device of the present invention applied to an optical transceiver will be described in detail with reference to FIG. 3A shows an enlarged view of a portion constituting the heat dissipation device of the optical transceiver 10 in FIG. 1, and FIG. 3B shows a state in which the metal plate 22 in FIG. 1 is viewed from above. Yes.

  In the heat radiating device of the present invention, as described above, the heat conductive sheet 21 is placed on the heat radiating surface of the package of the IC 20 a mounted on the circuit board 20, and the metal plate having good heat radiating property is placed on the heat conductive sheet 21. The casing of the optical transceiver functioning as a heat sink and the metal plate are thermally connected via a heat conductive paste. The thickness of the metal plate is set to a value slightly smaller than the distance between the IC package upper surface (heat radiating surface) and the housing inner surface (heat receiving surface).

  The IC 20a has a heat radiating surface formed on the surface opposite to the lower surface (mounting surface) that is mounted on and in contact with the circuit board 20, and includes, for example, a 15 mm square BGA package. The circuit board 20 is composed of an eight-layer printed board or the like, and for example, FR-4 which is a copper-clad board having heat resistance can be used as a base material. Although not shown, the circuit board 20 is attached and fixed to the upper casing 11 with screws. The upper housing 11 has an inner wall surface that is parallel to and opposed to the heat radiation surface of the IC 20a, and an outer wall surface that is exposed to the outside. The upper housing 11 is made of an Al-based metal die-cast to improve heat radiation characteristics. In order to improve, it has the structure which provided the fin for heat radiation in the upper part (outer surface).

  The heat conductive sheet 21 is made of a flame retardant electrical insulator having high heat conductivity and excellent adhesion, and for example, λ paste COH-4000 manufactured by Geltech Co., Ltd. can be used. Further, the heat conductive paste 23 is made of a paste having high heat conductivity and fluidity and being electrically insulating. For example, λ paste DP-100 manufactured by Geltech Co., Ltd. can be used.

  When assembling the heat dissipating device of the present invention, the IC 20a is mounted on the circuit board 20, and the heat conductive sheet 21 having the same size as the package of the IC 20a is placed on the IC 20a. A metal plate 22 for heat dissipation made of the above material is placed. The metal plate 22 is slightly larger than the BGA package. Further, a heat conductive paste 23 is applied on the metal plate 22, and the circuit board 20 is sandwiched between the upper housing 11 and the lower housing 12, so that the metal plate 22 on the IC 20a and the function of a radiator can be achieved. The housing 11 is brought into thermal contact. Thus, the lower side of the metal plate 22 is thermally connected to the IC 20a via the heat conductive sheet 21, while the upper side of the metal plate 22 is made of a metal upper casing via the heat conductive paste 23. 11 is thermally connected.

  The IC 20a, the heat conductive sheet 21, the metal plate 22, and the heat conductive paste 23 are sandwiched between the circuit board 20 and the upper casing 11 in this order, and screws for attaching the circuit board 20 to the upper casing 11 are tightened. Since the heat conductive paste 23 is gel-like and fluid, it easily deforms so as to fill the gap between the metal plate 22 and the upper housing 11. Therefore, it is possible to absorb variations due to the dimensional tolerance of components such as the mounting height of the IC 20 a and the upper housing 11 at the portion where the thickness of the heat conductive paste 23 changes. Therefore, since the heat conductive sheet 21 in contact with the IC 20a is not greatly compressed, pressure that causes damage to the package is not applied to the IC 20a.

  Further, since the heat conductive sheet 21 is arranged between the package of the IC 20a and the metal plate 22, the heat conductive paste 23 adheres to the IC 20a when the circuit board 20 is removed from the upper housing 11 for maintenance. In addition, since there is no need to remove the heat conductive paste, maintenance work can be easily performed.

Furthermore, according to the heat dissipation device of the present invention, the following effects can be obtained.
Optical transceivers have different circuits depending on specifications and functions such as transmission distance and transmission speed. Therefore, the size and arrangement of ICs mounted on a circuit board are different. Moreover, although the heat conductive paste and the heat conductive sheet are excellent in heat conductivity, the heat conductivity is greatly inferior compared to Al-based and Cu-based metals due to material limitations. Therefore, when the distance between the inner surface of the housing functioning as a heat sink and the upper surface of the IC is increased, the heat conduction efficiency is lowered only by filling the space between the two with a heat conductive sheet or a heat conductive paste as in the prior art. Therefore, in the conventional method, it is necessary to prepare a housing for each IC in accordance with the thickness of the IC so that the gap between the IC and the inner surface of the housing is small, which is not desirable from the viewpoint of component costs.

  However, in the heat dissipating device of the present invention, a metal plate is disposed between the IC upper surface and the inner surface of the housing, and the gap between the IC upper surface and the metal plate, or the gap between the metal plate and the inner surface of the housing, respectively, Filled with conductive paste. Therefore, not only can the heat conduction efficiency be greatly improved, but further, by selecting the thickness of the metal plate, the distance between the IC upper surface and the housing inner surface is a predetermined value even if the IC dimensions and arrangement are different. Since it is not necessary to change the shape of the casing so as to become, it is not necessary to prepare a casing for each product type, and the inner surface may be a simple flat surface, so that the processing cost can be suppressed.

  Thus, if the configuration like this optical transceiver is used, even if the type of IC changes and the mounting height changes, the difference can be absorbed by selecting the thickness of the metal plate. In the past, what has been dealt with by changing the shape of the upper housing is not necessary to change the upper housing, and can be handled by selecting the thickness of the metal plate.

  In the conventional optical transceiver shown in FIG. 5, the spread thermal conductive paste sometimes protrudes from the gap between the IC and the casing. For this reason, the protruding thermal conductive paste causes the optical transceiver to vibrate, shock, etc. There was a possibility that when it was received, it would scatter around and contaminate the IC. The heat conductive paste scattered and adhered to the surroundings may have a risk that the characteristics change due to secular change such as moisture absorption, and a defect such as electrical leakage of the circuit may occur.

  In order to prevent this, the metal plate 22 has a groove 22a as shown in FIGS. 3A and 3B so as to surround the outer periphery of the region in contact with the upper housing 11 via the heat conductive paste 23. It is desirable to provide Thus, by digging around the portion of the metal plate 22 that is contacted by the heat conductive paste 23 when assembled as an optical transceiver, even when subjected to a mechanical shock from the outside, the portion of the stepped portion that has been dug down The (groove 22a) can suppress the heat conductive paste 23 from being scattered around.

  In addition, naturally, the thickness of the heat conductive paste 23 changes due to the dimensional variation of the parts, but even if the excess heat conductive paste 23 protrudes around, the heat conductive paste 23 accumulates in the dug down step portion. There is an advantage that the coating amount can be easily controlled. In addition, it is possible to expect an effect of regulating the movement of the metal plate 22 in the planar direction at the dug portion, and the metal plate 22 is detached or greatly displaced due to an external mechanical shock or vibration. Can be suppressed.

  By providing such a groove on the metal plate side instead of the inner surface of the housing, the inner surface of the housing can be made a simple shape (for example, a flat surface). This has the advantage that it is equipped with fins, etc., so that it is not necessary to process a housing that is difficult to process, and there is no need to change the housing when the IC arrangement changes. .

  An optical transceiver including the heat dissipation device of the present embodiment, and an example in which the shape of the housing is changed according to the thickness of the IC package, the space between the housing and the IC package is narrowed, and the gap is filled with a heat conductive paste. The difference in heat dissipation characteristics was evaluated. As the heat conductive sheet and heat conductive paste of the optical transceiver of this example, those having a heat conductivity of 6.5 W / m · K were used. At this time, it was confirmed that the optical transceiver of this example had a temperature difference at the upper part of the casing of about 2 to 3 ° C. with respect to the comparison target, and there was no practical problem.

On the other hand, the vibration test (MIL-STD-883 Method 2007 Cond. A 20G, 20-2,000Hz, 4min / cy, 4cy / axis) and impact test (impact on mechanical shock are required for ordinary optical modules) MIL-STD-883 Method 2002 5times / axis 1,500G, 0.5ms). In the optical transceiver using the heat dissipation device of this example, it was confirmed that there was no significant change such as the metal plate for heat dissipation being shifted before and after the test, and the structure of the heat dissipation device of this example was mechanically reliable. In the test, it was confirmed that the structure had no problem.
In addition, this invention is not limited to said Example, Various things, such as an electroconductive material and a solvent to be used, can be utilized.

  Also, if the heat conductive paste has a particularly low viscosity or is exposed to severe vibration, it is not sufficient to provide a groove as a measure against the heat conductive paste scattering. You may make it close with. The tape is, for example, a 30 mm x 30 mm square, 0.1 mm thick polyimide sheet coated with adhesive paste, with a square hole so that the metal plate is exposed at the center. It is a thing. By sticking such a tape to the upper housing side, even if the heat conductive paste has a particularly low viscosity and is subjected to severe vibration, the heat conductive paste can be used without being scattered around.

  As described above, according to the present invention, since the heat conductive sheet and the heat conductive paste are used in combination, the heat conductive sheet does not depend on the mounting height on the circuit board or the dimensional variation of the components. The pressing force can be suppressed. In addition, by using a heat conductive sheet as a means of contact between the metal plate for heat dissipation and the IC, it is possible to avoid contamination of the IC and the mounting substrate around the IC with a heat conductive paste, etc., so good maintainability Can be secured.

In addition, since a metal plate is interposed between the heat conductive sheet and the heat conductive paste, when the electro-optical specifications such as transmission distance and transmission speed are changed, the dimensions and arrangement of the IC are changed. When the height changes, by changing the thickness of the metal plate, it is possible to ensure the same heat dissipation as when the shape of the housing is changed according to the IC. That is, it is possible to reduce the cost by making the housing of the optical transceiver common without impairing heat dissipation.
In addition, by providing a groove on the metal plate side to prevent heat conduction paste from being scattered, it is not necessary to change the housing that is difficult to process even if there is a change in the dimensional arrangement of the IC, etc. Cost can be reduced.

It is a figure explaining an example of the optical transceiver to which the thermal radiation apparatus by this invention is applied. It is a figure explaining an example of the optical transceiver to which the thermal radiation apparatus by this invention is applied. It is a figure explaining the thermal radiation apparatus by this invention. It is a figure explaining the thermal radiation apparatus applied to the conventional optical transceiver. It is a figure explaining the thermal radiation apparatus applied to the other conventional optical transceiver.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Optical transceiver, 11 ... Upper housing | casing, 11a ... Radiation fin, 12 ... Lower housing | casing, 13 ... Cover, 14 ... Grip, 15 ... Latch member, 15a ... Latch end, 15b ... Leaf spring part, 16 ... TOSA, 17 ... ROSA, 18 ... screw, 19 ... OSA holder, 20 ... circuit board, 20a ... electronic circuit (IC), 21 ... heat conduction sheet, 22 ... metal plate, 22a ... groove, 23 ... heat conduction paste.

Claims (3)

  A heat dissipation device that dissipates heat generated by an electronic component mounted on a circuit board to the outside through a housing that houses the circuit board, wherein a heat conductive sheet is disposed on a heat dissipation surface of the electronic component. A metal plate is placed on the heat conductive sheet, a heat conductive paste is interposed between the metal plate and the inner wall surface of the housing, and the heat generated by the electronic component is transferred to the heat conductive sheet and the metal. A heat radiating device, wherein the heat radiating device is transmitted to the casing through a plate and the heat conductive paste.   The heat dissipating device according to claim 1, wherein the metal plate is provided with a groove in a peripheral portion of a surface facing the housing.   An optical transceiver comprising the heat dissipating device according to claim 1.

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