WO2010036092A2

WO2010036092A2 - Thermal management for an optical system

Info

Publication number: WO2010036092A2
Application number: PCT/MY2009/000155
Authority: WO
Inventors: Seck Jiong Wong; Witjaksono Gunawan
Original assignee: Mimos Berhad
Priority date: 2008-09-25
Filing date: 2009-09-25
Publication date: 2010-04-01
Also published as: MY146161A; WO2010036092A3

Abstract

An optomechanical assembly (10) is disclosed for enhancing the thermal dissipation performance of an optical system within an enclosure (12). The optical module (11) of the optical system includes a heat sink surface (20) which connects the optical module (11) to the enclosure (12). A cooling device (25) is placed between the heat sink (20) and the enclosure (12) to create high heat potential hence better dissipation. The enclosure (12) is provided with cooling elements (23) and venting holes (22) to promote better heat removal via natural convection.

Description

Thermal Management for an Optical System

Field of Invention

The present invention relates generally to the field of optical system and more particularly to a thermal dissipation management of an optical system within an enclosure.

Background of the Invention

The operation of an optical system often, involves detection of light by a photodetector and conversion of energy into electrical signals. In the process, heat or thermal energy is produced. In most cases for very sensitive photodetector, significant amount of heat or thermal energy is generated and this can significantly impair the optical performance of the system. It is always desired to remove as much heat as possible from the system. This must be done in the shortest period of time because heat can accumulate within the system.

In order to reduce thermal heating of the optical system, current practice would attempt to attach thermoelectric coolers to the photodetector for cooling purposes because of their compactness, cost-effectiveness and their low power consumption. However, this approach will not solve the problem because the photodetector is packaged within a TO-can or a butterfly can and these in turn is packaged within an enclosure. The enclosure is the packaging for the optical system together with its interface electrical circuits. Although heat has been extracted from, the optical package system, heat still remains within the enclosure around the TO can. This is because the path for heat dissipation between the TO can to the enclosure is still missing.

Other conventional solution would be installing forced -convection cooling mechanisms such as fans and blowers within the enclosure to extract heat from the optical system. When fan and blowers are installed to remove heat, by forced convection, the obvious disadvantages that entailed are the size of the packaging become bigger than required and bulky, the power consumption of the overall system increases tremendously, hence an increase in cost as well.

The present invention has overcome the drawbacks of the existing methods by providing significantly improved .thermal management scheme for the optomechanical .system.

An objective of the present invention is to provide an optomechanical assembly having a thermoelectric cooler attached between the optoelectronic module and the enclosure to enhance the heat dissipation mechanism. The present invention also seeks to provide an efficient thermal dissipation scheme for the optomechanical assembly of the present invention by providing cooling fins and venting holes around the enclosure to promote better heat removal via natural convection.

Yet another objective of the present invention is to provide heat sink that connects the optoelectronic module to the enclosure directly using thermal interface material.

Other objects of this invention will become apparent on the reading of this entire disclosure.

Summary of the Invention

In the present invention, an optomechanical assembly comprising an enclosure which comprises a base plate and cover, an optoelectronic module held on the base plate having a holder provided with heat sink surface in an optical coupling with at least one optoelectronic device, and a cooling device provided on the holder and in proximity with the enclosure as a thermal link for the heat dissipation path between the optoelectronic module and enclosure. The enclosure is also provided with cooling elements and a plurality of venting holes. In accordance to the present invention, the cooling device comprises a thermoelectric cooler and a thermal conductive pad attached thereon.

Brief Description of the Drawings

Other objects, features, and advantages of the invention will be apparent from the following description when read with reference to the accompanying drawings. In the drawings, wherein like reference numerals denote corresponding parts throughout the several views:

Fig. 1 shows a perspective view of an optomechanical assembly of the present invention without the cover of the enclosure;

Fig. 2 depicts a perspective view of an optoelectronic module of the optomechanical assembly of Fig. 1;

Fig. 3 is a perspective view of the optomechanical assembly of Fig. 1 with additional circuit board attached therein; and

Fig. 4 illustrates a perspective view -of the optomechanical assembly together with the enclosure. Detailed Description of the Preferred Embodiments

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known methods, procedures and/or components have not been described in detail so as not to obscure the invention. Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

Fig. 1 provides a schematic perspective view representation of an optomechanical assembly in accordance to the preferred embodiment of the invention, for support of the optical and optoelectronic devices which is suitable in application areas such as physical random number generation, optical communications and the like. The optomechanical assembly is generally designated by the numeral 10. The optomechanical assembly (10) includes an enclosure (12) which packages an optoelectronic module (11) together with circuit board (13) with several apparatus, which is able to dissipate heat generated from a photoelectronic device (14) within the optoelectronic module (11) to the surrounding environment. The optoelectronic module (11) houses at least one optoelectronic device (14) such as a photodetector (14") or a laser diode (14').

The enclosure (12) includes a base plate (12a) and a cover (12b) for housing the optoelectronic module (11) and the circuit board (13) . The optoelectronic module (11) is shown mounted on the base plate (12a) and connected to the circuit board (13) either directly through soldering or via a flexible circuit (15) as shown in Fig. 1. During operation, the optoelectronic device (14) will dissipate heat and it is crucial that the heat generated is transmitted away from the optoelectronic device (14). However, as the optoelectronic module (11) is housed in the enclosure (12), therefore the air surrounding the optoelectronic module (11) will be confined within the enclosure (12).

The optomechanical assembly (10) of the present invention provides an enhanced heat removal capability via conduction and convection method to dissipate heat from the optoelectronic module (11) as well as the electronics circuit (13) to the enclosure (12) and subsequently to the outside environment of the enclosure (12). This will thus prevent accumulation of heat on the body of the optoelectronics module (11) . The present invention does not ^' intend to solve the thermal dissipation issue within the optoelectronic module (ID • Referring to Fig. 2, the optoelectronic module (11) has a holder (lla) with an internal bore (16) having one end of the holder (Ha) connected to a body (17) and attached with an optoelectronic device (14) such as laser diode (14'), and the other end to accommodate another optoelectronic device (14) such as a photodetector (14") packaged in the form of Transistor Outline (TO) can and affixed therein. The holder (Ha) has a heat sink surface (20) to drive away the heat from the optoelectronic device (14) . The holder (Ha) also provides a facet to be connected to the enclosure (12) by a cooling device (25) . The cooling device (25) includes a thermoelectric cooler (18) and a thermal conductive pad (19) attached thereon to be connected to the enclosure (12) .

The optomechanical assembly (10) fosters heat generated from the optoelectronic device (14) to be transferred to the heat sink surface (20) through the contact between the TO-can of the photodetector (14") and the heat sink surface (20) . Then, the thermoelectric cooler (18) will draw the heat from the heat sink surface (20) to the enclosure (12) through the thermal conductive pad (19) .

An additional heat spreader plate (21) is vertically attached at one edge of the base plate (12a) that contact the semiconductor chips on the circuit board (13) and acts as a heat sink that spread the heat generated over a larger area as shown in Fig. 3. Additional circuit board (13') may be added to the optomechanical assembly (10) by attaching it to the heat spreader plate (21) . The heat spreader plate (21) provides not only strong mechanical support but a good thermal contact so that there will be adequate heat transfer of the internal parts of the optomechanical assembly (10) to the outside environment.

The entire arrangement is then enclosed by the cover (12b) of the enclosure (12) which is seallably affixed to the base plate (12a) and the heat spreader plate (21) via sealing mechanism as shown in Fig. 4. The enclosure (12) together with the heat spreader plate (21) has features that enhance convective cooling of the optoelectronic module (11) within it. The cover (12b) of the enclosure (12) is also provided with a plurality of air vents (22) at the side of the cover (12b) to allow cool air to enter the enclosure (12) and at the top of the cover (12b) to allow hotter air to exit from the enclosure (12) .

Cooling elements (23) such as cooling fins are erected at the cover (12b) of the enclosure (12) to increase surface area which will further enhance convective cooling. The cooling fins (23) are preferably erected at the top area of the cover (12b) which is directly above the thermoelectric cooler (18) and thermal conductive pad (19) to serve act a thermal link path from the optoelectronic module (11) to the outer surfaces of the enclosure (12) .

As will be readily apparent to those skilled in the art, the present invention may easily be produced in other specific forms without departing from its essential characteristics. The present embodiments is, therefore, to be considered as merely illustrative and not restrictive, the scope of the invention being indicated by the claims rather than the foregoing description, and all changes which come within therefore intended to be embraced therein.

Claims

1. An optomechanical assembly (10) comprising: an enclosure (12) which comprises a base plate (12a) and cover (12b), wherein said enclosure (12) is provided with cooling elements (23) and a plurality of venting holes (22) ; an optoelectronic module (11) held on said base plate (12a) having a holder (lla) provided with heat sink surface (20) in an optical coupling with at least one optoelectronic device (14); and a cooling device (25) provided on said holder (Ha) of the optoelectronic module (11) and in proximity with said enclosure (12) as a thermal link for the heat dissipation path between said optoelectronic module (11) and enclosure (12) .

2. The optomechanical assembly (10) as claimed in claim 1, wherein said cooling device (25) comprises a thermoelectric cooler (18) and a thermal conductive pad (19) attached thereon.

3. The optomechanical assembly (10) as claimed in claim 1, wherein said optoelectronic module (11) is connected to a circuit board (13) and housed within said enclosure (12).

4. The optomechanical assembly (10) as claimed in claim 3, wherein said optoelectronic module (11) having its holder (lla) formed with an internal bore (16) enabling affixing at least one optoelectronic device (14) therein.

5. The optomechanical assembly (10) as claimed in claim 4, wherein said optoelectronic device (14) is a photodetector (14") packaged in the form of Transistor Outline (TO) can and in contact with said heat sink surface (20) of said holder (Ha) .

6. The optomechanical assembly (10) as claimed in claims 1 and 3, wherein said assembly (10) further comprising a heat spreader plate (21) vertically attached at one edge of said base plate (12a) and in contact with said circuit board (13).

7. The optomechanical assembly (10) as claimed in claim 6, wherein said assembly (10) may be added with additional circuit board (13' ) by attaching it to said heat spreader plate (21) .

8. The optomechanical assembly (10) as claimed in claim 1, wherein said venting holes (22) are provided at the side of said cover (12b) of the enclosure (12) to allow cool air to enter said enclosure (12) .

9. The optomechanical assembly (10) as claimed in claim 1, wherein said venting holes (22) are provided at the top of said cover (12b) of the enclosure (12) to allow hot air to exit from said enclosure (12).

10. The optomechanical assembly (10) as claimed in claim 1, wherein said cooling elements (23) are cooling fins erected at said cover (12b) of the enclosure (12).

11. The optomechanical assembly (10) as claimed in claim 10, wherein said cooling fins (23) are erected at the top area of said cover (12b) which is directly above said cooling device (25).