WO2012002796A1

WO2012002796A1 - A heat sink and a method of enhancing heat dissipation thereof

Info

Publication number: WO2012002796A1
Application number: PCT/MY2011/000051
Authority: WO
Inventors: Muhammad Syargawi Abdullah; Gunawan Witjaksono
Original assignee: Mimos Berhad
Priority date: 2010-06-28
Filing date: 2011-05-23
Publication date: 2012-01-05
Also published as: MY154642A

Abstract

A heat sink in an electronic circuit board (PCB) comprising a plurality of PCB layers (10) wherein a first PCB layer (100) is mountable with a plurality of electronic components (140) is provided, characterized in that, the heat sink includes at least one optical component (102) mountable on a first heat spreader (103), by a thermal cohesive means (104), wherein the first heat spreader (103) is attachable to the first PCB layer (100), a second PCB layer (110) is thermally conductible to the first PCB layer (100) by at least one thermal via (112), a third PCB layer (120) is thermally conductible to the second PCB layer (110) by the at least one thermal via (112), a bottom PCB layer (130) is thermally conductible to the third PCB layer (120) by the at least one thermal via (112), such that heat is conductible through the plurality of PCB layers (10) for enhanced thermal dissipation from the plurality of electronic components (140).

Description

A HEAT SINK AND A METHOD OF ENHANCING HEAT DISSIPATION THEROF

FIELD OF INVENTION The present invention relates to a heat sink in an electronic printed circuit board (PCB) and a method of enhancing thermal dissipation thereof.

BACKGROUND OF INVENTION Optoelectronics circuits include a combination of at least one optical component and at least one electrical circuit thereby providing electrical and optical functions in one device. It becomes more important that optoelectronics circuits, including the electronics and optical components be miniaturized. This miniaturization however can lead to some other problems.

One of the problems that are usually encountered with miniaturized optoelectronics devices is amount of eat created. While the size of the miniaturized device becomes smaller, the amount of heat that is generated from the devices remains the same regardless of its size. As such, the miniaturized optoelectronics devices have to dissipate more heat for a given volume. The heat, if not controlled, will degrade the performance and lifetime of optical components and this will result in unreliable and unstable optoelectronics circuit performance. This situation will get worse in an enclosed system where, the heat is trapped inside the enclosure. Because of the miniaturized nature of the circuit, traditional heat remover apparatus such as cooling fan, big heat sink and thermal electro coupler (TEC) would be irrelevant. There are already a few attempts to address the thermal issue on the optoelectronics circuit board effectively but however the solutions are expensive, space consuming, bulky and complex. US 5,077,638 describes a heat sink and a circuit board that allows a number of circuit boards with neat sinks to be simply mounted on the same housing. An arrangement was designed with an electric circuit board on which at least one heat-generating component is mounted which requires cooling. A circuit board is mounted to a heat sink. A heat sink which according to this invention is designed with a slot for the one side edge of the circuit board makes it possible for the heat sink to be simply fixed to the circuit board. However, the prior art still consumes a lot of space and the slot is in a fixed specific shape that does not allow modular solutions by integrating with other systems. Therefore, it is a challenging task to for providing a solution that addresses the issue of miniaturization and thermal management. It would be desirous to design the solution in such a way that it can be cost effective, compact and easy to implement.

SUMMARY OF INVENTION

Accordingly there is provided a heat sink in an electronic printed circuit board (PCB) comprising a plurality of PCB layers wherein a first PCB layer is mountable with a plurality of electronic components, characterized in that, the heat sink includes at least one optical component mountable on a first heat spreader by a thermal cohesive means, wherein the first heat spreader is attachable to the first PCB layer, a second PCB layer mountable with a second heat spreader, wherein the second PCB layer is thermally conductible to the first PCB layer by at least one thermal via, a third PCB layer is thermally conductible to the second PCB layer by the at least one thermal via, a bottom PCB layer mountable with a third heat spreader, wherein the bottom PCB layer is thermally conductible to the third PCB layer by the at least one thermal via, such that heat is conductible through the plurality of PCB layers for enhanced thermal dissipation from the plurality of electronic components.

There is also provided a method of enhancing thermal dissipation of an electronic printed circuit board (PCB), the method includes the steps of mounting a plurality of electronic components on a first PCB layer, mounting at least one optical component on a first heat spreader by thermal paste, mounting a second PCB layer with a second heat spreader by thermally connecting the second PCB layer to the first PCB layer, thermally connecting a third PCB layer to the second PCB layer, mounting a third heat spreader to a bottom PCB layer by thermally connecting the bottom PCB layer to the third PCB layer, such that heat is conducted through the plurality of PCB layers for enhanced thermal dissipation from the plurality of electronic components. ^"The present invention consists of several novel features, and a combination of parts hereinafter fully described and illustrated i the accompanying description and drawings, it being understood that various changes in the details may be made without departing from the scope of the invention or sacrificing any of the advantages of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, wherein:

Figure 1 illustrates a 3 dimensional view of the preferred embodiment of the invention;

Figure 2 illustrates a top view of the first PCB layer in the preferred embodiment of the invention;

Figure 3 illustrates the optical component on the first PCB layer in the preferred embodiment of the invention ;

Figure 4 illustrates the layout of the first PCB layer in the preferred embodiment of the invention;

Figure 5 illustrates the layout of the second PCB layer in the preferred embodiment of the invention; Figure 6 illustrates the layout of the third PCB layer in the preferred embodiment of the invention;

Figure 7 illustrates the layout of the bottom PCB layer in the preferred embodiment of the invention;

Figure 8 illustrates a graphical representation of comparison between operating temperature of the optical component without the heat sink and with the heat sink in the preferred embodiment of the invention; and Figure 9 illustrates a graphical representation of comparison between performance of the optical component without the heat sink and with the heat sink in the preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention relates to a heat sink in an electronic printed circuit board (PCB) and a method of enhancing thermal dissipation thereof: Hereinafter, this specification will describe the present invention according to the preferred embodiment of the present invention. However, it is to be understood that limiting the description to the preferred embodiment of the invention is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications and equivalents without departing from the scope of the appended claims.

The following detailed description of the preferred embodiment will now be described in accordance with the attached drawings, either individually or in combination. Figure 1 shows a preferred embodiment of a heat sink in an electronic printed circuit board (PCB) comprising a plurality of PCB layers (10) wherein a first PCB layer (100) is mountable with a plurality of electronic components (140). The heat sink includes at least one optical component (102) mountable on a first heat spreader (103) by a thermal cohesive means (104), wherein the first heat spreader (103) is attachable to the first PCB layer (100) as seen in Figure 2 and Figure 3. Figure 4 shows a first PCB layer layout (105). in Figure 5, a second PCB layer ( 110) is mountable with a second heat spreader (111), wherein the second PCB layer (110) is thermally conductible to .the first PCB layer (100) by at least one thermal via (112) in a second PCB layer layout (113). In Figure 6, a third PCB layer (120) is thermally conductible to the second PCB layer (110) by the at least one thermal via (112). In Figure 7, a bottom PCB layer (130) is mountable with a third heat spreader (132), wherein the bottom PCB layer is thermally conductible to the third PCB layer (120) by the at least one thermal via (1 2), such that heat is conductible through the plurality of PCB layers (10) for enhanced thermal dissipation from the plurality of electronic components (140) in an efficient manner.

The plurality of electronic components (140) may be selected from,, but not restricted to, electrical, electronic and optical components to be mounted on the first PCB layer (100). The thermal cohesive means used in the preferred embodiment is thermal paste to ensure that the at least one optical component (102) is mounted steadily on the first heat spreader (103).

It is to be understood that the first heat spreader (103), the second heat spreader (111) and the third heat spreader (132) are constructible with thermally conductive material, such as copper. It is to be appreciated that embodiments of the invention may use other thermally conductive material and is not restricted to copper.

The present invention utilizes multi layer PCB fabrication technology as a medium to dissipate heat from optical, electrical and electronic devices from the first PCB layer (100) to the bottom PCB layer (130) through the at least one thermal via (112) incorporated within the plurality of PCB layers (10). The first heat spreader (103) on top surface of the first PCB layer (100) is a thermally conductive sheet such as a copper sheet that dissipates heat and is attached directly to the at least one optical component (102) by thermal paste. Heat is produced by the plurality of electronic components (140) or the at least one optical component (102), or a combination of both. The heat produced in this way may critically affect performance of a device of which the plurality of electronic components (140) or the at least one optical component (102) are a part of. Without any effort to manage the heat, the performance of circuitry could be impaired. Optical devices exposed to excessive heat even for a short period may experience drastic degradation of life span and optical performance of the device.

A method of enhancing thermal dissipation of an electronic printed circuit board (PCB) is described herein. The method includes the steps of mounting a plurality of electronic components (140) on a first PCB layer (100) and mounting at least one optical component (102) on a first heat spreader (103) by thermal paste, wherein the first heat spreader (103) is attached to the first PCB layer (100). The first PCB layer (100) is where the plurality of electronic components (140) and the first heat spreader (103) are mounted and placed as shown in Figure 2. The at least one optical component (102) is mounted on the first heat spreader (103) through a thermal paste as seen in Figure 3. Figure 4 depicts a first PCB layer layout (105).

The method is further carried out by mounting a second PCB layer (110) with a second heat spreader (111) wherein the second PCB layer (1,10) is thermally connected to the first PCB layer (100) by at least one thermal via (112) as seen in Figure 5. Heat from the plurality of electroriie components (140) and the at least one optical component (102) is transferred to the second heat spreader (111) in the second PCB layer (110) through the at least one thermal via (112). Figure 5 also shows the second PCB layer layout ( 3). Further, a third PCB layer (120) is thermally connected to the second PCB layer (110) by the at least one thermal via (112) as seen in Figure 6. A bottom PCB layer (130) is mounted with a third heat spreader (132) wherein the bottom PCB layer (130) is thermally connectable to the third PCB layer (120) by the at least one thermal via (112), as seen in Figure 7, such that heat is conducted through the plurality of PCB layers for enhanced thermal dissipation from th plurality of electronic components (140).

The first heat spreader (103), the second heat spreader (111) and the third heat spreader (132) are constructed from copper. It is to be appreciated that embodiments of the invention may use other thermally conductive material and is not restricted to copper.

The heat sink has been tested by stability tests and results of said tests are .depicted in Figure 8 and Figure 9.

Figure 8 represents results of operating temperature of the at least one optical component (102) over a period of time. Figure 8(b) shows a graphical representation of a period of time for the at least one optical component (102) to be stabilized with the heat sink, which is at 5 minutes. However, Figure 8(a) shows that the at least one optical component (102) was stabilized only after 20 minutes without the heat sink. Therefore, the heat sink allows for better stabilization of components from the test results. Figure 9 represents results of performance of the at least one optical component (102) over a period of time. Figure 9(b) shows that the performance of the at least one optical component (102) was stable after the first 5 minutes using the heat sink. However, Figure 9(a) shows that the performance of the at least one optical component (102) was stabilized only, after more than 1 hour without implementation of the heat sink. Therefore, the heat sink allows for better stabilization of performance from the test results.

Therefore, the invention is suitable for use in applications such as, but not restricted to, PCBs in optoelectronic applications for enhancing heat dissipation from components.

Claims

1 , A heat sink in an electronic printed circuit board (PCB) comprising a plurality of PCB layers (10) wherein a first PCB layer (100) is mountable with a plurality of electronic components (140), characterized in that, the heat sink includes: at least one optical component ( 02) mountable on a first heat spreader (103) by a thermal cohesive means (104), wherein the first heat spreader (103) is attachable to the first PCB layer ( 00);

a second PCB layer (110) mountable with a second heat spreader (111 ), wherein the second PCB layer (110) is thermally conductible to the first PCB layer (100) by at least one thermal via (112);

a third PCB layer (120) is thermally conductible to the second PCB layer ( 110) by the at least one thermal via (112);

a bottom PCB layer (130) mountable with a third heat spreader (132), wherein the bottom PCB layer (130) is thermally conductible to the third PCB layer (120) by the at least one thermal via (112),

such that heat is conductible through the plurality of PCB layers (10) for enhanced thermal dissipation from the plurality of electronic components (140).

2. The heat sink as claimed in claim 1, wherein the plurality of electronic components (140) includes electrical, electronic and optical components.

3. The heat sink as claimed in claim 1, wherein the thermal cohesive means (104) is thermaf paste.

4. The heat sink as claimed in claim 1, wherein the first heat spreader (103), the second heat spreader (111) and the third heat spreader (132) are constructible with thermally conductive material.

The heat sink as claimed in claim 4, wherein the thermally conductive material copper.

6. The heat sink as claimed in claim 1 , wherein the heat sink is used in optoelectronic applications.

7. A method of enhancing thermal dissipation of an electronic printed circuit board (PCB), the method includes the steps of:

i. mounting a plurality of electronic components (140) on a first PCB layer (t00);

ii. mounting at least one optical component ( 02) on a first heat spreader (103) by thermal paste;

Hi. mounting a second PCB layer (110) with a second heat spreader (111) by thermally connecting the second PCB layer (110) to the first PCB layer (100);

iv. thermally connecting a third PCB layer (120) to the second PCB layer (110);

v. mounting a third heat spreader (132) to a bottom PCB layer (130) by thermally connecting the bottom PCB layer (130) to the third PCB layer (120); such that heat is conducted through the plurality of PCB layers (10) for enhanced thermal dissipation from the plurality of electronic components (140).

8. The method as claimed in claim 7, wherein the plurality of electronic components (140) includes electrical, electronic and optical components.

9. The method as claimed in claim 7, wherein the first heat spreader (103), the second heat spreader (111) and the third heat spreader (132) are constructed of thermally conductive material.

10. The method as claimed in claim 9, wherein the thermally conductive material is copper.

11. The method as claimed in claim 7, wherein the method is used in optoelectronic applications.