WO2018125974A1

WO2018125974A1 - Split heat sink

Info

Publication number: WO2018125974A1
Application number: PCT/US2017/068656
Authority: WO
Inventors: Rami HAKAM
Original assignee: Littelfuse Inc
Current assignee: Littelfuse Inc
Priority date: 2016-12-28
Filing date: 2017-12-28
Publication date: 2018-07-05
Anticipated expiration: 2019-06-28

Abstract

Provided herein are various split heat sinks. In one approach, a heat sink apparatus includes a first heat sink coupled to a second heat sink, and a membrane coupled to a first side of the first heat sink and disposed between the first heat sink and the second heat sink. In some approaches, the membrane includes a phase change material (PCM). The heat sink apparatus may further include a semiconductor device coupled to a second side of the first heat sink. In some approaches, the heat sink apparatus includes a support frame coupled to the second heat sink. In some approaches, the heat sink apparatus includes additional PCM disposed within the first heat sink and/or the second heat sink. In some approaches, the heat sink apparatus includes one or more fluid conduits formed therein.

Description

SPLIT HEAT SINK

Cross-Reference to Related Application

[0001] This application claims priority to U.S. Provisional Patent Application No.

62/439,673, filed December 28, 2016, the entire contents of which are incorporated by reference herein.

Field of the Disclosure

[0002] The disclosure relates generally to heat sinks for semiconductor devices and, more particularly, to split heat sinks having first and second heat sinks coupled together.

Background of the Disclosure

[0003] Transistor devices, such as insulated gate bipolar transistors (IGBT), have become increasingly common because IGBT's are able to handle a relatively high power density by connecting a dozen or more individual gates in parallel. However, the increasing power density of such devices has pushed traditional electronic cooling to its limits.

[0004] One known heat removal approach includes coupling a heat sink to a PC/IGBT board containing the IGBT. Heat sinks are typically comprised of a metal having a high thermal conductivity, and may be mounted upon the PC board for limiting the operating temperature of electronic components positioned in circuit upon the board. The heat sink ideally provides a high degree of heat transfer and thermal dissipation to accommodate the increased density of the electronic circuitry associated therewith. Increasing the thermal dissipation by means of convection generally requires increasing the surface area per unit volume of the heat sink. However, having the heat sink occupying only a minimum area on the PC board is beneficial to permit high density electronic component packaging. These competing aims represent a significant problem with existing cooling technology. Summary

[0005] In view of the foregoing, provided herein are various split heat sinks. In one approach, a heat sink apparatus includes a first heat sink coupled to a second heat sink, and a membrane coupled to a first side of the first heat sink and disposed between the first heat sink and the second heat sink. In some approaches, the membrane includes a phase change material (PCM). The heat sink apparatus may further include a semiconductor device coupled to a second side of the first heat sink. In some approaches, the heat sink apparatus includes a support frame coupled to the second heat sink. In some approaches, the heat sink apparatus includes additional PCM disposed within the first heat sink and/or the second heat sink. In some approaches, the heat sink apparatus includes one or more fluid conduits formed therein.

[0006] One exemplary approach in accordance with the present disclosure may include a heat sink apparatus having a first heat sink coupled to a second heat sink, a membrane coupled to a first side of the first heat sink and disposed between the first heat sink and the second heat sink, wherein the membrane includes a phase change material (PCM), and a semiconductor device coupled to a second side of the first heat sink.

[0007] Another exemplary approach in accordance with the present disclosure may include a split heat sink having a first heat sink coupled to a second heat sink, a membrane coupled to a first side of the first heat sink and disposed between the first heat sink and the second heat sink, wherein the membrane includes a phase change material (PCM), and a support frame coupled to the second heat sink and disposed adjacent the first heat sink.

[0008] Another exemplary approach in accordance with the present disclosure may include a split heat sink apparatus having a first heat sink coupled to a second heat sink, the second heat sink defining a first section and a second section, the second section comprising at least one cooling fin. The split heat sink apparatus may further include a phase change material (PCM) coupled to first side of the first heat sink, the PCM disposed between the first heat sink and the second heat sink, and a semiconductor device coupled to a second side of the first heat sink. The split heat sink apparatus may further include a support frame coupled to the second heat sink, the support frame disposed directly adjacent an outer edge of the first heat sink.

Brief Description of the Drawings

[0009] FIG. 1 is a side view of a heat sink apparatus according to exemplary embodiments of the disclosure.

[0010] FIG. 2 is an exploded side cross-sectional view of the apparatus shown in FIG.

1 according to exemplary embodiments of the disclosure.

[0011] FIG. 3 is an exploded side cross-sectional view of the apparatus shown in FIG.

1 according to exemplary embodiments of the disclosure.

[0012] FIG. 4 is an exploded side cross-sectional view of the apparatus shown in FIG.

1 according to exemplary embodiments of the disclosure.

[0013] FIG. 5 is a side view of the heat sink apparatus including a cooling conduit formed therein according to exemplary embodiments of the disclosure.

[0014] The drawings are not necessarily to scale. The drawings are merely representations, not intended to portray specific parameters of the disclosure. The drawings are intended to depict typical embodiments of the disclosure, and therefore should not be considered as limiting in scope. In the drawings, like numbering represents like elements.

[0015] Furthermore, certain elements in some of the figures may be omitted, or illustrated not-to-scale, for illustrative clarity. Cross-sectional views may be in the form of "slices", or "near-sighted" cross-sectional views, omitting certain background lines otherwise visible in a "true" cross-sectional view, for illustrative clarity. Furthermore, for clarity, some reference numbers may be omitted in certain drawings. Detailed Description

[0016] Embodiments in accordance with the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings. The heat sink/heat sink apparatus may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the system and method to those skilled in the art.

[0017] For the sake of convenience and clarity, terms such as "top," "bottom," "upper,"

"lower," "vertical," "horizontal," "lateral," and "longitudinal" will be used herein to describe the relative placement and orientation of these components and their constituent parts, each with respect to the geometry and orientation of the heat sink apparatus as it appears in FIGS. 1-4. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.

[0018] As used herein, an element or operation recited in the singular and proceeded with the word "a" or "an" should be understood as not excluding plural elements or operations, unless such exclusion is explicitly recited. Furthermore, references to "one embodiment" of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

[0019] As stated above, approaches herein provide a heat sink apparatus including a first heat sink coupled to a second heat sink, and a membrane coupled to a first side of the first heat sink and disposed between the first heat sink and the second heat sink. In some approaches, the membrane includes a phase change material (PCM). The heat sink apparatus may further include a semiconductor device coupled to a second side of the first heat sink. In some approaches, the heat sink apparatus includes a support frame coupled to the second heat sink. In some approaches, the heat sink apparatus includes additional PCM disposed within the first heat sink and/or the second heat sink. In some approaches, the heat sink apparatus includes one or more fluid conduits formed therein.

[0020] Referring now to FIG. 1, a side view of an exemplary heat sink apparatus/system (hereinafter, apparatus 100) in accordance with the present disclosure will be described in greater detail. In exemplary embodiments, the apparatus 100 includes a first heat sink 104 coupled to a second heat sink 108, and a membrane 110 coupled to a first side 112 of the first heat sink 104 such that the membrane 110 is disposed between the first heat sink 104 and the second heat sink 108. As shown, the first heat sink 104 may be coupled to the second heat sink 108 using one or more fasteners 114, such as screws, bolts, clamps, clasps, and/or an adhesive. One or more semiconductor devices 120, such as an insulated gate bipolar transistor (IGBT), may be coupled to a second side 122 of the first heat sink 104, for example. In some embodiments, the semiconductor device 120 may be formed on a PC board (not shown), which is then secured to the second side 122 of the first heat sink 104.

[0021] In other non-limiting embodiments, the semiconductor device 120 may be a microprocessor, memory device, micro electro-mechanical system (MEMS), network communications device, laser emitter, radio-frequency component, integrated circuit, etc. Each of the semiconductor devices 120 produces some respective amount of heat that is removed by the first and second heat sinks 104 and 108, as will be further described below.

[0022] The membrane 110 may be secured to the first heat sink 104 and/or the second heat sink 108, for example via the fasteners 114, thereby allowing the membrane 110 to be removed for replacement. In some embodiments, the membrane 110 may be a flexible phase change material (PCM) in contact with both the first heat sink 104 and the second heat sink 108. The PCM helps reduce the overall weight of the apparatus 100 and is configured to change phase from a solid state to a liquid state at a predetermined heat storage temperature greater than a normal operating temperature. For example, the temperature of the PCM of the membrane 110 also begins to rise with that of the first heat sink 104 and/or the second heat sink 108. As the temperature eventually rises to the temperature of fusion for the PCM, the PCM begins to store heat by transitioning from solid to liquid state. During this heat storage period, the first heat sink 104 and/or the second heat sink 108 exhibit thermal equilibrium at a new temperature a few degrees greater than the normal operating temperature. Illustrative and non-limiting examples of such PCM include paraffin, glycol mixtures, formamide, salt and water mixtures, etc. Other suitable PCMs can also be used. Furthermore, in some embodiments, no membrane is present between the first and second heat sinks 104, 108.

[0023] The apparatus 100 may further include a support frame 130 coupled to the second heat sink 108 using one or more fasteners 132, such as screws, bolts, clamps, clasps, and/or an adhesive. As shown, the support frame 130 has an L-shaped cross-section, which generally conforms to a cutout or recess 134 of the second heat sink 108. As configured, the support frame 130 is also disposed directly adjacent an outer edge 138 of the first heat sink 104. In some embodiments, the support frame 130 may also be coupled to the first heat sink 104 using one or more fasteners (not shown).

[0024] In exemplary embodiments, the second heat sink 108 is generally larger than the first heat sink 104. For example, as shown in FIG. 1, the second heat sink 108 has a width 'W2' that is greater than a width 'W of the first heat sink 104. Providing a larger surface area for the second heat sink 108 increases heat transfer/dissipation, while the smaller first heat sink 104 minimizes heat sink density at the PC board level. Furthermore, providing the apparatus 100 as a split heat sink allows for a more modular design by which the semiconductor device 120, the first heat sink 104, and/or the membrane 110 can be removed and replaced more efficiently.

[0025] Turning now to FIG. 2, an exploded side cross-sectional view of a heat sink assembly 200 (hereinafter "assembly 200") according to another embodiment will be described in greater detail. Similar to the apparatus 100 shown in FIG. 1, the assembly 200 includes a first heat sink 204 and a second heat sink 208, and a membrane 210 (e.g., a PCM) coupled to a first side 212 of the first heat sink 204 such that the membrane 210 is disposed between, and in direct contact with, the first heat sink 204 and the second heat sink 208.

[0026] In this embodiment, the second heat sink 208 includes a first section 244 adjacent and coupled to a second section 246. The first section 244 and the first heat sink 204 may be solid construction aluminum or copper, while the second section 246 may include a set of cooling fins 250. The cooling fins 250, which may be made from aluminum or plated copper, extend from an outer surface 251 of the first section 244 to further support heat dissipation.

[0027] Although omitted for the sake of brevity, it will be appreciated that the assembly

200 may further include a support device similar to the support frame 130 demonstrated in FIG. 1. The support frame 130 may have a shape that generally conforms to a cutout or recess 234 of the second heat sink 208.

[0028] Turning now to FIG. 3, an exploded side cross-sectional view of a heat sink assembly 300 (hereinafter "assembly 300") according to another embodiment will be described in greater detail. Similar to the apparatus 100 shown in FIG. 1, the assembly 300 includes a first heat sink 304 and a second heat sink 308, and a membrane 310 coupled to a first side 312 of the first heat sink 304 such that the membrane 310 is disposed between the first heat sink 304 and the second heat sink 308. The first heat sink 304 may be coupled to the second heat sink 308 so that the membrane 310 is contact on either side with the first and second heat sinks 304, 308.

[0029] In this embodiment, the first heat sink 304 includes a set of walls 352 defining one or more cavities 354 filled with a PCM 358, such as paraffin, glycol mixtures, formamide, salt and water mixtures, etc. The cavity 354 can be formed, for example, by milling, machining, laser ablation, etc. Other suitable techniques can also be used. The cavity 354 may be circular, rectangular, oval, or any other suitable shape in cross-section or plan. The cavity 354 is configured to contain a quantity of the PCM 358, which is preserved in a solid state during operation at a normal temperature.

[0030] As further shown, the second heat sink 308 includes a first section 344 adjacent and coupled to a second section 346. The first section 344 may include a set of walls 360 (e.g., Al or Cu) defining one or more cavities 362 filled with a quantity of a PCM 364, such as paraffin, glycol mixtures, formamide, salt and water mixtures, etc. The cavity 362 can be formed, for example, by milling, machining, laser ablation, etc. The PCM 358 within the cavity 354 and the PCM 364 within the cavity 362 is preserved in a solid state during operation at a normal temperature. The second section 346 may include a set of aluminum or copper plated cooling fins 350 extending from an outer surface 351 of the first section 344 to further support heat dissipation.

[0031] Turning now to FIG. 4, an exploded side cross-sectional view of a heat sink assembly 400 (hereinafter "assembly 400") according to another embodiment will be described in greater detail. Similar to the assembly 300 shown in FIG. 3, the assembly 400 includes a first heat sink 404 and a second heat sink 408, and a membrane 410 (e.g., a PCM) coupled to a first side 412 of the first heat sink 404 such that the membrane 410 is disposed between, and in contact with, the first heat sink 404 and the second heat sink 408.

[0032] In this embodiment, the first heat sink 404 includes a set of walls 452 defining one or more cavities 454 filled with a PCM 458, such as paraffin, glycol mixtures, formamide, salt and water mixtures, etc. The second heat sink 408 includes a first section 444 adjacent and coupled to a second section 446. The first section 444 may include a set of walls 460 (e.g., Al or Cu) defining one or more cavities 462 filled with a quantity of a PCM 464, such as paraffin, glycol mixtures, formamide, salt and water mixtures, etc. The PCM 458 within the cavity 454 and the PCM 464 within the cavity 462 is preserved in a solid state during operation at a normal temperature, and transitions to a liquid when heated. The second section 446 may include a set of aluminum or copper plated cooling fins 450 extending from an outer surface 451 of the first section 444 to further support heat dissipation.

[0033] As further shown, at least one of the first heat sink 404 and the second heat sink

408 include a conduit formed therein. For example, the first heat sink 404 includes a first conduit 470 formed through an interior of the first heat sink 404. In this embodiment, the first conduit 470 is provided through the PCM 458. In other embodiments, the first conduit 470 may be formed through a solid layer of Al or Cu, such as the first heat sink 204 shown in FIG. 2.

[0034] The second heat sink 408 may also include a second conduit 472 formed through an interior of the second heat sink 408. In this embodiment, the second conduit 472 is provided through the PCM 464. In other embodiments, the second conduit 472 may be formed through a solid layer of Al or Cu, such as the second heat sink 208 shown in FIG. 2. The first and second conduits 470, 472 may be formed by milling, machining, laser ablation or other known techniques, and may be circular, rectangular, or any other suitable cross-section shape.

[0035] In one embodiment, a fluid coolant traverses the first and second conduits 470,

472, wherein the fluid coolant is delivered to respective inlet ports 474, 476 of the first and/or second heat sinks 404, 408 via pumps 478, 480. Non-limiting examples of such fluid coolants include water, alcohol, air, nitrogen gas, etc. Other suitable coolants can also be used. A flow of coolant through the first and second conduits 470, 472 serves to carry heat away from the first and second heat sinks 404 and 408 by way of forced convection. In another embodiment, a fluid conduit can be defined in the form of an inlet header and an outlet header with a plurality of parallel fluid passageways there between.

[0036] In yet another embodiment, as shown in FIG. 5, the second heat sink 508 may include the second conduit 572 formed entirely within an interior of the second heat sink 508. In this embodiment, the second conduit 572 is provided as a cooling loop circulating throughout the PCM 564. For example, the second conduit 572 may be a set of completely sealed quasi evacuated tubes partially filled with air or other gases and arranged in a loop to create a cooling circulation flow. Other suitable arrangements for the second conduit 572 may also be envisioned.

[0037] In view of the foregoing, at least the following advantages are achieved by the embodiments disclosed herein. It is an advantage to provide a two-piece, split heat sink which includes a first heat sink coupled to a semiconductor device and a second heat sink acting as a finned convector. The first heat sink is provided with a small cross section to minimize PC board space required for mounting the heat sink, while the second heat sink is provided with a large number of spaced fins oriented generally along the direction of air flow adjacent to the PC board for improved heat dissipation by means of convection. The two heat sink components are attached by press fit employing a serrated aperture.

[0038] It is yet another advantage of the present disclosure to further enhance heat dissipation of the first and second heat sinks by adding a PCM therebetween, and optionally providing additional PCM within the first and/or second heat sink.

[0039] While certain embodiments of the disclosure have been described herein, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Claims

1. A heat sink apparatus, compri

a first heat sink coupled to a second heat sink;

a membrane coupled to a first side of the first heat sink and disposed between the first heat sink and the second heat sink, the membrane including a phase change material (PCM); and

a semiconductor device coupled to a second side of the first heat sink.

2. The heat sink apparatus of claim 1, further comprising a support frame coupled to the second heat sink.

3. The heat sink apparatus of claim 2, wherein the support frame is further coupled to the first heat sink.

4. The heat sink apparatus of claim 1, the first heat sink including a cavity filled with a

PCM.

5. The heat sink apparatus of claim 1, further comprising a first conduit formed in the first heat sink.

6. The heat sink apparatus of claim 5, the second heat sink including a cavity filled with a

PCM.

7. The heat sink apparatus of claim 5, further comprising a second conduit formed second heat sink.

8. The heat sink apparatus of claim 7, further comprising a pump coupled to at least one of: the first conduit and the second conduit.

9. The heat sink apparatus of claim 1, wherein the second heat sink includes a set of cooling fins.

10. The heat sink apparatus of claim 1, further comprising a set of fasteners coupling the first heat sink to the second heat sink.

11. A split heat sink, comprising:

a first heat sink coupled to a second heat sink;

a support frame coupled to the second heat sink and disposed adjacent the first heat sink.

12. The split heat sink of claim 11, wherein the support frame is coupled to the first heat sink.

13. The split heat sink of claim 11, wherein the support frame has a generally L-shaped cross section, and wherein the support frame is disposed within a recess of the second heat sink.

14. The split heat sink of claim 11, the first heat sink including a cavity filled with a PCM.

15. The split heat sink of claim 11, further comprising a first conduit formed through the first heat sink.

16. The split heat sink of claim 15, the second heat sink comprising a first section adjacent a second section, the first section including a cavity containing a PCM.

17. The split heat sink of claim 16, further comprising a second conduit formed through the first section of the second heat sink.

18. The split heat sink of claim 16, the second section of the second heat sink comprising a set of cooling fins.

19. The split heat sink of claim 11, wherein the first heat sink further comprises a second side opposite the first side, and wherein a semiconductor device is coupled to the second side of the first heat sink.

20. A split heat sink apparatus, comprising:

a first heat sink coupled to a second heat sink, the second heat sink defining a first section and a second section, the second section comprising at least one cooling fin;

a phase change material (PCM) coupled to first side of the first heat sink, the PCM disposed between the first heat sink and the second heat sink;

a semiconductor device coupled to a second side of the first heat sink; and a support frame coupled to the second heat sink, the support frame disposed directly adjacent an outer edge of the first heat sink.