Heatsink Assembly

Abstract

The disclosed heat sink assembly includes a heat sink having a plurality of ribs integrally molded along its longitudinal interior and first and second surfaces open at both longitudinal ends, and a first end plug and a second end plug that close the first and second surfaces at both ends of the heat sink, respectively. The heat sink has a cooling flow path in which a refrigerant flowing in from the first end plug side flows along an inlet flow path, changes direction from the second end plug side along a return flow path to be introduced into an outlet flow path, and then flows toward the first end plug side. The second end plug has a flow guide on the return flow path that changes from the inlet flow path to the outlet flow path.

Description

[Technical Field]

[0001] The present invention relates to a heat sink assembly that forms the bottom surface of a battery pack that includes a plurality of secondary batteries or that is attached to the bottom surface to promote heat dissipation from the battery pack.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0120563, filed on September 11, 2023, and all contents disclosed in the documents of said Korean patent application are incorporated herein by reference. [Background technology]

[0003] Unlike primary batteries, secondary batteries are rechargeable and have the potential to be small and have large capacities, which has led to extensive research and development in recent years. Demand for secondary batteries as an energy source is rapidly increasing due to the increasing technological development and demand for mobile devices, as well as the emergence of electric vehicles and energy storage systems in response to modern demands for environmental protection.

[0004] Secondary batteries are classified into coin-type batteries, cylindrical batteries, prismatic batteries, and pouch-type batteries depending on the shape of the battery case. The electrode assembly installed inside the battery case of a secondary battery is a power generating element that can be charged and discharged and has a laminated structure of electrodes and a separator.

[0005] Since secondary batteries are required to be used continuously for a long period of time, it is necessary to effectively control the heat generated during the charging and discharging process.If secondary batteries are not cooled smoothly, a positive feedback chain reaction will occur in which a rise in temperature causes an increase in current, and the increase in current causes another rise in temperature, ultimately leading to a catastrophic state of thermal runaway.

[0006] To effectively release the heat generated by secondary batteries, heat sinks (also called cooling plates) through which a refrigerant flows are widely used. The heat sink is attached to the bottom of a group of multiple secondary batteries, for example, a battery pack containing multiple secondary batteries, and performs a cooling function by absorbing the heat generated inside the pack with a refrigerant and releasing it to the outside.

[0007] Heat sinks can be divided into brazed and extruded heat sinks depending on their structure or manufacturing method. Brazed heat sinks are made by brazing two plates together to form flow channels, which allows for greater freedom in flow channel design, but has the disadvantage of reduced structural rigidity due to the deterioration of the material's physical properties. In contrast, extruded heat sinks, which are manufactured as a continuous body through extrusion molding, have the advantage of structural rigidity, but can only implement linear flow channels, resulting in many ports and the need for connecting pipes that take up space. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to provide a heat sink assembly that does not require a separate pipe for forming a flow path, occupies less space, and has a simplified flow path configuration that reduces the number of parts, thereby improving differential pressure.

[0009] Another object of the present invention is to provide a heat sink assembly that can absorb heat uniformly over its entire area by uniformly directing the flow rate of the coolant flowing through a plurality of flow paths.

[0010] However, the technical problems that the present invention aims to solve are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the description of the invention described below. [Means for solving the problem]

[0011] The present invention relates to a heat sink assembly, and in one example, it includes a heat sink having a plurality of ribs integrally molded along its interior longitudinal direction and first and second faces open at both longitudinal ends, and a first end plug and a second end plug that close the first and second faces at both ends of the heat sink, respectively. The heat sink has a cooling flow path in which a refrigerant flowing in from the first end plug side flows along an inlet flow path, changes direction from the second end plug side along a return flow path to be introduced into an outlet flow path, and then flows toward the first end plug side. The second end plug has a flow guide on the return flow path that changes from the inlet flow path to the outlet flow path.

[0012] The first end plug may have an inlet port through which the refrigerant flows and an outlet port through which the refrigerant flows.

[0013] The inlet passage connected to the inlet port may be disposed in a central region of the heat sink, and the outlet ports may be provided in pairs, with outlet passages connected to the pair of outlet ports respectively disposed on both sides of the inlet passage.

[0014] The first end plug may include an inlet plug that closes the first surface of the inlet passage, and a pair of outlet plugs that close the first surface of the outlet passage.

[0015] The flow guide may be in the form of a protrusion protruding from the surface of the second end plug.

[0016] The flow guide may be disposed to face a first outlet passage closest to the inlet passage among the passages that are diverted from the inlet passage to the return passage.

[0017] The flow guide may include an inclined surface that guides the refrigerant, which changes direction from the inlet flow path to the return flow path, toward the first outlet flow path.

[0018] In an embodiment of the present invention, the inclined surface of the flow guide may be disposed between a starting point and a center point along a width direction of the first outlet flow path.

[0019] For example, the apex of the inclined surface of the flow guide may be located at the center point in the width direction of the first outlet flow path.

[0020] The second end plug may further include a plurality of outlet flow paths that are gradually spaced apart from the first outlet flow path and the inlet flow path, and the space between the surface of the second end plug and the inlet of each outlet flow path may become wider from the first outlet flow path to outer outlet flow paths that are more distant from the inlet flow path.

[0021] For this reason, the distance between the end of the rib forming each of the outlet passages and the surface of the second end plug can increase linearly from the first outlet passage to the outer outlet passage that is further away from the inlet passage. [Effects of the Invention]

[0022] The heat sink assembly of the present invention having the above-described configuration can easily form a cooling flow path divided into an inlet and an outlet by machining both longitudinal ends of the flow path formed integrally with the heat sink and closing the open surface with an end plug.

[0023] Furthermore, the heat sink assembly of the present invention can ensure excellent structural rigidity by manufacturing the heat sink as a continuous body by extrusion molding.

[0024] In addition, the heat sink assembly of the present invention includes a flow guide in the return flow path where the coolant flow is suddenly redirected, thereby making the flow rate of the coolant introduced into each of the outlet flow paths more uniform. This allows uniform cooling performance to be maintained across the entire area of ​​the heat sink assembly, significantly reducing the possibility of secondary batteries located in areas where cooling is weak in certain areas experiencing problems such as performance degradation or thermal runaway.

[0025] However, the technical effects that can be obtained by the present invention are not limited to the effects described above, and other effects not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0026] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention described below, serve to further understand the technical concept of the present invention, and therefore the present invention should not be interpreted as being limited solely to the matters depicted in such drawings. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a view showing a heat sink assembly according to an embodiment of the present invention; [Figure 2] FIG. 2 is an exploded perspective view of the heat sink assembly of FIG. 1. [Figure 3] 1 is a diagram showing the structure of a heat sink in detail. [Figure 4] 2 is an enlarged view of part "A" in FIG. 1. [Figure 5] 2 is an enlarged view of part "B" in FIG. 1. [Figure 6] 2 is a diagram illustrating the overall flow of coolant in the heat sink assembly of FIG. 1; [Figure 7] 1 is a view showing a return flow path according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0028] Because the present invention can be modified in various ways and can have various embodiments, specific embodiments will be described in detail below.

[0029] However, this is not intended to limit the invention to any particular embodiment, but rather it can be understood to include all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

[0030] In the present invention, terms such as "comprise" and "have" are intended to specify the presence of features, numbers, steps, operations, components, parts or combinations thereof described in the specification, and can be understood as not precluding the presence or possibility of addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0031] Furthermore, in the present invention, when a layer, film, region, plate, or other portion is described as being "on" another portion, this includes not only the case where it is "directly on" the other portion, but also the case where there is another portion between them. Conversely, when a layer, film, region, plate, or other portion is described as being "under" the other portion, this includes not only the case where it is "directly under" the other portion, but also the case where there is another portion between them. Furthermore, in the present application, being disposed "on" can include not only the case where it is disposed at the top, but also the case where it is disposed at the bottom.

[0032] The present invention relates to a heat sink assembly, and in one example, it includes a heat sink having a plurality of ribs integrally molded along its interior longitudinal direction and first and second faces open at both longitudinal ends, and a first end plug and a second end plug that close the first and second faces at both ends of the heat sink, respectively. The heat sink has a cooling flow path in which a refrigerant flowing in from the first end plug side flows along an inlet flow path, changes direction from the second end plug side along a return flow path to be introduced into an outlet flow path, and then flows toward the first end plug side. The second end plug has a flow guide on the return flow path that changes from the inlet flow path to the outlet flow path.

[0033] The heat sink assembly of the present invention having the above-described configuration can easily form a cooling flow path divided into an inlet and an outlet by machining both longitudinal ends of the flow path formed integrally with the heat sink and closing the open surface with an end plug.

[0034] Furthermore, the heat sink assembly of the present invention can ensure excellent structural rigidity by manufacturing the heat sink as a continuous body by extrusion molding.

[0035] In addition, the heat sink assembly of the present invention includes a flow guide in the return flow path where the coolant flow is suddenly redirected, thereby making the flow rate of the coolant introduced into each of the outlet flow paths more uniform. This allows uniform cooling performance to be maintained across the entire area of ​​the heat sink assembly, significantly reducing the possibility of secondary batteries located in areas where cooling is weak in certain areas experiencing problems such as performance degradation or thermal runaway.

[0036] Hereinafter, specific embodiments of the heat sink assembly 10 of the present invention will be described in detail with reference to the accompanying drawings. For reference, the directions of front, back, up, down, left, and right used in the following description to designate relative positions are intended to aid in understanding the invention, and unless otherwise specified, are based on the directions shown in the drawings.

[0037] (First embodiment) FIG. 1 is a diagram showing a heat sink assembly 10 according to one embodiment of the present invention, FIG. 2 is an exploded perspective view of the heat sink assembly 10 of FIG. 1, and FIG. 3 is a diagram showing in detail the structure of the heat sink 100, particularly the structure of the internal flow path 140.

[0038] The heat sink assembly 10 of the present invention includes a heat sink 100 having a pair of opposing open surfaces, a first end plug, and a second end plug 200. The open surfaces of the heat sink 100 are surfaces located at both ends in the longitudinal direction L, and for ease of explanation, the two open surfaces will be referred to as a first surface 120 and a second surface 130, respectively. Here, the longitudinal direction L refers to the direction in which the plurality of flow channels 140, which are hollow portions, extend, and the width direction W refers to the direction perpendicular to the longitudinal direction L on a plane in which the plurality of flow channels 140 are spaced apart.

[0039] The plurality of flow channels 140 through which the refrigerant flows are hollow portions formed along the longitudinal direction L, and the flow channels 140 are separated by ribs 110. A first surface 120 and a second surface 130 at both ends of the heat sink 100 in the longitudinal direction L are open. The heat sink 100 may be manufactured as an extrusion molded product in which the plurality of flow channels 140 are integrally formed along the longitudinal direction L inside the heat sink 100 by extrusion molding. For example, FIGS. 1 and 2 show one embodiment of the heat sink 100 manufactured by extrusion molding.

[0040] The first end plug and second end plug 200 close the first surface 120 and second surface 130, respectively, that are open at both ends of the heat sink 100, and also function to organically connect the multiple separated flow paths 140 inside the heat sink 100 to form paths for the inflow and outflow of the refrigerant. The paths for the inflow and outflow of the refrigerant formed by the first end plug and second end plug 200 will be described in detail with reference to FIGS. 3 to 7.

[0041] Here, the illustrated embodiment presents as an example a heat sink 100 having a structure in which both ends in the longitudinal direction L are open due to the characteristics of extrusion-molded products. However, even in the case of a heat sink 100 that is not manufactured by extrusion molding, if the heat sink 100 has a structure in which both ends in the longitudinal direction L, through which multiple flow paths 140 extend, form open surfaces, it may be possible to construct the heat sink assembly 10 of the present invention using the same method of joining the first end plug and the second end plug 200.

[0042] 3 shows the structure of the flow channels 140 inside the heat sink 100 in more detail. The multiple flow channels 140 extend in the longitudinal direction L between the first surface 120 and the second surface 130, and both ends of each channel are spaced a predetermined distance from the first surface 120 and the second surface 130. The distance at which the flow channels 140 are spaced from the first surface 120 and the second surface 130 can be freely designed by a cutting process that mechanically removes the ribs 110 that separate the hollow portions of the flow channels 140. The cutting process that removes a portion of the end of the ribs 110 ensures a space (depth) for inserting the end plug 200.

[0043] The first end plug and the second end plug 200 close the open first surface 120 and second surface 130 of the heat sink 100, respectively. The end plugs 200 have a thickness and width suitable for insertion onto the first surface 120 and second surface 130 of the heat sink 100. The end plugs 200 inserted into the heat sink 100 can be hermetically joined by welding, for example, friction stir welding. For example, if the weld depths of the friction stir welding performed separately on the top and bottom surfaces of the heat sink 100 overlap, weld surfaces are formed on all four sides of the end plugs 200, and the end plugs 200 completely seal the heat sink 100.

[0044] Because the plurality of flow paths 140 extend in the longitudinal direction L and the first surface 120 and the second surface 130 are sealed by the first end plug and the second end plug 200, the coolant can be configured to flow throughout the entire heat transfer area of ​​the heat sink assembly 10 by appropriately selecting the positions of the ports through which the coolant flows in and out. In the illustrated embodiment, an inlet port 213 through which the coolant flows in and an outlet port 215 through which the coolant flows out are both located on the first surface 120, and the second end plug 220 is located on the second surface 130 to form a coolant return flow path 146 without a separate port.

[0045] 4 is an enlarged view of portion "A" of FIG. 1, and when viewed in conjunction with FIG. 3, the inlet flow passage 142 connected to the inlet port 213 is disposed in the central region of the heat sink 100, and the outlet flow passages 144 connected to a pair of outlet ports 215 are disposed on both sides of the inlet flow passage 142. In the illustrated embodiment, two inlet flow passages 142 are provided, and the ends of the inlet flow passages 142 are connected to return flow passages 146 that extend long along the second surface 130, and the extended return flow passages 146 are connected to the outlet flow passages 144 on both sides.

[0046] In one embodiment of the present invention, the first end plug 210 that closes the first surface 120 includes an inlet plug 211 that closes the first surface 120 of the inlet flow passage 142, and a pair of outlet plugs 212 that close the first surface 120 of the outlet flow passage 144. A certain space is formed between the inlet plug 211 and the inlet of the inlet flow passage 142, and an inlet port 213 is disposed in this space. As a result, the refrigerant flowing into the inlet port 213 fills the space upstream of the inlet flow passage 142, and then branches off into each inlet flow passage 142 and flows uniformly. Similarly, an outlet port 215 is disposed in the space formed between the outlet plug 212 and the outlet of the outlet flow passage 144.

[0047] 5 is an enlarged view of portion "B" of FIG. 1, illustrating return flow passage 146. Second surface 130 of heat sink 100 is closed by second end plug 220, and the ends of each flow passage 142, 144, i.e., the outlet of inlet flow passage 142 and the inlet of outlet flow passage 144 facing second surface 130, are also spaced a predetermined distance from second end plug 220, such that the space formed along second end plug 220 forms return flow passage 146. In the exemplary embodiment of FIG. 5, return flow passage 146 is shown with a constant distance from second surface 130, i.e., with no substantial change in cross-sectional area.

[0048] 5, the second end plug 220 includes a flow guide 230 on the return flow path 146 that is converted from the inlet flow path 142 to the outlet flow path 144. In the illustrated embodiment, the flow guide 230 is in the form of a protrusion that protrudes from the surface of the second end plug 220. The role of this flow guide 230 is to ensure a sufficient flow rate of refrigerant introduced into the outlet flow path 144 closest to the inlet flow path 142, i.e., the first outlet flow path 144-1.

[0049] The refrigerant exiting the outlet of the inlet flow path 142 collides with the second end plug 220 and then abruptly changes direction to the return flow paths 146 on either side. The refrigerant diverted to the return flow paths 146 flows sequentially into the inlets of each of the successive outlet flow paths 144, starting with the first outlet flow path 144-1. Ideally, the flow rate of the refrigerant introduced into each outlet flow path 144 would be uniform, but in reality, this is not the case.

[0050] Particularly problematic is the significant decrease in the flow rate of refrigerant introduced into the first outlet flow path 144-1, which is closest to the inlet flow path 142. The refrigerant flow around the first outlet flow path 144-1 is most unstable because it occurs immediately after the refrigerant flow is redirected by nearly 90° upon hitting the second end plug 220. This unstable flow pattern tends to result in an insufficient amount of refrigerant being introduced into the first outlet flow path 144-1. In more severe cases, the pressure drop caused by the highly turbulent flow may cause a backflow of refrigerant in the first outlet flow path 144-1.

[0051] The flow guide 230 provided in the second end plug 220 solves the flow distribution problem, and in particular serves to promote the flow of refrigerant toward the first outlet flow path 144-1, which has the most insufficient and unstable flow rate. To this end, the flow guide 230 is disposed opposite the first outlet flow path 144-1, which is closest to the inlet flow path 142, among the paths that are diverted from the inlet flow path 142 to the return flow path 146. Due to the flow guide 230 disposed opposite the inlet of the first outlet flow path 144-1, a portion of the refrigerant diverted toward the return flow path 146 hits the flow guide 230 and is then forced to flow toward the first outlet flow path 144-1.

[0052] To effectively redirect the refrigerant, the flow guide 230 may include an inclined surface 232 that guides the refrigerant redirecting from the inlet flow path 142 to the return flow path 146 toward the first outlet flow path 144-1. The inclined surface 232 of the flow guide 230 may be disposed between the starting point and the center point along the width direction W of the first outlet flow path 144-1 so that the refrigerant redirecting toward the first outlet flow path 144-1 can smoothly flow into the first outlet flow path 144-1. For example, as shown in the partially enlarged view of FIG. 5 , the apex 234 of the inclined surface 232 of the flow guide 230 may be located at the center point of the width direction W of the first outlet flow path 144-1. The flow of the refrigerant toward the first outlet flow path 144-1 is directed toward the inlet center of the first outlet flow path 144-1, thereby enabling effective inflow of the refrigerant.

[0053] 6 is a diagram showing the overall flow of refrigerant in the heat sink assembly 10 of FIG. 1. As described above, in the first surface 120 of the heat sink 100, the inlet passage 142 connected to the inlet port 213 is located in the central region of the heat sink 100, and the outlet passages 144 connected to a pair of outlet ports 215 are located on both sides of the inlet passage 142. In addition, on the second surface 130 of the heat sink 100, the second end plug 220 forms the return passage 146.

[0054] Due to this arrangement of flow paths 140, refrigerant flowing into inlet port 213 on the first end plug 210 side flows along central inlet flow path 142 and changes direction along return flow path 146 on the second end plug 220 side. The refrigerant whose direction is changed flows along return flow path 146 and is sequentially introduced into outlet flow path 144, and the refrigerant flowing along outlet flow path 144 passes through outlet port 215 on the first end plug 210 side to exit.

[0055] When the refrigerant flowing through the return passage 146 is introduced into each outlet passage 144, the flow guide 230 provided on the second end plug 220 ensures a good flow rate in the first outlet passage 144-1, which has the smallest refrigerant inflow. With the help of this flow guide 230, the flow rate of the refrigerant flowing through each outlet passage 144 becomes more uniform than before, and the refrigerant flows at a uniform flow rate across the entire area of ​​the heat sink 100, resulting in uniform cooling characteristics without bias in any particular area.

[0056] (Second embodiment) In the first embodiment, the present invention was described focusing on the configuration of the second end plug 220 for ensuring the flow rate for the first outlet flow path 144-1, which may cause a backflow of refrigerant in the return flow path 146. In the second embodiment, an additional configuration will be described that can more uniformly guide the flow rate of refrigerant introduced into each outlet flow path 144.

[0057] The refrigerant flowing through the return flow path 146 is distributed sequentially, starting with the first outlet flow path 144-1, into the multiple consecutive outlet flow paths 144. Because the flow rate of the refrigerant flowing out from the outlet of the inlet flow path 142 is almost constant, the flow characteristics of the refrigerant do not allow smooth refrigerant inflow into the first outlet flow path 144-1. However, since the refrigerant is generally distributed first to the outlet flow path 144 adjacent to the inlet flow path 142, the refrigerant flow rate tends to gradually decrease toward the downstream side of the return flow path 146. The second embodiment relates to a configuration for eliminating or alleviating such uneven distribution of flow rate.

[0058] FIG. 7 is a diagram illustrating a return flow passage 146 according to a second embodiment. Referring to FIG. 7, the return flow passage 146 includes multiple outlet flow passages 144 that are gradually spaced apart from the inlet flow passage 142, and the space between the surface of the second end plug 220 and the inlet of each outlet flow passage 144 increases from the first outlet flow passage 144-1 to the outer outlet flow passage 144 that is farther away from the inlet flow passage 142. The space between the surface of the second end plug 220 and the inlet of each outlet flow passage 144 is determined by the length of the rib 110 on the second surface 130 that forms the inlet of the outlet flow passage 144. That is, the configuration of FIG. 7 can be realized by adjusting the cutting depth of the end of the rib 110 of the outlet flow passage 144 that is mechanically machined through the second surface 130.

[0059] In the illustrated embodiment, the distance between the end of the rib 110 defining each outlet flow path 144 and the surface of the second end plug 220 increases linearly from the first outlet flow path 144-1 to the outermost outlet flow path 144. The linear increase in the distance between the end of the rib 110 and the surface of the second end plug 220 linearly expands the space between the surface of the second end plug 220 and the inlet of each outlet flow path 144 with increasing distance from the inlet flow path 142.

[0060] With this configuration, when the space between the surface of the second end plug 220 and the inlet of each outlet flow path 144 is narrow, the faster the flow rate, the smaller the amount of refrigerant introduced into the outlet flow path 144; on the other hand, when the space is wide, the slower the flow rate, the longer the amount of refrigerant introduced into the outlet flow path 144.

[0061] Therefore, the flow guide 230 of the second end plug 220 ensures the flow rate to the first outlet flow path 144-1, and by realizing differential flow rate distribution taking into account the distance from the outlet of the inlet flow path 142, the flow rate distributed throughout the outlet flow path 144 becomes more uniform, thereby enabling the cooling performance of the heat sink assembly 10 to exhibit uniform cooling performance across the entire area.

[0062] The present invention has been described in more detail above with reference to the drawings and embodiments, etc. However, the configurations shown in the drawings or embodiments in this specification are merely one embodiment of the present invention and do not represent all of the technical ideas of the present invention, and therefore, at the time of filing this application, there may be various equivalents and modifications that can replace them. [Explanation of symbols]

[0063] 10: Heat sink assembly 100: Heat sink 110: Rib 120: 1st page 130:Second side 140: Flow path 142: Inlet flow path 144: Outlet flow path 144-1: First outlet channel 146: Return flow path 200: End plug 210: 1st end plug 211: Inlet plug 212: Outlet plug 213: Inlet port 215: Outlet port 220: Second end plug 230: Flow Guide 232: Inclined surface 234: Vertex L: Longitudinal direction W: Width direction

Claims

1. a heat sink having a plurality of ribs integrally formed along a longitudinal direction of the interior thereof, and a first surface and a second surface at both ends in the longitudinal direction being open; a first end plug and a second end plug that close the first surface and the second surface at both ends of the heat sink, respectively; Including, The heat sink is a cooling flow path in which the refrigerant flowing in from the first end plug side flows along an inlet flow path, changes direction from the second end plug side along a return flow path, is introduced into an outlet flow path, and then flows toward the first end plug side; The second end plug is The heat sink assembly includes a flow guide on the return flow path that is diverted from the inlet flow path to the outlet flow path.

2. The first end plug has: The heat sink assembly of claim 1 , wherein an inlet port through which the coolant flows and an outlet port through which the coolant flows are disposed.

3. the inlet passage connected to the inlet port is disposed in a central region of the heat sink; The heat sink assembly according to claim 2 , wherein the outlet ports are provided in pairs, and the outlet passages connected to the pair of outlet ports respectively are disposed on both sides of the inlet passage.

4. The first end plug is an inlet plug that closes the first surface of the inlet passage; 4. The heat sink assembly of claim 3, further comprising a pair of outlet plugs closing off said first faces of said outlet passages.

5. The flow guide is 5. The heat sink assembly of claim 1, wherein the second end plug is in the form of a protrusion extending from a surface thereof.

6. The flow guide is The heat sink assembly according to claim 5 , wherein the first outlet passage is disposed opposite the first outlet passage that is closest to the inlet passage among the paths that are diverted from the inlet passage to the return passage.

7. The flow guide is The heat sink assembly of claim 6 , further comprising an inclined surface that directs refrigerant diverted from the inlet passage to the return passage toward the first outlet passage.

8. The inclined surface of the flow guide is The heat sink assembly of claim 7 , wherein the first outlet passage is disposed between a starting point and a center point along the width of the first outlet passage.

9. The apex of the inclined surface of the flow guide is The heat sink assembly of claim 8 , wherein the first outlet passage is located at the midpoint in the width direction of the first outlet passage.

10. 7. The heat sink assembly of claim 6, including a plurality of outlet passages spaced progressively apart from the inlet passage, the space between the surface of the second end plug and the inlet of each outlet passage increasing from the first outlet passage to outer outlet passages spaced further away from the inlet passage.

11. 11. The heat sink assembly of claim 10, wherein the distance between the end of the rib forming each outlet passage and the surface of the second end plug increases linearly from the first outlet passage to an outer outlet passage that is more remote from the inlet passage.

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