Rod-like FIN shape heat sink, production method for same, and cooling device on which said heat sink is mounted

Abstract

Provided are: a heat sink that increases the degree of freedom of design regarding requirements such as shape, height, and placement density, that exhibits high cooling performance, and that has a simple structure; and a production method for the same. Provided is a heat sink (12) that employs pin fins (22) as an example of a rod-like fin shape, and that, through heat exchange, absorbs and dissipates heat which is produced by operation of an electric element (10) such as a power semiconductor. This heat sink comprises a base part (20) that has a first surface (22U) which contacts the electric element and a second surface (22L) which is on the opposite side from the first surface, and that is thermally conductive. This heat sink also comprises a plurality of aluminum or copper pin fins (22) that are provided as separate components from the base part, that each have a lengthwise direction, and that are thermally conductive. The heat sink (12) is formed such that one end (22R) of each of the plurality of pin fins in the lengthwise direction thereof is joined to and made integral with the second surface (22L). Thus, the present invention comprises a collection of pin fins (FIN) in which all of the plurality of pin fins are disposed standing close together on the second surface (22L), and which performs a heat exchange function for cooling.

Description

Rod-shaped fin heat sink, its manufacturing method, and cooling device equipped with the heat sink

[0001] The present disclosure relates to a rod-shaped fin heat sink and a manufacturing method thereof, and a cooling device equipped with the heat sink, and in particular to a rod-shaped fin heat sink equipped with rod-shaped fins that forcibly cools electrical elements that generate heat during operation, a manufacturing method thereof, and a cooling device equipped with the heat sink.

[0002] In general, electrical elements often generate heat during operation, requiring cooling. A cooling mechanism for dissipating or absorbing this heat is necessary for both the component itself and the system as a whole. In recent years, with the widespread use of systems that control large amounts of power, such as drive circuits and control circuits, particularly in fields such as electric vehicles (EVs), hybrid vehicles, aircraft, home appliances, communication devices, and industrial equipment, power semiconductors (power diodes and power transistors), which are semiconductor elements that handle high voltages and large currents to control and convert that power, have come to play an important role. These power semiconductors are often packaged and incorporated into circuits such as inverters, converters, AC / AC converters, and DC / DC converters.

[0003] Semiconductor packages play such an important role in that they use a heat sink, either natural or forced, to cool the semiconductor package and use it in contact with the package as a way to suppress the temperature rise caused by heat generated during operation. These heat sinks come in a variety of structures and types, and designers select the appropriate type to suit the amount of heat generated by the semiconductor package and the cooling environment when carrying out thermal design.

[0004] In this context, pin fin heat sinks have attracted attention due to their simple structure and relatively large surface area in contact with the cooling fluid, such as cooling air, cooling water, or refrigerant, resulting in high heat exchange efficiency. These pin fin heat sinks have a base plate (base substrate) with a first surface that contacts and is positioned on the semiconductor package and a second surface opposite the first surface. Furthermore, multiple pin fins are provided on the second surface of the base plate. For example, both the base plate and the multiple pins are made of an aluminum alloy primarily containing aluminum or a copper alloy primarily containing copper. Heat transferred to a package containing a heat-generating element, such as a power semiconductor, is naturally or forcibly cooled by heat exchange via the base plate and the multiple pin fins.

[0005] Many examples of pin fin heat sinks are known, including the one described in Patent Document 1 [WO 2012 / 114955]. This document describes two linear fin rows, each consisting of multiple pin fins, arranged facing each other to form a roughly V-shape along the flow of cooling air. In this example, the pin fins are formed by die-casting using a mold and are integrated into the base plate.

[0006] However, the pin fin type heat sink formed by the above-mentioned conventional manufacturing method has limitations in terms of improving cooling performance and reducing manufacturing costs.

[0007] This will be explained separately in terms of cooling performance and manufacturing costs.

[0008] <Issues in terms of cooling performance> - It would be desirable to increase the pin height to improve performance, but from the perspective of die removal and die life, it is technically and practically difficult to increase the pin height.

[0009] ・We want to increase the density of pins relative to the plate area by increasing the number of pins as much as possible, but this reduces the mold thickness between the pins, which is limiting in terms of mold life.

[0010] <<Challenges in manufacturing costs>> ・Because there is a large variation in dimensions when forging or casting, in order to guarantee the shape, it is often necessary to manufacture more than specified in the client's drawings. For example, the pin height is manufactured higher than specified in the drawings and then removed by cutting to fit within the drawing tolerances. However, because aluminum pins are soft, they must be machined under advanced cutting conditions to prevent deformation. In addition, a process for removing burrs generated during cutting and a process for removing cutting chips (cleaning) are required, which increases the additional processing costs, material costs, and creates environmental problems.

[0011] - As the cooling performance of the heat sink improves, it becomes necessary to make the pin shape more complex, reduce the gap between pins, and minimize the pin draft angle, which increases the cost of mold production, shortens the mold life, and increases the cost of mold maintenance.

[0012] WO 2012 / 114955

[0013] For these reasons, as mentioned above, the current demands for high cooling performance and further reduction in manufacturing costs have not yet been fully met.

[0014] Therefore, it is desirable to provide a pin fin heat sink structure and a manufacturing method thereof that can increase design freedom regarding requirements such as the shape, height, and placement density of each pin fin, thereby enabling high cooling performance, and that can reduce manufacturing costs by using a simple structure consisting of only a base portion and multiple pin fins joined to the base portion.

[0015] According to one aspect of the present disclosure, there is provided a rod-shaped heat sink that absorbs and dissipates heat generated by an electric element through heat exchange during operation. The rod-shaped heat sink is characterized by comprising: a thermally conductive base portion having a first surface that contacts the electric element and a second surface opposite the first surface; and a pin assembly that is provided as a separate part from the base portion, and that includes a plurality of rod-shaped fins, each of which has a longitudinal direction and is thermally conductive, wherein one end of each of the rod-shaped fins in the longitudinal direction is integrally joined to the second surface, and the plurality of rod-shaped fins as a whole are arranged in a forest on the second surface.

[0016] The rod-shaped fin referred to here means a fin having an "elongated, straight, or almost straight shape," such as a pin fin. Therefore, the shape of the rod-shaped fin includes a round-bar fin having a circular cross section, a prismatic fin having a polygonal cross section, and even an elliptical fin having an elliptical cross section. Therefore, even if a fin has a plate-like cross section, known as a plate fin (see, for example, JP 2005-57033 A and JP 2017-54895 A), it is considered to be a rod-shaped fin if the ratio of its major axis to its minor axis (aspect ratio) is about 5:1.

[0017] Such rod-fin heat sinks are mounted in cooling devices for cooling electrical components.

[0018] On the other hand, according to another aspect of the present disclosure, there is provided a method for manufacturing a rod fin heat sink, the method comprising: a first step of setting a pin alignment jig on the base portion so as to face the second surface, the pin alignment jig having a plurality of through holes formed therein that correspond to the diameters and standing positions of the pins, the pin alignment jig facing the second surface, and inserting the rod fins into the through holes so that one end of each of the rod fins protrudes from the through holes; a second step of setting a pressure jig that applies pressure between the first surface of the base portion and one end of each of the pins protruding from the through holes of the pin alignment jig; and a third step of joining the other end of each of the rod fins to the second surface of the base portion while applying pressure with the pressure jig or a pressure device.

[0019] The rod-shaped fin heat sink according to one aspect of the present disclosure has a basic feature in that it has a simple structure in which the rod-shaped fins and the base are prepared as separate components and joined together by, for example, metal bonding. In addition, since the rod-shaped fins do not require components such as flanges that are conventionally found on the rod-shaped fins, the structure is simplified, which is advantageous in terms of manufacturing costs.

[0020] Furthermore, because the rod-shaped fins and the base can be treated as separate components, design and manufacturing can be tailored to the required cooling performance specifications from the manufacturing stage of each component. This means there is greater design freedom for improving the cooling performance of the entire heat sink, making it easier to meet the required specifications compared to conventional structures where the rod-shaped fins and the base are manufactured integrally from the beginning, such as by casting or forging. Specifically, the shape and height of each of the multiple rod-shaped fins, as well as the fin arrangement density on the surface of the base, can be more precisely adjusted according to the design specifications. This allows for more precise control of cooling performance.

[0021] On the other hand, according to the manufacturing method of the rod-shaped fin heat sink disclosed herein, a pin alignment jig having a plurality of through holes formed therein corresponding to the diameters and vertical positions of the rod-shaped fins is set on the base plate so as to face the second surface of the base portion, and the rod-shaped fins are inserted into the through holes so that one end of each pin protrudes from the holes (first step). Then, a pressure jig is set so as to apply pressure between the first surface of the base portion and one end of each of the rod-shaped fins protruding from the through holes of the pin alignment jig (second step). Then, while applying pressure, the other end of each of the rod-shaped fins is bonded to the second surface of the base portion using a bonding method such as diffusion bonding (third step). In this way, the first to third steps are simplified overall, including the step of aligning the rod-shaped fins among the separately prepared rod-shaped fins and base portion using the pin alignment jig, thereby reducing manufacturing costs.

[0022] In the accompanying drawings:

[0023] FIG. 1 is a perspective view illustrating an overview of a cooling device equipped with a rod-fin heat sink according to the present disclosure;

[0024] FIG. 2 is a cross-sectional view illustrating the structure of a rod-fin heat sink according to a first embodiment, which is equipped with a package of electric elements that generate heat during operation;

[0025] FIG. 3 is a side view illustrating a heat sink body;

[0026] FIG. 4 is a process diagram illustrating an overview of a first manufacturing method of a heat sink body;

[0027] FIG. 5 is a diagram illustrating components and tools required when manufacturing the heat sink body;

[0028] FIG. 6 is a diagram illustrating a manufacturing process of the heat sink body;

[0029] FIG. 7 is a partially cutaway perspective view illustrating a pin alignment jig, a base plate, and the positions of the pin fins on the base plate during manufacturing;

[0029] FIG. 8 is a process diagram illustrating an overview of a second manufacturing method of a heat sink body;

[0030] FIG. 9 is a cross-sectional view of a rod-fin heat sink, together with a detailed diagram illustrating a corrosion-resistant plating layer according to the second manufacturing method;

[0031] FIG. 10 is a diagram illustrating a portion of the process of a manufacturing method according to a modified example of the first embodiment;

[0032] FIG. 11 is a process diagram illustrating an overview of a manufacturing method of a rod-fin heat sink body according to a second embodiment;

[0033] FIG. 12 is a diagram illustrating a manufacturing method according to a second embodiment;

[0034] FIG. 13 is a diagram illustrating a portion of the manufacturing process of a modified example of the second embodiment;

[0035] FIG. 14 is a diagram illustrating a first modified example that can be implemented in both the first and second embodiments. FIG. 1 is a side view illustrating a modified example 2 that can be implemented in both the first and second embodiments. FIG. 2 is a side view illustrating a modified example 3 that can be implemented in both the first and second embodiments. FIG. 3 is a side view illustrating a modified example 4 that can be implemented in both the first and second embodiments. FIG. 4 is a view illustrating a modified example 5 that can be implemented in both the first and second embodiments. FIG. 5 is a view illustrating a modified example 6 that can be implemented in both the first and second embodiments. FIG. 6 is a view illustrating a modified example 7 that can be implemented in both the first and second embodiments. FIG. 7 is a view illustrating a modified example 8 that can be implemented in both the first and second embodiments.

[0023] (First embodiment) Hereinafter, a rod-fin type heat sink and a manufacturing method thereof according to the present invention will be described with reference to the drawings.

[0024] The first embodiment exemplifies the structure and features of the rod-fin heat sink, and the second and third embodiments explain some examples of manufacturing methods thereof.

[0025] First Embodiment As shown in FIG. 1 , a cooling device 1 according to a first embodiment is a device for cooling power semiconductors (electrical elements) that perform functions such as switching high power and current in a power supply circuit that supplies power to a motor mounted on, for example, an EV (electric vehicle). Power semiconductors generate heat during operation. For this reason, a cooling mechanism is required to dissipate heat to the outside or remove it through heat exchange from a semiconductor package 10 that includes, for example, multiple power semiconductors (electrical elements) with inverter functionality. Of course, since electrical elements generate heat to some extent during their operation, the electrical elements targeted by the present invention are not limited to power semiconductors.

[0026] In this embodiment, as an example of the cooling mechanism, a forced cooling mechanism is adopted in which a cooling fluid such as cooling water, cooling air, or a refrigerant such as chlorofluorocarbon gas is forcibly circulated. Of course, a natural cooling mechanism in which heat is naturally dissipated outside without circulating such a fluid may also be adopted.

[0027] 1 and 2 , the cooling device 1 according to this embodiment includes a pin-fin heat sink 12 (including a heat sink body 30, described later) that functions as a rod-fin heat sink and has a power semiconductor package 10 mounted on one side thereof in contact with the pin-fin heat sink 12. The heat sink 12 includes a cover 14 that faces the heat sink 12 and defines a space SP through which a cooling fluid FL, such as a refrigerant, flows. The cover 14 includes an input port 16A and an output port 16B at opposite ends of a side surface 14A of the cover 14 in the fluid flow direction, through which the cooling fluid FL flows. A pipe 18 connects the ports 16A and 16B, and a refrigerant source 19 (refrigerant supply device) is inserted midway through the pipe 18. The cooling device 1 includes the pin-fin heat sink 12, the cover 14, the input port 16A, the output port 16B, the pipe 18, and the refrigerant source 19.

[0028] The base plate 20, which is the base portion described below, and the pin fins 22, which are rod-shaped fins, are both formed from a metal material with high thermal conductivity, such as aluminum or an aluminum alloy (hereinafter simply referred to as "aluminum or aluminum"), or copper or a copper alloy (hereinafter simply referred to as "copper"), and are prepared as separate parts.

[0029] In this embodiment, the base plate 20 and the pin fins 22 are both made of the same metal material (such as aluminum or copper). A heat sink manufacturing method in which the base plate 20 and the pin fins 22 are both made of aluminum is referred to as a first manufacturing method, while a heat sink manufacturing method in which the base plate 20 and the pin fins 22 are both made of copper is referred to as a second manufacturing method, both of which will be described later.

[0030] The base plate 20 and the pin fins 22 may be made of different materials (for example, aluminum and copper, aluminum and brass, etc.).

[0031] Of these, the heat sink 12 includes, for example, a rectangular, plate-like base plate 20 (base portion) in a plan view, and a plurality of pin fins 22 (rod-shaped fins).

[0032] The pin fins 22 are an example of rod-shaped fins, and "rod-shaped" refers to an "elongated, straight, or almost straight" shape, which is the usual concept of an "elongated, elongated shape." This concept of shape is the same regardless of the metal material of the pin fins 22.

[0033] For this reason, as will be illustrated later (see FIG. 18), the shape of a rod-shaped fin includes a round rod-shaped fin with a circular transverse cross section, a square rod-shaped fin with a polygonal transverse cross section having three or more sides, and even an elliptical fin with an elliptical transverse cross section. Furthermore, not only the cross-sectional shape but also the overall shape that can be seen as elongated in the longitudinal direction is recognized as being included in the concept of rod-like, including shapes curved in the longitudinal direction and shapes in which multiple rod-shaped portions are integrated in staggered steps. In other words, the shape of the cross section does not necessarily have to be a perfect rod, and even if the shape is somewhat irregular, it is understood to be included in the concept of "rod-like" as long as it is close to an "elongated, straight, or almost straight" shape.

[0034] The base plate 20 has a thickness t determined based on the specifications specified by the user of the heat sink 12 and the design specifications for heat exchange. Furthermore, since the base plate 20 is formed in a plate shape, it has an upper surface 20U which is a first surface and a lower surface 20L which is a second surface opposite to the upper surface 20U.

[0035] Here, for ease of explanation, the direction from the upper surface 20U to the lower surface 20L of this thickness t is called the Z-axis direction, and three orthogonal axes, the X-axis direction and the Y-axis direction, are set along the horizontal and vertical edges of the base plate 20 relative to this Z-axis direction.

[0036] The base plate 20 (base portion) does not necessarily have to be plate-shaped, and may be curved as a whole. Furthermore, the lower surface 20L may be curved or formed in a stepped shape. The key is that the base plate 20 has a surface on which the pin fins 22 are erected and a surface against which the semiconductor package 10 abuts to receive heat dissipated from the semiconductor.

[0037] In this embodiment, the multiple pin fins (rod-shaped fins) 22 are classified as "rod-shaped fins that are elongated compared to the size of their horizontal cross-sections," and have both ends in the longitudinal direction LE (a tip end 22T and a bottom end 22R in the Z-axis direction in FIG. 1). Note that "rod-shaped" refers to "an elongated, straight, or almost straight shape," and is the usual concept of "an elongated, elongated shape." The shape of the horizontal cross-section may differ, and the fin does not necessarily have to be a perfect rod shape; even if the shape is somewhat irregular, it is recognized as "rod-shaped" as long as it is close to "an elongated, straight, or almost straight shape."

[0038] The cross-sectional size in the horizontal direction (direction along the XY plane) perpendicular to the longitudinal direction LE may be constant regardless of the cross-sectional position, or conversely, may increase as the cross-sectional position approaches the tip 22T. In the latter case, that is, in the upright state, the tip 22T will have a thicker inverted triangular shape. The shape of the pin fin 22 may be a round rod shape as a whole, a prism shape with a square cross section, or a triangular prism shape with a triangular cross section. Similarly, it may be a polygonal prism shape with pentagons or more. In the case of a fin whose horizontal cross section along the XY plane is a rectangle or a polygon with pentagons or more, a ratio of the length of the rectangle to the width or the length of the major axis to the minor axis of the polygon of 1:1 to 5:1 is understood to be included in the concept of a pin fin (i.e., a rod-shaped fin).

[0039] As can be seen from Fig. 1, the lower ends 22R of the multiple pin fins 22 are respectively bonded to multiple two-dimensionally discrete array positions P (see Fig. 7) on the lower surface 20L (second surface) of the base plate 20. Various bonding methods can be used for this purpose, such as diffusion bonding and brazing, which will be described later.

[0040] As a result, each pin fin 22 is erected at a designated arrangement position P on the lower surface 20L. As a whole, the plurality of pin fins 22 are provided as an assembly FIN of pin fins standing in a forest on the lower surface 20L as described above. This forest of pin fins 22 can also be understood from the schematic diagrams of Figures 1 and 2.

[0041] In this embodiment, the multiple pin fins 22 are all round bar-shaped pin fins with a uniform cross-sectional size from the bottom end 22R to the tip end 22T, with cross-sectional sizes taking into account thermal resistance based on thermal conductivity and flow path resistance to the flow of the cooling fluid FL. They are prepared as separate components from the base plate 20. For example, they are formed by cutting an aluminum wire rod with a diameter (e.g., 1.8 mm) that matches the design specifications to a length (e.g., 30 mm) determined by the design specifications (e.g., heat exchange capacity).

[0042] The pin fin assembly FIN may be an assembly of multiple types of pin fins 22 with different pin heights, cross-sectional sizes, cross-sectional shapes, etc. Under the same supply conditions of the cooling fluid FL, the larger the area of ​​the pin fins 22 in contact with the fluid FL, the larger the surface area of ​​the pin fins 22, resulting in a higher heat exchange rate, i.e., cooling performance. On the other hand, using pin fins with a large surface area increases flow resistance, slowing the speed of the fluid FL flowing through the space SP inside the heat sink 12 and reducing cooling performance. Therefore, to balance these two factors, it is effective to appropriately select the height, cross-sectional size, cross-sectional shape, etc. of the pin fins 22 according to the pin arrangement position P (i.e., whether the position belongs to the area on the second surface 20L facing the semiconductor package 10) to ensure high cooling performance.

[0043] In the heat sink 12 having the above configuration, heat transferred from the semiconductor package 10 is transferred via the base plate 20 to the multiple pin fins 22. The refrigerant discharged from the refrigerant source 20 passes through part of the pipe 18 and enters the internal space SP of the heat sink 12 from the input port 16A. Because the internal space SP is filled with the above-mentioned pin fins 22, heat exchange occurs between the pin fins 22 and the refrigerant in contact with their surfaces. As a result, the heat transferred to the pin fins 22 is forcibly exchanged with the refrigerant. The refrigerant that absorbs heat through this heat exchange is returned to the refrigerant source 20 from the output port 16B via the pipe 18. This refrigerant cycle is repeated, cooling the semiconductor package 10 by the heat sink 12.

[0044] <First and Second Manufacturing Methods of Heatsink> 1) First Manufacturing Method This first manufacturing method is applied when both the base plate 20 and the pin fins 22 are formed of aluminum (including aluminum alloy), as described above. FIG. 3 shows the pin fins 22, their assembly FIN, and the base plate 20 that supports them, as a schematic diagram of the heatsink body 30. The manufacturing method of this heatsink body 30 will be described with reference to FIGS. 4 to 8. The lower ends 22R of each of the multiple pin fins 22 are joined to the lower surface L (second surface) of the base plate 20 at arrangement positions P (see FIG. 7) spaced a predetermined distance from each other by the manufacturing method shown in FIG. 4, thereby forming the assembly FIN of the pin fins 22 as a whole.

[0045] 5(A) to 5(D), a plurality of aluminum pin fins 22, an aluminum base plate 20 which is a separate part from the pin fins 22, a pin alignment jig 40 made of a metal material (e.g., SUS) or a carbon material, and a pair of similar plate-shaped metal clamping jigs 50 are prepared (FIG. 4, step S1).

[0046] Of these, the pin alignment jig 40 has a rectangular plate-like portion 40A having the same area as the second surface 20L of the base plate 20 described above, and a plurality of pin insertion holes 40B drilled in the portion at positions that correspond to the two-dimensional pin arrangement position P (see FIG. 7) required by the design specifications. The pin alignment jig 40 also has wall portions 40C extending integrally from two (or four) opposing edges of the plate-like portion 40A. As will be described later, the size of the wall portions 40C is set so that when the jig is placed over the base plate 20, it abuts against and fits into two opposing side surfaces of the base plate 20.

[0047] 6A and 7, the pin alignment jig 40 can be positioned relative to the base plate 20 simply by placing the pin alignment jig 40 over the base plate 20 and abutting and fitting the wall portion 40C against the side surface of the base plate 20. In other words, the multiple pin insertion holes 40B of the pin alignment jig 40 correspond to directly below in the Z-axis direction, and the position of the second surface 20U of the base plate 20 corresponds to the arrangement position P of the pin fins 22 (see FIG. 7).

[0048] The assembled heat sink body 30 is then pressed from above and below in the Z-axis direction. The clamping jig 50 (or a pressure device (not shown)) used as the pressure jig is a pair of pressure plates 50L, 50U attached to an actuator (not shown). That is, the pressure plates 50L, 50U clamp and press the tip ends 22T of the pin fins 22 of the heat sink body 30, the lower end surface 4C of the wall portion 4C of the pin alignment jig 40, and the upper surface 20U of the base plate 20.

[0049] After the preparation in step S1 is completed, the pin alignment jig 40 is placed over the base plate 20 as shown in Fig. 6(A), and the pin fins 22 are inserted into the pin insertion holes 40B as shown by the dashed lines in Fig. 6(B) to set them on the pin alignment jig 40 (Fig. 4, step S2). Next, the pin alignment jig 40 is set on the base plate 20 as shown by the solid lines in Fig. 6(B) (Fig. 4, step S3). This positions the pin fins 22 with respect to the pin arrangement position P (see Fig. 7) on the surface ("lower surface 20L") of the base plate 20, and the height of the pin alignment jig 40 is adjusted so that the top of each pin fin 22 protrudes upward (in the length direction of the pin fin) beyond the surface of the pin alignment jig 40.

[0050] As a result, each of the pin fins 22 is supported by the pin alignment jig 40 and stands at the pin arrangement position P on the lower surface 20L of the base plate 20.

[0051] After the pin fin alignment and jig setting are complete, in step S4, as described above, the pin alignment jig 40 with the aligned pin fins 22 and the base plate 20 are sandwiched between a pair of clamping jigs 50 (50L, 50R) from above and below to prepare for pressure application (see FIG. 6C). This pressure setting allows the heads of each pin fin 22 and the undersides of both sides of the jig 40, i.e., the surface (underside 20L) of the base plate 20, to be sandwiched between the pair of clamping jigs 50 (50L, 50R) so that pressure can be applied from above and below. This pressure setting is performed, for example, in a vacuum chamber VR (see FIG. 6D). Once preparations for pressure application are complete, in step S5, the heat sink body 30 housed in the chamber VR is pressurized in a predetermined vacuum atmosphere while being heated at a temperature that induces diffusion, thereby performing metal bonding (see FIG. 6D). The heat source for heating may be placed inside or outside the chamber VR. This metal joining includes brazing as well as diffusion joining (thermal diffusion joining, microwave joining).

[0052] Therefore, heating causes atomic diffusion of the metals (aluminum or aluminum alloy in this embodiment) at the interface between each pin fin 22 and the surface (lower surface 20L) of the base plate 20, where the pin fins 22 and the base plate 20 are in contact with each other. The pin fins 22 are bonded (thermocompression bonded) to each other at the pin arrangement position P, forming an integrated unit (see the enlarged cross section of the bonded portion UN in FIG. 3 ). Note that if the pin fins 22 and the base plate 20 are made of different materials (e.g., aluminum or aluminum alloy and copper or copper alloy), the bonded portion UN will be layered, and some voids BD may occur within the layer. In this embodiment, the pin fins 22 and the base plate 20 are made of the same material (aluminum or aluminum alloy), reducing the number of voids and achieving a more reliable bond at the atomic level.

[0053] 1, a forest of pin fin assemblies FIN stands up from the underside 20L of the base plate 20, and the two elements of the pin fins and the base plate are integrated to form a heat sink body 30. The pin fin assemblies FIN protrude into the internal space SP through which the refrigerant passes.

[0054] An example of the bonding conditions for the thermal diffusion bonding in step S5 is a pressure of 0.05 to 40 MPa and a vacuum of 10 -4 ~10 -5 Torr, heating temperature = 260 to 620°C, heating time = 60 to 400 min. Of course, other bonding conditions may be set.

[0055] Once the thermal bonding is completed as described above, in step S6, the clamping jig 50 and the pin alignment jig 40 are removed, and the integrated heat sink body 30 is taken out of the chamber VR, and after an inspection process not shown, the cooling device 1 is assembled.

[0056] 2) Second Manufacturing Method This second manufacturing method is applied when both the base plate 20 and the pin fins 22 are made of a copper material (including a copper alloy), as described above.

[0057] The flow of the second manufacturing method is explained with reference to Fig. 8. In this flow, the material prepared in step S1' is different from that in Fig. 4, and step S7 is further added.

[0058] In the first step S1', a plurality of pin fins 22 made of copper (including copper alloys), a base plate 20 made of copper (including copper alloys) which is a separate part from the pin fins 22, a pin alignment jig 40 made of a metal material (e.g., SUS) or a carbon material, and a similar plate-shaped clamping jig 50 made of a metal are prepared (Figure 8, step S1').

[0059] Next, the steps S2 to S6 in FIG. 4 are carried out in the same manner as described above (FIG. 8, steps S2 to S6). However, in step S5, bonding conditions are set to match the thermal diffusion bonding of copper materials. The bonding method is thermal diffusion bonding in which pressure is applied in a vacuum atmosphere or a reducing atmosphere, or microwaves are applied. An example of the bonding conditions for this thermal diffusion bonding is a pressure of 0.01 to 40 MPa, a vacuum degree of 10, etc., taking into account the melting point of copper, etc. -4 ~10 -5 Torr, heating temperature = 650 to 1050°C, heating time = 1 to 400 min. Of course, other bonding conditions may be set.

[0060] Alternatively, the thermal diffusion bonding may be performed by ultrasonic bonding, which can be performed in an indoor environment.

[0061] When this thermal diffusion bonding is complete, the copper heat sink body 30 is formed with the pin fins 22 standing tall on the base plate 20. Then, the clamping jig 50 and the pin alignment jig 40 are removed, and the heat sink body 30 is taken out (step S6).

[0062] Thereafter, to prevent corrosion, the heat sink body 30 is subjected to a corrosion-resistant surface treatment (nickel plating, for example) using a known method such as electroplating or electroless plating, and a plating film TL having a thickness of, for example, several μm to several tens of μm is formed on the surface of the material, i.e., the heat sink body 30, as shown in Fig. 9. Specifically, the plating film TL is formed to cover the entire lower surface 20L and side surfaces of the base plate 20 and the entire surface of each pin fin 22. The peripheral edges of the upper surface 20U of the base plate 20 may also be plated continuously from the side surfaces.

[0063] The heat sink body 30 is further covered with an aluminum cover 14 to produce the heat sink 12. Therefore, as shown in Figure 9, the portion A where the copper base plate 20 (or its underside 20L) and the end of the cover 14 abut is resistant to corrosion caused by the difference in natural electrode potential E at the contact surface between dissimilar metals and corrosion caused by copper ions dissolved in the refrigerant or cooling water, thereby extending the life of the heat sink 12. In addition, because the base plate 20 and pin fins 22 are made of copper, they have a higher thermal conductivity than aluminum ones, allowing for better cooling performance.

[0064] <Effects> As described above, the heat sink body 30 according to this embodiment is formed by, for example, diffusion bonding (thermocompression bonding) or brazing a plurality of pin fins 22 prepared in advance to the base plate 20. This makes it easier to form a simple integrated structure consisting of the pin fins 22 and the base plate 20. Therefore, design specifications required to exhibit sufficient cooling performance, such as the shape and height of the pin fins 22 and their arrangement density on the base plate 20, can be achieved more easily and at lower cost than with conventional processing methods such as die casting.

[0065] More specifically, unlike conventional integrated manufacturing methods that make use of casting methods, for example, the rod-shaped fins can be prepared separately from the base portion (or base plate), eliminating the need to provide the rod-shaped fins with a draft angle, as was previously required. For this reason, the use of straight rod-shaped fins without a draft angle or rod-shaped fins with a thin base portion (reverse gradient) enables a denser layout, contributing to improved cooling performance.

[0066] Furthermore, because the rod-shaped fins can be prepared before the integral joining, the height of all or some of the multiple fins can be increased. On the other hand, when multiple rod-shaped fins are arranged upright on the surface of the base portion, it is also easy to design a high-density fin arrangement by narrowing the spacing between the rod-shaped fins over the entire surface or over part of the surface. By adjusting the height of the rod-shaped fins and arranging the fins over the entire surface or locally over a high density, the efficiency of heat exchange between heat generated from the electric element and a cooling fluid or the like via the base portion and the rod-shaped fins can be further improved, thereby improving cooling performance.

[0067] Furthermore, since the pin fins and base portion are prepared separately, the pin fins can be prepared by cutting wire rods of a predetermined diameter, eliminating the need for molds or machining processes. The pin fins are attached to the base portion by diffusion bonding or brazing. This simplified configuration is also advantageous in terms of manufacturing costs.

[0068] Furthermore, since the pin fins and base portion are prepared separately, there is an advantage in that it is easier to create in advance a state in which the natural electrode potential of the pin fins is "baser" than the natural electrode potential of the plate portion as a corrosion prevention measure.

[0069] <Comparison with Heat Sinks in Conventional Patent Publications> In order to explain this effect in more detail, various conventional heat sinks will be explained, focusing on their manufacturing methods.

[0070] According to one example of the prior art, heat sinks are made by utilizing casting and cutting processes (for example, Japanese Patent Laid-Open Publication No. 2001-102506).

[0071] Furthermore, the heat sink described in Japanese Patent Publication No. 2005-57033 includes a process of forming an extruded material by extrusion molding and a process of cutting a large number of plate fins from the extruded portion with a cutter, thereby manufacturing a heat sink having a large number of plate fins integrally formed on one surface of a base plate (base portion).

[0072] In addition, Japanese Patent Publication No. 2017-42861 (JP 2017-42861 A) describes a method of forming multiple plate-shaped fins by forming grooves in a metal workpiece using a multi-cutter. Furthermore, Japanese Patent Publication No. 2017-54895 (JP 2017-54895 A) also describes an example of using plate fins, but describes a heat sink in which multiple plate fins are integrally formed on a base portion by cold extrusion.

[0073] As mentioned above, as taught in Patent Publications 1 to 4, heat sinks can be formed using various methods, but applying these to pin fin heat sinks presents performance and cost challenges. In other words, the pin fin type has the advantage of being able to more precisely set the amount of heat exchange for cooling according to the position on the base plate by adjusting the number and height of the pin fins and changing their placement density, and so has tended to be used particularly frequently in recent years.

[0074] In such a situation, known examples focusing on pin fin-type heat sinks include Patent Publication 5 (JP 2023-44133), Patent Publication 6 (JP 2006-114668), Patent Publication 7 (JP 2023-92828), Patent Publication 8 (JP 2020-92250), Patent Publication 9 (JP 10-190265), Patent Publication 10 (JP 11-307705), Patent Publication 11 (JP 2020-17587), etc.

[0075] The heat sink taught in Japanese Patent Publication No. 2005-103667 has a structure in which a plurality of pin fins are formed integrally on the surface of a plate-shaped base in a forested manner. Specifically, a plurality of holes are drilled in the surface of a die in a desired two-dimensional array, a metal material (such as aluminum) is placed in the center of the surface, and then the metal material (preferably while heated) is pressed toward the die under desired conditions. This forces the metal material to flow into the plurality of holes. The die is then removed, resulting in a heat sink that is integral with the base and has a forest of pin fins extending from its surface.

[0076] However, in Patent Publication 5, the metal material is initially placed in the center of the die surface, so the typical example is to have different diameters for the holes in the center and the holes in the periphery (the hole diameter in the center is greater than the hole diameter in the periphery). In other words, the basic requirement of the teachings of Patent Publication 5 is that the cross-sectional area of ​​the holes, i.e., the cross-sectional area of ​​the pins, should be gradually or continuously reduced from the center of the base surface toward the periphery. Therefore, for example, when this pin-fin heat sink is used in a forced cooling system, the center of the base, where the cross-sectional area of ​​the pin fins is larger, has the highest heat exchange capacity. In other words, when used to cool multiple semiconductor packages with different heat dissipation, the design conditions for the package mounting position become strict. Therefore, it remains insufficient to achieve the desired high cooling performance and reduced manufacturing costs.

[0077] Furthermore, Japanese Patent Publication No. 2006-106663 discloses a method for manufacturing a pin fin heat sink by solder-plating multiple separately formed pin fins and a base portion. However, in the heat sink described in this publication, a flange portion with a diameter larger than the pin fin is provided near the longitudinal base end of each pin fin, and a solder plating layer of a predetermined thickness is formed on the pin fins below the flange portion. Meanwhile, pin insertion holes that fit the base end portions of each pin fin are formed at predetermined intervals on the surface of the base portion. The base ends of the pin fins are inserted into these pin insertion holes, and the solder plating layer is melted by heating. As a result, the multiple pin fins are integrated with the base portion with their flanges abutting the surface of the base portion, forming a heat sink with multiple pin fins standing tall on the surface of the base portion.

[0078] However, in the case of the pin fin heat sink described in Patent Publication 6, a flange is provided at the bottom of each pin fin to secure its base end. The diameter (size) of this flange is naturally larger than the diameter (cross-sectional diameter and size) of the pin. Therefore, it is difficult to reduce the arrangement density of the pin fins on the surface of the base, and there is little freedom in adjusting the arrangement density on the surface.

[0079] Furthermore, Patent Publication 7 exemplifies the formation of multiple round-bar pin fins of different thicknesses on a base portion, but the manufacturing process also involves a die preparation step and a pressurizing step (using a forging device) in which a sealed metal material is pressed against the die to integrally form the pin fins and base portion. Patent Publication 8 exemplifies a structure in which multiple directional, approximately diamond-shaped pin fins are arranged in different positions in the refrigerant passage depending on the orientation of the pin fins, but the pin fins are integrally formed by punching together with other elements such as a top plate.

[0080] The examples of Patent Publications 7 and 8 also have the same disadvantages as those of Patent Publications 5 and 6.

[0081] Furthermore, in Patent Publication 9, the spacing between multiple pin fins is formed so that it increases as the cooling air moves from the upwind side to the downwind side, and an arrangement is adopted that takes into consideration the escape of the cooling air to the outside. Furthermore, Patent Publication 10 devise an arrangement of pin fins that stand in rows on a substrate, taking into consideration the height and arrangement density of the pin fins on the upwind and downwind sides of the center of the substrate. These examples described in Patent Publications 9 and 10 can contribute to improving cooling performance, but there is no suggestion from the perspective of reducing manufacturing costs, which is a problem with heat sinks that use pin fins.

[0082] Furthermore, Patent Publication 11 discloses a configuration in which a plurality of fins made of aluminum in the shape of diamond pillars are integrally formed on a base by forging. It also suggests that the fins can be joined to the base by brazing. However, considering the additional steps involved in forging, there are still difficulties in terms of manufacturing cost. On the other hand, it has also been suggested that the fins can be joined by brazing, but brazing itself is a commonly used joining method, so this alone does not provide any useful hints to those skilled in the art.

[0083] As described above, even the pin fin type heat sinks described in the above-mentioned Patent Publications 1 and 5 to 11 are far from achieving the high cooling performance and further reduction in manufacturing costs that are currently required.

[0084] In contrast, as described above, the heat sink body 30 according to this embodiment is formed by integrating the pin fins 22 and the base plate 20 by diffusion bonding (thermocompression bonding). This makes it easier to form a simple integrated structure, and it is also easier to satisfy required design specifications, such as the shape and height of the pin fins 22 and their arrangement density on the base plate 20, thereby achieving good cooling performance. Furthermore, this can be achieved more easily and at lower cost than conventional processing methods such as die casting.

[0085] In particular, when a die is used to pressurize a metal material, the amount of metal material that is pressed and flows into the multiple holes in the die, i.e., the control of the height of the pin fins, varies depending on the position of the holes. For this reason, it is not technically easy to change the pin height depending on the hole position (pin position) or to precisely control the pin position and placement density. However, according to this embodiment, such inconveniences can be reliably resolved.

[0086] <Modification of First Embodiment> A modification of the above-described manufacturing method will be described with reference to FIG.

[0087] The first embodiment described above employs a thermal diffusion bonding method that relies on the metal diffusion phenomenon caused by heating and pressurizing in a vacuum atmosphere or room air, as typically shown in Fig. 6(D). However, this example can be modified and implemented as shown in Fig. 10.

[0088] 10 shows the bonding process (corresponding to step S5) corresponding to FIG. 6(D), in which microwave irradiation is used to diffuse the metals and bond them together. That is, as shown in FIG. 10, the heat sink body 30 is placed in the chamber VR, and a microwave oscillator 60 is also placed in the chamber VR. Additionally, the chamber VR is filled with a reducing atmosphere, and microwaves are irradiated from the microwave oscillator 60 to the heat sink body 30 while pressurizing the chamber VR with a pressurizer in the same manner as described above. The energy of this microwave causes diffusion in the contact areas between the lower end portions 22L of each pin fin 22 and the lower surface 20L of the base plate 20L, resulting in diffusion bonding between the two.

[0089] The bonding conditions at this time are, for example, pressure = 0.1 MPa to 2000 MPa, microwave frequency = 300 MHz to 30 GHz, microwave irradiation power = 100 to 1000 W, and microwave irradiation time = 50 to 2500 seconds, and appropriate values ​​are selected from these numerical ranges.

[0090] In this way, the diffusion bonding may be performed using microwave energy.

[0091] The configuration other than that of using microwaves is the same as that of the first embodiment, and therefore a description thereof will be omitted.

[0092] As described above, according to the first embodiment and its modified examples, the heat sink body 30 is formed by integrating the pin fins 22 and the base plate 20, which are prepared as separate components, by diffusion bonding.

[0093] Therefore, the pin fins 22 and the base plate 20 can be individually designed and prepared, and then diffusion bonded to be integrated, which increases the degree of freedom in design.

[0094] Specifically, since only individual pin fins need to be formed, conventional forging allows for higher processing precision for each of the multiple pin fins compared to casting. Furthermore, factors such as the size, height, cross-sectional shape, and even the arrangement density of the pin fins 22 on the base plate can be easily tailored to required specifications, allowing for greater design flexibility. It is also unnecessary to provide the pin fins 22 with a draft angle for removing them from a mold, as was previously required. Conversely, a reverse taper can be applied to increase the area of ​​the pin fins that come into contact with the refrigerant. At the same time, a reverse taper narrows the base of the pin fin, thereby reducing flow resistance of the refrigerant and other components. Unlike casting, conventional forging does not limit the height of the pin fins 22 to a certain limit (e.g., 5 mm) due to manufacturing difficulties. Pin fins of unprecedented heights, such as 30 mm, can be formed. The pin arrangement density and pin fin thickness can also be varied depending on the local position on the underside 20L of the base plate 20. All of this can be determined based on the specifications required for the heat sink, contributing to improved cooling performance.

[0095] The joining for integration is also simpler than conventional forging, casting, or machining, because it only needs to be done between the lower end 22R of each pin fin and the pin arrangement position P on the underside 20L of the base plate 20. Of course, if this joining is possible, the integrated heat sink body can be easily manufactured, so the pin fins and base plate may be made of different materials.

[0096] Second Embodiment Next, a second embodiment of the present invention will be described with reference to Figures 11 and 12. In this second embodiment, components that have the same or equivalent functions as those of the first embodiment described above are denoted by the same reference numerals, and their description will be omitted or simplified.

[0097] In the second embodiment, the pin fins 22 (rod-shaped fins) and the base plate 20 (base portion) are prepared as separate components and then joined together, but the joining method is different. Specifically, instead of the diffusion bonding used in the first embodiment, brazing is used in a vacuum or air atmosphere.

[0098] Therefore, as shown in FIG. 11, the manufacturing process is partially different from that shown in FIG.

[0099] Specifically, steps S1 to S3 shown in Fig. 11 are the same as or substantially equivalent to those shown in Fig. 4, and include preparing a plurality of aluminum pin fins 22, an aluminum base plate 20, a carbon pin alignment jig 40, and a pair of plate-shaped carbon clamping jigs 50 (Fig. 11, step S1). However, the lower surface 20L of the base plate 20 is coated with a film of brazing filler metal BR for aluminum.

[0100] Next, the pin alignment jig 40 is set on the base plate 20 so as to cover it ( FIG. 11 , step S2). As a result, as described above, the multiple pin insertion holes 40B of the pin alignment jig 40 are positioned relative to the base plate 20, i.e., with respect to the pin arrangement position P (see FIG. 7 ). Next, in step S3, the multiple pin fins 22 are inserted into the multiple pin insertion holes 40B, respectively. That is, while being supported by the pin alignment jig 40, the multiple pin fins 22 are each made to stand at the pin arrangement position P on the brazing material film BR on the lower surface 20L of the base plate 20. As a result, the heat sink body 30 is formed in the same manner as described above.

[0101] Next, this heat sink body 30 is placed in a chamber VR, a vacuum atmosphere of a predetermined vacuum level is created in the chamber, and an actuator of a pressurizer (not shown) is set via a pair of clamping jigs 50. This completes the preparation as shown in FIG.

[0102] Next, in step S11, the heat sink body 30 is heated for a predetermined time by a heater (not shown) under the control of a predetermined temperature profile, whereby the surfaces (lower end surfaces) of the lower ends 22R of the pin fins 22 and the contact surfaces of the pin arrangement positions P on the lower surface 20L of the base plate 20, which face each other via the brazing filler metal BR, are brazed together and integrated as the brazing filler metal BR melts.

[0103] After this brazing is completed, the heat sink body 30 is removed (step S6).

[0104] As an example, the pressure is 0.05 Pa to 40 MPa, and the vacuum is 10 －４ ~10 －６ Torr, the heating time is set to 30 minutes to 3 hours, and the heating temperature is set to 500 to 620°C.

[0105] As described above, the second embodiment also provides the same advantageous effects as the first embodiment, and allows for a variety of joining methods. Furthermore, the brazed lower end 22R of each pin fin 22 has a brazed portion FT that flares outward from the underside 20L of the base plate 20, resembling Mount Fuji, in a side view. This reduces stagnation of the cooling fluid FL flowing nearby the lower end 22R.

[0106] <Modification of the Second Embodiment> The joining method employed in the second embodiment described above may be replaced by brazing in an air atmosphere. In this case, in the preparation process described in step S1 described above, a powder-like flux FL specifically for aluminum brazing is applied in the form of a film on the film of the brazing filler metal BR described above (see FIG. 13). As shown in FIG. 13, this promotes wetting of the brazing material and removes the oxide film on the aluminum surface, ensuring reliable brazing even when heat treatment is performed in an air atmosphere, a reducing atmosphere, or a vacuum atmosphere.

[0107] An example of the brazing conditions is a pressure applied by a pressure jig of 0.01 Pa to 10 MPa, a heating time of 10 minutes to 6 hours, and a heating temperature of 500 to 650°C.

[0108] <Another Modification> <Modification 1> A structure that can be applied to both the first and second embodiments described above will be described as another modification 1 with reference to Fig. 14. This structure relates to a corrosion prevention structure for a pin fin heat sink, and can be implemented in each of the above-described embodiments and their modifications.

[0109] Conventionally, pin fin or plate fin heat sinks have been manufactured by forging, casting, or by adding machining to these methods. In other words, since they are manufactured from the same base material from the beginning, the natural electrode potential E (also called corrosion potential or natural potential) of the parts that make up the fins and base plate is the same.

[0110] It is generally known that corrosion pits form over time in the pin fins and base plate due to the corrosive components of the refrigerant or cooling water flowing through the heat sink (schematically shown by the reference symbol CO in Figure 14). If the corrosion progresses to the point where the corrosion pit CO penetrates the base plate, it is expected that refrigerant or cooling water leakage will occur, significantly impairing cooling performance and reducing the functionality of the electronic components being cooled. Such a situation can lead to a breakdown in the reliability of the electronic components, and therefore to a breakdown in the target system, so it is desirable to avoid such an occurrence, or at least to prevent such an occurrence during the warranty period.

[0111] The inventors have considered that such corrosion-related problems are one of the problems inherent in the conventional method of integrally molding the fins and base plate. In response, the inventors have conceived the idea that another advantage of preparing the fins and base plate as separate components, as in the present invention, is that the progression of such corrosion can be controlled between the fins and base plate. As a specific solution, in the preparation process of step S1 in the manufacturing method described above (FIGS. 4 and 11), when the pin fins 22 and the base plate 20 are prepared separately, elements such as ZN (zinc), SN (tin), and LN (lanthanides) are added to the aluminum (Al) material of the pin fins 22 to form the pin fins 22 as an aluminum alloy. In this case, for example, the base plate 20 is formed from aluminum or an aluminum alloy. This makes the natural electrode potential EF of the pin fins 22 (aluminum alloy) electrochemically lower than the natural electrode potential EP of the base plate 20 (EF < EP: noble potential). For example, the natural electrode potential of the pin fins 22 is set to be less noble than the natural electrode potential of the base plate 20 by a potential (e.g., 100 mV) selected from a predetermined potential range (e.g., 20 to 200 mV). According to this example, the pin fins 22 and the base plate 20 are prepared separately and then integrated by bonding, making it easy to set the above-mentioned relationship of EF<EP.

[0112] Therefore, even if the above-mentioned corrosion pitting CO occurs in both the pin fins 22 and the base plate 20 with use over time, the corrosion rate of the base plate 20 is slower than that of the pin fins 22. Since a large number of pin fins 22 are typically installed upright, even if corrosion occurs in a small number of these pin fins 22, it is unlikely to significantly reduce cooling performance. Instead, by subjecting the pin fins 22 to sacrificial corrosion while delaying the occurrence of corrosion pitting CO in the base plate 20, the life of the base plate 20 is extended against corrosion pitting, and the high cooling performance of the pin fin heat sink 12 can be maintained for a long period of time. Additionally, corrosion-resistant surface treatments (e.g., anodizing) can be eliminated.

[0113] <Modification 2> A structure applicable to both the first and second embodiments will be described as another modification 2 with reference to Fig. 15. This structure, relating to the shape of the pin fins of the pin fin heat sink, can be implemented in each of the above-described embodiments and their modifications.

[0114] 15, a plurality of pin fins 22X are provided on the underside 20L of a base plate 20X, and a heat sink body 30X is manufactured by joining separate components together by metal bonding. In this respect, the basic structure is the same as that of the above-described embodiment and modified examples.

[0115] In this second modification, the dimensions Wt and Wr of the tip 22T and bottom 22R of each pin fin 22X are set such that Wt > Wr. These end dimensions Wt and Wr are expressed as the diameter if the pin fin 22X is cylindrical, or as the diagonal length of a horizontal cross section if the pin fin 22X is prismatic. Whether the pin fin 22X is cylindrical or prismatic, the horizontal cross section increases in size as it approaches the tip due to the Wt > Wr relationship. In other words, the pin fin 22X has an inverted trapezoidal shape (inversely tapered, when viewed in a vertical cross section) with a larger diameter at the top. In FIG. 13 , reference symbol CX denotes the metal joint between the bottom 22R of each pin fin 22X and the base plate 20X at the arrangement position P.

[0116] Conventionally, in the case of forging or casting, the pin fins had to be provided with a draft gradient (a sloped side surface that reduces the cross-sectional size toward the tip) during the removal process from the mold. However, this conventional draft gradient is no longer necessary because the pin fins and base plate are integrated from separate components by metal joining. Conversely, the reverse gradient (a gradient in which the lateral cross-sectional size increases toward the tip: a negative draft gradient) allows the surface area of ​​the pin fins 22X to be larger than that of pin fins that required a draft gradient in the past. This increases the area in contact with the cooling fluid FL, such as a refrigerant, thereby increasing the heat exchange capacity of each pin fin 22X and improving cooling performance.

[0117] Of course, it is also possible to set Wt=Wr so that the rod-shaped fins stand straight upright in the upright fin state without providing a negative draft angle.

[0118] <Modification 3> A structure applicable to both the first and second embodiments will be described as another modification 3 with reference to Fig. 16. This structure, relating to the shape of the pin fins of the pin fin heat sink, can be implemented in each of the above-described embodiments and their modifications.

[0119] As can be seen from Figure 16, this variant 3 relates to a pin fin shape in which the length Hp of the pin fin 22X in the longitudinal direction (Z-axis direction) described in variant 2 is significantly longer than its horizontal cross-sectional size. As an example of this length Hp, if the average diameter of the horizontal cross section of a round bar-shaped pin fin is 3 mm, then the length Hp is a value of 40 to 60 mm. Note that in Figure 16 as well, reference symbol CX denotes the metal joint between the lower end 22R of each pin fin 22X at arrangement position P and the base plate 20X.

[0120] This is also a technique that can be achieved using the structure and manufacturing method disclosed herein, in which "the pin fins and base plate are integrated from separate parts by metal joining." Even if the number of pin fins is small, the length of the pin fins in the longitudinal direction can increase the area that comes into contact with the cooling fluid FL, thereby providing high cooling performance.

[0121] <Modification 4> A structure applicable to both the first and second embodiments will be described as another modification 4 with reference to Fig. 17. This structure, relating to the shape of the pin fins of the pin fin heat sink, can be implemented in each of the above-described embodiments and their modifications.

[0122] As shown schematically in FIGS. 17A, 17B, and 17C, a plurality of pin fins 22 (here, cylindrical) have a plurality of dimples DP (FIG. 17A), spiral grooves SG (FIG. 17B), and diagonal grooves OG (FIG. 17C) machined on their surfaces. One or more of these dimples DP, spiral grooves SG, or diagonal grooves OG are machined to match the shape and size of the pin fins 22. Because the pin fins 22 are individually prepared in advance, such additional machining is easy. At the same time, the area of ​​contact between the plurality of pin fins 22 and the refrigerant can be increased, which, as described above, contributes to improved cooling performance. In addition, arranging the pin fins in a way that takes into account the erection position P of each pin fin 22 and its orientation, i.e., the orientation of the spiral grooves SG and diagonal grooves OG, can also contribute to controlling the flow of the refrigerant.

[0123] <Modification 5> A structure applicable to both the first and second embodiments will be described as another modification 5 with reference to Fig. 18. Modification 5 relates to a structure for arranging a plurality of pin fins (rod-shaped fins) 22 straight and vertically at the respective pin arrangement positions P on the underside 20L of the base plate 20 when manufacturing a pin fin heat sink.

[0124] Although it is possible to erect the pin fins 22 at an angle to the base plate 20, when considering that a plurality of pin fins 22 are normally arranged in a forest to form a pin fin assembly FIN, it is desirable to erect the plurality of pin fins 22 vertically on the base plate 20 (lower surface 20L) in terms of flow velocity analysis of the cooling fluid FL such as a refrigerant and calculation of heat exchange efficiency. From this perspective, the fifth modification aims to further improve the accuracy of the above-mentioned pin alignment jig 40 in terms of vertical arrangement of the pin fins.

[0125] As shown in Figure 18, by setting the pin alignment jig 40 on the base plate 20, pin alignment positions P are set in an array in a plan view on the underside 20L of the base plate 20 directly below each pin insertion hole 40B of the pin alignment jig 40. Therefore, positioning holes PH of a predetermined diameter, each with a bottom and a tapered surface 40T, are drilled in the base plate 20 at positions corresponding to each pin alignment position P. During manufacturing, each pin fin 22 is inserted through each pin insertion hole 40B of the pin alignment jig 40 so that its lower end 22R fits into the positioning hole PH. A fillet FT is formed in the positioning hole PH by thermal diffusion bonding. This allows each pin fin 22 to be planted vertically.

[0126] 18, to make it easier to vertically position the pin fins, another step may be added to the plate-like portion 40A extending laterally from the wall portion 40C, as shown by the imaginary line 40D, thereby improving the vertical support performance of the pin fins 22 with the two-step plate-like portions 40A, 40D. Of course, the thickness of at least the pin insertion hole 40B portion of such a pin alignment jig 40 can also be increased to improve the vertical support performance of the pin fins 22. Note that the wall portion 40C of this pin alignment jig 40 and the side surface of the base plate 20 may not simply be in contact with each other, but may be engaged with a locking mechanism or latch mechanism (represented by reference numeral 40E) to more reliably secure the pin fins in place when positioned.

[0127] <Modification 6> A structure applicable to both the first and second embodiments will be described as another modification 6 with reference to FIG.

[0128] This modification 6 relates to another example showing the shape of the lower end 22R of the pin fin 22 and the shape of the positioning hole PH, and shows two modes. In both modes, the lower end 22R of the pin fin 22 is press-fitted into the positioning hole PH, and then the two are integrated by, for example, diffusion bonding.

[0129] In the first mode, as shown in FIG. 19A, a tapered surface θ of a certain angle is formed at an end 22LW of a certain length including a lower end 22R of a pin fin 22E. ＰIn addition, the side surface of the positioning hole PH also has a tapered surface θ Ｐ Therefore, the lower end 22R of the pin fin 22E can be press-fitted into the positioning hole PH, and then the diffusion bonding described above can be performed. This press-fitting ensures that the pin fin 22E is positioned upright. Furthermore, as shown in the figure, the number of surfaces to be diffusion-bonded increases to M1 (the tapered circumferential surface) and bottom surface M2 (flat surface), resulting in a more reliable bond than diffusion bonding of only the bottom surface.

[0130] In addition, the portion of each pin fin 22E facing the base plate (end 22LW) is thinner than the remaining cylindrical portion at the tip. This reduces flow resistance to the cooling fluid FL, allowing the fluid FL to flow more along the surface of the base plate 20. This improves the efficiency of heat absorption from the base plate 20 and improves cooling efficiency.

[0131] 19B shows a second aspect of the sixth modified example. In this aspect, the tapered relationship between the plate and the pin at the lower end 22R shown in FIG. 19A is maintained, but the overall shape of the pin fins 22F is different. That is, each pin fin 22F has a tapered surface θ of the end 22LW similar to the inversely tapered pin fin 22X shown in FIG. 16. Ｐ is continuously connected to the remaining portion. In other words, the pin fin 22F has a tapered surface θ Ｐ It is formed in an inverted tapered shape.

[0132] Therefore, in this second embodiment, the same effects as those described above can be obtained, and the effects of Modification 3 described in Figure 16 can also be enjoyed. Although not shown, instead of Modification 6 described above, tiny mounts that serve as supports for erecting the pin fins 22F may be formed at each of the pin erection positions on the underside 20L of the base plate 20, and the pin fins 22F may be erected in a similar manner in positioning holes PH drilled only in those mounts, or in positioning holes PH drilled as described above via those mounts. In this case, the mounts are made of aluminum or copper, and are made to match the materials of the pin fins and base plate. If the mounts are made of copper, it is desirable that the mounts located at the bases of the pins be treated with an anti-corrosion treatment such as nickel plating.

[0133] <Seventh Modification> A structure applicable to both the first and second embodiments will be described as a seventh modification with reference to FIG.

[0134] As shown in FIG. 20 , even if the pin fins 22 (22B, 22S) are, for example, round-bar pin fins, when multiple pin fins 22 are arranged in an array in a plan view to form an assembly FIN, the horizontal cross-sectional areas of all pin fins 22 do not need to be the same. That is, the cross-sectional area of ​​pin fins 22B arranged in areas of the base plate 20 (lower surface 20L) requiring greater heat exchange may be increased. That is, the diameter may be increased (r1 > r2: r1 is the diameter of a thick pin fin, and r2 is the diameter of a thin pin fin). Of course, this cross-sectional area (diameter) may be divided into three or more levels, such as large, medium, and small. In FIG. 20 , reference symbol FL indicates the flow of cooling fluid FL (cooling air, cooling water, refrigerant).

[0135] To simplify the discussion, when the discharge conditions of the cooling fluid FL, flow path resistance, and other fluid supply conditions are the same, the size of the cross-sectional area (diameter in the case of a round bar) mentioned above adjusts the contact area when the cooling fluid FL comes into contact with the pin fins 22. By the same concept, the height h1 of the pin fins 22B arranged in an area requiring a larger amount of heat exchange among the assembly FIN of multiple pin fins 22 (22B, 22S) may be made higher than the height h2 of the pin fins 22S arranged in other areas (h1>h2).

[0136] Of course, either the cross-sectional area (diameter, etc.) or the height may be selected, or both may be selected and adjusted simultaneously.

[0137] In addition, the arrangement density of the pin fins 22 (22B, 22S) may be adjusted for each partial region of the pin fin assembly FIN (D1>D2: an example where the arrangement density of pin fins that require a higher heat exchange capacity is D1, and the arrangement density that does not is D2).

[0138] <Modification 8> A structure applicable to both the first and second embodiments will be described as another modification 8 with reference to FIG.

[0139] As shown in FIGS. 21A to 21D, the horizontal cross-sectional shape of the pin fins (rod-like fins) 22 (22K, 22T, 22S, 22D) does not necessarily have to be circular, as described above. For example, as shown in FIG. 21A, the pin fins may have a rectangular shape (fin 22K), such as a square or a rectangle. As shown in FIGS. 21B and 21C, the pin fins may have a polygonal shape, such as a rhombus or a triangle (fins 22T, 22S), or may have an elliptical shape (fin 22D) as shown in FIG. 21D. The array of these pin fins 22 (22K, 22T, 22S, 22D) is arranged to secure a designed surface area and provide a designed fluid resistance for the cooling fluid FL, as in FIG. 20 .

[0140] REFERENCE SIGNS LIST 1 Cooling device 10 Semiconductor package (electronic component, electrical component) 12 Pin fin heat sink as rod-shaped fin heat sink 14 Cover 20, 20X Base plate (functions as base portion) 20U Upper surface 20L Lower surface 22, 22X, 22E, 22F Pin fin as rod-shaped fin 22T Tip portion 22R Lower end portion 30 Heat sink body (part of fin-shaped heat sink) 40 Pin alignment jig (functions as fin alignment jig) 40A Plate-shaped portion 40B Pin insertion hole (functions as fin insertion hole) 40C Wall portion 50 Clamping jig FIN Pin fin assembly (corresponding to rod-shaped fin assembly) FL Cooling fluid

Claims

1. A rod-fin heat sink that absorbs and dissipates heat generated by an electric element through heat exchange, comprising: a thermally conductive base having a first surface that comes into contact with the electric element and a second surface facing the first surface; and a rod-fin heat sink provided as a separate part from the base, comprising a plurality of thermally conductive rod-shaped fins, each of which has a longitudinal direction, one end of each of the plurality of rod-shaped fins being joined to the second surface to form an integrated unit, and the plurality of rod-shaped fins as a whole being arranged in a forest on the second surface.

2. The rod-fin heat sink as described in claim 1, characterized in that the plurality of rod-shaped fins and the base portion are both formed from an alloy whose main component is aluminum or copper.

3. A rod-fin heat sink as described in claim 2, characterized in that at least a portion of the plurality of rod-shaped fins on the second surface when the second surface is viewed in a plane differ from the remaining rod-shaped fins in at least one of their arrangement density and height.

4. A rod-shaped fin heat sink as described in any one of claims 1 to 3, characterized in that each of the multiple rod-shaped fins has a longitudinal direction, and the cross-sectional area perpendicular to the longitudinal direction is of a constant size and the same shape regardless of the position in the longitudinal direction, or is of a size that varies depending on the position but is the same shape.

5. A rod-shaped fin heat sink as described in any one of claims 1 to 3, characterized in that the cross section of the rod-shaped fin perpendicular to the longitudinal direction of the rod-shaped fin is circular, polygonal having three or more sides and angles, or elliptical.

6. A rod-fin heat sink as described in any one of claims 1 to 3, characterized in that each of the plurality of rod-shaped fins has at least one of dimples, spiral grooves, and oblique ring-shaped grooves formed on its surface.

7. A rod-shaped fin heat sink as described in any one of claims 1 to 3, characterized in that the natural electrode potential of the rod-shaped fins relative to the natural electrode potential of the base portion is set to be electrochemically baser.

8. The rod-shaped fin heat sink according to claim 7, characterized in that the plurality of rod-shaped fins and the base portion are both formed from an alloy primarily composed of aluminum or copper, and the rod-shaped fins are formed from a material obtained by adding an electrochemically less noble element to the alloy.

9. A rod-shaped fin heat sink as described in any one of claims 1 to 3, characterized in that the end face of one end of each of the plurality of rod-shaped fins is surface-joined at a corner position of the second surface.

10. A rod-shaped fin heat sink as described in any one of claims 1 to 3, characterized in that a recess is formed in each position of the second surface where each of the multiple rod-shaped fins abuts, into which one end of each of the multiple rod-shaped fins fits, and the joining is performed with the one end of each of the multiple rod-shaped fins fitted into the recess.

11. A rod-shaped fin heat sink as described in any one of claims 1 to 3, wherein one longitudinal end of each of the plurality of rod-shaped fins is integrally joined to the second surface by diffusion bonding or thermocompression bonding, brazing, or joining by microwave irradiation.

12. A cooling device for cooling an electric element, comprising a rod-shaped fin type heat sink as claimed in any one of claims 1 to 3, and a fluid circulating means for circulating a cooling fluid through said heat sink to effect heat exchange between said heat sink and the rod-shaped fins of said heat sink.

13. A cooling device equipped with a rod-shaped fin heat sink that absorbs and dissipates heat generated by the electric element through heat exchange, the rod-shaped fin heat sink comprising: a thermally conductive base portion having a first surface that comes into contact with the electric element and a second surface that faces the first surface; and a rod-shaped fin assembly provided as a separate part from the base portion, each of which has a longitudinal direction and is made up of a plurality of thermally conductive rod-shaped fins, one end of each of the longitudinal directions of the plurality of rod-shaped fins being joined to the second surface to be integrated, the plurality of rod-shaped fins being arranged as a whole in a forested state on the second surface; the fluid circulating means comprising: a case that cooperates with the second surface of the base portion to surround the assembly of the plurality of rod-shaped fins standing on the second surface, and in which a space is formed through which the cooling fluid passes between the plurality of rod-shaped fins in one direction of the assembly; 13. The cooling device according to claim 12, further comprising: a pipe provided in the case for circulating the fluid to the rod-fin heat sink; and a fluid source for circulating the fluid through the pipe and the space.

14. A method for manufacturing a rod-shaped fin heat sink, comprising: a first step of setting a pin alignment jig on the base part so as to face the second surface, the pin alignment jig having a plurality of through holes formed therein that correspond to the diameters and erected positions of the plurality of rod-shaped fins, the pin alignment jig having a first surface to be brought into contact with an electric element and a second surface opposing the first surface in a thickness direction, and a plurality of columnar and thermally conductive rod-shaped fins to be erected on the second surface, and inserting the plurality of rod-shaped fins into the plurality of through holes so that one end of each of the plurality of rod-shaped fins protrudes from the plurality of through holes; a second step of setting a pressure jig that applies pressure between the first surface of the base part and one end of each of the plurality of rod-shaped fins protruding from the plurality of through holes of the pin alignment jig; and a third step of joining the other end of each of the plurality of rod-shaped fins to the second surface of the base part while applying pressure with the pressure jig or a pressure device.

15. A method for manufacturing a rod-fin heat sink as set forth in claim 14, characterized in that the plurality of rod-shaped fins and the base portion are both formed from an alloy primarily composed of aluminum or copper.

16. In the method for manufacturing a rod-shaped fin heat sink as described in claim 15, the first step is characterized by comprising: a pin plate preparation step of preparing the rod-shaped fins and the base portion as separate parts; a jig setting step of first setting the pin alignment jig on the base portion; and a tweezers step of, after setting the pin alignment jig on the base portion, inserting the rod-shaped fins into the through holes of the pin alignment jig so that one end of each of the rod-shaped fins protrudes from the through holes.

17. In the method for manufacturing a rod-shaped fin heat sink as described in claim 14 or 15, the pin alignment jig has a plate-shaped portion, the plurality of through holes are drilled in the plate-shaped portion in a two-dimensional array in a planar view, and the size of each of the plurality of through holes is formed to a value that allows the plurality of rod-shaped fins to fit into each of the plurality of through holes.

18. In the method for manufacturing a rod-shaped fin heat sink as described in claim 14 or 15, the third step is characterized in that it is carried out in a vacuum atmosphere, and is a step of heating the contact portions between the other ends of each of the plurality of rod-shaped fins and the second surface of the base portion from a heat source to perform diffusion bonding.

19. A method for manufacturing a rod-shaped fin heat sink as described in claim 14 or 15, characterized in that the second surface of the base portion is coated with a brazing material, and the third step is carried out in a vacuum atmosphere or an atmospheric atmosphere, and is a step of heating and brazing the coated brazing material to the abutting portions between the other end of each of the multiple rod-shaped fins and the second surface of the base portion.

20. In the method for manufacturing a rod-shaped fin heat sink as described in claim 14 or 15, the third step is characterized in that it is carried out in a reducing atmosphere and is a step of irradiating microwaves from a microwave source to the abutting portion between the other end of each of the multiple rod-shaped fins and the second surface of the base portion to cause thermal diffusion bonding.

21. In the manufacturing method of a rod-shaped fin heat sink as described in claim 15, the pin plate preparation process is characterized in that the natural electrode potential of the pin relative to the natural electrode potential of the base portion is set to be lower by a potential selected from a predetermined potential range.

22. A method for manufacturing a rod-shaped fin heat sink as described in claim 15, characterized in that the rod-shaped fins and the base portion are both formed from an alloy mainly composed of aluminum or copper, and the rod-shaped fins are formed from a material obtained by adding an electrochemically less noble element to the alloy.

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