JP6065925B2 - Heat sink manufacturing method and heat sink - Google Patents

Description

  The present invention relates to a method for manufacturing a heat sink and a heat sink.

  For example, Patent Document 1 discloses a heat sink manufacturing method in which a substrate and a plurality of pin-shaped fins standing on the substrate are solid-phase bonded by friction welding. The friction welding process according to Patent Document 1 includes a friction process in which a surface of a substrate and an end face of a pin-shaped fin are brought into contact with each other, and then the substrate and the pin-shaped fin are reciprocated linearly to form a high-temperature layer by frictional heat. And a pressure-contacting step for applying an upset pressure.

  (A)-(d) of FIG. 13 is a schematic sectional side view which shows the joining state of a board | substrate and a pin-shaped fin in steps in the manufacturing method of the conventional heat sink. 14A to 14D are schematic plan views corresponding to FIGS. 13A to 13D.

  As shown in FIG. 13A, in the conventional heat sink manufacturing method, the surface 110 a of the substrate 110 and the end surface 120 a of the pin-shaped fin 120 are abutted, and the pin-shaped fin 120 is straight with respect to the substrate 110. The friction process is performed by reciprocating in the shape. In the friction process, the pin-shaped fin 120 is reciprocated in the left-right direction (see arrows) in the drawing.

  As shown in FIGS. 13B to 13D, the fillet 130 is formed by the friction welding process. The fillet 130 is a part formed on the outer periphery of the tip of the pin-shaped fin 120 by softening the tip side of the pin-shaped fin 120 and protruding the base material in the friction welding process. As shown in FIG. 13A, when the friction welding process is performed, the surface 110a of the substrate 110 has a first region X that is always in contact with the pin-shaped fin 120, and the pin-shaped fin 120 with reciprocation. And second regions Y and Y that repeat contact or non-contact with each other.

Japanese Patent Laid-Open No. 11-340392

  The second regions Y and Y are cooled because they are exposed to the atmosphere when they are not in contact with the pin-shaped fins 120 in the friction welding process. Therefore, the frictional heat is smaller in the second regions Y and Y than in the first region X. Therefore, as shown in FIGS. 13B to 13D, even if the fillet 130 is formed by the reciprocating motion of the pin-shaped fin 120, the second regions Y, Y having low frictional heat and the fillet 130 are joined. It becomes difficult to bond, the bonding strength decreases, and a bonding defect Q may occur in the bonded portion.

  On the other hand, the area (heat generating part Z) indicated by hatching in FIGS. 14A to 14D shows an area where frictional heat is generated step by step as the friction process proceeds. As shown in FIG. 14A, since the heat generating portion Z has low frictional heat in the initial state, the heat generating portion Z has a substantially elliptical shape elongated in a direction orthogonal to the amplitude direction (hereinafter referred to as “orthogonal direction”). Present. As shown in (b) to (d) of FIG. 14, in the heat generating portion Z, when the friction process proceeds, the length dimension in the amplitude direction gradually increases without changing the length dimension in the orthogonal direction. Since the shape of the fillet 130 is affected by frictional heat, the shape of the fillet 130 increases substantially in a similar manner with the deformation of the shape of the heat generating portion Z. That is, the fillet 130 tends to have a length dimension in the orthogonal direction larger than a length dimension in the amplitude direction. In other words, in the friction welding process, since the amplitude direction (reciprocating direction) is one direction, there is a problem that the fillet 130 is not formed with good balance.

  From such a viewpoint, it is an object of the present invention to provide a method of manufacturing a heat sink that can increase bonding strength, prevent occurrence of bonding defects, and can bond pin-shaped fins in a balanced manner. Moreover, this invention makes it a subject to provide the heat sink with which a pin-shaped fin is joined with sufficient balance.

In order to solve such a problem, the present invention is a method of manufacturing a heat sink having a copper or copper alloy substrate and a plurality of aluminum or aluminum alloy pin-like fins erected on the substrate, The plurality of holes of the second jig are arranged so that the substrate heated to 400 to 500 ° C. is disposed on the first jig and the tips of the plurality of pin-shaped fins are exposed from the second jig. A step of arranging a plurality of the pin-shaped fins, abutting the end surfaces of the plurality of pin-shaped fins on the surface of the heated substrate, and relatively moving the first jig and the second jig. And a friction welding process in which the substrate and the pin-shaped fin are reciprocated linearly to perform friction welding.

According to such a manufacturing method, even if a region where the substrate and the pin-shaped fin are not in contact with each other is formed, the substrate is heated in advance, so that the temperature drop in the region can be suppressed. Thereby, it is possible to increase the bonding strength by reliably bonding the surface of the substrate and the fillet, and to prevent the occurrence of bonding defects.
In addition, since the substrate is preheated, the pin-shaped fins are greatly softened in the initial state of the friction welding process. Thereby, the heat generating part formed between the surface of the substrate and the end face of the pin-shaped fin is formed with a good balance between the amplitude direction of the friction welding and the orthogonal direction orthogonal to the amplitude direction. Along with this, the difference between the length dimension of the fillet in the amplitude direction and the length dimension in the orthogonal direction can be reduced, so that the joints can be joined with good balance.

  Moreover, while forming the said board | substrate with copper or a copper alloy, thermal conductivity can be improved by forming the said pin-shaped fin with aluminum or an aluminum alloy. Further, the weight can be reduced and the material cost can be reduced.

  In the friction welding process, the amplitude is preferably set to 1.2 to 1.8 mm. According to this manufacturing method, it is possible to further increase the bonding strength and prevent the occurrence of bonding defects.

Further, the present invention provides a heat sink which have a pin-shaped fins made of a plurality of aluminum or aluminum alloy which is erected a substrate made of copper or copper alloy on the substrate, the substrate and the plurality of pin-like fins The fillet made of the same material as that of the pin-shaped fin formed at the joint portion has a ratio of the minimum diameter to the maximum diameter of 0.75 to 0.99 and is extremely thin at the joint interface of the joint portion. A copper / aluminum reaction layer is present .

  According to such a configuration, the difference between the maximum diameter and the minimum diameter of the fillet can be reduced, so that the pin-shaped fins can be joined with a good balance.

  According to the heat sink manufacturing method of the present invention, it is possible to increase the bonding strength, prevent the occurrence of bonding defects, and bond the pin-shaped fins with a good balance. Moreover, according to the heat sink which concerns on this invention, a pin-shaped fin is joined with sufficient balance.

It is a perspective view which shows the heat sink which concerns on embodiment of this invention, Comprising: (a) is a general view, (b) is an enlarged view. It is sectional drawing which shows the manufacturing method of the heat sink concerning this embodiment, Comprising: (a) shows a preparatory process, (b) shows the butt | matching process of a friction welding process. It is sectional drawing which shows the manufacturing method of the heat sink which concerns on this embodiment, Comprising: (a) shows the friction process and press-contact process of a friction welding process, (b) shows the taking-out process. (A)-(d) is a typical sectional side view which shows the joining state of a board | substrate and a pin-shaped fin in steps in the manufacturing method of the heat sink of this embodiment. (A)-(d) is a schematic plan view corresponding to (a)-(d) of FIG. (A) is a perspective view which shows the test body of an Example, (b) is a perspective view which shows the test piece of an Example, (c) is a plane sectional view which shows a fillet. It is a table | surface which shows the conditions of the manufacturing method of an Example. It is a graph which shows the relationship between the substrate heating temperature of an Example, and joining strength. It is a cross-sectional microstructure figure of the junction part of an Example. It is a graph which shows the relationship between the substrate heating temperature of an Example, and a fillet diameter ratio. It is a graph which shows the relationship between the fillet diameter ratio of an Example, and joining efficiency. It is a graph which shows the relationship between the amplitude of an Example, and a pin-shaped fin joint rate. (A)-(d) is a typical sectional side view which shows the joining state of a board | substrate and a pin-shaped fin in steps in the manufacturing method of the conventional heat sink. (A)-(d) is a schematic plan view corresponding to (a)-(d) of FIG.

  Embodiments of the present invention will be described in detail with reference to the drawings. First, the heat sink 1 according to the present embodiment will be described. As shown in FIG. 1A, the heat sink 1 includes a substrate 2 and pin-like fins 3. The heat sink 1 is a member that radiates heat from a semiconductor element such as an IC or a transistor.

  The substrate 2 has a plate shape. Although the material of the board | substrate 2 should just be suitably selected from the metal which can be friction-welded, copper or copper alloy is used in this embodiment. Thermal conductivity can be improved by making the board | substrate 2 into copper or a copper alloy.

  The pin-shaped fin 3 has a cylindrical shape. A plurality of pin-like fins 3 are erected on the surface 2 a of the substrate 2 at equal intervals. The material of the pin-shaped fin 3 may be appropriately selected from metals capable of friction welding, but in the present embodiment, aluminum or aluminum alloy is used. By forming the pin-shaped fins 3 from aluminum or an aluminum alloy, it is possible to reduce the weight and reduce the material cost. The planar cross section of the pin-shaped fin 3 has a circular shape in the present embodiment, but may have another shape such as an ellipse or a polygon.

  As shown in FIG. 1B, a fillet 4 is formed at the joint between the substrate 2 and the pin-like fin 3. The fillet 4 is a portion formed on the outer periphery of the tip of the pin-shaped fin 3 by softening the tip side of the pin-shaped fin 3 and protruding the base material by the friction welding process. The entire lower surface of the fillet 4 is bonded (attached) to the surface 2 a of the substrate 2. The fillet 4 has a ratio of the minimum diameter to the maximum diameter of 0.75 to 0.99.

  Next, a method for manufacturing a heat sink according to the present embodiment will be described. In the heat sink manufacturing method, a preparation process, a friction welding process, and a removal process are performed.

  As shown in FIG. 2A, the preparation step is a step of heating the substrate 2 and arranging the substrate 2 on the first jig 10 and the pin-shaped fins 3 on the second jig 20. The substrate 2 is heated by, for example, a sheath heater. In this embodiment, the heating temperature is set to 360 to 500 ° C, preferably 400 to 500 ° C. The heating temperature is appropriately set according to the materials of the substrate 2 and the pin-like fins 3 to be joined. The heating temperature is appropriately set so that no joint defect occurs in the joint and the ratio of the minimum diameter to the maximum diameter of the fillet 4 formed after the friction welding is 0.75 to 0.99. That's fine.

  The first jig 10 can fix the substrate 2 and can reciprocate in the horizontal direction. The second jig 20 includes a plurality of holes 21 extending in the height direction. The hole 21 is a cylindrical hollow part. The inner diameter of the hole 21 is substantially equal to the outer diameter of the pin-like fin 3. When the pin-like fin 3 is inserted into the hole 21, the tip end side of the pin-like fin 3 is exposed. In the preparation step, the heated substrate 2 is disposed on the first jig 10, and the plurality of pin-like fins 3 are disposed in the hole 21 of the second jig 20. Since the friction welding process is performed quickly after heating the substrate 2, the heating temperature of the substrate 2 in the preparation process and the temperature of the substrate 2 in the friction welding process are substantially equal.

  The friction welding process is a process of joining the heated substrate 2 and the pin-shaped fins 3 by friction welding. In the friction welding process, a butt process, a friction process, and a pressure welding process are performed. In the butting step, as shown in FIG. 2B, the first jig 10 and the second jig 20 are relatively moved so that the end surface 3 a of the pin-like fin 3 is butted against the surface 2 a of the substrate 2.

  As shown in FIG. 3A, in the friction process, the first jig 10 is reciprocated with respect to the second jig 20 to generate frictional heat at the abutting portion. In the friction process, in this embodiment, the linearly reciprocating motion is performed in the left-right direction of FIG. In the friction process, the surface 2a of the substrate 2 and the end surface 3a of the pin-like fin 3 are rubbed together to generate frictional heat, and the softened base material is discharged to the outside.

  The conditions for the friction process may be set as appropriate. For example, the frequency is 100 to 260 Hz, the amplitude is 1.0 to 2.0 mm (preferably 1.2 to 1.8 mm), and the friction load is 0.5 to 2. Set to 0 MPa. Moreover, the time of a friction process is set to about 1-3 seconds. When the friction process is completed, the process immediately proceeds to the pressure contact process.

  In the pressure welding process, the first jig 10 and the second jig 20 are pressed in directions close to each other without reciprocating. The conditions for the pressure contact process may be set as appropriate. For example, the upset load is set to 80 to 120 MPa, and the upset time is set to 5 to 12 seconds.

  After frictional heat is generated at the joint (abutting portion between the surface 2a of the substrate 2 and the end surface 3a of the pin-like fin 3) by the friction process, the reciprocation is stopped and an upset load is applied by the pressure welding process. And the pin-shaped fin 3 are joined. In the friction process, the substrate 2 and the pin-like fins 3 are rubbed together, and the softened base material is pushed out of the joint, thereby forming the fillet 4.

  The take-out step is a step of taking out the heat sink 1 from the second jig 20 after retracting the first jig 10 as shown in FIG.

  Next, the formation process of the fillet 4 in the friction welding process according to the present embodiment will be described. FIGS. 4A to 4D are schematic side sectional views showing stepwise the bonding state between the substrate and the pin-like fins in the heat sink manufacturing method of the present embodiment. (A)-(d) of FIG. 5 is a schematic plan view corresponding to (a)-(d) of FIG.

  First, as shown in FIG. 13, the second region Y in the conventional friction welding process is cooled by being exposed to the atmosphere in order to repeat contact or non-contact with the pin-shaped fin 120 by the reciprocating motion of the pin-shaped fin 120. On the other hand, as shown in FIG. 4A, in the friction welding process of the present embodiment, even if a region where the substrate 2 and the pin-like fin 3 are not in contact with each other is formed, the substrate 2 is heated in advance. Therefore, the temperature drop in the region can be suppressed. As a result, as shown in FIGS. 4B to 4D, the lower surface 4a of the fillet 4 and the surface 2a of the substrate 2 are reliably bonded (attached), so that the bonding strength can be increased. The occurrence of bonding defects can be prevented.

  On the other hand, the area (heat generating part Z1) indicated by hatching in FIGS. 5A to 5D shows an area where frictional heat is generated step by step as the friction process proceeds. As shown in FIG. 5A, since the substrate 2 is preheated in this embodiment, the frictional heat between the region where the substrate 2 and the pin-like fin 3 are always in contact with the region where the substrate 2 is not in contact is shown. Imbalance can be reduced. Thereby, in the initial stage of a friction process, since the front-end | tip of the pin-shaped fin 3 is softened more than before, the heat generating part Z1 exhibits a circular shape or a shape close to a circular shape. As shown in FIGS. 5B to 5D, the heat generating portion Z1 has a length in the direction orthogonal to the length direction in the amplitude direction (reciprocating direction) (direction orthogonal to the amplitude direction) when the friction process proceeds. The dimensions gradually increase at a substantially constant rate. That is, when the friction process proceeds, the heat generating portion Z1 becomes substantially similar to the initial state of FIG.

  Since the shape of the fillet 4 is affected by frictional heat, the shape of the fillet 4 increases substantially in a similar manner with the deformation of the shape of the heat generating portion Z1. Thereby, the fillet 4 can make the difference of the length dimension of an amplitude direction and the length dimension of an orthogonal direction smaller than before. Therefore, according to the friction welding process of this embodiment, the dispersion | variation in the joint strength of the amplitude direction and orthogonal direction of a junction part can be suppressed. That is, the substrate 2 and the pin-like fins 3 can be joined with a good balance.

  In addition, by heating the substrate 2 in advance, the pin-like fins 3 can be softened faster than before in the friction process, so that the time for the friction process can be shortened.

<Tensile test>
Next, examples of the present invention will be described. In this example, the first test body 1A and the second test body 1B shown in FIG. 6A were formed in accordance with a plurality of heating temperatures, which will be described later, respectively, and a tensile test was performed. The first test body 1 </ b> A and the second test body 1 </ b> B have the same shape, and each includes a substrate 2 and a plurality of pin-shaped fins 3. Fillets 4 are respectively formed at the joints between the substrate 2 and the pin-like fins 3. The plurality of pin-like fins 3 are arranged in a line along the opposing pieces of the substrate 2.

  The substrate 2 was set to 95 mm long, 95 mm wide, and 5 mm thick. The pin-shaped fin 3 was set to an outer diameter of 2.4 mm and a length of 60 mm. Copper C1020-1 / 2H (JIS) was used as the material for the substrate 2 of the first specimen 1A, and aluminum alloy A1070 (JIS) was used as the material for the pin-like fins 3. On the other hand, the material of the substrate 2 of the second specimen 1B was copper C1020-1 / 2H (JIS), and the material of the pin-like fin 3 was aluminum alloy A4043 (JIS). The joining conditions in the manufacturing method of the example are as shown in FIG.

Copper C1020-1 / 2H (JIS) is oxygen-free copper formed of Cu; 99.96% or more. 1 / 2H is work-hardened so that the tensile strength is intermediate between tempered 1 / 4H and 3 / 4H.
Aluminum alloy A1070 (JIS) is Si; 0.20% or less, Fe; 0.25% or less, Cu; 0.04% or less, Mn; 0.03% or less, Mg; 0.03% or less, Zn; 0.04% or less, V; 0.05% or less, Ti; 0.03% or less, others; 0.03% or less, Al; 99.70% or more.
Aluminum alloy A4043 (JIS) is Si: 4.5-6.0% or less, Fe: 0.8% or less, Cu: 0.30% or less, Mn: 0.05% or less, Mg: 0.05% Hereinafter, Zn: 0.10% or less, Ti: 0.20 or less, others: 0.15% or less, Al: the balance.

  Although the manufacturing method of the example is almost the same as that of the above-described embodiment, as shown in FIG. 7, in the friction welding process of the example, the heating temperature of the substrate 2 is 25 ° C., 250 ° C., 300 ° C., 350 ° C., 400 ° C, 450 ° C, 475 ° C, and 500 ° C were set in 8 stages, and the first test body 1A and the second test body 1B were formed for each heating temperature. Since the melting point of aluminum is about 660 ° C., if the heating temperature is set higher than 500 ° C., the pin-shaped fins 3 may be melted. Therefore, the upper limit of the heating temperature of the substrate 2 was set to 500 ° C. In the manufacturing method of the example, the M direction shown in FIG. 6A is set as the amplitude direction (reciprocating direction). The N direction is an orthogonal direction orthogonal to the M direction.

  In the tensile test, as shown in FIG. 6B, a part of the substrate 2 was cut, and a test piece composed of the substrate 2 and one pin-like fin 3 was collected. As shown in FIG. 6C, the maximum diameter φmax and the minimum diameter φmin of the fillet 4 were measured with a caliper.

  FIG. 8 is a graph showing the relationship between the substrate heating temperature and the bonding strength in the example. A result R1 shown in FIG. 8 indicates the result of the bonding strength of the first specimen 1A. On the other hand, the result R2 shows the result of the bonding strength of the second specimen 1B. As shown in the result R1, it was found that in the first specimen 1A, a bonding strength of at least 50 MPa or more was obtained when the heating temperature of the substrate 2 was 400 ° C. or higher and 500 ° C. or lower. Further, as shown in the result R2, in the second specimen 1B, when the substrate 2 heating temperature is 350 ° C., a bonding strength exceeding 30 MPa is obtained, and when it is 400 ° C. or more and 500 ° C. or less, the bonding strength is at least 90 MPa or more. It was found that strength was obtained.

  8 indicates the base material strength (tensile strength) of the pin-shaped fin 3 made of the aluminum alloy A1070, and the dotted line S2 indicates the base material strength (tensile strength) of the pin-shaped fin 3 made of the aluminum alloy A4043. . In the result R1 (aluminum alloy A1070), it was found that the bonding strength reached 50% or more of the base material strength when the heating temperature of the substrate 2 was 400 ° C. or higher and 500 ° C. or lower. In other words, it was found that when the heating temperature of the substrate 2 is less than 400 ° C., the bonding strength is less than 50% of the base material strength.

  In the result R2 (aluminum alloy A4043), it was found that the bonding strength reached 80% or more of the base material strength when the heating temperature of the substrate 2 was 400 ° C. or higher and 500 ° C. or lower. In other words, it was found that when the heating temperature of the substrate 2 is less than 400 ° C., the bonding strength is less than 80% of the base material strength.

  FIG. 9 is a cross-sectional microstructure diagram of the joint portion of the example. As shown in the left column of FIG. 9, it was found that when the heating temperature of the substrate 2 is 350 ° C., both sides in the width direction of the fillet 4 are not bonded to the substrate 2 and bonding defects Q and Q are formed. On the other hand, as shown in the right column of FIG. 9, when the heating temperature was 475 ° C., the surface 2a of the substrate 2 and the lower surface of the fillet 4 were bonded together, and no bonding defect was found in the bonded portion. When the heating temperature was 475 ° C., an extremely thin copper / aluminum reaction layer of about 1 μm could be confirmed at the bonding interface, and it was found that both were metallicly bonded.

  Considering FIGS. 8 and 9, it was found that when the heating temperature of the substrate 2 is set to 400 to 500 ° C., there is no bonding defect in the bonding portion and sufficient bonding strength can be obtained.

  FIG. 10 is a graph showing the relationship between the substrate heating temperature and the fillet diameter ratio in the example. In the graph, the result is shown by plot points having the same shape (diamond) regardless of the material of the pin-shaped fin 3. The fillet diameter ratio is a value of the minimum diameter φmin with respect to the maximum diameter φmax of the fillet 4 as shown in FIG. As shown in FIG. 10, it was found that the fillet diameter ratio approaches 1.0 as the heating temperature of the substrate 2 increases. Moreover, it turned out that the heating temperature of the board | substrate 2 from which a fillet diameter ratio will be 0.75 or more is 400 degreeC.

  FIG. 11 is a graph showing the relationship between the fillet diameter ratio of the example and the joining efficiency. In the graph, the result is shown by plot points having the same shape (diamond) regardless of the material of the pin-shaped fin 3. The joining efficiency is a value obtained by dividing the joining strength (see FIG. 8) obtained in the tensile test by the base material strength of the pin-shaped fins 3 of each material. The joining strength and the base material strength are obtained by dividing the breaking load in the tensile test by the initial cross-sectional area of the base material of the pin-shaped fin 3. For this reason, joining efficiency may exceed 100%.

  As shown in FIG. 11, it has been found that when the fillet diameter ratio is 0.75 or more, the joining efficiency is 40% or more. That is, it has been found that when the difference between the maximum diameter φmax and the minimum diameter φmin of the fillet 4 is small, the joining efficiency is also increased. On the other hand, it was found that when the fillet diameter ratio is less than 0.75, the joining efficiency is less than 40% and the joining efficiency is lowered. Considering the results of FIGS. 10 and 11, it was found that when the heating temperature was 400 ° C. or higher, the fillet diameter ratio was 0.75 or higher and sufficient bonding strength was obtained. That is, it was found that when the heating temperature was 400 ° C. or higher, the bonding was performed in a well-balanced and strong manner.

<Pin-shaped fin joint rate test>
Further, in this example, the second test body 1B (aluminum alloy A4043) shown in FIG. 6A was formed in accordance with a plurality of amplitudes described later, and a pin-shaped fin joint ratio test was performed. In the pin-shaped fin bonding rate test, the number of pin-shaped fins 3 formed on the second test body 1B (40 pin-shaped fins 3 in total) are bonded to the substrate 2 without dropping or breaking. The percentage was calculated.

  In the pin-shaped fin bonding rate test, the amplitude of the friction welding process was set to 0.8 mm, 1.0 mm, 1.2 mm, 1.6 mm, and 1.8 mm, and test specimens were formed with the respective amplitudes. The heating temperature of the substrate 2 was uniformly set to 350 ° C. As shown in FIG. 12, it was found that the pin-like fin joint ratio was 70% or more when the amplitude was 1.2 mm or more. Moreover, it turned out that a pin-shaped fin joint rate will be less than 70% as an amplitude is less than 1.2 mm. Therefore, it was found that the amplitude in the friction welding process is preferably set to 1.2 to 1.8 mm.

1 heat sink 2 substrate 3 pin-shaped fin 4 fillet

Claims (3)

A method of manufacturing a heat sink comprising a copper or copper alloy substrate and a plurality of aluminum or aluminum alloy pin-like fins erected on the substrate,
The plurality of holes of the second jig are arranged so that the substrate heated to 400 to 500 ° C. is disposed on the first jig and the tips of the plurality of pin-shaped fins are exposed from the second jig. A preparation step of arranging a plurality of the pin-shaped fins in
The end surfaces of the plurality of pin-shaped fins are butted against the surface of the heated substrate, and the substrate and the pin-shaped fins are linearly moved by relatively moving the first jig and the second jig. A method of manufacturing a heat sink, comprising: a friction welding process for reciprocating and performing friction welding.   2. The method of manufacturing a heat sink according to claim 1, wherein in the friction welding step, the amplitude is set to 1.2 to 1.8 mm. A heat sink have a pin-shaped fins made of a plurality of aluminum or aluminum alloy substrate made of copper or a copper alloy is erected on the substrate,
The fillet of the same material as the pin-shaped fin formed at the joint between the substrate and the plurality of pin-shaped fins has a ratio of the minimum diameter to the maximum diameter of 0.75 to 0.99 , A heat sink, characterized in that an extremely thin copper / aluminum reaction layer exists at the joint interface of the joint .

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