JPH09298259A - Heat sink and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To approximately uniformly radiate the heat from all radiation fins, by forming the Al fins on the surface of an Al plate composite with a Cu plate to form a composite board, and forming a metal bond at the interface of the composite board. SOLUTION: The heat sink is a pin fin type having many pin-like fins 2 on a board 1 which is a composite board of an Al and Cu plates 1a, 1b with Al fins disposed on the Al plate. The Al and Cu plates of the board 1 are metal-bonded. The Cu plate is used to conduct the heat produced in an LSI mounted on the surface of this plate to the entire board. The Al fins on the Al plate are to efficiently radiate the heat from the Cu plate to the Al plate.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a large scale integrated circuit (L).
The present invention relates to a heat sink attached to an electronic component that generates heat such as SI) and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent electronic devices, LSIs and the like are often used, and the amount of heat generated increases due to the miniaturization and higher density of packaging, and the heat dissipation method becomes a problem. That is, since the LSI generates a large amount of heat during use, how to dissipate this heat is the key to operating the LSI normally and at high speed. To dissipate the heat,
A heat sink is attached to the LSI package.

FIG. 2 is a view showing a state in which a channel fin type heat sink, which is a typical heat sink, is attached to a ceramic pin grid array type LSI package. A channel fin type heat sink 4 is attached to the package 3 via a heat transfer substrate 9, the LSI 11 is bonded under the heat transfer substrate 9, and a frame-shaped ceramics plate 5 or 6 and a metal lid 7 are used. It is housed in the constructed airtight space 8. The heat transfer substrate 9 and the ceramic plate 5, and the lid 7 and the ceramic plate 6 are joined by brazing or the like. The large number of pins 10 inserted into the ceramics plate 6 and the LSI 11 are electrically connected to each other via the wires 13 and the conduction circuit printed on the surface 12 of the ceramics plate 5.

As the material of the heat transfer substrate 9, a material having a large thermal conductivity and a small difference in linear expansion coefficient from the LSI 11 is selected. For example, a material obtained by impregnating a porous tungsten plate with copper is used. Channel fins 24 on the heat transfer board 9
The heat generated by the LSI is transferred to the channel fins 24 through the heat transfer substrate 9 and is dissipated to the outside. However, in most of the LSI packages currently used, the size of the heat transfer substrate 9 is 50% or less of the size of the package as shown in FIG. Some are. Generally, the size of the heat sink and the size of the package are almost the same. Therefore, the heat emitted from the package is transferred only to the central portion of the substrate of the heat sink, and is diffused to the entire radiation fin by heat conduction of the substrate of the heat sink. In order to improve the heat conduction in the horizontal direction of the substrate, it is sufficient to increase the thickness of the substrate, but at the same time, there is a limit in that the height of the fin is decreased.

In order to improve the performance of the heat sink, it is desirable to conduct heat evenly throughout the substrate. However, as described above, the heat generated in the LSI package is transferred to the radiating fins through the heat transfer substrate, and therefore is most transferred to the central portion of the heat sink. As described above, in the conventional heat sink, all the radiation fins do not function effectively.

Japanese Unexamined Patent Publication No. 2-291154 discloses a ceramic package with a heat sink for solving the above problems. This heat sink is a pin fin type having a large number of pin-shaped projections on the substrate. The feature is that the diameter of the pin in the central part is the maximum and the diameter is gradually reduced toward the periphery. With such a structure, the flow of air becomes faster under forced air cooling because the fin interval in the central portion is narrow. Furthermore, the cross-sectional area of the pin is increased, the heat conduction to the tip of the pin is improved, and the heat dissipation efficiency of the center of the heat sink is improved.
The overall thermal resistance is low.

However, in such a structure, since the fin interval in the central part is small, the ventilation resistance in that part is large, and when actually used, almost no air flows, and on the contrary the heat dissipation efficiency in the central part is reduced. I had done it. It needed a powerful fan to prevent it, and it was not practical.

[0008]

As described above, in the conventional heat sink, the heat generated from the LSI is not uniformly transmitted to all the fins, so that the heat sink cannot be efficiently radiated.

The present invention provides a heat sink that can dissipate heat substantially uniformly from all the heat dissipating fins without losing the superiority of formability and heat dissipating property of a conventional heat sink of aluminum or aluminum alloy alone, and a manufacturing method thereof. It is intended to be provided.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted experiments and studies to develop a heat sink that uses aluminum, which has been conventionally used as a heat sink, and efficiently dissipates heat over all fins. The following findings were obtained.

1) In order to transfer the heat to be dissipated to all the fins, it is necessary to transfer the heat from the heat source to the entire substrate. For that purpose, a metal plate having good thermal conductivity is coupled to the substrate. It is better to use a composite plate.

2) A copper plate is suitable as the metal plate, and the bonding method must be metal bonding.

3) As the composite substrate, it is preferable to use a clad plate of aluminum and copper, which is metal-bonded at the time of manufacturing.

The present invention has been made on the basis of such findings, and the gist thereof is that "a substrate is a composite plate made of a copper plate and an aluminum plate, and a radiation fin made of aluminum is formed on the surface of the aluminum plate of the composite plate. Is provided and the interface of the composite plate is metal-bonded, and a method for manufacturing the heat sink characterized by forming a radiation fin on the aluminum portion of the aluminum and copper clad plate ". is there.

In the present invention, "aluminum" means pure aluminum and an aluminum alloy, and "copper" means pure copper and a copper alloy.

[0016]

FIG. 1 is a view showing an example of a heat sink according to the present invention. This heat sink is a pin fin type in which a large number of pin-shaped fins 2 are provided on a substrate 1. The substrate 1 is a composite plate composed of an aluminum plate 1a and a copper plate 1b, aluminum fins are provided on the aluminum plate side, and the aluminum plate and the copper plate forming the substrate 1 are metal-bonded.

The reason why the aluminum plate and the copper plate are used as the substrate and the aluminum fin is provided on the surface of the aluminum plate is as follows.

The copper plate is used because the LSI is attached to the surface of the copper plate and the heat generated in the LSI is conducted to the entire substrate. Therefore, copper having good heat conductivity is used as the material of the heat conductor.

The aluminum fin is provided on the aluminum plate side in order to efficiently dissipate the heat conducted from the copper plate to the aluminum plate through the aluminum fin. Aluminum is used as the material for the fins because it has good heat dissipation and moldability.

In this case, in order to improve heat conduction from the aluminum plate to the fins, it is preferable that they are integrated. Such a heat sink in which the substrate and the fins are integrated can be manufactured by a forming process such as forging described later.

Next, the reason for metal-bonding an aluminum plate having aluminum fins to a copper plate will be described.

The method of joining the aluminum plate and the copper plate is extremely important because the thermal resistance generated at the joining interface poses a problem. If there is a gap at the joint interface, the air trapped in it becomes a heat insulating material, and the thermal resistance increases significantly. In the method of mechanically joining the copper plate to the aluminum finned plate, it is difficult to eliminate the gaps at the joint portion, and the working process becomes complicated, resulting in an increase in manufacturing cost. Further, the thermal resistance cannot be reduced even if the heat transfer substrate and the fin substrate are joined together by using an adhesive or the like as used in the past. However, if copper and aluminum are metallically bonded, the thermal resistance at the boundary can be minimized. Metal joining refers to metallurgical joining such as diffusion joining and welding.

It is very difficult to separately manufacture an aluminum plate having fins and a copper plate and then metal-bond them, and if possible, it requires a lot of labor and is not practical.

A preferred method for producing a composite plate in which an aluminum plate and a copper plate are metal-bonded is a method in which the aluminum plate and the copper plate are separately heated, and then the both plates are stacked and rolled. The clad plate manufactured by such a method is pressure-bonded at a high temperature during rolling and metallurgically bonded.

After the aluminum and copper clad plate is manufactured as described above, it is preferable to fin the aluminum portion.

The shape of the fin is not particularly limited, but a pin type fin composed of a plurality of pins or a channel type fin composed of a plurality of parallel flat plate rows is preferable.

As the processing method for forming the fin, any method such as mechanical processing and plastic processing may be used.

[0028]

【Example】

(Example 1) Aluminum alloy (JIS A2017)
40mm wide, 40mm long, 16mm thick
(Aluminum alloy plate thickness: 15 mm, copper plate thickness: 1 mm)
A heat sink for a channel-type fin having the following dimensions was manufactured using the clad plate.

Substrate: width 40 mm, length: 40 mm, thickness: 2 mm (thickness: aluminum part 1 mm, copper part 1 m)
m) Fins: Height: 14 mm, thickness 1 mm, fin spacing 2 m
m 13 fins (plates are arranged in parallel on the substrate) FIG. 3 is a diagram showing the manufactured heat sink, (a) is a plan view and (b) is a side view. The unit of the numbers in the figure is mm
It is.

FIG. 4 is a diagram for explaining a method of manufacturing the heat sink. The material 13 is the clad plate, and a disc-shaped grindstone 15 having a thickness of 2 mm is rotated and advanced from one end thereof to form a groove 16 having a width of 2 mm and a depth of 14 mm.
Twelve pieces were formed at mm intervals to obtain fins as shown in FIG.

As a comparative example, a heat sink made of a single aluminum alloy having the same dimensions as the heat sink was also manufactured.

Using these heat sinks, the heat radiation performance was measured in the following manner.

The center of the board of each heat sink, 30 mm ×
A range of 30 mm was heated by an electric heater, and cooling air was blown from the upper part of the fin while changing the speed in a range of 0.5 to 5.0 m / sec. The flow velocity of the cooling air is based on the assumption of normal computer forced cooling.

60 minutes after the start of energization and air blowing, the temperature Tj of the central portion of the back surface of the substrate and the temperature of the cooling air before the air blowing are maintained with the heat supply to the fins and the heat radiation from the fins being stable. Was measured, and the thermal resistance R was calculated by the following formula. The heat generation amount Q of the heater was 10 w.

R = (Tj-Ta) / Q FIG. 7 is a diagram showing the relationship between the obtained thermal resistance R and the flow velocity of the cooling air. As is clear from the figure, the heat resistance of the heat sink of the present invention is smaller than the heat resistance of the heat sink made of a single aluminum alloy regardless of the flow velocity, and the heat dissipation performance is excellent.

Example 2 A clad plate having a width of 60 mm, a length of 60 mm and a thickness of 6 mm (pure aluminum plate thickness: 3.5 mm, copper plate thickness: 2.5 mm) made of pure aluminum and copper was used, and the following dimensions were used. A pin fin type heat sink was manufactured.

Substrate: width 60 mm, length 60 mm, thickness 3 mm (thickness: pure aluminum part 1 mm, copper part 2 mm) fin: height: 15 mm, pin diameter: 1 mm, pin pitch: 4 mm number of pins: 196 Therefore, a heat sink made of pure aluminum alone with the same dimensions as above was also manufactured.

FIG. 5 is a view showing the manufactured heat sink, (a) is a plan view and (b) is a side view. The unit of the numbers in the figure is mm.

FIG. 6 is a diagram for explaining a method of manufacturing the heat sink. A die 18 having a through hole corresponding to the number of pins to be formed by facing the punch 17 movable up and down by a method of forming a pin by a forging machine is a die table 22.
The die is held by the die holder 19. As shown in (a) of the same figure, the clad plate 21 of the material is placed on the die with the aluminum surface facing the die side, and the punch 17 is lowered to push the aluminum into the through hole of the die as shown in (b). Forging into a pin shape. When the molding is completed, as shown in (c), the knockout pin 20 is pushed up from the back side of the die, and the pin is pulled out from the die hole to complete the heat sink 23.

Using these heat sinks, the heat dissipation performance was measured in the following manner.

Central part of substrate of each heat sink, 40 mm ×
A range of 40 mm is heated with an electric heater, and as in Example 1,
The cooling air was blown from the upper part of the fin by changing the speed in the range of 0.5 to 5.0 m / sec.

60 minutes after the start of energization and blowing, Tj and Ta were measured and the thermal resistance was determined by the same method as in Example 1.

FIG. 8 is a diagram showing the relationship between the obtained thermal resistance R and the flow velocity of the cooling air. As is clear from the figure, the heat resistance of the heat sink of the present invention is smaller than the heat resistance of the pure heat sink made of pure aluminum regardless of the flow velocity, and the heat dissipation performance is excellent.

[0044]

The heat sink of the present invention is excellent in heat dissipation performance, can sufficiently cope with an increase in heat generation due to high density mounting of LSI, and is extremely excellent in contributing to normal and high-speed operation of LSI. It is a thing.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a pin fin type heat sink of the present invention.

FIG. 2 is a schematic diagram of an LSI package.

FIG. 3 is a diagram showing a channel fin type heat sink used in an example.

FIG. 4 is a diagram for explaining a method of manufacturing a channel fin type heat sink.

FIG. 5 is a diagram showing a pin fin type heat sink used in Examples.

FIG. 6 is a diagram for explaining a method of manufacturing a pin fin type heat sink.

FIG. 7 is a diagram showing a relationship between a thermal resistance of a channel fin type heat sink and a cooling flow rate.

FIG. 8 is a diagram showing the relationship between the thermal resistance of a pin fin type heat sink and the cooling flow velocity.

[Brief description of reference numerals]

 1 substrate 1a aluminum 1b copper 2 pin fin 3 LSI package 15 grindstone 17 1 punch 18 die

Claims (2)

[Claims] 1. A substrate is a composite plate composed of a copper plate and an aluminum plate, and a radiation fin made of aluminum is provided on the surface of the aluminum plate of the composite plate, and the interface of the composite plate is metal-bonded. Characteristic heat sink. 2. A method for manufacturing a heat sink according to claim 1, wherein a heat radiation fin is formed on an aluminum portion of an aluminum / copper clad plate.