JPH10227585A - Heat spreader and cooler employing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cope with a case in which the heat generating density of a semi- conductor element and the like to be cooled is high, and various arrangement method by a method wherein a heat conductive metallic body is provided at a part, to which a part to be cooled is connected thermally, while the circumferential parts of the metallic body are constituted of a heat pipe structure. SOLUTION: A semi-conductor element 2 is positioned at the central part of a heat spreader 1 substantially and a heat conductive metallic body 101 is provided at the central part while a heat pipe cavity unit 100, constituting a heat pipe structure, is provided at the circumferential part of the metallic body 101. Fins 4 are attached to the opposite side of the heat spreader 1 and, further, heat conductive grease 3 is provided to reduce contact heat resistance between the fin unit 4 and the heat spreader 1. Accordingly, the heat of the semi-conductor element 2 is transferred to working liquid in the heat pipe cavity part 100 through the heat transfer metallic body 101 while the heat is dispersed by the heat conductive metallic body 101 and the heat absorbing part (evaporating unit) of the heat pipe cavity unit 100 is spread to a wide area. Accordingly, the generation of local boiling boundary is restrained and efficient heat transfer can be effected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat spreader suitable for cooling electric parts and the like that require cooling, and a cooler using the same.

[0002]

2. Description of the Related Art As a method for cooling semiconductor devices mounted on various electric devices such as personal computers and other devices, a method of cooling air in a device housing by attaching a fan to the device, and a method for cooling the device. A method of attaching a cooling body to a semiconductor element and the like are known.

When cooling by attaching a cooling element to a semiconductor element, the semiconductor element is generally small in size.
It is effective to disperse the heat to the heat transfer member once and dissipate the heat from the fins attached to the heat transfer member without directly attaching the radiation fin to the semiconductor element.

[0004] Specifically, a heat conductor is brought into contact with a semiconductor element, and fins are attached to the heat conductor. The heat generated by the semiconductor element to be cooled will generally travel to the heat conductor and dissipate therefrom via the fins. Here, as the heat transfer body, a material having excellent thermal conductivity such as an aluminum material or a copper material is usually used in many cases.

[0005] The heat transfer member attached to the semiconductor element is sometimes called a heat spreader in order to spread heat.
In order to spread the heat more efficiently, the heat spreader may have a heat pipe structure. in this case,
A heat pipe prepared separately may be embedded in the heat transfer body.

[0006] Depending on the position where the semiconductor element is mounted,
In many cases, the fins and the heat spreader are separated. Since it is desirable that the fin is provided near the outside of the device housing on which the semiconductor element is mounted, the heat spreader and the fin may be separated depending on the position of the semiconductor element to be cooled. In such a case, a method of connecting the heat spreader and the fins with a heat pipe is effective and has been put to practical use.

The transfer of heat by the heat pipe connecting the heat spreader and the fins or by the heat pipe forming the heat spreader is usually performed by the following operation. That is, on the heat absorption side of the heat pipe, a container (often called a container) that forms the heat pipe.
The working fluid evaporates due to the heat transmitted by conducting heat through the material, and the vapor moves to the heat radiation side of the heat pipe.
On the heat radiation side, the working fluid vapor is cooled and returns to the liquid state again. Then, the working fluid that has returned to the liquid phase moves to the heat absorbing side again. Heat is transferred by such phase transformation and movement of the working fluid. The working fluid may be in a vapor state in addition to the liquid state, but the term “working fluid” is conventionally used here.

[0008] The working fluid that has been brought into the liquid phase state by the phase transformation is:
It returns to the heat absorbing side by gravity or capillary action. In the case of the gravity type, the heat absorption side may be disposed below the heat radiation side. In the case of an electric device such as a personal computer, it is often difficult to provide a height difference between the heat radiating side and the heat absorbing side of the heat pipe due to the internal space. In such a case,
A heat pipe with a groove or wick provided inside is applied. Of course, in terms of performance, it is needless to say that even in a heat pipe utilizing such a capillary action, it is desirable to arrange the heat radiation side above the heat absorption side.

A typical external shape of the heat pipe is a circular pipe shape, but a flat plate-shaped plate is also often used. The selection of the shape of the heat pipe may be appropriately determined in consideration of the state to which the heat pipe is applied, required characteristics, and the like. Also, the material of the container constituting the heat pipe may be selected in accordance with the use or the like, and for example, a copper material, a stainless steel material, an aluminum material or the like can be applied.

FIG. 3 is an explanatory view showing an embodiment of a conventional cooler. The semiconductor element 2 to be cooled is mounted on a printed circuit board 5. A heat spreader 10 having a heat pipe structure is arranged on the upper surface side of the semiconductor element 2. The heat of the semiconductor element 2 transmitted to the heat spreader 10 is radiated from the fin portion 4.

In order to thermally connect a component to be cooled such as the semiconductor element 2 to the heat spreader 10, the component to be cooled may be brought into contact with the component to be cooled or may be brought into contact with a heat transfer material. Here, the heat transfer grease 3 is interposed between the heat spreader 10 and the fin portion 4 in order to reduce the contact thermal resistance.

The conventional example shown in FIG. 3 uses a plate-like heat pipe as the heat spreader 10. Conventionally, such a heat spreader 10 has, for example, an inner space formed by joining two upper and lower metal plates serving as a container constituting a heat pipe, and a working fluid (usually water or alternative Freon) is formed in the inner space. Used).
The inside of the heat pipe in which the working fluid is sealed is vacuum degassed so that the working fluid is likely to undergo a phase transformation of evaporation and condensation.

[0013]

The above-described heat spreader 10 having the heat pipe structure or the heat spreader in which the heat pipe is embedded has a structure in which the heat absorbing portion of the heat pipe is located at a position of a semiconductor element to be cooled. Had become.

However, semiconductor elements to be cooled are generally small in size, and in recent years, their heat density is often high. In the case of such a component to be cooled, the heat absorption portion of the heat pipe to which the component is thermally connected tends to reach the boiling limit because the heat flow velocity is too high. In this case, the efficiency of heat transport is impaired.

Further, depending on the arrangement of the heat spreader and the condition of use of the electric equipment or the like on which the heat spreader is mounted, the heat absorbing portion where the component to be cooled is located may be located above the heat radiating portion. In such a case, the heat transfer function of the heat pipe constituting the heat spreader is likely to be reduced. That is, the heat pipe is set to the top heat mode.

Under such circumstances, there has been a demand for a heat spreader which can easily cope with a case where the heat generation density of a semiconductor element or the like to be cooled is high or various arrangement methods.

[0017]

The heat spreader proposed in the present invention is a heat spreader having a heat transfer metal body at a portion to which a component to be cooled is thermally connected, and a heat pipe structure around the heat transfer metal body. is there. A cooler using such a heat spreader is also proposed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view showing the structure of a heat spreader according to the present invention and a cooler using the same. The semiconductor element 2 mounted on the printed circuit board 5 is an object to be cooled (a component to be cooled). The semiconductor element 2 is located substantially at the center of the heat spreader 1. A heat transfer metal body 101 is provided at the center portion, and a heat pipe cavity portion 100 forming a heat pipe structure is provided at a peripheral portion thereof. In this figure, the hydraulic fluid is omitted.

The fin portion 4 is attached to the heat spreader 1 on the side opposite to the surface on which the semiconductor element 2 is provided.
The heat transfer grease 3 is provided to reduce the contact heat resistance between the fin portion 4 and the heat spreader 1.

FIG. 2 is an explanatory diagram simply showing a method of manufacturing the heat spreader 1 of FIG. The heat spreader is assembled by joining the upper plate 12 and the lower box 13. The joining method is not particularly limited, but a welding method such as MIG welding, TIG welding, resistance welding, or a brazing method can be suitably applied. When brazing, if the material of the upper plate 12 and the lower box 13 is an Al material, it is convenient to use a brazing sheet. When the material of the upper plate 12 and the lower box 13 is Cu, Ag
A brazing material or the like may be used.

After these are joined, the heat pipe cavity 100 shown in FIG. 1 is formed by the recess 14 and a part of the upper plate 12. Note that the names of the upper plate 12 and the lower box 13 are merely names for convenience of explanation. There is no point in being above or below. Reference numeral 11 denotes a block corresponding to the heat transfer metal body 101 in FIG.

It is desirable to form a groove on the inner surface of the heat pipe cavity 100 for the purpose of increasing thermal efficiency. Therefore, it is preferable to form a groove in the inner wall of the lower box 13. The grooves can be formed by, for example, grooving or threading, or by separately preparing a sintered body and joining them.

The material of the upper plate 12 and the lower box 13 forming the heat spreader 1 is desirably copper or aluminum having high thermal conductivity. The material may be selected in consideration of required heat characteristics, strength characteristics, and the like. From the viewpoint of thermal conductivity, pure copper (tough pitch copper, oxygen-free copper, etc.), pure Al-based material, and the like are desirable.

The heat pipe cavity 100 contains a predetermined amount of hydraulic fluid. Of course, degassing is also performed to function as a heat pipe. The working fluid may be a normal working fluid such as water or CFC substitute.

When the heat spreader 1 of the present invention is used, generally, the heat of the semiconductor element 2 is transmitted to the working fluid in the heat pipe cavity 100 via the conductive metal body 101. Of course, some heat is transmitted to the fin portion 4 via the conductive metal body 101. Since the heat is dispersed by the conductive metal body 101, the heat absorbing portion (evaporating portion) of the heat pipe cavity 100 also spreads over a wide area. For this reason, generation | occurrence | production of a local boiling limit is suppressed, and efficient heat transfer will be performed.

FIG. 4 shows a case where a block 15 as shown in FIG. 4 is arranged in place of the block 11 in FIG. When the surface area is increased as in the block 15, the heat transferred from the semiconductor element 2 to the block 15 is more efficiently transferred to the working fluid. Therefore, the cooling performance is improved.

In the above-described embodiment, an example was shown in which one semiconductor element 2 was located substantially at the center of the heat spreader 1. However, when there are a plurality of parts to be cooled, a plurality of heat transfer elements are provided corresponding to the positions. A metal body will be provided and a heat pipe cavity will be provided around it.

[0028]

The heat spreader according to the present invention can easily cope with a case where a component to be cooled has a high heat generation density and various arrangement methods as a cooler for cooling the component. A cooler using this heat spreader can achieve efficient cooling.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of a heat spreader of the present invention and a cooler using the same.

FIG. 2 is an explanatory view showing the assembly of the heat spreader of the present invention.

FIG. 3 is an explanatory diagram showing an example of a cooler using a conventional heat spreader.

FIG. 4 is an explanatory view showing assembly of another example of the heat spreader of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat spreader 2 Semiconductor element 3 Heat transfer grease 4 Fin part 5 Printed circuit board 10 Heat spreader 11 Block 12 Upper plate 13 Lower box 14 Depression 15 Block 100 Heat pipe cavity 101 Heat transfer metal body

Claims (2)

[Claims] 1. A heat spreader in which a part to be cooled is thermally connected to a heat transfer metal body and a peripheral part thereof has a heat pipe structure. 2. A cooler using the heat spreader according to claim 1.