Heat exchange – Intermediate fluent heat exchange material receiving and... – Liquid fluent heat exchange material
Reexamination Certificate
2000-04-06
2001-08-07
Lazarus, Ira S. (Department: 3743)
Heat exchange
Intermediate fluent heat exchange material receiving and...
Liquid fluent heat exchange material
C165S104330, C174S015200, C361S704000, C257S715000
Reexamination Certificate
active
06269866
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a cooling device used for preventing temperature from rising in electric parts such as small-sized computers and the like, which generate heat. In particular, the invention relates to a cooling device provided with a heat pipe.
2. Description of the Related Art
It is known to cool semiconductor devices and the like, mounted on various kinds of electrical equipment such as personal computers and other equipment, by air in a casing of the equipment, and by attaching a cooling body to a semiconductor device.
In the case of cooling the semiconductor device with a cooling body attached to the semiconductor device, there is often employed a manner of dispersing heat to a heat transferring body without directly attaching a radiating fin to the semiconductor device and radiating the heat through the fin directly attached to the heat transferring body because of the semiconductor device is generally small. The heat generated by the semiconductor device to be cooled is generally transmitted to the heat transferring body and radiated through the fins. The heat transferring body is frequently made of the material which has superior heat conductivity such as aluminum material and copper material.
The heat transferring body attached to the semiconductor device may be referred to as the heat spreader in view of a heat spreading. There is shown in
FIG. 29
an example of the heat spreader using metal as a conventional heat transferring body. A semiconductor device
102
to be cooled is packaged on a printed circuit board
105
. On an upper surface of the semiconductor
102
is disposed a heat spreader
100
which is a heat transferring body made of metal. The heat transmitted to the heat spreader
100
is radiated from fins
40
.
In order to connect a body to be cooled, such as the semiconductor device
102
, to the heat spreader in a heat transferring manner, both are in direct contact with each other, or connected through a heat transferring medium
110
. For example, the heat transferring medium
110
is made of a heat transferring grease, thereby lowering the heat transferring resistance.
Moreover, the fins
40
may be attached to the heat spreader
100
in order to spread the heat more effectively. It is desired that the fins
40
be disposed in the vicinity of the outside of a casing of the equipment mounting the semiconductor device
102
. Accordingly, the heat spreader
100
and the fins
40
may be away from each other depending on the location of the semiconductor device
102
. In this case, the heat spreader
100
and the fins
40
can be connected through a heat pipe. The heat pipe transmits the heat as follows. The heat pipe receives, at an absorbing side thereof, the heat which is transmitted through the material of a container constituting the heat pipe, thereby causing the working fluid to be evaporated to allow the vapor to move to a heat radiation side of the heat pipe. The heat pipe cools the vapor of the working fluid at the heat radiation side thereof to return it to a liquid phase state again. Then the liquefied working fluid is moved to the heat absorbing side again. In this way, the circulation of the working fluid subjected to the phase change causes the heat to be transferred.
During the circulation of the working fluid, the vapor is moved due to gas diffusion, and then the liquid is moved due to gravity and the capillary phenomenon. Wicks may be employed in order to utilize the capillary phenomenon. In a case where the heat is transmitted through a heat transferring solid body such as metal, the transmission of the heat is caused due to the temperature difference. Accordingly, the larger the temperature difference, the larger the quantity of the transmitted heat, whereas in the case of the heat pipe, the larger the vaporization latent heat of the working liquid or the larger the circulation rate of the working fluid, the larger the quantity of transmitted heat.
As a result, the heat pipe is capable of transmitting plenty of heat even if the temperature difference is small, provided that the temperature of the heat absorbing side is higher than the vaporization temperature of the working fluid and that the temperature of the heat radiation side is lower than the vaporization temperature of the working fluid. Therefore, the heat pipe is effective in a case where the temperature of the body to be cooled is required to be lowered substantially to the room temperature. In many cases, heat pipes are employed as not only the connection between the conductive metal body and the fins but also as the heat spreader. And heat pipes are also employed with the heat transferring metal body.
There is shown in
FIG. 30
a heat spreader in which a heat pipe is embedded in the heat transferring body. A heat pipe
109
is incorporated into a heat transferring metal body
108
, thereby reducing the weight of the heat transferring metal body
108
by an the amount that the heat transferring metal body
108
is replaced by the heat pipe
109
. Although this heat pipe is thick and short in length, the construction thereof is the same as that of the usual heat pipe, so it may be called the plate-like flat heat pipe.
Recently, equipment including electronic products have been improved with respect to function and are made small-sized and light-weight by using electronic parts such as semiconductor devices, which require the temperature to be limited to room temperature. In such equipment, it is advantageous that instead of the heat transferring metal body, the heat pipe is employed as the heat spreader.
The heat pipe has a disadvantage in that the heat absorbing side of the heat pipe must be located below the heat radiation side because the liquefied working fluid flows downwardly. For the purpose of eliminating this disadvantage it is proposed that the liquefied working fluid is guided by means of wicks. The wick, which has a capillary function, moves liquid by surface tension. For example, Japanese Patent Provisional Publication (Kokai) No. 7-208884 proposed that a plate-like heat pipe having block-like wicks each formed by numerous capillaries tubes are arranged so as to contact with upper and lower surfaces of the heat pipe.
The above-mentioned proposal is shown in FIG.
31
. FIG.
31
(
a
) is a longitudinal sectional view of a container
200
containing working fluid, and
FIG. 31
(b) is a cross sectional view thereof. First wicks
201
are disposed between a heat radiating wall
202
and a heat absorbing wall
203
, with a space
204
formed therearound, and then second wicks
205
are disposed along the heat radiation wall
202
and the heat absorbing wall
203
. Then as shown in
FIG. 31
(b), there are a plurality of the first wicks
201
, which are arranged radially.
The first wick
201
, having a strong capillary force, is formed into a block, whereas the second wick
205
, having a weak capillary force, comprises slightly rough metal wire mesh, each arranged horizontally, are stacked one over another. Reference numeral
210
designates an exothermic body. Even if the exothermic body
210
is located above the container
200
, which is in the so-called top heat mode, the working fluid in the liquid phase condensed at the heat radiating wall
202
located below and is transferred to the heat absorbing wall
203
located above by means of the first wick
201
. Then, the working fluid evaporates into a gas phase at the heat absorbing wall
203
and reaches the heat radiating wall
202
through the space
204
from the second wick
205
having a rough mesh.
However, in the field of the electronic products and the like, the bodies to be cooled are, in many cases, small in size and high in exothermic density like the semiconductor devices. In the above-mentioned heat pipe, the portion of the heat absorbing wall with which the exothermic body contacts is also contacted by working fluid in the liquid phase that is sealed in the mesh of the metal wire gauze, like the non-contacting portion.
The portion of the
Ikeda Masami
Niekawa Jun
Sasaki Ken
Ueki Tatuhiko
Yamamoto Masaaki
Lazarus Ira S.
McKinnon Terrell
The Furukawa Electric Co. Ltd.
Thorp Reed & Armstrong
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