Heat exchange – With retainer for removable article – Electrical component
Reexamination Certificate
2000-10-04
2003-04-08
Flanigan, Allen (Department: 3743)
Heat exchange
With retainer for removable article
Electrical component
C361S704000
Reexamination Certificate
active
06543521
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a cooling apparatus. More particularly, the present invention relates to a cooling element (heat sink) which is used to cool heat producing semiconductor devices such as integrated circuits (IC), large scale integration (LSI), micro processing units (MPU), and to cooling apparatuses comprising heat sinks and blowers such as air cooling fans.
BACKGROUND OF THE INVENTION
Higher integration of electronic components and increasing frequencies of operation clocks have been increasing the heat produced by such components in recent years. Under such circumstances, maintaining actual operation temperatures of the electronic components within the range of operation guarantee temperatures has been becoming a critical issue in securing the normal functioning of the electronic components. Increases in integration and frequencies of the micro processing units (MPU) and other electronic components which emit considerable heat have been remarkable. Thus, dissipation of the heat produced by such electronic components has been becoming increasingly important in order to stabilize their operation and secure their operational life.
In general, a cooling apparatus which is used to dissipate heat produced by electronic components comprises a heat sink which expands the heat dissipation area and effectively transfers heat to a refrigerant such as air, and an air cooling fan which forcibly blows refrigerant such as air to the heatsink. These heat sinks comprise a base plate which spreads out the heat produced by the heat producing element and heat dissipation fins which transfer heat. Common types of heat sink include a plate-fin type and a pin-type fin in which, respectively many thin plates and pins are disposed on a base plate. These heatsinks are mainly constructed of materials of high thermal conductivity such as aluminum and copper, and produced by such methods as the extrusion molding method, the cold forging method, the die casting method, and the thin-plate lamination method.
Regarding the ways to mount the cooling apparatus onto an electronic component which emits considerable heat (hereinafter, heat producing element), it can be mounted either directly onto the heat producing element as illustrated in
FIG. 10A
, or indirectly by inserting a heat conducting plate between the heat producing element and the heat sink, as illustrated in FIG.
10
B. The heat conducting plate is designed to conduct the heat produced by the heat producing element to the heatsink and to dissipate heat, and also to protect the heat producing element. The cooling mechanism of the cooling apparatus in use is described as follows: heat produced by the heat producing element shown in
FIG. 10A
, is conducted to heat dissipation fins
1
via a heat-conductive base section
2
made of materials of high thermal conductivity such as aluminum, and, over the surface of the heat dissipation fins
1
, is transferred and dissipated into the air blown by a cooling fan
5
, to be cooled.
In order to improve the performance of the cooling apparatus, heat is most desirably distributed evenly throughout the base plate, and dissipated through all of the heat dissipation fins. However, heat emitted from the heat producing element tends to be conducted predominantly to the heat dissipation fins disposed right above the heat producing element, and the amount of the heat conducted to the peripheral heat dissipation fins is relatively small. The reason for this is that the heat producing element is much smaller than the base plate, thus contact area between them is very limited. Consequently, the heat dissipation fins as a whole often fail to function effectively.
The most important point here is how to conduct heat emitted from the heat producing elements effectively to the heat dissipation fins over the broadest possible area, as mentioned previously. Some conventional methods focus on this point. For example, the Japanese Patent Application Laid Open Publication No. H09-298259 discloses a method of improving the cooling ability in which, in order to enhance the heat dissipation effect of the base plate, as shown in
FIG. 11
, the entire surface of the base section on the heat producing element side is covered with a metallic material such as copper whose thermal conductivity is at least higher than that of aluminum.
In the case of the forced air cooling system, in which outside air is forcibly blown onto the surface of the fins
1
by a fan, the heat dissipation ability of the fins
1
is determined by the amount of the heat transferred to the influent air from the surface of the fins
1
. In other words, the heat dissipation ability is determined by the volume of air exhausted outside from the heat sink per unit of time. Simply put, it is necessary to form the fins
1
over an area as broad as possible and provide a large amount of air. However, as previously mentioned, in the case of currently available electronic apparatuses, the proportion of the heat sink to the apparatus as a whole limits the available space. Thus, the applicable number of the fins, and the size and capability of the fans are inevitably limited, hampering the achievement of a high cooling ability. In some cases, conventional heat sinks are produced in such a manner that the greatest possible number of fins
1
for each unit area are formed on the base
2
in order to enhance the heat dissipation ability by increasing the heat dissipation area. However, in this case, as the number of the fins per unit area increases, the space between the fins becomes narrower, thus increasing fluid resistance to the air brought in by the fan. As a result, the absolute volume of air flow decreases, lowering the heat dissipation ability per unit of time. As such, the cooling ability is determined by the balance between the level of an increase in the heat dissipation area and a decrease in the air flow. Thus, mere increase in the surface area does not lead to an improvement in the cooling ability.
Therefore, in order to achieve a high ability while reducing the size and weight as much as possible, it is essential to improve the performance of the base
2
which conducts heat to the fins
1
.
The above description is mainly focused on the cooling elements and cooling apparatus used for the electronic components, however, the same theory can be applied to other general heat producing elements.
The present invention aims at providing cooling elements and cooling apparatus using the same which are effectively used for cooling heat producing elements in general.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a smaller and lighter heat sink having a higher heat dissipation ability and a cooling apparatus using such heat sink.
The cooling element of the present invention comprises a base section which is in contact with a heat producing element to be cooled, and a heat dissipation section composed of heat dissipation fins, which is integrally formed with the base section. The cooling element is constructed such that the ratio of T (thickness of the base section) to L (reference length, namely, either the shortest width of the base section right above the heat producing element or its external diameter) is within the range of not less than 0.14 and not more than 0.24.
Another cooling element of the present invention comprises a base section which is in contact with a heat producing element to be cooled, and a heat dissipation section composed of heat dissipation fins, which is integrally formed with the base section. This cooling element is constructed such that the ratio of d (length of a face of the base section, which faces the heat producing element) to L2 (reference length of the base section, namely, either the length of the longest length of the base section or its external diameter) is not less than 0.5.
The cooling apparatus of the present invention comprises the cooling element of the present invention and an air blowing device.
With the construction mentioned above, the present invention aims
Fujiwara Yasuhiro
Kamizuru Shinobu
Sato Kaoru
Sugimoto Kazuhiko
Tate Sumio
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