Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2000-02-29
2001-08-14
Picard, Leo P. (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S707000, C361S709000, C361S712000, C361S719000, C257S719000, C257S718000, C257S727000, C174S016300, C165S080200, C165S080300
Reexamination Certificate
active
06275380
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to cooling of electronic components in electronic devices. More particularly, the present invention relates to the removable attachment of an additional heat sink to a primary heat sink of an electronic device.
BACKGROUND OF THE INVENTION
As the art moves towards higher power integrated circuits and components, hereinafter referred to as heat emitting components, heat transfer from the heat emitting components becomes increasingly difficult and more important. One conventional technique used to remove heat from a heat emitting component was to employ a finned heat sink which was placed in thermal contact with the heat emitting component. In this manner, heat generated by the heat emitting component was conducted to the heat sink and then dissipated to the ambient environment.
FIG. 1
is a front plan view of a heat sink structure
10
in accordance with the prior art. Heat sink structure
10
included a finned heat sink
12
in thermal contact with a heat emitting component
14
. During use, heat emitting component
14
generated heat. This heat was conducted to heat sink
12
, which dissipated this heat to the ambient environment.
To provide the greatest flexibility in the use of heat sink
12
, fins
16
of heat sink
12
were made relatively short. In this manner, heat sink
12
could be used in a variety of different computer systems having a variety of different spacings between the cabinet and a printed circuit board
20
, to which heat emitting component
14
was attached. To illustrate, by forming relatively short fins
16
, heat sink
12
could be used with a cabinet
18
(indicated in dashed lines), which was spaced relatively close to printed circuit board
20
. Further, heat sink
12
could be readily used with a cabinet
22
, which was space relatively far from printed circuit board
20
.
When used with cabinet
18
, heat sink
12
was relatively effective at dissipating heat from heat emitting component
14
. In particular, air was forced to flow between fins
16
due to the relatively small spacing between printed circuit board
20
and cabinet
18
.
However, when used with cabinet
22
, heat sink
12
was relatively ineffective at dissipating heat from heat emitting component
14
. In particular, since air follows a path of least resistance, the air had a tendency to flow between heat sink
12
and cabinet
22
instead of between fins
16
.
To provide adequate cooling of heat emitting component
14
when used with cabinet
22
, heat sink
12
could be replaced with another heat sink having longer fins. Disadvantageously, since the spacing between cabinet
22
and printed circuit board
20
varied depending upon the particular manufacturer, a large number of different heat sinks had to be stocked to accommodate the different manufacturer specifications. To avoid the complexity and cost associated with stocking a large number of different heat sinks, heat sink
12
having relatively short fins
16
was used for all manufacturers regardless of the spacing between cabinet
22
and printed circuit board
20
.
To enhance heat dissipation from heat sink
12
when the spacing between cabinet
22
and printed circuit board
20
was relatively large, additional and/or more powerful fans were used. However, to avoid excess power consumption and to avoid exceeding noise level limits, the size of these additional and/or more powerful fans was severely restricted.
Accordingly, the art needs a method of enhancing heat transfer from a heat emitting component using a heat sink having relatively short fins without having to providing additional and/or more powerful fans.
SUMMARY OF THE INVENTION
In accordance with the present invention, a heat sink structure includes first and second add-on heat sinks mounted to a primary heat sink. The primary heat sink is in thermal contact with a heat emitting component. The add-on heat sinks enhance heat transfer from the primary heat sink in several ways. First, since the add-on heat sinks are thermally connected to the primary heat sink, the effective heat transfer surface area for dissipating heat to the ambient environment is increased compared to the surface area of the primary heat sink alone. Increasing the effective heat transfer surface area increases heat dissipation to the ambient environment.
The add-on heat sinks also enhance heat transfer from the primary heat sink by improving airflow between fins of the primary heat sink. More particularly, the add-on heat sinks restrict air from flowing between the primary heat sink and a cabinet, which is spaced relatively far from a substrate, e.g., printed circuit board, to which the heat emitting component is attached. In this manner, the add-on heat sinks force air to flow between the fins of the primary heat sink, thus enhancing heat transfer from the primary heat sink.
Advantageously, the add-on heat sinks enhance heat transfer from the primary heat sink when the spacing between the cabinet and the printed circuit board is sufficiently large such that the primary heat sink would otherwise be ineffective at cooling the heat emitting component. By enhancing heat transfer from the primary heat sink, the add-on heat sinks ensure that the temperature of the heat emitting component remains below the maximum allowable operating temperature of the heat emitting component.
However, in the event that the spacing between the cabinet and the printed circuit board is sufficiently small such that the primary heat sink alone is effective at cooling the heat emitting component, the add-on heat sinks are not provided.
Advantageously, the primary heat sink is used with all spacings between the cabinet and the printed circuit board. In the event that the spacing between the cabinet and the printed circuit board becomes sufficiently large such that the primary heat sink alone would be ineffective at cooling the heat emitting component, only then are the add-on heat sinks provided. Accordingly, only a single primary heat sink is stocked for all manufacturers.
Recall that in the prior art, a large number of different heat sinks had to be stocked to accommodate the different spacings between the cabinet and the printed circuit board for the various manufacturers. Disadvantageously, stocking a large number of different heat sinks was cost prohibitive.
Alternatively, in the prior art, a single heat sink having relatively short fins was used for all manufacturers regardless of the spacing between the cabinet and the printed circuit board. To enhance heat transfer from the heat emitting component and heat sink when the spacing between the cabinet and printed circuit board became relatively large, additional and/or more powerful fans were used. Disadvantageously, these additional and/or more powerful fans consumed more power, which increased the operating cost of the computer system. Further, these additional and/or more powerful fans resulted in an increase in noise, which was detrimental to the performance of the computer system.
In contrast, the heat sink structure in accordance with the present invention provides effective cooling of the heat emitting component even when the spacing between the cabinet and the printed circuit board becomes relatively large. Effective cooling of the heat emitting component is achieved using only a single primary heat sink for all manufacturers. Further, effective cooling of the heat emitting component is achieved without having to power a fan and without generating noise. Accordingly, the prior art requirements of stocking a large number of heat sinks and providing additional and/or more powerful fans are eliminated.
In one embodiment, a simple yet reliable method of mounting an add-on heat sink to a primary heat sink is presented. To mount the add-on heat sink to the primary heat sink, the add-on heat sink is positioned such that locking features of the add-on heat sink are substantially aligned with sides of the primary heat sink.
The add-on heat sink is pressed towards the primary heat sink. This causes a first
Chervinsky Boris L.
Gunnison McKay & Hodgson, L.L.P.
Hodgson Serge J.
Picard Leo P.
Sun Microsystems Inc.
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