Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-10-15
2001-06-19
Picard, Leo P. (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S704000, C361S707000, C257S707000, C174S015100, C165S080300
Reexamination Certificate
active
06249437
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention is directed, in general, to a heat sink and, more specifically, to a heat sink having an offset fin profile for use in electronic and electrical equipment.
BACKGROUND OF THE INVENTION
Miniaturization of components has increased component and power densities in electronic devices to higher levels than ever before. These electronic and electrical components and devices mounted on printed circuit and wiring boards generate considerable operating heat that, unless dissipated to the environment, may result in temperature related circuit or component failure. Experience has shown that nearly 50% of electronic failures are the result of thermal problems. The generally preferred control method is to use a heat sink to transfer component heat to the surrounding ambient air.
A heat sink can be made of any material with favorable heat transfer characteristics, such as copper, aluminum or steel. Aluminum is generally preferred because it is inexpensive, easy to work with, lightweight, and has good heat transfer characteristics. Where aluminum is used, the less alloying material used in the aluminum, the better the heat transfer characteristics.
The heat sink and heat generating component are usually placed in direct contact with one another in order to more efficiently cool the component. In most cases, after the heat sink absorbs component heat, the heat is transferred to the surrounding ambient air by conduction and convection. A typical printed wiring or circuit board may have a number of heat generating devices. That is why it is not unusual to have a number of heat sinks on a single circuit board associated with heat generating devices and components. Because circuits are frequently enclosed in cabinets or other enclosures, a fan is usually employed to move cooling air across the heat sink and facilitate the transfer of heat.
When a number of heat sinks are required, design factors in addition to temperature control must be taken into consideration. When a printed circuit or wiring board requires multiple heat sinks, the board area occupied by heat sinks will often constitute a significant fraction of the total board space. Similarly, a significant fraction of the total volume available to house a circuit will be taken up by heat sinks when a number of heat sinks are required. As the total area on a board required for heat sinks becomes significant, the board real estate allocated to components also becomes affected by heat sink requirements. Of course, the more efficient heat sink designs will require less area and will be lighter than heat sinks that are not as efficient.
In order to facilitate heat transfer, heat sinks frequently have “fins” to increase the total surface area that serves to conduct and convect heat. These fins typically extend into the flow of air and dissipate the conducted heat into the surrounding ambient air by convection. In most cases, the fins on the heat sink that are located closer to the air flow source will provide for more efficient cooling than those located further away from the air flow source. This is true for a number of reasons, one of which is that air flow to the fins at the leading edge is not blocked, whereas the later fins will be in a dead air zone.
Accordingly, what is needed in the art is a heat sink design that will maximize the efficiency of the heat sink device by permitting the maximum amount of cooling air available to contact the maximum cooling fin surface area of the heat sink in order to provide for more efficient cooling of heat generating devices located in an electronics circuit.
SUMMARY OF THE INVENTION
To address the above-discussed deficiencies of the prior art, the present invention provides for a uniquely configured heat sink. In one particularly advantageous embodiment, the heat sink includes a heat sink body with a spine configured to be oriented parallel with the direction of an air flow generated across the heat sink when it is coupled to a substrate. The heat sink also includes a first set of cooling fins coupled to and extending from the heat sink spine along a first common longitudinal axis. At least two of the first set of cooling fins laterally extend from the first common longitudinal axis in a common direction and in an offset relationship to each other.
Thus, in broad scope, the present invention provides for a heat sink with superior cooling capability for use on electronic substrates to which are coupled heat generating components. The heat sink has a set of offset cooling fins extending from a spine into a cooling air flow that is usually forced across the substrate. The cooling fins are offset in order to permit an unimpeded air flow to contact a leading edge on each fin. This novel heat sink device provides an increase in cooling efficiency over heat sinks that are not configured with offset cooling fins.
One embodiment of the present invention provides for the heat sink to be configured to have at least one heat generating component mounted thereon. In another embodiment, the heat sink is comprised of aluminum. In still another embodiment, the heat sink has a mounting foot extending laterally from the spine that is configured to permit the heat sink to be coupled to an electronic substrate.
In another embodiment, the present invention provides for a heat sink with a first set of cooling fins laterally extending from a first common longitudinal axis in a common direction and in an offset relationship to each other. In still another aspect of the invention, the heat sink provides for each of the cooling fins to include a leading face that is oriented substantially perpendicular to the direction of the air flow and in an offset relationship so that an unimpeded air flow impacts the leading face of each cooling fin.
In a particularly useful embodiment of the invention, the heat sink has a second set of cooling fins extending from and coupled to the spine along a second common longitudinal axis. In this embodiment, at least two of the second set of cooling fins extend laterally from the second common longitudinal axis in a common direction and in an offset relationship to each other. Another aspect of this embodiment provides for the common direction to be towards the first common longitudinal axis.
The present invention also provides for a method of manufacturing a heat sink with superior cooling capability for use on an electronic substrate to which are coupled heat generating components. The method, in one embodiment, comprises forming a heat sink body with a spine configured to be oriented parallel with the air flow direction when the heat sink is coupled to a substrate. A first set of cooling fins is formed extending from and coupled to the spine along a first common longitudinal axis. At least two of the first set of cooling fins extend laterally from the first common longitudinal axis in a common direction and in an offset relationship to each other. Another particularly beneficial embodiment of the method of manufacturing the heat sink provides for the heat sink to be formed by stamping. This permits the use of a relatively inexpensive process to manufacture heat sinks and also permits the use of aluminum with a minimum of alloying material added.
In still another embodiment, the heat sink is formed with a second set of cooling fins extending from the spine. The second set of cooling fins is coupled to the spine along a second common longitudinal axis with at least two of the cooling fins laterally extending from the second common longitudinal axis in a common direction and in an offset relationship to each other. Another aspect of this embodiment provides for the common direction to be toward the first common longitudinal axis.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of th
Ferranti Stephen A.
Ganesa-Pillai Madhu
Klafter Leon
Mello John Paul
Reeves Amanda C.
Datskovsky Michael
Picard Leo P.
Tyco Electronics Logistics AG
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