Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-02-04
2001-01-30
Tolin, Gerald (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C029S845000, C361S704000
Reexamination Certificate
active
06181561
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 standoff buttons and a method of manufacture therefor.
BACKGROUND OF THE INVENTION
One of the concerns of circuit designers is the control of circuit or component heat generated during operation of an electronic circuit. Such control is necessary in order to prevent component or circuit failure caused by a heat build up. The generally preferred method to control circuit and component heat is to dissipate it into the atmosphere before it can build up to damaging levels. In order to do this, designers will usually associate the components or circuit with a heat sink to absorb heat from the component or circuit and radiate it into the atmosphere.
Heat sinks are generally made of a material with favorable heat transfer, or thermal conductive, characteristics; that is, the material must be able to absorb heat and radiate it into the surrounding atmosphere in an efficient manner. Several metals have favorable thermal conductive characteristics, including copper, aluminum, steel, and their alloys. Any one of these materials can be used as a heat sink, but aluminum is generally the preferred material because copper is expensive and steel is not very malleable.
Heat sinks are made in a variety of shapes and sizes and several methods exist for combining heat sinks with circuits or components. Sometimes the heat sink is mounted directly to the heat generating component while at other times the entire circuit will be associated with a single heat sink. In the case of circuits mounted on small printed circuit or wiring boards, the entire circuit or wiring board will frequently have a single heat sink mounted on it. In most cases printed wiring and circuit boards that are small in size will require a single heat sink consisting of a single sheet of metallic material, such as aluminum, shaped to conform to the circuit with which it will be associated. Using prior art, the heat sink will be fastened to the circuit by a method or mechanism that will leave an air space for insulation purposes between the circuit board and the heat sink in order to prevent the metallic heat sink from shorting the circuit on the printed circuit or wiring board.
In many conventional devices, if a small flat printed wiring or circuit board is required to be associated with a heat sink, then a flat piece of aluminum of approximately the same size as the circuit board is designated for use as a heat sink. The circuit or wiring board and heat sink are typically mounted so they directly oppose each other. When in this configuration, the heat sink is able to absorb heat emitted by the circuit and components mounted on the board. The heat sink is typically held in place by using any one of several well recognized fastening means, such as clips, screws, pins, or bolts. Additionally, in order to keep the heat sink from coming into direct contact with the circuit or wiring board, spacers are used to keep the circuit board and the heat sink separated.
These conventional assemblies require several small parts that must meticulously be assembled, which generally means the manufacturing process is slower and more costly. Additionally, a number of assemblies are typically rejected for quality control reasons when numerous small parts are used because of the ease with which a part may be inadvertently omitted or come apart due to vibration and handling that occurs during the remainder of the assembly process.
Accordingly, what is needed in the art is a heat sink that can be associated with a circuit requiring heat control that has a simple attachment method and uses substantially fewer parts than prior art methods.
SUMMARY OF THE INVENTION
To address the above-discussed deficiencies of the prior art, the present invention provides a method of manufacturing a heat sink for use with a circuit board having a predetermined thickness and an opening formed therein. In one particularly advantageous embodiment the method comprises forming a heat sink body, forming a support shoulder in the heat sink body by protruding a portion of the heat sink body to a predetermined first height, and forming a button shoulder in the heat sink body by protruding a portion of the support shoulder to a predetermined second height. Preferably, the heat sink body comprises aluminum or aluminum alloy. However, it should, of course, be recognized that other extrudable or malleable materials may be used in place of aluminum or its alloys. Additionally, it should be understood that a plurality of such support shoulders and button shoulders may be formed to provide a plurality of coupling points with the circuit board, which could also have a corresponding number of openings.
Thus, in a broad scope, the present invention provides a novel heat sink attachment system and method for manufacturing that attachment system. For example, the support shoulder and the button shoulder can be easily manufactured by double drawing the metal heat sink body with a die, such as a die on a progressive die press. Alternatively, of course, the heat sink body may be extruded to form the support shoulder and the button shoulder. Because there are no assembly parts required, manufacturing time and cost are substantially reduced. Additionally, the because of the ease with which the support shoulder and the button shoulder can be formed, mass production of the heat sink is easily accomplished.
The present method invention may further include forming an outer diameter of the button shoulder that is less than an inner diameter of the opening. This aspect allows for easy insertion of the button shoulder into the opening. In another aspect, the forming a support shoulder includes forming a spacer shoulder having a protrusion height that provides a maximum design distance of separation between the heat sink and the circuit board. Typically, electronic components will be attached to the same side of the circuit board on which the heat sink is mounted. In such instances, the spacer shoulder's height is such that the electronic component is thermally coupled to the heat sink when it is mounted on the circuit board. In some instances, the electronic component is thermally coupled to the heat sink by way of a thermal conducting silicon gel, such as a diamond filled silicon. Thus, the support shoulder also serves as a spacer to provide the required distance of separation between the circuit board and the heat sink.
In another embodiment, forming the button shoulder to a predetermined second height includes forming a button shoulder to height that does not substantially exceed the thickness of the circuit board. What is meant by not substantially exceeding the thickness of the circuit board means that the protruding portion of the button shoulder does not protrude far enough above the circuit board such that it will bend over onto circuit board when a spreading force is applied against the button shoulder.
In another aspect, the present invention provides a method of manufacturing a circuit board. In this particular embodiment, the method includes forming a circuit board having an opening therein and a predetermined thickness, forming a heat sink body, inserting the protruding portion of the button shoulder into the opening and applying a force against the protruding portion to increase a diameter thereof and effectuate a frictional holding force of the button shoulder against an interior diameter of the opening. In this embodiment, forming a heat sink includes forming a support shoulder in the heat sink body by protruding a portion of the heat sink body to a predetermined first height and forming a button shoulder in the heat sink body by protruding a portion of the support shoulder to a predetermined second height.
In yet another aspect, the present invention provides a heat sink for use with a circuit board having a predetermined thickness and an opening formed therein. The heat sink comprises a heat sink body, a support shoulder formed in a surface
Albrecht Louis R.
Hansen James J.
Shewmake Steven A.
Lucent Technologies - Inc.
Tolin Gerald
LandOfFree
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