Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2001-11-20
2003-02-11
Schuberg, Darren (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S692000, C361S707000, C361S721000, C257S707000, C174S016300
Reexamination Certificate
active
06519156
ABSTRACT:
TECHNICAL FIELD
The present invention is related to heat sinks for printed circuit boards, and more particularly to a system and method of transferring heat from electronic devices using a surface mounted conduction heat sink.
BACKGROUND
Circuit boards are becoming more and more densely packed with electronic devices as the need for power, memory and additional capabilities increases. As a result the heat generated by these electronic devices also increases. The heat that is generated by an electronic device must be transferred away from the electronic device or the performance of the electronic device(s) will deteriorate. The problem of dissipating heat from electronic devices mounted on circuit boards gets worse when the piece of equipment employing the circuit board is mounted within a housing. For example, fiber optic transmitter/receiver modules that include circuit boards are often environmentally sealed in a housing to prevent damage from the elements. As a result, the ability to dissipate heat from the electronic devices mounted on the circuit boards becomes challenging. The environmental housing's only mode of heat transfer to the ambient is natural convection. The transmitter/receiver module's only mode of heat transfer to the environmental housing is conduction.
A classic thermal management technique uses thermal vias to dissipate heat. The thermal vias are located in a copper pad of a printed circuit board, under the device that needs cooling. A heat sink pad of a device is soldered to the copper pad of the circuit board. During operation of the device, heat is transferred from the device's heat sink pad to the copper pad on the primary side of the circuit board. The heat is then transferred through the thermal vias to the far (secondary) side of the circuit board and to the housing of the transmitter/receiver module. The heat is then transferred by conduction from the transmitter/receiver module to the unit's environmental housing. As the component density in an electronic module increases, it becomes difficult to use classical thermal vias to dissipate heat.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for
SUMMARY
The above-mentioned problems with meeting the thermal requirements of electronic devices mounted on circuit boards are addressed by the present invention and will be understood by reading and studying the following specification. Embodiments of the present invention provide heat sinks for facilitating meeting the thermal requirements of electronic devices mounted on circuit boards.
More particularly, in one embodiment, a heat sink is provided that has a leg and a member coupled substantially perpendicular to the leg at a first end of the leg. The leg is surface mountable to a first surface of a printed circuit board at a second end of the leg to receive heat from an electronic device on a second surface of the printed circuit board by a thermally conductive via through the printed circuit board.
In another embodiment, a heat sink is provided that has a first U-shaped portion, a second U-shaped portion, and a pair of thermally conductive vias. The first U-shaped portion is mountable on a first surface of a printed circuit board for straddling an electronic device on the first surface of the printed circuit board. Further, the first U-shaped portion has an interior surface for thermally coupling to an outer surface of the electronic device. The second U-shaped portion is mountable on a second surface of the printed circuit board. The pair of thermally conductive vias is for passing between the first and second surfaces of the printed circuit board. Moreover, each of the pair of thermally conductive vias is for respectively thermally coupling each of first and second legs of the “U” of the second U-shaped portion to the electronic device.
In yet another embodiment, a method of removing heat from an electronic device is provided. The method includes transferring the heat from an electronic device mounted on a first surface of a printed circuit board to a first heat transfer pad of the electronic device. The method includes transferring the heat from the first heat transfer pad to a second heat transfer pad coupled to the first heat transfer pad, where the second heat transfer pad is on the first surface of a printed circuit board. Moreover, the method includes transferring the heat from the second heat transfer pad to a heat sink that is mounted on a second surface of the printed circuit board and that straddles a component on the second surface using a thermally conductive via that passes through the printed circuit board and that thermally couples the second heat transfer pad to the heat sink. The method also includes transferring the heat from the heat sink to an outer housing that encloses the printed circuit board.
Other embodiments are described and claimed.
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“Thermal Management Products,” a catalogue from Chomerics, a division of Parker Hannifin Corp., 68 pp. (1999).
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ADC Telecommunications Inc.
Datskovsky Michael
Fogg and Associates LLC
Ryan Laura A.
Schuberg Darren
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