System for clamping heat sink

A system for clamping a heat sink that prevents excessive clamping force is provided. The system may include a heat sink, a semiconductor device, a printed circuit board, and a cover. The semiconductor device may be mounted onto the circuit board and attached to the cover. The heat sink may be designed to interface with the semiconductor device to transfer heat away from the semiconductor device and dissipate the heat into the environment. Accordingly, the heat sink may be clamped into a tight mechanical connection with the semiconductor device to minimize thermal resistance between the semiconductor device and the heat sink. To prevent excessive clamping force from damaging the semiconductor device, loading columns may extend between the cover and the heat sink.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention is generally related to a system for clamping a heat sink. More specifically, the invention relates to a system for clamping a heat sink that prevents excessive clamping force.

2. Related Art

When performing various functions, integrated circuits tend to generate heat. The integrated circuit may be cooled by dissipating heat into the surrounding environment. Particularly in the audio electronics industry, the market has required manufacturers to provide smaller electronic packages along with improved audio performance and power. To improve heat dissipation, heat sinks or blocks of metal may be connected with semiconductor devices to conduct heat away from the semiconductor device and provide a larger surface area from which to dissipate the heat. The heat sink often include fins to increase the surface area for heat dissipation and may even include a channel that provides fluid cooling. This may be particularly important with regard to power amplifiers and audio circuits, as they can generate a significant amount of heat and may require cooling to maintain audio performance of the electronic component.

When attaching a heat sink to the semiconductor device, it may be important to have a tight mechanical coupling of the surface of the heat sink with the surface of the semiconductor device to minimize thermal resistance when transferring heat from the semiconductor device to the heat sink. Often, the components must be securely attached in a manner that will withstand harsh vibration and shock. For example, harsh shock and vibration are often encountered in an automotive audio environment. However, clamping the semiconductor device with excessive force can cause damage to the semiconductor device. Accordingly, there is a need to control the force used in securely clamping a heat sink to a semiconductor device.

SUMMARY

This invention provides a system for clamping a heat sink that prevents excessive clamping force. The system may include a heat sink, a semiconductor device, a printed circuit board, and a cover. The semiconductor device may be mounted onto the circuit board and attached to the cover. The heat sink may be designed to interface with the semiconductor device to transfer heat away from the semiconductor device and dissipate the heat into the environment. Accordingly, the heat sink may be clamped into a tight mechanical connection to minimize thermal resistance between the semiconductor device and the heat sink.

The clamping may be accomplished using bolts that are inserted through openings in the cover and threaded into the heat sink. Tightening the bolts may apply a clamping force that presses the heat sink against the semiconductor device. To prevent excessive clamping force from damaging the semiconductor device, loading columns may extend between the cover and the heat sink. The loading columns serve as a stop or structural support that act against the clamping force when the bolts are torqued. In addition, a button may be formed in the cover beneath the semiconductor device to act as a support for the semiconductor device. Further, a teardrop shaped support may be formed in the cover to support the printed circuit board. The teardrop shaped support may include a head portion with bolt openings and a tail portion that extends toward the semiconductor device to support the printed circuit board.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

InFIG. 1, an example of an electronic assembly10is provided. The electronic assembly10may include a semiconductor device12, a circuit board14, a heat sink18and a cover16. The semiconductor device12may be in the form of a power amplifier or other semiconductor device that generates heat during usage. These devices often include a ceramic casing and metal pins or pads for facilitating electrical connection. One such device may be the TDA8594J amplifier from PHILIPS electronics. Accordingly, the heat sink18may be provided to receive heat from the semiconductor device12. The heat sink18transfers heat away from the semiconductor device12and provides an increased surface area allowing improved dissipation of the heat into the environment of the electronic assembly10.

The electronic assembly10may also include a circuit board14such as a printed circuit board to which the semiconductor device12may be mounted. The circuit board14may be made of a plastic and may include metal traces that may be coupled to the semiconductor device12. The traces may provide electrical power as well as data signals, such as audio data signals, and/or control signals to the semiconductor device12for processing. In addition, the circuit board14may include additional traces for communicating output signals, such as audio signals, to other components or a speaker system after processing. A cover16extends around and protects the circuit board14and semiconductor device12. The cover16may be formed from a metal sheet, for example, through a series of forming or stamping events. The cover may be made of from any rigid material such as a steel or other metal, although the cover may also be made from other deformable materials such as plastic or a fibrous material. The cover may include a corrosion resistant plating. For example, the cover can be made of a steel sheet with a thickness of 1.0 mm and including a zinc coating. The cover16includes loading columns24that extend from an outer surface of the cover through a hole in the circuit board14toward the heat sink18. The loading columns24prevent the application of excessive clamping force on the heat sink18. As such, the loading columns24provide structural support to the heat sink18and prevent damage to the semiconductor device12.

The heat sink18may be clamped to the semiconductor device12using a fastener20. InFIGS. 1 and 2, the fastener20is shown as a bolt that may be threaded into a bore22formed in the heat sink18. Accordingly, the fastener20extends through an opening in the cover16, continues through an opening in the circuit board14, and engages the heat sink18. As mentioned, the fastener20may engage the heat sink18through a threaded engagement. Screws, rivets, clamps or any other fasteners may also be readily used. In the bolt arrangement shown, providing increased torque on the fastener20generates additional clamping forces by compressing the semiconductor device12between the heat sink18and the cover16. As shown inFIG. 1, the loading columns24and fastener arrangement may be provided at multiple locations around the semiconductor device12, for example on the opposite sides of the semiconductor device12to securely balance compression of the heat sink18against the semiconductor device12. The columns24may extend slightly above the semiconductor device12requiring compression of the columns24. Alternatively, the columns24may extend flush with or below the semiconductor device12. Similarly, the columns24may all be the same length or may be different lengths thereby providing additional support as the compression increases. In addition, a button28may be formed in the cover16to act as a spring between the cover16and the semiconductor device12to absorb forces that may otherwise over compress the semiconductor device12. Further, the button28may have a rounded or generally dome shape causing the bend of the sheet metal to act as a deformable spring. Further, the button28may include a flat top surface that reacts with the semiconductor device12through the printed circuit board14. As such, the cover16forms a planar surface and a button28extends from the planar surface and forms a second planar surface parallel to the first planar surface that reacts with the semiconductor device12. Further, the loading columns24also extend from the planar surface and may be formed substantially perpendicular to a planar surface. It is also understood that other deformable springs for example, leaf springs or coil springs may be used in place of the button28to absorb forces. However, the button28may be integrally formed in the cover16. As may further be seen inFIG. 2, the heat sink18may include fins32extending away from the semiconductor device12providing additional surface area to improve heat dissipation through convection cooling. In addition, the fastener20may be located in a channel30formed in the cover16.

InFIGS. 3,4and5, additional views of the cover16fromFIG. 2are provided. The cover16may extend along and around the printed circuit board14and may include cooling holes50allowing for the flow of air for convection cooling of the heat sink18, semiconductor device12, and the circuit board14. The cover16may interface with another housing portion that forms part of the heat sink18(seen inFIG. 2). The cover16may surround and protect the components of the electronic assembly including the circuit board14and the semiconductor device12. The cover16may be formed of a metal sheet through various stamping and forming processes. The trench30may be formed across the cover and may be used for housing multiple semiconductor devices, for example a pair of power amplifiers. The button28may be stamped into the cover forming a rounded domed configuration including a flattened top surface providing a more stable mechanical interface. The button28, as described previously, may act as a spring against semiconductor device12to absorb the clamping force. In a similar manner, the loading columns24may be stamped into cover16and bent perpendicular to a top surface of the trench30to absorb additional clamping force and prevent over clamping of the heat sink18and damage to the semiconductor device12. In addition, a recess42may be formed in the cover16for supporting the circuit board14and distributing the force from the fastener20across the circuit board14. The recess42may extend from the planar surface of the cover16toward the circuit board14. The recess42may include a flat surface parallel to the planar surface that is elongated and extends towards the middle of the semiconductor device12to provide additional support for the semiconductor device12. As such, the recess42may have a generally teardrop shape with the head of the teardrop surrounding the fastener opening44and the tail of the teardrop extending towards the middle of the semiconductor device12. This configuration may be mirrored on the opposite side of the cover16as denoted by recess46and fastener opening48, symmetrically forming a generally teardrop shape with the tail extending towards the semiconductor device12. Other shapes for the recess may also be used, such as ovals or polygons, however the teardrop shape may provide improved support due to support by the head of the screw on one end and the converging tail lines on the opposite end. Although the cover12, as shown inFIGS. 3-5, is configured to accommodate two semiconductor devices, it is readily understood that multiple additional semiconductor devices could be accommodated by duplicating this arrangement in various additional locations along the cover16. Alternatively, a single semiconductor device may be accommodated in a single location on the cover16.

InFIG. 6, an example method100is provided for clamping a heat sink18to a semiconductor device12. The method starts in block101. The cover16may be formed from a sheet of metal through various stamping operations. In block102, one or more columns24may be formed in a surface of the cover16. At this stage, the column(s)24may resemble a strip parallel with the surface extending into an opening formed in the surface of the sheet. In block104, a button28may be formed in the surface of the sheet at a semiconductor device location. Further, if two columns are used, the columns24may be juxtaposed and the button28may be formed in between the two columns24. The button28may be formed by stamping a portion of the surface into a dome shape. Alternatively, slits may be stamped in the surface and a portion of the surface between the slits may be bent and/or stretched outwardly into a curved shape. Further, the top of the button may be formed into a flat surface that is configured to interface with a surface of the circuit board14or semiconductor device12. In block106, teardrop shape supports42may be formed in the surface of the cover. Openings44may be formed in the cover16to be aligned with the teardrop shape supports42as denoted by block108. In block110, a trench30may be formed in the surface of the cover16such that the columns24, the button28, and the supports42are located in the trench and generally protected by other extended surfaces of the cover16. In block112, the columns may be bent such that columns24extend away from the surface of the cover16. For example, the columns24may extend at approximately a 90° angle with respect to the surface of the cover16allowing the columns24to extend between the surface of the cover16and the heat sink18during later assembly steps. The semiconductor device12may be attached to a circuit board14as denoted in block114. In block116, a circuit board14may be attached to the cover16such that the columns24extend through the circuit board14upwardly around the semiconductor device12. The heat sink18may be attached to the semiconductor device12such that the columns24extend between the cover16and the heat sink18as denoted by block118. The heat sink18may be attached to the semiconductor device12utilizing fasteners20such as bolts that extend through openings42in the cover16and thread into the heat sink18. When the bolts20are tightened, the columns24provide a structural support acting to relieve the clamping force against the semiconductor device12. In this configuration, the button28and the teardrop shape supports42serve to support the circuit board14and semiconductor device12thereby reducing flex or stress imposed upon the assembly. The end of the method is denoted by block120.

InFIG. 7, another example of an electronic assembly210is provided. The electronic assembly210may include a semiconductor device212, a circuit board214, a heat sink218, and a cover216. The heat sink218may be provided to receive heat from the semiconductor device212. The electronic assembly210may also include a circuit board214such as a printed circuit board to which the semiconductor device212may be mounted. Traces on the circuit board214may provide electrical power as well as data signals and/or control signals to the semiconductor device212. A cover216extends about and protects a circuit board214and the semiconductor device212. The cover216may be formed from a sheet metal for example, through a series of forming or stamping events. The cover may be made from any rigid material, for example metal, plastic, or other similar material. The heat sink218may be clamped to the semiconductor device212using a fastener220. The fastener220is shown as a bolt. Although the fastener220may be threaded into the heat sink218as depicted inFIG. 1, alternatively, in any of the embodiments discussed, the fastener220may pass through a bore222in the heat sink218and be threaded into the cover216. Alternatively, the fastener220may extend through the cover216and be threaded into a nut on an opposite side of the cover216from the heat sink218.

The heat sink218may include columns224that extend around the semiconductor device212to absorb force from over clamping of the heat sink218by the fasteners220. In other alternative embodiments, the columns may be independent spacers extending between the cover and the heat sink. The columns224may extend through openings226in the circuit board214to contact the cover216. In particular, the columns224may contact buttons270formed in the cover216that also act to absorb over clamping of the heat sink218. Buttons270may include a first segment252of the cover216that extends angularly towards the heat sink218with respect to a planar region250of the cover that is generally parallel to the heat sink218. The button270forms a top surface254that is substantially parallel to the planar region250and aligned to interact with the column224of the heat sink218. Similar to the first segment252, button includes a second segment256that is angularly formed with respect to the planar region250and that extends between the top surface254and the planar region250thereby forming the button270.

The cover216may also include a button228aligned with the center of the semiconductor device212. The button228may be surrounded by a planar region250of the cover216. The button228may include a first segment230that extends angularly away from the integrated circuit212and that is connected to a planar portion232that is substantially parallel to the planar portion250of the cover216. The planar portion232may be connected to a second segment336that extends angularly toward the semiconductor device212, between the planar portion232and a planar surface238. The planar surface238may be substantially parallel to the planar region250of the cover216, as well as, the circuit board214and the semiconductor device212. Accordingly, the surface238is configured to interact with the circuit board214or the semiconductor device212through the circuit board214. In addition, it can be readily understood that the surface238may directly support the semiconductor device212as described in other embodiments provided below. The first segment230and the second segment236may cause a gap234to be formed between the cover216and the circuit board214. Similarly, a third segment240may extend angularly between the planar surface238and a planar segment244that is substantially parallel to the planar region250, similar to segment232. A fourth segment246extends between the planar segment242and the planar region250forming a gap244between the cover216and the circuit board214, similar to gap234. The segments of the button228act together as a deformable spring to absorb any over clamping force and prevent damage to the semiconductor device212.

InFIG. 8, another example of an electronic assembly310is provided. The electronic assembly310may include a semiconductor device312, a heat sink318, and a cover316. The heat sink318may be provided to receive heat from the semiconductor device312. A cover316may extend about and protect the semiconductor device312. The cover316may be formed from a metal sheet, for example, through a series of forming or stamping events. The cover316may be made from any rigid material, for example metal, plastic, or other similar material. The heat sink318may be clamped to the semiconductor device312using a fastener320. The fastener320is shown as a bolt that may be threaded into a bore322formed in the heat sink318. Accordingly, the fastener320extends through an opening in the cover316and engages the heat sink318. As mentioned, the fastener320may engage the heat sink318through a threaded engagement. Screws, rivets, clamps or any other fasteners may readily be used. In the bolt arrangement shown, providing increased torque on the fastener320generates additional clamping forces by compressing the semiconductor device312between the heat sink318and the cover316.

Loading columns324may extend from the cover316toward the heat sink318to absorb compression force if the semiconductor device312is cover compressed. The loading columns324and fastener arrangement may be provided at multiple locations around the semiconductor device312, for example on the opposite sides of the semiconductor device312to securely balance compression of the heat sink318against the semiconductor device312. In addition, a button328may be formed in the cover316to act as a spring between the cover316and the semiconductor device312to absorb forces that may otherwise over compress the semiconductor device312. Further, the button328may have a rounded or generally dome shape causing the bend of the sheet metal to act as a deformable spring. Further, the button328may include a flat top surface that contacts the semiconductor device312. As such, the cover316forms a planar surface and a button328extends from the planar surface and forms a second planar surface parallel to the first planar surface that reacts with the semiconductor device312. Further, the loading columns324also extend from the planar surface and may be formed substantially perpendicular to a planar surface. It is also understood that other deformable springs for example, leaf springs or coil springs may be used in place of the button328to absorb forces. However, the button328may be integrally formed in the cover316. The button328may act as a deformable spring to absorb any over clamping force and prevent damage to the semiconductor device312.

InFIG. 9, another example of an electronic assembly410is provided. The electronic assembly410may include a semiconductor device412, a first heat sink418, a second heat sink414, and a cover416. The first and second heat sink418and414may be provided to receive heat from the semiconductor device412. A cover416may extend about and protect the semiconductor device412. The cover416may be formed from a metal sheet, for example, through a series of forming or stamping events. The cover416may be made from any rigid material, for example metal, plastic, or other similar material. The first and second heat sink418,414may be clamped to the semiconductor device412using a fastener420. The fastener420is shown as a bolt that may extend through the first heat sink418and be threaded into a bore422formed in the second heat sink414. Accordingly, the fastener420extends through an opening in the cover416and engages the second heat sink414. In the bolt arrangement shown, providing increased torque on the fastener420generates additional clamping forces by compressing the semiconductor device412between the first and second heat sink418,414.

Loading columns424may extend from the cover416toward the heat sink418to absorb compression force if the semiconductor device412is cover compressed. The loading columns424and fastener arrangement may be provided at multiple locations around the semiconductor device412, for example on the opposite sides of the semiconductor device412to securely balance compression of the heat sink418against the semiconductor device412. In addition, a button428may be formed in the cover416to act as a spring between the cover416and the semiconductor device412to absorb forces that may otherwise over compress the semiconductor device412. Further, the button428may have a rounded or generally dome shape causing the bend of the sheet metal to act as a deformable spring. Further, the button428may include a flat top surface that reacts with the semiconductor device412through the printed circuit board414. As such, the cover416forms a planar surface and a button428extends from the planar surface and forms a second planar surface parallel to the first planar surface that reacts with the semiconductor device412. Further, the loading columns424also extend from the planar surface and may be formed substantially perpendicular to a planar surface. It is also understood that other deformable springs for example, leaf springs or coil springs may be used in place of the button428to absorb forces. However, the button428may be integrally formed in the cover416. The button428may act as a deformable spring to absorb any over clamping force and prevent damage to the semiconductor device412.