Apparatus and method for heat sink assembly

A heat sink assembly uses a pin and a spring arrangement to bias a heat sink against an underlying support with an electrical component in between. A lock cap, mounted on a head of the pin, selectively engages a retainer formed beneath an upper end of a heat dissipating element or fin of the heat sink to precompress the spring. When the lock cap is engaged and the spring is precompressed, the pin may be attached to the underlying support without opposing the force of the spring. When the attachment is complete and the lock cap is disengaged, the spring is allowed to act against the head of the pin and the base of the heat sink to operatively bias the heat sink against the underlying support.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to cooling for electrical components, and more particularly, to apparatuses and methods for providing thermal dissipation for electrical components using heat sink assemblies.

2. Discussion of the Related Art

Many electrical products today include discrete electrical components, such as semiconductor integrated circuits, which generate substantial amounts of thermal energy during normal operation. However, if the thermal energy is too great without adequate cooling, damage to the electrical component or product may result. In order to prevent such damage, a solution for thermal dissipation or cooling for the electrical component is typically necessary.

Known solutions for thermal dissipation typically include positioning a heat skink over the electrical component that generates the heat. Heat sinks generally are manufactured from a material having a high thermal conductivity and typically include a base with a series of heat dissipating elements or fins extending vertically upwardly from the base to maximize surface area. Air flow through the heat dissipating elements, with or without the assistance of a mechanical fan, operates to dissipate the thermal energy from the heat sink, and, in turn, from the electrical component.

To maximize thermal dissipation, it is often desirable to maximize the thermal contact between the heat sink and the electrical component. A variety of techniques may be used for maximizing such thermal contact, including applying an adhesive thermally-conductive layer between the heat sink and the electrical component, and/or using push pins, springs, clips and/or anchors to increase the force holding the heat sink to the associated electrical component.

However, implementing these techniques often require one or more limitations or tradeoffs. For example, a thermal adhesive layer alone may be insufficient to dissipate a desired amount of heat, and applying other elements may require consuming too much space in the electrical product. It is also difficult to hold the pins in the desired position producing tight contact of the heat sink against the electrical components while soldering the pins to the support because the springs force the pins and heat sink away from the support. As a result, pins often are soldered to the support in a position in which they are forced upwardly from their desired position and the downward pressing forces imposed by the springs are lower than desired or even non-existent. Thermal dissipation is substantially degraded as a result. Consequently, there is a need for an improved thermal dissipation solution that maximizes the amount of heat which may be dissipated while minimizing the amount of space required.

SUMMARY OF THE INVENTION

Aspects of the present invention provide a heat sink assembly using a pin and a spring arrangement to bias a heat sink against an underlying support with an electrical component in between. A lock cap, mounted on a head of the pin, retains the pin and spring in a lowered position with the spring pre-compressed. The lock cap selectively engages a retainer formed beneath an upper end of a heat dissipating element or fin of the heat sink. When the lock cap is engaged and the spring pre-compressed, the pin may be attached to the underlying support without opposing the force of the spring. When the attachment is complete, the lock cap can be disengaged, allowing the spring is allowed to act against the pin and the base of the heat sink to bias the heat sink against the underlying support with optimal force.

The retainer may be formed by a groove, ledge, or other horizontally extending structure in or on the heat dissipating element, and a retaining surface of the lock cap may selectively engage the structure by rotating into and out of engagement with the structure.

Specifically, one aspect of the present invention may include a heat sink assembly comprising a retaining pin assembly and a heat sink including a base and a plurality of heat dissipating elements extending at least generally vertically upwardly from the base. A retainer is associated with one the heat dissipating elements for selective engagement with the retaining pin assembly. The retainer is horizontally offset relative to an overlying portion of the at least one heat dissipating element. The retainer is configured to be selectively engaged by rotation of the head of a retaining pin assembly. Also, the base includes an opening that allows a portion of the retaining pin assembly to pass there through for connection to an underlying support.

The retaining pin assembly may include a pin having a head and, a body that passes through the opening of the heat sink. The retaining pin assembly may additionally include a spring that is disposed around the body of the pin and over the base of the heat sink. The spring is pre-compressed between the base and the head of the pin when the pin assembly engages the retainer on the heat dissipating element.

It is thus a feature of at least one embodiment of the invention to provide a mechanism in a heat sink suited to hold a spring in a greater compression state while a headed pin passing through the heat is attached to a board or other underlying support, such as by soldering. Then, after attachment, the spring may be released to a lesser compression state act between the head of the pin and the heat sink to increase the force biasing the heat sink against an electrical component located between the heat sink and the support.

A lock cap may be mounted on the head of the pin. The cap may have an at least generally horizontal-extending retaining surface extending in first and second directions, with the retaining surface being longer in the first direction than in the second direction. Rotation of the cap about a vertical axis thus moves the retaining surface into and out of engagement with a mating surface on or in the heat sink. The cap may be removable. It also may be sized to fit between the fins of the heat sink when oriented in a first manner, then rotated to engage the retainer of either fin when oriented in a second manner. Additionally, the cap may be integrated into the pin and not be removable.

Another aspect of the present invention may include a method of assembling a heat sink assembly. The method may comprise: (a) inserting a pin assembly having a head and a body between first and second heat dissipating elements and through a spring and an opening in the base the heat sink; (b) forcing the pin assembly downwardly to compress the spring; (c) while the spring is compressed, engaging a retainer on the heat dissipating element with a retaining surface of the pin assembly to hold the spring in its compressed state; (d), while the retaining surface on the pin assembly is engaged with the retainer on the heat dissipating element, attaching the pin to a PCB or other support structure disposed below the base of the heat dissipating element, such as by solder or the like; and then (e) disengaging the retaining surface on the pin assembly from the retainer on the heat dissipating element.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now toFIG. 1, an exploded perspective view of a heat sink assembly10, shown in an exemplar system with an electrical component12that is mounted to an underlying support14, is provided in accordance with an embodiment of the invention. The heat sink assembly10includes one or more retaining pin assemblies16, and a heat sink18. The heat sink assembly10is positioned over the electrical component12, which is a heat generating component such as a packaged semiconductor integrated circuit or other element. The electrical component12is mounted to the underlying support14, which may be a Printed Circuit Board (PCB) or similar substrate, such as by wave soldering. A thermal adhesive layer or thermal pad (not shown) may also be provided between the heat sink assembly10and the electrical component12.

Still referring toFIG. 1, each retaining pin assembly16may comprise a pin20or other longitudinal structure having a head22and a body24. A lock cap26may be mounted on the head22of the pin20such that the lock cap26is rotatable or otherwise movable relative to the pin20. The lock cap26may be mounted simply by resting the lock cap26on the head22. Specifically, as best seen inFIGS. 4A and 4B, the lock cap26may have a recess27that extends vertically upwardly from the bottom surface of the lock cap26so as to be insertable over a post29that protrudes upwardly beyond the head of the pin. In its operative position or engagement shown inFIG. 4Bin which the lock cap26engages retaining elements44aand44bon the heat dissipating elements as detailed below, the lock cap26is clamped between the retaining elements44aand44band the head22of the pin. The lock cap26can be rotated from its disengaged position ofFIG. 4Ato its engaged position ofFIG. 4Bby engaging a groove49in the top of the lock cap26, best seen inFIGS. 5 and 6, using a screwdriver or the like. It should be noted that that the lock cap26alternatively could be retained on the pin20using a snap a ring or other secure arrangement. In addition, the lock cap26may provide an at least generally horizontal-extending retaining surface28, which may be a flange or rib, extending in first and second direction, and the retaining surface28may be longer in the first direction than in the second direction. Also, the body24of the pin20may pass through a biasing mechanism such as coil spring30which is capable of resiliently biasing the heat sink18against the component12in order to enhance thermal contact therebetween.

The heat sink18may comprise a base32and a plurality of heat dissipating elements34, which may be fins, extending at least generally vertically upwardly from the base32. The heat sink18may be manufactured from metal or another material having a high thermal conductivity and may be designed such that air flowing through the heat dissipating elements34dissipates thermal energy from the heat sink18, and, in turn, from the electrical component12. As shown in a cutaway area36, the base32may also include one or more openings38(four such openings38are provided in the vicinities of the corners of the rectangular heat sink18in the illustrated embodiment). The heat dissipating elements34may be spaced further apart in regions flanking the openings38the heat sink openings38and the pin assemblies16. Each opening38is configured to allow a portion of the body24of a corresponding pin assembly16to pass therethrough for connecting to the underlying support14. Consequently, the underlying support14may also include one or more support openings40, each of which substantially aligned with an opening38in the heat sink18, for receiving the body24of the pin20.

At least one of the heat dissipating elements34adjacent to each opening38also includes a retainer44located beneath an upper end of the respective heat dissipating element34. In the illustrated embodiment, facing retainers44are provided on both heat dissipating elements34that flank each heat sink opening38. The retainer44provides selective engagement with the retaining pin assembly16. The retainer44is horizontally offset relative to an overlying portion of the respective heat dissipating element34, and is configured to be selectively engaged by the retaining pin assembly16, such as by the lock cap26. The retainer44may be a groove formed in the heat dissipating elements34, which can be easily formed during fabrication of the heat sink18. Alternatively, other retaining configurations may be similarly provided, such as a ledge or shoulder extending outwardly from the heat dissipating elements34.

In operation, the lock cap26may selectively engage with retainer elements44aor44bprovided by one or more of the heat dissipating elements34. When the lock cap26is engaged, the coil spring30is pre-compressed between the head22of the pin20and the base32of the heat sink18. Next, the body24of the pin assembly16, which in this position passes through the heat sink opening38, and is aligned with the support opening40, may be connected to the support opening40, such as via wave soldering, without having to oppose the biasing force that otherwise would be imposed by the coil spring30. Finally, the lock cap26may be disengaged, such that the coil spring30is released and permitted to compress between the head22of the connected pin20and the base32of the heat sink18. As a result, the coil spring30operates to force the heat sink18onto the electrical component12using a minimal amount of space.

Referring now toFIG. 2, a side view of the heat sink assembly10, in communication with the electrical component12that is mounted to the underlying support14, before engagement of the retaining pin assembly16to the retainer44, and before attachment of the pin20to the underlying support14, is provided. The lock cap26may be mounted to the head22of the pin20. The body24of the pin20may pass through the coil spring30through the heat sink opening38in preparation for connection to the support opening40. A thermal adhesive layer or thermal pad46may be provided between the heat sink assembly10and the electrical component12for maximizing heat transfer between the electrical component12and the heat sink18.

Referring now toFIG. 3, a side view of the heat sink assembly10is shown following attachment of the heat sink assembly10to the underlying support14and while the lock caps26are still engaged with the retainers elements44aand44b. The coil spring30is pre-compressed between the base32of the heat sink18and the head22of the pin20due to engagement of the lock caps26with the associated retainers elements44aand44b. Due to this precompression, spring forces are no longer available to bias the pin assemblies16out of the heat sink openings38. As a result, the body24of each pin can be attached to the underlying support with while being located at a position in which the spring can provide a good biasing effect, but without having to overcome opposition from the spring forces during the attachment process. In a preferred embodiment, the connection48could be made by solder, though other forms of connection/attachment could be provided within the scope of the invention.

Referring again toFIGS. 4A and 5, detailed side and plan view of the lock cap26of a pin assembly16, mounted on the head22of the pin20, and positioned in proximity to retainers elements44aand44bof respective heat dissipating elements34aand34b. The retainer elements44aand44hare shown disengaged from the retaining surface28of the lock cap26, which could correspond to a period of time before or after forming the connection48between the body24of the pin20and the support opening40as described above with respect toFIG. 3. The lock cap26may be substantially rectangular in shape so that the retaining surface28of the lock cap26is shorter in a second direction28athan in a first direction28b. With the retaining surface28shorter in the second direction28athan the separation distance between the adjacent heat dissipating elements34aand34b, the lock cap26can be placed into position between the adjacent heat dissipating elements34aand34b. As a result the retaining surface28is fully disengaged from the retainers elements44aand44hwhen the lock cap26is in the position shown inFIGS. 4A and 5. Moreover, in this configuration, the retaining surface28fits between the space provided by the adjacent heat dissipating elements34aand34b. With the retaining surface28longer in the first direction28bthan a separation distance between the adjacent heat dissipating elements34aand34b, the lock cap26can engage the retainer elements44aand44b.

Referring now toFIG. 4B, a detailed side view of the retainers elements44aand44bshown fully engaged with the retaining surface28of the lock cap26of a pin assembly16is provided, which could correspond to a period of time during forming of the connection48between the body24and the support opening40as described above with respect to Fig. The lock cap26may rotate clockwise or counter-clockwise from a first position, as shown inFIG. 4A, to a second position, as shown inFIG. 4B, for transitioning between the disengaged and the engaged positions. As discussed above, this rotation may be accomplished, for example, by applying a screw driver or other tool to the groove49disposed over the lock cap26. As the retaining surface28of the lock cap26is longer in the first direction281) than in the second direction28a, the retaining surface28is fully engaged with the retainers elements44aand44b, and the coil spring30is held pre-compressed between the lock cap26and the base32of the heat sink18.

In alternative embodiments, other shapes for the lock cap, and/or other configurations for the retainers, may be used. For example, the lock cap may be asymmetrical with only one side longer than any other side. Also, only a single retainer may be used, which could be a groove, a ledge, or otherwise, and which could be provided in a limited area (in proximity to the aligned openings of the heat sink and the underlying support) or provided along an entire length of the respective heat dissipating element. Another possible embodiment is provided inFIG. 6, in which an ovoid lock cap60is positioned in proximity to retainers elements62aand62bof heat dissipating elements64aand64b, before engagement therebetween. In addition, in this embodiment, the retainers elements62aand62bmay be limited length grooves in the heat dissipating elements64aand64b. Accordingly, it will be appreciated that a variety of retention techniques may be used within the spirit of the present invention.

Referring now toFIG. 7, a side view of the heat sink assembly10, as described above with respect toFIGS. 1-4, illustrates the completed assembly after removal of the lock caps26. Here, with the connection48complete, the lock cap26of each respective pin assembly16is disengaged from its associated retainer elements44aand44b, and the coil spring30is allowed to act between the head22of the pin20and the base32of the heat sink18without acting on the heat dissipating elements34. The pin20is also fixed in position at this time due to its connection to the underlying14by the soldered connection48. Accordingly, the heat sink18is biased against the underlying support14, thereby applying an optimal amount of force for transferring heat from the electrical component12to the heat sink18. The lock caps26, having been rotated to their disengaged positions, can now be removed and reused or discarded.

Referring now toFIG. 8, an exemplar flowchart illustrating a method of assembling a heat sink assembly is provided in accordance with an embodiment of the invention. In this process block, a pin having a head and a body may be inserted through a coil spring and an opening in the base of a heat sink at blocks70. Next, in process block72, a pin assembly, which includes the pin and a retaining surface, may be forced downwardly to compress the coil spring between the head of the pin and the base of the heat sink. The retaining surface may be located, for example, on a lock cap located above the head of the pin as described above.

Next, in process block74, while the coil spring is compressed, the retaining surface is moved into engagement with the mating retainer on the heat dissipating element to hold the coil spring in its compressed state. Engaging may comprise, for example, rotating a lock cap located above the head of the pin from a first position in which the retaining surface is spaced from the retainer to a second position in which the retaining surface engages the retainer. Also, the retainer may be formed on a surface of a first heat dissipating element, and may face another retainer that is formed on a second heat dissipating element. In this case, the retaining surface on the pin assembly may effectively engage both retainers.

Next, in process block76, while the retaining surface on the pin assembly is engaged with the retainer on the heat dissipating element, the pin is attached to an underlying support disposed below the base, such as by soldering the pin to a PCB. Finally, in process block78, the retaining surface on the pin assembly is disengaged from the retainer on the heat dissipating element such as by rotating the lock cap from the second position to the first position. As a result, the heat sink is biased against the underlying support with the electrical component in between.