Heatsink Assembly for a High-Power Device

This invention relates in general to heatsink mechanisms and more particularly to a heatsink assembly for dissipating heat from an electronic component.

Electronic products such as two-way radios invariably contain electronic components, such as integrated circuit (IC) packages, mounted to printed circuit substrates. The substrate assembly is usually located within an inner cavity of a product housing. In operation, individual circuits on an IC generate heat, effecting an increase in the temperature of the IC. In an effort to improve performance, cost and reliability, there has been a trend toward the packaging of greater numbers of circuits in ever smaller spaces. Therefore, although the average power per circuit has been steadily decreasing with time--because of improvements in device and circuit technologies--increased circuit density and the growing total number of circuits per system have resulted in a continual increase in power and power density requirements. Semiconductor elements which are sensitive to temperature increases, e.g., transistors and diodes, may malfunction under excessive temperature; negatively impacting the operation of the circuit. In extreme cases, complete circuit failure may result. To avoid the deleterious effects of heat on IC functionality, it is desirable to maintain the junction temperature of the IC below a predetermined value. A common means of maintaining the chip temperature below such a predetermined value comprises removing heat away from the IC and the package using a heatsink.

A variety of heat sinking methods are known for dissipating heat away from electronic components. For instance, some IC packages incorporate thermally conductive heat sinks or heat fin structures bonded on the back side of the package or chip itself. Sometimes, this means of heat sinking will suffice. However, some devices, such as high-power transistors, generate excessive heat requiring greater heat dissipation. For such devices, additional heat sinking is required. For example, a high power transistor package often has an integral metal heatsink extending from the package. The heatsink has a hole which is used to mechanically fasten the heatsink, e.g., with a screw, to a nearby object having a large thermal mass. In instances where it is not feasible to directly attach the package heatsink to the thermal mass, a thermally conductive interposer may be employed; one end attached, e.g., clipped on, to the package heatsink, the other end mechanically fastened to the thermal mass. Mechanical fasteners ensure that sufficient contact pressure is maintained between the second end of the interposer and the thermal mass; in turn, ensuring sufficient thermal conduction away from the electronic component. However, the addition of mechanical fasteners to product designs is undesirable. Historically, manufacturers have driven toward product designs which eliminate the use of mechanical fasteners, since they tend to increase cycle time and cost, while decreasing product reliability.

For the foregoing reasons, it would be desirous to have a means for providing additional heat sinking in products incorporating high-power electronic components, while eliminating the need for additional mechanical fasteners.

The sole FIGURE provided is an exploded view of a heatsink assembly in accordance with the present invention.

While the specification concludes with claims defining the features of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the following description in conjunction with the drawing figure.

Referring now to the FIGURE, a heatsink assembly 100 is shown for providing additional heat dissipation to an electronic component 102 contained within the housing 130 of a product having an internal loudspeaker 120. The electronic component 102 is provided upon a printed circuit substrate 101. A heatsink 104 extends from the electronic component 102. Although we envision a high-power integrated circuit (IC) package, such as a high-power transistor, the instant invention is applicable to other types of electronic components having an attached heatsink and requiring supplemental heat dissipation, i.e., in addition to the heat dissipated by the heatsink 104 alone. One skilled in the art will appreciate that there are myriad types of electronic components incorporating a wide variety of heatsink styles (e.g., see the 1995 Newark Electronics.RTM. catalog, pp. 231-234). Typically, heatsinks are manufactured from a thermally conductive metal such as aluminum. Alternatively, metal-filled polymer composites are sometimes employed. During circuit operation, component-generated heat must be dissipated to prevent damage to sensitive circuitry; the heatsink 104 acts as a thermal path away from the IC.

The heatsink 104 is attached to the first end 108 of a thermally-conductive interposer 106. Preferably, the first end 108 has a shape which is conductive to frictional coupling with the heatsink. By "frictional coupling" we mean that the first end 108 fits so tightly over the heatsink 104 that a sufficient contact force is achieved without the need for any additional fastening mechanisms, e.g., mechanical or adhesive. For instance, where a transistor-like package having a rectangular-shaped heatsink is being coupled to, it would be preferable to have a U-shaped first end which fits snugly over the outer surface of the heatsink; direct and intimate contact between the first end 108 and the heatsink 104 ensuring efficient conduction of heat from the heatsink to the connector. Clip-on and snap-on type friction mount heatsinks are well known in the art. Regardless of the heatsink shape, the first end 108 of the interposer 106 should mate with the heatsink such that there is sufficient contact force between the first end and the interposer.

The interposer 106 has a second end 110 which magnetically couples to the rear surface 123 of a loudspeaker magnet 122, precluding the need for separate mechanical fasteners used in prior art connector mechanisms. Magnetic coupling is achieved by manufacturing the interposer 106 from a material which is magnetically attracted to the magnet, i.e., a ferrous metal or alloy thereof. Preferably, the interposer 106 is stamped and formed from a single piece of ferrous metal, e.g., a metal sheet. The thickness of the metal piece or sheet will vary depending upon thermal conduction requirements for a particular application. Magnetic attraction between the second end 110 of the interposer 106 and the speaker magnet 122 is a critical feature of the invention, providing sufficient contact force without the need for mechanical fastening devices. To maximize heat conduction from the interposer 106 to the loudspeaker magnet 122, it is preferable that the second end 110 of the interposer has a surface which lies flush with the rear surface 123 of the speaker magnet 122 when the two surfaces are magnetically coupled. For instance, where the rear surface 123 of the speaker magnet 122 is planar--which is generally the case--the surface of the second end 110 which magnetically-couples to the rear surface 123 should also be planar. An alternate embodiment of the invention incorporates integral mounting tabs 111 which extend away from, and perpendicular to, the second end. The mounting tabs 111 provide added mechanical stability, preventing the second end 110 of the interposer 106 from sliding off of the rear surface 123 of the magnet 122.

While the preferred embodiments of the invention have been illustrated and described, it will be clear that the invention is not so limited. Numerous modifications, changes, variations, substitutions and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims. For instance, a variation of the present invention could incorporate an interposer having a plurality of first ends for contacting a plurality of package heatsinks. Furthermore, although we envision the magnet of the present invention being provided by an internal loudspeaker, clearly magnetic attraction may be provided by alternate structures having an integral magnet, e.g., an electronic motor.