Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – Insulating material
Reexamination Certificate
2004-02-17
2004-12-07
Vu, Hung (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
Insulating material
C257S706000, C257S717000
Reexamination Certificate
active
06828673
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention applies primarily to solid-state electronic components and more specifically to attaching heat sinks to those components in order to control the damaging effects of heat generated by solid-state components during operation.
It is widely known that many solid-state electronic components, including microprocessors, generate excess heat during operation. That heat poses a serious threat to their performance and can result in the failure of such devices or neighboring components. As electronic devices inevitably become smaller, the cumulative effect of heat from neighboring components becomes a greater concern. In order to control the heat, devices such as cooling fans and heat sinks are commonly employed.
Attaching heat sinks to solid-state components has been achieved in a variety of ways with advantages and disadvantages to each method. Permanently adhering the heat sink to the electronic component generally ensures a good initial thermal interface, but with vibration and the passage of time, the bonds tend to deteriorate with degenerating effects on heat dissipation. Permanent bonding also precludes re-use and is impractical or impossible in many applications.
Using a secondary device, commonly known as a clip or adapter, is another popular way to attach heat sinks. Clips exist in a wide variety of designs ranging from single piece units to multiple part assemblies. They generally incorporate L-shaped legs to slide or slip over the electronic device package and then use a variety of methods to secure the heat sink. Clips can be cost effective ways to attach heat sinks to solid-state electronic components, but current designs have inherent problems.
One popular design as shown in U.S. Pat. No. 5,313,099 attaches the heat sink to the clip with a threaded coupling and uses the pressure of screwing down the heat sink against the electronic device package to secure and attach the heat sink to the clip assembly. The big advantage of this design is that this design provides initial adjustability for different thicknesses of electronic device packages. A thicker or thinner device package is accommodated by simply screwing the heat sink into the clip until the heat sink engages the solid-state component. However, this method requires substantial pressure between the contact surface of the heat sink and solid-state component to keep the heat sink from vibrating loose. The required pressure exceeds some solid-state electronic component manufacturer's specifications that can result in damage or destruction of the device. Even when all specifications are met, this method of attachment will still occasionally unscrew with potentially catastrophic consequences to thermal performance and neighboring components. Further, installation by this method requires torque sensitive tools, technicians trained in the proper use of those tools and the inherently time consuming process of properly aligning very finely threaded components. All these factors result in a costly installation process. Manufacturing and inspecting the very finely threaded heat sinks required in this design is also expensive. Finally, this design does not compensate for component expansion and contraction caused by the heat generated during operation. This expansion and contraction can cause the heat sink/clip assembly to unscrew or pop off the electronic device package with obviously damaging effects.
Another connection system proposed by U.S. Pat. No. 5,313,099 is to provide the attachment base of the heat sink with a tapered flange adapted to be forced through a bore in the clip until the radially extending lip of the flange snaps into a recessed area of the clip so as to secure and attach the sink to the clip. Although this snap fit attachment concept has not been commercialized, this concept would not provide for the effects of expansion and contraction of the heat sink clip assembly as with the threaded attachment base mode above discussed.
Accordingly, there is a need to provide a connection mechanism such that heat sinks of the aforementioned general type can be attached to the clips which in turn connect with and position the electronic device for effective heat transfer contact with the heat sink that compensates for component expansion and contraction.
Accordingly, the main object of the present invention is to provide an easy to install and inexpensive to manufacture heat sink and clip assembly which provides a secure reusable thermal coupling between a heat sink and a solid-state component for the purpose of dissipating heat and that will also compensate for expansion/contraction effects on thermal interfaces experienced during operation. The invention will achieve its purpose without exerting excessive force against solid-state components and will provide adjustability for varying thicknesses and pressure requirements of electronic device packages.
SUMMARY OF THE INVENTION
In a first embodiment of the invention, a heat sink is created with a base having a tapered initial lower surface and a contiguous upper and inversely tapered secondary or working surface. The two thus oppositely tapered surfaces of the heat sink base form a connecting flange or edge which connection defines the largest portion of the base. The heat sink is then inserted into an adaptor (clip) having an opening through which the heat sink base is inserted to form a working connection with the clip. The periphery of the clip opening is of the same shape and approximate size (e.g., diameter) as the heat sink base and is provided with a flexible radiused contact surface. The lower initial surface of the heat sink base by reason of its aforementioned taper presents a lesser dimension (diameter) such that as the heat sink is pushed into the clip the initial tapered base affords easier connectivity. Once the connection edge of the heat sink base is forced past the edges of the clip opening, operative connection between the heat sink and clip is achieved, and the flexible radius contact surfaces bear against the secondary working surface of the heat sink base.
The heat sink may be of radial fin, pin fin or other design as required by the application, and the clip's receiving opening will reflect the required heat sink's base whether the shape be square, round of other geometric shape. The clip may be attached to the electronic device package by opposing L-shaped legs protruding below the clip's heat sink receiving surface. The heat sink is then secured to both the clip and electronic device package by inserting the heat sink it through the clip's receiving opening where the beat sink is held in place by the force of the clip's flexible receiving collar exerting horizontal force against the heat sink's incline plane working surface which results in a downward vertical force component being exerted against the heat sink towards the solid-state component thermal interface surface and vertical force exerted against the clip's L-shaped legs to the under side of the electronic device package.
The amount of force required to secure the heat sink/clip assembly to an electronic device package is controlled for differing applications by changing the angle of the heat sink base's incline plane and/or changing the flexibility of the clip's receiving collar. The flexibility of the clip's receiving collar riding against the heat sink's incline plane allows the heat sink to travel vertically for a predetermined distance without significantly changing the pressures between the thermal interface surface, the clip's legs to the electronic device package or, finally, the heat sink to the clip. The properties of the clip's flexible retaining collar riding against the heat sink's incline plane also virtually eliminates the damaging effects of vibration and heat expansion/contraction to the thermal interface.
Numerous advantages to the invention's application, manufacturing and installation become self evident in the detailed description and drawings su
Ficorilli John
Gruner Stephen
Doherty Robert J.
Vu Hung
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