Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-09-13
2002-03-12
Thompson, Gregory (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C024S458000, C248S510000, C257S719000, C361S710000, C361S719000
Reexamination Certificate
active
06356446
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention (Technical Field)
The present invention relates to cooling of electronic assemblies.
2. Background Art
With the introduction of integrated circuits (ICs), there has been a steady progression toward larger and more complicated IC devices to permit the inclusion of a greater number of functions on the IC. With larger ICs having more circuitry, more heat is produced that is not adequately removed by natural air convection alone nor by powered ventilation, such as a fan.
A heat sink is a device that preferably has a relatively high rate of thermal conductivity and high heat capacity. Because of the material properties of the heat sink and its design, a heat sink can draw heat from any closely situated heat source and dissipate that heat into the surrounding environment. The heat that is generated by ICs must be removed from the area of operation, or else the IC can be ruined.
Convection cooling is performed by the use of a heat sink that is directly applied to the device. It is not desirable to use a bonding process, such as an adhesive, because of the permanent nature of such attachment; an IC may be discarded if malfunctioning and it is not desirable to throw away the heat sink as well as the IC. It has therefore been found beneficial to attach a heat sink to the IC by mechanical means, such as a retainer clip. The typical heat sink in current use comprises a flat plate, generally of the same size as the device, with a plurality of radiation fins extending upwardly. The heat sink is commonly fabricated from aluminum and is extruded and subsequently machined.
A parallel development in the electronic assembly art has been the provision of means for detachably securing large and generally expensive IC devices to a printed circuit board. By detachably securing these expensive ICs, they can be easily removed and repaired when one part of the device becomes damaged or is inoperable. This eliminates the need for fixing the device while it is attached to the printed circuit board, removing the device with possible damage to the sensitive pins, or throwing away the entire IC and printed circuit board. Typically, the industry uses sockets for detachably securing ICs to printed circuit boards. Sockets are permanently attached to the printed circuit board through soldering of downwardly-extending contact pins. These sockets for semi-conductor devices are typically standardized for various ICs and/or IC families.
Recently, however, a new low-cost microprocessor module has been developed that will be used instead of a socket. The microprocessor module consists of the microprocessor IC that is soldered to a small printed circuit board, which is in turn detachably secured to the larger printed circuit board.
To facilitate the proper attachment of the heat sink to the microprocessor module and associated printed circuit board and microprocessor, the printed circuit board within the module is provided with holes that correspond to holes through the plate of the heat sink, through which a retainer clip is inserted. The retainer clip then secures the heat sink to the bottom of the printed circuit board, and at the same time secures the microprocessor module in tight engagement with the heat sink.
Heat sinks to be used with microprocessor modules and printed circuit boards may be of various constructions, but all heat sinks are fabricated or formed from a material with high thermal conductivity, such as aluminum. Heat sinks include a plate with a flat bottom surface. The plate is generally rectangular and its size is co-extensive with the size of the entire device, which includes the printed circuit board and microprocessor module. The heat sink has a large number of fins that are integral with the plate and formed from a single extrusion. In the central region of the heat sink, the fins are machined away to create a channel that extends across the plate.
The heat sink is retained on the entire device by a resilient retainer clip that biases the heat sink into tight thermally conductive relation to the device. That is, the lower surface of the plate is forced against the upper surface of the device.
Prior art heat sink and retainer clip devices are disclosed in U.S. Pat. No. 5,600,540 to Blomquist, entitled “Heat Sink and Retainer for Electronic Integrated Circuits;” U.S. Pat. No. 5,396,402 to Perugini, et al., entitled “Appliance for Attaching Heat Sink to Pin Grid Array and Socket;” and in U.S. Pat. No. 5,208,731 entitled “Heat Dissipating Assembly.” U.S. Pat. No. 5,208,731 discloses an assembly for heat dissipation using a spring clip which cooperates with tabs or lugs on opposite side walls of a socket to retain a microprocessor or other IC. U.S. Pat. No. 5,396,402 discloses the use of a clip, which includes a leaf spring and two plastic clips, to be used specifically with a pin grid array chip and pin grid array socket. U.S. Pat. No. 5,600,540 discloses a heat sink and retainer clip to be used with a rectangular socket having opposing side walls, wherein at least two of the side walls have lugs projecting laterally outward. That particular retainer clip is constructed in two pieces; one of which is an elongated strap having a bent portion that bears down upon the heat sink, and another that is rotatably mounted on the end of the first which, when forced down and rotated inward, hooks an opening onto a lug. These prior art devices are made differently and operate differently from the present invention.
The present invention is a simple design to be used with microprocessor modules or any electronic device to be retained against a heat sink, and has the added benefit of producing an evenly-distributed load across the printed circuit board, and microprocessor, during and after installation. The present invention has a flexible slotted rail and pin configuration and a handle for the user to pull back and forth to install and remove the clip.
SUMMARY OF THE INVENTION (DISCLOSURE OF THE INVENTION)
The present invention is a heat sink retainer clip for biasing an electronic device mounted on a printed circuit board within a housing and a heat sink into heat transfer engagement. The clip comprises at least one rail supported on the housing; at least one pin to be inserted through registered openings in the heat sink, printed circuit board, and housing; a slot in at least one of the rails for receiving the pin; and a handle for positioning the clip relative to the heat sink, printed circuit board, and housing from a first relaxed position to a second biasing position. The pin or pins of the clip preferably comprise a body, a base at one end of the body to abut the heat sink, a spacer at the middle of the body to maintain an approximate fixed distance between the electronic device and the heat sink, and a bulb at the opposite end of the base of the body extending through the slot in the rail to abut the slot when the clip is in the biasing position. Preferably, each pin is comprised of thermoplastic. Preferably, the handle is connected between two corresponding ends of the rails. The rails have at least one arched portion which produces a biasing force and at least one flat portion connected to the arched portion that is in contact with the housing. Preferably, the arched portion produces a biasing force of between approximately 10-20 pounds. The slot in the rail preferably has a registered hole for initially receiving the pin. Preferably, the slot is located so that the end of the slot opposite the registered hole is located at the highest point of the arched portion. The clip is preferably made of resilient stamped metal.
In a preferred embodiment, the heat sink retainer clip is comprised of two rails supported on the housing; four pins to be inserted through registered openings in the heat sink, printed circuit board, and housing; four slots in the two rails which receive the four pins; four holes through the two rails, and adjacent to the four slots, corresponding to the four pins to initially receive the pins; and a handle for positioning the cl
Mays Andrea L.
PSC Computer Products, Inc.
Thompson Gregory
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