Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2002-12-23
2004-08-03
Thompson, Gregory D. (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C211S041170, C062S259200, C165S080200, C165S080300, C165S185000, C174S016100, C174S016300, C361S707000, C361S719000, C361S721000
Reexamination Certificate
active
06771504
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to the field of broad electronic technology (BET), and in particular to thermal management for wedge-lock mounting into card cages. More specifically, the invention relates to a method for improving the cooling path from the heat sink on the circuit board to the card cage chassis.
BACKGROUND OF THE INVENTION
It is well known in the field of electronic technology that overheating electronic assemblages containing heat generating components, such as processors, transistors, diodes etc., contributes to reducing the life of the component or module as well as the overall reliability while in service. As electrical assemblages or products containing such components become denser and contain components that have higher wattages per square area, component overheating becomes a larger problem as well as a limiting factor in the reliability of the electrical assemblage. Thus, eliminating or substantially reducing the heat from such components during service must be accomplished before product reliability can be greatly improved. The performance and reliability of commercial electronic products are limited by the inability of the products to dissipate heat generated by densely packed electrical components. Moreover, a related problem in the electronic art involves circuit boards configured in a card cage. It is known that limited progress has been made in the art for removing heat from such electrical assemblages.
Prior art attempts to address the aforementioned problems have met with limited success. Some artisans have taken advantage of the heat sink positioned on one side of the circuit card/board and the thermal path between the heat sink to the slot of the card cage. Since this is a relatively small area, it is generally deemed to offer limited opportunities for making this an effective and cost effective heat transfer location. Moreover, it is well known that heat dissipation through the wedge lock securing the circuit board has been improved over the last 10 years with changes in the construction and materials of the wedge-lock. However, it is also well known that there remains a considerable challenge in making this an effective means of improving the heat transfer from the electrical assemblage. Hence, most of the heat does not transfer through the wedge-lock, but through the back side of the board or the heat sink. To improve layout area, the heat sink has become more open with cutouts. This technique is known to reduce the stiffness of the assembly, which reduces the resonant frequency. To increase the frequency, ribs (both horizontal and vertical) are often added to the heat sink. With a rib of the heat sink aligned with a wall of the wedge-lock, increased thermal path area is now available at the “edge” of the assembly. The associated problem is the air gap between the circuit card/board and the bottom of the receiving slot.
Other prior art attempts to address the aforementioned problem has resulted in varying degrees of success. In the area of commercial electronics, such as computer electronics, the most common solution is to utilize costly component constructions. In the automotive electronic area, costly circuit board materials are generally used to reduce component overheating.
Therefore, there persists a need in the art for an electronic assemblage that operates at considerably cooler junction and board temperatures. Further, there is a need for a cost effective method of reducing the heat generated by hot components in electronic assemblages under high and ordinary service loads.
SUMMARY OF THE INVENTION
The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the present invention, a method is disclosed for transporting heat from an electrical assemblage. A retaining unit (card cage) securely retains the electrical assemblage and wedge lock. A heat sink is arranged in fluid communication with both the electrical assemblage and the wedge lock such that a rear wall of the wedge lock and a side wall of the heat sink form a coplanar thermal wall. The coplanar thermal wall is spaced apart from an interior wall of said retaining unit to form a thermal gap therebetween. A heat transfer element is disposed in the thermal gap such that at least a portion of the heat transfer element contacts at least a portion of the coplanar thermal wall and the interior wall of the retaining unit for transporting dissipated heat therebetween.
The present invention has numerous advantages over prior art developments. More particularly, the electronic assemblage of the invention operates at lower temperatures and is, therefore, more reliable. Further, the electronic assemblage can allocate space in proximity to the heat-generating element for specific electrical traces essential for the design layout. Furthermore, the electronic assemblage of the invention may contain a larger number of standard and thinner width size components.
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Bailey, Sr. Clyde E.
Eastman Kodak Company
Thompson Gregory D.
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