Circuit board and computer system for enhanced cooling

Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices

Reexamination Certificate

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Details

C361S752000

Reexamination Certificate

active

06198629

ABSTRACT:

BACKGROUND
1. Field of the Present Invention
The present invention generally relates to the field of computers and more particularly to a circuit board design for enhanced cooling in a computer system.
2. History of Related Art
Computer systems including personal computers, servers systems, and enterprise systems are universally prevalent in a vast assortment of business, scientific, commercial, and home applications. The thermal generation characteristics of the semiconductor technology that drives essentially all computer systems have been well documented and heat dissipation in computer systems has been a design and manufacturing concern from the inception of the industry.
Several emerging trends in computer design have heightened the need for efficiently dissipating heat in computer systems. Among these trends, the desire to increase the number of features packaged within a given system by increasing the number of expansion or I/O cards connected to the system, the desire to decrease the size of the computer system chassis or box, and the ever increasing power dissipated by the emerging generation of I/O cards due to increased functionality and performance, have all resulted in unprecedented levels of thermal generation.
Accommodating more I/O cards without increasing the chassis dimensions results in decreased spacing between adjacent I/O cards. The reduced spacing translates directly into reduced air flow between adjacent cards and hence higher component temperatures. Typically, I/O cards are inserted into an expansion board or planar that either connects to or is an integral part of the computer system's processor board or motherboard. The expansion board includes multiple connectors for attaching I/O cards. Frequently, the problems of adequately dissipating the heat generated by the I/O cards is in part a result of the poor air flow that is characteristic of certain regions of the I/O cards. Typically, the region of the I/O card proximal to the corner formed by the rear face of the chassis and the planar has poor air flow. As the connector pitch in these planars decreases and/or the functionality and performance of the I/O cards increases, the heating problem of providing adequate air circulation to remote portions of I/O cards increases.
Inadequate heat dissipation on computer systems detrimentally affects system performance and reliability. As the temperature of the semiconductor components of the system increase, the speed at which the devices operate decreases. If the temperature increases beyond a specified threshold, the devices may experience temporary or permanent thermal breakdown. Typically, air moving devices (AMD's) such as fans or blowers are introduced into the computer system to increase air flow and to maximize heat dissipation. As board-to-board spacing or pitch continues to decrease, however, the benefit achieved by adding more AMD's or higher speed AMD's into the computer system is reduced. Additionally, it is desirable to minimize the use of AMD's in a computer system because each AMD consumes valuable space that could otherwise be dedicated to system electronics, increases system cost, and undesirably increases the system noise level. Accordingly, it is highly desirable to provide for an enhanced cooling method that addresses the greater challenges presented by densely spaced higher performance I/O cards required in present day systems without significantly increasing system cost and without significantly decreasing system performance or reliability.
SUMMARY OF THE INVENTION
The problems identified above are in large part addressed by a computer system employing a circuit board designed to facilitate air flow in regions of the I/O cards that would otherwise receive little air flow. Broadly speaking, the present invention contemplates a computer system including a chassis, an expansion board, and an AMD. A CPU that includes one or more processors may be housed within the chassis. Preferably, the chassis has a substantially rectangular cross section suitable for receiving the expansion board. A rear face of the chassis includes upper and lower exhaust ports. The expansion board includes an upper and lower surface and is suitable for receiving a plurality of expansion cards via connectors attached to the upper surface. The expansion board may be coupled to a CPU board and is housed within the chassis and positioned such that a rear side of the expansion board abuts or is located proximal to an interior surface of the rear face of the chassis between the upper and lower exhaust ports. The expansion board further includes one or more holes or voids for facilitating air flow. The AMD is positioned within the chassis for directing air flow across the expansion board toward the rear face of the chassis and through the upper and, via the voids in the expansion card, through the lower exhaust ports in the rear face of the chassis.
Preferably, at least one of the voids comprises a notch that is routed or otherwise formed in the perimeter of the expansion board. In this embodiment, the interior surface of the chassis together with the notched void cooperatively define a passage for facilitating air flow at the edge of the expansion board. In the preferred embodiment, the computer system further includes a plurality of expansion or I/O cards that are received by the expansion board via the connectors. The system may further include a sheet metal piece vertically displaced below and substantially parallel to the expansion board. In one such embodiment, the expansion board is connected to the sheet metal piece via spacer structures. The sheet metal piece may, in one embodiment, be vertically displaced below the lower exhaust port of the rear face of the chassis. In another embodiment, the sheet metal piece is displaced above the lower exhaust port. In this embodiment, the sheet metal piece preferably includes one or more vents corresponding to the voids in the expansion board. The sheet metal vents may simply comprise voids in the sheet metal or, in an embodiment suitable for maximizing the EMF shielding provided by the sheet metal piece, the vents may comprise a perforated section or screen. Ideally, the sheet metal vents and the expansion board voids are aligned when the expansion board is received within the chassis. The sheet metal piece may reside between the expansion board and a power supply of the computer system thereby shielding the expansion board and I/O cards above the sheet metal and electronics below the sheet metal from one another.
The present invention still further contemplates a circuit board suitable for being received within a substantially rectangular chassis of a computer system. The circuit board includes at least one void suitable for facilitating air flow when the circuit board is received within the chassis. In one embodiment in which the circuit board comprises an expansion board, the board includes a plurality of connectors suitable for receiving a plurality of I/O cards. In one embodiment, the circuit board connectors are compliant with the PCI or other industry standard local bus specification. In the preferred embodiment, at least one of the voids is a notch formed at the perimeter of the circuit board, wherein, together with an interior surface of the chassis, the notched void defines an air passage at the edge of the circuit board when the board is received within the chassis. In this embodiment, the notched void is preferably defined by a pair of substantially parallel notch sidewalls that extend perpendicularly from the interior surface of the chassis to a baseline of the notch, where the baseline extends substantially parallel to the interior surface of the chassis when the circuit board is received within chassis. In one embodiment, at least one of the notched voids is formed into two or more of the four sides of the circuit board. In another embodiment, the notched voids are included in only the side of the board that abuts the interior surface of the rear face of the chassis when the circuit board

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