Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2001-05-15
2004-08-17
Datskovsky, Michael (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S689000, C361S692000, C361S689000, C165S121000, C257S717000
Reexamination Certificate
active
06778390
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to the field of cooling components on a printed circuit board. More specifically, the present invention is directed to an apparatus and method for providing improved heat transfer to a plurality of chips on a printed circuit board.
BACKGROUND OF THE INVENTION
The ability to arrange electronic components on printed circuit boards having standard sizes allows for the easy configuration, assembly, repair and upgrading of electronic devices. Personal computers, for example, typically include a motherboard having multiple standardized ports or buses which include slots or connectors for attaching boards or cards. As a testament to the flexibility of this approach, connectors are included in nearly every personal computer, allowing for the addition of computer memory, connections to input/output (I/O) devices, and additional computing power.
Bus standards include, but are not limited, the Peripheral Component Interconnect (PCI) and the Industry Standard Architecture (ISA) standards, both of which have general utility, and the Accelerated Graphics Port (AGP) standard, which is designed for improving the graphics capabilities of computers. Each of these standards includes electrical and electronic standards for providing computational functions and mechanical standards to assure that the connectors and cards mate to provide the required electrical connections and physical stability. Of particular interest here are the mechanical standards, which include but are not limited to details of the geometrical configuration of the card edge that mates with the connector, the width, length and height of the assembled board, and the electrical specifications and power use of the card.
In addition to meeting the bus standards, it is important that card components including, but not limited to processors, memory chips, power supplies, and other electronic components, are operated within prescribed temperature limits. For high-power dissipating devices such as power supplies and processors, it is generally required that the operating temperature be kept below a maximum operating temperature. For boards having a plurality of temperature-sensitive components within the same circuit, maintaining individual chip temperatures within a range that allows all chips to operate the same. Thus, for example, memory chips often have temperature-dependent clock speeds. Circuits that have memory chips in parallel operate best if all the chips are within some temperature range, and thus have the same approximate clock speed.
Techniques for removing heat from electronic components has evolved with cooling demands. Fans of various types are used to force air out of the back of the enclosure or to force fresh air into the enclosure. In either case, such fans induce internal circulation and promote convective heat transfer from heat generating components. Other techniques include using more than one fan or ducting the flow within the enclosure to improve heat removal. On the component level, the use of passive heat sinks for heat removal from individual components is well known in the art. Axial fans or blowers are often added to high heat generating and temperature sensitive components, such as processors. These air moving devices increase the local heat transfer, moving thermal energy from one or several components into the enclosure. Techniques for improving heat sink contact with components have also been developed, as have active heat removal systems, such as heat pipes and Peltier devices.
The trend in recent years has been towards placing faster, more powerful computer chips having increased dissipation on each printed circuit board. These boards are normally stacked close to achieve a compact overall design. Stacking the boards may hinder the ability of the air to circulate near hot components, and may also reduce the effectiveness of chip or heat sink mounted fans or blowers. In addition, many high-end cards, such as GPUs, include a processor having a dedicated fan and other computer chips that should be operated at or near the same temperature. For example boards conforming to the AGP standard usually include a high power dissipating GPU and banks of clock-speed temperature-dependent memory chips, sometime laid out along two perpendicular lines about the GPU. Cooling systems thus need to cool the GPU to keep it from overheating and maintain a plurality of memory chips at or near the same temperature. The prior art methods are not sufficient to maintain several components, chips or sets of chips on one printed circuit board at or near a specified temperature. In addition, board standards require keeping all components within a specified height of the board so that adjacent slots can be used for other boards.
An example of a prior art problem and solution to a beat removal problem, as encountered in the design of an AGP board, is shown with reference to prior art
FIGS. 1 and 2
, which show the design specifications and component layout for an AGP card capable of consuming 50 Watts of power (a “AGP Pro
50
” card). The AGP Pro specification is being adopted to accommodate AGP-like cards that have greater power consumption and may require more space on the motherboard than does an AGP standard board.
FIG. 1
shows an edge view of a motherboard
107
having an AGP Pro connector
109
, a PCI card
110
, and adjacent PCI connectors
111
and
113
. AGP Pro connector
109
and PCI connectors
111
and
113
are parallel, are aligned with the length L of card
101
, and are separated by a distance S. An AGP Pro compatible device
100
having a card
101
with a component side
115
and solder side
117
has a protruding portion
125
for electrically mating with connector
109
, and a bracket
137
for fixing the AGP Pro compatible device to the computer frame (not shown). Bracket
137
is usually located near a wall of the computer enclosure and has an I/O connector mounted thereon (not shown) for making connections outside of the computer. An outline
103
specifies the maximum width W and height H of objects associated with component side
115
, and an outline
105
specifies the maximum width W arid height B of objects associated with solder side
117
. Of particular interest is outline
103
. The original specifications for an AGP card call for an AGP compliant card to take up only the space between the AGP board and the next closest board (a height H less than S-B). Principally because of the increased power consumption, the original AGP standard was modified into an AGP Pro
50
standard, which allows a card occupy a height H which overlaps the space of the adjoining PCI slots
111
. The next closest position for inserting PCI card
110
is PCI connector
113
, PCI cards that might have occupied PCI connector
111
are not available for use when AGP card
100
is in connector
109
.
FIG. 2A
shows a top view
2
A—
2
A of AGP card
100
from
FIG. 1
showing various components to be cooled and a prior art method of cooling, and
FIG. 2B
shows a cross-sectional view of memory chips
121
and heat sink
131
. Mounted on card
101
are a GPU
119
and a plurality of memory chips
121
arranged along two rows
129
and
131
. Mounted on GPU
119
is a fan
135
for cooling the various components. Fan
135
is typically a vertical fan that draws air above card
100
as shown in FIG.
1
and towards GPU
100
to produce a vertical convective flow that subsequently flows over card
100
as shown by the arrows emanating from fan
135
. Each of the rows
129
and
131
of memory chips
121
has a heat sink
123
placed on top of the memory chips and having fins that protrude away from card
100
. As shown on
FIG. 2B
, heat sink
123
has a substantially flat bottom
126
that is in thermal contact with memory chips
121
, and fins
124
that protrude away from the bottom. Heat sink
123
is of a material having a high thermal conductivity, usually a metal such as aluminum or copper. Fins
124
provide increased surface area for heat transfer, either through nat
Cooley & Godward LLP
Datskovsky Michael
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