Title: Mounting and grounding assembly for circuit board mounted parallel to chassis bottom
Abstract: A computer chassis having tabs extending from the inside of its side panels and springs extending from the bottom panel, for spring-mounting a circuit board, such as a motherboard or other circuit board oriented parallel to the bottom surface of the chassis. The tabs and springs may also be used to ground the circuit board.
Patent Number: 6,937,475 Issued on 08/30/2005 to Rigimbal, et al.
| Inventors:
|
Rigimbal; Laurent A. (Round Rock, TX);
Holderness; Christopher L. (Pflugerville, TX)
|
| Assignee:
|
Dell Products L.P. (Round Rock, TX)
|
| Appl. No.:
|
654736 |
| Filed:
|
September 4, 2003 |
| Current U.S. Class: |
361/752; 361/753; 361/799; 361/809; 361/796; 361/807; 174/52.1 |
| Intern'l Class: |
H05K 005/02; H05K 007/12; H05K 007/14 |
| Field of Search: |
361/742,758,770,802,807-810,804,752,753,796-799
174/50,521,138.G
211/411.7
312/223.2,223.3
|
References Cited [Referenced By]
U.S. Patent Documents
| 5647748 | Jul., 1997 | Mills et al.
| |
| 5691504 | Nov., 1997 | Sands et al.
| |
| 5730515 | Mar., 1998 | Ho.
| |
| 5801928 | Sep., 1998 | Burstedt et al.
| |
| 5999416 | Dec., 1999 | McAnally et al.
| |
| 6075694 | Jun., 2000 | Mills et al.
| |
| 6191953 | Feb., 2001 | Aggus et al.
| |
| 6215667 | Apr., 2001 | Ady et al.
| |
| 6238026 | May., 2001 | Adams et al.
| |
| 6347044 | Feb., 2002 | Won et al.
| |
| 6404646 | Jun., 2002 | Tsai et al.
| |
| 6424537 | Jul., 2002 | Paquin et al.
| |
| 6424538 | Jul., 2002 | Paquin.
| |
| 6525266 | Feb., 2003 | Ferland et al.
| |
| 6537084 | Mar., 2003 | Casey et al.
| |
| 6544047 | Apr., 2003 | Moore.
| |
| 6751102 | Jun., 2004 | Chen.
| |
| 2002/0129954 | Sep., 2002 | Griffis.
| |
| 2002/0181212 | Dec., 2002 | Paquin et al.
| |
| 2002/0181219 | Dec., 2002 | Paquin et al.
| |
Primary Examiner: Vu; Phuong T.
Assistant Examiner: Levi; Dameon E.
Attorney, Agent or Firm: Baker Botts L.L.P.
Claims
1. A chassis for containing a computer, and for mounting a circuit board oriented
parallel to the bottom surface of the chassis and having notches cut from its perimeter, comprising:
two parallel side panels on opposing sides of the chassis, each side panel having
at least one tab protruding from its inner surface, each tab being slightly and
laterally offset from a location on the side panel opposing one of the notches
in the circuit board when the circuit board is mounted within the chassis; and
a planar bottom panel, having springs extending from its inner surface;
wherein the distance between the side panels is only slightly greater than the
width of the circuit board, such that the notches of the circuit board may be placed
over the tabs, and the circuit board lowered under the tabs and laterally shifted
such that the springs are compressed and hold the circuit board against the tabs.
2. The chassis of claim 1, wherein the side panels, bottom panels, tabs, and
springs are made from an electrically conductive material.
3. The chassis of claim 1, wherein the chassis is rectangular.
4. The chassis of claim 1, wherein the tabs are formed by stamping a form feature
in the sides of the chassis.
5. The chassis of claim 1, wherein the springs are formed by stamping a form
feature in the sides of the chassis.
6. The chassis of claim 1, wherein the side panels and the tab are made from
electrically conductive material, and wherein the circuit board has at least one
upper grounding pad and at least one tab is located such that it contacts the upper
grounding pad when the circuit board is mounted in the chassis.
7. The chassis of claim 1, wherein the side panels and the springs are made from
electrically conductive material, and wherein the circuit board has at least one
lower grounding pad and at least one spring is located such that it contacts the
lower grounding pad when the circuit board is mounted in the chassis.
8. The chassis of claim 1, wherein the springs are located near the sides of
the chassis.
9. The chassis of claim 1, wherein the springs are located proximate the tabs.
10. The chassis of claim 1, further comprising one or more standoffs on the bottom
panel of the chassis.
11. The chassis of claim 1, wherein each of the springs is made from a strip
of metal extending diagonally upward from the bottom panel.
12. The chassis of claim 1, wherein the tabs are triangular strips, stamped inward
from the side panels.
13. The chassis of claim 1, wherein the springs are metal strips, stamped inward
from the bottom panel.
14. A method of mounting a circuit board oriented parallel to the bottom surface
of a chassis, within a chassis having at least two opposing parallel sides, comprising
the steps of:
cutting notches in the perimeter of the circuit board;
providing tabs in the opposing parallel sides of the chassis, the tabs protruding
from the inner surface of the sides to a distance that permits them to pass through
the notches when the circuit board is positioned above the tabs and lowered;
providing springs on the bottom of the chassis, such that if the circuit board
is positioned above the tabs, lowered, and laterally shifted, the springs push
the board against the tabs;
positioning the circuit board directly above the tabs;
lowering the circuit board below the tabs; and
shifting the circuit board laterally such that the tabs are no longer directly
above the notches.
15. The method of claim 14, wherein the chassis is at least partly made from
an electrically conductive material, and further comprising the step of providing
at least one upper grounding pad on the circuit board that contacts at least one tab.
16. The method of claim 14, wherein the chassis is at least partly made from
an electrically conductive material, and further comprising the step of providing
at least one lower grounding pad on the circuit board that contacts at least one spring.
17. A circuit board suitable for mounting within a computer chassis parallel
to the bottom surface of the chassis, the chassis having a plurality of tabs protruding
from opposing side panels and a plurality of springs protruding from its bottom panel;
a circuit board base having a plurality of notches in its perimeter and having
a width slightly less than the distance between the side panels;
at least one upper grounding pad located on the top surface of the base, near
the perimeter of the base, such that the upper grounding pad contacts a tab when
the circuit board is mounted in the chassis; and
at least one lower grounding pad located on the bottom surface of the base, such
that the lower grounding pad contacts a spring when the circuit board is mounted
in the chassis.
18. The circuit board of claim 17, wherein the notches are entirely located in
a "keep out" area of the base.
Description
TECHNICAL FIELD
This invention is related to computer systems, and more particularly to a chassis
for a computer.
BACKGROUND
A computer chassis houses the main electronic components of the computer, including
the motherboard, power supply, cooling system, and optional adapters, such as adapters
that provide audio or video or networking capabilities. Typically, room is also
provided for data storage, such as a hard disk or CD-ROM drive.
The chassis fulfills several functions. In addition to simply housing and protecting
the electrical and mechanical components, it provides a mounting structure to which
the components are secured in accordance with a design that efficiently interconnects
them. It also provides a barrier for electromagnetic interference (EMI) caused
by electromagnetic fields generated inside or outside the chassis.
Computer chassis designs often incorporate hooks, tabs, channels, screws,
or the like for mounting circuit boards inside the chassis. These mounting methods
often result in a reduction of useful surface area of the circuit board.
SUMMARY
One aspect of the invention is a chassis for containing a computer and for mounting
a horizontally oriented circuit board. The chassis is designed for a circuit board
having small notches cut from its perimeter. The chassis may be various shapes,
but in general, has a flat bottom and opposing parallel side panels. The distance
between these side panels is only slightly greater than the width of the circuit
board. Each side panel has at least one tab protruding from its inner surface.
Each tab is slightly and laterally offset from a location on the side panel opposing
one of the notches in the circuit board when the circuit board is mounted within
the chassis. The bottom panel of the chassis has springs extending from its inner surface.
For installing the circuit board, the notches of the circuit board are placed
directly over the tabs. The circuit board is then lowered past the tabs and laterally
shifted such that the springs are compressed and hold the circuit board against
the tabs.
The chassis, including the tabs and springs, is electrically conductive. The
tabs and springs contact grounding pads on the upper and lower surfaces of the
circuit board, respectively, to provide grounding for the circuit board.
An advantage of the invention is that it provides good mounting and grounding
while reducing the useful board surface area as little as possible. It provides
an EMI ground path on both the top and the bottom of the circuit board, while at
the same time, providing maximum surface area for mounting components on the circuit
board. No holes are required to be drilled through the circuit board. Instead,
small notches are placed in the perimeter of the board, in a location that is typically
a "keep out" (non-populated) portion of the board.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the present embodiments and advantages thereof
may be acquired by referring to the following description taken in conjunction
with the accompanying drawings, in which like reference numbers indicate like features,
and wherein:
FIG. 1 illustrates a computer chassis having four circuit board mounting assemblies
in accordance with the invention.
FIG. 2 illustrates the computer chassis having a circuit board mounted inside,
using the assemblies of FIG. 1.
FIG. 3 is a side cut-away view of the computer chassis with one side removed
and with the circuit board mounted in place.
FIG. 4 is a top plan view of a tab positioned directly over a notch during the
installation of a circuit board.
FIG. 5 is a top plan view of the tab positioned over the grounding pad, after
the circuit board is lowered and laterally shifted from the position of FIG. 4.
DETAILED DESCRIPTION
FIG. 1 illustrates a computer chassis
10 having four circuit board mounting
assemblies
100 in accordance with the invention. As explained below, assemblies
100 receive a motherboard (not shown in FIG. 1) or any other circuit board
that is oriented parallel to the bottom surface of the chassis.
Chassis
10 is essentially a rectangular box, made from a rigid material,
such as sheet metal. It has six planer surfaces, namely, a bottom, top, two side
panels, a front panel, and a back panel. In FIG. 1, the front panel is removed,
in preparation for installation of circuit boards and other internal components.
The invention is also applicable for installation of these components with the
top panel removed.
The chassis material is conductive, and provides a grounding sink for the internal
components. In other embodiments, rather than being box-shaped, chassis
10
could have some other closed shape, regular or irregular, but will have a flat
bottom and two parallel sides. Various equivalent chassis shapes can be envisioned
having opposing sides that are at least partly parallel, with the circuit board
to be mounted in that portion of the chassis.
In the example of FIG. 1, chassis
10 has four circuit board mounting assemblies
100, one near each inner corner of chassis
10. Each assembly
100
has a tab
101 on the inside surface of a side wall of chassis
10,
and a proximately located grounding spring
102 on the inside bottom surface
of chassis. As explained below, a circuit board may be mounted between tabs
101
and springs
102 of the assemblies
100.
The number of assemblies
20 illustrated in FIG. 1 is convenient for mounting
a board that fits inside chassis
10 over the entire bottom of chassis
10.
However, this number of assemblies
100 is for purposes of illustration only.
More or fewer assemblies could be used, and not all need be used for mounting a
particular circuit board. Their location could be anywhere along two opposing and
parallel sides of chassis
10.
In the example of this description, tabs
101 are formed by stamping the
sheet metal that comprises the side of chassis
10. Such features are often
referred to as "form features". In the example of FIG. 1, the stamping process
for each tab
101 creates a metal strip stamped inward from the side panels,
and resulting in the triangular shaped tab
101 and leaving a corresponding
opening in the side of chassis
10.
In other embodiments, tabs
101 could be fabricated as a separate piece
and attached to the inner surface of chassis
10. In general, tabs
101
may be any shape, with a common feature being that they protrude from the inner
surface of the side of chassis
10 and are operable to hold down a board
that is oriented parallel to the bottom surface of the chassis
10 when installed,
as further explained below. For example, tabs
101 could be flat and/or rectangular.
Tabs
101 may be quite small. For example, tabs
101 having dimensions
of 0.140 inch by 0.200 inch would be suitable for a chassis
10 whose motherboard
is approximately 16×18 inches.
Board standoffs
103 are punched from, or attached to the bottom surface
of chassis
10. Their purpose is to prevent the installed circuit board (shown
in FIG. 2) from being pushed too far down toward the bottom of chassis
10.
Instead, as explained below, the board is suspended by springs
102. To this
end, the height of the top of springs
102 is higher than the height of standoffs
103. With a sufficiently stiff spring constant of springs
101, however,
standoffs
103 may not be required.
FIG. 2 illustrates chassis
10 having a circuit board
20 mounted
inside, using assemblies
100 in accordance with the invention. Circuit board
20 has a notch
23 corresponding to each tab
101. Notches
23
are slightly offset from tabs
101, when board
20 is installed. Various
representative components typically mounted on circuit board
20 are also
shown, such as integrated circuit chips
22 and heat sinks
23.
As may be easily understood by reference to FIG. 2, the inner width (w) between
the sides of the chassis
10 is only slightly larger than the width (w′)
of the circuit board
20. Circuit board
20 is mounted by placing it
inside chassis
10 with each notch
21 directly positioned above a
corresponding tab
101. The board
20 may then be lowered so that the
notches
21 are below the tabs
101. Next, board
20 is shifted
relative to chassis
10, so that each tab
101 is slightly to the side
of each notch
21. In the example of FIG. 2, board
20 has been lowered
so that tabs
101 fit through notches
21, and then board
20
has been shifted in the direction of the arrow to its proper location in chassis
10.
Notches
21 are placed along the edges of board
20, and need
not be large in size. As stated above, tabs
101 are small, and notches need
only be slightly larger. The small size of notches
21 results in their being
all, or substantially all, in an area of circuit board
20 that is not typically
populated with components.
A grounding pad
25 is adjacent each notch
21, along the edge of
board
20. Grounding pads
25 are positioned such that when circuit board
20 is shifted into place as described herein, tab
101 will be directly
above grounding pad
25. A metal-to-metal contact between tab
101
and grounding pad
25 provides grounding for circuit board
20. Grounding
pad
25 need not be large-in the example of this description, its length
and width are substantially the same as the length and width of tab
101.
In the example of FIG. 2, board
20 has dimensions (length and width) that
substantially conform to the bottom surface area of chassis
10. However,
smaller boards could be mounted in the same manner. A typical arrangement of mounting
assemblies
100 would be one at each corner of board
10, but as stated
above, more or fewer could be used.
In the example of this description, circuit board
20 is a "motherboard",
that is, a board populated with a processor, RAM, and perhaps other chips for implementing
the primary processing functions. However, circuit board
20 need not be
a "motherboard"-it may be any circuit board mounted parallel to the bottom surface
of chassis
10, slightly above the bottom surface of chassis
10.
FIG. 3 is a side cut-away view of a portion of chassis
10 with one side
removed and with circuit board
20 mounted in place. Only the bottom panel
of chassis
10 is shown. Because the side of chassis
10 is removed,
tab
101 is not shown in FIG.
3. Upper ground pad
25 is visible
on the top surface of board
20, as well as notch
21.
Referring to both FIGS. 1 and 3, a grounding spring
102 has a fixed
end on the bottom surface of chassis
10 and a free end extending upwardly
from the bottom surface, and is generally cantilevered in shape. The free end of
spring
102 is not attached to board
20, but rather the bottom of
board
20 rests on the top of spring
20. The contacting (top) portion
of spring
201 may be extended or broadened to provide as much contact area
as is desired.
Spring
102 is constructed from a conductive material, such as a metal,
having properties that permit the free end of spring
102 to move in an upward
or downward direction in a spring-like manner. A possible design for spring
102
is as a form feature, stamped into the sheet metal that forms the bottom of chassis
10. Alternatively, spring
102 could be a separate piece, attached
to the bottom surface of chassis
10.
In FIG. 3, board
20 is in place, having been lowered so that tab
101
passes through notch
21 and then shifted so that tab
101 is over
upper ground pad
25. When board
20 has been installed in this manner,
spring
102 is compressed. The distance, x, between the fixed end of spring
102 and the free end is smaller than it would be if board were not installed.
The pressure of spring
202 against the bottom of board
20 results
in upper grounding pad
25 being pushed upwardly against the bottom of tab
201. This provides grounding for the top of board
20.
Lower ground pads
31 are located on the bottom surface of board
20.
They may be any convenient size, but are located such that they contact the top
of springs
202 when board
20 is installed. In this example, lower
ground pads
31 are substantially the same rectangular shape and size as
upper ground pads
31. By contacting ground pads
31, springs
102
provide a conductive connection from circuit board
20 to the bottom of chassis
10.
Like upper ground pads
25, lower ground pads
31 are conductive.
Pads
25 and
31 may be easily fabricated on board
20 during
the metallization phase of fabrication, in a manner similar to the fabrication
of solder pads.
In the example of this description, each tab
101 is located close to a
spring
102 within chassis
10. Likewise, each upper ground pad
25
is located close to a lower ground pad
31 on opposing sides of board
20.
However, this is not necessary, so long as tabs
101 are located such that
they will contact upper ground pads
25 and springs
102 are located
such that they will contact lower ground pads
31 when circuit board
20
is installed. In other words, the contacting tab
101 and upper ground pad
25 may be displaced from the contacting spring
102 and lower ground
pad
31.
FIGS. 4 and 5 are top plan views of a tab
101 extending from the side
of chassis
10, and further illustrate the process of installing a circuit
board
20 within chassis
10. Only the portion of circuit board
20
in the area of tab
101 is shown. In FIG. 4, the circuit board
20
has been lowered down into chassis
10, with tab
101 passing through
notch
21. The board
20 was initially placed so that notch
21
was directly above tab
101, then lowered so that tab
101 passed through
notch
21. In FIG. 5, the board
20 has been shifted laterally in the
direction of the arrow, so that tab
101 is over grounding pad
25.
As explained above, as a result of the upward pushing action of the underlying
spring
101, the contact between tab
101 and grounding pad
25
is snug. If desired, the top surface of spring
102 may have raised bumps
or other patterning to ensure a multi-point contact, or to otherwise facilitate
good grounding.
Referring again to FIG. 1, a lock spring
13 is attached to the front
edge of chassis
10. In other embodiments, the lock spring may be attached
to the back edge, or to both the front and back edges. During installation of board
20, spring
13 is depressed so as to permit board
20 to be
lowered and shifted into place as described above. Once board
20 is properly
situated, spring
13 is released and is operable to hold board
20
in place, with each tab
101 contacting its associated upper grounding pad
25 and with each spring
102 contacting its associated lower grounding
pad
31.
Although the disclosed embodiments have been described in detail, it should
be understood that various changes, substitutions and alterations can be made to
the embodiments without departing from their spirit and scope.
*
