U.S. patent application number 13/553414 was filed with the patent office on 2013-05-09 for midplane especially applicable to an orthogonal architecture electronic system.
The applicant listed for this patent is Marc B. Cartier, JR., Thomas S. COHEN, Mark W. Gailus. Invention is credited to Marc B. Cartier, JR., Thomas S. COHEN, Mark W. Gailus.
Application Number | 20130112468 13/553414 |
Document ID | / |
Family ID | 48222944 |
Filed Date | 2013-05-09 |
United States Patent
Application |
20130112468 |
Kind Code |
A1 |
COHEN; Thomas S. ; et
al. |
May 9, 2013 |
MIDPLANE ESPECIALLY APPLICABLE TO AN ORTHOGONAL ARCHITECTURE
ELECTRONIC SYSTEM
Abstract
A midplane has a first side to which contact ends of a first
differential connector are connected and a second side opposite the
first side to which contact ends of a second differential connector
are connected. The midplane includes a plurality of vias extending
from the first side to the second side, with the vias providing
first signal launches on the first side and second signal launches
on the second side. The first signal launches are provided in a
plurality of rows, with each row having first signal launches along
a first line and first signal launches along a second line
substantially parallel to the first line. The second signal
launches are provided in a plurality of columns, with each column
having second signal launches along a third line and second signal
launches along a fourth line substantially parallel to the third
line.
Inventors: |
COHEN; Thomas S.; (New
Boston, NH) ; Cartier, JR.; Marc B.; (Dover, NH)
; Gailus; Mark W.; (Concord, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
COHEN; Thomas S.
Cartier, JR.; Marc B.
Gailus; Mark W. |
New Boston
Dover
Concord |
NH
NH
MA |
US
US
US |
|
|
Family ID: |
48222944 |
Appl. No.: |
13/553414 |
Filed: |
July 19, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12789621 |
May 28, 2010 |
8226438 |
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13553414 |
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12203270 |
Sep 3, 2008 |
7744415 |
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12789621 |
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11522530 |
Sep 18, 2006 |
7422484 |
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12203270 |
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11173927 |
Jul 1, 2005 |
7108556 |
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11522530 |
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60584928 |
Jul 1, 2004 |
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60638973 |
Dec 24, 2004 |
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Current U.S.
Class: |
174/262 |
Current CPC
Class: |
H01R 12/00 20130101;
H01R 13/646 20130101; H05K 2201/044 20130101; H05K 1/116 20130101;
H05K 1/14 20130101; H05K 1/0231 20130101; H05K 2201/09718 20130101;
H01R 13/6587 20130101; H01R 13/514 20130101; H01R 13/6471 20130101;
H05K 1/0237 20130101; H05K 1/115 20130101; H05K 2203/1572 20130101;
H05K 2201/09236 20130101; H05K 2201/10189 20130101; H05K 7/1445
20130101; H05K 3/429 20130101 |
Class at
Publication: |
174/262 |
International
Class: |
H05K 1/11 20060101
H05K001/11 |
Claims
1-36. (canceled)
37. A printed circuit board having a first side for coupling with a
first connector and a second side, opposite the first side, for
coupling with a second connector, the printed circuit board
comprising: a first plurality of vias extending from the first side
to the second side with the vias providing first signal launches on
the first side and second signal launches on the second side, the
first signal launches arranged in pairs and provided in a plurality
of rows for electrically connecting to signal couplings of the
first connector, and the second signal launches arranged in pairs
and provided in a plurality of columns for electrically connecting
to signal couplings of the second connector; and a second plurality
of vias extending from the first side to the second side with the
second plurality of vias providing first ground launches on the
first side and second ground launches on the second side, wherein,
for each pair of first signal launches in each row, one first
signal launch is disposed along a first line, and the other first
signal launch is disposed along a second line substantially
parallel to the first line, wherein, for each pair of second signal
launches in each column, one second signal launch is disposed along
a third line, and the other second signal launch is disposed along
a fourth line substantially parallel to the third line, wherein,
for each pair of first signal launches in each row, there is a
first ground launch disposed therebetween, and wherein, for each
pair of second signal launches in each column, there is a second
ground launch disposed therebetween.
38. The printed circuit board according to claim 37, wherein the
first and second lines are orthogonal to the third and fourth
lines.
39. The printed circuit board according to claim 38, wherein for
each row of first signal launches, the first ground launches are
provided along a fifth line adjacent to and substantially parallel
to the first line and the second lines, and for each column of
second signal launches, the second ground launches are provided
along a sixth line adjacent to and substantially parallel to the
third line and the fourth line.
40. The printed circuit board according to claim 39, wherein there
is exactly one first ground launch disposed between each pair of
first signal launches and an adjacent pair of first signal
launches, and wherein there is exactly one second ground launch
disposed between each pair of second signal launches and an
adjacent pair of second signal launches.
41. The printed circuit board according to claim 37, wherein for a
surface area on the first side and the same surface area on the
second side, the number of first signal launches equals the number
of second signal launches.
42. The printed circuit board according to claim 37, further
comprising at least one ground plane layer with the plurality of
vias extending therethrough, and wherein for each pair of vias
corresponding to a signal coupling pair of the first connector and
the second connector, an area surrounding the pair of vias is free
of the ground plane layer and each via of the pair is electrically
isolated from the other.
43. The printed circuit board according to claim 42, wherein the
area surrounding the pair of vias free of the ground plane layer is
substantially oval in shape.
44. The printed circuit board according to claim 42, wherein the
area surrounding the pair of vias free of the ground plane layer is
substantially rectangular in shape.
45. The printed circuit board according to claim 42, wherein the
area surrounding the pair of vias free of the ground plane layer is
oriented substantially at a 45 degree angle relative to the rows of
the first signal launches.
46. The printed circuit board according to claim 42, wherein the
area surrounding the pair of vias free of the ground plane layer is
oriented substantially at a 45 degree angle relative to the columns
of the second signal launches.
47. The printed circuit board according to claim 46, wherein for
the pairs of vias corresponding to the signal couplings of the
first connector and the second connector, a region between adjacent
pairs of vias includes the ground plane layer.
48. An electrical interconnect assembly comprising: a printed
circuit board according to claim 37; a first electrical connector
having a plurality of first signal couplings arranged in pairs, and
a plurality of first ground couplings; and a second electrical
connector having a plurality of second signal couplings arranged in
pairs, and a plurality of second ground couplings, wherein each of
the first signal couplings corresponds to one of the second signal
couplings, wherein each of the first ground couplings corresponds
to one of the second ground couplings, wherein each first signal
coupling and the corresponding second signal coupling are
electrically connected to a same one of the plurality of first
vias, and wherein each first ground coupling and the corresponding
second ground coupling are physically connected to different ones
of the plurality of second vias.
49. An electrical interconnect assembly comprising: a printed
circuit board according to claim 40; and a first electrical
connector having a plurality of first signal couplings arranged in
pairs and provided in rows, and a plurality of first ground
couplings, wherein each first ground coupling corresponds to a pair
of first signal couplings, wherein each first signal coupling is
electrically connected to a first signal launch, wherein, for each
pair of first signal couplings, a corresponding first ground
coupling and a first ground coupling corresponding to an adjacent
pair of first signal couplings are physically connected to the
exactly one ground launch disposed between the adjacent pairs of
first signal couplings.
50. The electrical interconnect assembly according to claim 49
further comprising: a second electrical connector having a
plurality of second signal couplings arranged in pairs and provided
in columns, and a plurality of second ground couplings, wherein
each second ground coupling corresponds to a pair of second signal
couplings, wherein each second signal coupling is electrically
connected to a second signal launch, wherein, for each pair of
second signal couplings, a corresponding second ground coupling and
a second ground coupling corresponding to an adjacent pair of
second signal couplings are physically connected to the exactly one
ground launch disposed between the adjacent pairs of second signal
couplings.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application claims priority to U.S. Provisional
Patent Application No. 60/584,928, filed Jul. 1, 2004, and U.S.
Provisional Patent Application No. 60/638,973, filed Dec. 24, 2004,
the disclosures of which are incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] Modern electronic systems are typically assembled from
multiple printed circuit boards. Such printed circuit boards, which
are commonly referred to as "daughter cards", contain components
thereon, such as integrated circuits. Each daughter card also
typically includes one or more connectors that allow the components
on the daughter card to communicate with components on the other
daughter cards in the system.
[0003] One way to interconnect the daughter cards in an electronic'
system is to utilize a midplane. A midplane is a printed circuit
board, typically larger than the daughter cards, to which the
daughter cards are connected--by way of connectors on both the
daughter cards and the midplane--and that provides conductive paths
therein. The conductive paths, which are also referred to as
"signal traces", interconnect and provide communication between the
daughter cards in the system. A midplane, as the name implies,
provides connectors on both sides, allowing daughter cards to be
connected on both sides of the midplane. The midplane can route
signals between daughter cards connected on the same side of the
midplane or can cross-connect a daughter card on one side of the
midplane with a daughter card on the other side of the
midplane.
[0004] In order to connect a connector to the midplane, holes are
conventionally drilled through the midplane. The holes, which are
also referred to as "vias", electrically connect to signal traces
in the midplane. The inside walls of the vias are typically plated
with a conductive material, such as metal, to provide electrical
conductivity. The connector is provided with contact ends, such as
press-fit contact tails or SMT (surface mount technique) contact
tails, for connecting to the vias.
[0005] As electronic systems have become smaller, faster and more
complex, this has generally required that midplanes provide more
vias and signal traces without increasing in size, or in many
instances, while actually decreasing in size. This has introduced
significant difficulties in designing and fabricating midplanes, as
well as significant difficulties in dealing with electrical noise
and other electrical characteristics. Electrical noise is usually
considered any undesirable electrical energy in an electronic
system, including but not limited to, reflections, electromagnetic
interference, mode conversions and unwanted coupling, such as
cross-talk.
[0006] The trend for smaller, faster and more complex electronic
systems has also required connectors to carry more and faster data
signals in a smaller space without degrading the electrical
characteristics of the signal. Connectors can be made to carry more
signals in less space by placing signal conductors in a connector
closer together. A major difficulty with placing signal conductors
closer together is that electrical noise between the signal
conductors increases as the distance between signal conductors
decreases and as the speed of the signals increases. In addition,
as frequency content increases, there is a greater possibility of
energy loss. Energy loss may be attributed to impedance
discontinuities, mode conversion, leakage from imperfect shielding,
or undesired coupling to other conductors (crosstalk). Therefore,
connectors are designed to control the mechanisms that enable
energy loss. Conductors composing transmission paths are designed
to match system impedance, enforce a known propagating mode of
energy, minimize eddy currents, and isolate alternate transmission
paths from one another. One example of controlling energy loss is
the placement of a conductor connected to a ground placed adjacent
to a signal contact element to determine an impedance and minimize
energy loss in the form of radiation.
[0007] One way to control electrical noise in a connector is to
utilize differential signals. Differential signals are signals
represented by a pair of signal conductors, called a "differential
pair". The voltage difference between the pair of signal conductors
represents the signal. If electrical noise is electromagnetically
coupled to a differential pair, the effect on each signal conductor
of the pair should be similar. This renders a differential pair
less sensitive to electrical noise as compared with a single signal
conductor. However, use of a differential connector, especially in
a midplane system architecture, introduces further difficulties as
vias corresponding to the differential pair on either side of the
midplane must each be electrically connected in the midplane and
signal traces can only be routed between adjacent differential
pairs.
[0008] What is desired, therefore, is to provide a midplane and a
differential connector designed for such a midplane that addresses
the difficulties described above.
SUMMARY OF THE INVENTION
[0009] In one embodiment of a midplane in accordance with the
invention, the midplane has a first side to which contact ends of a
first differential connector are connected and a second side
opposite the first side to which contact ends of a second
differential connector are connected. The midplane includes a
plurality of vias extending from the first side to the second side,
with the vias providing first signal launches on the first side and
second signal launches on the second side. The first signal
launches are provided in a plurality of rows for electrically
connecting to the contact ends of the first differential connector,
with each row having first signal launches along a first line and
first signal launches along a second line substantially parallel to
the first line. The first signal launches along the first and
second lines are offset so that first signal launches along the
first line and adjacent first signal launches along the second line
correspond to differential pairs of the first differential
connector. The second signal launches are provided in a plurality
of columns for electrically, connecting to the contact ends of the
second differential connector, with each column having second
signal launches along a third line and second signal launches along
a fourth line substantially parallel to the third line. The second
signal launches along the third and fourth lines are offset so that
second signal launches along the third line and adjacent second
signal launches along the fourth line correspond to differential
pairs of the second differential connector.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The accompanying drawings are not intended to be drawn to
scale. In the drawings, each identical or nearly identical
component that is illustrated in various figures is represented by
a like numeral. For purposes of clarity, not every component may be
labeled in every drawing. In the drawings:
[0011] FIG. 1 is a perspective view of an electronic system
utilizing a midplane according to an embodiment of the present
invention;
[0012] FIG. 2 is a partially exploded view of a differential
electrical connector assembly according to an embodiment of the
present invention that may be used in the electronic system of FIG.
1;
[0013] FIG. 3 is a perspective view of a differential midplane
connector shown in FIG. 2;
[0014] FIG. 4 is a perspective view showing rows of differential
pair signal conductors and corresponding ground conductors of the
differential midplane connector shown in FIG. 3 according to an
embodiment of the present invention;
[0015] FIG. 4A is an alternative embodiment of FIG. 4, showing rows
of differential pair signal conductors and corresponding ground
conductors of the differential midplane connector shown in FIG.
3;
[0016] FIG. 5 is a bottom view showing first contact ends of the
differential pair signal conductors and corresponding ground
conductors of the differential midplane connector shown in FIG.
4;
[0017] FIG. 6 is a perspective view of a differential daughtercard
connector according to an embodiment of the present invention shown
in FIG. 2, with a wafer separated from the connector for
clarity;
[0018] FIG. 7 is an exploded view of the wafer of FIG. 6 showing
only the differential pair signal conductors and corresponding
ground conductor;
[0019] FIG. 8A is a schematic top view of a portion of one side of
the midplane of FIG. 1, with a part of the surface removed to show
a ground plane layer;
[0020] FIG. 8B is a schematic top view of a portion (the same
portion as FIG. 8A) of the other side of the midplane of FIG. 1,
with a part of the surface removed to show a ground plane
layer;
[0021] FIG. 9A is a schematic view of a cross-section through the
mating contact region of a traditional differential midplane
connector attached to one side of a midplane;
[0022] FIG. 9B is a schematic view of a cross-section through the
mating contact region of a traditional differential midplane
connector attached to the other side of a midplane as illustrated
in FIG. 9A;
[0023] FIGS. 9C and 9D are diagrams illustrating via hole patterns
for FIGS. 9A and 9B, respectively for traditional differential
midplane connectors;
[0024] FIG. 10A is a schematic view of a cross-section through the
mating contact region of a differential midplane connector attached
to one side of a midplane according to an embodiment of the present
invention;
[0025] FIG. 10B is a schematic view of a cross-section through the
mating contact region of a differential midplane connector attached
to the other side of a midplane according to an embodiment of the
present invention;
[0026] FIGS. 10C and 10D are diagrams illustrating via hole
patterns for FIGS. 10A and 10B, respectively for differential
midplane connectors according to an embodiment of the present
invention;
[0027] FIG. 11A is a perspective view of two differential
electrical connector assemblies attached to opposing sides of a
midplane according to an embodiment of the present invention;
and
[0028] FIG. 11B is a schematic side view of FIG. 11A, showing two
pairs of signal conductors each mounted on opposing sides of a
midplane and sharing common vias according to an embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0029] This invention is not limited in its application to the
details of construction and the arrangement of components set forth
in the following description or illustrated in the drawings. The
invention is capable of other embodiments and of being practiced or
of being carried out in various ways. Also, the phraseology and
terminology used herein is for the purpose of description and
should not be regarded as limiting. The use of "including,"
"comprising," "having," "containing," "involving," and variations
thereof herein, is meant to encompass the items listed thereafter
and equivalents thereof as well as additional items.
[0030] Referring to FIG. 1, there is shown a sketch of an
electronic system 100 which utilizes a midplane 110 in accordance
with the present invention. The midplane has a first side 112 and a
second side 114. Daughtercards 120A, 120B, 120C and 120D are
electrically connected to the midplane 110 on the second side 114.
Daughtercards 130A, 130B and 130C are electrically connected to the
midplane 110 on the first side 112. Note that the daughtercards
130A-130C on the first side 112 of the midplane 110 are orthogonal
in orientation to the daughtercards 120A-120D on the second side
114 of the midplane 110. The concepts embodied in the present
invention are especially applicable to such an orthogonal
architecture electronic system.
[0031] While not shown in the sketch of FIG. 1, daughtercards
120A-120D and 130A-130C are electrically connected to the midplane
110 by electrical connector assemblies. FIG. 2 shows a preferred
embodiment of such an electrical connector assembly 200 in
accordance with the present invention. Midplane 110 includes
multiple signal traces that route signals between daughtercards
120A-120D and 130A-130C of the electronic system 100. The midplane
110 is described in greater detail with respect to FIG. 7. It
should be noted that the number of daughtercards 130A-130C shown on
the first side 112 and the number of daughtercards 120A-120D shown
on the second side 114 are for illustrative purposes only, and the
actual number of daughtercards connected to the midplane 1.10 may
vary depending upon the electronic system.
[0032] FIG. 2 shows the electrical connector assembly 200 that may
be used to connect the daughtercards 120A-120D and 130A-130C to the
midplane 110 of FIG. 1. The electrical connector assembly 200 is
preferably a differential electrical connector assembly. The
electrical connector assembly 200 includes a first differential
electrical connector 300, which in the illustration connects to the
midplane 110, and a second differential electrical connector 400,
which connects to one of the daughtercards (daughtercard 120A is
referenced for illustration in FIG. 2). Typically, one or more
second connectors 400 would be connected to each daughtercard, with
the corresponding number of first connectors 300 connected to the
midplane 110.
[0033] FIG. 3 shows a differential midplane connector 300 having a
housing 302, which is preferably made of an insulative material.
The housing 302 has sidewalls 304, 305, end walls 307, 308 and a
base (not numbered). Disposed in the base of the housing 302 are a
plurality of signal conductors 310 provided as differential pairs
and a plurality of ground conductors 320, with each ground
conductor 320 corresponding to a differential pair of signal
conductors 310 and positioned adjacent thereto. As shown in greater
detail in FIGS. 4, 4A and 5, the signal conductors 310 and the
ground conductors 320 are provided in a plurality of rows. For
exemplary purposes only, six rows 330a-330f are shown in FIG. 4,
with each of the rows having six differential pairs of signal
conductors 310 and six corresponding ground conductors 320. Note
that the number of rows, the number of signal conductors 310 for
each row, and the number of ground conductors 320 for each row may
be any number as desired. However, as will become more apparent in
connection with the description of the midplane 110 in FIG. 8, it
is preferable to pre-select the number of rows, the number of
signal conductors 310 for each row, and the number of ground
conductors 320 for each row to ensure a substantially square
footprint for connecting to the midplane 110.
[0034] Each signal conductor 310 has a first contact end 312
connectable to the midplane 110, a second contact end 314, and an
intermediate portion 316 therebetween having a first width as
measured from first edge 317 to second edge 318 of the signal
conductor 310. Each ground conductor 320 has a first contact end
322 connectable to the midplane 110, a second contact end 324, and
an intermediate portion 326 therebetween having a second width as
measured from first edge 327 to second edge 328 of the ground
conductor 320. Preferably, the second width of the intermediate
portion 326 of the ground conductor 320 is at least twice the first
width of the intermediate portion 316 of the signal conductor 310.
This allows the ground conductor 320 to provide sufficient
shielding to the corresponding differential pair of signal
conductors 310 from the electromagnetic effects of signal
conductors in adjacent rows.
[0035] In the preferred embodiment, the first contact end 322 of
the ground conductor 320 includes a first contact arm 332 and a
second contact arm 333 spaced from the first contact arm 332. The
first and second contact arms 332, 333 extend in the direction of
the corresponding differential pair of signal conductors 310.
Preferably, the first and second contact arms 332, 333 extend
beyond the plane of the corresponding signal conductors 310. This
allows the contact arms 332, 333 to provide sufficient shielding to
the corresponding differential pair of signal conductors 310 from
the electromagnetic effects of adjacent signal conductors in the
row. Note that for each of the plurality of rows 330a-330f, the
first contact arm 332 of a ground conductor 320 is proximal and
substantially parallel to the second contact arm 333 of an adjacent
ground conductor 320, except at an end of a row.
[0036] The drawings show that the first contact end 312 of each
signal conductor 310 and the first contact end 322 of each ground
conductor 320 as press-fit contact tails. However, it should be
apparent to one of ordinary skill in the art that the first contact
ends 312, 322 may take any known form, e.g., pressure-mount
contacts, paste-in-hole solder attachment, contact tails adapted
for soldering, etc., for connecting to the midplane 110. In the
preferred embodiment, the press-fit contact tails of the signal
conductors 310 are oriented in a first direction and the press-fit
contact tails of the ground conductors 320 are oriented in a second
direction substantially perpendicular to the first direction.
[0037] Referring to FIGS. 4 and 5, each differential pair of signal
conductors 310 of a row, e.g., row 330a, has one first contact end
312(a) that lies along a first line 350 and is parallel to the
plurality of rows and an other first contact end 312(b) that lies
along a second line 352 and is parallel to and spaced from the
first line 350. The first contact end 322 of the corresponding
ground conductor 320 preferably lies along a third line 354 that is
parallel to and spaced from the first and second lines 350, 352. In
the preferred embodiment, the third line 354 is positioned between
the first and second lines 350, 352. This configuration, as
described in greater detail with respect to the description of the
midplane 110 in FIG. 8, provides a substantially square footprint
for connecting to the midplane 110.
[0038] For each differential pair of signal conductors 310 of a
row, the second contact ends 314 lie along a fourth line 356. The
fourth line 356 is preferably parallel to the plurality of rows.
The second contact ends 324 of the ground conductors 320 lie along
a fifth line 358 that is parallel to and spaced from the fourth
line 356.
[0039] Referring now to FIG. 4A, there is shown an alternative
embodiment of FIG. 4. In this embodiment, the signal conductors 310
are as shown in FIG. 4. However, instead of providing a ground
conductor 320 corresponding to each differential pair of signal
conductors 310 as illustrated in FIG. 4, there is provided a single
first ground conductor 370 for each row of signal conductors 310.
The first ground conductor 370 extends substantially the length of
the corresponding row, where the rows are referenced by 330a'-330f'
in FIG. 4A. Each first ground conductor 370 has a plurality of
mating contact ends 374 that are connectable to the corresponding
ground conductor of the second differential electrical connector
400. The number of mating contact ends 374 of each first ground
conductor 370 is preferably the same as the number of differential
pairs of signal conductors 310 of each corresponding row. In the
example illustrated in FIG. 4A, there are six mating contact ends
374 corresponding to the six differential pairs of signal
conductors 310.
[0040] A plurality of second ground conductors 380 are also
provided, with each second ground conductor 380 electrically
connected to each first ground conductor 370 and oriented
substantially perpendicular to the first ground conductors 370.
Each second ground conductor 380 extends substantially the length
of the plurality of rows 330a'-330f', and each second ground
conductor 380 is positioned between adjacent differential pairs of
signal conductors 310 of each row 330a'-330f'. The second ground
conductors 380 are each provided with a first contact end
connectable to the midplane 110. Preferably, the first contact end
of each second ground conductor 380 includes a plurality of contact
pins 382 that are oriented perpendicularly to the orientation of
the contact pins 312 of the signal conductors 310. Note that for
each row 330a'-330f', there is a contact pin 382 of a second ground
conductor 380 adjacent each differential pair of signal conductors
310. And for each row 330a'-330f', the contact pins 382 for the row
lie along a third line 354, as described with respect to FIG. 5.
Other suitable configurations of signal conductors 310 and ground
conductors 320 may also be used, as will be apparent to those of
ordinary skill in the art.
[0041] Referring now to FIGS. 6 and 7, there is shown the second
differential electrical connector 400 of the electrical connector
assembly 200 which mates to the first differential electrical
connector 300 on one side and electrically connects to one of the
daughtercards (e.g., daughtercard 130C) on another side. The second
differential electrical connector 400 includes a plurality of
wafers 401, where each of the plurality of wafers 401 corresponds
to one of the plurality of rows (e.g., 330a-330f of FIG. 4) of the
first differential electrical connector 300. Thus, the number of
wafers 401 of the second differential electrical connector 400 is
the same as the number of rows of the first differential electrical
connector 300. Each wafer 401 includes a housing 402, which is
preferably made of an insulative material. A plurality of signal
conductors 410 provided as differential pairs are held in the
housing 402 with a corresponding ground conductor 420 positioned
adjacent thereto. The signal conductors 410 and the corresponding
ground conductor 420 are shown in greater detail in FIG. 7. Note
that the number of differential pairs of signal conductors 310
provided in a row of the first differential electrical connector
300 is the same as the number of differential pairs of signal
conductors 410 provided in the corresponding wafer 401 of the
second differential electrical connector 400.
[0042] Each signal conductor 410 has a first contact end 412
connectable to one of the daughtercards (e.g., 120A-120D, 130A-130C
of FIG. 1), a second contact end 414 connectable to the second
contact end 314 of a corresponding signal conductor 310 of the
first differential electrical connector 300, and an intermediate
portion 416 therebetween. Each ground conductor 420 has a first
contact end 422 connectable to the daughtercard, a second contact
end 424 connectable to the second contact ends 324 of the
corresponding ground conductors 320 of the first differential
electrical connector 300, and an intermediate portion 426
therebetween. The drawings show the first contact end 412 of each
signal conductor 410 and the first contact end 422 of the ground
conductor 420 as press-fit contact tails. However, it should be
apparent to one of ordinary skill in the art that the first contact
ends 412, 422 may take any form, e.g., pressure-mount contacts,
paste-in-hole solder attachment, contact tails adapted for
soldering, etc., for connecting to the daughtercard.
[0043] In the preferred embodiment, the ground conductor 420 is a
ground shield that provides electrical shielding to the
corresponding signal conductors 410 of the wafer 401. However, a
plurality of ground conductors may be utilized instead of a single
ground shield, as known in the art. Provided in the second contact
end 424 of the ground shield 420 are slits 430. Preferably, the
slits 430 are positioned between adjacent differential pairs of
signal conductors 410.
[0044] Each of the slits 430 is configured to receive and
electrically connect to a ground conductor 440 that is oriented
perpendicular to the ground conductor 420 of the wafer 401. Note
that the ground conductor 440 is preferably configured as a ground
strip, as shown in FIG. 6. Each ground strip 440 electrically
connects to each ground conductor 420 of the wafers 401. In this
manner, the ground strips 440 electrically separate adjacent second
contact ends 414 of differential pairs of signal conductors 410.
The grid-like shielding pattern formed by the ground shields 420
and the ground strips 440 provides effective electrical shielding
(e.g., from electrical noise) for the differential pairs of signal
conductors 410. This grid-like shielding pattern formed by the
ground shields 420 and the ground strips 440 is housed in a shroud
450, which is preferably insulative.
[0045] Referring now to FIG. 8A, there is shown a top view of a
portion of the first side 112 of the midplane 110 of FIG. 1, with a
part of the surface removed to reveal a ground plane layer 150.
FIG. 8B shows a top view of the portion (same portion as in FIG. 8A
and viewed from the same perspective as FIG. 8A) of the second side
114 of the midplane 110 of FIG. 1, with a part of the surface
removed to reveal a ground plane layer 170. The portion of the
midplane 110 shown in FIGS. 8A and 88 correspond to the footprint
of a differential electrical connector, such as the differential
electrical connector 300, that connects to the midplane 110. Note
that the portion of the first side 112 of the midplane 110 shown in
FIG. 8A provides a similar interface for a differential electrical
connector as the portion of the second side 114 of the midplane 110
shown in FIG. 8B.
[0046] As known in the art, a midplane is generally a multi-layer
printed circuit board formed of multiple layers of dielectric
substrates with signal traces or planes formed on one or more of
the dielectric layers. Further, the multi-layer printed circuit
board will typically have a ground plane formed on one or more of
the dielectric layers. Vias generally extend between layers of a
multi-layer printed circuit board. Vias which extend through all
layers of a multi-layer printed circuit board are sometimes
referred to as through-holes. The vias are usually formed after the
layers of substrates are formed into a printed circuit board.
Conductive vias generally intersect signal traces on different
layers. Conductive vias also interconnect components mounted on the
printed circuit board to signal traces on inner layers of the
printed circuit board.
[0047] FIG. 8A shows the ground plane 150, which is formed on one
of the dielectric layers of the midplane 110. FIG. 88 shows the
ground plane 170, which is formed on one of the dielectric layers
of the midplane 110. Typically, the midplane 110 will have more
than one ground plane, and ground planes 150, 170 will be different
ground planes. However, the ground planes 150, 170 may be the same
ground plane without departing from the scope of the present
invention. The midplane 110 has a plurality of vias 152, 154
extending from the first side 112 to the second side 114. Thus,
vias 152, 154 are through-hole vias. The vias 152 are signal
connecting conductive vias and the vias 154 are ground connecting
conductive vias. Note that the signal connecting conductive vias
152 on the first side 112 of the midplane 110 provide first signal
launches 155 for differential pairs of the differential connector
connected to the first side 112 and the signal connecting
conductive vias 152 on the second side 114 of the midplane 110
provide second signal launches 175 for differential pairs of the
differential connector connected to the second side 114. The ground
connecting conductive vias 154 on the first side 112 of the
midplane 110 provide first ground launches 157 for differential
pairs of the differential connector connected to the first side 112
and the ground connecting conductive vias 154 on the second side
114 of the midplane 110 provide second ground launches 177 for
differential pairs of the differential connector connected to the
second side 114.
[0048] The first signal launches 155 are provided in a plurality of
rows 156a-156f, as shown in FIG. 8A, for electrically connecting to
a differential connector. In the example of FIG. 8A, the six rows
156a-156f shown correspond to the six rows 330a-330f of
differential pairs of signal conductors 310 of the first
differential electrical connector 300 shown in FIGS. 4 and 5. Each
signal connecting conductive via 152 of a pair corresponding to a
differential pair of signal conductors is electrically isolated
from the other signal connecting conductive via 152 of the pair.
Further, for each pair of signal connecting conductive vias 152
corresponding to a differential pair of signal conductors, there is
an area 158 surrounding the pair of signal connecting conductive
vias 152 that is free of the ground plane 150. This free area 158
is sometimes referred to as an "antipad." It has been found that by
ensuring that the area surrounding the pair of signal connecting
conductive vias 152 is free of the ground plane 150 (while a region
between adjacent pairs of signal connecting conductive vias 152
includes the ground plane 150), there is significantly improved
signal performance. Note that while the preferred embodiment of the
invention illustrates a substantially oval antipad 158, the antipad
158 may take other shapes. See, e.g., U.S. Pat. No. 6,607,402,
incorporated by reference herein. For example, the antipad 158 may
be substantially rectangular in shape or may be substantially
figure-8 in shape.
[0049] As with the first contact ends 312 of each differential pair
of signal conductors 310 of the first differential electrical
connector 300 (FIGS. 4 and 5), one signal connecting conductive via
152 of a pair lies along a first line 160 and the other signal
connecting conductive via 152 of the pair lies along a second line
162 that is parallel to and spaced from the first line 160. Also,
as with the first contact ends 312 of each differential pair of
signal conductors 310 of the first differential electrical
connector 300, the signal connecting conductive vias 152 of a pair
are offset. Preferably, the signal connecting conductive vias 152
of a pair are offset substantially at a forty-five (45) degree
angle relative to the orientation of the rows 156a-156f. Note that
because of this offset of the signal connecting conductive vias 152
of a pair, the antipad 158 surrounding the pair is also preferably
oriented substantially at a forty-five (45) degree angle relative
to the orientation of the rows 156a-156f.
[0050] The first ground launches 157 are also provided in the
plurality of rows 156a-156f, as shown in FIG. 8A, for electrically
connecting to a differential connector. For each of the rows
156a-156f, the first ground launches 157 are provided along a line
164 that is adjacent to and substantially parallel to the first and
second lines 160, 162. Preferably, this line 164 is spaced between
the first and second lines 160, 162. Further, for each of the rows
156a-156f, the number of first ground launches 157 is preferably
greater than the number of pairs of first signal launches 155. In
the example of FIG. 8A, the number of first ground launches 157 of
a row 156a-156f is seven (7), while the number of pairs of first
signal launches 155 of a row 156a-156f is six (6).
[0051] Referring now to FIG. 8B, there is shown the second signal
launches 175 that are provided in a plurality of columns 176a-176f
for electrically connecting to a differential connector. In the
exemplary illustration of FIG. 8B, the six columns 176a-176f shown
correspond to the six rows 330a-330f of differential pairs of
signal conductors 310 of the first differential electrical
connector 300 shown in FIGS. 4 and 5. These columns 176a-176f are
orthogonal to the rows 156a-156f of FIG. 8A. This orthogonality of
the rows 156a-156f on the first side 112 of the midplane 110
relative to the columns 176a-176f on the second side 114 of the
midplane 100 corresponds to and accommodates the orthogonality of
the daughtercards 130A-130C on the first side 112 relative to the
daughtercards 120A-120D on the second side 114 (see FIG. 1).
[0052] Same as in FIG. 8A, each signal connecting conductive via
152 of a pair corresponding to a differential pair of signal
conductors is electrically isolated from the other signal
connecting conductive via 152 of the pair. In fact, the
through-hole signal connecting conductive vias 152 shown 8A are the
same through-hole signal connecting conductive vias 152 shown in
FIG. 8B. Thus, for the portion of the midplane 110 shown in FIGS.
8A and 88, the number of first signal launches 155 equals the
number of second signal launches 175. Note that by designing a
differential electrical connector that provides a substantially
square footprint for connecting to the midplane 110 (such as the
first differential electrical connector 300), it is possible to
provide the midplane 110 that utilizes the same through-hole signal
connecting conductive vias 152 for connecting a differential
electrical connector to the first side 112 and a differential
electrical connector to the second side 114. In this manner, the
midplane design of the present invention (i) significantly reduces
the required layers and size of the midplane, (ii) provides for an
easier to design and manufacture midplane, (iii) improves the
signal characteristics of the transmitted signals, and (iv)
significantly reduces the materials and cost of the manufactured
midplane.
[0053] For each pair of signal connecting conductive vias 152
corresponding to a differential pair of signal conductors, there is
an area 178 surrounding the pair of signal connecting conductive
vias 152 that is free of the ground plane 170. This antipad 178 is
similar to the antipad 158 of FIG. 8A. It has been found that by
ensuring that the area surrounding the pair of signal connecting
conductive vias 152 is free of the ground plane 170 (while a region
between adjacent pairs of signal connecting conductive vias 152
includes the ground plane 170), there is significantly improved
signal performance. Note that while the preferred embodiment of the
invention illustrates a substantially oval antipad 178, the antipad
178 may take other shapes. For example, the antipad 178 may be
substantially rectangular in shape or may be substantially figure-8
in shape.
[0054] As with the first contact ends 312 of each differential pair
of signal conductors 310 of the first differential electrical
connector 300 (FIGS. 4 and 5), one signal connecting conductive via
152 of a pair lies along a third line 180 and the other signal
connecting conductive via 152 of the pair lies along a fourth line
182 that is parallel to and spaced from the third line 180. Also,
as with the first contact ends 312 of each differential pair of
signal conductors 310 of the first differential electrical
connector 300, the signal connecting conductive vias 152 of a pair
are offset. Preferably, the signal connecting conductive vias 152
of a pair are offset substantially at a forty-five (45) degree
angle relative to the orientation of the columns 176a-176f. Note
that because of this offset of the signal connecting conductive
vias 152 of a pair, the antipad 178 surrounding the pair is also
preferably oriented substantially at a forty-five (45) degree angle
relative to the orientation of the columns 176a-176f.
[0055] The second ground launches 177 are also provided in the
plurality of columns 176a-176f, as shown in FIG. 8B, for
electrically connecting to a differential connector. For each of
the columns 176a-176f, the second ground launches 177 are provided
along a line 184 that is adjacent to and substantially parallel to
the third and fourth lines 180, 182. Preferably, this line 184 is
spaced between the third and fourth lines 180, 182. As described
above, the columns 176a-176f of the second side 114 are orthogonal
to the rows 156a-156f of the first side 112. Thus, the third and
fourth lines 180, 182 are orthogonal to the first and second lines
160, 162 of FIG. 8A. For each of the columns 176a-176f, the number
of second ground launches 177 is preferably greater than the number
of pairs of second signal launches 175. In the example of FIG. 8B,
the number of second ground launches 177 of a column 176a-176f is
seven (7), while the number of pairs of second signal launches 175
of a column 176a-176f is six (6).
[0056] FIGS. 9A through 9D and FIGS. 10A through 10D illustrate the
advantage of offset contact tails associated with the differential
midplane connector 300 according to an embodiment the present
invention. FIG. 9A illustrates a cross section through a
traditional connector near the second contact end region. FIG. 9A
shows that connector 300 has a pair-wise orientation. As used
herein, "pair-wise" orientation indicates that the connector is
designed with pairs of signal conductors adapted to preferentially
electrically couple to each other. For example, the direction of
the displacement between one conductor of a pair near the first
contact end, e.g., 312(a), and the second conductor of the pair
near the first contact end, e.g., 312(b), provides the orientation
of the pair.
[0057] Multiple design techniques may be used to create a pair-wise
orientation of a connector. These design techniques may be used
alone or in combination. In the illustrated embodiment, shields are
used to create preferential coupling between pairs. A pair-wise
orientation is created because the signal conductors of each pairs
are oriented in the connector with the signal conductors of a pair
displaced from each other in a direction parallel to the
shielding.
[0058] As another example of a technique to create a pair-wise
orientation, the signal conductors of a pair may be routed closer
to each other than to the next nearest signal conductor.
[0059] A pair-wise orientation is desirable for a differential
connector because it increases the coupling between the conductors
that form a pair and decreases coupling to signal conductors that
form an adjacent pair. As a result, each differential signal path
is less susceptible to extraneous electromagnetic fields that could
induce noise. Further, the coupling between adjacent pairs is
reduced, thereby reducing cross-talk within the connector, allowing
the connector to operate with greater signal integrity. With
greater signal integrity, more signals may be routed through the
connector or signals of higher frequency may pass through the
connector.
[0060] In FIG. 9A, second contact ends 314A and 314B forming a
differential pair are aligned along column 910A. Such an alignment
is similar to a connector 300 mounted on surface 112 to receive a
connector on board 130A, such as shown in FIG. 1, with column 910A
being aligned along an axis (shown here in the z axis) that is
parallel to rows 330a-330f.
[0061] FIG. 9C shows a via hole pattern needed to receive first
contact ends from signal conductors in a traditional connector
mounted as shown in FIG. 9A if offset first contact ends are not
used. FIG. 9C shows the hole pattern having the same alignment
along an axis as the signal conductors for the connector in FIG.
9A, shown here in the z axis.
[0062] FIG. 9B shows a cross section of a connector with the second
contact ends of a differential pair aligned along row 920A. Such an
alignment is similar to a connector 300 mounted on surface 114 to
receive a connector on board 120A, such as shown in FIG. 1, with
row 920A being aligned along an axis (shown here in the x axis)
that is parallel to rows 330a-330f. Because board 120A is
perpendicular to board 130A, the pair-wise orientation and the
alignment of the connector in FIG. 9B is orthogonal to the
pair-wise orientation and the alignment of the connector in FIG.
9A.
[0063] FIG. 9D shows a via hole pattern needed to receive first
contact ends from signal conductors in a traditional connector
mounted as shown in FIG. 9B if offset first contact ends are not
used. FIG. 9D shows the hole pattern having the same alignment
along an axis as the signal conductors for the connector in FIG.
9B, shown here in the x axis.
[0064] When the via hole patterns of FIG. 9C and 9D are formed on
opposite sides of a midplane, no amount of shifting of the hole
pattern allows both holes for the same pair to be aligned. For
example, if holes 930A and 940A are aligned, holes 930B and 940B
cannot align. To connect a signal pair on one side of a midplane to
another using a traditional connector design, routing traces within
the midplane are required to make connections between the vias in
which the connectors on opposite sides of the midplane are
mounted.
[0065] FIGS. 10A through 10D illustrates an advantage that can be
obtained with offset contact tails, 312(a), 312(b) according to an
embodiment of the present invention. FIGS. 10A and 108 show the
second contact ends 314A, 314B and 324A aligned along the same axes
(shown here in the z and x axes, respectively) as previously shown
in FIGS. 9A and 9B. With a forty-five (45) degree offset associated
with the orientation of the contact tails 312(a), 312(b) from the
second contact end position, there is a corresponding forty-five
(45) degree offset for hole patterns associated with each
differential pair. Thus, FIGS. 10C and 10D show via hole patterns
needed to receive first contact ends 312(a) and 312(b) from signal
conductors 310 as mounted in FIGS. 10A and 10B, respectively. FIG.
10C shows the hole pattern having an alignment along an axis
z'-that has an angle about forty-five degrees from the alignment
(shown here in the z axis) of the second contact ends, 314 as shown
in FIG. 10A. Similarly, FIG. 10D shows the hole pattern having an
alignment along an axis x' that has an angle about forty-five
degrees from the alignment (shown here in the x axis) of the second
contact ends, 314 as shown in FIG. 10B. As a result, even though
the mating contact portions 314 of connectors 300 on opposing sides
of midplane 110 have orthogonal pair-wise orientations and
alignments, the holes for differential pairs on opposing sides of
midplane 110 have the same pattern and may be aligned. If the hole
patterns on opposite sides of the midplane align, connectors in
opposite sides of the midplane may be inserted into the same
vias.
[0066] This alignment is shown in FIG. 11A, which shows connectors
300A and 300B mounted on opposite sides of midplane 110. Connector
300A mates with connector 400A. Connector 300B mates with connector
400B. Because connectors 400A and 400B are attached to printed
circuit boards that are mounted with different orientations, the
pair-wise orientation of connectors 400A and 400B have different
orientations. In the illustrated embodiment, connectors 400A and
4008 are mounted orthogonal to each other. To mate with connectors
400A and 4008, connectors 300A and 300B must similarly be mounted
orthogonal to each other. Consequently, connector 300A has a
pair-wise orientation and alignment and connector 300B has a
pair-wise orientation and alignment.
[0067] Despite the different pair-wise orientations of connectors
300A and 300B, the offset pattern of contact tails 312 allows the
contact tails 312 of connectors 300A and 300B to be mounted using
one set of via holes. Further, every pair of signal conductors in
connector 300A may be mounted in the same two vias as a pair of
signal conductors in connector 300B.
[0068] FIG. 11B is a side view of a pair of signal conductors
within connectors 300A and 300B mounted on opposing sides of a
midplane 110. The signal conductors have an orientation and
alignment on one side of the board and an orientation and alignment
on the opposing side. Despite orthogonal orientations, the offset
of the contact tails of both pairs allows the contact tails to
align so that they may be connected through vias 1110a and 1110b,
respectively.
[0069] In this way, the two signals that form one differential
signal are routed together from a daughter card on one side of
midplane 110, through a first set of connectors to midplane 110,
through midplane 110 to a second set of connectors to a second
daughter card. The two signal conductors are kept together as a
pair, thereby providing desirable signal integrity properties.
Further, the transmission path may be optimized for carrying
differential signals. As described above, each connector may be
constructed with shielding, signal conductor positioning or other
structures that provide a pair-wise orientation that increases the
signal integrity when carrying differential signals.
[0070] In the midplane, connections between the signal conductors
on opposing sides of the midplane may be made using only the vias
of the midplane to carry the signal. No traces within the midplane
are needed to carry differential signals from one side of the
midplane to another. Eliminating traces, and transitions between
vias and traces, within the midplane means less distortion of the
signal occurs in the midplane, further increasing the signal
integrity of the connector. Further, FIG. 8A and 8B illustrate that
ground clearances around differential pairs may be structured to
further improve the integrity of signals passing through the
midplane oriented as differential pairs.
[0071] A number of preferred and alternative embodiments of the
invention have been described. Nevertheless, it will be apparent to
one of ordinary skill in the art that various modifications and
alterations of this invention may be made without departing from
the scope and spirit of this invention. Accordingly, other
embodiments are within the scope of the appending claims.
* * * * *