U.S. patent application number 15/207643 was filed with the patent office on 2016-11-03 for transceiver system.
The applicant listed for this patent is Samtec, Inc.. Invention is credited to Chadrick P. FAITH, Keith R. GUETIG, John A. MONGOLD, Randall E. MUSSER, Dale F. SCHMELZ.
Application Number | 20160322769 15/207643 |
Document ID | / |
Family ID | 49548933 |
Filed Date | 2016-11-03 |
United States Patent
Application |
20160322769 |
Kind Code |
A1 |
FAITH; Chadrick P. ; et
al. |
November 3, 2016 |
TRANSCEIVER SYSTEM
Abstract
A transceiver for a two-connector system includes a circuit
board, at least one cable attached to the circuit board, and a
housing arranged to contain the circuit board. The two-connector
system includes a front connector and a back connector. When the
transceiver is connected to the two-connector system, a front edge
of the circuit board is arranged to engage with the front connector
and an intermediate portion of the circuit board is arranged to
engage with the back connector.
Inventors: |
FAITH; Chadrick P.; (New
Albany, IN) ; GUETIG; Keith R.; (New Albany, IN)
; SCHMELZ; Dale F.; (New Albany, IN) ; MUSSER;
Randall E.; (New Albany, IN) ; MONGOLD; John A.;
(New Albany, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samtec, Inc. |
New Albany |
IN |
US |
|
|
Family ID: |
49548933 |
Appl. No.: |
15/207643 |
Filed: |
July 12, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13950628 |
Jul 25, 2013 |
9419403 |
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15207643 |
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13895571 |
May 16, 2013 |
8787711 |
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13950628 |
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13758464 |
Feb 4, 2013 |
8588562 |
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13895571 |
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13539173 |
Jun 29, 2012 |
8588561 |
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13758464 |
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61787274 |
Mar 15, 2013 |
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61636005 |
Apr 20, 2012 |
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61504072 |
Jul 1, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 6/428 20130101;
H01R 43/26 20130101; H01R 43/20 20130101; H04B 10/40 20130101; H01R
12/716 20130101; H01R 13/6275 20130101; G02B 6/4284 20130101; Y10T
29/49149 20150115; H01R 12/598 20130101; H01R 43/0256 20130101;
H01R 12/70 20130101; H01R 12/62 20130101 |
International
Class: |
H01R 43/20 20060101
H01R043/20; H01R 12/62 20060101 H01R012/62; H04B 10/40 20060101
H04B010/40; H01R 12/71 20060101 H01R012/71; H01R 13/627 20060101
H01R013/627; H01R 43/02 20060101 H01R043/02; H01R 12/59 20060101
H01R012/59; H01R 12/70 20060101 H01R012/70 |
Claims
1. A method of manufacturing a transceiver, comprising: computer
numerical control routing a circuit board; laser routing at least
one edge portion of the circuit board to obtain a tolerance of
+/-0.001'' for mating with a 0.5-mm pitch connector; and arranging
the circuit board within a housing.
2. The method of claim 1, further comprising: fusibly connecting a
plurality of cables to a plurality of pads of the circuit board;
coating a first epoxy over at least one cable of the plurality of
cables and at least one pad of the plurality of pads; and curing
the first epoxy.
3. The method of claim 2, further comprising: after curing the
first epoxy, coating a second epoxy over at least one other cable
of the plurality of cables and at least one other pad of the
plurality of pads; and curing the second epoxy.
4. The method of claim 2, further comprising: before curing the
first epoxy, coating a second epoxy over at least one other cable
of the plurality of cables and at least one other pad of the
plurality of pads; and curing the first epoxy and the second epoxy
simultaneously.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to transceivers and IC
packages. More specifically, the present invention relates to
transceivers that can be directly plugged into an IC package.
[0003] 2. Description of the Related Art
[0004] Known miniature transceivers include copper transceivers and
optical transceivers. Optical transceivers are typically used for
applications that require long signal transmissions or high data
rates. However, known optical transceivers are expensive, and thus
are not preferable for applications that do not require an optical
connection, for example, applications with a short signal
transmission length or applications that use low speed signals.
Examples of known optical transceivers are disclosed in U.S. Patent
Application Nos. Ser. No. 13/539,173; 61/504,072; and 61/636,005,
the entire contents of which are hereby incorporated by reference.
Much of the cost of these optical transceivers is due to the
optical engines within the optical transceivers that convert light
to electricity and electricity to light. Examples of the optical
engines are disclosed in U.S. Pat. Nos. 7,329,054; 7,648,287;
7,766,559; and 7,824,112; U.S. Patent Application Publication Nos.
2008/0222351, 2011/0123150, and 2011/0123151; and U.S. Patent
Application No. 61/562,371, the entire contents of which are hereby
incorporated by reference.
[0005] In contrast, known copper transceivers are less expensive
than known optical transceivers, but provide lower data rates and
are typically unusable for longer signal transmissions. However,
because known connectors are not designed to accept both optical
transceivers and copper transceivers, a system that uses a known
copper transceiver must be redesigned for use with an optical
transceiver if it is desired to increase the data rate or signal
transmission distance.
[0006] Furthermore, known copper transceivers have a number of
known problems. Typically known copper transceivers include flying
leads, which are typically only used for testing/debugging. In
particular, known copper transceivers have impedance
discontinuities in the cable termination region, that is, in the
area where cable(s) are connected to a circuit board or other
electrical components within the transceiver. The connection
density in the cable termination region is also limited by the
pitch of the cable(s) that are used with the transceiver. Further,
thermoplastic housings often require screws and other hardware that
add expense, and latching systems are often not very robust, which
can lead to accidental disconnection of the transceiver.
[0007] Moreover, known transceivers use circuit boards that
typically have a routing tolerance of +/-0.005'', which is not a
tight enough tolerance to mate to a 0.5-mm pitch connector.
Accordingly, the pitch of a typical connector used with known
transceivers is typically at least 0.635 mm (0.025'').
[0008] One example of a known miniature transceiver is a Quad Small
Form-factor Pluggable (QSFP or QSFP+) transceiver. QSFP
transceivers are compact, hot-pluggable transceivers that include
connectors that are designed to accept both copper and optical
transceivers. However, a typical QSFP transceiver uses a relatively
large receptacle cage and a mating connector with a 0.8 mm pitch,
which results in the QSFP transceiver requiring a significant
amount of space on the circuit board to which the QSFP transceiver
is connected.
[0009] Transceiver size may be reduced and/or performance increased
by using precision soldering or intricate hand soldering. However,
these methods increase expense and may cause defects.
[0010] RF connectors or other expensive components may be included
with a known miniature transceiver to improve performance. However,
such connectors or components take up space on a circuit board or
device to which the transceiver is to be connected and increase
overall expense of the system that includes the transceiver.
Similarly, custom or exotic fixtures may be used with a known
miniature transceiver to improve performance. Such fixtures
include, for example, components used in high-end vision systems or
components manufactured using active alignment and registration
automation (e.g., using laser alignment). However, such fixtures
typically require expensive tooling, have complex design concerns,
and have long set-up times for manufacturing, which increase
overall expense of the system that includes the transceiver.
Furthermore, custom or exotic fixtures are difficult and expensive
to repair.
[0011] Snap features and press fit bosses have been used to secure
known miniature transceivers in place. For example, a known
miniature transceiver may include one or more pins that
mechanically deform when inserted into corresponding holes of a
known connector to secure the transceiver to the connector.
However, these components are relatively unreliable and may lead to
undesirable signal interruptions or mechanical failures. Friction
latches have been used to secure known miniature transceivers in
place. For example, a known connector may include one or more
brackets that press against the sides of a known miniature
transceiver to secure the transceiver to the connector. However,
friction latches typically have a low withdrawal force, which
allows transceivers to accidentally un-mate and cause transmission
link failures or other system failures.
[0012] Termination-region density improvements have been made by
using a cable with smaller gauge wires, which reduces pitch and
increases density. However, using smaller gauge wires reduces
performance of the transceiver, particularly by limiting data rate
and signal transmission distance.
[0013] Furthermore, if conventional manufacturing methods are used
to produce circuit boards with 0.5-mm pad pitches, high yield
losses result due to the requirements for tolerances of the circuit
boards. Accordingly, conventional manufacturing methods increase
expense due to a high proportion of circuit boards rejected during
sorting. In particular, conventional manufacturing methods often
provide a yield of acceptable circuit boards that is several orders
of magnitude lower than the rejected circuit boards.
SUMMARY OF THE INVENTION
[0014] To overcome the problems described above, the preferred
embodiments of the present invention provide a two-connector
assembly including front and back connectors. The front connector
preferably is a connector that is configured to receive a front
edge of a circuit board from a transceiver, and the back connector
preferably is a connector that is configured to receive an
intermediate portion of the circuit board when the front edge of
the circuit board is inserted into the front connector. Various
preferred embodiments of the present invention provide a
high-density connection for cables that has a low-cost, is easy to
deploy, has few parts, and has sufficient mechanical retention.
[0015] A transceiver according to a preferred embodiment of the
present invention includes a circuit board, at least one cable
attached to the circuit board, and a housing arranged to contain
the circuit board. The two-connector system includes a front
connector and a back connector. When the transceiver is connected
to the two-connector system, a front edge of the circuit board is
arranged to engage with the front connector and an intermediate
portion of the circuit board is arranged to engage with the back
connector.
[0016] The housing preferably includes a clip arranged to engage
with at least one slot of the back connector. The housing is
preferably arranged such that the clip is aligned to engage with
the at least one slot of the back connector when the front edge of
the circuit board is engaged with the front connector. The circuit
board preferably includes at least one notch and the housing
preferably includes a clip arranged to pass through the at least
one notch of the circuit board.
[0017] The at least one cable preferably includes at least one of a
coaxial cable, a shielded coaxial cable, a twinaxial cable, a
twisted pair cable, a shielded twisted pair cable, and a shielded
twinax cable. Preferably, a conductor of the coaxial cable is
electrically connected to a pad of the circuit board and a
conductive shield of the coaxial cable is electrically connected to
a ground plane of the circuit board.
[0018] An epoxy preferably covers the at least one cable and at
least one pad of the circuit board. A dielectric constant of the
epoxy is preferably within about .+-.20% of a dielectric constant
of the circuit board, for example. Preferably, the epoxy and the
circuit board each have a dielectric constant between about 3.9 and
about 4.2, for example.
[0019] The at least one cable preferably includes a first cable and
a second cable. Preferably, electrical traces that are electrically
connected to the first cable are arranged only on a top surface of
the circuit board. Electrical traces that are electrically
connected to the second cable are preferably arranged on a bottom
surface of the circuit board. Preferably, a first epoxy covers the
first cable and a first pad of the circuit board and a second epoxy
covers the second cable and a second pad of the circuit board.
Preferably, the at least one cable is electrically connected to at
least one pad near the front edge of the circuit board.
[0020] The housing preferably includes undercuts arranged to
receive at least one edge of the circuit board and alignment pins
arranged to be inserted into holes in the circuit board.
[0021] The front connector is preferably a 0.5-mm pitch edge-card
connector and the circuit board preferably has a routing tolerance
of +/-0.001'' for engaging with the front connector, for
example.
[0022] A two-connector system according to a preferred embodiment
of the present invention includes a circuit board, a front
connector and a back connector connected to the circuit board, and
a transceiver connected to the circuit board through the front
connector and the back connector. The transceiver includes at least
one cable attached to the circuit board and a housing arranged to
receive the circuit board. A front edge of the circuit board is
arranged to engage with the front connector and an intermediate
portion of the circuit board is arranged to engage with the back
connector.
[0023] A method of manufacturing a transceiver according to a
preferred embodiment of the present invention includes computer
numerical control routing a circuit board, laser routing at least
one edge portion of the circuit board to obtain a tolerance of
+/0.001'' for mating with a 0.5-mm pitch connector, and arranging
the circuit board within a housing.
[0024] Preferably, the method further includes fusibly connecting a
plurality of cables to a plurality of pads of the circuit board,
coating a first epoxy over at least one cable of the plurality of
cables and at least one pad of the plurality of pads, and curing
the first epoxy.
[0025] The method preferably includes, after curing the first
epoxy, coating a second epoxy over at least one other cable of the
plurality of cables and at least one other pad of the plurality of
pads and curing the second epoxy. Alternatively, the method
preferably includes, before curing the first epoxy, coating a
second epoxy over at least one other cable of the plurality of
cables and at least one other pad of the plurality of pads and
curing the first epoxy and the second epoxy simultaneously.
[0026] The above and other features, elements, steps,
characteristics and advantages of the present invention will become
more apparent from the following detailed description of preferred
embodiments of the present invention with reference to the attached
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a perspective view of a two-connector assembly
with a transceiver and a two-connector assembly according to a
preferred embodiment of the present invention.
[0028] FIG. 2 is another perspective view of the two-connector
assembly shown in FIG. 1.
[0029] FIG. 3 is a top view of a circuit board of the transceiver
shown in FIG. 1.
[0030] FIG. 4 is a bottom view of the circuit board shown in FIG.
3.
[0031] FIG. 5 is a perspective view of a coaxial cable used in the
two-connector assembly shown in FIG. 1.
[0032] FIG. 6 is a perspective view of a lower coaxial cable
connected to the circuit board shown in FIG. 3.
[0033] FIG. 7 is a top view of the lower coaxial cable connected to
the circuit board shown in FIG. 3.
[0034] FIG. 8 is a perspective view of an upper coaxial cable and
the lower coaxial cable connected to the circuit board shown in
FIG. 3.
[0035] FIG. 9 is a top view of the upper coaxial cable and the
lower coaxial cable connected to the circuit board shown in FIG.
3.
[0036] FIG. 10 is a top side view of the upper coaxial cable and
the lower coaxial cable connected to the circuit board shown in
FIG. 3.
[0037] FIG. 11 is a bottom perspective view of the transceiver
shown in FIG. 1.
[0038] FIG. 12 is a top perspective view of a U-clip of the
transceiver shown in FIG. 1.
[0039] FIG. 13 is a bottom perspective view of the U-clip shown in
FIG. 12.
[0040] FIG. 14 is a top perspective view of a substrate of the
two-connector assembly shown in FIG. 1.
[0041] FIG. 15 is a top perspective view of a back connector of the
two-connector assembly shown in FIG. 1.
[0042] FIG. 16 is a top perspective view of the front connector of
the two-connector assembly shown in FIG. 1.
[0043] FIG. 17 is a top-front perspective view of the two-connector
assembly of FIG. 1 before the transceiver is engaged with the
two-connector assembly.
[0044] FIG. 18 is a rear-front perspective view of the
two-connector assembly of FIG. 1 before the transceiver is engaged
with the two-connector assembly.
[0045] FIG. 19 is a top view of the two-connector assembly of FIG.
1 before the transceiver is engaged with the two-connector
assembly.
[0046] FIG. 20 is a bottom view of the two-connector assembly of
FIG. 1 before the transceiver is engaged with the two-connector
assembly.
[0047] FIG. 21 is a top perspective view of the two-connector
assembly shown in FIG. 1 with the U-clip of the transceiver engaged
with the back connector and the circuit board.
[0048] FIG. 22 is a top perspective view of the two-connector
assembly shown in FIG. 1 with the U-clip of the transceiver engaged
with the circuit board, where the back connector is not shown.
[0049] FIGS. 23A-23C are top views showing routing of the circuit
board shown in FIG. 3.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0050] FIGS. 1 and 2 are perspective views of a two-connector
assembly with a transceiver 100 and a two-connector assembly that
includes a front connector 40 and a back connector 50. The
transceiver 100 includes a housing 20 and a circuit board 10
connected to an upper coaxial cable 30a and a lower coaxial cable
30b. The front connector 40 and the back connector 50 are
preferably mounted to a substrate 60. Preferably, the front
connector 40 is an edge-card connector.
[0051] FIGS. 3 and 4 are, respectively, top and bottom views of the
circuit board 10 of the transceiver 100. As shown in FIG. 3, a top
surface of the circuit board 10 includes upper termination pads
11a, upper traces 11b, upper edge pads 11c, upper ground pads 12,
and ground planes 16. As shown in FIG. 4, a bottom surface of the
circuit board 10 includes lower termination pads 13a, lower traces
13b, lower edge pads 13c, lower ground pads 14, and, optionally,
back pads 15. Accordingly, as described below, the circuit board 10
provides electrical and mechanical connections to the upper coaxial
cable 30a and the lower coaxial cable 30b.
[0052] As shown in FIGS. 1-4, the housing 20 preferably includes a
U-clip 28, and the circuit board 10 preferably includes
pass-through notches 18 and holes 19. As described below, the
pass-through notches 18 are arranged to receive legs 28a of the
U-clip 28, and the holes 19 are arranged to receive heat-staked
alignment pins 29 of the housing 20.
[0053] FIG. 5 is a perspective view of a coaxial cable 30 used in
the two-connector assembly shown in FIGS. 1 and 2. As shown in
FIGS. 1 and 2, two coaxial cables 30 are included in the
two-connector assembly as the upper coaxial cable 30a and the lower
coaxial cable 30b.
[0054] As shown in FIG. 5, the coaxial cable 30 includes conductors
31, insulators 32, conductive shields 33, and outer coatings 34.
Preferably, the coaxial cable 30 is a ribbonized coaxial cable,
although other types of cables or wiring may be used, for example,
a shielded coaxial cable, a twinaxial cable, a twisted pair cable,
a shielded twinaxial cable, a shielded twisted pair cable, and the
like.
[0055] The conductors 31 and the conductive shields 33 are
conductive elements of the coaxial cable 30. The conductors 31 are
arranged to carry electrical signals, whereas the conductive
shields 33 typically provide a ground connection. The conductive
shields 33 also provide electrical isolation for the conductors 31
and reduce crosstalk between neighboring conductors 31. Each of the
insulators 32 is preferably formed of a dielectric material with a
constant or substantially constant cross-section to provide
constant or substantially constant electrical properties for its
associated conductor 31. The insulators 32 preferably have round,
oval, rectangular, or square cross-sectional shapes, but may be
formed or defined in any other suitable shape. The outer coatings
34 of the coaxial cable 30 protect the other layers of the coaxial
cable 30 and prevent the conductive shields 33 from coming into
contact with other electrical components to significantly reduce or
prevent occurrence of an electrical short.
[0056] FIGS. 6-10 show connections between the circuit board 10 and
the coaxial cables 30, including the upper coaxial cable 30a and
the lower coaxial cable 30b.
[0057] As shown in FIGS. 6-10, a portion of each of the outer
coatings 34 and a portion of each of the insulators 32 of each of
the upper coaxial cable 30a and the lower coaxial cable 30b is
preferably removed to allow the conductive shield 33 to be
connected to a corresponding ground plane 16 of the circuit board
10. As shown in FIGS. 6-10, the conductive shields 33 of each of
the upper coaxial cable 30a and the lower coaxial cable 30b are
preferably commonly connected to ground planes 16 of the circuit
board 10, and grounding bars 36 preferably connect the conductive
shields 33 to the ground planes 16. The grounding bars 36 are
preferably soldered to the circuit board 10 (for example, by
hot-bar soldering) to provide a high-capacity electrical ground for
the coaxial cables 30 and to help mechanically secure the coaxial
cables 30 to the circuit board 10. Furthermore, the conductive
shields 33 of the upper coaxial cable 30a and the lower coaxial
cable 30b are preferably connected to a common ground through the
ground planes 16. However, alternative grounding connections may be
used. For example, one or more drain wires (not shown) may be
connected to conductive shields 33 and the corresponding ground
plane 16, or one or more of the conductors 31 may be used for a
ground connection.
[0058] As shown in FIGS. 6-10, the conductors 31 of the upper
coaxial cable 30a and the lower coaxial cable 30b are preferably
fusibly connected (for example, by solder), respectively, to the
upper termination pads 11a and the lower termination pads 13a of
the circuit board 10.
[0059] After electrically connecting one of the coaxial cables 30
to the circuit board 10, epoxy is preferably deposited in the
termination region where the coaxial cable 30 connects to the
circuit board 10. As shown in FIGS. 6-10, an epoxy-coated
termination 35 is provided by depositing epoxy in each of the
termination regions where the upper coaxial cable 30a and the lower
coaxial cable 30b respectively connect to the upper termination
pads 11a and the lower termination pads 13a of the circuit board
10.
[0060] Preferably, the epoxy is cured when exposed to an
ultraviolet (UV) light, although other types of epoxy may be used
(e.g., thermally-cured epoxy, two-part epoxy, light-sensitive
epoxy, pressure sensitive epoxy, other suitable epoxy or similar
materials). The epoxy may include, for example, glass epoxy, epoxy
with aramid fibers, a blend of epoxy and bismaleimide-triazine, and
the like. A non-exhaustive list of possible epoxy formulations
includes LOCTITE 3705, LOCTITE 3128, ECCOBOND E-3200, LOCTITE 3593,
LOCTITE 3943, and LOCTITE PC18M, for example. Preferably, the epoxy
has a dielectric constant that is similar to the dielectric
constant of the circuit board 10 in order to reduce
discontinuities, as described below. Further, the epoxy preferably
has a dielectric constant that is consistent throughout the
epoxy.
[0061] Accordingly, the portion of the coaxial cables 30 that is
removed to attach the coaxial cables 30 to the circuit board 10 is
surrounded by the epoxy, which has a dielectric constant similar to
the dielectric constant of the circuit board 10, rather than air.
Preferably, the dielectric constant of the epoxy is within about
.+-.20% of the dielectric constant of the circuit board 10, for
example. More preferably, the epoxy and the circuit board 10 each
have a dielectric constant between about 3.9 and about 4.2, for
example. However, the range of values for the dielectric constants
of the epoxy and the circuit board 10 is not limited thereto, and
may be selected, for example, according to the specific materials
for the components used in the two-connector assembly or according
to operating conditions or other factors or preferences. The
similarity in the dielectric constants of the epoxy and the circuit
board 10 reduces impedance discontinuities when signals are
transmitted between the circuit board 10 and the coaxial cables 30.
Reducing impedance discontinuities increases signal integrity
performance. As another example, the epoxy may be selected so that
the dielectric constant of the epoxy matches the dielectric
constant of the insulators 32 of the coaxial cable 30. Furthermore,
instead of using an epoxy, it is also possible to use bonding
agents, underfills, potting compounds, glues, fillers,
encapsulants, sealants, and other suitable materials, for
example.
[0062] As shown in FIGS. 8 and 10, the upper coaxial cable 30a and
the lower coaxial cable 30b are connected to the circuit board 10
in a "shingled" manner so that the upper coaxial cable 30a is
located over the contacts associated with the lower coaxial cable
30b. For example, shingling the upper and lower coaxial cables 30a
and 30b, according to a preferred embodiment of the present
invention, provides 24 wires (i.e., each of the conductors 31 of
the upper and lower coaxial cables 30a and 30b) in an area where a
typical transceiver would only include 12 wires.
[0063] The lower coaxial cable 30b is preferably soldered to the
circuit board 10, a first portion of epoxy is placed in the
termination region of the lower coaxial cable 30b, and the first
portion of epoxy is cured (e.g., by exposing the epoxy to a UV
light) to provide an epoxy-coated termination 35. Next, the upper
coaxial cable 30a is soldered to the circuit board 10, a second
portion of epoxy is placed in the termination region for the upper
coaxial cable 30a, and the second portion of epoxy is cured to
provide another epoxy-coated termination 35. Although the upper
coaxial cable 30a and the lower coaxial cable 30b could be soldered
and/or epoxied simultaneously to save manufacturing time,
sequentially soldering the upper coaxial cable 30a and the lower
coaxial cable 30b provides a better mechanical connection with a
reduced chance of introducing defects into the termination regions
because the coaxial cables 30 do not have to be bent as compared
with simultaneous soldering of the upper coaxial cable 30a and the
lower coaxial cable 30b. That is, if the coaxial cables are
simultaneously soldered, at least the upper coaxial cable 30a needs
to be bent away from the circuit board 10 during soldering of the
lower coaxial cable 30b, so that the outer coatings 34 of the upper
coaxial cable 30a are not damaged by the soldering of the lower
coaxial cable 30b. Bending of the coaxial cables 30 may result in
defects in the termination regions and may reduce performance of
the coaxial cables 30 due to mechanical fatigue.
[0064] A preferred embodiment of the present invention reduces the
length of the outer coatings 34 and insulators 32 of the coaxial
cables 30 that needs to be removed to attach the coaxial cables 30
to the circuit board 10. In particular, the high-density connection
for the coaxial cables 30 provided by the upper and lower
termination pads 11a and 13a, the ground planes 16, and the epoxy
allows for the length of the outer coatings 34 of the coaxial
cables 30 that needs to be stripped to be shorter than that of
cables used in known transceivers. In particular, the epoxy
provides a mechanical strain relief for the solder joints between
the upper and lower termination pads 11a and 13a and the conductors
31 of the coaxial cables 30, so as to allow for a shorter region of
the coaxial cables 30 to be soldered. Providing shorter termination
lengths improves high-speed performance by reducing the size of the
area where signal discontinuities are most likely to arise.
Preferably, the length of each of the exposed portions of the
insulators 32 and the length of each of the exposed portions of the
conductors 31 is less than about 0.050'', and is more preferably
less than about 0.030'', for example. Accordingly, since the
present preferred embodiment of the present invention provides a
shorter length of an unshielded portion of each of the conductors
31 of coaxial cables 30, impedance discontinuities are reduced in
the termination region. Reducing the impedance discontinuities
increases the signal integrity performance.
[0065] Each signal transmitted on one of the conductors 31 is
received at the circuit board 10 and routed through one of the
termination pads (i.e., upper termination pads 11a or lower
termination pads 13a). The upper coaxial cable 30a is preferably
terminated to the upper termination pads 11a, and the lower coaxial
cable 30b is preferably terminated to lower the termination pads
13a. Each signal is further routed through one of the traces (i.e.,
upper traces 11b or lower traces 13b) that are connected to the
corresponding upper termination pads 11a or lower termination pads
13a. Each signal is still further routed through one of the edge
pads (i.e., upper edge pads 11c or lower edge pads 13c) that are
located at the edge of the circuit board 10. Preferably, the upper
coaxial cable 30a and the lower coaxial cable 30b each include
pairs of conductors 31, for example, so that differential signals
can be transmitted on respective pairs of conductors 31. However,
according to a preferred embodiment of the present invention, the
conductors 31 carry single-ended signals, or a combination of both
differential signals and single-ended signals.
[0066] The signals of the upper coaxial cable 30a are preferably
routed through upper termination pads 11a, upper traces 11b, and
upper edge pads 11c on the top of the circuit board 10, as shown in
FIGS. 3, 8, and 9. Similarly, the signals of the lower coaxial
cable 30b are preferably routed through lower termination pads 13a
on the top of the circuit board 10 and lower traces 11b and lower
edge pads 11c on the bottom of the circuit board 10, as shown in
FIGS. 4, 6, and 7. Preferably, the lower traces 11b on the bottom
of the circuit board 10 are connected to lower termination pads 13a
on the top circuit board 10 by vias. As shown in FIGS. 16-20, the
upper edge pads 11c on the top of the circuit board 10 mate with
corresponding upper contacts 41 within the front connector 40 when
the circuit board 10 of the transceiver 100 is inserted into the
front connector 40. Similarly, the lower edge pads 13c on the
bottom of the circuit board 10 mate with corresponding lower
contacts 43 within the front connector 40 when the circuit board 10
of the transceiver 100 is inserted into the front connector 40.
[0067] As shown in FIGS. 3 and 4, the upper traces 11b on the top
of the circuit board 10 have shorter lengths than the lower traces
13b on the bottom of the circuit board 10. Accordingly, critical
signals can be routed through the upper coaxial cable 30a, the
upper termination pads 11a, the upper traces 11b, and the upper
edge pads 11c (i.e., only along the top of the circuit board 10) to
minimize the distance that the critical signals travel through
traces of the circuit board 10, so as to reduce crosstalk,
interference, noise, and the like. Accordingly, less critical
signals can be routed through the lower coaxial cable 30b, the
lower termination pads 13a, the lower traces 13b that are typically
longer the upper traces 11b, and the lower edge pads 13c (i.e.,
partially along the bottom of the circuit board 10).
[0068] However, the preferred embodiments of the present invention
are not limited to the specific arrangement described above.
According to preferred embodiments of the present invention,
balanced signal transmission lengths may be provided for the
signals of the upper coaxial cable 30a and the lower coaxial cable
30b. For example, if the upper contacts 41 are longer than the
lower contacts 43, then the signals of the upper coaxial cable 30a
and the lower coaxial cable 30b will have similar overall signal
transmission lengths through the circuit board 10 and the front
connector 40. As another example, the lower coaxial cable 30b may
be soldered to the bottom of the circuit board 10 to minimize the
distance that the signals of the lower coaxial cable 30b travel
through traces of the circuit board 10.
[0069] As shown in FIGS. 3 and 4, the circuit board 10 preferably
includes upper ground pads 12 arranged between each pair of upper
edge pads 11c and lower ground pads 14 arranged between each pair
of lower edge pads 13c, such that 19 total edge pads are defined on
each of the top and the bottom of the circuit board 10, for
example. According to a preferred embodiment of the present
invention, the pairs of upper and lower edge pads 11c and 13c with
ground pads 12 and 14 interposed between the pairs of the upper and
lower edge pads 11c and 13c provide high signal integrity while
still maintaining a 0.5-mm pitch for mating with a 0.5-mm-pitch
edge-card connector such as front connector 40, for example. The
back pads 15 preferably provide ground connections for the circuit
board 10, via back contacts 55 of the back connector 50. However,
according to a preferred embodiment of the present invention, the
back pads 15 may carry signals or power, or the back pads 15 may
have no electrical connection. Furthermore, the back pads 15 may
have any combination of the above, such that at least one of the
back pads carries signals or power while at least one of the back
pads has no electrical connection. According to a preferred
embodiment of the present invention, the circuit board 10 may not
include the back pads 15, for example, to reduce manufacturing
costs.
[0070] FIG. 11 is a bottom perspective view of the transceiver 100.
A preferred embodiment of the present invention includes undercuts
21 and alignment pins 29 in the housing 20 of the transceiver 100
to secure the housing 20 to the circuit board 10 as shown in FIG.
11. The undercuts 21 in the housing 20 receive the end of the
circuit board 10 that is opposite to the upper and lower edge pads
11c and 13c and help prevent the circuit board 10 from being
disconnected with the housing 20 when the transceiver 100 is
inserted into the front connector 40. The alignment pins 29 are
received by holes 19 of the circuit board 10 and provide a
low-cost, secure mechanical connection between the housing 20 and
the circuit board 10. The alignment pins 29 can be heat-staked
and/or ultrasonically welded after being inserted into the holes 19
of the circuit board 10. The preferred embodiments of the present
invention are not limited to the undercuts 21 and the alignment
pins 29 in the housing 20 as described above, as other features may
be used to secure the housing 20 to the circuit board 10.
[0071] FIGS. 12 and 13 are perspective views the U-clip 28. A
preferred embodiment of the present invention includes the U-clip
28, as shown in FIGS. 12 and 13, in the housing 20 of the
transceiver 100. The U-clip 28 includes legs 28a that are arranged
to be received by pass-through notches 18 in the circuit board 10,
as shown in FIGS. 3, 4, and 6-8. Preferably, the U-clip 28 includes
a tab 28c such that a force from, for example, a human finger, can
push or pull the legs 28a of the U-clip 28 into or from the
pass-through notches 18 in the circuit board 10. When the U-clip 28
is engaged, the legs 28a of the U-clip 28 engage with slots 58 in
the back connector 50 to secure the transceiver 100 to the back
connector 50, as shown in FIGS. 1, 2, 21, and 22 and further
described in detail below.
[0072] FIG. 14 shows a top perspective view of the substrate 60.
FIG. 15 shows a top perspective view of a back connector 50, and
FIG. 16 shows a top perspective view of the front connector 40.
[0073] As shown in FIG. 14, the substrate 60 includes three rows of
pads: a row of upper substrate pads 61, a row of lower substrate
pads 63, and a row of back substrate pads 65. Further, the
substrate 60 preferably includes front alignment holes 68 and back
alignment holes 69.
[0074] As shown in FIG. 15, the back connector 50 includes back
contacts 55 and slots 58. Further, the back connector 50 preferably
includes alignment posts 59. Preferably, the alignment posts are
arranged to be inserted into the back alignment holes 68 of the
substrate 60 to locate the back connector 50 on the substrate 60.
Furthermore, the back alignment holes 68 and the alignment posts 59
may be polarized to ensure proper alignment and orientation of the
back connector 50 on the substrate 60. The back substrate pads 65
are preferably fusibly connected (for example, by solder) to the
back contacts 55 to provide a secure electrical and mechanical
connection between the back connector 50 and the substrate 60.
[0075] As shown in FIG. 16, the front connector 40 includes upper
contacts 41 and lower contacts 43. It is noted that, for clarity,
not all of the upper contacts 41 and lower contacts 43 are shown in
FIG. 16. Further, the front connector 40 preferably includes
spacers 49. The spacers 49 may be arranged to be inserted into the
front alignment holes 69 of the substrate 60 to locate the front
connector 40 on the substrate 60. The front alignment holes 69 and
the spacers 49 may be polarized to ensure proper alignment and
orientation of the front connector 40 on the substrate 60. The
upper substrate pads 61 and the lower substrate pads 63 are
preferably fusibly connected (for example, by solder),
respectively, to the upper contacts 41 and the lower contacts 43 to
provide a secure electrical and mechanical connection between the
front connector 40 and the substrate 60.
[0076] FIGS. 17-20 show views of the front connector 40 and the
back connector 50 mounted on the substrate 60, prior to engagement
with the transceiver 100.
[0077] As shown in FIGS. 17-20, the front connector 40, the back
connector 50, and the transceiver 100 are arranged so that the
upper edge pads 11c of the circuit board 10 align and engage with
the upper contacts 41 of the front connector 40 when the
transceiver 100 is inserted into the front connector 40. Similarly,
the front connector 40, the back connector 50, and the transceiver
100 are arranged so that the lower edge pads 13c of the circuit
board 10 align and engage with the lower contacts 43 of the front
connector 40 when the transceiver 100 is inserted into the front
connector 40. Further, the front connector 40, the back connector
50, and the transceiver 100 are preferably arranged so that the
back pads 15 of the circuit board 10 align and engage with the back
contacts 55 of the back connector 50 when the transceiver 100 is
inserted into the back connector 50. However, this alignment is not
needed if the back pads 15 are not included on the circuit board
10.
[0078] FIGS. 21 and 22 show top perspective views of the
two-connector assembly when the transceiver 100 is engaged with the
front connector 40 and the back connector 50, and the U-clip 28 is
engaged with the circuit board 10 and the back connector 50. The
back connector 50 is not shown in FIG. 22 to illustrate the
insertion of the U-clip 28 with the circuit board 10.
[0079] As shown in FIG. 21, the legs 28c of the U-clip 28 are
insertable into the slots 58 of the back connector 50 to secure the
transceiver 100 to the back connector 50 and the front connector
40. As shown in FIG. 22, the legs 28c of the U-clip 28 are also
insertable into the pass-through notches 18 of the circuit board 10
to help prevent the circuit board 10 from being disconnected from
the housing 20, the front connector 40, and the back connector
50.
[0080] When the legs 28c of the U-clip 28 are engaged with the
slots 58 of the back connector 50 and the pass-through notches 18
of the circuit board 10, movement of the circuit board 10 (e.g.,
twisting of the circuit board 10 within the front connector 40) is
restricted. Accordingly, secure electrical connections between the
edge pads 11c and 13c of the circuit board 10 and the contacts 41
and 43 of the front connector 40 may be achieved, even when using a
small pitch such as a 0.5-mm pitch, for example. Furthermore, by
restricting movement of the circuit board 10, degradation and wear
of the edge pads 11c and 13c of the circuit board 10 and the
contacts 41 and 43 of the front connector 40 is significantly
reduced or prevented.
[0081] The housing 20 preferably includes ridges or depressions
that press against the arm 28b of the U-clip 28 to help prevent
undesirable disengagement of the legs 28a from the slots 58.
[0082] FIGS. 23A-23C show the top of the circuit board 10. A
preferred embodiment of the present invention preferably uses a
two-step manufacturing process of the circuit board 10 to improve
the overall width tolerance of the circuit board 10 from +/-0.005''
to +/-0.001'', for example. The first step is computer numerical
control (CNC) routing the majority of the perimeter of the circuit
board 10', as shown in FIG. 23A. The second step is laser routing
the width region of the circuit board to provide the 0.5-mm pitch
for the circuit board 10, as shown in FIG. 23B. As shown in FIG.
23C, the material 10a removed by the laser routing provides a
precision fit for the circuit board 10 into the front connector 40.
The laser routing provides a +/-0.001'' tolerance, and is limited
to a small region of the circuit board 10 because laser routing is
more expensive than CNC routing. Further, laser routing is
preferably applied to only the end of the circuit board 10 that
includes the upper and lower edge pads 11c and 13c, since a tight
tolerance is only needed for the portion of the circuit board 10
that engages with a 0.5-mm pitch edge-card connector such as front
connector 40. A reliable electrical connection may be achieved
between the circuit board 10 and the back connector 50 using only
CNC routing, since the back connector 50 preferably has a tolerance
of about +/-0.005'', for example.
[0083] A preferred embodiment of the present invention preferably
includes both the front connector 40 and the back connector 50, as
shown in FIGS. 1, 2, 17-19, 21, and 22. However, only the front
edge connector 40 may be used to transmit signals. That is, the
back connector 50 may function only to help mechanically secure the
circuit board 10 to a substrate 60 on which the front connector 40
and the back connector 50 are mounted. Furthermore, signals may
also be routed along only one of the top and bottom of the circuit
board 10. For example, the signals of the upper coaxial cable 30a
can be routed along the top of the circuit board 10, and the
signals of the lower coaxial cable 30b can be routed through the
back connector 50 instead of being routed through the lower traces
13b on the bottom of the circuit board 10.
[0084] The front connector 40 and the back connector 50, according
to a preferred embodiment of the present invention, may connect
with an optical transceiver. Preferably, the optical transceiver
includes the circuit board shown in FIGS. 3 and 4. Preferably, the
optical transceiver also includes an optical engine arranged to
convert optical signals into electrical signals and to convert
electrical signals into optical signals. The optical transceiver
preferably further includes a heatsink.
[0085] The back connector 50 is preferably a compression-type
connector and may be implemented as a zero-insertion-force
connector, as shown in FIG. 15. However, other one-piece interface
or connector solutions could also be used for the back connector
50.
[0086] Instead of using the circuit board 10 and the substrate 60,
it is also possible to use any suitable element on which electrical
components can be attached. Furthermore, the circuit board 10 and
the substrate 60 may be arranged to include stepped planes. For
example, the substrate 60 could include stacked substrates so that
the back substrate pads 65 are included in a different plane from
the upper and lower substrate pads 61 and 63.
[0087] A preferred embodiment of the present invention preferably
uses epoxy in the termination region of the circuit board 10 to
improve both the electrical and mechanical connections between the
coaxial cables 30 and the circuit board 10. However, the epoxy
coated terminations 35 may only be included in the termination
region of only one of the coaxial cables 30 and/or in only a
portion of the termination region. Furthermore, bonding agents,
encapsulants, adhesives, and other suitable or similar materials
may be used in place of the epoxy.
[0088] It should be understood that the foregoing description is
only illustrative of the present invention. Various alternatives
and modifications can be devised by those skilled in the art
without departing from the present invention. Accordingly, the
present invention is intended to embrace all such alternatives,
modifications, and variances that fall within the scope of the
appended claims.
* * * * *