U.S. patent application number 15/235143 was filed with the patent office on 2016-12-01 for shielded electrical cable.
This patent application is currently assigned to 3M Innovative Properties Company. The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Douglas B. Gundel.
Application Number | 20160351302 15/235143 |
Document ID | / |
Family ID | 43063806 |
Filed Date | 2016-12-01 |
United States Patent
Application |
20160351302 |
Kind Code |
A1 |
Gundel; Douglas B. |
December 1, 2016 |
SHIELDED ELECTRICAL CABLE
Abstract
A shielded electrical cable includes a conductor set that
includes one or more substantially parallel longitudinal insulated
conductors, a shielding film and two non-conductive polymeric
layers disposed around the conductor set, The polymeric layers
include concentric portions substantially concentric with at least
one of the conductors having a first cross-sectional area and
parallel portions where the polymeric layers are substantially
parallel to each other. The cable further includes a transition
portion providing a gradual transition between the concentric
portions and the parallel portions of the polymeric layers, the
transition portion having a second cross-sectional area defined as
an area between the shielding film and the polymeric layers between
first transition points where the polymeric layers deviate from
being substantially concentric with the at least one of the
conductors and second transition points where the polymeric layers
deviate from being substantially parallel. The second
cross-sectional area is equal to or smaller than the first
cross-sectional area.
Inventors: |
Gundel; Douglas B.; (Cedar
Park, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
43063806 |
Appl. No.: |
15/235143 |
Filed: |
August 12, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01B 11/04 20130101;
H01B 11/10 20130101; H01B 11/1895 20130101; H01B 7/0876 20130101;
H01B 11/203 20130101; H01B 7/0823 20130101; H01B 11/1091 20130101;
H05K 9/0098 20130101; H01B 7/0861 20130101; H01B 11/00 20130101;
H01B 7/0838 20130101; H01B 11/1891 20130101; H01B 7/0892 20130101;
H01B 7/188 20130101 |
International
Class: |
H01B 11/20 20060101
H01B011/20; H01B 11/18 20060101 H01B011/18; H01B 7/08 20060101
H01B007/08 |
Claims
1. A shielded electrical cable comprising: a conductor set
including one or more substantially parallel longitudinal insulated
conductors; a shielding film disposed around the conductor set; and
two non-conductive polymeric layers disposed around the conductor
set and including a concentric portion substantially concentric
with at least one of the conductors having a first cross-sectional
area and a parallel portion on at least one lateral side of the
conductor set where the two non-conductive polymeric layers are
substantially parallel to each other; and a transition portion
providing a gradual transition between the concentric portion and
the parallel portion of the two non-conductive polymeric layers,
the transition portion comprising a second cross-sectional area
defined as an area between the shielding film and the two
non-conductive polymeric layers between first transition points
where the two non-conductive polymeric layers deviate from being
substantially concentric with the at least one of the conductors
and second transition points where the two non-conductive polymeric
layers deviate from being substantially parallel, the second
cross-sectional area being equal to or smaller than the first
cross-sectional area.
2. The shielded electrical cable of claim 1, wherein the second
cross-sectional area is smaller than the first cross-sectional
area.
3. The shielded electrical cable of claim 1, wherein the second
cross-sectional area is substantially the same along the length of
the conductor.
4. The shielded electrical cable of claim 1, wherein the shielded
electrical cable includes transition portions positioned on each
side of the conductor set.
5. The shielded electrical cable of claim 1 further comprising an
adhesive layer disposed between the two non-conductive polymeric
layers and bonding the two non-conductive polymeric layers to each
other on at least one side of the conductor set.
6. The shielded electrical cable of claim 1, wherein the insulated
conductor has an insulation thickness, and wherein the transition
portion has a lateral length defined as a length between the first
transition points, wherein the lateral length is less than the
insulation thickness.
7. The shielded electrical cable of claim 1, wherein the transition
portion has a lateral length defined as a length between the first
transition points, wherein the lateral length is less than a
diameter of the conductor.
8. The shielded electrical cable of claim 1 comprising a
characteristic impedance that is within 5 to 10% of a target
impedance value over a length of 1 meter.
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to shielded
electrical cables for the transmission of electrical signals. In
particular, the present invention relates to shielded electrical
cables that can be mass-terminated and provide high speed
electrical properties.
BACKGROUND
[0002] Electrical cables for transmission of electrical signals are
well known. One common type of electrical cable is a coaxial cable.
Coaxial cables generally include an electrically conductive wire
surrounded by an insulator. The wire and insulator are surrounded
by a shield, and the wire, insulator, and shield are surrounded by
a jacket. Another common type of electrical cable is a shielded
electrical cable comprising one or more insulated signal conductors
surrounded by a shielding layer formed, for example, by a metal
foil. To facilitate electrical connection of the shielding layer, a
further un-insulated conductor is sometimes provided between the
shielding layer and the insulation of the signal conductor or
conductors. Both these common types of electrical cable normally
require the use of specifically designed connectors for termination
and are often not suitable for the use of mass-termination
techniques, i.e., the simultaneous connection of a plurality of
conductors to individual contact elements, such as, e.g.,
electrical contacts of an electrical connector or contact elements
on a printed circuit board. Although electrical cables have been
developed to facilitate these mass-termination techniques, these
cables often have limitations in the ability to mass-produce them,
in the ability to prepare their termination ends, in their
flexibility, and in their electrical performance. In view of the
advancements in high speed electrical and electronic components, a
continuing need exists for electrical cables that are capable of
transmitting high speed signals, facilitate mass-termination
techniques, are cost-effective, and can be used in a large number
of applications.
SUMMARY
[0003] In one aspect, the present invention provides a shielded
electrical cable including a conductor set and a shielding film.
The conductor set includes one or more substantially parallel
longitudinal insulated conductors. The shielding film includes a
cover portion partially covering the conductor set, and parallel
portions extending from both sides of the conductor set.
[0004] In another aspect, the present invention provides a shielded
electrical cable including a plurality of spaced apart conductor
sets arranged generally in a single plane and a shielding film.
Each conductor set includes one or more substantially parallel
longitudinal insulated conductors. The shielding film includes a
plurality of cover portions partially covering the conductor sets,
and a parallel portion disposed between adjacent conductor sets and
configured to electrically isolate the adjacent conductor sets from
each other.
[0005] The above summary of the present invention is not intended
to describe each disclosed embodiment or every implementation of
the present invention. The Figures and detailed description that
follow below more particularly exemplify illustrative
embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a perspective view of an exemplary embodiment of a
shielded electrical cable according to an aspect of the present
invention.
[0007] FIGS. 2a-2e are front cross-sectional views of five other
exemplary embodiments of a shielded electrical cable according to
aspects of the present invention.
[0008] FIG. 3 is a perspective view of two shielded electrical
cables of FIG. 1 terminated to a printed circuit board.
[0009] FIGS. 4a-4d are top views of an exemplary termination
process of a shielded electrical cable according to an aspect of
the present invention.
[0010] FIG. 5 is a top view of another exemplary embodiment of a
shielded electrical cable according to an aspect of the present
invention.
[0011] FIG. 6 is a top view of another exemplary embodiment of a
shielded electrical cable according to an aspect of the present
invention.
[0012] FIGS. 7a-7d are front cross-sectional views of four other
exemplary embodiments of a shielded electrical cable according to
aspects of the present invention.
[0013] FIGS. 8a-8c are front cross-sectional views of three other
exemplary embodiments of a shielded electrical cable according to
aspects of the present invention.
[0014] FIGS. 9a-9b are top and partially cross-sectional front
views, respectively, of an exemplary embodiment of an electrical
assembly according to an aspect of the present invention terminated
to a printed circuit board.
[0015] FIGS. 10a-10e and 10f-10g are perspective and front
cross-sectional views, respectively, illustrating an exemplary
method of making a shielded electrical cable according to an aspect
of the present invention.
[0016] FIGS. 11a-11c are front cross-sectional views illustrating a
detail of an exemplary method of making a shielded electrical cable
according to an aspect of the present invention.
[0017] FIGS. 12a-12b are a front cross-sectional view of another
exemplary embodiment of a shielded electrical cable according to an
aspect of the present invention and a corresponding detail view,
respectively.
[0018] FIGS. 13a-13b are front cross-sectional views of two other
exemplary embodiments of a shielded electrical cable according to
an aspect of the present invention.
[0019] FIGS. 14a-14b are front cross-sectional views of two other
exemplary embodiments of a shielded electrical cable according to
an aspect of the present invention.
[0020] FIGS. 15a-15c are front cross-sectional views of three other
exemplary embodiments of a shielded electrical cable according to
aspects of the present invention.
[0021] FIGS. 16a-16g are front cross-sectional detail views
illustrating seven exemplary embodiments of a parallel portion of a
shielded electrical cable according to aspects of the present
invention.
[0022] FIGS. 17a-17b are front cross-sectional detail views of
another exemplary embodiment of a parallel portion of a shielded
electrical cable according to an aspect of the present
invention.
[0023] FIG. 18 is a front cross-sectional detail view of another
exemplary embodiment of a shielded electrical cable according to an
aspect of the present invention in a bent configuration.
[0024] FIG. 19 is a front cross-sectional detail view of another
exemplary embodiment of a shielded electrical cable according to an
aspect of the present invention.
[0025] FIGS. 20a-20f are front cross-sectional detail views
illustrating six other exemplary embodiments of a parallel portion
of a shielded electrical cable according to aspects of the present
invention.
[0026] FIG. 21a-21b are front cross-sectional views of two other
exemplary embodiments of a shielded electrical cable according to
aspects of the present invention.
[0027] FIG. 22 is a graph comparing the electrical isolation
performance of an exemplary embodiment of a shielded electrical
cable according to an aspect of the present invention to the
electrical isolation performance of a conventional electrical
cable.
[0028] FIG. 23 is a front cross-sectional view of another exemplary
embodiment of a shielded electrical cable according to an aspect of
the present invention.
[0029] FIG. 24 is a front cross-sectional view of another exemplary
embodiment of a shielded electrical cable according to an aspect of
the present invention.
[0030] FIG. 25 is a front cross-sectional view of another exemplary
embodiment of a shielded electrical cable according to an aspect of
the present invention.
[0031] FIG. 26a-26d are front cross-sectional views of four other
exemplary embodiments of a shielded electrical cable according to
aspects of the present invention.
[0032] FIG. 27 is a front cross-sectional view of another exemplary
embodiment of a shielded electrical cable according to an aspect of
the present invention.
[0033] FIG. 28a-28d are front cross-sectional views of four other
exemplary embodiments of a shielded electrical cable according to
aspects of the present invention.
[0034] FIG. 29a-29d are front cross-sectional views of four other
exemplary embodiments of a shielded electrical cable according to
aspects of the present invention.
DETAILED DESCRIPTION
[0035] In the following detailed description of the preferred
embodiments, reference is made to the accompanying drawings that
form a part hereof. The accompanying drawings show, by way of
illustration, specific embodiments in which the invention may be
practiced. It is to be understood that other embodiments may be
utilized, and structural or logical changes may be made without
departing from the scope of the present invention. The following
detailed description, therefore, is not to be taken in a limiting
sense, and the scope of the invention is defined by the appended
claims.
[0036] Referring now to the Figures, FIG. 1 illustrates an
exemplary embodiment of a shielded electrical cable according to an
aspect of the present invention. Shielded electrical cable 2
includes a plurality of spaced apart conductor sets 4 arranged
generally in a single plane. Each conductor set includes two
substantially parallel longitudinal insulated conductors 6.
Insulated conductors 6 may include insulated signal wires,
insulated power wires, or insulated ground wires. Two generally
parallel shielding films 8 are disposed around conductor sets 4. A
conformable adhesive layer 10 is disposed between shielding films 8
and bonds shielding films 8 to each other on both sides of each
conductor set 4. In one embodiment, conductor sets 4 have a
substantially curvilinear cross-sectional shape, and shielding
films 8 are disposed around conductor sets 4 such as to
substantially conform to and maintain the cross-sectional shape.
Maintaining the cross-sectional shape maintains the electrical
characteristics of conductor sets 4 as intended in the design of
conductor sets 4. This is an advantage over some conventional
shielded electrical cables where disposing a conductive shield
around a conductor set changes the cross-sectional shape of the
conductor set.
[0037] Although in the embodiment illustrated in FIG. 1, each
conductor set 4 includes two insulated conductors 6, in other
embodiments, each conductor set 4 may include one or more insulated
conductors 6. For example, instead of shielded electrical cable 2
including four conductor sets 4 each including two insulated
conductors 6 as shown in FIG. 1, shielded electrical cable 2 may
include one conductor set 4 including eight insulated conductors 6,
or eight conductor sets 4 each including one insulated conductor 6.
This flexibility in arrangements of conductor sets 4 and insulated
conductors 6 allows shielded electrical cable 2 to be configured
suitable for the intended application. For example, conductor sets
4 and insulated conductors 6 may be configured to form a multiple
twinaxial cable, i.e., multiple conductor sets 4 each including two
insulated conductors 6, a multiple coaxial cable, i.e., multiple
conductor sets each including one insulated conductor 6, or a
combination thereof. In other embodiments, a conductor set 4 may
further include a conductive shield (not shown) disposed around the
one or more insulated conductors 6, and an insulative jacket (not
shown) disposed around the conductive shield.
[0038] In the embodiment illustrated in FIG. 1, shielded electrical
cable 2 further includes optional longitudinal ground conductors
12. Ground conductors 12 may include ground wires or drain wires.
Ground conductors 12 are spaced apart from and extend in
substantially the same direction as insulated conductors 6.
Conductor sets 4 and ground conductors 12 are arranged generally in
a single plane. Shielding films 8 are disposed around ground
conductors 12 and conformable adhesive layer 10 bonds shielding
films 8 to each other on both sides of ground conductors 12. Ground
conductors 12 may electrically contact at least one of shielding
films 8.
[0039] FIGS. 2a-2e illustrate various exemplary embodiments of a
shielded electrical cable according to aspects of the present
invention. FIGS. 2a-2e are specifically intended to illustrate
various examples of arrangements of conductors disposed between two
shielding films.
[0040] Referring to FIG. 2a, shielded electrical cable 102 includes
a single conductor set 104. Conductor set 104 includes a single
longitudinal insulated conductor 106. Two generally parallel
shielding films 108 are disposed around conductor set 104. A
conformable adhesive layer 110 is disposed between shielding films
108 and bonds shielding films 108 to each other on both sides of
conductor set 104. Shielded electrical cable 102 further includes
optional longitudinal ground conductors 112. Ground conductors 112
are spaced apart from and extend in substantially the same
direction as insulated conductor 106. Conductor set 104 and ground
conductors 112 are arranged generally in a single plane. Shielding
films 108 are disposed around ground conductors 112 and conformable
adhesive layer 110 bonds shielding films 108 to each other on both
sides of ground conductors 112. Ground conductors 112 may
electrically contact at least one of shielding films 108. Insulated
conductor 106 is effectively arranged in a coaxial or single ended
cable arrangement.
[0041] Referring to FIG. 2b, shielded electrical cable 202 is
similar to shielded electrical cable 102 illustrated in FIG. 2a.
Where shielded electrical cable 102 includes a single conductor set
104 including a single longitudinal insulated conductor 106,
shielded electrical cable 202 includes a single conductor set 204
including two substantially parallel longitudinal insulated
conductors 206. Insulated conductors 206 are arranged generally in
a single plane and effectively in a twinaxial or differential pair
cable arrangement.
[0042] Referring to FIG. 2c, shielded electrical cable 302 is
similar to shielded electrical cable 102 illustrated in FIG. 2a.
Where shielded electrical cable 102 includes a single conductor set
104 including a single longitudinal insulated conductor 106,
shielded electrical cable 302 includes a single conductor set 304
including two longitudinal insulated conductors 306. Insulated
conductors 306 are arranged effectively in a twisted pair cable
arrangement, whereby insulated conductors 306 twist around each
other in longitudinal direction.
[0043] Referring to FIG. 2d, shielded electrical cable 402 is
similar to shielded electrical cable 102 illustrated in FIG. 2a.
Where shielded electrical cable 102 includes a single conductor set
104 including a single longitudinal insulated conductor 106,
shielded electrical cable 402 includes a single conductor set 404
including four longitudinal insulated conductors 406. Insulated
conductors 406 are arranged effectively in a quad cable
arrangement, whereby insulated conductors 406 may twist around each
other in longitudinal direction, or may be substantially
parallel.
[0044] Referring back to FIGS. 2a-2d, further embodiments of
shielded electrical cables according to aspects of the present
invention may include a plurality of spaced apart conductor sets
104, 204, 304 or 404, or combinations thereof, arranged generally
in a single plane. Optionally, the shielded electrical cables may
include a plurality of ground conductors 112 spaced apart from and
extending generally in the same direction as the insulated
conductors of the conductor sets, wherein the conductor sets and
ground conductors are arranged generally in a single plane. FIG. 2e
illustrates an exemplary embodiment of such a shielded electrical
cable.
[0045] Referring to FIG. 2e, shielded electrical cable 502 includes
a plurality of spaced apart conductor sets 104, 204 arranged
generally in a single plane. Shielded electrical cable 502 further
includes optional ground conductors 112 disposed between conductor
sets 104, 204 and at both ends of shielded electrical cable 502.
Two generally parallel shielding films 508 are disposed around
conductor sets 104, 204 and ground conductors 112. A conformable
adhesive layer 510 is disposed between shielding films 508 and
bonds shielding films 508 to each other on both sides of each
conductor set 104, 204 and each ground conductor. Shielded
electrical cable 502 includes a combination of coaxial cable
arrangements (conductor sets 104) and a twinaxial cable arrangement
(conductor set 204) and may therefore be referred to as a hybrid
cable arrangement.
[0046] FIG. 3 illustrates two shielded electrical cables 2
terminated to a printed circuit board 14. Because insulated
conductors 6 and ground conductors 12 are arranged generally in a
single plane, shielded electrical cables 2 are well suited for
mass-stripping, i.e., the simultaneous stripping of shielding films
8 and insulated conductors 6, and mass-termination, i.e., the
simultaneous terminating of the stripped ends of insulated
conductors 6 and ground conductors 12, which allows a more
automated cable assembly process. This is an advantage of the
shielded electrical cables according to aspects of the present
invention. In FIG. 3, the stripped ends of insulated conductors 6
and ground conductors 12 are terminated to contact elements 16 on
printed circuit board 14. In other embodiments, the stripped ends
of insulated conductors 6 and ground conductors 12 may be
terminated to any suitable individual contact elements of any
suitable termination point, such as, e.g., electrical contacts of
an electrical connector.
[0047] FIGS. 4a-4d illustrate an exemplary termination process of
shielded electrical cable 2 to printed circuit board 14. This
termination process can be a mass-termination process and includes
the steps of stripping (illustrated in FIGS. 4a-4b), aligning
(illustrated in FIG. 4c), and terminating (illustrated in FIG. 4d).
When forming shielded electrical cable 2, the arrangement of
conductor sets 4, insulated conductors 6, and ground conductors 12
of shielded electrical cable 2 may be matched to the arrangement of
contact elements 16 on printed circuit board 14, which would
eliminate any significant manipulation of the end portions of
shielded electrical cable 2 during alignment or termination.
[0048] In the step illustrated in FIG. 4a, an end portion 8a of
shielding films 8 is removed. Any suitable method may be used, such
as, e.g., mechanical stripping or laser stripping. This step
exposes an end portion of insulated conductors 6 and ground
conductors 12. In one aspect, mass-stripping of end portion 8a of
shielding films 8 is possible because they form an integrally
connected layer that is separate from the insulation of insulated
conductors 6. Removing shielding films 8 from insulated conductors
6 allows protection against electrical shorting at these locations
and also provides independent movement of the exposed end portions
of insulated conductors 6 and ground conductors 12. In the step
illustrated in FIG. 4b, an end portion 6a of the insulation of
insulated conductors 6 is removed. Any suitable method may be used,
such as, e.g., mechanical stripping or laser stripping. This step
exposes an end portion of the conductor of insulated conductors 6.
In the step illustrated in FIG. 4c, shielded electrical cable 2 is
aligned with printed circuit board 14 such that the end portions of
the conductors of insulated conductors 6 and the end portions of
ground conductors 12 of shielded electrical cable 2 are aligned
with contact elements 16 on printed circuit board 14. In the step
illustrated in FIG. 4d, the end portions of the conductors of
insulated conductors 6 and the end portions of ground conductors 12
of shielded electrical cable 2 are terminated to contact elements
16 on printed circuit board 14. Examples of suitable termination
methods that may be used include soldering, welding, crimping,
mechanical clamping, and adhesively bonding, to name a few.
[0049] FIG. 5 illustrates another exemplary embodiment of a
shielded electrical cable according to an aspect of the present
invention. Shielded electrical cable 602 is similar to shielded
electrical cable 2 illustrated in FIG. 1. In addition, shielded
electrical cable 602 includes a plurality of longitudinal splits 18
disposed between conductor sets 4. Splits 18 separate individual
conductor sets 4 at least along a portion of the length of shielded
electrical cable 602, thereby increasing at least the lateral
flexibility of shielded electrical cable 602. This allows shielded
electrical cable 602 to be placed more easily into a curvilinear
outer jacket, e.g. In other embodiments, splits 18 may be placed
such as to separate individual or multiple conductor sets 4 and
ground conductors 12. To maintain the spacing of conductor sets 4
and ground conductors 12, splits 18 may be discontinuous along the
length of shielded electrical cable 602. To maintain the spacing of
conductor sets 4 and ground conductors 12 in at least one end
portion A of shielded electrical cable 602 and thereby maintaining
mass-termination capability, splits 18 may not extend into one or
both end portions A. Splits 18 may be formed in shielded electrical
cable 602 using any suitable method, such as, e.g., laser cutting
or punching. Instead of or in combination with longitudinal splits,
other suitable shapes of openings may be formed in shielded
electrical cable 602, such as, e.g., holes, e.g., to increase at
least the lateral flexibility of shielded electrical cable 602.
[0050] FIG. 6 illustrates another exemplary embodiment of a
shielded electrical cable according to an aspect of the present
invention. Shielded electrical cable 702 is similar to shielded
electrical cable 602 illustrated in FIG. 5. Effectively, in
shielded electrical cable 702, one of conductor sets 4 is replaced
by two ground conductors 12. Shielded electrical cable 702 includes
longitudinal splits 18 and 18'. Split 18 separates individual
conductor sets 4 along a portion of the length of shielded
electrical cable 702 and does not extend into end portions A of
shielded electrical cable 702. Split 18' separates individual
conductor sets 4 along the length of shielded electrical cable 702
and extends into end portions A of shielded electrical cable 702,
which effectively splits shielded electrical cable 702 into two
individual shielded electrical cables 702', 702''. Shielding films
8 and ground conductors 12 provide an uninterrupted ground plane in
each of the individual shielded electrical cables 702', 702''. This
exemplary embodiment illustrates the advantage of the parallel
processing capability of the shielded electrical cables according
to aspects of the present invention, whereby multiple shielded
electrical cables may be formed simultaneously.
[0051] FIGS. 7a-7d illustrate four other exemplary embodiments of a
shielded electrical cable according to aspects of the present
invention. FIGS. 7a-7e are specifically intended to illustrate
various examples of constructions of the shielding films of the
shielded electrical cables. In one aspect, at least one of the
shielding films may include a conductive layer and a non-conductive
polymeric layer. The conductive layer may include any suitable
conductive material, including but not limited to copper, silver,
aluminum, gold, and alloys thereof. The non-conductive polymeric
layer may include any suitable polymeric material, including but
not limited to polyester, polyimide, polyamide-imide,
polytetrafluoroethylene, polypropylene, polyethylene, polyphenylene
sulfide, polyethylene naphthalate, polycarbonate, silicone rubber,
ethylene propylene diene rubber, polyurethane, acrylates,
silicones, natural rubber, epoxies, and synthetic rubber adhesive.
The non-conductive polymeric layer may include one or more
additives and/or fillers to provide properties suitable for the
intended application. In another aspect, at least one of the
shielding films may include a laminating adhesive layer disposed
between the conductive layer and the non-conductive polymeric
layer. In another aspect, at least one of the shielding films may
include a stand-alone conductive film. The construction of the
shielding films may be selected based on a number of design
parameters suitable for the intended application, such as, e.g.,
flexibility, electrical performance, and configuration of the
shielded electrical cable (such as, e.g., presence and location of
ground conductors). In one embodiment, the shielding films include
an integrally formed shielding film. In one embodiment, the
shielding films have a thickness in the range of 0.01 mm to 0.05
mm. The shielding films provide isolation, shielding, and precise
spacing between the conductor sets, and enable a more automated and
lower cost cable manufacturing process.
[0052] In addition, the shielding films prevent a phenomenon known
as "signal suck-out" or resonance, whereby high signal attenuation
occurs at a particular frequency range. This phenomenon typically
occurs in conventional shielded electrical cables where a
conductive shield is wrapped around a conductor set.
[0053] Referring to FIG. 7a, shielded electrical cable 802 includes
a single conductor set 804. Conductor set 804 includes two
substantially parallel longitudinal insulated conductors 806. Two
generally parallel shielding films 808 are disposed around
conductor set 804. Shielding films 808 include a conformable
adhesive layer 810 that bonds shielding films 808 to each other on
both sides of conductor set 804. Insulated conductors 806 are
arranged generally in a single plane and effectively in a twinaxial
or differential pair cable arrangement. Shielding films 808 include
a conductive layer 808a and a non-conductive polymeric layer 808b.
Non-conductive polymeric layer 808b faces insulated conductors 806.
Conductive layer 808a may be deposited onto non-conductive
polymeric layer 808b using any suitable method.
[0054] Referring to FIG. 7b, shielded electrical cable 902 includes
a single conductor set 904. Conductor set 904 includes two
substantially parallel longitudinal insulated conductors 906. Two
generally parallel shielding films 908 are disposed around
conductor set 904. Shielding films 908 include a conformable
adhesive layer 910 that bonds shielding films 908 to each other on
both sides of conductor set 904. Insulated conductors 906 are
arranged generally in a single plane and effectively in a twinaxial
or differential pair cable arrangement. Shielding films 908 include
a conductive layer 908a and a non-conductive polymeric layer 908b.
Conductive layer 908a faces insulated conductors 906. Conductive
layer 908a may be deposited onto non-conductive polymeric layer
908b using any suitable method.
[0055] Referring to FIG. 7c, shielded electrical cable 1002
includes a single conductor set 1004. Conductor set 1004 includes
two substantially parallel longitudinal insulated conductors 1006.
Two generally parallel shielding films 1008 are disposed around
conductor set 1004. Shielding films 1008 include a conformable
adhesive layer 1010 that bonds shielding films 1008 to each other
on both sides of conductor set 1004. Insulated conductors 1006 are
arranged generally in a single plane and effectively in a twinaxial
or differential pair cable arrangement. Shielding films 1008
include a stand-alone conductive film.
[0056] Referring to FIG. 7d, shielded electrical cable 1102
includes a single conductor set 1104. Conductor set 1104 includes
two substantially parallel longitudinal insulated conductors 1106.
Two generally parallel shielding films 1108 are disposed around
conductor set 1104. Shielding films 1108 include a conformable
adhesive layer 1110 that bonds shielding films 1108 to each other
on both sides of conductor set 1104. Insulated conductors 1106 are
arranged generally in a single plane and effectively in a twinaxial
or differential pair cable arrangement. Shielding films 1108
include a conductive layer 1108a, a non-conductive polymeric layer
1108b, and a laminating adhesive layer 1108c disposed between
conductive layer 1108a and non-conductive polymeric layer 1108b,
thereby laminating conductive layer 1108a to non-conductive
polymeric layer 1108b. Conductive layer 1108a faces insulated
conductors 1106.
[0057] Referring back to FIG. 1, conformable adhesive layer 10 of
shielded electrical cable 2 is disposed between shielding films 8
and bonds shielding films 8 to each other on both sides of each
conductor set 4. In one embodiment, conformable adhesive layer 10
may be disposed on one of shielding films 8. In another embodiment,
conformable adhesive layer 10 may be disposed on both shielding
films 8. Conformable adhesive layer 10 may include an insulative
adhesive and provide an insulative bond between shielding films 8.
Optionally, conformable adhesive layer 10 may provide an insulative
bond between at least one of shielding films 8 and insulated
conductors 6, and between at least one of shielding films 8 and
ground conductors 12. Conformable adhesive layer 10 may include a
conductive adhesive and provide a conductive bond between shielding
films 8. Optionally, conformable adhesive layer 10 may provide a
conductive bond between at least one of shielding films 8 and
ground conductors 12. Suitable conductive adhesives include
conductive particles to provide the flow of electrical current. The
conductive particles can be any of the types of particles currently
used, such as spheres, flakes, rods, cubes, amorphous, or other
particle shapes. They may be solid or substantially solid particles
such as carbon black, carbon fibers, nickel spheres, nickel coated
copper spheres, metal-coated oxides, metal-coated polymer fibers,
or other similar conductive particles. These conductive particles
can be made from electrically insulating materials that are plated
or coated with a conductive material such as silver, aluminum,
nickel, or indium tin-oxide. The metal-coated insulating material
can be substantially hollow particles such as hollow glass spheres,
or may comprise solid materials such as glass beads or metal
oxides. The conductive particles may be on the order of several
tens of microns to nanometer sized materials such as carbon
nanotubes. Suitable conductive adhesives may also include a
conductive polymeric matrix. In one aspect, conformable adhesive
layer 10 may include a continuous adhesive layer extending along
the entire length and width of shielding films 8. In another
aspect, conformable adhesive layer 10 may include a discontinuous
adhesive layer. For example, conformable adhesive layer 10 may be
present only in some portions along the length or width of
shielding films 8. In one embodiment, discontinuous adhesive layer
10 includes a plurality of longitudinal adhesive stripes that are
disposed, e.g., on both sides of each conductor set 4 and ground
conductors 12. In one embodiment, conformable adhesive layer 10
includes at least one of a pressure sensitive adhesive, a hot melt
adhesive, a thermoset adhesive, and a curable adhesive. In one
embodiment, conformable adhesive layer 10 is configured to provide
a bond between shielding films 8 that is substantially stronger
than a bond between one or more insulated conductor 6 and shielding
films 8. This may be achieved, e.g., by selecting the adhesive
formulation accordingly. An advantage of this adhesive
configuration is that shielding films 8 are readily strippable from
the insulation of insulated conductors 6. In another embodiment,
conformable adhesive layer 10 is configured to provide a bond
between shielding films 8 and a bond between one or more insulated
conductor 6 and shielding films 8 that are substantially equally
strong. An advantage of this adhesive configuration is that
insulated conductors 6 are anchored between shielding films 8. On
bending shielded electrical cable 2, this allows for little
relative movement and therefore reduces the likelihood of buckling
of shielding films 8. Suitable bond strengths may be chosen based
on the intended application. In one embodiment, conformable
adhesive layer 10 has a thickness of less than about 0.13 mm. In a
preferred embodiment, conformable adhesive layer 10 has a thickness
of less than about 0.05 mm.
[0058] Conformable adhesive layer 10 may conform to achieve desired
mechanical and electrical performance characteristics of shielded
electrical cable 2. In one aspect, conformable adhesive layer 10
may conform to be thinner between shielding films 8 in areas
between conductor sets 4, which increases at least the lateral
flexibility of shielded electrical cable 2. This allows shielded
electrical cable 2 to be placed more easily into a curvilinear
outer jacket, e.g. In another aspect, conformable adhesive layer 10
may conform to be thicker in areas immediately adjacent conductor
sets 4 and substantially conform to conductor sets 4. This
increases the mechanical strength and enables forming a curvilinear
shape of shielding films 8 in these areas, which increases the
durability of shielded electrical cable 2, e.g., during flexing of
the cable. In addition, this helps to maintain the position and
spacing of insulated conductors 6 relative to shielding films 8
along the length of shielded electrical cable 2, which results in
uniform impedance and superior signal integrity of shielded
electrical cable 2. In another aspect, conformable adhesive layer
10 may conform to effectively be partially of completely removed
between shielding films 8 in areas between conductor sets 4. As a
result, shielding films 8 electrically contact each other in these
areas, which increases the electrical performance of shielded
electrical cable 2. In another aspect, conformable adhesive layer
10 may conform to effectively be partially of completely removed
between at least one of shielding films 8 and ground conductors 12.
As a result, ground conductors 12 electrically contact at least one
of shielding films 8 in these areas, which increases the electrical
performance of shielded electrical cable 2. Even if a thin
conformable adhesive layer 10 exists between at least one of
shielding films 8 and ground conductors 12, asperities on ground
conductors 12 may break through conformable adhesive layer 10 to
establish electrical contact as intended.
[0059] FIGS. 8a-8c illustrate three other exemplary embodiments of
a shielded electrical cable according to aspects of the present
invention. FIGS. 8a-8c are specifically intended to illustrate
examples of the placement of ground conductors in the shielded
electrical cables. An aspect of a shielded electrical cable is
proper grounding of the shield. Shielded electrical cables
according to aspects of the present invention can be grounded in a
number of ways. In one aspect, the ground conductors electrically
contact at least one of the shielding films such that grounding the
ground conductors also grounds the shielding films. In this
arrangement, the ground conductors may also be referred to as
"drain wires". In another aspect, the ground conductors do not
electrically contact the shielding films, but are individual
elements in the cable construction that may be independently
terminated to any suitable individual contact element of any
suitable termination point, such as, e.g., a contact element on a
printed circuit board. In this arrangement, the ground conductors
may also be referred to as "ground wires". FIG. 8a illustrates an
exemplary embodiment of a shielded electrical cable according to an
aspect of the present invention wherein the ground conductors are
positioned external to the shielding films. FIGS. 8b-8c illustrate
two exemplary embodiments of a shielded electrical cable according
to aspects of the present invention wherein the ground conductors
are positioned between the shielding films, and may be included in
the conductor set. One or more ground conductors may be placed in
any suitable position external to the shielding films, between the
shielding films, or a combination of both.
[0060] Referring to FIG. 8a, shielded electrical cable 1202
includes a single conductor set 1204. Conductor set 1204 includes
two substantially parallel longitudinal insulated conductors 1206.
Two generally parallel shielding films 1208 are disposed around
conductor set 1204. A conformable adhesive layer 1210 is disposed
between shielding films 1208 and bonds shielding films 1208 to each
other on both sides of conductor set 1204. Insulated conductors
1206 are arranged generally in a single plane and effectively in a
twinaxial or differential pair cable arrangement. Shielded
electrical cable 1202 further includes a plurality of ground
conductors 1212 positioned external to shielding films 1208. Ground
conductors 1212 are placed over, under, and on both sides of
conductor set 1204. Optionally, shielded electrical cable 1202
includes protective films 1220 surrounding shielding films 1208 and
ground conductors 1212. Protective films 1220 include a protective
layer 1220a and an adhesive layer 1220b bonding protective layer
1220a to shielding films 1208 and ground conductors 1212.
Alternatively, shielding films 1208 and ground conductors 1212 may
be surrounded by an outer conductive shield, such as, e.g., a
conductive braid, and an outer insulative jacket (not shown).
[0061] Referring to FIG. 8b, shielded electrical cable 1302
includes a single conductor set 1304. Conductor set 1304 includes
two substantially parallel longitudinal insulated conductors 1306.
Two generally parallel shielding films 1308 are disposed around
conductor set 1304. A conformable adhesive layer 1310 is disposed
between shielding films 1308 and bonds shielding films 1308 to each
other on both sides of conductor set 1304. Insulated conductors
1306 are arranged generally in a single plane and effectively in a
twinaxial or differential pair cable arrangement. Shielded
electrical cable 1302 further includes a plurality of ground
conductors 1312 positioned between shielding films 1308. Two of the
ground conductors 1312 are included in conductor set 1304, and two
of the ground conductors 1312 are spaced apart from conductor set
1304.
[0062] Referring to FIG. 8c, shielded electrical cable 1402
includes a single conductor set 1404. Conductor set 1404 includes
two substantially parallel longitudinal insulated conductors 1406.
Two generally parallel shielding films 1408 are disposed around
conductor set 1404. A conformable adhesive layer 1410 is disposed
between shielding films 1408 and bonds shielding films 1408 to each
other on both sides of conductor set 1404. Insulated conductors
1406 are arranged generally in a single plane and effectively in a
twinaxial or differential pair cable arrangement. Shielded
electrical cable 1402 further includes a plurality of ground
conductors 1412 positioned between shielding films 1408. All of the
ground conductors 1412 are included in conductor set 1404. Two of
the ground conductors 1412 and insulated conductors 1406 are
arranged generally in a single plane.
[0063] FIGS. 9a-9b illustrate an exemplary embodiment of an
electrical assembly according to an aspect of the present invention
terminated to a printed circuit board. Electrical assembly 1500
includes a shielded electrical cable 1502 and an electrically
conductive cable clip 1522. Shielded electrical cable 1502 includes
a plurality of spaced apart conductor sets 1504 arranged generally
in a single plane. Each conductor set includes two substantially
parallel longitudinal insulated conductors 1506. Two generally
parallel shielding films 1508 are disposed around conductor sets
1504. A conformable adhesive layer 1510 is disposed between
shielding films 1508 and bonds shielding films 1508 to each other
on both sides of each conductor set 1504. Cable clip 1522 is
clamped or otherwise attached to an end portion of shielded
electrical cable 1502 such that at least one of shielding films
1508 electrically contacts cable clip 1522. Cable clip 1522 is
configured for termination to a ground reference, such as, e.g.,
contact element 1516 on printed circuit board 1514, to establish a
ground connection between shielded electrical cable 1502 and the
ground reference. Cable clip may be terminated to the ground
reference using any suitable method, including soldering, welding,
crimping, mechanical clamping, and adhesively bonding, to name a
few. When terminated, cable clip 1522 may facilitate termination of
the end portions of the conductors of insulated conductors 1506 of
shielded electrical cable 1502 to contact elements of a termination
point, such as, e.g., contact elements 16 on printed circuit board
14. Shielded electrical cable 1502 may include one or more ground
conductors as described herein that may electrically contact cable
clip 1522 in addition to or instead of at least one of shielding
films 1508.
[0064] FIGS. 10a-10g illustrate an exemplary method of making a
shielded electrical cable according to an aspect of the present
invention. Specifically, FIGS. 10a-10g illustrate an exemplary
method of making shielded electrical cable 2 illustrated in FIG.
1.
[0065] In the step illustrated in FIG. 10a, insulated conductors 6
are formed using any suitable method, such as, e.g., extrusion.
Insulated conductors 6 may be formed of any suitable length.
Insulated conductors 6 may then be provided as such or cut to a
desired length. Ground conductors 12 may be formed and provided in
a similar fashion (not shown). In the step illustrated in FIG. 10b,
shielding films 8 are formed. A single layer or multilayer web may
be formed using any suitable method, such as, e.g., continuous wide
web processing. Shielding films 8 may be formed of any suitable
length. Shielding films 8 may then be provided as such or cut to a
desired length and/or width. Shielding films 8 may be pre-formed to
have transverse partial folds to increase flexibility in the
longitudinal direction. As illustrated in FIG. 10b, shielding films
8 include conformable adhesive layer 10, which may be formed on
shielding films 8 using any suitable method, such as, e.g.,
laminating or sputtering. In the step illustrated in FIG. 10c, a
plurality of insulated conductors 6, ground conductors 12, and
shielding films 8 are provided. A forming tool 24 is provided.
Forming tool 24 includes a pair of forming rolls 26a, 26b having a
shape corresponding to a cross-sectional shape of shielded
electrical cable 2 and include a bite 28. Insulated conductors 6,
ground conductors 12, and shielding films 8 are arranged according
to the configuration of shielded electrical cable 2, and positioned
in proximity to forming rolls 26a, 26b, after which they are
concurrently fed into bite 28 of forming rolls 26a, 26b and
disposed between forming rolls 26a, 26b. Forming tool 24 forms
shielding films 8 around conductor sets 4 and ground conductor 12
and bonds shielding films 8 to each other on both sides of each
conductor set 4 and ground conductors 12. Heat may be applied to
facilitate bonding. Although in this embodiment, forming shielding
films 8 around conductor sets 4 and ground conductor 12 and bonding
shielding films 8 to each other on both sides of each conductor set
4 and ground conductors 12 occur in a single operation, in other
embodiments, these steps may occur in separate operations. FIG. 10d
illustrates shielded electrical cable 2 as it is formed by forming
tool 24. In the step illustrated in FIG. 10e, longitudinal splits
18 are formed between conductor sets 4. Splits 18 may be formed in
shielded electrical cable 2 using any suitable method, such as,
e.g., laser cutting or punching. In the step illustrated in FIG.
10f, shielding films 8 of shielded electrical cable 2 are folded
and an outer conductive shield 30 is provided around the folded
shielding films 8 using any suitable method. In the step
illustrated in FIG. 10g, an outer jacket 32 is provided around
outer conductive shield 30 using any suitable method, such as,
e.g., extrusion. In other embodiments, outer conductive shield 30
may be omitted and outer jacket 32 may be provided around the
folded shielding films 8.
[0066] FIGS. 11a-11c illustrate a detail of an exemplary method of
making a shielded electrical cable according to an aspect of the
present invention. FIGS. 11a-11c are specifically intended to
illustrate an example of the conforming of conformable adhesive
layers during the forming and bonding of shielding films.
[0067] In the step illustrated in FIG. 11a, an insulated conductor
1606, a ground conductor 1612 spaced apart from insulated conductor
1606, and two shielding films 1608 are provided. Shielding films
1608 each include a conformable adhesive layer 1610. In the steps
illustrated in FIGS. 11b-11c, shielding films 1608 are formed
around insulated conductor 1606 and ground conductor 1612 and
bonded to each other. Initially, as illustrated in FIG. 11b,
conformable adhesive layers 1610 still have their original
thickness. As the forming and bonding of shielding films 1608
proceeds, conformable adhesive layers 1610 conform to achieve
desired mechanical and electrical performance characteristics of
shielded electrical cable 1602. Specifically, as illustrated in
FIG. 11c, conformable adhesive layers 1610 conform to be thinner
between shielding films 1608 on both sides of insulated conductor
1606 and ground conductor 1612; a portion of conformable adhesive
layers 1610 displaces away from these areas. Further, conformable
adhesive layers 1610 conform to be thicker in areas immediately
adjacent insulated conductor 1606 and ground conductor 1612, and
substantially conform to insulated conductor 1606 and ground
conductor 1612; a portion of conformable adhesive layers 1610
displaces into these areas. Further, conformable adhesive layers
1610 conform to effectively be removed between shielding films 1608
and ground conductor 1612; conformable adhesive layers 1610
displace away from these areas such that ground conductor 1612
electrically contacts shielding films 1608.
[0068] In certain exemplary embodiments, the shielded electrical
cable according to an aspect of the present invention includes a
transition portion positioned on one or both sides of the conductor
set. This transition portion is configured to provide high
manufacturability and strain and stress relief of the shielded
electrical cable. Maintaining this transition portion at a
substantially constant configuration (including aspects such as,
e.g., size, shape, and content) along the length of the shielded
electrical cable facilitates the shielded electrical cable to have
substantially uniform electrical properties, such as, e.g.,
impedance, skew, insertion loss, reflection, mode conversion, eye
opening, and jitter. Additionally, in certain embodiments, such as,
e.g., embodiments wherein the conductor set includes two
substantially parallel longitudinal insulated conductors arranged
generally in a single plane and effectively in a twinaxial or
differential pair cable arrangement, maintaining this transition
portion at a substantially constant configuration along the length
of the shielded electrical cable beneficially provides
substantially the same electromagnetic field deviation from an
ideal concentric case for both conductors in the conductor set.
Thus, careful control of the configuration of this transition
portion along the length of the shielded electrical cable
contributes to the electrical performance of the cable. FIGS.
12a-14b illustrate various exemplary embodiments of a shielded
electrical cable according to aspects of the present invention that
include a transition portion disposed on one or both sides of the
conductor set.
[0069] Referring now to FIGS. 12a-12b, shielded electrical cable
1702 includes a single conductor set 1704. Conductor set 1704
includes a single longitudinal insulated conductor 1706. Two
generally parallel shielding films 1708 are disposed around
conductor set 1704. An optional conformable adhesive layer 1710 is
disposed between shielding films 1708 and bonds shielding films
1708 to each other on both sides of conductor set 1704. Insulated
conductor 1706 is effectively arranged in a coaxial or single ended
cable arrangement. Shielding films 1708 include a conductive layer
1708a and a non-conductive polymeric layer 1708b. Conductive layer
1708a faces insulated conductors 1706. This configuration of
shielding films 1708 is similar to the configuration of shielding
films 908 shown in FIG. 7b. Alternatively, the configuration of
shielding films 1708 may be similar to the configuration of
shielding films 808 shown in FIG. 7a, shielding films 1008 shown in
FIG. 7c, or shielding films 1108 shown in FIG. 7d, for example.
Shielding films 1708 include a concentric portion 1708'
substantially concentric with conductor 1706 and parallel portions
1708'' wherein shielding films 1708 are substantially parallel. In
other embodiments, shielding films 1708 may include a single
parallel portion 1708''. Shielded electrical cable 1702 further
includes transition portions 1734 positioned on both sides of
conductor set 1704. In other embodiments, shielded electrical cable
1702 may include a transition portion 1734 positioned on only one
side of conductor set 1704. Transition portions 1734 are defined by
shielding films 1708 and conductor set 1704 and provide a gradual
transition between concentric portion 1708' and parallel portion
1708'' of shielding films 1708. As opposed to a sharp transition,
such as, e.g., a right-angle transition or a transition point (as
opposed to a transition portion), a gradual transition, such as,
e.g., a substantially sigmoidal transition, provides strain and
stress relief for shielding films 1708 in transition portions 1734
and prevents damage to shielding films 1708 when shielded
electrical cable 1702 is in use, e.g., when laterally or axially
bending shielded electrical cable 1702. This damage may include,
e.g., fractures in conductive layer 1708a and/or debonding between
conductive layer 1708a and non-conductive polymeric layer 1708b. In
addition, a gradual transition prevents damage to shielding films
1708 in manufacturing of shielded electrical cable 1702, which may
include, e.g., cracking or shearing of conductive layer 1708a
and/or non-conductive polymeric layer 1708b.
[0070] The configuration of shielded electrical cables according
aspects of the present invention including a transition portion on
one or both sides of the conductor set represents a departure from
conventional cable configurations, such as, e.g., an ideal coaxial
cable, wherein a shield is generally continuously disposed around a
single insulated conductor, or an ideal twinaxial cable, wherein a
shield is generally continuously disposed around a pair of
insulated conductors. Although these ideal cable configurations
provide ideal electromagnetic profiles, these profiles are not
necessary to achieve acceptable electrical properties. In the
shielded electrical cables according to aspects of the present
invention, acceptable electrical properties can be achieved by
minimizing the electrical impact of the transition portion, e.g.,
by minimizing the size of the transition portion and carefully
controlling the configuration of the transition portion along the
length of the shielded electrical cable. Minimizing the size of the
transition portion minimizes the capacitance deviation and
minimizes the required space between multiple conductor sets,
thereby reducing the conductor set pitch and/or increasing the
electrical isolation between conductor sets. Careful control of the
configuration of the transition portion along the length of the
shielded electrical cable contributes to obtaining predictable
electrical behavior and consistency, which is important for high
speed transmission lines so that electrical data can be reliably
transmitted, and becomes more important when the size of the
transition portion cannot be minimized. An electrical
characteristic that is often considered is the characteristic
impedance of the transmission line. Any impedance changes along the
length of a transmission line may cause power to be reflected back
to the source instead of being transmitted to the target. Ideally,
the transmission line will have no impedance variation along its
length, but, depending on the intended application, variations up
to 5-10% may be acceptable. Another electrical characteristic that
is often considered in twinaxial cables (differentially driven) is
skew or unequal transmission speeds of two transmission lines of a
pair along at least a portion of their length. Skew produces
conversion of the differential signal to a common mode signal that
can be reflected back to the source, reduces the transmitted signal
strength, creates electromagnetic radiation, and dramatically
increases the bit error rate, in particular jitter. Ideally, a pair
of transmission lines will have no skew, but, depending on the
intended application, a differential S-parameter SCD21 or SCD12
value (representing the differential-to common mode conversion from
one end of the transmission line to the other) of less than -25 to
-30 dB up to a frequency of interest, such as, e.g., 6 GHz, may be
acceptable. Alternatively, skew can be measured in the time domain
and compared to a required specification. Depending on the intended
application, values of less than about 20 picoseconds/meter (ps/m)
and preferably less than about 10 ps/m may be acceptable.
[0071] Referring back to FIGS. 12a-12b, in part to help achieve
acceptable electrical properties, transition portions 1734 of
shielded electrical cable 1702 may each include a cross-sectional
area 1734a that is smaller than a cross-sectional area 1706a of
conductor 1706. As best shown in FIG. 12b, cross-sectional area
1734a of transition portion 1734 is defined by transition points
1734', where shielding films 1708 deviate from being substantially
concentric with insulated conductor 1706, and transition points
1734'', where shielding films 1708 deviate from being substantially
parallel. In addition, each cross-sectional area 1734a may include
a void portion 1734b. Void portions 1734b may be substantially the
same. Further, conformable adhesive layer 1710 may have a thickness
T.sub.ac in concentric portion 1708', and a thickness in transition
portion 1734 that is greater than thickness T.sub.ac in concentric
portion 1708'. Similarly, conformable adhesive layer 1710 may have
a thickness T.sub.ap in parallel portion 1708'', and a thickness in
transition portion 1734 that is greater than thickness T.sub.ap in
parallel portion 1708''. Conformable adhesive layer 1710 may
represent at least 25% of cross-sectional area 1734a. The presence
of conformable adhesive layer 1710 in cross-sectional area 1734a,
in particular at a thickness that is greater than thickness
T.sub.ac or thickness T.sub.ap, contributes to the strength of
transition portion 1734. Careful control of the manufacturing
process and the material characteristics of the various elements of
shielded electrical cable 1702 may reduce variations in void
portion 1734b and the thickness of conformable adhesive layer 1710
in transition portion 1734, which may in turn reduce variations in
the capacitance of cross-sectional area 1734a. Shielded electrical
cable 1702 may include a transition portion 1734 positioned on one
or both sides of conductor set 1704 that includes a cross-sectional
area 1734a that is substantially equal to or smaller than a
cross-sectional area 1706a of conductor 1706. Shielded electrical
cable 1702 may include a transition portion 1734 positioned on one
or both sides of conductor set 1704 that includes a cross-sectional
area 1734a that is substantially the same along the length of
conductor 1706. For example, cross-sectional area 1734a may vary
less than 50% over a length of 1 m. Shielded electrical cable 1702
may include transition portions 1734 positioned on both sides of
conductor set 1704 that each include a cross-sectional area 1734a,
wherein the sum of cross-sectional areas 1734a is substantially the
same along the length of conductor 1706. For example, the sum of
cross-sectional areas 1734a may vary less than 50% over a length of
1 m. Shielded electrical cable 1702 may includes transition
portions 1734 positioned on both sides of conductor set 1704 that
each include a cross-sectional area 1734a, wherein the
cross-sectional areas 1734a are substantially the same. Shielded
electrical cable 1702 may include transition portions 1734
positioned on both sides of conductor set 1704, wherein the
transition portions 1734 are substantially identical. Insulated
conductor 1706 has an insulation thickness T.sub.i,and transition
portion 1734 may have a lateral length L.sub.t that is less than
insulation thickness T.sub.i. Insulated conductor 1706 has a
diameter D.sub.c, and transition portion 1734 may have a lateral
length L.sub.t that is less than diameter D.sub.c. The various
configurations described above may provide a characteristic
impedance that remains within a desired range, such as, e.g.,
within 5-10% of a target impedance value, such as, e.g., 50 Ohms,
over a given length, such as, e.g., 1 m.
[0072] Factors that control the configuration of transition portion
1734 along the length of shielded electrical cable 1702 include the
manufacturing process, the thickness of conductive layers 1708a and
non-conductive polymeric layers 1708b, conformable adhesive layer
1710, and the bond strength between insulated conductor 1706 and
shielding films 1708, to name a few.
[0073] In one aspect, conductor set 1704, shielding films 1708, and
transition portion 1734 are cooperatively configured in an
impedance controlling relationship. An impedance controlling
relationship means that conductor set 1704, shielding films 1708,
and transition portion 1734 are cooperatively configured to control
the characteristic impedance of the shielded electrical cable.
[0074] FIGS. 13a-13b illustrate two other exemplary embodiments of
a shielded electrical cable according to aspects of the present
invention including two insulated conductors. Referring to FIG.
13a, shielded electrical cable 1802 includes a single conductor set
1804 including two substantially parallel longitudinal individually
insulated conductors 1806. Two generally parallel shielding films
1808 are disposed around conductor set 1804. An optional
conformable adhesive layer 1810 is disposed between shielding films
1808 and bonds shielding films 1808 to each other on both sides of
conductor set 1804. Insulated conductors 1806 are arranged
generally in a single plane and effectively in a twinaxial or
differential pair cable arrangement. Shielding films 1808 include a
conductive layer 1808a and a non-conductive polymeric layer 1808b.
Conductive layer 1808a faces insulated conductors 1806. Shielding
films 1808 include concentric portions 1808' substantially
concentric with corresponding conductors 1806 and parallel portions
1808'' wherein shielding films 1808 are substantially parallel.
Shielded electrical cable 1802 includes transition portions 1834
positioned on both sides of conductor set 1804 that each include a
cross-sectional area 1834a, wherein the sum of cross-sectional
areas 1834a is substantially the same along the length of
conductors 1806. For example, the sum of cross-sectional areas
1834a may vary less than 50% over a length of 1 m. In addition,
cross-sectional areas 1834a are substantially the same and
transition portions 1834 are substantially identical. This
configuration of transition portions 1834 may provide a
characteristic impedance for each conductor 1806 (single-ended) and
a differential impedance that both remain within a desired range,
such as, e.g., within 5-10% of a target impedance value over a
given length, such as, e.g., 1 m. In addition, this configuration
of transition portions 1834 may minimize skew of the two conductors
1806 along at least a portion of their length. Referring to FIG.
13b, shielded electrical cable 1902 is similar to shielded
electrical cable 1802. Whereas shielded electrical cable 1802 has
individually insulated conductors 1806, shielded electrical cable
1902 has jointly insulated conductors 1906. Nonetheless, transition
portions 1934 are identical to transition portions 1834 and provide
the same benefits to shielded electrical cable 1902.
[0075] FIGS. 14a-14b illustrate two other exemplary embodiments of
a shielded electrical cable according to aspects of the present
invention including two insulated conductors. These exemplary
embodiments are intended to illustrate variations in position and
configuration of the transition portions. Shielded electrical
cables 2002 (FIGS. 14a) and 2102 (FIG. 14b) are similar to shielded
electrical cable 1802. Whereas in shielded electrical cable 1802,
parallel portions 1808'' of shielding films 1808 and insulated
conductors 1806 are arranged generally in a single plane, in
shielded electrical cables 2002 and 2102, parallel portions 2008''
and 2108'' of shielding films 2008 and 2108 and insulated
conductors 2006 and 2106 are arranged in different planes. As a
result, transition portions 2034 and 2134 have a different position
and configuration. For reasons including that transition portions
2034 and 2134 are positioned substantially symmetrically with
respect to corresponding insulated conductors 2006 and 2106 and
that the configuration of transition portions 2034 and 2134 is
carefully controlled along the length of shielded electrical cables
2002 and 2102, shielded electrical cables 2002 and 2102 are
configured to still provide acceptable electrical properties.
[0076] In further exemplary embodiments, shielded electrical cables
according to aspects of the present invention include a plurality
of spaced apart conductor sets arranged generally in a single
plane. Each conductor set includes one or more substantially
parallel longitudinal insulated conductors. Two generally parallel
shielding films are disposed around the conductor sets and include
a plurality of concentric portions substantially concentric with at
least one of the conductors and a plurality of parallel portions
wherein the shielding films are substantially parallel. A plurality
of transition portions defined by the shielding films and the
conductor sets provide a gradual transition between the concentric
portions and the parallel portions of the shielding films. The
transition portions may be positioned on both sides of each
conductor set. For example, the shielded electrical cable may
include a combination of one or more conductor sets 1704, wherein
insulated conductor 1706 is effectively arranged in a coaxial or
single ended cable arrangement, and one or more conductor sets
1804, wherein insulated conductors 1806 are effectively arranged in
a twinaxial or differential pair cable arrangement. The conductor
sets, shielding films and transition portions may be cooperatively
configured in an impedance controlling relationship.
[0077] FIGS. 15a-15c, 18 and 19 illustrate several other exemplary
embodiments of a shielded electrical cable according to aspects of
the present invention. FIGS. 16a-16g, 17a-17b and 20a-20f
illustrate several exemplary embodiments of a parallel portion of a
shielded electrical cable according to aspects of the present
invention. FIGS. 15a-20f are specifically intended to illustrate
examples of a parallel portion that is configured to electrically
isolate a conductor set of the shielded electrical cable. The
conductor set may be electrically isolated from an adjacent
conductor set (e.g., to minimize crosstalk between adjacent
conductor sets, FIGS. 15a-15c and 16a-16g) or from the external
environment of the shielded electrical cable (e.g., to minimize
electromagnetic radiation escape from the shielded electrical cable
and minimize electromagnetic interference from external sources,
FIGS. 19 and 20a-20f). In both cases, the parallel portion may
include various mechanical structures to realize the electrical
isolation. Examples include close proximity of the shielding films,
high dielectric constant material between the shielding films,
ground conductors that make direct or indirect electrical contact
with at least one of the shielding films, extended distance between
adjacent conductor sets, physical breaks between adjacent conductor
sets, intermittent contact of the shielding films to each other
directly either longitudinally, transversely, or both, and
conductive adhesive, to name a few. In one aspect, a parallel
portion of the shielding films is defined as a portion of the
shielding films that is not covering a conductor set.
[0078] In FIGS. 15a, shielded electrical cable 2202 includes two
conductor sets 2204, each including two substantially parallel
longitudinal insulated conductors 2206, and two generally parallel
shielding films 2208 disposed around conductor sets 2204. Shielding
films 2208 include parallel portions 2208'' wherein shielding films
2208 are substantially parallel. Parallel portions 2208''
positioned in between conductor sets 2204 are configured to
electrically isolate conductor sets 2204 from each other. In
shielded electrical cable 2202, parallel portions 2208'' of
shielding films 2208 and insulated conductors 2206 are arranged
generally in a single plane.
[0079] In FIGS. 15b, shielded electrical cable 2302 includes two
conductor sets 2304, each including one longitudinal insulated
conductor 2306, and two generally parallel shielding films 2308
disposed around conductor sets 2304. Shielding films 2308 include
parallel portions 2308'' wherein shielding films 2308 are
substantially parallel. Parallel portions 2308'' positioned in
between conductor sets 2304 are configured to electrically isolate
conductor sets 2304 from each other. In shielded electrical cable
2302, parallel portions 2308'' of shielding films 2308 and
insulated conductors 2306 are arranged generally in a single
plane.
[0080] In FIGS. 15c, shielded electrical cable 2402 includes two
conductor sets 2404, each including two substantially parallel
longitudinal insulated conductors 2406, and two generally parallel
shielding films 2408 disposed around conductor sets 2404. Shielding
films 2408 include parallel portions 2408'' wherein shielding films
2408 are substantially parallel. Parallel portions 2408''
positioned in between conductor sets 2404 are configured to
electrically isolate conductor sets 2404 from each other. In
shielded electrical cable 2402, parallel portions 2408'' of
shielding films 2408 and insulated conductors 2406 are arranged in
different planes.
[0081] In FIG. 16a, shielded electrical cable 2502 includes a
parallel portion 2508'' wherein shielding films 2508 are spaced
apart. Spacing apart shielding films 2508, i.e., not having
shielding films 2508 make direct electrical contact continuously
along their seam, increases the strength of parallel portion
2508''. This is an advantage over shielded electrical cables
wherein relatively thin and fragile shielding films may fracture or
crack during manufacturing if forced to make direct electrical
contact continuously along their seam. Spacing apart shielding
films 2508 may permit crosstalk between adjacent conductor sets if
effective means are not used to reduce the crosstalk potential.
Generally, the electrical and magnetic fields must be contained to
the general area of the conductor sets and not permitted to impinge
on an adjacent conductor set. In the embodiment illustrated in FIG.
16a, this is achieved by providing a low characteristic impedance
between shielding films 2508. This may be accomplished by spacing
apart shielding films 2508 at close proximity. In one embodiment,
shielding films 2508 are spaced apart by less than about 0.13 mm in
at least one location of parallel portion 2508''. The resulting
characteristic impedance between shielding films 2508 may be less
than about 15 Ohms, and the resulting crosstalk between adjacent
conductor sets may be less than about -25 dB. In one embodiment,
parallel portion 2508'' has a minimum thickness of less than about
0.13 mm. In one embodiment, shielding films 2508 are spaced apart
by a separation medium. The separation medium may include
conformable adhesive layer 2510. In one embodiment, the separation
medium has a dielectric constant of at least 1.5. A high dielectric
constant decreases the characteristic impedance between shielding
films 2508, thereby decreasing the crosstalk (increasing the
electrical isolation) between adjacent conductor sets. Shielding
films 2508 may make direct electrical contact with each other in at
least one location of parallel portion 2508''. Shielding films 2508
may be forced together in selective locations as suitable for the
intended application such that conformable adhesive layer 2510
conforms around these locations. This can be done, e.g., with a
patterned tool making intermittent pinch contact between shielding
films 2508 in these locations. These locations may be patterned
longitudinally or transversely. In one embodiment, the separation
medium may be electrically conductive to enable direct electrical
contact between shielding films 2508.
[0082] In FIG. 16b, shielded electrical cable 2602 includes a
parallel portion 2608'' including a longitudinal ground conductor
2612 disposed between shielding films 2608. Ground conductor 2612
makes indirect electrical contact with both shielding films 2608.
Ground conductor 2612 has a low but non-zero impedance with respect
to shielding films 2608. In other embodiments, ground conductor
2612 may make direct or indirect electrical contact with at least
one of the shielding films 2608 in at least one location of
parallel portion 2608''. In one embodiment, shielded electrical
cable 2602 includes a conformable adhesive layer 2610 disposed
between shielding films 2608 and configured to provide controlled
separation of at least one of shielding films 2608 and ground
conductor 2612. In one aspect, this means that conformable adhesive
layer 2610 has a non-uniform thickness that allows ground conductor
2612 to make direct or indirect electrical contact with at least
one of shielding films 2608 in selective locations as suitable for
the intended application. In one embodiment, ground conductor 2612
may include surface asperities or a deformable wire, such as, e.g.,
a stranded wire, to provide this controlled electrical contact
between ground conductor 2612 and at least one of shielding films
2608.
[0083] In FIG. 16c, shielded electrical cable 2702 includes a
parallel portion 2708'' including a longitudinal ground conductor
2712 disposed between shielding films 2708. Ground conductor 2712
makes direct electrical contact with both shielding films 2708.
[0084] In FIG. 16d, shielded electrical cable 2802 includes a
parallel portion 2808'' wherein shielding films 2808 make direct
electrical contact with each other by any suitable means, such as,
e.g., conductive element 2844. Conductive element 2844 may include
a conductive plated via or channel, a conductive filled via or
channel, or a conductive adhesive, to name a few.
[0085] In FIG. 16e, shielded electrical cable 2902 includes a
parallel portion 2908'' including an opening 2936 in at least one
location of parallel portion 2908''. In other words, parallel
portion 2908'' is discontinuous. Opening 2936 may include a hole, a
perforation, a slit, and any other suitable element. Opening 2936
provides at least some level of physical separation, which
contributes to the electrical isolation performance of parallel
portion 2908'' and increases at least the lateral flexibility of
shielded electrical cable 2902. This separation may be
discontinuous along the length of parallel portion 2908'', and may
be discontinuous across the width of parallel portion 2908''.
[0086] In FIG. 16f, shielded electrical cable 3002 includes a
parallel portion 3008'' wherein at least one of shielding films
3008 includes a break 3038 in at least one location of parallel
portion 3008''. In other words, at least one of shielding films
3008 is discontinuous. Break 3038 may include a hole, a
perforation, a slit, and any other suitable element. Break 3038
provides at least some level of physical separation, which
contributes to the electrical isolation performance of parallel
portion 3008'' and increases at least the lateral flexibility of
shielded electrical cable 3002. This separation may be
discontinuous or continuous along the length of parallel portion
3008'', and may be discontinuous across the width of parallel
portion 3008''.
[0087] In FIG. 16g, shielded electrical cable 3102 includes a
parallel portion 3108'' that is piecewise planar in a folded
configuration. All other things being equal, a piecewise planar
parallel portion has a greater actual width than a planar parallel
portion having the same projected width. If the actual width of a
parallel portion is much greater than the spacing between the
shielding films, a low characteristic impedance results, which
contributes to the electrical isolation performance of the parallel
portion. In one embodiment, a characteristic impedance of less than
5 to 10 Ohms results in good electrical isolation. In one
embodiment, parallel portion 3108'' of shielded electrical cable
3102 has an actual width to minimum spacing ratio of at least 5. In
one embodiment, parallel portion 3108'' is pre-bent and thereby
increases at least the lateral flexibility of shielded electrical
cable 3102. Parallel portion 3108'' may be piecewise planar in any
other suitable configuration.
[0088] Referring now to FIGS. 17a-17b, another exemplary embodiment
of a parallel portion of a shielded electrical cable according to
an aspect of the present invention is illustrated. Shielded
electrical cable 3202 includes two generally parallel shielding
films 3208 include a parallel portion 3208'' wherein shielding
films 3208 are substantially parallel. Shielding films 3208 include
a non-conductive polymeric layer 3208b, a conductive layer 3208a
disposed on non-conductive polymeric layer 3208b, and a stop layer
3208d disposed on conductive layer 3208a. A conformable adhesive
layer 3210 is disposed on stop layer 3208d. Parallel portion 3208''
includes a longitudinal ground conductor 3212 disposed between
shielding films 3208. Ground conductor 3212 makes indirect
electrical contact with conductive layers 3208a of shielding films
3208. This indirect electrical contact is enabled by a controlled
separation of conductive layer 3208a and ground conductor 3212
provided by stop layer 3208d. In one embodiment, stop layer 3208d
is a non-conductive polymeric layer. As shown in FIGS. 17a-17b, an
external pressure (FIG. 17a) is used to press conductive layers
3208a together and force conformable adhesive layers 3210 to
conform around ground conductor 3212 (FIG. 17b). Because stop layer
3208d does not conform at least under the same conditions, it
prevents direct electrical contact between ground conductor 3212
and conductive layer 3208a of shielding films 3208. The thickness
and dielectric properties of stop layer 3208d may be selected to
achieve a target characteristic impedance. In one embodiment, a
characteristic impedance of less than 5 to 10 Ohms results in good
electrical isolation.
[0089] FIG. 18 illustrates another exemplary embodiment of a
shielded electrical cable according to an aspect of the present
invention. Shielded electrical cable 3302 includes two generally
parallel shielding films 3308 disposed around spaced apart
conductor sets 3304. Shielding films 3308 include parallel portions
3308'' wherein shielding films 3308 are substantially parallel.
Parallel portions 3308'' are configured to be laterally bent at an
angle a of at least 30.degree.. This lateral flexibility of
parallel portions 3308'' enables shielded electrical cable 3302 to
be folded in any suitable configuration, such as, e.g., a
configuration that can be used in a round cable (see, e.g., FIG.
10g). In one embodiment, the lateral flexibility of parallel
portions 3308'' is enabled by shielding films 3308 including two or
more relatively thin individual layers. To warrant the integrity of
these individual layers in particular under bending conditions, it
is preferred that the bonds between them remain intact. In one
embodiment, parallel portions 3308'' have a minimum thickness of
less than about 0.13 mm, and the bond strength between individual
layers is at least 17.86 g/mm (1 lbs/inch) after thermal exposures
during processing or use.
[0090] In one aspect, it is beneficial to the electrical
performance of a shielded electrical cable according to aspect of
the present invention for the parallel portions to have
approximately the same size and shape on both sides of a conductor
set. Any dimensional changes or imbalances may produce imbalances
in capacitance and inductance along the length of the parallel
portion. This in turn may cause impedance differences along the
length of the parallel portion and impedance imbalances between
adjacent conductor sets. At least for these reasons, control of the
spacing between the shielding films may be desired. In one
embodiment, the shielding films on both sides of a conductor set
are spaced apart within about 0.05 mm of each other.
[0091] In FIG. 19, shielded electrical cable 3402 includes two
conductor sets 3404, each including two substantially parallel
longitudinal insulated conductors 3406, and two generally parallel
shielding films 3408 disposed around conductor sets 3404. Shielding
films 3408 include parallel portions 3408'' wherein shielding films
3408 are substantially parallel. Parallel portions 3408''
positioned at or near an edge of shielded electrical cable 3402 are
configured to electrically isolate conductor sets 3404 from the
external environment. In shielded electrical cable 3402, parallel
portions 3408'' of shielding films 3408 and insulated conductors
3406 are arranged generally in a single plane.
[0092] In FIG. 20a, shielded electrical cable 3502 includes a
parallel portion 3508'' wherein shielding films 3508 are spaced
apart. Parallel portion 3508'' is similar to parallel portion
2508'' described above and illustrated in FIG. 16a. Whereas
parallel portion 2508'' is positioned in between conductor sets,
parallel portion 3508'' is positioned at or near an edge of
shielded electrical cable 3502.
[0093] In FIG. 20b, shielded electrical cable 3602 includes a
parallel portion 3608'' including a longitudinal ground conductor
3612 disposed between shielding films 3608. Parallel portion 3608''
is similar to parallel portion 2608'' described above and
illustrated in FIG. 16b. Whereas parallel portion 2608'' is
positioned in between conductor sets, parallel portion 3608'' is
positioned at or near an edge of shielded electrical cable
3602.
[0094] In FIG. 20c, shielded electrical cable 3702 includes a
parallel portion 3708'' including a longitudinal ground conductor
3712 disposed between shielding films 3708. Parallel portion 3708''
is similar to parallel portion 2708'' described above and
illustrated in FIG. 16c. Whereas parallel portion 2708'' is
positioned in between conductor sets, parallel portion 3708'' is
positioned at or near an edge of shielded electrical cable
3702.
[0095] In FIG. 20d, shielded electrical cable 3802 includes a
parallel portion 3808'' wherein shielding films 3808 make direct
electrical contact with each other by any suitable means, such as,
e.g., conductive element 3844. Conductive element 3844 may include
a conductive plated via or channel, a conductive filled via or
channel, or a conductive adhesive, to name a few. Parallel portion
3808'' is similar to parallel portion 2808'' described above and
illustrated in FIG. 16d. Whereas parallel portion 2808'' is
positioned in between conductor sets, parallel portion 3808'' is
positioned at or near an edge of shielded electrical cable
3802.
[0096] In FIG. 20e, shielded electrical cable 3902 includes a
parallel portion 3908'' that is piecewise planar in a folded
configuration. Parallel portion 3908'' is similar to parallel
portion 3108'' described above and illustrated in FIG. 16g. Whereas
parallel portion 3108'' is positioned in between conductor sets,
parallel portion 3908'' is positioned at or near an edge of
shielded electrical cable 3902.
[0097] In FIG. 20f, shielded electrical cable 4002 includes a
parallel portion 4008'' that is piecewise planar in a curved
configuration and positioned at or near an edge of shielded
electrical cable 4002.
[0098] A shielded electrical cable according to an aspect of the
present invention may include at least one longitudinal ground
conductor, an electrical article extending in substantially the
same direction as the ground conductor, and two generally parallel
shielding films disposed around the ground conductor and the
electrical article. In this configuration, the shielding films and
ground conductor are configured to electrically isolate the
electrical article. The ground conductor may extend beyond at least
one of the ends of the shielding films, e.g., for termination of
the shielding films to any suitable individual contact element of
any suitable termination point, such as, e.g., a contact element on
a printed circuit board or an electrical contact of an electrical
connector. Beneficially, only a limited number of ground conductors
is needed for a cable construction, and can, along with the
shielding films, complete an electromagnetic enclosure of the
electrical article. The electrical article may include at least one
longitudinal conductor, at least one conductor set including one or
more substantially parallel longitudinal insulated conductors, a
flexible printed circuit, or any other suitable electrical article
of which electrical isolation is desired. FIGS. 21a-21b illustrate
two exemplary embodiments of such shielded electrical cable
configuration.
[0099] In FIG. 21a, shielded electrical cable 4102 includes two
spaced apart substantially parallel longitudinal ground conductors
4112, an electrical article 4140 positioned between and extending
in substantially the same direction as ground conductors 4112, and
two generally parallel shielding films 4108 disposed around ground
conductors 4112 and electrical article 4140. Electrical article
4140 includes three conductor sets 4104. Each conductor set 4104
includes two substantially parallel longitudinal insulated
conductors 4106. Ground conductors 4112 make indirect electrical
contact with both shielding films 4108. Ground conductors 4112 have
a low but non-zero impedance with respect to shielding films 4108.
In other embodiments, ground conductors 4112 may make direct or
indirect electrical contact with at least one of the shielding
films 4108 in at least one location of shielding films 4108. In one
embodiment, shielded electrical cable 4102 includes a conformable
adhesive layer 4110 disposed between shielding films 4108 and
bonding shielding films 4108 to each other on both sides of ground
conductors 4112 and electrical article 4140. Conformable adhesive
layer 4110 is configured to provide controlled separation of at
least one of shielding films 4108 and ground conductors 4112. In
one aspect, this means that conformable adhesive layer 4110 has a
non-uniform thickness that allows ground conductors 4112 to make
direct or indirect electrical contact with at least one of
shielding films 4108 in selective locations as suitable for the
intended application. In one embodiment, ground conductors 4112 may
include surface asperities or a deformable wire, such as, e.g., a
stranded wire, to provide this controlled electrical contact
between ground conductors 4112 and at least one of shielding films
4108. In one embodiment, shielding films 4108 are spaced apart by a
minimum spacing in at least one location of shielding films 4108,
and ground conductors 4112 have a thickness that is greater than
the minimum spacing. In one embodiment, shielding films 4108 have a
thickness of less than about 0.025 mm.
[0100] In FIG. 21b, shielded electrical cable 4202 includes two
spaced apart substantially parallel longitudinal ground conductors
4212, an electrical article 4240 positioned between and extending
in substantially the same direction as ground conductors 4212, and
two generally parallel shielding films 4208 disposed around ground
conductors 4212 and electrical article 4240. Shielded electrical
cable 4202 is similar to shielded electrical cable 4102 described
above and illustrated in FIG. 21a. Whereas in shielded electrical
cable 4102, electrical article 4140 includes three conductor sets
4104 each including two substantially parallel longitudinal
insulated conductors 4106, in shielded electrical cable 4202,
electrical article 4240 includes a flexible printed circuit
including three conductor sets 4242.
[0101] FIG. 22 illustrates the far end crosstalk (FEXT) isolation
between two adjacent conductor sets of a conventional electrical
cable wherein the conductor sets are completely isolated, i.e.,
have no common ground (Sample 1), and between two adjacent
conductor sets of shielded electrical cable 2202 illustrated in
FIG. 15a wherein shielding films 2208 are spaced apart by about
0.025 mm (Sample 2), both having a cable length of about 3 m. The
test method for creating this data is well known in the art. The
data was generated using an Agilent 8720ES 50 MHz-20 GHz
S-Parameter Network Analyzer. It can be seen by comparing the far
end crosstalk plots that the conventional electrical cable and
shielded electrical cable 2202 provide a similar far end crosstalk
performance. Specifically, it is generally accepted that a far end
crosstalk of less than about -35 dB is suitable for most
applications. It can be easily seen from FIG. 22 that for the
configuration tested, both the conventional electrical cable and
shielded electrical cable 2202 provide satisfactory electrical
isolation performance. The satisfactory electrical isolation
performance in combination with the increased strength of the
parallel portion due to the ability to space apart the shielding
films is an advantage of a shielded electrical cable according to
an aspect of the present invention over conventional electrical
cables.
[0102] In exemplary embodiments described above, the shielded
electrical cable includes two generally parallel shielding films
disposed around a conductor set or around a plurality of spaced
apart conductor sets. In further embodiments, the shielded
electrical cable may include a single shielding film. Advantages of
a shielded electrical cable including a single shielding film,
compared to a shielded electrical cable including two shielding
films, include a decrease in its material cost and an increase in
its mechanical flexibility, manufacturability, and ease of
stripping and termination. A single shielding film may provide an
acceptable level of electromagnetic interference (EMI) isolation
and may reduce the proximity effect thereby decreasing signal
attenuation. FIGS. 23-29d illustrate various exemplary embodiments
of a shielded electrical cable according to aspects of the present
invention including a single shielding film.
[0103] Referring now to FIG. 23, shielded electrical cable 4302
includes two spaced apart conductor sets 4304 and a single
shielding film 4308. Each conductor set 4304 includes a single
longitudinal insulated conductor 4306. Insulated conductors 4306
are arranged generally in a single plane and effectively in a
coaxial or single ended cable arrangement. Shielding film 4308
includes parallel portions 4308'' extending from both sides of each
conductor set 4304. Parallel portions 4308'' cooperatively define a
generally planar shielding film. Shielding film 4308 further
includes two cover portions 4308''' each partially covering a
conductor set 4304. Each cover portion 4308''' includes a
concentric portion 4308' substantially concentric with
corresponding conductor 4306. Shielding film 4308 includes a
conductive layer 4308a and a non-conductive polymeric layer 4308b.
Conductive layer 4308a faces insulated conductors 4306. Shielded
electrical cable 4302 further includes an optional non-conductive
carrier film 4346. Carrier film 4346 includes parallel portions
4346'' extending from both sides of each conductor set 4304 and
disposed opposite parallel portions 4308'' of shielding film 4308.
Carrier film 4346 further includes two cover portions 4346' each
partially covering a conductor set 4304 opposite cover portion
4308''' of shielding film 4308. Each cover portion 4346''' includes
a concentric portion 4346' substantially concentric with
corresponding conductor 4306. Carrier film 4346 may include any
suitable polymeric material, including but not limited to
polyester, polyimide, polyamide-imide, polytetrafluoroethylene,
polypropylene, polyethylene, polyphenylene sulfide, polyethylene
naphthalate, polycarbonate, silicone rubber, ethylene propylene
diene rubber, polyurethane, acrylates, silicones, natural rubber,
epoxies, and synthetic rubber adhesive. Carrier film 4346 may
include one or more additives and/or fillers to provide properties
suitable for the intended application. Carrier film 4346 may be
used to complete physical coverage of conductor sets 4304 and add
to the mechanical stability of shielded electrical cable 4302.
[0104] Referring to FIG. 24, shielded electrical cable 4402 is
similar to shielded electrical cable 4302 described above and
illustrated in FIG. 23. Whereas shielded electrical cable 4302
includes conductor sets 4304 each including a single longitudinal
insulated conductor 4306, shielded electrical cable 4402 includes
conductor sets 4404 including two substantially parallel
longitudinal insulated conductors 4406. Insulated conductors 4406
are arranged generally in a single plane and effectively in a
twinaxial or differential pair cable arrangement.
[0105] Referring to FIG. 25, shielded electrical cable 4502 is
similar to shielded electrical cable 4402 described above and
illustrated in FIG. 24. Whereas shielded electrical cable 4402 has
individually insulated conductors 4406, shielded electrical cable
4502 has jointly insulated conductors 4506.
[0106] In one aspect, as can be seen in FIGS. 23-25, the shielding
film is re-entrant between adjacent conductor sets. In other words,
the shielding film includes a parallel portion that is disposed
between adjacent conductor sets. This parallel portion is
configured to electrically isolate the adjacent conductor sets from
each other. In one aspect, the parallel portion eliminates the need
for a ground conductor to be positioned between adjacent conductor
sets, which simplifies the cable construction and increases the
cable flexibility, among other benefits. In one embodiment, the
parallel portion is positioned at a depth d (FIG. 23) that is
greater than about one third of the diameter of the insulated
conductors. In another embodiment, the parallel portion is
positioned at a depth d that is greater than about one half of the
diameter of the insulated conductors. In one aspect, depending on
the spacing between adjacent conductor sets, the transmission
distance, and the signaling scheme (differential versus
single-ended), this re-entrant configuration of the shielding film
more than adequately electrically isolates the conductor sets from
each other.
[0107] The conductor sets and shielding film may be cooperatively
configured in an impedance controlling relationship. In one aspect,
this means that the partial coverage of the conductor sets by the
shielding film is accomplished with a desired consistency in
geometry along the length of the shielded electrical cable such as
to provide an acceptable impedance variation as suitable for the
intended application. In one embodiment, this impedance variation
is less than 5 Ohms and preferably less than 3 Ohms along a
representative cable length, such as, e.g., 1 m. In another aspect,
if the insulated conductors are arranged effectively in a twinaxial
or differential pair cable arrangement, this means that the partial
coverage of the conductor sets by the shielding film is
accomplished with a desired consistency in geometry between the
insulated conductors of a pair such as to provide an acceptable
impedance variation as suitable for the intended application. In
one embodiment, this impedance variation is less than 2 Ohms and
preferably less than 0.5 Ohms along a representative cable length,
such as, e.g., 1 m.
[0108] FIGS. 26a-26d illustrate various exemplary embodiments of a
shielded electrical cable according to aspects of the present
invention. FIGS. 26a-26d are specifically intended to illustrate
various examples of partial coverage of the conductor set by the
shielding film. The amount of coverage by the shielding film varies
between the embodiments. In the embodiment illustrated in FIG. 26a,
the conductor set has the most coverage. In the embodiment
illustrated in FIG. 26d, the conductor set has the least coverage.
In the embodiments illustrated in FIGS. 26a and 26b, more than half
of the periphery of the conductor set is covered by the shielding
film. In the embodiments illustrated in FIGS. 26c and 26d, less
than half of the periphery of the conductor set is covered by the
shielding film. A greater amount of coverage provides better
electromagnetic interference (EMI) isolation and reduced signal
attenuation (resulting from a reduction in the proximity
effect).
[0109] Referring to FIG. 26a, shielded electrical cable 4602
includes a conductor set 4604 and a shielding film 4608. Conductor
set 4604 includes two longitudinal insulated conductors 4606.
Shielding film 4608 includes parallel portions 4608'' extending
from both sides of conductor set 4604. Parallel portions 4608''
cooperatively define a generally planar shielding film. Shielding
film 4608 further includes a cover portion 4608''' partially
covering conductor set 4604. Cover portion 4608''' includes
concentric portions 4608' substantially concentric with
corresponding conductor 4306. Shielded electrical cable 4602
further includes an optional non-conductive carrier film 4646.
Carrier film 4646 includes parallel portions 4646'' extending from
both sides of conductor set 4604 and disposed opposite parallel
portions 4608'' of shielding film 4608. Carrier film 4646 further
includes a cover portion 4646''' partially covering conductor set
4604 opposite cover portion 4608''' of shielding film 4608. Cover
portion 4608''' of shielding film 4608 covers the top side and the
entire left and right sides of conductor set 4604. Cover portion
4646''' of carrier film 4646 covers the bottom side of conductor
set 4604, completing the enclosure of conductor set 4604. In this
embodiment, parallel portions 4646'' and cover portion 4646''' of
carrier film 4646 are substantially coplanar.
[0110] Referring to FIG. 26b, shielded electrical cable 4702 is
similar to shielded electrical cable 4602 described above and
illustrated in FIG. 26a. However, in shielded electrical cable
4702, cover portion 4708''' of shielding film 4708 covers the top
side and more than half of the left and right sides of conductor
set 4704. Cover portion 4746''' of carrier film 4746 covers the
bottom side and the remainder (less than half) of the left and
right sides of conductor set 4704, completing the enclosure of
conductor set 4704. Cover portion 4746''' of carrier film 4746
includes concentric portions 4746' substantially concentric with
corresponding conductor 4706.
[0111] Referring to FIG. 26c, shielded electrical cable 4802 is
similar to shielded electrical cable 4602 described above and
illustrated in FIG. 26a. However, in shielded electrical cable
4802, cover portion 4808''' of shielding film 4808 covers the
bottom side and less than half of the left and right sides of
conductor set 4804. Cover portion 4846''' of carrier film 4846
covers the top side and the remainder (more than half) of the left
and right sides of conductor set 4804, completing the enclosure of
conductor set 4804.
[0112] Referring to FIG. 26d, shielded electrical cable 4902 is
similar to shielded electrical cable 4602 described above and
illustrated in FIG. 26a. However, in shielded electrical cable
4902, cover portion 4908''' of shielding film 4908 covers the
bottom side of conductor set 4904. Cover portion 4946''' of carrier
film 4946 covers the top side and the entire left and right sides
of conductor set 4904, completing the enclosure of conductor set
4904. In this embodiment, parallel portions 4908'' and cover
portion 4908''' of shielding film 4908 are substantially
coplanar.
[0113] Similar to embodiments of the shielded electrical cable
including two generally parallel shielding films disposed around a
conductor set or around a plurality of spaced apart conductor sets,
embodiments of the shielded electrical cable including a single
shielding film may include at least one longitudinal ground
conductor. In one aspect, this ground conductor facilitates
electrical contact of the shielding film to any suitable individual
contact element of any suitable termination point, such as, e.g., a
contact element on a printed circuit board or an electrical contact
of an electrical connector. The ground conductor may extend beyond
at least one of the ends of the shielding film to facilitate this
electrical contact. The ground conductor may make direct or
indirect electrical contact with the shielding film in at least one
location along its length, and may be placed in suitable locations
of the shielded electrical cable.
[0114] FIG. 27 is specifically intended to illustrates exemplary
locations of a ground conductor in a shielded electrical cable
according to an aspect of the present invention. Shielded
electrical cable 5002 is similar to shielded electrical cable 4402
described above and illustrated in FIG. 24, but includes ground
conductors 5012 in various exemplary locations. Ground conductors
5012 extend in substantially the same direction as insulated
conductors 5006 of conductor sets 5004 and are positioned between
shielding film 5008 and carrier film 5046. One ground conductor
5012 is included in a parallel portion 5008'' of shielding film
5008 and three ground conductors 5012 are included in a conductor
set 5004. One of these three ground conductors 5012 is positioned
between insulated conductors 5006 and shielding film 5008 and two
of these three ground conductors 5012 and insulated conductors 5006
are arranged generally in a single plane.
[0115] FIGS. 28a-28d illustrate various exemplary embodiments of a
shielded electrical cable according to aspects of the present
invention. FIGS. 28a-28d are specifically intended to illustrate
various examples of partial coverage of the conductor set by the
shielding film without the presence of a carrier film. The amount
of coverage by the shielding film varies between the embodiments.
In the embodiment illustrated in FIG. 28a, the conductor set has
the most coverage. In the embodiment illustrated in FIG. 28d, the
conductor set has the least coverage. In the embodiments
illustrated in FIGS. 28a and 28b, more than half of the periphery
of the conductor set is covered by the shielding film. In the
embodiment illustrated in FIG. 28c, about half of the periphery of
the conductor set is covered by the shielding film. In the
embodiment illustrated in FIG. 28d, less than half of the periphery
of the conductor set is covered by the shielding film. A greater
amount of coverage provides better electromagnetic interference
(EMI) isolation and reduced signal attenuation (resulting from a
reduction in the proximity effect). Although in these embodiments,
a conductor set includes two substantially parallel longitudinal
insulated conductors, in other embodiments, a conductor set may
include one or more than two substantially parallel longitudinal
insulated conductors.
[0116] Referring to FIG. 28a, shielded electrical cable 5102
includes a conductor set 5104 and a shielding film 5108. Conductor
set 5104 includes two longitudinal insulated conductors 5106.
Shielding film 5108 includes parallel portions 5108'' extending
from both sides of conductor set 5104. Parallel portions 5108''
cooperatively define a generally planar shielding film. Shielding
film 5108 further includes a cover portion 5108''' partially
covering conductor set 5104. Cover portion 5108''' includes
concentric portions 5108' substantially concentric with
corresponding conductor 5106. Cover portion 5108''' of shielding
film 5108 covers the bottom side and the entire left and right
sides of conductor set 5104.
[0117] Referring to FIG. 28b, shielded electrical cable 5202 is
similar to shielded electrical cable 5102 described above and
illustrated in FIG. 28a. However, in shielded electrical cable
5202, cover portion 5208''' of shielding film 5208 covers the
bottom side and more than half of the left and right sides of
conductor set 5204.
[0118] Referring to FIG. 28c, shielded electrical cable 5302 is
similar to shielded electrical cable 5102 described above and
illustrated in FIG. 28a. However, in shielded electrical cable
5302, cover portion 5308''' of shielding film 5308 covers the
bottom side and about half of the left and right sides of conductor
set 5304.
[0119] Referring to FIG. 28d, shielded electrical cable 5402 is
similar to shielded electrical cable 5102 described above and
illustrated in FIG. 28a. However, in shielded electrical cable
5402, cover portion 5408''' of shielding film 5408 covers the
bottom side and less than half of the left and right sides of
conductor set 5404.
[0120] As an alternative to a carrier film, for example, shielded
electrical cables according to aspects of the present invention may
include an optional non-conductive support. This support may be
used to complete physical coverage of a conductor set and add to
the mechanical stability of the shielded electrical cable. FIGS.
29a-29d illustrate various exemplary embodiments of a shielded
electrical cable according to aspects of the present invention
including a non-conductive support. Although in these embodiments,
a non-conductive support is used with a conductor set that includes
two substantially parallel longitudinal insulated conductors, in
other embodiments, a non-conductive support may be used with a
conductor set that includes one or more than two substantially
parallel longitudinal insulated conductors, or with a ground
conductor. The support may include any suitable polymeric material,
including but not limited to polyester, polyimide, polyamide-imide,
polytetrafluoroethylene, polypropylene, polyethylene, polyphenylene
sulfide, polyethylene naphthalate, polycarbonate, silicone rubber,
ethylene propylene diene rubber, polyurethane, acrylates,
silicones, natural rubber, epoxies, and synthetic rubber adhesive.
The support may include one or more additives and/or fillers to
provide properties suitable for the intended application.
[0121] Referring to FIG. 29a, shielded electrical cable 5502 is
similar to shielded electrical cable 5102 described above and
illustrated in FIG. 28a, but further includes a non-conductive
support 5548 partially covering conductor set 5504 opposite cover
portion 5508''' of shielding film 5508. Support 5548 covers
essentially the entire top side of conductor set 5504, essentially
fully enclosing insulated conductors 5506. Support 5548 includes a
generally planar top surface 5548a. Top surface 5548a and parallel
portions 5508'' are substantially coplanar.
[0122] Referring to FIG. 29b, shielded electrical cable 5602 is
similar to shielded electrical cable 5202 described above and
illustrated in FIG. 28b, but further includes a non-conductive
support 5648 partially covering conductor set 5604 opposite cover
portion 5608''' of shielding film 5608. Support 5648 only partially
covers the top side of conductor set 5604, leaving insulated
conductors 5606 partially exposed.
[0123] Referring to FIG. 29c, shielded electrical cable 5702 is
similar to shielded electrical cable 5302 described above and
illustrated in FIG. 28c, but further includes a non-conductive
support 5748 partially covering conductor set 5704 opposite cover
portion 5708''' of shielding film 5708. Support 5748 covers
essentially the entire top side of conductor set 5704, essentially
fully enclosing insulated conductors 5706. At least a portion of
support 5748 is substantially concentric with insulated conductors
5706. A portion of support 5748 is disposed between insulated
conductors 5706 and shielding film 5708.
[0124] Referring to FIG. 29d, shielded electrical cable 5802 is
similar to shielded electrical cable 5402 described above and
illustrated in FIG. 28d, but further includes a non-conductive
support 5848 partially covering conductor set 5804 opposite cover
portion 5808''' of shielding film 5808. Support 5848 only partially
covers the top side of conductor set 5804, leaving insulated
conductors 5806 partially exposed. A portion of support 5848 is
disposed between insulated conductors 5806 and shielding film
5808.
[0125] The following items are exemplary embodiments of a shielded
electrical cable according to aspects of the present invention.
[0126] Item 1 is a shielded electrical cable comprising a conductor
set including one or more substantially parallel longitudinal
insulated conductors; and a shielding film including a cover
portion partially covering the conductor set, and parallel portions
extending from both sides of the conductor set.
[0127] Item 2 is the shielded electrical cable of item 1, wherein
the parallel portions cooperatively define a generally planar
shielding film.
[0128] Item 3 is the shielded electrical cable of item 1, wherein
the cover portion includes a concentric portion substantially
concentric with at least one of the conductors.
[0129] Item 4 is the shielded electrical cable of item 1 further
comprising a non-conductive carrier film including a cover portion
partially covering the conductor set opposite the cover portion of
the shielding film, and parallel portions extending from both sides
of the conductor set and disposed opposite the parallel portions of
the shielding film.
[0130] Item 5 is the shielded electrical cable of item 4, wherein
the cover portion of the carrier film includes a concentric portion
substantially concentric with at least one of the conductors.
[0131] Item 6 is the shielded electrical cable of item 1 further
comprising at least one longitudinal ground conductor extending in
substantially the same direction as the one or more insulated
conductors.
[0132] Item 7 is the shielded electrical cable of item 6, wherein
the ground conductor makes direct electrical contact with the
shielding film in at least one location along its length.
[0133] Item 8 is the shielded electrical cable of item 6, wherein
the ground conductor makes indirect electrical contact with the
shielding film in at least one location along its length.
[0134] Item 9 is the shielded electrical cable of item 6, wherein
the ground conductor extends beyond at least one of the ends of the
shielding film.
[0135] Item 10 is the shielded electrical cable of item 6, wherein
the ground conductor is included in the conductor set.
[0136] Item 11 is the shielded electrical cable of item 6, wherein
the ground conductor is included in the parallel portion.
[0137] Item 12 is the shielded electrical cable of item 1, wherein
the conductor set and shielding film are cooperatively configured
in an impedance controlling relationship.
[0138] Item 13 is the shielded electrical cable of item 1 further
comprising a non-conductive support partially covering the
conductor set opposite the cover portion of the shielding film.
[0139] Item 14 is the shielded electrical cable of item 13, wherein
the support includes a concentric portion substantially concentric
with at least one of the conductors.
[0140] Item 15 is a shielded electrical cable comprising a
plurality of spaced apart conductor sets arranged generally in a
single plane, each conductor set including one or more
substantially parallel longitudinal insulated conductors; and a
shielding film including a plurality of cover portions partially
covering the conductor sets, and a parallel portion disposed
between adjacent conductor sets and configured to electrically
isolate the adjacent conductor sets from each other.
[0141] Item 16 is the shielded electrical cable of item 15, wherein
the parallel portion is positioned at a depth that is greater than
about one third of the diameter of the insulated conductors.
[0142] Item 17 is the shielded electrical cable of item 15, wherein
the parallel portion is positioned at a depth that is greater than
about one half of the diameter of the insulated conductors.
[0143] Although specific embodiments have been illustrated and
described herein for purposes of description of the preferred
embodiment, it will be appreciated by those of ordinary skill in
the art that a wide variety of alternate and/or equivalent
implementations calculated to achieve the same purposes may be
substituted for the specific embodiments shown and described
without departing from the scope of the present invention. Those
with skill in the mechanical, electro-mechanical, and electrical
arts will readily appreciate that the present invention may be
implemented in a very wide variety of embodiments. This application
is intended to cover any adaptations or variations of the preferred
embodiments discussed herein. Therefore, it is manifestly intended
that this invention be limited only by the claims and the
equivalents thereof.
* * * * *