U.S. patent application number 16/256094 was filed with the patent office on 2019-07-25 for shielding tape with features for mitigating micro-fractures and the effects thereof.
This patent application is currently assigned to PCT International, Inc.. The applicant listed for this patent is PCT International, Inc.. Invention is credited to Walter B. Melton, Leonard Visser, Timothy L. Youtsey.
Application Number | 20190228878 16/256094 |
Document ID | / |
Family ID | 67300109 |
Filed Date | 2019-07-25 |
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United States Patent
Application |
20190228878 |
Kind Code |
A1 |
Visser; Leonard ; et
al. |
July 25, 2019 |
Shielding Tape With Features For Mitigating Micro-Fractures And The
Effects Thereof
Abstract
In an electronic cable, a shielding tape prevents and mitigates
the creation and propagation of micro-fractures and the deleterious
effects thereof. In some embodiments, the shielding tape has layers
which are oriented in a non-zero transverse relation with respect
to each other, or have been treated to have non-zero orientations.
Other embodiments include micro-fracture propagation mitigation
means, such as perforations, ridges, waffling, and dimpling. In
some embodiments, the layers of the shielding tape are bonded to
each other with an electrically-conductive elastomeric adhesive. In
other embodiments, the shielding tape is wrapped around a cable's
dielectric and form an overlap gap, which is filled by an
electrically-conductive elastomeric adhesive.
Inventors: |
Visser; Leonard;
(Huntsville, AR) ; Youtsey; Timothy L.; (Tempe,
AZ) ; Melton; Walter B.; (Glendale, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PCT International, Inc. |
Mesa |
AZ |
US |
|
|
Assignee: |
PCT International, Inc.
Mesa
AZ
|
Family ID: |
67300109 |
Appl. No.: |
16/256094 |
Filed: |
January 24, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62621901 |
Jan 25, 2018 |
|
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62621905 |
Jan 25, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01B 11/1008 20130101;
H01B 7/1895 20130101; H05K 9/0098 20130101; H01B 7/22 20130101 |
International
Class: |
H01B 7/22 20060101
H01B007/22; H01B 7/18 20060101 H01B007/18 |
Claims
1. Shielding tape in an electronic cable, the shielding tape
comprising: a metallic layer; and micro-fracture propagation
mitigation means formed in the metallic layer.
2. The shielding tape of claim 1, wherein the micro-fracture
propagation mitigations means includes perforations formed through
the metallic layer.
3. The shielding tape of claim 2, wherein the perforations have a
major dimension smaller than approximately 12 millimeters.
4. The shielding tape of claim 3, wherein the major dimension is
smaller than approximately 3 millimeters.
5. The shielding tape of claim 2, wherein the perforations are
spaced apart in an array across the metallic layer.
6. The shielding tape of claim 5, wherein the perforations have a
major dimension smaller than approximately 12 millimeters and are
spaced apart from each other in the array by at least the major
dimension.
7. The shielding tape of claim 6, wherein the major dimension is
smaller than approximately 3 millimeters.
8. The shielding tape of claim 1, wherein the micro-fracture
propagation mitigations means includes ridges formed in the
metallic layer.
9. The shielding tape of claim 8, wherein: each ridge in the
metallic layer comprises a first wall and a second wall arranged
obliquely with respect to the first wall; and the first and second
walls each project into and out of a plane along which the metallic
layer extends.
10. The shielding tape of claim 1, wherein the micro-fracture
propagation mitigations means includes waffling formed in the
metallic layer.
11. The shielding tape of claim 10, wherein the waffling is formed
by intersecting ridges on the metallic layer spaced apart by
depressions between the ridges.
12. The shielding tape of claim 1, wherein the micro-fracture
propagation mitigations means includes dimpling formed in the
metallic layer.
13. The shielding tape of claim 12, wherein the dimpling is formed
by semi-spherical concave depressions into the layer.
14. The shielding tape of claim 13, wherein the concave depressions
are spaced apart in an array across the metallic layer.
15. The shielding tape of claim 14, wherein the concave depressions
each have a major dimension, and the concave depressions are spaced
apart from each other in the array by at least the major
dimension.
16. Shielding tape in an electronic cable, the shielding tape
comprising: a first metallic layer having a first orientation along
which micro-fractures are predisposed to form; a second metallic
layer having a second orientation along which micro-fractures are
predisposed to form; and the first and second orientations have a
non-zero transverse relation with respect to each other.
17. The shielding tape of claim 16, wherein the first and second
orientations in the first and second metallic layers are formed by
burnishing the first and second metallic layers.
18. The shielding tape of claim 16, wherein the first metallic
layer is arranged with a non-zero transverse orientation with
respect to the second metallic layer.
19. Shielding tape in an electronic cable, the shielding tape
comprising: a first layer; a second layer; an adhesive disposed
between the first and second layers; and metallic solids dispersed
throughout the adhesive, defining the adhesive with electrically
conductive material characteristics.
20. The shielding tape of claim 19, wherein the adhesive is an
elastomeric adhesive.
21. An electronic cable comprising: a conductor; an insulator
surrounding the conductor; shielding tape wrapped around the
insulator, the shielding tape having overlapping edges forming an
overlap gap therebetween; an adhesive disposed in the overlap gap;
and metallic solids dispersed throughout the adhesive, defining the
adhesive with electrically conductive material characteristics.
22. The cable of claim 21, wherein the adhesive is an elastomeric
adhesive.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/621,901, filed Jan. 25, 2018, and it also claims
the benefit of U.S. Provisional Application No. 62/621,905, filed
Jan. 25, 2018, both of which are hereby incorporated by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to electronic
devices, and more particularly to shielding tape used in various
cabled communication products including coaxial cable, HDMI cable,
power cords, Ethernet cables, and other electronic cables and
devices.
BACKGROUND OF THE INVENTION
[0003] Electronic devices and components used in and around homes
and businesses produce ingress noise affecting radio-frequency
("RF") signals transmitted through nearby coaxial cables. Ingress
noise can be caused by manufacturing or installation defects, by
imperfections in various electronic devices or components or
electronic cables, and by poor or inadequate shielding.
Conventional shielding that may have once been adequate is becoming
less and less effective with the continuing proliferation of
electronic devices. Communication in the 5G band creates
particularly insidious noise issues. Ingress noise has become a
serious problem impacting signal quality in television, voice,
security, and broadband services.
[0004] Shielding is used in a variety of electronic cables and
devices to reduce outside electrical interference or noise that
could affect an RF signal travelling through the cable or other
device. The shielding also helps prevent the signal from radiating
from the cable or other device and then interfering with other
devices.
[0005] Conventionally, one type of shielding includes two or three
shielding layers of aluminum or other shielding material (such as
silver, copper, or Mu-metal) wherein each shielding layer of a
laminated assembly is separated by a separating layer, such as a
plastic, e.g., polyethylene terephthalate ("PET"), or a polyolefin
such as polypropylene ("PP"). This type of shielding that combines
layers of shielding material and separating layers is often
referred to as either "foil," "laminated tape," "shielding tape,"
"shielding laminate tape," "laminated shielding tape" (LST), and
combinations or variations thereof. In some cables, such as coaxial
cables, multiple layers of shielding tape (each of which has one or
more shielding layers) are employed in the cable. For example,
"tri-shield" cables include an inner foil surrounded by a braid,
which is in turn surrounded by an outer foil. "Quad-shield" cables
include an inner foil surrounded by an inner braid, which is in
turn surrounded by an outer foil, in turn surrounded by an outer
braid.
[0006] Multiple layers of shielding tape, while providing better
shielding performance, also add to the cost and complexity of
producing the cabling. Conventional shielding tape, with only one
or two shielding layers, is susceptible to the formation of
micro-fractures or micro-cracks as the cable bends and flexes over
time. Such micro-fractures are shown in FIGS. 1A and 1B.
Micro-fractures may also be caused by the application of heat and
stress to shielding tape, during the manufacturing process of a
coaxial cable, as the tape is bonded to or applied over inner
components of the cable such as the dielectric material. These
micro-fractures and micro-cracks will allow RF signal ingress and
egress. A way to mitigate the formation of the micro-fractures and
micro-cracks, or a way to mitigate their effects, is needed.
SUMMARY OF THE INVENTION
[0007] In an electronic cable, a shielding tape prevents and
mitigates the creation and propagation of micro-fractures and the
deleterious effects thereof. In some embodiments, the shielding
tape has layers which are oriented in a non-zero transverse
relation with respect to each other, or have been treated to have
non-zero orientations. Other embodiments include micro-fracture
propagation mitigation means, such as perforations, ridges,
waffling, and dimpling. In some embodiments, the layers of the
shielding tape are bonded to each other with an
electrically-conductive elastomeric adhesive. In other embodiments,
the shielding tape is wrapped around a cable's dielectric and form
an overlap gap, which is filled by an electrically-conductive or
elastomeric adhesive.
[0008] The above provides the reader with a very brief summary of
some embodiments discussed below. Simplifications and omissions are
made, and the summary is not intended to limit or define in any way
the scope of the invention or key aspects thereof. Rather, this
brief summary merely introduces the reader to some aspects of the
invention in preparation for the detailed description that
follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Referring to the drawings:
[0010] FIGS. 1A and 1B are photographs of micro-fractures in
electronic cables;
[0011] FIG. 1C is an electronic cable with a shielding tape;
[0012] FIG. 2A is a diagram of two layers of conventional shielding
tape, illustrating RF noise egress through micro-fractures;
[0013] FIG. 2B is a diagram of two layers of a shielding tape,
illustrating mitigation of RF noise egress through
micro-fractures;
[0014] FIG. 3 is a diagram of two layers of a shielding tape,
illustrating mitigation of RF noise egress through
micro-fractures;
[0015] FIGS. 4A and 4B are diagrams of two bonded layers of
conventional shielding tape, illustrating RF noise egress through
micro-fractures;
[0016] FIGS. 4C and 4D are diagrams of two elastomerically bonded
layers of shielding tape, illustrating the prevention of RF noise
egress;
[0017] FIGS. 4E and 4F are diagrams of two elastomerically bonded
layers of shielding tape, illustrating the prevention of RF noise
egress;
[0018] FIGS. 5A and 5B are diagrams of layers of shielding tape, at
least one of which is formed with micro-perforations;
[0019] FIGS. 6A and 6B are diagrams of a layer of conventional
shielding tape developing micro-fractures when placed under
stress;
[0020] FIGS. 6C and 6D are diagrams of a layer of shielding tape
with ridges, preventing the development of micro-fractures when
placed under stress;
[0021] FIGS. 6E and 6F are diagrams of a layer of shielding tape
with waffling, preventing the development of micro-fractures when
placed under stress;
[0022] FIGS. 6G and 6H are diagrams of a layer of shielding tape
with dimpling, preventing the development of micro-fractures when
placed under stress;
[0023] FIG. 7A is a diagram of layers of shielding tape with
electrically-conductive adhesive disposed between the layers;
and
[0024] FIGS. 7B and 7C are section and detailed views of a coaxial
cable, showing electrically-conductive adhesive disposed within an
overlap gap in shielding tape.
DETAILED DESCRIPTION
[0025] Reference now is made to the drawings, in which the same
reference characters are used throughout the different figures to
designate the same elements. FIGS. 1A and 1B are optical microscope
photographs showing micro-fractures 10 formed through a shielding
tape. These micro-fractures 10 are elongate, longer than they are
wide. Micro-fractures such as these allow RF ingress and
egress.
[0026] FIG. 2A illustrates conventional laminated tape construction
techniques which might lead to the creation of such micro-fractures
10. FIG. 2A shows two laminated tape layers 11 and 12. The layer 11
is an inner layer and the layer 12 is an outer layer; the outer
layer 12 surrounds the inner layer 11. Though one having ordinary
skill in the art should understand, discussion of conventional
coaxial cable construction is discussed here for the purpose of
context. This discussion is not meant to limit this entire
disclosure to coaxial cables; indeed, this disclosure applies to
other types of electronic cables and cords as suitable. Generally,
most conventional coaxial cables have a center conductor surrounded
by a cylindrical dielectric. The dielectric is then encircled by
the shielding tape, which may include a foil layer, a laminated
shielding tape layer, a braided layer, or a combination thereof.
Finally, an insulating jacket--generally a PVC jacket--surrounds
the entire assembly.
[0027] The layers 11 and 12 are two layers of the shielding tape in
such a conventional coaxial cable. During the manufacturing
processes of these layers 11 and 12, rolling and stretching of the
metal of the layers 11 and 12 results in a generally longitudinal
crystal orientation. If micro-fractures later develop in the layers
11 and 12, such micro-fractures tend to be likewise oriented
longitudinally. Wrapping the layers 11 and 12 onto the cable can
create or enlarge the micro-fractures. FIG. 2A shows two set of
micro-fractures 13 and 14 formed in the layers 11 and 12.
[0028] Frequently, micro-fractures propagate through the components
of a shielding tape. This is what has occurred in FIG. 2A; it can
be seen that the micro-fractures 13 and 14 are registered with each
other. When the center conductor within the cable generates egress
noise (indicated throughout these drawings by the reference
character N), the noise N can pass through the micro-fractures 13
in the inner layer 11. When the micro-fractures 13 and 14 in both
layers 11 and 12 are registered with each other, however, the noise
N will pass not only through the layer 11, but also through the
layer 12, thereby transmitting outside of the cable. It is noted
that while the drawings generally show egress noise N as a set of
arrowed lines extending out of the cable, the micro-fractures are
also vulnerable to ingress noise. Ingress noise is not specifically
discussed or shown here, but one having ordinary skill in the art
will appreciate that it behaves similarly to egress noise N with
respect to transmission through micro-fractures.
[0029] FIG. 1C illustrates a coaxial cable 110 constructed with
shielding tape that prevents and mitigates the formation and
propagation of micro-fractures and also prevents and mitigates the
deleterious effects of RF signal ingress and egress through such
micro-fractures. The cable 110 has a center conductor 111, an
insulating dielectric 112 surrounding the conductor 111, a
shielding tape 113 with these mitigation features, a flexible braid
114 encircling the shielding tape 113, and an insulative jacket 115
surrounding everything.
[0030] The below construction methods, features, techniques, and
structures apply to the shielding tape 113, mitigate micro-fracture
formation and propagation, and also minimize RF signal ingress and
egress. In general, improved shielding tapes are described which
reduce the incidence, enlargement, and propagation of
micro-fractures and micro-tears that often result from bending and
flexing of cables and other devices. This not only reduces signal
egress or ingress but also improves the flex life of the shielding
tape, maintains electrical continuity, and minimizes performance
degradation of the cable or other device over time. Furthermore,
outer shielding structures, such as braids, may be eliminated,
thereby eliminating the need to remove such structures when
attaching a connector to the cable, and eliminating problems
associated with outer shielding structures separating and
interfering with connector attachment.
[0031] FIG. 2B illustrates a construction technique which prevents
the development of registered micro-fractures in the shielding tape
used for shielding, and/or reduces the incidence of
micro-fractures, and minimizes the dimensions of micro-fractures.
The shielding tape shown in FIG. 2B is constructed with two
separate metallic layers 20 and 21 in which some of the aluminum
crystal orientation of one or more of the adjoining aluminum layers
is at least partially biased by a surface treatment such as
burnishing. It is briefly noted here that "aluminum laminate" is
sometimes used in this description to identify the shielding tape
because aluminum is a common material choice for the shielding
foil.
[0032] FIG. 2B shows micro-fractures 22 and 23 formed in the layers
20 and 21, respectively. As can be seen, the micro-fractures 22 and
23 are oriented transversely with respect to each other. This is
because the layers 20 and 21 have been burnished differently.
Burnishing is the process of rubbing or smoothing the layers 20 and
21 in a certain direction by repeatedly sliding a hard object
tangentially in contact against the layers 20 and 21. As burnishing
continues, the crystals in the layers 20 and 21 orient themselves
consistently. This helps ensure that if a micro-fracture develops,
it will develop along the orientation of the crystals. In other
words, when the crystals have acquired a consistent orientation the
micro-fractures are predisposed to form along that particular
orientation.
[0033] The inner layer 20 is burnished in a first direction
arranging the crystals into a first orientation (horizontal on the
page), and the outer layer 21 is burnished in a second direction
arranging the crystals into a second orientation (vertical on the
page). FIG. 2B shows the first and second orientations generally as
the direction of the micro-fractures 22 and 23, which are
perpendicular to each other. While a perpendicular orientation may
be preferable, any non-zero transverse relation is suitable. When
the metallic layers 20 and 21 are joined to each other (preferably
with laminate between) during manufacturing to form the shielding
tape for application to the cable, the micro-fractures 22 and 23
are offset; they have a non-zero transverse orientation with
respect to each other. Therefore, longitudinal tears are less
likely to register with or near each other, and are thus more
likely to form only small holes through the shielding tape rather
than long tears. In other words, overlapping micro-fractures 22 and
23 in adjacent layers 20 and 21 form small holes rather than tears,
and small holes allow less RF egress noise N to be emitted than do
long tears.
[0034] While the construction technique shown in FIG. 2B does not
necessarily reduce the incidence of micro-fractures, it does reduce
the transmission of egress noise N by orienting the micro-fractures
in an offset fashion. RF ingress and egress through the
micro-fractures 22 and 23 is thus minimized, and shielding
effectiveness is maintained despite the presence of the
micro-fractures 22 and 23 in the individual layers 20 and 21.
[0035] FIG. 3 illustrates another shielding tape construction
technique. Two metallic layers 30 and 31 of the shielding tape each
have opposed ends 32 and 33 and opposed sides 34 and 35. They also
have a similar aluminum crystal orientation, namely, between the
sides 34 and 35. This crystal orientation is created by burnishing
or some other technique. The known consistent orientation of
aluminum crystals is exploited to mitigate egress noise N
transmission. Before the metallic layers 30 and 31 are joined to
form the shielding tape, one of the layers 30 or 31 is rotated with
respect to the other. FIG. 3B shows the outer layer 31 offset and
generally perpendicular to the inner layer 30. While a
perpendicular offset orientation may be preferable, any non-zero
transverse relation is suitable. The layers 30 and 31 are then
joined.
[0036] By offsetting or orienting the layers 30 and 31 transversely
with respect to each other, shielding loss from micro-fractures is
minimized. While the micro-fractures 36 and 37 may overlap with
each other, they do not register, and so they can only form small
holes rather than long tears. Laminating two or more such layers 30
and 31, one of which has been physically offset at any non-zero
angle up to and including ninety degrees prior to lamination,
minimizes the dimensions of the opening through which any RF
ingress or egress can occur and thereby reduces the potential for
RF signal ingress or egress through a micro-fracture of the
aluminum layer.
[0037] In another method, each layer of the shielding tape is
annealed prior to lamination. Under appropriate annealing
procedures, aluminum crystal grain size is reduced and orientation
of the crystals is randomized. If micro-fractures later occur in
the presence of smaller grains and randomized crystal orientation,
such micro-fractures are less likely to be parallel with or
coterminous with a micro-fracture in an adjoining layer. Thus, a
channel through which any ingress or egress noise must penetrate,
if any such channel exists, is greatly reduced in size. Shielding
from RF signal ingress or egress is thereby preserved.
[0038] Conventionally, the components of the shielding tape 40 are
joined to each other with a non-elastomeric adhesive, as shown in
FIG. 4A. When a stress is applied on the shielding tape 40, such as
a shear stress 41, micro-fractures 42 will develop in one or both
of the layers, and egress noise N will transmit through these
micro-fractures 42.
[0039] FIGS. 4C and 4D show three laminated layers 50, 51, and 52
of a shielding tape with an adhesive 53 disposed therebetween. The
adhesive 53 has elastomeric properties and thus permits flexing
without the consequential forming of micro-fractures in the layers
50, 51, or 52. The elasticity of the adhesive 53 reduces the
transmission from one layer to another of the stresses caused by
bending or flexing, thereby decreasing the likelihood of the
development of a micro-fracture. But, if such a micro-fracture does
occur in one aluminum layer despite the elasticity of the bonding
adhesive, there is less likelihood that parallel or coterminous
micro-fractures will propagate or develop in the adjoining layers,
and there is a greater likelihood that any micro-fracture present
in one layer will be covered by or adjacent to an undamaged segment
of the adjacent layer.
[0040] The adhesive 53 is applied across the entire surface of each
layer 50, 51, and 52, so that bonding between two adjacent layers
is made across the entirety of abutting surfaces. The shielding
tape is constructed in this fashion and is then wrapped around the
cable. While FIG. 4D does illustrates three layers 50, 51, and 52,
it is noted that a greater or lesser number of layers may be used,
depending on factors such as the performance specifications, design
constrictions, and budget of the manufacturer.
[0041] FIGS. 4E and 4F show an alternate embodiment of elastomeric
bonding. There, the shielding tape is still constructed from three
layers 50, 51, and 52, but the adhesive 53 is applied differently.
The layers 50, 51, and 52 each have opposed ends 54 and 55 and
opposed sides 56 and 57. The adhesive 53, rather than being applied
across an entire face of the layer, is only applied along the sides
56 and 57. No adhesive 53 is applied between the sides 56 and 57.
In some embodiments, adhesive 53 is applied along the opposed ends
55 and 56.
[0042] In applications involving coaxial cable, the shielding tape
is commonly manufactured in long strips, so in this particular
application the bonding adhesive is preferably applied only along
the longitudinal sides 56 and 57 of the layers 50, 51 and 52.
Flexibility of unbonded sections of the layers 50, 51, and 52,
between the sides 56 and 57, provides a measure of stress relief
that reduces the likelihood of micro-fracture development in the
layers 50, 51, and 52. FIGS. 4E and 4F show the application of the
bonding adhesive only along the sides 56 and 57 of the layers 50,
51, and 52. When the shear stress 41 is applied, micro-fractures do
not develop. Other patterns of adhesive placement may be suitable
or preferable in some applications.
[0043] The above construction techniques mitigate the effects of
micro-fracture incidence and propagation. Other construction
techniques directly mitigate the incidence and propagation of
micro-fractures. These micro-fracture propagation mitigation means
or features are formed in the metallic layer of the shielding and
include perforations or micro-perforations (FIGS. 5A and 5B),
ridges (FIGS. 6C and 6D), waffling (FIGS. 6E and 6F), and dimpling
(FIGS. 6G and 6H).
[0044] One such means of reducing the incidence of micro-fractures
is with the use of an array of perforations or micro-perforations,
as shown in FIGS. 5A and 5B, which show a shielding tape 60 under
no stress and under shear stress 41. In this embodiment, an array
of micro-perforations 61 is applied to one or more layers 62, 63,
or 64 of the shielding tape 60. Such micro-perforations 61 in a
layer alleviate any stresses present and decreases the likelihood
that any such stresses will cause a micro-fracture. Moreover, where
stresses do cause a micro-fracture, such micro-perforations 61
prevent and limit further expansion of the micro-fractures beyond
the micro-perforation 61. The micro-perforations thus act as a stop
to migration or extension of micro-fractures across more of the
affected layer.
[0045] The micro-perforations 61 have a major dimension, which is
the longest distance between two edges of a micro-perforation. The
major dimension is smaller in dimension than the amplitude of the
wavelength of the RF signal to be carried by the particular cable
in which the shielding tape 60 is to be used. Thus, RF signals
cannot pass through any one of the intact micro-perforations 61.
Indeed, ingress or egress of noise from desired RF signals through
a micro-perforation 61 can only occur in the event that there is a
tear at a micro-perforation. Even then, the noise ingress or egress
can only pass entirely through the shielding tap 60 if the adjacent
layers have also been torn at micro-perforations 61 which are
registered with the torn micro-perforation 61.
[0046] Because the micro-perforations 61 are very small, any
ingress or egress of RF signals through the micro-perforations 61
is limited to much higher frequencies and smaller wavelengths than
might otherwise leak through a larger micro-fracture. Moreover,
noise ingress would be from RF signals different in wavelength from
those transmitted through the cable. In other words, use of an
array of micro-perforations 61 is especially suitable in
applications where ingress or egress of higher frequency range RF
signals is not a significant consideration and can be
tolerated.
[0047] The shielding tape 60 shown in FIGS. 5A and 5B includes an
array of micro-perforations 61 in which the micro-perforations 61
are arranged in rows, and the micro-perforations 61 in each row are
offset horizontally from those in the row above and below. The
micro-perforations 61 preferably have a circular shape, with their
major dimension being the diameter of that circular shape, but in
other embodiments may have other shapes whose major dimension is
smaller than the wavelength of the RF noise, especially of RF noise
in the 5G spectrum. Preferably, the major dimension is smaller than
approximately 12 millimeters to mitigate RF frequencies around 24
GHz. More preferably, the major dimension is smaller than
approximately 3.5 millimeters to mitigate RF frequencies around 86
GHz. Still more preferably, the major dimension is smaller than
approximately 3 millimeters to mitigate RF frequencies around 95
GHz. In the array, the micro-perforations 61 are preferably spaced
apart by at least the major dimension.
[0048] As can be seen in FIGS. 5A and 5B, the shielding tape 60 not
only has the micro-perforations 61, but its layers 62, 63, and 64
are joined by the elastomeric adhesive 53. When the shear stress 41
is applied, the layers 62, 63, and 64 stretch along the direction
of the shear stress 41, the adhesive 53 elastically deforms, and
the micro-perforations 61 deform to acquire an elongated shape.
When the shear stress 41 is released, the micro-perforations return
to their original shape, as in FIG. 5A.
[0049] FIGS. 6A and 6B show a conventional laminated layer 70, both
under no stress and under shear stress 41. As has been discussed,
when a laminated layer 70 is placed under shear stress 41,
micro-fractures 71 will develop, generally transverse to the
direction of the shear stress 41. This allows egress noise N to
transmit through the layer 70. Various methods of treating,
aligning, orienting, and bonding layers has been discussed. The
layers can also be textured in different ways.
[0050] FIGS. 6C and 6D illustrate a single laminated metallic layer
73 of shielding tape, where the layer has a texture. The layer 73
is formed with a plurality of corrugations or ridges 74. The layer
73 has opposed ends 75 and 76 and opposed sides 77 and 78.
Generally, the layer 73 is aligned along a plane P extending
between the ends 75 and 76 and between the sides 77 and 78. The
ridges 74, extending between the sides 77 and 78, project into and
out of that plane. Each ridge 74 has a first wall 80 and a second
wall 81, meeting at a hinge point 82 therebetween. The first and
second walls 80 and 81 are generally straight and flat and oriented
obliquely with respect to each other. The layer 73 has a dimension
A between the opposed ends 75 and 76. When the layer 73 is placed
under the shear stress 41, the layer 73 acquires a new dimension
A'. Generally, because that shear stress 41 will be positive to act
to extend the layer 73, the dimension A' is greater than the
dimension A. However, in some cases, the shear stress 41 will be
negative and will cause the ends 75 and 76 to collapse toward each
other, in which case the dimension A' will be less than the
dimension A. When the layer 73 is under a positive shear stress 41,
the ridges 74 respond by flattening and lengthening. This
accommodates the effect of the shear stress 41 to stretch the layer
73. Without such accommodation, the layer 73 would tend to tear and
develop micro-fractures. In other words, the ridges 74 prevent or
mitigate the development of micro-fractures.
[0051] The layer 73 is suitable for use as the sole layer in a
shielding tape, or it may be used without similar layers 73, or
with other different layers discussed herein, in different
orientations described herein and with different surface treatments
described herein.
[0052] FIGS. 6E and 6F show a metallic layer 84 of a shielding tape
with waffling 85 formed by intersecting ridges 86 separated and
spaced apart by depressions 87. The ridges 86 are oriented normally
with respect to a plane in which the layer 84 lies, and there are
two sets of ridges 86: one set which is aligned vertically, or
end-to-end, and another set which is aligned horizontally, or
side-to-side, so that the two sets of ridges are transverse and
preferably perpendicular with respect to each other across both
sides of the layer 84. The ridges 86 project normally to the layer
84, both in front of and behind the layer 84, and the depressions
87 are disposed between the ridges 86.
[0053] The ridges 86 are reinforced portions of the layer 84,
representing a thickened portion of the layer 84, while the
depressions 87 are "thinned" portions, in that they are thinner
than the ridges 86, but are still generally as thick as the other
layers, such as layers 50, 51, 52, 70, etc. When the shear stress
is applied to the layer 84 and it stretches, the ridges 86 respond
by stretching slightly, and the depressions 87 respond by
stretching slightly. Should a micro-fracture occur, it generally
forms in the thinned area of a depression 87, and it is limited to
the depression 87 in which it forms; it is unlikely to propagate
through a ridge 86 to an adjacent depression 87. As such, the layer
84 prevents and mitigates the development of micro-fractures.
[0054] The layer 84 is suitable for use as the sole layer in a
shielding tape, or it may be used without similar layers 84, or
with other different layers discussed herein, in different
orientations described herein and with different surface treatments
described herein.
[0055] FIGS. 6G and 6H show another metallic layer 90 of a
shielding tape with a plurality of dimples or concavities 91 formed
therein and arranged in an array. These concavities 91 alleviate
any stresses present and decrease the likelihood that stresses will
cause a micro-fracture. Moreover, where stresses do cause a
micro-fracture, such concavities 91 prevent and limit further
expansion of the micro-fractures beyond the concavity 91. The
concavities 91 thus act as a stop to migration or extension of
micro-fractures across more of the layer 90.
[0056] Each concavity 91 is a semi-spherical concave depression,
extending into the body of the layer 90. The concavities 91 all
have a major dimension corresponding to the diameter of the
semi-spherical depression. In the array of concavities 91 in the
layer 90, the concavities 91 are arranged in rows, and the
concavities 91 in each row are offset horizontally from those in
the row above and below. The concavities 91 are preferably but not
necessarily spaced apart by at least the major dimension. The
concavities 91 preferably have a circular shape, with their major
dimension being a diameter, but in other embodiments may have other
shapes. When the shear stress 41 is applied, the layer 90 stretches
along the direction of the shear stress 41 and the concavities 91
deform. Because the concavities 91 are semi-spherical, they can
expand. They have more surface area than their cross-sectional
circular outline circumscribes, and that surface area is stretched
out when the layer 90 stretches under the shear stress 41. When the
shear stress 41 is released, the concavities 91 return to their
original shape, as in FIG. 6G.
[0057] The layer 90 is suitable for use as the sole layer in a
shielding tape, or it may be used without similar layers 90, or
with other different layers discussed herein, in different
orientations described herein and with different surface treatments
described herein.
[0058] As noted above, an elastomeric adhesive may be used between
layers of the shielding tape. The elastomeric adhesive has
elastomeric characteristics. The adhesive may be alternately
formulated, however, to include metallic solids. An adhesive
containing metallic solids may be elastomeric or
non-elastomeric.
[0059] In FIG. 7A, three layers 94, 95, and 96 are shown, each with
an electrically-conductive adhesive 97 disposed between. The
adhesive 97 preferably but not necessarily includes the elastomeric
adhesive 98 and small metallic solids 99 dispersed throughout the
adhesive 98. In some embodiments, the adhesive 97 includes the
metallic solids 99 and a non-elastomeric adhesive 98. The metallic
solids 99 include aluminum, nickel, copper, carbon, graphene, or
other like metals having good electrical conductivity properties,
and range in size as small as only a few microns, such as just two
or three microns in dimension, though they are illustrated in these
drawings as much bigger for clarity only. The metallic solids 99
are homogenously dispersed and have a high density within the
adhesive 97 to prevent transmission of very high frequency RF
ingress or egress signals, and the conductivity (and thus noise
mitigation properties) of the adhesive 97 improves with greater
density of metallic solids 99 through quantum tunneling effects. RF
signal or noise ingress or egress through the adhesive bond between
the layers 94, 95, and 96 is effectively minimized by means of the
electrically conductive adhesive 97. The dispersion of metallic
solids 99 in the adhesive 97 enhances shielding effectiveness, and
the adhesive 97 itself is thereby made to serve as a barrier to RF
signals, sometimes without the need for an additional layer of
laminate material or metallic layer. If or where micro-fractures
develop in the layers 94, 95, and 96, the electrically-conductive
adhesive 97 mitigates the transmission of egress noise N.
[0060] The electrically-conductive adhesive 97 is used in another
context as well. FIGS. 7B and 7C illustrate an exemplary electronic
cable 100 having a center conductor 101, a dielectric insulator 102
surrounding the center conductor 101, and shielding tape 103
wrapped around the insulator 102. The shielding tape 103 has
opposed edges 104 and 105. The edges 104 and 105 overlap slightly
to form an overlap gap 106. The electrically-conductive adhesive 97
is disposed in this overlap gap 106. The adhesive 97, dispersed
with metallic solids 99, bonds the edges 104 and 105 to each other
to prevent the shielding tape 103 from separating. However, the
electrically-conductive adhesive 97 also prevents the gap 106 from
becoming a tunnel for RF signal or noise ingress and egress.
[0061] It is noted that these methods, features, structures, and
construction techniques can be combined. For example, the shielding
tape 113 of FIG. 1C may have a layer with waffling, that layer may
be elastomerically bonded at the edges, and an
electrically-conductive adhesive may be used within an overlap gap
when the shielding tape 113 is wrapped around the dielectric 112.
Other combinations of the above mitigation features are
contemplated as well.
[0062] A preferred embodiment is fully and clearly described above
so as to enable one having skill in the art to understand, make,
and use the same. Those skilled in the art will recognize that
modifications may be made to the description above without
departing from the spirit of the invention, and that some
embodiments include only those elements and features described, or
a subset thereof. To the extent that modifications do not depart
from the spirit of the invention, they are intended to be included
within the scope thereof.
* * * * *