U.S. patent application number 10/053048 was filed with the patent office on 2003-04-24 for electrical interconnect between an articulating display and a pc based planar board.
Invention is credited to Kruse, John M., Kukson, Dean.
Application Number | 20030075349 10/053048 |
Document ID | / |
Family ID | 21981588 |
Filed Date | 2003-04-24 |
United States Patent
Application |
20030075349 |
Kind Code |
A1 |
Kruse, John M. ; et
al. |
April 24, 2003 |
ELECTRICAL INTERCONNECT BETWEEN AN ARTICULATING DISPLAY AND A PC
BASED PLANAR BOARD
Abstract
A flexible interconnect for electrically connecting a display
unit to a data processing unit to facilitate transmission of low
voltage differential signals and inhibit electromagnetic
interference (EMI). The flexible interconnect includes a conductive
layer extending along a plane and an upper and lower insulative
layer above and below the conductive layer. The interconnect
includes an upper and lower shield layer above and below the upper
and lower insulative layer. The flexible interconnect layers form
first and second opposing sides orthogonal to the plane of the
conductive layer. The interconnect also includes at least two
conductive shield members that face the first and second opposing
sides of the flexible interconnect layers. The two conductive
shield members electrically connect the upper and lower shield
layer on each opposing side such that the conductive shield members
and the shield layers inhibit EMI about the length of the flexible
interconnect.
Inventors: |
Kruse, John M.; (New
Brighton, MN) ; Kukson, Dean; (Pine Island,
MN) |
Correspondence
Address: |
MEDTRONIC, INC.
710 MEDTRONIC PARKWAY NE
MS-LC340
MINNEAPOLIS
MN
55432-5604
US
|
Family ID: |
21981588 |
Appl. No.: |
10/053048 |
Filed: |
October 19, 2001 |
Current U.S.
Class: |
174/390 |
Current CPC
Class: |
H05K 1/0393 20130101;
H01B 7/0838 20130101; H01B 7/0861 20130101; H05K 1/0218
20130101 |
Class at
Publication: |
174/35.00C |
International
Class: |
H05K 009/00 |
Claims
We claim:
1. A flexible interconnect arrangement (FIA) adapted to transmit
low voltage differential signals along a length of the FIA and
inhibit electromagnetic radiation generated as the signals travel
along the length of the FIA, the FIA comprising: a conductive layer
extending parallel to a plane along the length of the FIA, an upper
insulative layer and a lower insulative layer respectively above
and below the conductive layer, and an upper shield layer and lower
shield layer respectively above and below the upper insulative
layer and the lower insulative layer, said layers forming at least
first and second opposing sides orthogonal to the plane of the
conductive layer; and at least two conductive shield members
adapted to face the respective first and second opposing sides of
said layers and to electrically connect the upper shield layer and
the lower shield layer on each opposing side, respectively, wherein
the conductive shield members and the shield layers are adapted to
inhibit EMI about the length of the FIA.
2. The FIA of claim 1, wherein the conductive shield members are
comprised of a plurality of sets of conductive vias adapted to be
located along the length of the FIA.
3. The FIA of claim 1, wherein the upper shield layer is comprised
of an ultra fine mesh.
4. The FIA of claim 3, wherein the ultra fine mesh is comprised of
a silver etched screen.
5. The FIA of claim 1, wherein the lower shield layer is comprised
of a grounding mesh plane.
6. The FIA of claim 5, wherein the grounding mesh plane is
comprised of a copper material.
7. The FIA of claim 1, wherein the conductive layer is comprised of
copper traces.
8. The FIA of claim 1, wherein the conductive layer and the upper
shield layer are separated by at least two insulative layers having
a combined thickness of less than 0.070 millimeters and exhibit an
impedance of about 100 ohms.
9. The FIA of claim 1, further comprising a second upper insulative
layer above the upper shield layer and a second lower insulative
layer below the lower shield layer.
10. The FIA of claim 1, wherein the conductive vias have a spacing
along the length of the FIA of about 1/4 of the wavelength of the
low voltage differential signals.
11. A data processing arrangement comprising: a display unit; a
data processing unit; and a flexible interconnect arrangement (FIA)
adapted to be coupled between the display unit and the data
processing unit and transmit low voltage differential signals to
the display unit along a length of the flexible interconnect
arrangement, wherein the flexible interconnect arrangement
includes: a conductive layer extending parallel to a plane along
the length of the FIA, an upper insulative layer and a lower
insulative layer respectively above and below the conductive layer,
and an upper shield layer and lower shield layer respectively above
and below the upper insulative layer and the lower insulative
layer, said layers forming at least first and second opposing sides
orthogonal to the plane of the conductive layer; and at least two
conductive shield members adapted to face the first and second
opposing sides of said layers respectively and to electrically
connect the upper shield layer and the lower shield layer on each
opposing side, respectively, wherein the conductive shield members
and the shield layers are adapted to inhibit EMI about the length
of the FIA.
12. The data processing arrangement of claim 11, wherein the
flexible interconnect arrangement further includes a portion
adapted to be coupled to the display unit and enable an audio
circuit and a touch screen circuit disposed in the display
unit.
13. The data processing arrangement of claim 11, wherein the upper
shield layer is comprised of an ultra fine conductive mesh adapted
to provide a high radius of flexibility, therein alleviating the
fatigue in the FIA caused by movement of the display unit.
14. The data processing arrangement of claim 1, wherein the
conductive shield members include conductive vias have a spacing
along the length of the FIA of about 1/4 of the wavelength of the
transmitted signals, wherein the conductive vias and the upper and
lower shield layers form an EMI shield about the FIA.
15. The data processing arrangement of claim 13, wherein the lower
shield layer is comprised of a copper mesh grounding plane.
16. The data processing arrangement of claim 11, wherein the data
processing unit includes an implant programming unit.
17. A cable arrangement for use with a data processing arrangement
comprising; a first end adapted to be coupled to a display unit; a
second end adapted to be coupled to a data processing unit; and a
flexible interconnect arrangement (FIA) adapted to be coupled to
the first and second ends and transmit low voltage differential
signals along a length of the FIA, wherein the flexible
interconnect arrangement includes: a conductive layer extending
along a plane in the direction of the length of the FIA, an upper
insulative layer and a lower insulative layer respectively above
and below the conductive layer, and an upper shield layer and lower
shield layer above and below the upper insulative layer and the
lower insulative layer, said layers forming at least first and
second opposing sides orthogonal to the plane of the conductive
layer; and at least two conductive shield members adapted to face
the first and second opposing sides of said layers and to
electrically connect the upper shield layer and the lower shield
layer on each opposing side, respectively, wherein the conductive
shield members and the shield layers are adapted to inhibit EMI
about the length of the FIA.
18. The cable arrangement of claim 17, wherein the conductive
shield members of the FIA include conductive vias have a spacing
along the length of the FIA of about 1/4 of the wavelength of the
low voltage differential signals, wherein the conductive vias and
the upper and lower shield layers form an EMI shield about the
FIA.
19. The cable arrangement of claim 17, wherein the upper shield
layer of the FIA is comprised of an ultra fine conductive mesh.
20. The cable arrangement of claim 17, further comprising a second
upper insulative layer above the upper shield layer and a second
lower insulative layer below the lower shield layer of the FIA.
Description
FIELD OF THE INVENTION
[0001] The present invention generally relates to a flexible cable
for coupling a flat panel display with a data processing unit.
Specifically, the invention relates to a flexible cable that
transmits low voltage differential signals and promotes reduced
levels of emissions of electromagnetic radiation.
BACKGROUND OF THE INVENTION
[0002] Portable computer displays receive power and electrical
signals from the base portion of the portable computer via a
flexible cable or circuit board interconnect. The cable or
interconnect should be stable and robust enough to withstand many
wear and fatigue cycles due to repeated opening and closing cycles
without degrading in performance. Where the data rate of
transmission with the display is high, such as with low voltage
differential signaling (LVDS) used in connection with high-speed
video signals, shielding must be supplied around the flexible
circuit to protect against electromagnetic interference (EMI). EMI
shielding is usually provided by solid ground planes that encase
the signaling lines of the cable.
[0003] In order to reduce transmission errors induced by noise
during data transmission, the cable is usually powered at voltage
levels below 3 volts and exhibits impedance levels of over 100
ohms. The ground planes that shield the cable from emitting EMI to
the surrounding computer components also control the impedance of
the cable. However, use of the solid ground planes reduces cable
flexibility and leads to eventual failure of the cable through
fatigue caused by the repetitive opening and closing of the
portable computer display.
[0004] Although it is preferable in low voltage differential
signaling to increase the impedance in the cable, the solid ground
planes tend to reduce the impedance of the cable. Cable impedance
is reduced because of the large capacitance that is generated in
the small vertical spacing between the signal lines and the solid
ground plane. One approach to increasing the impedance in the cable
is to increase the spacing between the signal lines and the solid
ground plane, thereby reducing the capacitance. However, the
increased spacing increases the overall thickness of the cable and
reduces the cable's flexibility. Although operative, such cable
construction is impractical for use in certain applications, such
as in various portable computers because of the cable size and its
predisposition for failure through fatigue.
[0005] A cable arrangement and a data processing system that
addresses the aforementioned problems, as well as other related
problems, are therefore desirable.
SUMMARY OF THE INVENTION
[0006] Various embodiments of the present invention are directed to
addressing the above and other needs involving a flexible
interconnect arrangement for electrically connecting a display unit
to a data processing unit that facilitates the transmission of low
voltage differential signals and inhibits electromagnetic
interference (EMI) along the length of the interconnect
arrangement. In addition, the flexible interconnect arrangement
includes a grounding plane arrangement that results in a thin,
highly flexible structure that is resist to early breakdown as a
result of fatigue.
[0007] According to one embodiment of the invention, a flexible
interconnect arrangement transmits low voltage differential signals
along a length of the flexible interconnect arrangement and
inhibits electromagnetic radiation generated by the signals that
travel along the length of the flexible interconnect arrangement.
The flexible interconnect arrangement includes a conductive layer
extending along a plane in the direction of the length of the
flexible interconnect arrangement and an upper insulative layer and
a lower insulative layer respectively above and below the
conductive layer. The interconnect arrangement further includes an
upper shield layer and lower shield layer above and below the upper
insulative layer and the lower insulative layer. The flexible
interconnect arrangement layers form at least first and second
opposing sides orthogonal to the plane of the conductive layer. The
interconnect arrangement also includes at least two conductive
shield members that face the first and second opposing sides of the
flexible interconnect arrangement layers and electrically connect
the upper shield layer and the lower shield layer on each opposing
side. The conductive shield members and the shield layers inhibit
EMI about the length of the flexible interconnect arrangement.
[0008] The above summary of the present invention is not intended
to describe each illustrated embodiment or every implementation of
the present invention. The figures in the detailed description that
follow more particularly exemplify these embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The invention may be more completely understood in
consideration of the following detailed description of various
embodiments of the invention in connection with the accompanying
drawings, in which:
[0010] FIG. 1 illustrates a flexible interconnect arrangement for
use in a data processing arrangement according to an example
embodiment of the invention; and
[0011] FIG. 2 illustrates a cross section of the flexible
interconnect arrangement of FIG. 1 according to an example
embodiment of the invention.
[0012] While the invention is amenable to various modifications and
alternative forms, specifics thereof have been shown by way of
example in the drawings and will be described in detail. It should
be understood, however, that the intention is not to limit the
invention to the particular embodiments described. On the contrary,
the intention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the invention
as defined by the appended claims.
DETAILED DESCRIPTION
[0013] The present invention is generally directed to an
arrangement and system for a flexible interconnect arrangement for
electrically connecting a display unit to a data processing unit
that facilitates the transmission of low voltage differential
signals and inhibits electromagnetic interference (EMI) along the
length of the flexible interconnect arrangement. While the present
invention is not necessarily limited to such an application, the
invention will be better appreciated using a discussion of example
embodiments in such a specific context.
[0014] In an example embodiment, a flexible interconnect
arrangement (FIA) facilitates low voltage differential signal
communications between an analyzer and a display screen with a
highly flexible, high impedance circuit board structure. Meeting
the high impedance requirement of the flexible interconnect
arrangement requires using solid ground planes that are
sufficiently spaced apart from the copper traces to ensure a high
impedance. This approach increases the thickness of the
interconnect arrangement and makes it impractical for use with
portable display units. The FIA meets the needs for high impedance
and high flexibility by using upper and lower conductive mesh
structures as shields on either side of an insulated copper
tracings layer instead of the more highly conductive solid ground
planes. The lower impedance of the mesh shield layers allows the
shield layers to be closer to the copper tracings layer, therein
reducing the thickness of the FIA. In addition, the arrangement of
and the type of dielectric material used in the insulative layers
immediately above and below form a high impedance structure that
allows the shield layers to be disposed closer to the copper
tracings layer. The mesh shield layers are electrically connected
with each other with conductive vias at various points along the
length of the FIA to form an EMI shield that extends the length of
the FIA.
[0015] FIG. 1 illustrates a flexible interconnect arrangement (FIA)
100 for use in a data processing arrangement according to an
example embodiment of the invention. One example of the data
processing arrangement includes an implanted medical device
programing unit that uses flexible interconnect arrangement (FIA)
100 to electrically connect a programming unit display screen with
an analyzer of the programming unit (not shown). A first end 102 of
flexible interconnect arrangement 100 connects to the display
screen via a connector 103. A second end 104 connects to the
analyzer of the programming unit via a connector 105. In this
example embodiment, FIA 100 includes a third end 106 that connects
to a circuit board in the display screen via connector 107. Third
end 106 of FIA 100 enables the audio circuits located in the
display screen area as well as the touch screen capabilities of the
display screen. For a more detailed discussion of the components
and functionality of an implant programming unit reference can be
made to U.S. Pat. No. 5,324,315 to Grevious, which is assigned to
the assignee of the present invention and is incorporated herein by
reference.
[0016] In this example embodiment, FIA 100 has a predetermined
length L that extends from first end 102 to second end 104 of FIA
100. FIA 100 transmits a series of low voltage differential signals
along the length L from the analyzer to the display screen. During
signal transmission, FIA 100 shields the display and the analyzer
from electromagnetic interference (EMI) that the differential
signals generate as they travel the length of FIA 100. A polymide
coating material coats an upper surface 110 and a lower surface 112
of FIA 100. FIA 100 includes sets of conductive vias 114 that are
located along the length of FIA 100. FIA 100 includes an upper
shield member and a lower shield member (not shown), both of which
extend laterally along the length L of FIA 100, that combine with
vias 114 to form an EMI shield that extends along the length of FIA
100. Spacing between vias 114 along the length L of FIA 100 is
about 1/4 the wavelength of the transmitted signals. The EMI
shielding capability diminishes as the spacing between vias 114
increases. The configuration of the present invention effectively
forms an EMI sleeve around FIA 100.
[0017] The description in connection with FIG. 2 provides a more
detailed discussion of the cross section of FIA 100 taken across
line A-A that includes the upper and lower shield members that form
the EMI shield of the present invention.
[0018] FIG. 2 illustrates a cross section 150 of flexible
interconnect arrangement 100 of FIG. 1 according to an example
embodiment of the invention. Cross section 150 illustrates a copper
tracings layer 152 disposed between two sets of insulative layers
and two shielding layers that form the basic structure of FIA 100.
The manner of arranging the insulative layers, the types of
materials used in the insulative layers and the structure of the
individual shielding layers in combination produce a highly
flexible interconnect arrangement with high impedance.
[0019] Cross section 150 is labeled with the letter T indicating
the direction of signal transmission on FIA 100. FIA 100 includes
conductive layer 152 comprised of copper tracings that extends
along a plane that is parallel to T and extends in the direction of
length L of FIA 110. Conductive layer 152 has about 0.25 ounces of
copper by weight. FIA 100 includes an upper insulative layer 154A
disposed above conductive layer 152 and a lower insulative layer
154B disposed below conductive layer 152. In this example, the
upper and lower insulative layers are formed from an epoxy adhesive
having a dielectric constant of about 4.8. Upper insulative layer
154A has a thickness of about 0.033 mm while lower insulative layer
154B has a thickness of about 0.018 mm.
[0020] FIA 100 includes a second upper insulative layer 156A
disposed above layer 154A and a second lower insulative layer 156B
disposed below layer 154B. In this example, second upper and lower
insulative layers 156A and 156B are formed of a polymide dielectric
having a thickness of about 0.025 mm, respectively. The polyimide
dielectric material has a dielectric constant of about 4.2. FIA 100
includes an additional lower insulative layer 158 that is disposed
below insulative layer 156B. Insulative layer 158 is formed from an
epoxy adhesive and has a thickness of about 0.018 mm.
[0021] FIA 100 further includes an upper conductive shield layer
160 disposed above layer 156A and a lower conductive shield layer
162 disposed below layer 158. In this example, upper shield layer
160 is comprised of an ultra fine silver etched mesh screen having
a thickness of about 0.0015 in. On the other side, lower shield
layer 162 is comprised of a copper ground plane formed from a
copper mesh having a thickness of about 0.0015 in. The mesh
structures of shield layers 160 and 162 form faraday shields about
FIA 100 that provide a high degree of flexibility to FIA 100 while
exhibiting a lower impedance than normal solid ground planes. As
discussed above, the lower impedance of the shield layers
facilitates locating the shield layers closer to each other and to
the copper traces. The dielectric constant of the materials used in
insulative layers 154-158 also contributes to forming a thin and
flexible interconnect that has the high impedance needed for low
voltage differential signaling.
[0022] In this example embodiment, a set of insulative layers
having a combined thickness of less than 0.070 millimeters separate
conductive layer 152 and upper shield layer 160 and exhibit an
impedance of about 100 ohms. Similarly, another set of insulative
layers separate conductive layer 152 and lower shield layer 162 and
exhibit an impedance of about 100 ohms.
[0023] FIA 100 further includes insulative layers above and below
shield layers 160 and 162. In this example embodiment, the
insulative layer above shield layer 160 is comprised of an acrylic
adhesive layer 166 having a thickness of about 0.030 mm and
polymide layer 110 having a thickness of about 0.025 mm. The
insulative layer below shield layer 162 is comprised of an epoxy
adhesive layer 164 having a thickness of about 0.033 mm and
polymide layer 112 having a thickness of about 0.025 mm. The layers
of FIA 100 form a layered structure having a first sidewall 170 and
a second sidewall 172. Sidewalls 170 and 172 are orthogonal to the
plane formed by conductive layer 152 and extend the length of FIA
100 in the direction of T.
[0024] In forming an EMI shield about FIA 100, shield layers 160
and 162 are electrically connected together with at least two
conductive shield members 114 disposed on sidewalls 170 and 172,
respectively. In this example embodiment, shield members 114 are
conductive vias that extend from shield layer 160 down to shield
layer 162. As seen in FIG. 1, each set of conductive vias 114 are
spaced laterally along the length of FIA 100. The two conductive
shield members 114 electrically connect upper shield layer 160 and
lower shield layer 162 on each opposing side of FIA 100 such that
the conductive shield members and the flexible interconnect
arrangement layer inhibit EMI about the length of FIA 100. Vias 114
are formed of copper but can be formed from silver. Vias 114 are
not limited to formed metallic structures and can include metallic
elements that are adhered to shield layers 160 and 162.
[0025] In another embodiment of the present invention, the
flexibility of FIA 100 increases upon substituting copper mesh
ground plane 162 with a silver etched screen similar to layer 160
of FIG. 2. To reduce cost of FIA 100, silver etched screen layer
160 is substitutable with a copper mesh ground plane similar to
layer 162 of FIG. 2.
[0026] In another embodiment, insulative layers 154A and 156A are
substitutable with a single layer of polyimide dielectric, or a
similar dielectric material, as long as the single polyimide layer
has a similar dielectric constant as that of the combined layers
154A and 156A. Layers 154B and 156B, likewise, are substitutable
with a single dielectric layer having a dielectric constant similar
to the combined layers 154B and 156B.
[0027] The adhesives used in the above described embodiments
include, but are not limited to, butyralthenolic, acrylic
polyimide, PEI, nitriale phenolic and aramide. Materials having
similar dielectric characteristics and adherence to metallic
materials following standard IPC-FC 242 (Institute for Packaging
Electronic Circuits) can also be used in variations of the
described embodiments. In one example application, the epoxy
adhesive has a dielectric constant of about 4.8. The polyimide
layers 110 and 112 have a dielectric constant of about 4.2. Similar
materials that are used as cover layers for coating circuit boards
can be found in standard IPC 232.
[0028] The present invention provides a benefit of forming flexible
interconnect arrangements of different shapes. Referring briefly to
FIG. 1, an "S" configuration 116 can be formed in FIA 100 to
accommodate the hardware design of the display screen and the
analyzer unit. In one example embodiment, the conductive tracings
have linewidths of 0.0036 in. and spacings of 0.006 in.
[0029] The present invention is applicable to the various data
processing arrangements including, but not limited to, personal
notebook and handheld computers, PDAs and wireless communication
devices. Display screens include LCD, electroluminescent or any
other thin film display technology. The display screen can also
include touch-sensitivity capability enabling the user to interact
with the data processing arrangement using a stylus or a user's
hand.
[0030] Various modifications, equivalent processes, as well as
numerous structures to which the present invention may be
applicable will be readily apparent to those of skill in the art to
which the present invention is directed upon review of the present
specification. The claims are intended to cover such modifications
and devices.
* * * * *