U.S. patent application number 12/534077 was filed with the patent office on 2011-02-03 for multi-layer microwave corrugated printed circuit board and method.
Invention is credited to Edward Marsh Jackson, Hee Kyung Kim, Clifton Quan, Kevin C. Rolston, Fangchou Yang.
Application Number | 20110024160 12/534077 |
Document ID | / |
Family ID | 43037070 |
Filed Date | 2011-02-03 |
United States Patent
Application |
20110024160 |
Kind Code |
A1 |
Quan; Clifton ; et
al. |
February 3, 2011 |
MULTI-LAYER MICROWAVE CORRUGATED PRINTED CIRCUIT BOARD AND
METHOD
Abstract
A multi-layer microwave corrugated printed circuit board is
provided. In one embodiment, the invention relates to a method for
interconnecting components of a corrugated printed circuit board,
the components including a first flexible layer having a first
signal line on a surface of the first flexible layer and a second
flexible layer having a second signal line on a surface of the
second flexible layer, the method including forming at least one
first hole in the first flexible layer, forming a conductive pad on
the second flexible layer, forming at least one second hole in a
non-conductive adhesive layer, aligning the at least one second
hole with the at least one first hole and the conductive pad,
bonding the first flexible layer and the second flexible layer,
with the non-conductive adhesive layer disposed there between, and
filling the at least one first hole and the at least one second
hole with a conductive paste to electrically couple the first
signal line with the second signal line.
Inventors: |
Quan; Clifton; (Arcadia,
CA) ; Kim; Hee Kyung; (El Segundo, CA) ; Yang;
Fangchou; (Los Angeles, CA) ; Rolston; Kevin C.;
(Westchester, CA) ; Jackson; Edward Marsh; (Long
Beach, CA) |
Correspondence
Address: |
Christie Parker & Hale LLP
P.O.Box 7068
Pasadena
CA
91109
US
|
Family ID: |
43037070 |
Appl. No.: |
12/534077 |
Filed: |
July 31, 2009 |
Current U.S.
Class: |
174/254 ;
174/261; 29/830; 29/846 |
Current CPC
Class: |
H05K 3/4635 20130101;
H05K 2201/10378 20130101; Y10T 29/49155 20150115; H05K 3/4614
20130101; H05K 1/024 20130101; H05K 1/144 20130101; H05K 2201/09318
20130101; H05K 3/361 20130101; H05K 3/4069 20130101; Y10T 29/49126
20150115; H05K 2201/09109 20130101; H05K 2201/055 20130101; H05K
2203/063 20130101; H05K 1/147 20130101; H05K 1/028 20130101; H05K
2201/058 20130101 |
Class at
Publication: |
174/254 ; 29/830;
29/846; 174/261 |
International
Class: |
H05K 1/00 20060101
H05K001/00; H05K 3/36 20060101 H05K003/36 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0001] This invention was made with Government support from the
Defense Advanced Research Projects Agency (DARPA) for the
Integrated Sensor Is Structure (ISIS) program and under contract
number FA8750-06-C-0048. The U.S. Government has certain rights in
this invention.
Claims
1. A method for interconnecting components of a corrugated printed
circuit board, the components comprising a first flexible layer
having a first signal line on a surface of the first flexible layer
and a second flexible layer having a second signal line on a
surface of the second flexible layer, the method comprising:
forming at least one first hole in the first flexible layer;
forming a conductive pad on the second flexible layer; forming at
least one second hole in a non-conductive adhesive layer; aligning
the at least one second hole with the at least one first hole and
the conductive pad; bonding the first flexible layer and the second
flexible layer, with the non-conductive adhesive layer disposed
there between; and filling the at least one first hole and the at
least one second hole with a conductive paste to electrically
couple the first signal line with the second signal line.
2. The method of claim 1, wherein the first flexible layer is a
folded flexible layer, and the second flexible layer is a flat
flexible layer.
3. The method of claim 1, wherein the first flexible layer is a
flat flexible layer, and the second flexible layer is a folded
flexible layer.
4. The method of claim 1: wherein the at least one first hole
comprises: a first through hole for the first signal line; a second
through hole for a first ground plane line; and a third through
hole for a second ground plane line; wherein the at least one
second hole comprises: a fourth through hole for the second signal
line; a fifth through hole for a third ground plane line; and a
sixth through hole for a fourth ground plane line; wherein the
filling the at least one first hole and the at least one second
hole with the conductive paste comprises filling the first through
hole, the second through hole, the third through hole, the fourth
through hole, the fifth through hole, and the sixth through hole
with the conductive paste.
5. The method of claim 1, wherein the conductive paste electrically
couples a ground plane of the first flexible layer with a ground
plane of the second flexible layer.
6. The method of claim 1, wherein the conductive paste is a
conductive adhesive paste.
7. The method of claim 1, further comprising adding a
non-conductive paste to the second flexible layer prior to the
bonding the first flexible layer and the second flexible layer.
8. The method of claim 1, further comprising adding a
non-conductive adhesive layer to the second flexible layer prior to
the bonding the first flexible layer and the second flexible
layer.
9. The method of claim 1, further comprising curing the conductive
paste.
10. The method of claim 1, wherein the components of the corrugated
printed circuit board further comprise a third flexible layer and a
fourth flexible layer.
11. The method of claim 10, wherein the third flexible layer is a
folded flexible layer, and the fourth flexible layer is a flat
flexible layer.
12. The method of claim 10: wherein the first flexible layer is a
flat flexible layer, and the second flexible layer is a folded
flexible layer; wherein the third flexible layer is a flat flexible
layer, and the fourth flexible layer is a folded flexible layer;
wherein the third flat flexible layer is coupled between the second
folded flexible layer and the fourth folded flexible layer; wherein
a flute of the second folded flexible layer extends in a first
direction; wherein a flute of the fourth folded flexible layer
extends in a second direction; and wherein the first direction and
the second direction are not the same.
13. An interconnect assembly for a corrugated printed circuit
board, the interconnect assembly comprising: a first flexible layer
having a first signal line on a surface of the first flexible
layer, the first flexible layer comprising a first hole; a second
flexible layer having a second signal line on a surface of the
second flexible layer, the second flexible layer comprising a
conductive pad; a non-conductive adhesive layer having a second
hole, the non-conductive adhesive layer disposed between, and
coupled with, the first flexible layer and the second flexible
layer, wherein the first hole, the second hole, and conductive pad
are aligned such that the first hole and second hole comprise a
third hole; and conductive paste disposed within the third hole to
electrically couple the first signal line and the second signal
line.
14. The interconnect assembly of claim 13, wherein the first
flexible layer is a folded flexible layer, and the second flexible
layer is a flat flexible layer.
15. The interconnect assembly of claim 13, wherein the first
flexible layer is a flat flexible layer, and the second flexible
layer is a folded flexible layer.
16. The interconnect assembly of claim 13: wherein the first hole
comprises a first through hole for the first signal line; wherein
the first flexible layer further comprises: a second through hole
for coupling a ground plane of the first flexible layer; and a
third through hole for coupling the ground plane of the first
flexible layer; wherein the second hole comprises a fourth through
hole for the second signal line; and wherein the second flexible
layer further comprises: a fifth through hole for coupling a ground
plane of the second flexible layer; and a sixth through hole for
coupling to the ground plane of the second flexible layer.
17. The interconnect assembly of claim 13, wherein the conductive
paste is a conductive adhesive paste.
18. The interconnect assembly of claim 13, further comprising a
non-conductive paste disposed on the second flexible layer.
19. The interconnect assembly of claim 13, further comprising a
non-conductive adhesive layer disposed on the second flexible
layer.
20. The interconnect assembly of claim 13, further comprising a
third flexible layer and a fourth flexible layer.
21. The interconnect assembly of claim 20, wherein the third
flexible layer is a folded flexible layer, and the fourth flexible
layer is a flat flexible layer.
22. The interconnect assembly of claim 20: wherein the first
flexible layer is a flat flexible layer, and the second flexible
layer is a folded flexible layer; wherein the third flexible layer
is a flat flexible layer, and the fourth flexible layer is a folded
flexible layer; wherein the third flat flexible layer is coupled
between the second folded flexible layer and the fourth folded
flexible layer; wherein a flute of the second folded flexible layer
extends in a first direction; wherein a flute of the fourth folded
flexible layer extends in a second direction; and wherein the first
direction and the second direction are not the same.
Description
BACKGROUND
[0002] The present invention relates generally to printed circuit
boards for use in communication systems. More specifically, the
invention relates to multi-layer microwave corrugated printed
circuit boards and methods for interconnecting the printed circuit
boards.
[0003] Next generation large area multifunction active arrays for
applications such as space and airborne based antennas need to be
lighter weight, lower cost and more conformal than what can be
achieved with current active array architecture and multilayer
active panel array development. These space and airborne antennas
can be used for radar and communication systems, including
platforms such as micro-satellites and stratospheric airships.
[0004] The trend toward thinner and lighter multilayer mixed signal
printed circuit board (PCB) panels integrating monolithic microwave
integrated circuit (MMIC) and digital integrated circuits as well
as power components is driven by installation requirements for
these future platforms such as airships and micro-satellites.
Minimizing the weight of these panels and the devices located
thereon while maintaining panel strength sufficient to be part of
an aircraft secondary structure are important design
considerations. Conventional PCB construction for multi-layer mixed
signal panels can be too complex and heavy to meet weight reduction
requirements. A number of challenges for meeting the weight
reduction requirements exist. For example, in conventional PCB
construction, the circuit layers are generally laminated together
with full sheets of bond ply adhesive film, which can contribute
significantly to the weight of the panel. Accordingly, there is a
need for a light weight PCB assembly that provides robust
structural characteristics.
SUMMARY OF THE INVENTION
[0005] Aspects of the invention relate to a multi-layer microwave
corrugated printed circuit board. In one embodiment, the invention
relates to a method for interconnecting components of a corrugated
printed circuit board, the components including a first flexible
layer having a first signal line on a surface of the first flexible
layer and a second flexible layer having a second signal line on a
surface of the second flexible layer, the method including forming
at least one first hole in the first flexible layer, forming a
conductive pad on the second flexible layer, forming at least one
second hole in a non-conductive adhesive layer, aligning the at
least one second hole with the at least one first hole and the
conductive pad, bonding the first flexible layer and the second
flexible layer, with the non-conductive adhesive layer disposed
there between, and filling the at least one first hole and the at
least one second hole with a conductive paste to electrically
couple the first signal line with the second signal line.
[0006] In another embodiment, the invention relates to an
interconnect assembly for a corrugated printed circuit board, the
interconnect assembly including a first flexible layer having a
first signal line on a surface of the first flexible layer, the
first flexible layer including a first hole, a second flexible
layer having a second signal line on a surface of the second
flexible layer, the second flexible layer including a conductive
pad, a non-conductive adhesive layer having a second hole, the
non-conductive adhesive layer disposed between, and coupled with,
the first flexible layer and the second flexible layer, wherein the
first hole, the second hole, and conductive pad are aligned such
that the first hole and second hole include a third hole, and
conductive paste disposed within the third hole to electrically
couple the first signal line and the second signal line.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a side view of a corrugated printed circuit board
in accordance with one embodiment of the invention.
[0008] FIG. 2 is a exploded perspective view of a two layer
corrugated printed circuit board in accordance with one embodiment
of the invention.
[0009] FIG. 3 is a perspective view of the two layer corrugated
printed circuit board of FIG. 2.
[0010] FIG. 4 is a exploded perspective view of the two layer
corrugated printed circuit board of FIG. 2 in accordance with one
embodiment of the invention.
[0011] FIG. 5 is a perspective view of the two layer corrugated
printed circuit board of FIG. 4.
[0012] FIG. 6 is a perspective view of a number of corrugated
printed circuit boards having different widths in accordance with
one embodiment of the invention.
[0013] FIG. 7 is a close up view of an interconnect between a
folded flex layer and a flat flex layer of a corrugated printed
circuit board in accordance with one embodiment of the
invention.
[0014] FIG. 8 is a top view of a portion of the interconnect of
FIG. 7 including three lines of a microstrip transmission line in
accordance with one embodiment of the invention.
[0015] FIG. 9 is a cross sectional inverted view of the flat flex
layer of FIG. 7 in accordance with one embodiment of the
invention.
[0016] FIG. 10 is an exploded cross sectional view of an
interconnect of a folded flex layer and a flat flex layer with an
adhesive layer positioned there between in accordance with one
embodiment of the invention.
[0017] FIG. 11 is an exploded cross sectional view of the
interconnect of FIG. 10 taken along section A-A.
[0018] FIG. 12 is a cross sectional view of the interconnect of
FIG. 10 illustrating a through hole extending through the flat flex
layer and the adhesive layer to a conductor pad positioned on the
folded flex layer of the interconnect.
[0019] FIG. 13 is a cross sectional view of the interconnect of
FIG. 10 taken along the section A-A which illustrates three through
holes extending through the flat flex layer and the adhesive layer
to conductor pads positioned on the folded flex layer of the
interconnect.
[0020] FIG. 14 is a view of the interconnect of FIG. 12 after
conductive paste has been inserted into the through hole.
[0021] FIG. 15 is a view of the interconnect of FIG. 13 after
conductive paste has been inserted into the three through
holes.
[0022] FIG. 16 is a flow chart of a process for assembling a
corrugated printed circuit board in accordance with one embodiment
of the invention.
[0023] FIG. 17a-17c are assembly drawings of a process for
assembling a corrugated printed circuit board in accordance with
one embodiment of the invention.
[0024] FIG. 18a-18c are assembly drawings of another process for
assembling a corrugated printed circuit board in accordance with
one embodiment of the invention.
[0025] FIG. 19 is a flow chart of a process for forming an
interconnect for a corrugated printed circuit board in accordance
with one embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0026] Referring now to the drawings, embodiments of systems and
methods for interconnecting components of corrugated printed
circuit boards (PCBs) are illustrated. In a number of embodiments,
the corrugated PCBs include a first flexible layer having a first
signal line on a surface of the first flexible layer and a second
flexible layer having a second signal line on a surface of the
second flexible layer. Embodiments of methods for forming an
interconnect between the first and second layers can include
forming a first hole in the first flexible layer, a conductive pad
on the second flexible layer, and a second hole in a non-conductive
adhesive layer disposed between the first and second layers,
aligning the second hole with the first hole and the conductive
pad, bonding the first flexible layer and the second flexible
layer, and filling the first hole and the second hole with a
conductive paste to electrically couple the first signal line with
the second signal line.
[0027] In several embodiments, the first layer includes multiple
through holes aligned with corresponding through holes in the
non-conductive adhesive layer and multiple pads on the second
layer. For example, in one embodiment, the first layer includes
three through holes aligned with three through holes in the
non-conductive adhesive layer and three pads on the second layer.
In one embodiment, the first layer is a flat flexible circuit layer
and the second layer is a folded flexible circuit layer. Together
the layers can form a corrugated circuit board structure. In
another embodiment, the first layer is a folded flexible circuit
layer and the second layer is a flat flexible circuit layer. In
some embodiments, the corrugated PCBs can include more than two
layers. In a number of embodiments, interconnects are formed at
multiple locations on surfaces of the first and second layers.
[0028] While not bound by any particular theory, architects have
known for years that an arch with the proper curve is the strongest
way to span a given space. Embodiments of the corrugated PCBs
described herein incorporate this same principle when they include
arches in the corrugated medium. These arches are known as flutes
and when anchored to a linerboard with an adhesive, they resist
bending and pressure from all directions. Corrugated fiberboard, or
combined board, has two main components: the linerboard and the
medium. Both are made of a special kind of heavy paper called
container board for cardboard applications (e.g., boxes).
Linerboard is the flat facing that adheres to the medium. The
medium is the wavy, fluted paper in between the liners.
[0029] The corrugation manufacturing processes are most commonly
used to make boxes having one layer of fluting between two smooth
sheets. When a piece of combined board is placed on its end, the
arches form rigid columns, capable of supporting a great deal of
weight. When pressure is applied to the side of the board, the
space in between the flutes acts as a cushion to protect the
container's contents. The flutes also serve as an insulator,
providing some product protection from sudden temperature changes.
At the same time, the vertical liner board provides more strength
and protects the flutes from damage. Flutes come in several
standard shapes or flute profiles.
[0030] Embodiments of multi-layer corrugated printed circuit boards
can be made of flexible circuit board material configured in an
alternating combination of arched layers between smooth sheets. In
some embodiments, the corrugated PCBs are used as with microwave
and/or mixed signal designs. Corrugation is applied to the
manufacturing of multi-layer printed flex circuit boards to created
extremely durable, versatile, economical and lightweight assemblies
of microwave multi-chip mixed signal electronic panels used for
airborne platforms such as airships and micro-satellites where
weight and cost are important factors. Microwave, digital and power
integrated circuits (ICs) can be attached with reflowed solder
paste on top or in between the layer and folds as shown in FIG. 1
using standard flip chip surface mounting techniques. Microwave,
digital and power signal traces can be routed along the fluted flex
layers. Depending on the desired weight, component density and
panel strength for a particular application, there are many types
and combinations of corrugated layers available, each with
different flute sizes and thicknesses. These formed layers, such as
a wafer pattern, can offer enhanced structure, routing flexibility
and functionality.
[0031] FIG. 1 is a side view of a corrugated printed circuit board
100 in accordance with one embodiment of the invention. In some
embodiments, the corrugated PCB can be used in conjunction with an
active array antenna for a radar or a communication system. The
corrugated printed circuit board 100 includes a level one assembly
102, a level two assembly 104 and a level three assembly 106. The
level one assembly 102 can include one or more apertures, an radio
frequency (RF) feed, electronic components and power and
communication signals. The level two assembly 104 can include an RF
feed, electronic components and power and communication signals.
The level three assembly 106 can also include an RF feed,
electronic components and power and communication signals. An
example of a printed circuit board having a multiple assembly
levels is described in U.S. Pat. No. 7,525,498, the entire content
of which is incorporated herein by reference.
[0032] FIG. 2 is a exploded perspective view of a two layer
corrugated printed circuit board 200 in accordance with one
embodiment of the invention. The corrugated printed circuit board
200 includes a top flat flexible layer 208, a first folded or
fluted flexible layer 210, a middle flat flexible layer 212, a
second folded or fluted flexible layer 214, and a bottom flat
flexible layer 216. In other embodiments, the corrugated PCB can
include more than two fluted layers and more than three flat
layers.
[0033] In the embodiment illustrated in FIG. 2, the flutes of the
first or upper fluted layer 210 extend in the same direction as the
flutes of the second or lower fluted layer 214. In other
embodiments, the flutes of the upper fluted layer and the lower
fluted layers can extend in different directions. In one
embodiment, the flutes of the upper fluted layer extend in a
direction that is perpendicular to the flutes of the lower fluted
layer, or vice versa. In other embodiments, additional fluted
layers are included and the flutes of each fluted layer can extend
in the same direction, or in different directions. In the
embodiment illustrated in FIG. 2, the fluted layers have a specific
height and width for the flutes. In other embodiments, the fluted
layers can have other heights and widths for the flutes.
[0034] FIG. 3 is a perspective view of the two layer corrugated
printed circuit board 200 of FIG. 2.
[0035] FIG. 4 is a exploded perspective view of the two layer
corrugated printed circuit board 200 of FIG. 2 in accordance with
one embodiment of the invention. The two layer PCB 200 includes all
of the same components of the embodiment illustrated in FIG. 2,
except that the flutes of the second fluted flexible layer 215
extend in a direction perpendicular to the flutes of the first
fluted flexible layer 210.
[0036] FIG. 5 is a perspective view of the two layer corrugated
printed circuit board of FIG. 4.
[0037] FIG. 6 is a perspective view of a number of corrugated
printed circuit boards having different widths in accordance with
one embodiment of the invention. Embodiments of corrugated printed
circuit boards for the present invention can include flutes having
several standard shapes or flute profiles (A, B, C, E, F, etc.) as
shown in FIG. 6. The A-flute was the first to be developed and is
one of the largest flute profiles. The B-flute was next and is much
smaller. The C-flute followed and is between A and B in size. The
E-flute is smaller than the B-flute and the F-flute is smaller yet.
In addition to these five profiles, new flute profiles, both larger
and smaller than those listed here, can be created for more
specialized boards. Generally, larger flute profiles deliver
greater vertical compression strength and cushioning. Smaller flute
profiles provide enhanced structural capabilities. Different flute
profiles can be combined in one piece of combined board. For
instance, in a triple wall board, one layer of medium might be
A-flute while the other two layers may be C-flute. Mixing flute
profiles in this way allows designers to manipulate the compression
strength, cushioning strength and total thickness of the combined
board to suit requirements for particular applications.
[0038] FIG. 7 is a close up view of an interconnect 300 between a
folded flex layer 310 and a flat flex layer 312 of a corrugated
printed circuit board in accordance with one embodiment of the
invention. The interconnect 300 further includes a dielectric
adhesive layer 311 or spacer disposed between the folded flex layer
310 and the flat flex layer 312. An RF communication signal 313
passes along the flat flex layer 312 toward and through the
adhesive layer 311 and then along the folded flex layer 310. In
FIG. 7, the flat flex layer 312 is configured as a microstrip
transmission line or microstripline for passing the RF
communication signal 313. As such, the flat layer 312 has a signal
conductor 315 disposed along a bottom surface of the flat layer 312
and a groundplane conductor 317 disposed along a top surface of the
flat layer 312. In FIG. 7, the folded flex layer 310 is also
configured as a microstrip transmission line or microstripline for
passing the RF communication signal 313. As such, the flat layer
310 has a signal conductor 319, or microstripline, disposed along a
bottom surface of the folded layer 310 and a groundplane conductor
321 disposed along a top surface of the flat layer 310.
[0039] In the embodiment illustrated in FIG. 7, the RF
communication signal 313 passes along the bottom of the flat layer
312, via signal conductor 315, from right to left, transitions to
the folded layer 310 via the interconnect and continues along a
bottom of the folded layer 310, via signal conductor 319. In other
embodiments, the RF communication signal 313 can follow other
suitable paths along the flat and folded layers. In one embodiment,
the dielectric adhesive layer can have a dielectric constant of
3.5. In other embodiments, the dielectric adhesive layer can have
other suitable dielectric constant values. In the embodiment
illustrated in FIG. 7, the folded flex layer and the flat flex
layer are configured as microstripline transmission lines. In other
embodiments, the folded flex layer and the flat flex layer can be
configured to support other suitable types of transmission
lines.
[0040] FIG. 8 is a top view of a portion of the interconnect 300 of
FIG. 7 showing a three wire interconnect for connecting signal
lines of a microstrip transmission line in accordance with one
embodiment of the invention. The three wire interconnect includes a
middle line interconnect 323 for an RF signal, and two outer line
interconnects 325 and 327 for the associated ground plane
signals.
[0041] FIG. 9 is a cross sectional inverted view of the flat flex
layer 312 of FIG. 7 in accordance with one embodiment of the
invention. The flat flex layer 312 is configured as a microstrip
transmission line which includes the signal conductor trace 315 on
one surface of the flat layer 312 and a ground plane 317 disposed
on an opposite side of the flat layer 312, where the surfaces are
separated by a dielectric layer 329. In one embodiment, the
dielectric layer can have a dielectric constant of 2.9. In other
embodiments, the dielectric layer can have other suitable
dielectric constant values.
[0042] FIG. 10 is an exploded cross sectional view of an
interconnect 400 of a folded flex layer 410 and a flat flex layer
412 with an adhesive layer 411 positioned there between in
accordance with one embodiment of the invention. FIG. 11 is an
exploded cross sectional view of the interconnect 400 of FIG. 10
taken along section A-A.
[0043] When the interconnect is assembled, an RF communication
signal can pass along the flat flex layer 412 toward and through
the adhesive layer 411 and then along the folded flex layer 410 or
vice versa. The folded flex layer 410 is configured as a microstrip
transmission line or microstripline for passing the RF
communication signal. As such, the flat layer 410 has a signal
conductor 419, or microstripline, disposed along a bottom surface
of the folded layer 410 and a groundplane conductor 421 disposed
along a top surface of the flat layer 410.
[0044] To form the interconnect 400, the folded layer 410 further
includes conductive pads 434a, 434b and 434c and ground plane
through holes 440. Conductive pad 434a is used to provide a pathway
for the RF communication signal, while conductive pads 434b and
434c are used to provide pathways for groundplane signals via
through holes 440. To form the interconnect 400, the adhesive layer
411 includes through holes 432a, 432b and 432c extending through
the width of the layer for the RF communication and ground signals,
respectively.
[0045] The flat flex layer 412 is also configured as a microstrip
transmission line or microstripline for passing the RF
communication signal. As such, the flat layer 412 has a signal
conductor 415 disposed along a bottom surface of the flat layer 412
and a groundplane conductor 417 disposed along a top surface of the
flat layer 412. To form the interconnect 400, the flat layer 412
further includes through holes 436a, 436b and 436c for the RF
communication and ground signals, respectively. Conductive pads
surround through holes 436a, 436b and 436c on both the top
groundplane layer 417 and bottom RF signal layer 415 for making
electrical contact with circuit traces. The through holes 436a,
436b and 436c and surrounding conductive pads provide pathways for
the RF communication signal and groundplane signals, respectively.
In a number of embodiments, the through holes discussed herein are
plated through holes.
[0046] FIG. 12 is a cross sectional view of the interconnect 400 of
FIG. 10 illustrating a through hole 433a extending through the flat
flex layer 412 and the adhesive layer 411 to a conductor pad 434a
positioned on the folded flex layer 410 of the interconnect.
Adhesive layer through hole 432a and flat flex layer through hole
436a are aligned to form through hole 433a extending through both
layers to the conductor pad 434a positioned on the folded flex
layer 410.
[0047] FIG. 13 is a cross sectional view of the interconnect 400 of
FIG. 10 taken along the section A-A which illustrates three through
holes (433a, 433b, 433c) extending through both the flat flex layer
412 and the adhesive layer 411 to the conductor pads (434a, 434b,
434c) positioned on the folded flex layer 410 of the
interconnect.
[0048] FIG. 14 is a view of the interconnect of FIG. 12 after
conductive paste 442 has been inserted into through hole 433a. In
some embodiments, the conductive paste also has adhesive
properties.
[0049] FIG. 15 is a view of the interconnect of FIG. 13 after
conductive paste 442 has been inserted into the three through holes
(433a, 433b, 433c). The conductive paste completes an electrical
pathway for the RF communication and ground signals, and provides
additional structural support for the interconnect.
[0050] FIG. 16 is a flow chart of a process for assembling a
corrugated printed circuit board in accordance with one embodiment
of the invention. The process 500 shows different paths to produce
an interconnect that can be used to attach components of a
corrugated printed circuit. In one embodiment, the process 500
produces a flexible circuit attachment using a conductive fill,
disposed within an open hole of a bottom flex circuit, that forms
an electrical interconnect between a conductor on the bottom flex
circuit and a conductor on the top flex circuit.
[0051] The process first designs and fabricates (501) a bottom
flexible circuit, or flex circuit, with a hole and an annular ring
at preselected attachment locations on a top surface of the bottom
flex circuit. The process also designs and fabricates (502) a top
flexible circuit with conductive pads at preselected attachment
locations, that correspond to the attachment locations of the
bottom flex circuit, on a bottom surface of the top flex circuit.
From block 502, the process can mechanically attach the flex
circuits using multiple sub-processes. In a first sub-process
(solid arrow path), the process aligns (506) and fusion bonds (507)
the flex circuits. The aligning can include aligning the top and
bottom flex circuits so that the holes are in line with the pads.
In a second sub-process (dashed arrow path (2)), the process
dispenses (505) a non-conductive paste on the top and/or bottom
flex circuits. The process then aligns (506) the flex circuits and
bonds (508) the common flat areas of the flex circuits together
using heat and pressure.
[0052] In a third sub-process (dashed arrow path (1)), the process
precuts (503) holes in a non-conductive film adhesive where
electrical connections are intended to be positioned. The process
then aligns (504) the non-conductive adhesive on the bottom and/or
top flex layers and tacks it into place. The process then aligns
(506) the flex circuits and bonds (508) the common flat areas of
the flex circuits together using heat and pressure. Once the top
and bottom flex circuits have been attached, the process dispenses
(509) conductive adhesive paste into the hole(s) to fill the area
created by the hole and to thereby attach the bottom flex circuit
with the pad of the top flex circuit. The process then cures (510)
the conductive adhesive paste.
[0053] In one embodiment, the process can perform the sequence of
actions in any order. In another embodiment, the process can skip
one or more of the actions. In other embodiments, one of more of
the actions are performed simultaneously. In some embodiments,
additional actions can be performed.
[0054] In one embodiment, the top flex circuit can be a folded flex
circuit/layer and the bottom flex circuit can be flat flex
circuit/layer. In such case, the bottom/flat flex circuit includes
the through hole and the top/folded flex circuit includes the
pad(s). In another embodiment, the top flex circuit can be a flat
flex circuit/layer and the bottom flex circuit can be folded flex
circuit/layer. In such case, the bottom/folded flex circuit
includes the through hole and the top/flat flex circuit includes
the pad(s).
[0055] In the process illustrated in FIG. 16, the process may at
times refer to a single hole or pad. However, the process generally
relates to use of multiple holes and pads.
[0056] FIG. 17a-17c are assembly drawings of a process for
assembling an interconnect for a corrugated printed circuit board
in accordance with one embodiment of the invention. In the
embodiment illustrated in FIG. 17a-17c, the top flex circuit is
folded and the bottom flex circuit is flat. FIG. 17a illustrates an
exploded cross sectional assembly view of the interconnect prior to
bonding. FIG. 17b illustrates a cross sectional view of the bonded
interconnect assembly prior to insertion of conductive paste. FIG.
17c illustrates a cross sectional view of the bonded interconnect
assembly after the holes have been filled with conductive paste. In
some embodiments, the conductive paste includes adhesive
properties.
[0057] FIG. 18a-18c are assembly drawings of a process for
assembling an interconnect for a corrugated printed circuit board
in accordance with one embodiment of the invention. In the
embodiment illustrated in FIG. 18a-18c, the top flex circuit is
flat and the bottom flex circuit is folded. FIG. 18a illustrates an
exploded cross sectional assembly view of the interconnect prior to
bonding. FIG. 18b illustrates a cross sectional view of the bonded
interconnect assembly prior to an insertion of conductive paste.
FIG. 18c illustrates a cross sectional view of the bonded
interconnect assembly after the holes have been filled with
conductive paste. In some embodiments, the conductive paste
includes adhesive properties.
[0058] FIG. 19 is a flow chart of a process 600 for forming an
interconnect for a corrugated printed circuit board in accordance
with one embodiment of the invention. In a number of embodiments,
the corrugated PCB includes a first flexible layer having a first
signal line on a surface of the first flexible layer and a second
flexible layer having a second signal line on a surface of the
second flexible layer. The process begins by forming (602) at least
one first hole in the first flexible layer. In several embodiments,
the first hole is a plated through hole coupled to the first signal
line of the first layer. The process then forms (604) a conductive
pad on the second flexible layer. In several embodiments, the
conductive pad is coupled to the second signal line. The process
then forms (606) at least one second hole in a non-conductive
adhesive layer. The process then aligns (608) the second hole with
the first hole and the conductive pad. The process then bonds (610)
the first flexible layer and the second flexible layer with the
adhesive layer positioned between the two layers. The process
completes by filling (612) the first hole and the second hole with
a conductive adhesive paste to couple the first and second signal
lines.
[0059] In one embodiment, the first flexible layer is a folded flex
circuit and the second flexible layer is a flat flex circuit. In
another embodiment, the first flexible layer is a flat flex circuit
and the second flexible layer is a folded flex circuit.
[0060] In one embodiment, the process can perform the sequence of
actions in any order. In another embodiment, the process can skip
one or more of the actions. In other embodiments, one of more of
the actions are performed simultaneously. In some embodiments,
additional actions can be performed.
[0061] In one embodiment, the bonding is achieved by a fusion
bonding process. In another embodiment, the bonding is achieved by
bonding the common flat areas of the first flexible layer and the
second flexible layer together using heat and pressure. In some
embodiments, the bonding process is achieved by adding a
non-conductive adhesive film to the first flexible layer and/or the
second flexible layer. In other embodiments, the bonding process is
achieved by adding a non-conductive paste to the first flexible
layer and/or the second flexible layer.
[0062] While the above description contains many specific
embodiments of the invention, these should not be construed as
limitations on the scope of the invention, but rather as examples
of specific embodiments thereof. Accordingly, the scope of the
invention should be determined not by the embodiments illustrated,
but by the appended claims and their equivalents.
* * * * *