U.S. patent application number 14/879191 was filed with the patent office on 2017-04-13 for electronic module with free-formed self-supported vertical interconnects.
The applicant listed for this patent is Raytheon Company. Invention is credited to James Mcspadden, Brandon W. Pillans.
Application Number | 20170105311 14/879191 |
Document ID | / |
Family ID | 56802668 |
Filed Date | 2017-04-13 |
United States Patent
Application |
20170105311 |
Kind Code |
A1 |
Pillans; Brandon W. ; et
al. |
April 13, 2017 |
ELECTRONIC MODULE WITH FREE-FORMED SELF-SUPPORTED VERTICAL
INTERCONNECTS
Abstract
An electronic module, and method for making same, includes
free-formed, self-supported interconnect pillars that electrically
connect cover electronic components disposed on a cover substrate
with base electronic components disposed on a base substrate. The
free-formed, self-supported interconnect pillars may extend
vertically in a straight path between the cover electronic
components and the base electronic components. The free-formed,
self-supported interconnect pillars may be formed from an
electrically conductive filament provided by an additive
manufacturing process. By free-forming the self-supported
interconnect pillars directly on the electronic components, the
flexibility of electronic module design may be enhanced, while
reducing the complexity and cost to manufacture such electronic
modules.
Inventors: |
Pillans; Brandon W.; (Plano,
TX) ; Mcspadden; James; (Allen, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Raytheon Company |
Waltham |
MA |
US |
|
|
Family ID: |
56802668 |
Appl. No.: |
14/879191 |
Filed: |
October 9, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 24/90 20130101;
H01L 2224/85 20130101; H01L 2224/11 20130101; H01L 24/81 20130101;
H01L 2225/0651 20130101; H01L 23/36 20130101; H01L 2224/1134
20130101; H01L 23/5385 20130101; H01L 24/72 20130101; H01L 24/73
20130101; H01L 2224/72 20130101; H01L 24/13 20130101; H05K 13/00
20130101; H01L 2224/92163 20130101; H01L 2225/06589 20130101; H01L
2224/72 20130101; H01L 2224/9202 20130101; H01L 2225/06513
20130101; H01L 2224/9202 20130101; H01L 24/11 20130101; H01L 23/66
20130101; H01L 24/16 20130101; H01L 2224/1308 20130101; H01L
2224/48227 20130101; H01L 2224/16145 20130101; H01L 2224/81901
20130101; H01L 24/48 20130101; H01L 2224/90 20130101; H05K 7/202
20130101; H01L 25/0652 20130101; H01L 2224/81901 20130101; H01L
2224/81191 20130101; H01L 2224/73207 20130101 |
International
Class: |
H05K 7/20 20060101
H05K007/20; H05K 13/00 20060101 H05K013/00 |
Claims
1. A method for assembling an electronic module comprising the
steps: mounting a base electronic component on a base substrate;
mounting a cover electronic component on a cover substrate;
depositing an electrically conductive filament directly on the base
electronic component or directly on the cover electronic component;
free-forming a self-supported interconnect pillar with the
deposited electrically conductive filament, the free-formed,
self-supported interconnect pillar extending upright from the base
electronic component or the cover electronic component; arranging
the cover substrate over the opposing base substrate and aligning
the base electronic component with the cover electronic component;
and electrically connecting the base electronic component to the
cover electronic component with the free-formed, self-supported
interconnect pillar.
2. The method according to claim 1, further comprising the steps:
attaching a compressible electrical interposer at a free-end of the
free-formed, self-supported interconnect pillar; and electrically
interposing the compressible electrical interposer in the
electrical path between the respective free-formed, self-supported
interconnect pillar and the base electronic component or the cover
electronic component.
3. The method according to claim 1, wherein the electrically
conductive filament is an electrically conductive paste.
4. The method according to claim 3, wherein the electrically
conductive paste is deposited to form the free-formed,
self-supported interconnect pillar having a length to width aspect
ratio of at least 3 to 1.
5. The method according to claim 3, wherein the cover electronic
component and the base electronic component each include an
externally addressable face having an electrical contact surface;
wherein the externally addressable face of the cover electronic
component is aligned with and opposingly faces the externally
addressable face of the base electronic component; and wherein the
electrically conductive paste is deposited on the electrical
contact surface of the base electronic component or is deposited on
the electrical contact surface of the cover electronic component
and forms the free-formed, self-supported interconnect pillar in a
straight path for electrically connecting with the opposing
electrical contact surface of the base electronic component or the
cover electronic component.
6. The method according to claim 5, wherein a plurality of the base
electronic components are mounted on the base substrate and a
plurality of the cover electronic components are mounted on the
cover substrate; wherein at least one of the externally addressable
faces of the plurality of cover electronic components is non-planar
with respect to at least one other of the externally addressable
faces of the plurality of cover electronic components, and/or at
least one of the externally addressable faces of the plurality of
base electronic components is non-planar with respect to at least
one other of the externally addressable faces of the plurality of
base electronic components; and wherein the electrically conductive
paste is deposited on one or more of the plurality of base
electronic components and/or one or more of the plurality of cover
electronic components to form a plurality of the free-formed,
self-supported interconnect pillars having varying longitudinal
lengths for electrically connecting the plurality of base
electronic components to the plurality of cover electronic
components and to accommodate for the non-planarity of the
respective externally addressable faces of the plurality of base
electronic components and/or the plurality of cover electronic
components.
7. The method according to claim 3, wherein the electrically
conductive paste is deposited to form the free-formed,
self-supported interconnect pillar having a substantially
cylindrical shape; and wherein the electrical conductivity is
uniform through both a transverse cross-section and along a
longitudinal length of the free-formed, self-supported interconnect
pillar.
8. The method according to claim 7, wherein the electrical
conductivity of the free-formed, self-supported interconnect pillar
is 1.times.10.sup.7 siemens per meter or greater.
9. The method according to claim 3, wherein the electrically
conductive paste is deposited through a layer-wise additive
manufacturing process to form the free-formed, self-supported
interconnect pillar.
10. The method according to claim 3, wherein the electrically
conductive paste is deposited in a single extrusion step to form
the at least one free-formed, self-supported interconnect pillar
extending upright from the base electronic component or the cover
electronic component.
11. The method according to claim 3, further comprising the step of
solidifying the electrically conductive paste.
12. The method according to claim 1, wherein the cover electronic
component mounted on the cover substrate generates more heat than
the base electronic component mounted on the base substrate.
13. The method according to claim 12, further comprising the steps:
attaching a cold plate to the cover substrate; and cooling the
cover electronic component.
14. The method according to claim 1, wherein the electronic module
is an RF module, and the free-formed, self-supported interconnect
pillar is configured to transmit RF or DC signals.
15. The method according to claim 14, wherein the cover electronic
component is a monolithic microwave integrated circuit, and wherein
the base electronic component is an application specific integrated
circuit.
16. An electronic module having a base substrate; a base electronic
component disposed on the base substrate; a cover substrate
disposed over the base substrate; a cover electronic component
disposed on the cover substrate, the cover electronic component
being spaced from the base electronic component; and a
self-supported interconnect pillar electrically connecting the base
electronic component with the cover electronic component, the
electronic module being made by a method comprising the steps:
mounting the base electronic component on the base substrate;
mounting the cover electronic component on the cover substrate;
depositing an electrically conductive filament directly on the base
electronic component or directly on the cover electronic component;
free-forming the self-supported interconnect pillar with the
deposited electrically conductive filament the free-formed,
self-supported interconnect pillar extending upright from the base
electronic component or the cover electronic component; arranging
the cover substrate over the opposing base substrate and aligning
the base electronic component with the cover electronic component;
and electrically connecting the base electronic component to the
cover electronic component with the free-formed, self-supported
interconnect pillar.
17. The electronic module according to claim 16, wherein the
free-formed, self-supported interconnect pillar is formed from an
electrically conductive paste.
18. The electronic module according to claim 17, wherein the cover
electronic component and the base electronic component each include
an externally addressable face having an electrical contact
surface; wherein the externally addressable face of the cover
electronic component is parallel to and directly opposingly faces
the externally addressable face of the base electronic component;
and wherein the free-formed, self-supported interconnect pillar
extends between the respective electrical contact surfaces of the
cover electronic component and the base electronic component, the
free-formed, self-supported interconnect pillar having a length to
width aspect ratio of at least 3 to 1 and being upright and
perpendicular with respect to each of the externally addressable
faces of the cover electronic component and the base electronic
component.
19. The electronic module according to claim 18, wherein the base
substrate includes a plurality of the base electronic components,
the cover substrate includes a plurality of the cover electronic
components, and a plurality of the free-formed, self-supported
interconnect pillars electrically connect the plurality of base
electronic components to the respective plurality of cover
electronic components; wherein at least one of the externally
addressable faces of the plurality of cover electronic components
is non-planar with respect to at least one other of the externally
addressable faces of the plurality of cover electronic components,
and/or at least one of the externally addressable faces of the
plurality of base electronic components is non-planar with respect
to at least one other of the externally addressable faces of the
plurality of base electronic components; and wherein the
free-formed, self-supported interconnect pillars have varying
longitudinal lengths to accommodate for the non-planarity of the
respective externally addressable faces of the plurality of base
electronic components and/or the plurality of cover electronic
components.
20. An RF module according to the electronic module of claim 16,
further comprising a heat exchanger attached to the cover
substrate, wherein the base substrate includes a plurality of the
base electronic components, the cover substrate includes a
plurality of the cover electronic components, and a plurality of
the free-formed, self-supported interconnect pillars electrically
connect the respective plurality of base electronic components to
the respective plurality of cover electronic components; wherein
the plurality of cover electronic components includes one or more
monolithic microwave integrated circuits; wherein the plurality of
base electronic components includes one or more application
specific integrated circuits; and wherein one or more of the
plurality of free-formed, self-supported interconnect pillars is
configured to transmit RF or DC signals.
Description
FIELD OF INVENTION
[0001] The present invention relates generally to electronic
modules, and more particularly to RF modules having free-formed,
self-supported electrical interconnects.
BACKGROUND
[0002] Electronic modules, such as radio frequency (RF) modules,
contain electronic components, such as high-frequency chipsets,
that may take up a considerable amount of space inside the module
and may generate a significant amount of heat. RF modules in a
planar phased array antenna architecture are typically mounted on a
base substrate and the available area for integrating such modules
is often constrained. Typically, cooling is applied through the
bottom of the module via a thermal mass or a restricted cold plate,
which may interfere with RF operation due to the cold plate or
thermal mass being in the direct path of electrical signals on the
planar phased array antenna. As electronic components for RF
modules become increasingly complex, there is a need to improve the
available surface area for mounting such components, as well as
improve the flexibility in electronic module design, while also
enhancing the cooling to such components without interfering with
RF/DC operation.
SUMMARY OF INVENTION
[0003] The present invention provides an electronic module, and
method for making the electronic module, having free-formed,
self-supported interconnect pillars that electrically connect
electronic components on a cover substrate of the electronic module
with electronic components on a base substrate of the electronic
module.
[0004] The free-formed, self-supported interconnect pillars may
provide for improved compactness of the electronic module by
establishing an electrical path to the electronic components on the
cover substrate, thereby effectively increasing the available area
for mounting such electronic components. More particularly, the
free-formed, self-supported interconnect pillars may extend
vertically between the base electronic components and the opposing
cover electronic components to provide a straight electrical path
that allows sufficient spacing between the opposing electronic
components. Such a configuration may enable improved thermal
performance and cooling between components, and also limits or
eliminates the use of substrate area for the interconnect path. In
addition, by providing a straight and/or direct electrical path
between electronic components, the configuration of the
free-formed, self-supported interconnect pillars may also enable
improved operational efficiency of the electronic module by
reducing transmission losses of the electrical signal along the
electrical path. Furthermore, the cover substrate may provide an
integrated thermal spreader, which may be combined with a heat
exchanger or thermal mass, to enhance cooling to the cover
electronic components, while also minimizing interference with
electrical connections or operations of the electronic device, such
as the radio frequency (RF) or direct current (DC) operations.
[0005] The free-formed, self-supported interconnect pillars may be
formed from an electrically conductive filament provided by a
layer-wise additive manufacturing process. By depositing the
electrically conductive filament, in situ, directly on the
electronic components, the tailorability and flexibility in module
design may be enhanced and the complexity of the interconnect
structure may be reduced. For example, the free-formed,
self-supported interconnect pillars may better accommodate for
non-planarity between electronic components disposed on the
substrates, and free-forming the self-supported interconnect
pillars may improve the speed and cost to manufacture such
electronic modules.
[0006] According to one aspect of the invention, a method for
assembling an electronic module includes the steps: (i) mounting a
base electronic component on a base substrate; (ii) mounting a
cover electronic component on a cover substrate; (iii) depositing
an electrically conductive filament directly on the base electronic
component or directly on the cover electronic component; (iv)
free-forming a self-supported interconnect pillar with the
deposited electrically conductive filament, the free-formed,
self-supported interconnect pillar extending upright from the base
electronic component or the cover electronic component; (v)
arranging the cover substrate over the opposing base substrate and
aligning the base electronic component with the cover electronic
component; and (vi) electrically connecting the base electronic
component to the cover electronic component with the free-formed,
self-supported interconnect pillar.
[0007] Embodiments of the invention may include one or more of the
following additional features separately or in combination.
[0008] For example, the method for assembling the electronic module
may further include the steps of attaching a compressible
electrical interposer at a free-end of the free-formed,
self-supported interconnect pillar, and electrically interposing
the compressible electrical interposer in the electrical path
between the respective free-formed, self-supported interconnect
pillar and the base electronic component or the cover electronic
component.
[0009] In some embodiments, the electrically conductive filament
may be an electrically conductive paste.
[0010] The electrically conductive paste may be deposited to form
the free-formed, self-supported interconnect pillar having a length
to width aspect ratio of at least 3 to 1.
[0011] The cover electronic component and the base electronic
component may each include an externally addressable face having an
electrical contact surface, where the externally addressable face
of the cover electronic component may be aligned with and
opposingly face the externally addressable face of the base
electronic component.
[0012] The electrically conductive paste may be deposited on the
electrical contact surface of the base electronic component or may
be deposited on the electrical contact surface of the cover
electronic component and may form the free-formed, self-supported
interconnect pillar in a straight path for electrically connecting
with the opposing electrical contact surface of the base electronic
component or the cover electronic component.
[0013] A plurality of the base electronic components may be mounted
on the base substrate and a plurality of the cover electronic
components may be mounted on the cover substrate, where at least
one of the externally addressable faces of the plurality of cover
electronic components is non-planar with respect to at least one
other of the externally addressable faces of the plurality of cover
electronic components, and/or at least one of the externally
addressable faces of the plurality of base electronic components is
non-planar with respect to at least one other of the externally
addressable faces of the plurality of base electronic
components.
[0014] The electrically conductive paste may be deposited on one or
more of the plurality of base electronic components and/or one or
more of the plurality of cover electronic components to form a
plurality of the free-formed, self-supported interconnect pillars
having varying longitudinal lengths for electrically connecting the
plurality of base electronic components to the plurality of cover
electronic components and to accommodate for the non-planarity of
the respective externally addressable faces of the plurality of
base electronic components and/or the plurality of cover electronic
components.
[0015] The electrically conductive paste may be deposited to form
the free-formed, self-supported interconnect pillar having a
substantially cylindrical shape.
[0016] The electrical conductivity of the free-formed,
self-supported interconnect pillar may be uniform through both a
transverse cross-section and along a longitudinal length of the
free-formed, self-supported interconnect pillar.
[0017] The electrical conductivity of the free-formed,
self-supported interconnect pillar may be about 1.times.10.sup.7
siemens per meter or greater.
[0018] The electrically conductive paste may be deposited through a
layer-wise additive manufacturing process to form the free-formed,
self-supported interconnect pillar.
[0019] Optionally, the electrically conductive paste may be
deposited in a single extrusion step to form the at least one
free-formed, self-supported interconnect pillar extending upright
from the base electronic component or the cover electronic
component.
[0020] The method for assembling the electronic module may further
include the step of solidifying the electrically conductive
paste.
[0021] The cover electronic component mounted on the cover
substrate may generate more heat than the base electronic component
mounted on the base substrate.
[0022] The method for assembling the electronic module may further
include the steps of attaching a cold plate to the cover substrate,
and cooling the cover electronic component.
[0023] The electronic module may be an RF module, and the
free-formed, self-supported interconnect pillar may be configured
to transmit RF or DC signals or transport heat.
[0024] A plurality of cover electronic components may be provided,
which may include one or more monolithic microwave integrated
circuits.
[0025] A plurality of base electronic components may be provided,
which may include one or more application specific integrated
circuits.
[0026] According to another aspect of the invention, an electronic
module includes a base substrate, a base electronic component
disposed on the base substrate, a cover substrate disposed over the
base substrate, a cover electronic component disposed on the cover
substrate, where the cover electronic component is spaced from the
base electronic component, and a free-formed, self-supported
interconnect pillar electrically connecting the base electronic
component with the cover electronic component.
[0027] Embodiments of the invention may include one or more of the
following additional features separately or in combination.
[0028] For example, the free-formed, self-supported interconnect
pillar may be formed from an electrically conductive paste.
[0029] The cover electronic component and the base electronic
component may each include an externally addressable face having an
electrical contact surface, where the externally addressable face
of the cover electronic component is parallel to and directly
opposingly faces the externally addressable face of the base
electronic component.
[0030] The free-formed, self-supported interconnect pillar may
extend between the respective electrical contact surfaces of the
cover electronic component and the base electronic component.
[0031] The free-formed, self-supported interconnect pillar may have
a length to width aspect ratio of at least 3 to 1 and may extend
upright and perpendicular with respect to each of the externally
addressable faces of the cover electronic component and the base
electronic component.
[0032] The base substrate may include a plurality of the base
electronic components, and the cover substrate may include a
plurality of the cover electronic components.
[0033] A plurality of the free-formed, self-supported interconnect
pillars may electrically connect the plurality of base electronic
components to the respective plurality of cover electronic
components.
[0034] In some embodiments, at least one of the externally
addressable faces of the plurality of cover electronic components
is non-planar with respect to at least one other of the externally
addressable faces of the plurality of cover electronic components,
and/or at least one of the externally addressable faces of the
plurality of base electronic components is non-planar with respect
to at least one other of the externally addressable faces of the
plurality of base electronic components.
[0035] The free-formed, self-supported interconnect pillars may
have varying longitudinal lengths to accommodate for the
non-planarity of the respective externally addressable faces of the
plurality of base electronic components and/or the plurality of
cover electronic components.
[0036] The electronic module may further include cooling means,
such as a heat exchanger or thermal mass, attached to the cover
substrate.
[0037] The electronic module may be an RF module, where a plurality
of cover electronic components may include one or more monolithic
microwave integrated circuits, where a plurality of base electronic
components may include one or more application specific integrated
circuits, and where one or more of the plurality of free-formed,
self-supported interconnect pillars may be configured to transmit
RF or DC signals.
[0038] The following description and the annexed drawings set forth
certain illustrative embodiments of the invention. These
embodiments are indicative, however, of but a few of the various
ways in which the principles of the invention may be employed.
Other objects, advantages and novel features according to aspects
of the invention will become apparent from the following detailed
description when considered in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] The annexed drawings, which are not necessarily to scale,
show various aspects of the invention.
[0040] FIG. 1 is a perspective view of an exemplary electronic
module according to the invention, where a cover substrate is shown
removed from a base substrate.
[0041] FIGS. 2A-2F are cross-sectional views depicting exemplary
process steps of assembling an exemplary electronic module
according to the invention.
[0042] FIG. 2A depicts cover electronic components mounted to a
cover substrate, and base electronic components mounted to a base
substrate.
[0043] FIG. 2B depicts deposition of an electrically conductive
filament through a nozzle to form independent layers of the
filament on the base electronic components.
[0044] FIG. 2C depicts deposition of the electrically conductive
filament to free-form self-supported interconnect pillars on the
base electronic components.
[0045] FIG. 2D depicts attachment of compressible interposers to
free-ends of the free-formed, self-supported interconnect
pillars.
[0046] FIG. 2E depicts alignment and attachment of the cover
substrate to the base substrate to electrically connect the cover
electronic components to the base electronic components with the
free-formed, self-supported interconnect pillars.
[0047] FIG. 2F depicts attachment of cooling means to the exterior
surface of the cover substrate.
[0048] FIG. 3 is a photograph showing an exemplary free-formed,
self-supported interconnect pillar according to the invention.
DETAILED DESCRIPTION
[0049] An electronic module, and method for making same, includes
free-formed, self-supported interconnect pillars that electrically
connect cover electronic components disposed on a cover substrate
with base electronic components disposed on a base substrate. The
free-formed, self-supported interconnect pillars may extend
vertically in a straight path between the cover electronic
components and the base electronic components. The free-formed,
self-supported interconnect pillars may be formed from an
electrically conductive filament provided by an additive
manufacturing process.
[0050] The principles of the present invention have particular
application to radio frequency (RF) electronic modules for wireless
electronic devices, and thus will be described below chiefly in
this context. It is also understood that principles of this
invention may be applicable to other electronic modules where it is
desirable to provide a three-dimensional architecture using
free-formed, self-supported interconnect pillars that enable
enhanced compactness, improved thermal and operational performance,
and increased flexibility in design and manufacturing, among other
considerations.
[0051] FIG. 1 shows an exemplary electronic module 10 having a base
substrate 12, or base, and a cover substrate 14, or lid, disposed
over the base substrate 12. The base substrate 12 includes one or
more base electronic components 16 disposed on the base substrate
12. The cover substrate 14 includes one or more cover electronic
components 18 disposed on the cover substrate 14, which may be
spaced from and/or opposingly face the base electronic components
16 (as shown in FIG. 2F, for example). One or more free-formed,
self-supported interconnect pillars 20 extend upright between the
base electronic components 16 and the cover electronic components
18 to provide an electrical path there between.
[0052] FIGS. 2A-2F illustrate an exemplary process of assembling
and/or forming an exemplary electronic module 110. The electronic
module 110 is substantially the same as, or similar to, the
above-referenced electronic module 10, and consequently the same
reference numerals but indexed by 100 are used to denote structures
corresponding to the same or similar structures in the electronic
module 10. In addition, the description relating to the electronic
module 10 is equally applicable to the electronic module 110, and
vice versa, except as noted below.
[0053] As shown in FIG. 2A, one or more base electronic components
116 are mounted on a base substrate 112. The base substrate 112 may
include a metal base, semiconductor substrate, or may include
conventional materials such as alumina, aluminum nitride, or
similar ceramic according to conventional processes using
conventional equipment, as is well known in the art. The base
substrate 112 can include a single layer or multiple layers,
including a dielectric layer and an insulating layer, formed using
conventional processes and equipment.
[0054] The base electronic components 116 may be attached to the
base substrate 112 in a suitable manner, for example, using
electrically conductive or electrically non-conductive adhesives or
solder. The base electronic components 116 may include integrated
circuits, semiconductor chips, microelectronic devices, and/or
various other active and passive electrical structures, such as
capacitors, transistors, resistors, inductors, diodes, input/output
interfaces, etc., which may be provided according to conventional
practice. The base substrate 112 may also include other
electrically conductive circuitry provided by traditional
techniques in a well-known manner, such as wire bonding or
photolithographic techniques, and the like.
[0055] Also shown in FIG. 2A, one or more cover electronic
components 118 are mounted on a cover substrate 114, thereby
effectively doubling the available area for mounting such
components inside of the electronic module 110. The cover substrate
114 and the cover electronic components 118 may be the same as or
substantially similar to the base substrate 112 and the base
electronic components 116, respectively. As with the base substrate
112, the cover substrate 114 may include various integrated
circuits, semiconductor chips, microelectronic devices, and/or
other electrical circuitry and components, which may be provided
according to conventional practice well-known in the art. The cover
substrate 114 may also be sufficiently rigid to support the cover
electronic components without distortion.
[0056] Generally, any type or number of electronic components 116,
118 can be attached to the cover substrate 114 and/or the base
substrate 112. In a preferred embodiment, the electronic components
118 that generate the most heat are mounted to the cover substrate
114, which readily enables efficient transfer of the heat from the
electronic components 118 to the exterior of electronic module 110.
The cover substrate 114 may be provided as a thermal spreader,
which may be combined with cooling means, such as a heat exchanger,
to enhance cooling of the cover electronic components 118. The
cover substrate 114 may also be configured to have a higher thermal
conductivity than the base substrate 112 for more effectively
cooling the high heat-generating components. For example, the cover
substrate 114 may be made of, or include, an electrically
non-conductive material having good thermal conductivity such as,
for example, aluminum nitride; or the cover substrate 114 may be
made of, or include, an electrically conductive material having
good thermal conductivity, such as a molybdenum-copper alloy.
Alternatively or additionally, the cover substrate 114 may be made
of a material having relatively poor thermal conductivity, such as
ceramic (e.g., alumina), and can incorporate a heat sink made of a
thermally conductive material, such as metal, for example,
copper-tungsten.
[0057] In the illustrated embodiment shown in FIG. 2A, the
electronic module 110 is configured as an RF module 110 and may
include application specific integrated circuits (ASICs) 130,
monolithic microwave integrated circuits (MIMICs) 132, other
electronic components (e.g., capacitors and/or other integrated
circuits 138), and/or other electronic circuitry (e.g., wires 134
and input/output interfaces 136) for generating, transmitting, and
receiving RF signals. In a preferred embodiment, the cover
electronic components 118 include the MMICs 132 which are mounted
to the underside of the cover substrate 114, and the base
electronic components 116 include the ASICs 130 and other
components 138. Such a configuration enables more efficient cooling
of the MMIC components 132 by providing the cover substrate 114 as
a thermal spreader, which may optionally include cooling means 180
(shown in FIG. 2F), for example a thermal mass or heat exchanger
(e.g., cold plate), that is mounted to the exterior surface of the
cover substrate 114 opposite the MMIC components 132. Such a
configuration may also reduce interference with RF operations by
limiting obstructions with RF connections to the MMICs 132, and
also by providing the cooling means 180 outside of the direct path
of RF energy transferred through the front of the phased array
antenna (e.g., toward the base substrate 112).
[0058] Turning to FIGS. 2B and 2C, an exemplary process for
producing one or more free-formed, self-supported interconnect
pillars 120 (hereinafter also referred to as "interconnect pillars"
120) is shown. The free-formed, self-supported interconnect pillars
120 electrically connect the base electronic components 116 and the
cover electronic components 118 to provide an electrical path
therebetween. The term "electrically connect" as used herein may
include either direct or indirect electrical connection between
components e.g., 116, 118. It is understood that individual
free-formed, self-supported interconnect pillars 120 may
electrically connect individual electronic components 116, 118 at
its opposite ends, and/or more than one interconnect pillar 120 may
be disposed on a single electronic component 116, 118 to connect
one or more opposite electronic components 116, 118. Although the
interconnect pillars 120 are shown in the illustrated embodiment as
being straight, they may also include a branching-type structure
that provides for electrical connection of a single interconnect
pillar 120 with multiple electronic components 116, 118 at one or
more of the interconnect pillar ends. The interconnect pillars 120
may be perpendicular to the base electronic components 116 for
electrically connecting with opposingly facing cover electronic
components 118 that may be in direct alignment with the respective
base electronic components 116. Alternatively or additionally, the
interconnect pillars 120 may be inclined with respect to the base
electronic components 116 for electrically connecting with
opposingly facing cover electronic components 118 that may be in an
offset alignment with the respective base electronic components
116.
[0059] The free-formed, self-supported interconnect pillars 120 may
be configured to transmit a variety of electrical signals between
the base electronic components 116 and cover electronic components
118. For example, where the electronic module 110 is configured as
an RF module, the interconnect pillars 120 may be configured to
communicate RF signals by receiving an RF input toward the base
substrate 112 and transmitting an RF output toward the cover
substrate 114, for example, to MMIC components 132. The
interconnect pillars 120 may also be configured to transmit direct
current (DC) between components, for example, from the ASICs 130 or
other electronic components 138 (e.g., capacitors) disposed on the
base substrate 112 to provide power and control to the MMICs 132
mounted on the cover substrate 114. In a preferred embodiment, the
interconnect pillars 120 that are configured for RF operation
(shown as RF pillars 20' in FIG. 1) are formed proximal the
peripheral edges of the base substrate 112 and/or the cover
substrate 114. In addition, the interconnect pillars 120 configured
for RF operation may have a larger cross-sectional area for
carrying more DC current without overheating. The interconnect
pillar 120 may be configured with a suitable cross-sectional area
depending on the current or RF power requirements to ensure
reliable operation.
[0060] In the illustrated embodiment, the free-formed,
self-supported interconnect pillars 120 are formed by depositing an
electrically conductive filament 140 through a nozzle 150, or
extrusion head, directly onto the base electronic components 116,
such as the ASICs 130 and/or other electronic components 138, for
example. The filament 140 may be deposited directly onto an
electrical contact surface (not shown) provided on an externally
addressable face (e.g., face 139) of the one or more base
electronic components 116. Alternatively or additionally, the
filament 140 may be deposited directly onto the cover electronic
components 118 to form the interconnect pillars 120 in a similar
manner, however, deposition and formation of the interconnect
pillars 120 on the base electronic components 116 will primarily be
shown and described for the purposes of simplicity.
[0061] In a preferred embodiment, the electrically conductive
filament 140 is made of an electrically conductive paste, which may
be deposited through a layer-wise additive manufacturing process to
form the free-formed, self-supported interconnect pillar 120, as
exemplified in FIGS. 2B and 2C. For example, the filament 140 may
be deposited as a series of single layers 142, or traces, as the
nozzle 150 moves across the substrate 112, such as from left to
right as viewed in FIG. 2B. In this manner, the free-formed,
self-supported interconnect pillar 120 may be formed layer 142 by
layer 142, extending upright and away from the base electronic
components 116, until the fully-formed interconnect pillar 120
reaches a desired dimension (shown in FIG. 2C, for example). The
term "layer" as used herein means one or more levels, or of
potentially patterned strata, and not necessarily a continuous
phase. Optionally, the filament 140 may be solidified, such as
through temperature treatment or air drying, before subsequent
layers 142 are deposited. Alternatively or additionally, the
filament 140 may be deposited in a single extrusion step to fully
form the free-formed, self-supported interconnect pillar 120
extending upright from the base electronic component 116. For
example, the filament 140 may be deposited on the base electronic
component 116, and as the filament 140 continuously flows through
the nozzle 150, the nozzle 150 may move away from the base
component 116 (i.e., upward, as viewed in FIG. 2B) to free-form a
single (e.g., cylindrical) self-supported interconnect pillar, or
other non-layered interconnect structure extending upright and
having a length greater than its width.
[0062] The additive manufacturing process for free-forming the
self-supported interconnect pillar 120 may include methods such as
Selective Laser Sintering (SLS), Stereolithography (SLA),
micro-stereolithography, Laminated Object Manufacturing (LOM),
Fused Deposition Modeling (FDM), MultiJet Modeling (MJM),
direct-write, inkjet fabrication, and micro-dispense. Areas of
substantial overlap can exist between many of these methods, which
can be chosen as needed based on the materials, tolerances, size,
quantity, accuracy, cost structure, critical dimensions, and other
parameters defined by the requirements of the object or objects to
be made.
[0063] Advantageously, the interconnect pillars 120 may be
free-formed by depositing the filament 140, in situ, directly on
the one or more electronic components 116, 118, and are therefore
not formed in a mold or via path, nor subtractively machined or
etched, nor preformed or prefabricated interconnect structures that
must be subsequently attached to the electronic components 116,
118. Accordingly, the term "free-formed" as used herein includes
formation of the interconnect pillars 120 in their unique intended
position on the base electronic components 116 disposed on the base
substrate 112 and/or the cover electronic components 118 disposed
on the cover substrate 114, and not preformed or prefabricated into
a predefined shape, nor subtractively machined or etched.
[0064] In addition, the free-formed interconnect pillars 120 may be
deposited with the electrically conductive filament 140 such that
the interconnect pillars 120 are self-supported structures capable
of extending upright without the need for extraneous scaffolding
that must subsequently be machined or etched away, and without the
need for other support structures, such as via paths machined into
the substrate, and the like. Accordingly, the term "self-supported"
as used herein includes formation of the interconnect pillars 120
such that the interconnect pillar 120 may support itself
independently along at least a majority of its longitudinal length,
and preferably entirely unsupported along a length thereof.
[0065] Such a free-formed, self-supported interconnect pillar 120
may enhance tailorability in the electronic module 110 design and
may also reduce the complexity of the interconnect structure. For
example, as exemplified in FIG. 2C, by depositing the electrically
conductive filament 140 in situ at unique intended positions on the
base electronic components 116, the free-formed, self-supported
interconnect pillars 120 may be formed with varying lengths (L) to
better accommodate for the non-planarity of the externally
addressable faces (e.g., 139) between electronic components 116,
118 that are electrically connected on opposite ends of the
interconnect pillar 120. In this manner, the size and shape of each
interconnect pillar 120 may be customized to match an individual
topology not constrained by bulk manufacturing processes and
tolerances. In addition, by depositing the electrically conductive
filament 140 to free-form the self-supported interconnect pillars
120, inessential subtractive machining or etching steps may be
reduced or eliminated. As such, the flexibility in design of such
electronic modules 110 may be enhanced and the speed, cost, and
yield to manufacture such electronic modules 110 may be
improved.
[0066] A further advantage to providing the free-formed,
self-supported interconnect pillars 120 in the manner described
above is that such a configuration may enable improved compactness
of the electronic module 110 by establishing an electrical path to
the cover electronic components 118 disposed on the increased
substrate area provided by the cover substrate 114. In addition, by
providing the interconnect pillars 120 with sufficient length to
adequately space the cover electronic components 118 from the base
electronic components 116, the thermal performance of the
electronic module 110 may be improved as the higher heat generating
components may be adequately separated from lower heat generating
components.
[0067] The free-formed, self-supported interconnect pillars 120 may
also improve operational efficiency and reduce transmission losses
of the electrical signals in the electronic module 110 by providing
straight and/or predominately direct electrical paths between the
respective electronic components 116, 118. For example, as shown in
the exemplary embodiment of FIG. 2F, the externally addressable
faces (e.g., 139) of the base electronic components 116 may be
aligned with and opposingly face the externally addressable faces
of the cover electronic components 118, such that the free-formed,
self-supported interconnect pillars 120 may be formed
perpendicularly and extend vertically with respect to the
externally addressable faces (e.g., 139) of the respective
electronic components 116, 118. Moreover, providing a straight and
vertical path for the interconnect pillars 120 may reduce
complexity in electronic module design and may limit or eliminate
the use of substrate area that would otherwise be required for the
interconnect path.
[0068] In a preferred embodiment, the free-formed, self-supported
interconnect pillar 120 has a longitudinal length (L) that is
greater than its transverse width (W) (or diameter). In particular,
the length to width aspect ratio of the free-formed, self-supported
interconnect pillar 120 is at least 2:1, preferably at least 3:1,
more preferably 5:1, and optionally 8:1 or greater, including all
ranges and subranges therebetween. Such a configuration of the
free-formed, self-supported interconnect pillar 120 may provide
adequate spacing for improved thermal performance and compactness,
may improve operational efficiency and reduce transmission losses,
and/or may enable the interconnect structure to be free-formed and
self-supported for improved manufacturing efficiency. The higher
aspect ratio may also enable a more dense interconnect structure,
thereby requiring less MMIC 132 and/or ASIC 130 footprint.
[0069] Depending at least in part on the shape of the extrusion
nozzle 150, the extruded filament 140 and/or the corresponding
interconnect pillar 120 may in some embodiments have a
substantially cylindrical shape. Because the extruded and deposited
filament 140 may undergo a settling process, or in some cases a
solidification process (for example, air-drying or thermal
treatment, such as sintering or curing) after being deposited in
the one or more layers 142 on the electronic module 116, the
transverse cross-sectional shape of the interconnect pillar 120 may
include some distortions from an exact circle. The interconnect
pillar 120 may therefore be described as having a substantially
cylindrical shape, which is defined herein as having a cylindrical
shape or a distorted cylindrical shape. Alternatively or
additionally, the filament 140 may be deposited from a nozzle 150
that does not have a circular cross-section; for example, the
transverse cross-section of the nozzle may be rectangular, square,
hexagonal, or other polygonal shape, in which case the transverse
cross-sectional shape of the interconnect pillar 120 corresponds
with the shape of the nozzle 150.
[0070] The electrically conductive filament 140 and/or the
corresponding structure of the interconnect pillar 120 may have a
diameter (or width, W) of from about 1 mil (25 microns) to about
100 mils (2.54 mm), more preferably from about 3 mils (76 microns)
to 8 mils (203 microns), most preferably 6 mils (152 microns). The
unsupported length (L) of the free-formed interconnect pillar 120,
as measured along its longitudinal axis, may be from about 5 mils
(127 microns) to about 500 mils (12.7 mm), more preferably about 10
mils (254 microns) to about 50 mils (1,270 microns), and most
preferably about 30 mils (762 microns). As discussed above, the
length (L) to width (W) (or diameter) aspect ratio of the
free-formed, self-supported interconnect pillar 120 may be at least
about 3:1, and more preferably about 5:1.
[0071] The electrically conductive filament 140, such as that made
of an electrically conductive paste, may be designed with an
appropriate chemistry and viscosity to enable the free-formed
extrusion through the nozzle 150 and to provide the self-supported
interconnect pillar structure. Preferably, the electrically
conductive paste has thixotropic shear thinning behavior that
enables the paste to be extruded through the nozzle 150 and yet be
able to retain a self-supported shape of the deposited layer 142,
or a self-supported shape of the entire interconnect pillar 120,
after exiting the nozzle 150. In addition, it may be preferable
that the electrically conductive paste has chemical compatibility
and good wetting behavior with the electronic component 116, 118
and/or the electrical contact surface on the externally addressable
face of the electronic component 116 or 118. Accordingly, the
electrically conductive filament 140 and/or the free-formed
interconnect pillar 120 may form a strong interface with the
electronic component 116, 118 or the electrical contact surface
thereof in the as-deposited state, as well as after any
post-processing, such as thermal treatment, without compromising
the structural integrity of the free-formed self-supported
interconnect structure 120.
[0072] Due to the desired functionality of the free-formed,
self-supported interconnect pillars 120, it may be preferred that
the electrically conductive filament 140 and/or the corresponding
interconnect pillar 120 exhibits a sufficiently high electrical
conductivity. For example, the electrical conductivity of the
filament 140 may be on the order of about 1.times.10.sup.7
siemensper meter, preferably at least about 2.5.times.10.sup.7
siemensper meter, and more preferably greater than 3.times.10.sup.7
siemens per meter at standard temperature and pressure. The
electrically conductive filament 140 may comprise an electrically
conductive material, such as a transition metal, an alkali metal,
an alkaline earth metal, a rare earth metal, or carbon. For
example, the conductive material may include an electrically
conductive material selected from the group consisting of: silver,
copper, lead, tin, lithium, gold, platinum, titanium, tungsten,
zirconium, iron, nickel, zinc, aluminum, magnesium, and carbon
(e.g., graphite, graphene, carbon nanotubes).
[0073] In addition, due to the interconnect pillar 120 being
engaged at its opposite ends between the base substrate 112 and the
cover substrate 114, and the electronic components 116, 118 thereof
(as shown in FIG. 2E), it may be preferable that the interconnect
pillar have sufficient compressive strength. It may also be
preferred that the interconnect pillar 120 has a coefficient of
thermal expansion similar to the module housing itself to limit
compressive stresses from accumulating in the interconnect pillar
120 as the interconnect pillar 120 heats and expands due to heat
generated by the electronic components 116, 118.
[0074] The free-formed, self-supported interconnect pillar 120 may
preferably have a substantially uniform transverse cross-sectional
width (W) (or diameter) along the entire unsupported length of the
interconnect pillar 120, however, some distortions may occur due to
settling or solidification of the deposited filament 140. It may
also preferable that the free-formed, self-supported interconnect
pillar 120 has uniform material properties, such as electrical
conductivity, through both its transverse cross-section and along
its longitudinal length. Alternatively, the interconnect pillar 120
may be a functionally graded component having varying material
properties for enabling modification or modulation of the
electrical signal as required.
[0075] FIG. 3 shows a photograph of an exemplary free-formed,
self-supported interconnect pillar 220 having a substantially
cylindrical shape. The interconnect pillar 220 was made from a
silver nanopaste that was deposited in a single vertical pass, or
trace, extending away from the base. The height (or unsupported
length, L) of the interconnect pillar 220 is about 29 mils (737
microns) and the width (W) (or diameter) is about 6 mils (152
microns), such that the length to width aspect ratio is about 5:1.
The free-formed, self-supported interconnect pillar 220 has a
relatively high electrical conductivity of about 85% that of the
electrical conductivity of gold.
[0076] Turning now to FIG. 2D, after depositing the electrically
conductive filament 140 and free-forming the self-supported
interconnect pillars 120, the exemplary process of assembling the
electronic module 110 may optionally include a step of attaching a
compressible electrical interposer 160 at a free-end 124 of the
free-formed, self-supported interconnect pillar 120. Accordingly,
when the interconnect pillars 120 electrically connect the base
electronic components 116 to the cover electronic components 118
(as shown in FIG. 2F), the compressible interposers 160 may be
electrically interposed in the electrical path. In this manner, the
interconnect pillars 120 may provide an electrical connection
between the respective electronic components 116 and 118 that is
indirect, yet the electrical path may still be provided as a
straight path.
[0077] The electrical interposer 160 may have sufficient compliance
or compressibility to accommodate for compressive engagement
between the cover electronic component 114 and the free-end 124 of
the interconnect pillar 120, which may reduce compressive stresses
on the interconnect pillar 120. The compressible electrical
interposer 160 may also have sufficient spring back to accommodate
for slight variations in the overall height of the respective
interconnect pillars 120 as the cover substrate 114 is attached to
the base substrate 116, and as the cover electronic components 118
engage the compressible interposers 160 (as shown in FIGS. 2E and
2F, for example). The compressible electrical interposer 160 may
also provide for improved contact area between the interconnect
pillar 120 and the cover electronic component 118. In some
embodiments, the compressible electrical interposer 160 may have
approximately the same width (or diameter) as the interconnect
pillar 120. The compressible electrical interposer 160 may provide
low signal losses or distortion of the electrical signal between
electronic components 116 and 118. In a preferred embodiment, the
compressible electrical interposer 160 may constitute less than 20%
of the length of the electrical path between electronic components
116 and 118 for reducing transmission losses.
[0078] The compressible electrical interposer 160 may be made from
an electrically conductive elastomeric material, such as a
silicon-based rubber having electrically conductive particles or
fibers dispersed therein. Alternatively, the compressible
electrical interposer 160 may be made from one or more electrically
conductive wires, or filaments, compacted into a compressible
interposer configuration, for example, cylindrical. The conductive
wire or filaments of the interposer 160 may be made from
gold-plated beryllium copper alloy (Au/BeCu) or a gold-plated
molybdenum alloy (Au/Mo), for example.
[0079] Referring now to FIG. 2E, an exemplary process step of
attaching the cover substrate 114 to the base substrate 112 to
electrically connect the cover electronic components 118 with the
base electronic components 116 via the interconnect pillars 120,
and optionally the compressible interposers 160, is shown. In the
illustrated embodiment, the cover substrate 114 is arranged over
the base substrate 112, and the respective cover electronic
components 118 are directly aligned with, and opposingly face, the
base electronic components 116 to electrically connect with the
vertical and straight interconnect pillars 120. As the cover
substrate 114 is lowered to attach to the base substrate 112, the
interposers 160 are compressed and simultaneously the cover
substrate 114 may engage a hermetic seal member (not shown) on the
base substrate 112 (or upright sidewalls of the base substrate 112)
to form a hermetically sealed internal cavity 170 (shown in FIG.
2F) that prevents contaminants or moisture from entering the
internal cavity 170. In this manner, all of the electronic
components 116, 118 and electrical connections therebetween (e.g.,
interconnect pillars 120), with the exception of the input/output
interfaces 136, for example, may be completely contained within the
hermetically sealed internal cavity 170. The cover substrate 114
may be fixedly attached to the base substrate 112 with a laser weld
or adhesive, for example an epoxy resin or solder, in a suitable
manner well-known in the art.
[0080] In FIG. 2F, a cooling means 180 is shown attached to the
exterior surface of the cover substrate 114 opposite the cover
electronic components 118. The cooling means 180 may be a thermal
mass, such as a block of steel, or a heat exchanger, such as a cold
plate, a chiller, or a plate-fin heat exchanger. The cooling means
180 may be used to actively or passively cool the cover electronic
components 118 by providing a direct path for thermal energy
through the cover substrate 114. Preferably, the cover substrate
114 is configured to have a relatively high thermal conductivity
for more effectively cooling the high heat-generating components.
The cooling means 180 may be mounted and attached to the cover
substrate 114 in a well-known manner using conventional methods,
for example, with the use of adhesives, such as epoxy. The adhesive
used for attaching the cooling means 180 may be configured to also
have high thermal conductivity, for example, with the addition of
thermally conductive additives.
[0081] Although the invention has been shown and described with
respect to a certain embodiment or embodiments, it is obvious that
equivalent alterations and modifications will occur to others
skilled in the art upon the reading and understanding of this
specification and the annexed drawings. In particular regard to the
various functions performed by the above described elements
(components, assemblies, devices, compositions, etc.), the terms
(including a reference to a "means") used to describe such elements
are intended to correspond, unless otherwise indicated, to any
element which performs the specified function of the described
element (i.e., that is functionally equivalent), even though not
structurally equivalent to the disclosed structure which performs
the function in the herein illustrated exemplary embodiment or
embodiments of the invention. In addition, while a particular
feature of the invention may have been described above with respect
to only one or more of several illustrated embodiments, such
feature may be combined with one or more other features of the
other embodiments, as may be desired and advantageous for any given
or particular application.
* * * * *