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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.
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.