U.S. patent application number 16/002025 was filed with the patent office on 2018-11-08 for methods of fabricating electronic and mechanical structures.
The applicant listed for this patent is Nuvotronics, Inc.. Invention is credited to Dara L. Cardwell, David W. Sherrer.
Application Number | 20180319108 16/002025 |
Document ID | / |
Family ID | 47506581 |
Filed Date | 2018-11-08 |
United States Patent
Application |
20180319108 |
Kind Code |
A1 |
Sherrer; David W. ; et
al. |
November 8, 2018 |
METHODS OF FABRICATING ELECTRONIC AND MECHANICAL STRUCTURES
Abstract
The present invention relates to the fabrication of complicated
electronic and/or mechanical structures and devices and components
using homogeneous or heterogeneous 3D additive build processes. In
particular the invention relates to selective metallization
processes including electroless and/or electrolytic
metallization.
Inventors: |
Sherrer; David W.; (Radford,
VA) ; Cardwell; Dara L.; (Pulaski, VA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nuvotronics, Inc. |
Radford |
VA |
US |
|
|
Family ID: |
47506581 |
Appl. No.: |
16/002025 |
Filed: |
June 7, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14232396 |
May 5, 2014 |
9993982 |
|
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PCT/US2012/046734 |
Jul 13, 2012 |
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16002025 |
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61507496 |
Jul 13, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05K 3/4664 20130101;
B33Y 80/00 20141201; B22D 19/00 20130101; B29C 70/882 20130101;
H05K 2201/037 20130101; H05K 1/0284 20130101; H05K 1/0274 20130101;
H05K 2201/0195 20130101; C25D 5/02 20130101; B29C 64/106 20170801;
H05K 3/1275 20130101; H05K 2201/0191 20130101 |
International
Class: |
B29C 70/88 20060101
B29C070/88; B29C 64/106 20170101 B29C064/106; B22D 19/00 20060101
B22D019/00; C25D 5/02 20060101 C25D005/02; B29C 64/00 20170101
B29C064/00 |
Claims
1-20. (canceled)
21. A method of fabricating a 3D structure, comprising: providing a
substrate having at least one integrated circuit disposed thereon;
depositing onto the substrate using 3D printing a first dielectric
material to create a first patterned layer having at least one
region in which the first dielectric material is deposited and at
least one void region in which no first dielectric material is
deposited; depositing, on the first patterned layer, a second
dielectric material to create a second patterned layer having at
least one region in which the second dielectric material is
deposited and at least one void region in which no second
dielectric material is deposited; and depositing a metal into
selected portions of one or both of the at least one void regions
of the first and second patterned layers, thereby providing a 3D
structure.
22. The method of claim 21, wherein the 3D structure is an
electronic structure.
23. The method of claim 21, wherein the substrate comprises a
circuit board.
24. The method of claim 21, wherein the substrate comprises a
nonplanar surface.
25. The method of claim 21, wherein one or both of the first and
second patterned layers have portions of differing thickness.
26. The method of claim 21, wherein the first and second dielectric
materials comprise the same material.
27. The method of claim 21, wherein the first and second dielectric
materials comprise different materials.
28. The method of claim 21, wherein one or both of the first and
second dielectric materials comprise a photoimageable material.
29. The method of claim 28, comprising patterning the
photoimageable material using a photolithographic technique.
30. The method of claim 21, wherein one or both of the first and
second dielectric materials comprise a metallization catalyst
disposed therethrough.
31. The method of claim 30, comprising etching the dielectric
material comprising the metallization catalyst to increase the
number of catalyst sites in a surface thereof.
32. The method of claim 30, comprising exposing the first and
second dielectric materials with metal-containing material to
selectively deposit metal on the dielectric material containing the
metallization catalyst.
33. The method of claim 32, wherein the metal-containing material
comprises a gas or a vapor.
34. The method of claim 21, wherein only one of the first and
second dielectric materials comprise a metallization catalyst
disposed therethrough.
35. The method of claim 34, comprising exposing the first and
second dielectric materials with a process that selectively
deposits metal on the dielectric containing the metallization
catalyst while not depositing metal on the other dielectric
material.
36. The method of claim 35, wherein the process comprises atomic
layer deposition.
37. The method of claim 21, comprising removing one or both of the
first and second dielectric materials.
38. The method of claim 21, comprising milling one or both of the
first and second layers to planarize the surface of the layer.
39. The method of claim 21, wherein the step of depositing the
metal comprises deposition by electroless metallization.
40. The method of claim 39, wherein the metal comprises copper.
41. The method of claim 21, wherein the step of depositing the
metal comprises deposition by electrolytic plating.
42. The method of claim 41, wherein the metal comprises copper.
43. The method of claim 21, wherein the metal comprises copper.
44. A method of fabricating a 3D structure, comprising: providing a
substrate having at least one integrated circuit disposed thereon;
depositing onto the substrate using 3D printing a first dielectric
material to create a patterned layer having at least one region in
which the first dielectric material is deposited and at least one
void region in which no first dielectric material is deposited;
depositing, on the first patterned layer, a second dielectric
material different from the first dielectric material to create a
second patterned layer having at least one region in which the
second dielectric material is deposited and at least one void
region in which no second dielectric material is deposited; and
exposing the first and second dielectric materials with a process
that selectively deposits metal on only one of the first and second
dielectric materials.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 14/232,396, filed Jan. 13, 2014, now U.S. Pat. No. 9,993,982,
which in turn is a 371 application of International Application No.
PCT/US2012/046734 filed Jul. 12, 2012, which claims priority to
U.S. Provisional Application No. 61/507,496 filed Jul. 13, 2011.
Each of the foregoing applications is hereby incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to the fabrication of
electronic and/or mechanical structures and components and devices
such as those used in the electronics industry. In particular, the
present invention relates to using homogeneous or heterogeneous
materials in three dimensional fabrication of electronic and/or
mechanical structures and components and devices. Additionally, the
present invention relates to selective metallization processes
including electroless and/or electrolytic metallization.
BACKGROUND OF THE INVENTION
[0003] Improved methods of fabricating electronic and/or mechanical
structures continue to drive the electronics and other industries.
More and more components are being added to devices that are
getting increasingly complex and smaller. As a result fabrication
techniques are required to provide electronic and/or mechanical
components and/or parts that have increased functionality as well
as to take up less space in the device and on substrates used in
the device. The fields of micro-mechatronics, microsensors such as
multi-axis gyroscopes, electrical circuits, and microwave and
waveguide circuits are rapidly advancing. The ability to achieve
customization in such devices and still allow them to be affordably
manufactured has remained a challenge. Most industrial shaping,
forming, and production processes achieve economy of scale only by
near direct duplication of a device. For example, consumer
electronics are affordable when making millions of complex
integrated circuits that are nearly identical. Still there are many
fields where the ability to make custom 3D parts of heterogeneous
materials has remained elusive and substantial sacrifices in
dimensional accuracy and precision, material diversity, upward or
downward size scaling, for example from microns to meters, and/or
other limitations have relegated most direct 3D manufacturing to
either be unaffordable, impractical, or find limited fields of use,
for example to make plastic prototypes for novelty, engineering
understanding, or marketing.
[0004] In micromechanics, processes to make small components often
revolve around removal rather than additive processes such as
turning or milling operations and such devices are typically made
one at a time. Alternatively, molding is used but is limited in the
complexity of the parts and number that can be made and are usually
of limited material diversity. For example, one would not expect
injection molding to make parts of plastic, metal, and ceramic in
the same molding operation. Processes that have been created to
address the fabrication of components and devices of very high
precision and accuracy traditionally revolve around
photolithographic processes and deposition and/or etching
processes. For example, in traditional thin film metallization
patterning for integrated circuits and circuit boards, temporary
photoresists are patterned on metallic layers followed by etching
of the exposed metal, then removed to leave a metallic pattern.
Alternatively, metal can be plated into the exposed areas of the
photoresist followed by removal of the photoresist and flash
etching to leave behind a metallic pattern. Thicknesses of the
patterns are limited to the thickness of the original metallic
layer, in the case of etching, and the thickness of the
photoresist, in the case of metallic plating.
[0005] Current fabrication processes include, for example,
permanent resists, generally known as photoimageable dielectrics
(PID). It may desirable that such materials have low dielectric
constants and low dielectric losses particularly when they are a
permanent part of an electronic component and/or device. They are
coated onto a substrate from either a liquid composition or by
using a dry film, indiscriminately, coating the entire substrate.
They can be used to photodefine structures wherein the PID can be
cured to become a permanent part of the electronic and/or
mechanical component and/or device. Adhesion promotion and
catalyzation of the surfaces of the cured PID may allow for metal
to be deposited onto the surfaces of the resist.
[0006] In some processes, a temporary photoresist may be metallized
or the resist may serve as a mold for the metallization; this is
followed by removal of the resist leaving behind a metal structure
with air as the dielectric. In addition, many structures require
more than one layer of dielectric material and/or conductive
materials such as, for example, metal. To create devices that have
substantial complexity, tens, hundreds, or even millions of layers
may be required depending on the size, scale, and resolution
desired. Furthermore, the use of PIDs to create such devices is
very limiting. After a layer of PID is imaged to form a structure,
a second layer, uniformly applied from either a liquid or a dry
film, has difficulty planarizing or filling the spaces in the
structure particularly if they are on the scale of the layer's
thickness or greater. A further limitation is the inability to
create structures of varying and specific desired thicknesses since
the PID can only be applied as one uniform thickness when applied
by these methods. Still a further limitation is the inability of
the PID to allow for selective metallization. Adhesion promotion
and catalyzation of the PID surfaces is non-selective so that every
exposed surface will be metallized, rather than a select set of
surfaces.
[0007] A still further limitation of the current techniques is the
inability to create structures that differ substantially in size,
functionality, and accuracy and also can provide the needed
material diversity wherein the materials have both acceptable
properties in comparison to other forming techniques currently
known--for example finding a process that can provide the
properties of metals, dielectrics, and some polymer materials that
can be achieved through means such as thin film deposition,
plating, sintering, and so on. Even without material diversity, the
materials available in the 3D printing processes themselves often
have compromised material properties compared to the material
available in bulk or through other forming methods. This is
particularly true when attempting to create multicomponent
structures in the 3D printing process. For example, the properties
of a 3D printed conductor or metallization may have unacceptably
low electrical or thermal conductivity compared to a vacuum
deposited or plated counterpart. For a dielectric such as a
ceramic, or even a polymer composition, properties such as the
dielectric constants, dielectric losses, and density may be
unacceptably compromised. Thus, it may prove unacceptably
challenging to obtain a suitable diversity of desirable materials,
having a large enough set of desirable material properties, to
create many functional devices that would be desired, for example,
that which would desirably be associated with creating a 3D printed
and fully functional version of many components populating an
electronic and/or mechanical device. For instance, to create a
circuit board, both a good electrical conductor and a good non
conductor are required in a pattern. It may also be important in
the final device that its metals or conductors are able to take a
solder based device attachment; and that its adjacent
non-conductors can withstand the temperatures associated with this
process. Finding a 3D printing process that can provide metal
properties found in plated metals and in the same process finding a
dielectric that will both suitably adhere to said printed metal and
have an acceptable decomposition temperature, chemical resistance,
and other suitable dielectric properties can be difficult with the
processes currently available in 3D printing.
[0008] The current processes are of little use when a substrate has
components or other elements already fabricated onto or into the
substrate particularly where the topology is substantially
non-planar with respect to the layer thickness. Also, many
substrates are sensitive to the solvents or heating steps that are
required in fabrication. Alternative methods of preparing these
devices with many components include molds and pick and place
processes wherein the components are made "off-line" and are
assembled later onto the electronic and/or mechanical device.
Classic examples include capacitors and resistors, and inductors as
well as magnetic components.
[0009] As can be seen, current methods for the fabrication of
electronic and mechanical structures for manufacturing electronic
and/or mechanical components and other objects are limiting. Thus,
there is a need for devices and methods of fabrication that allow
electronic and/or mechanical structures to be made with varying
sizes, thicknesses, and materials as well as the ability to be
preferentially metallized--including devices and methods that can
be utilized in a non-destructive manner when substrates are already
populated with devices.
SUMMARY OF THE INVENTION
[0010] In a first embodiment, the present application for patent
discloses and claims a method of fabricating three dimensional
electronic and/or mechanical structures by selectively depositing
at least one dielectric material, which comprises a metallizable
composition, using three dimensional printing methods and
selectively depositing metal onto the metallizable dielectric
material. The deposited dielectric material, which comprises a
metallization composition, may further be made from a
photoimageable composition and/or patterned using lithographic
processes such as, for example, contact printing, projection
printing, direct write printing, and/or other lithographic
processes.
[0011] In a second embodiment, the present application for patent
discloses and claims a method of fabricating three dimensional
electronic and/or mechanical structures by selectively depositing
at least one dielectric material, which comprises a metallization
composition, using three dimensional printing methods and
depositing at least one dielectric material which does not comprise
a metallization composition and selectively depositing a metal onto
the metallizable dielectric material.
[0012] In a third embodiment, the present application for patent
discloses and claims a method of fabricating three dimensional
electronic and/or mechanical structures as in either of the
previous two embodiments but further comprising depositing a
sacrificial material comprising a metallizable composition,
selectively metallizing the sacrificial material and removing the
sacrificial material. The sacrificial material may be comprised of
a photoimageable material that can be lithographically imaged using
lithographic processes such as, for example, contact printing,
projection printing, direct write printing, and/or other
lithographic processes. The removal of the sacrificial material may
be performed by organic solvents, aqueous solvents and/or thermal
vaporization and optionally may include mechanical assistance such
as, for example, ultrasonification.
[0013] In a further embodiment, the present application for patent
discloses and claims a method of fabricating three dimensional
electronic and/or mechanical structures by selectively depositing
one dielectric material using three dimensional printing methods,
selectively depositing a second dielectric material using three
dimensional printing methods, selectively catalyzing one of the
dielectric materials with a plating catalyst and selectively
depositing metal onto the catalyzed dielectric materials. Either,
or both, of the dielectric materials may be photoimageable and can
be imaged using lithographic processes such as, for example,
contact printing, projection printing, direct write printing,
and/or other lithographic processes.
[0014] In a further embodiment, the present application for patent
discloses and claims a method of fabricating three dimensional
electronic and/or mechanical structures of the immediately above
embodiment, but further comprising depositing a sacrificial
material comprising a metallizable composition, selectively
metallizing the sacrificial material, and removing the sacrificial
material. The sacrificial material may be comprised of a
photoimageable material and can be imaged using lithographic
processes such as, for example, contact printing, projection
printing, direct write printing, and/or other lithographic
processes. The removal of the sacrificial material may be performed
by organic solvents, aqueous solvents and/or thermal vaporization
and optionally may include mechanical assistance such as, for
example, ultrasonification.
[0015] In still a further embodiment, all of the above embodiments
are deposited in a selected plurality of layers to give a
sequential build of electronic and/or mechanical structures,
wherein the layers comprise one or more of a metal material, a
sacrificial material, and a dielectric material thereby forming a
structure above the substrate.
[0016] In the above embodiments, the three dimensional printing
methods can be, for example, stereolithography, 2-photon
stereolithography, inkjet, hot melt extrusion fabrication, and/or
selective laser sintering.
[0017] All of these embodiments and their variants may have in
common the use of a dielectric that is selectively metallizable in
conjunction and relation with a second dielectric to form mixed
metal-dielectric structures and metal-dielectric-void
structures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The foregoing summary and the following detailed description
of the exemplary embodiments of the present invention may be
further understood when read in conjunction with the appended
drawings, in which:
[0019] FIGS. 1A-1G schematically illustrate exemplary processes,
devices, and materials in accordance with the present invention
exemplified by ink jet printing or other material dispenser as but
one illustrative example of 3D-printing processes of the present
invention;
[0020] FIG. 1A, schematically illustrates two different printing
heads 10, 11 printing two different materials 12, 13 to provide
first and second structures 14, 15 on a substrate 16;
[0021] FIG. 1B schematically illustrates the case where a metal 17
is further selectively deposited onto the second structure 15 of
FIG. 1A;
[0022] FIG. 1C schematically illustrates inkjet printing of a
second structure 25 in a manner similar to that of FIG. 1A but onto
a metal layer 20 rather than directly onto the substrate;
[0023] FIG. 1D schematically illustrates the case where a metal 22
is further deposited onto the second structure 25 of FIG. 1C;
[0024] FIG. 1E schematically illustrates the case where the inkjet
deposited material of the second structure 25 of FIG. 1D has been
removed to leave a standalone metal structure 28;
[0025] FIGS. 1F and 1G schematically illustrate a method and
resulting structure similar to that of FIGS. 1C-1D but having a
sacrificial material 18 disposed on the second structure 25
preventing metallization at the location of the sacrificial
material to provide a release hole to assist in the removal of the
second structure 25 after metallization;
[0026] FIG. 2 schematically illustrates using hot melt extrusion
fabrication as an illustrative example of 3D-printing processes,
devices, and materials of the present invention, wherein a printing
head 30 deposits material 33 onto substrate 35;
[0027] FIG. 3 schematically illustrates an exemplary process of
stereolithography as an illustrative example of 3D-printing
processes, devices, and materials of the present invention, in
which a substrate 30 is placed in a bath 32 containing a liquid
monomer 34 and an exposure device 36 exposes the monomer to curing
radiation 38 to give cured structures 40 which steps may be
repeated many times to create a 3D structure;
[0028] FIGS. 4-16 schematically illustrate cross-sectional views of
an exemplary 3D printing process and structure in accordance with
the present invention for the fabrication of a three dimensional,
multilayered, coaxial cable;
[0029] FIGS. 17-29B schematically illustrate cross-sectional views
of an exemplary 3D printing process and structure in accordance
with the present invention for the fabrication of a three
dimensional, multilayered, coaxial cable; and
[0030] FIG. 30 schematically illustrates an alternative support
structure for use in the structure of FIG. 16.
DETAILED DESCRIPTION OF THE INVENTION
[0031] The present invention relates to processes and devices
created, at least in part, utilizing three dimensional (3D)
additive build manufacturing as a way to create 3D objects by going
from a computer or digital design of the 3D object to the object
itself from this digital information. In one of its aspects, the
present invention relates to simple and complex electronic and/or
mechanical structures and processes for their formation. In one
notable aspect, the present invention relates to devices having
conductive structures with tolerances and accuracy on the micron
scale, such as microwave and waveguide circuits. In this regard,
the present invention provides novel methods for creating such
conductive structures via 3D additive build manufacturing while
overcoming present difficulties in providing conductive structures
of small dimension and high tolerance and having suitable bulk
electrical and thermal conductivity properties made via 3D additive
build manufacturing. In particular, the present invention may use
selective metallization processes and materials in conjunction with
non-conductive structure(s) provided by 3D additive build processes
described below to provide micron scale accuracy conductive
structures within a multi-structure and/or multi-component device
environment, for example. As used herein, "selective metallization"
connotes the ability for one material to take or bind to a
metallization process or to a metallization catalyst with respect
to a second material which does not so take or bind when both are
exposed to the same metallization process. Thus, selective
metallization permits selected structures to be metallized while
other structures within the overall device/system architecture are
not. A number of motivations for this selectivity have been
discovered.
[0032] One motivation is that some of the highest accuracy and
tolerance 3D printing methods such as stereolithography tend to be
formed from light solidified monomers or polymers. Even if one used
electrically conductive polymers however, they are not typically
able to provide bulk conductivity of a dense metal such as silver
or copper. While it is possible to coat most plastic surfaces with
a metal--for example by electroless plating--it is not possible to
use current techniques with precision to choose where metal will
and will not be coated except in the case of a planar and smooth
exterior of sufficient dimensions, for example with additional
masking. Thus, in accordance with the present invention the
desirability of having a deposited material with near
bulk-conductivity grow and adhere where desired, or through other
means such as later stage thermal processing, is recognized.
[0033] Turning to the different technologies available for
performing additive manufacturing or 3D printing, 3D additive build
manufacturing has come to include additive manufacturing methods
such as Selective Laser Sintering (SLS), and StereoLithography
(SLA), and micro-stereolithography. Other additive manufacturing
methods include Laminated Object Manufacturing (LOM), Fused
Deposition Modeling (FDM), and MultiJet Modeling (MJM), and Inkjet.
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. In addition, 3D additive build
manufacturing has come to be known by a variety of names, including
3D printing, for example. Thus, as used herein the terms "3D
additive build manufacturing" and "3D printing" are used
interchangeably.
[0034] Three dimensional (3D) printing is a form of additive
fabrication or additive manufacturing technology wherein a 3D
object is created by laying down or forming successive layers of
material at precise positions. Thus inkjet, fused deposition, and
multij et would all be forms of 3D printing. 3D printers have the
ability to print structures made of several materials with
different mechanical and/or physical properties in a single build
process, and operate by taking a 3D computer file and constructing
from it a series of cross-sections taken in the build direction.
Each cross-section layer is then printed one on top of the other to
create the 3D objects. (When the term "layer" is used herein, it
means one or more levels or of potentially patterned strata and not
necessarily a continuous plane.)
[0035] Alternatively, a 3D printer can create a 3D object from an
extrusion of a liquid that is solidified by either a change in
temperature or a chemical change, for example, such as melting or
polymerization. Thus, while a layer-wise build may be used in some
instances, a vector-based build where 3D motions both in and out of
a plane are determined based on the part to be made, machine
physics, material chemistry, and other manufacturing considerations
can also be used. In plane rastering and out of plane motion of a
"print head" supplying a material, or for the same "print head",
adjusting the 3D coordinates of a critical focal volume of light
within a photosensitive liquid and (thereby converting it in that
location to a solid "voxel") are both methods where, through motion
and repetition, a 3D object of some target physical dimensions,
shape, and size can be formed.
[0036] A number of different technologies are available for
performing 3D printing. Their main differences are in the way
layers are built to create objects. Some methods use melting or
reflow to produce the layers such as in "selective laser sintering"
wherein one or more lasers selectively fuse particles from a bed of
particles. After each cross-section is created, a new layer of
powder is applied to the top and the processes repeated until a
desired 3D structure is obtained. Depending on desired properties,
each layer of powder may be the same, or a layer of different
powder may be applied. Each powder layer may be uniform or the
layer can be sectioned with differing materials, thus providing the
capability of obtaining objects with differing characteristics
and/or functionalities. This technique is also useful for producing
fused plastic layers and/or plastic objects or metal layers and/or
metal objects or ceramic layers and/or ceramic objects. For
metallic structures, a bed of metallic powder is provided followed
by exposure to a laser. For many functional objects in electronics
and in mechanics, a combination of materials that include more than
one of metal, ceramic, plastic, semiconductor, and others would be
desirable. Thus it is desirable in such a process to control
factors such as stress, shrinkage, CTE, material cohesion and
inter-material interface adhesion in constructing or building such
a 3D device of highly heterogeneous material types.
[0037] Another method in additive manufacturing through 3D printing
is "hot melt extrusion fabrication" wherein materials, supplied as
pellets and/or a filament may be liquefied and deposited by one or
more extrusion heads. The pellets and/or filaments may be the same
or different and may be melted and mixed prior to or during
extrusion.
[0038] Other methods include application of liquid materials that
are cured with different technologies, including inkjet printing.
In the case of 3D structures, the "inkjet" may deposit layers, for
example, from a micron to tens of microns or more in thickness in
each layer. The layer may be cured as the process proceeds, for
example, by drying. Alternatively, in one part, inkjet printing
layers can be applied and cured one layer at a time. One or more
printing heads, using similar or different materials, can be used
to build structures on a substrate. Another inkjet printing
technique is to inkjet a binder onto a bed of powder to bind the
powder into a solid layer. The process continues until the desired
3D object is obtained.
[0039] Another method of additive manufacturing using liquid
materials is stereolithography wherein a vat or layer of liquid
polymer is exposed to a light. The exposed regions of liquid
polymer harden into solid layers. The substrate upon which the
solid layer region was fabricated is then moved down in small
increments and the liquid polymer is again exposed to light. The
process repeats until the model is built. The liquid polymer is
then drained from the vat, leaving the solid model. This method
also allows for replacing the liquid polymer with a different
liquid polymer at various stages during the building process, thus
allowing for the use of different materials for different
applications and with different properties.
[0040] Other techniques include 2-photon stereolithography in which
a 3D structure is obtained using one focused laser to create a 3D
gel. This is followed by a second laser that cures the desired
sections of the gel into a solid, with the uncured gel being washed
away.
[0041] Materials useful for the 3D fabrication of electronic and/or
mechanical structures, include, but are not limited to, dielectric
materials, for example, ABS, polyacrylates, BCB, polyimides,
polyamides, polyurethanes, polyesters, polycarbonates,
polysulfones, polysilicon materials and other materials known in
the art to be useful as dielectric for fabrication of electronic
and/or mechanical structures. While polymers may be most easily
deposited materials using current 3D printing techniques,
semiconductors, ceramics, and metals are typically found in
electronic components. Selective laser sintering is one of the only
additive manufacturing techniques that currently provides near bulk
density metals, however its accuracy and resolution are low
compared to jet deposited or extrusion deposited 3D printers. These
materials however can be 3D printed as a mixture such as a
nanomaterial paste or composition in a binder. 3D printing
techniques that have a direct thermal component such as laser
sintering can often provide a final structural material; however,
other approaches such as baking the final printed structure to
remove binders and certain polymer components could be equally used
to obtain the final desired material properties. For instance, a
polymer could be heat treated to remove solvent and leave behind a
solid, or a polymer-ceramic composite could be heat treated to
decompose the polymer and leave behind a ceramic. The materials may
be used alone or may be formulated into inkjet compositions, or as
meltable solids for hot melt extrusion application, or as
monomeric, polymeric, or mixtures of materials for
stereo-lithographic applications.
[0042] Other useful materials may be applied by additive
manufacturing or 3D printing processes and further processed in a
curing step, for example, epoxy, novolac, melamine, glycidyl ethers
of poly-bis-phenol A, or combinations thereof, and other
crosslinking systems which require a thermal cure, a photo cure or
a combination thereof. In some of these materials, one or more
curing catalysts aid in the curing step, for example, photoacid
generators, thermal acid generators, photobase generators and/or
thermal base generators. Depending on the desired properties the
materials for 3D printing may be combined into one or more useful
printing compositions.
[0043] In some embodiments, the compositions for 3D printing or
additive manufacturing comprise a "metallizable composition". These
compositions may contain or may selectively bind to metallization
catalysts, which allow for the deposition of metal using wet
chemical processes or gas phase processes. Metallization catalysts
include, for example, palladium-tin alloys which are activated to
palladium catalyst during processing. Other catalysts include
organic palladium materials which may be activated to palladium
catalyst by thermal or chemical or plasma treatment. In some cases,
a metallization precursor may be included in the dielectric being
deposited. In some cases a material is chosen that can readily
adsorb or absorb or bind to a catalyst from a solution in relation
to a second material that does not absorb or adsorb or bind to the
catalyst. In this embodiment, the material is deposited, the
material may optionally be etched and may be optionally exposed to
an additional step to concentrate the catalyst such as a plasma
etching step that selectively removes a small amount of the polymer
or binder material and leaves the catalyst. Further processing
needed to activate a catalyst such as a palladium chloride
composition, like exposure to a reducing agent, is known in the
art. The material can then be plated.
[0044] In other embodiments, the printing compositions may comprise
photoimageable materials. For example, a photodefinable dielectric
material, for example, glycidyl ethers of poly-bis-phenol
A/photoacid generator systems, can be applied by 3D methods
followed by further processing using photolithographic techniques
such as, for example, exposing the material to actinic radiation
through a photomask and removing any unexposed material using a
suitable developer solution. This method could allow a two-fold
patterning process, the first being the pattern provided by the 3D
deposition, the second being a photolithographic process, and may
provide more versatility in manufacturing a 3D structure. Other
photolithographic materials may also be used for example, acrylate
systems, BCB systems, silicon based systems and/or novolac
systems.
[0045] Using, for example, electroless metallization processes
known in the art, metal may selectively be deposited, for example,
copper, nickel, gold, tin, zinc, silver, palladium, tin, lead,
aluminum, chromium and/or alloys. In some embodiments, the
composition containing the metallization catalyst has its surface
etched back to remove some of the non-catalytic dielectric
material, thereby increasing the number of catalyst sites in the
surface of the composition potentially allowing for improved
plating. For example, etching steps to concentrate catalysts on a
surface of the metallizable plastic may include plasma processes
such as, for example, plasma etching in the presence of oxygen or
may include wet chemical etching.
[0046] Other dielectric materials not containing metal catalysts
may be deposited along with catalyzed dielectrics. These can be
deposited at the same time when using inkjet or hot melt extrusion
printing by employing more than one printing head and/or
sequentially such as, for example, with stereolithography where in
one material is deposited from a liquid composition, the
composition flushed and replaced by a second liquid composition
which is then deposited. This allows for selective metallization
wherein selected structures are metallized while other structures
are not.
[0047] To date, entire 3D printed plastic models have been
metalized using plating on plastic techniques such as electroless
plating and/or electroless plating followed by electrolytic
plating; however, methods to selectively enable the formation of
metalized regions along with non-metalized regions wherein the
regions that become metal are defined by the materials deposited
have not been demonstrated. This is in contrast with a patterned
metallization in which an additional masking material such a resist
or paint is applied to the object to create a metal pattern. In
other embodiments, two dielectric compositions may be deposited
onto a substrate using 3D printing methods, wherein only one of the
dielectric compositions can be catalyzed with a plating catalyst
and subsequently plated and the other does not take to or have the
catalyst incorporated and so does not plate in the same
metallization process. One way this can be achieved when one of the
dielectric compositions has surface characteristics that allow a
plating catalyst to adhere to it, while the other dielectric
composition does not allow the catalyst to adhere. Examples of such
adherent surfaces include surfaces with, for example, carboxylic
acid, hydroxy and/or other highly polar groups on the surface
and/or the surface may be porous allowing catalyst to be captured
in the pores.
[0048] Alternatively, one of the dielectric compositions may be
treated with conventional plating on plastic processes, for
example, slight swelling and etching of the dielectric followed by
contact with a catalyst bath where the catalyst becomes adherent to
the dielectric. The treated dielectric then is plated in a plating
bath. The other deposited dielectric is selected such that it is
not affected by the catalyzing and therefore the plating processes.
Plating of the selected dielectric may be performed for example by
electroless plating processes and/or by a combination of
electroless plating followed by electrolytic plating, for example.
In the above plating processes, it can be seen that the embodiments
of the current disclosure provide for select plating and
non-plating of the deposited 3D structure.
[0049] The selective metallization may also occur by a gas or vapor
phase reaction, for example in atomic layer deposition (ALD), a
polar material may allow a series of gas phase reactions that
metalize a surface were as a non-polar material may not start a
reaction.
[0050] In addition to 3D printing or additive manufacturing of
permanent dielectric materials, metallizable or otherwise, the
present invention includes the 3D printing of sacrificial materials
along with one or more of the metallizable dielectric and the
non-metallizable dielectric. For example, the 3D printed materials
may be used to provide both a sacrificial scaffolding, for example,
a starch, and a permanent material, for example, ABS. In this case,
the final object is obtained when the sacrificial scaffolding is
dissolved or otherwise removed. While parts entirely made of
dielectric materials are useful in certain applications, other
products, especially electronic and/or mechanical structures,
benefit from having a mixture of metal and dielectrics available
which may be combined with nearly arbitrary complexity,
particularly when combined with a sacrificial material that can
provide a space or void where desired.
[0051] Thus typically three materials may be used, a sacrificial
scaffolding material that can be dissolved after printing, and two
materials one selectively metallizable in reference to the second,
which remain intact during the process which removes the
sacrificial scaffolding material. Subsequently, the metallizable
material may be metallized during a metallization step, after which
the selectively metallized material may optionally be removed in a
second removal step. If the material is optionally removed, it may
be desirable to ensure the metal is deposited to a thickness such
that it can be free-standing. In some cases it may be desirable to
have a dielectric, a metal, and a void structured in arbitrary and
determined complexity in the final structure. Merely coating a
dielectric, such as a selectively metallizable plastic, with a
metal coating may not be desirable. A metal encapsulated dielectric
may for example fail under temperature cycles due to a mismatch
between the metal and dielectric properties, and therefore one may
prefer to remove the metallized dielectric from the metal coating,
similar to the removal of sacrificial materials that can serve as
scaffolding. Thus one may choose 3 or 4 materials to realize such a
device: a selectively metallizable dielectric, a second dielectric
that does not become metallized in the same process, the metal that
becomes coated on the metallizable dielectric, and optionally a
scaffolding material. Typically, the scaffolding material is
removed, then metal is deposited selectively on one of the two
dielectric materials, and then the metallized dielectric material
may also be optionally removed by a final removal process, leaving
a desired metal, air, dielectric structure.
[0052] Materials suitable as sacrificial materials can be printed
using 3D techniques. Such materials are platable using the
techniques described above, that is, they contain plating catalysts
and/or can be swell/etched/catalyzed, and/or can be readily removed
to leave behind a full or partial metallic structural element. Such
materials include, for example, polyacrylates, polycarbonates,
cellulosic materials, and other materials capable of being removed
by a remover. Removers include organic solvents, for example,
glycol ethers, glycol ether acetates, alcohols, esters, ethers,
ketones, halogenated solvents, DMF, DMSO and the like; aqueous
solvents such as acids and bases ranging in pH from about 0 to
about 13 with or without surfactants and/or emulsifiers; and/or
thermal vaporization, and/or combinations thereof. The sacrificial
materials may dissolve, emulsify, particulate, depolymerize, and/or
become gaseous. Additionally, mechanical assistance, for example
ultrasonification, may also be used. The selectivity of the
removers and the removal process require that the dielectric
materials are not affected during the removal process.
[0053] The current application also discloses depositing
metalizable dielectrics, non-metalizable dielectric materials and
sacrificial materials in a plurality of layers. The versatility of
3D printing allows a deposition of a variety of sequences of layers
based on the electronic and/or mechanical structural requirements.
For example, 3D-MERFS and PolyStrata.RTM.-like devices can be
prepared by the disclosed methods. See U.S. Pat. No. 7,012,489,
U.S. Pat. No. 7,649,432, U.S. Pat. No. 7,948,335, U.S. Pat. No.
7,148,772, U.S. Pat. No. 7,405,638, U.S. Pat. No. 7,656,256, U.S.
Pat. No. 7,755,174, U.S. Pat. No. 7,898,356, U.S. Pat. No.
8,031,037, US 2008/0199656 and US2011/0123783, 2010/0296252,
2011/0273241, 2011/0181376, 2011/0210807 for examples of devices
that can be prepared using the currently disclosed methods, the
contents of which patents and published applications are
incorporated herein by reference.
[0054] In some embodiments, materials can be mixed in a reservoir
prior to the printing of the material. This is particularly useful
for materials that are highly reactive so that two materials may
start to react with each other as they are being printed. In this
manner, viscosity can build up quickly to help form a solid layer
when the layer is applied.
[0055] Two printing devices may work in concert with each other so
that two parts of highly reactive materials can be printed
simultaneously and begin reacting immediately, such as, for
example, an epoxy novolac layer is printed from one printing device
and an acid is printed by a second printing device directly onto
the epoxy novolac layer. As soon as the acid comes into contact
with the epoxy, a crosslinking reaction occurs.
[0056] In other processes, some layers can be cured by heat and/or
light, so that some of the printing heads can be replaced by or
used in conjunction with heating elements and/or light emitting
elements which may be applied to a layer which has been deposited.
In this manner, the layers may be selectively cured or allowed to
remain uncured, suitable for further processing.
[0057] The electronic and/or mechanical structure may be deposited
on a variety of different surfaces since the process is not
dependent on coating processes that are typically required. Thus, a
planar or nonplanar surface may be used to deposit the layers.
Surfaces which are partially or fully populated with electronic
devices and/or components may also be used and fabrication can take
place on these surfaces, which is difficult to achieve with current
conventional methods.
[0058] The method for building electronic and/or mechanical
structures may include depositing materials using conventional
deposition processes, including, for example, spin coating,
lamination, dip coating, curtain coating, slot coating, spray
coating, off-set coating and the like. It may be desirable to
planarize the structures after every layer or periodically, or
provide selective removal steps during the processing of one or
more layers. To that end, other conventional processes may also be
included, for example, chemical-mechanical-polishing, lapping,
mechanical machining, diamond turning or other precision turning,
milling, grinding, plasma etching, laser ablation, and/or
combinations thereof.
[0059] The 3D printing process can provide structures of different
shapes and/or different heights, as well as structures that have
cavities and/or walls into which discrete components may be placed
later during manufacturing.
[0060] The current application for patent is not restricted to size
such that objects from microns to meters can be fabricated using
these methods and is primarily only limited by the resolution
capabilities of the print head or the scale of the printer.
Additionally, the substrate used for deposition may function only
as a support onto which the objects, and all its embodiments, are
printed, such that the substrate may later be removed providing a
stand-alone object with selectively metallized portions on the
object.
[0061] Turning now to FIG. 1A, as an illustrative example of
3D-printing processes of the present invention, printing heads 10,
11 are provided which may deposit droplets of first and second
materials 12, 13 to form first and second layered structures 14, 15
on a substrate 16. As used herein, the term "droplets" may refer to
liquids, solids, e.g., powders or nanoparticles, or combinations
thereof, such as a suspension or slurry, for example. "Droplets"
may be of a volume of picoliters to milliliters depending on the
dimensional size, tolerances, and complexity of the device being
fabricated. The first and second materials 12, 13 may have the same
or different composition, and the printing heads 10, 11 may be the
same or different, depositing different sizes and/or shapes of
droplets as desired. Although FIG. 1A illustrates two printing
heads 10, 11, more than two printing heads may be used, each of
which may deposit materials simultaneously and/or sequentially. In
addition, a single printing head 10 may be used to deposit each of
the first and second materials 12, 13. The printing heads 10, 11
and the substrate 16 are typically moved relative to one another
using linear motors, gantry robotic systems, SCARA robotic systems,
electrostatic deflection of the particles, raster scan printing
motion, or other relevant techniques, for example.
[0062] The printing heads 10, 11 may deposit layer upon layer until
a desired thickness of structure is obtained. In some processes,
the printing heads 10, 11 may provide multiple materials by
switching from one material to another during the process, and
differing ones of the multiple materials may be printed over each
other to provide complex patterns. When layers are printed over
each other, openings may be left in the layers to allow solution
flow into and out of the structure formed of the layers.
[0063] The substrate 16 may comprise any surface useful in forming
an electronic and/or mechanical device including, for example,
silicon materials, ceramic materials, glass materials, metal
materials, integrated circuit containing semiconductor materials,
circuit board materials, RFID substrates and the like. It may for
example be a SiGe or InP wafer containing integrated circuits. The
substrate 16 may be flat or, because of the versatility of the
process, may be populated with components and/or structures that
are already resident on the substrate 16. The substrate 16 may be a
permanent part of the end product or it may be a temporary platform
on which the structures are grown and/or removed and/or detached
using, for example, a sacrificial layer.
[0064] FIG. 1B illustrates the selective metallization of the
second layered structure 15 with a metal coating 17, which can be
achieved by electroless plating techniques, electrolytic techniques
and/or direct plating, for example. In some applications, one or
more of the materials 12, 13 may contain conductive polymers such
as, for example, polythiophene, polypyrrole and/or polyaniline.
Conductive materials may also include, for example, graphene,
carbon, nanocarbon constructions and/or other materials, including
non-metals, which may be useful as electroplating conductors.
[0065] Alternatively or additionally, one of the materials, e.g.,
material 13, may contain plating catalysts. The catalysts may
include one or more of palladium/tin colloid and/or their chloride
salts, for example. After the printing process is complete (e.g.,
FIG. 1A), the substrate 16 containing layered structures 14, 15 may
be immersed in a commercial activating solution which for example
reduces a tin salt or palladium salt to elemental palladium and/or
tin in the optionally catalyst-containing second material 13. The
substrate 16 may then be immersed in a commercial electroless
plating bath and operated to obtain a desired metal thickness. In
some embodiments, it may be advantageous to etch the surfaces of
the catalyst-containing second material 13, allowing more of the
catalyst to be on the surface for contact and reaction with the
electroless plating materials. Etching can be performed in liquid
baths such as, for example, strong alkali materials which have some
sensitivity to strong alkali, or the materials may be plasma etched
for example in an oxygen containing plasma as described above.
[0066] Turning to a further exemplary structure and method of the
present invention, FIG. 1C illustrates a process similar to that of
FIG. 1A in which printing heads 10, 11 deposit droplets of first
and second materials 12, 13 to form first and second layered
structures 24, 25 on a substrate 26; however, a metal layer 20 is
provided on the substrate 26 at the location in which the second
structure 25 is to be deposited. A metal 22 may be further
deposited to the exposed surfaces of the second structure 25, in a
similar manner described above with regard to the metal 17 of FIG.
1B, allowing the second structure 25 to be completely surrounded by
metal 22, FIG. 1D. Subsequently, the second deposited material 13
comprising the second structure 25 may be removed to leave a
stand-alone, 3D metal structure 28, FIG. 1E. As described above,
the deposited second material 13 may be removed by one or more of
dissolution, thermal vaporization, polymer deconstruction, and
other suitable methods. The dissolution of the second structure 25
may be enhanced by printing an additional sacrificial material 18
over a portion of the second structure 25 so that a selected region
of the second structure 25 is not metallized to form a "release
hole", FIGS. 1F, 1G. This additional sacrificial material 18 may be
stripped selectively revealing an unmetallized region of the second
structure 25 which may then be dissolved and/or otherwise removed
from the metal shell 29. The additional sacrificial material 18 may
be the same or different from a sacrificial material 25 and/or may
be a thin layer of a dielectric that selectively does not metallize
under the conditions of second structure 25. The next step from
FIG. 1G then would be for it to look similar to FIG. 1E if the
option to remove the materials of 18 and 25 is chosen.
[0067] As mentioned, materials which are suitable for depositing
can range from dielectric materials such as, for example,
polyimides, polysulphones, polysilanes, and the like, as well as
polyacrylates. Depending on the desired structure of the fabricated
electronic and/or mechanical device, temporary materials may also
be used such as, for example, waxes, solvent soluble materials
and/or aqueous solution soluble materials. These materials can be
important when the final fabricated device has air gaps or voids as
shown in FIG. 1E.
[0068] FIG. 2 illustrates another exemplary process for depositing
materials for electronic and/or mechanical structures using hot
melt extrusion fabrication techniques wherein a printing head 37
deposits material 33 onto substrate 35. As with the inkjet printing
technique discussed above, there may be more than one printing head
depositing more than one material at the same time or at different
times. The material that feeds into the printing head may be
changed during the process to allow deposition of different
materials from the same printing head. Alternatively or
additionally, multiple print heads containing different materials
may be used in sequence or in parallel. In this process, materials
are pre-heated, and/or may be premixed with other materials prior
to deposition.
[0069] FIG. 3 illustrates stereolithography as a further exemplary
process for creation of 3D structures of the present invention. A
substrate 30 is placed in a bath 32 containing a curable material,
such as a liquid monomer or liquid polymer 34. An exposure device
36 exposes the monomer to curing radiation 38, which may be, for
example, ultraviolet radiation to provide a cured layer pattern 40
at selected locations on the substrate 30. After the layer pattern
40 is deposited, the substrate 30 may be submerged further into the
bath 32 to a chosen level, and a new liquid layer cured on top of
the substrate 30 and/or portions of the existing layer pattern 40.
The exposure may be repeated with each new layer adhering to
previous layers 40, and the substrate 30 again submerged further
into the bath 32. The process may continue until the desired 3D
structure is created. The liquid monomer 34 may be drained and
replaced with a different material during the process allowing for
the use of more than one type of material for the building of the
structure. Additionally, there may be more than one exposure unit
36 exposing the liquid monomer 34 at the same or different
times.
[0070] Turning now to FIGS. 4-16, an exemplary process of the
present invention is illustrated using an inkjet process as an
example of a 3D additive build process of the present invention in
the fabrication of a three dimensional, multilayered, coax cable
78, FIG. 16. It is to be understood that other suitable 3D
manufacturing techniques may also be used instead or in
combination, but inkjet printing has been shown merely for purposes
of illustration and not limitation.
[0071] A substrate 50 is provided having the bottom metallic wall
52 of the coaxial waveguide conductor cable 78 disposed thereon,
FIG. 4. A sacrificial material 54a, 54b may be deposited by 3D
inkjet printing 56, or other suitable 3D additive build process, in
a desired pattern to define a location 53 of a lower portion of the
coax sidewall 68 (cf. FIG. 16) and a pocket 55 for additional
desired structure(s) and/or devices, such as a non-conductive
support post for a central conductor 69 of the coax cable 78, FIG.
5. A passivation layer 58 may then be deposited in the pocket 55,
FIG. 6 . The passivation layer 58 may be non-conductive and prevent
metal plating on the passivation layer 58. Metal plating, or other
suitable metallization processes, may next be performed to fill the
location 53 with metal to provide a lower sidewall portion 60a
disposed in continuity with the bottom metallic wall 52, FIG. 7.
Again, planarization techniques may be included here to planarize
the uppers surfaces 61 to remove excess metal which might be
deposited due to overplating. Planarization in this and/or any of
the steps requiring planarization may be achieved by one or more of
CMP, lapping, polishing, grinding, diamond turning, lathe turning,
milling, and the like. This may optionally be done instead after
the next step for the support post, or may optionally be done at
any step if and as needed.
[0072] A support post 62 may be deposited by inkjet printing a
non-conductive material 63, such as any of the above mentioned
dielectric materials, over the passivation layer 58 to provide
support for the central conductor 69 of the coax cable 78, FIG. 8A.
Planarization may optionally be used at this stage to provide a
level surface, although adjustments may be made in the printing
process to allow for any over deposition. While deposition of
passivation layer 58 and support post 62 are shown here as
comprising two separate materials and steps, the passivation layer
58 and support post 62 may comprise the same material, such as a
non-metallizable material, and may be formed in one deposition or
forming step.
[0073] Optionally, while material 62 in FIG. 8A is shown as a
support post material being deposited on the non-conductive layer
58, an object 65 may be inserted instead in the pocket or recess
area 55, FIG. 8B, to realize devices other than the coax example
illustrated in FIGS. 4-16. For example, the object 65 may include
one or more of a chip (integrated circuit), a magnet, and a ferrite
and could be inserted in the pocket 55. For example, a material or
device that is not compatible with the utilized 3D additive build
process, e.g., due to chemical or thermal requirements, or a device
that needs more or less processing than the 3D additive build
process allows could be inserted. The object 65 could be bonded to
the passivation layer 58 and/or the bottom metallic wall 52 under
the passivation layer 58 by one or more means such as, for example,
a conductive or non-conductive adhesive, or the object 65 could be
mechanically locked in place by subsequent deposition steps. Any
suitable means such a pick and place, manual insertion, or
self-assembly in a fluid using electrostatic attraction could be
used to incorporate the device/object 65.
[0074] Resuming the coaxial build example, sacrificial material
64a, 64b may be deposited by 3D inkjet printing, or other suitable
3D additive build process, to define a location 66a of an
intermediate portion of the coax sidewall 68 and a location 66b of
the central conductor 69, FIGS. 9, 16. Since the support post 62 is
non-conductive, a seed layer 67 that allows plating to occur on the
support post 62, such as a metallization catalyst, or conductive
thin film, may be deposited by inkjet printing, FIG. 10. Metal
plating, or other suitable metallization process, may next be
performed to fill the location 66b with metal to provide a center
conductor 69, and to fill location 66a with metal to provide an
intermediate sidewall portion 60b disposed in continuity with the
lower sidewall portion 60a, FIG. 11.
[0075] Sacrificial material 70a, 70b defining the location 71a of a
top portion of the sidewall 68 and a location 71b of a top layer of
the outer conductor 79 of the coax cable 78 is now deposited, FIGS.
12, 16. Note that, due to the versatility of the 3D additive build
processes of the present invention, the thickness of 70a may be
than then thickness of 70b so that plating of the top layers of the
sidewall 68 and a top layer of the outer conductor 79 can occur
concurrently.
[0076] Dissolution plugs 72 may optionally be deposited via inkjet
printing at selected location(s) on the surface of the sacrificial
material 70b, FIG. 13. The plugs 72 may be composed of material
that does not plate with metal and can be removed at a later time
to reveal holes in the top of the complete coax cable 78 allowing a
passageway for the sacrificial material 54b, 64b, 70b to pass
during a removal process. A seed layer 74 may be deposited on the
sacrificial material 70b allowing the top layer of the sacrificial
material 70b to be plated in all the areas except where the
dissolution plugs 72 are located, FIG. 14. Plating may then be
performed to provide the top of the sidewall 60c and the top layer
76 of the coax cable 78, FIG. 15. Subsequently, the sacrificial
dissolution plugs 72 and the sacrificial material 54a, 54b, 64a,
64b, 70a, 70b may be removed using suitable dissolution methods,
such as those described herein, to provide for a coax cable 78,
FIG. 16. The dissolution plugs 72 may be provided at any suitable
location, including for example, in the sacrificial material 54a,
64a, 70a. The holes provided by the dissolution plugs 72 may be in
locations and of a size and shape to minimize disruption of the
desired electrical properties.
[0077] It should be noted that all the coating steps in this
exemplary process were 3D additive build processes. Moreover, while
plating was used as a method to obtain near bulk metallic
properties in the 3D build, one or more of the plating steps could
be replaced by a 3D printing step if suitable material properties
needed can be obtained. Alternatively or additionally, as
illustrated in the following example, conductive structures may be
provided via metallization of selected non-conducting structures to
yield solid or hollow structures having conductive surfaces as an
alternative to structures with bulk electrical and/or thermal
conductivity.
[0078] Turning to FIGS. 17-29B, a further example of a 3D additive
build process of the present invention for creating a 3D coaxial
structure with a primarily air dielectric is illustrated. A 3D
deposition device 84 may deposit a first material 82 on a substrate
80 to provide a first layer 82a, FIG. 17. The deposition device 84
may be any device which can implement any suitable 3D additive
build process, such as solid polymer printing, stereolithography,
and/or similar method. Alternatively, the deposition device 84 may
schematically represent the deposition and patterning process for a
laminated plastic film and/or patterning process for a spin coated
photoresist. In this example, the first material 82 may comprise a
selectively metallizable polymer, plastic, and/or dielectric
material and may be deposited in a thickness on the order of
microns to centimeters depending on the scale of the object being
created. A second layer 82b of the first material 82 may be
deposited at selected location(s) on the first layer 82a, FIG. 18.
A second material 90 may be deposited at selected location(s) on
the first layer 82a through a deposition device 88 which may be the
same or different from the deposition device 84. The second
material 90 may be provide a support post 90a at a location and
also create voids 91 between the support post 90a and second layer
82b. The second material 90 may be desirably chosen to be different
from the material 82 of the first layer 82a so that the first layer
82a can be selectively metallized by a suitable metallization
process, while the support post 90a is not metallized. Materials
that are selectively metalizable, such as first material 82, can
contain catalysts or other active sites that attract metal
materials and compositions in their bulk or specifically on their
surface. For example, the first material 82 may comprise a
catalyzed form of the second material 90, where the catalyst
renders the first material 82 metallizable. Additionally or
alternatively, differences in physical properties, such as surface
roughness, may be utilized to render a material selectively
metallizable. For example, by surface roughness or surface porosity
material 90 may not have a catalyst adhere in the same process in
which is does adhere to the materials of 82a and 82b. Thus, by
choice or engineering design of first and second materials and
metallization process, the first and second layers 82a, 82b, having
the metallizable compositions, may be selectively metallizable in
comparison to the support post 90a.
[0079] A sacrificial scaffolding material 94 may be deposited
through a deposition device 92, which may be the same or different
than the deposition devices 84, 88, to selectively fill one or more
of the voids 91 to provide a scaffolding 94a for subsequent
structures or layers that may need to be suspended during the 3D
additive build process. The use of a sacrificial scaffolding
material 94 may be predicated on the need to suspend structures or
to provide structures with a void region below them and may be used
to support materials deposited with deposition devices 84, 88. The
scaffolding 94a may be removed in a subsequent step. It should be
clear to one skilled in the art of 3D microfabrication that the
scaffolding 94a may not be required if, for example, a
stereolithography or similar process is used where a liquid resin
serves a similar function, e.g., where selective polymerization
above a liquid layer may form features suspended by the
unpolymerized liquid. In addition, other means to produce a
suspended feature may be used, for example, the use of a rapidly
solidifying material and forces such as cohesion or surface tension
may be used in a 3D additive build system to create a suspended
material without the need for a scaffolding material. In such
examples, a similar build process can be used without the use of a
scaffolding 94a.
[0080] Returning to the build process, the deposition device 84 may
next deposit a third layer of material 82 comprising structures
82d, 82c disposed over the support post 90a and the second layer
82b, respectively, FIG. 21. Additional sacrificial material 94 may
be deposited through deposition device 92 over the scaffolding 94a
in the voids between structures 82d, 82c to provide additional
scaffolding 94b that may be subsequently removed, FIG. 22. The
deposition device 84 may then deposit a fourth layer 82e, which may
comprise the same as materials of layers 82a-82d, over the
structure 82c, FIG. 23, and additional sacrificial material 94 may
be deposited through means 92 over structures 82d and scaffolding
94b to provide additional scaffolding 94c, FIG. 24.
[0081] An upper structure 82f comprising the same material as the
first layer 82a may be deposited through device 84 over the fourth
layer 82e and additional scaffolding 94c, FIG. 25. The scaffolding
94a-94c may be selectively removed to provide a resulting
coaxial-shaped structure 200 having a void 106 (air dielectric)
therein, FIG. 26. As described earlier, the scaffolding 94a-94c may
be dissolved through one or more of a solvent removal step, a
thermal sublimation step, and a vapor removal process. For example,
if layers 82a-82f and support post 90a were a catalyzed and a
non-catalyzed ABS plastic, respectively, then the scaffolding
94a-94c may comprise a starch and removal may occur, for example,
in hot water with ultrasonic agitation.
[0082] At this stage in the process the coaxial structure 200 may
be nonconducting in view of the choice of materials 82, 90 utilized
in the 3D additive build process, with layers 82a-82f collectively
providing a metallizable core 202 for use as an outer conductor and
layer 82d a metallizable core for use as an inner conductor, FIG.
26. A metallization process, may thus be performed to metallize
those structures comprising the first material 82 (i.e., layers
82a-82f) while the support post 90a remains unmetallized, FIGS.
27A, 27B. Again, the first material 82 is selectively metallized
relative to the support post material 90 due to compositional
and/or surface physical differences, for example, between the first
and second materials 82, 90, leading to a difference in the
reaction of such materials 82, 90 to the particular metallization
process utilized, i.e., selective metallization between materials
82, 90. (In other embodiments, the majority of the device may
comprise a non-metallizable material, and any mixture and number of
layers of metallizable material, non-metallizable material and
voids may be produced with the present exemplary process.) FIGS.
27A, 27B schematically illustrate end-on and side cross-sectional
views, respectively, of the coaxial structure 200 after the
selective metallization, such as exposure to a metallization
sequence involving an electroless copper or electroless silver or
electroless gold coating process. As a result, a metallized inner
conductor 97 is provided by the metal coating 97a disposed over
layer 82d, and a metallized outer conductor 110 is provided by the
metal coatings 110a, 110b disposed over the exterior and interior
surfaces of layers 82a-82c, 82e, 82f, respectively. The inner
conductor 97, having its core 82d formed, for example, as part of
the process illustrated in FIG. 21, is electrically discontinuous
from the outer conductor 110 due to non-metallized support post 90a
formed in the steps illustrated in FIG. 20. As illustrated in FIG.
27B, the coaxial inner conductor 97 may extend upward to a top
surface (on the left side) and exit at a port in the plane of the
center conductor 97 (at the right side).
[0083] The metal coatings 97a, 110a, 110b may be submicron or may
be several, 10's, 100's, or 1000's of microns thick depending on
the scale of the structure formed and may be formed through means
known in the arts of electroless and/or electrolytic plating as
well as in electroforming. The coatings 97a, 110a, 110b may
comprise more than one layer of metal, for example, of a layer of
nickel and a layer of gold. Due to the RF skin depth, a thickness
of several microns or less is capable of providing a low loss
transmission line at frequencies above one or more GHz. It is noted
that in some embodiments, a triaxial transmission line could also
be formed in a similar sequence by making the coatings 110a, 110b
formed on the inner and outer surfaces of the core 202
discontinuous and using a conductive substrate, for example.
[0084] In addition, during the sequential build multiple support
posts 90a may be deposited at the step illustrated in FIG. 19. Such
support posts 90a can take forms including blocks, stubs, straps,
sheets, rods and the like. While a simple transmission line section
is illustrated, it should be clear that complex 3D multilayer
networks of coax and waveguide components can be made by the
exemplary 3D additive build process. While an inner conductor 97 is
shown in this example of coax, by omitting the inner conductor 97,
hollow core waveguides can equally be created in the same process.
In addition, integration of DC bias and control lines, chip
mounting regions, connectors and connector flanges, and elements of
the device or system housing itself can be formed by 3D additive
build processes.
[0085] For example, the exemplary 3D additive build process may be
altered beginning at the step of FIG. 19 by omitting the support
post 90a and filling the voids 91 and region that had been occupied
by the support post 90a with a sacrificial material to provide a
scaffold 94d, FIG. 28. Subsequently, a support bar 102 may be
deposited over portions of the second layer 82b and scaffold 94d.
The support bar 102 may comprise metallizable portion 102b and
non-metallizable portions 102a, 102c. Differentiation between
metallizable portion 102b and non-metallizable portions 102a, 102c
may be provided as a bulk property of the support bar 102, such as
by providing a catalyst or other appropriate material to the
metallizable portion 102b while the support bar 102 is being
deposited. Alternatively or additionally, the metallizable portion
102b may be deposited as a separate material different in
composition from the non-metallizable portions 102a, 102c. Still
further, the metallizable portion 102b may be rendered metallizable
as compared to the bulk properties of the support bar 102 by
altering the surface properties, physical or chemical, of the
support bar 102 at those locations. Processing may then continue to
add additional layers and scaffolding materials as per the steps
illustrated in FIGS. 21-26 followed by metallization as discussed
above in connection with FIGS. 27A-27B to yield the coaxial
structure illustrated in FIGS. 29A, 29B. Here, the support bar(s)
102 supports the inner conductor 97 providing the support function
previously provided by support post 90a by virtue of the ends of
the support bars 102 being embedded in the outer conductor core at
layer 82c. Such a use of support bars 102 having metallizable
portion 102b, and non-metallizable portions 102a, 102c may be
implemented in other structures, such as in lieu of the support
post 62 present in the example of FIG. 16, as illustrated in FIG.
30.
[0086] Optional release holes may be provided in closed structures
or those that have limited flow to facilitate removal of the
scaffolding 94a-94c and/or to facilitate the required fluid flow
for the metal coating steps. Such holes, for example, may be added
to upper layer 82f, or any layer, prior to metallization in
locations and of a size to minimize disruption of the electrical
properties desired, as per the use of dissolution plugs 72 as
illustrated in FIGS. 1F, 1G, 13-15. The use of such release holes
and their design and placement can be designed by one skilled in
the art and may be assisted through software such as Ansoft's
HFSS.RTM. for electromagnetic structures, Ansoft's Ansys.RTM. for
mechanical or fluidic structures, and/or similar software
products.
[0087] In addition, it should be clear that while a substrate 80 is
used in the sequence illustrated in FIGS. 17-29B, structures could
readily be released from the substrate 80, for example, by applying
a sacrificial material, such as material 92, and/or by mechanically
detaching the object from a platform, for example. Further, the
selectively metallizable material 82 may remain in the final
device; however, if the metal layers 90a, 110a, 110b are
sufficiently thick, the selectively metallizable material 82 may be
removed after deposition of the metal, for example through one or
more openings in the metal layers 90a, 110a, 110b using methods
which may leave the supports posts 90a intact. Moreover, while an
electronic application is illustrated by way of example, many other
applications such as fluidic devices, mechanical devices, and the
like can be created.
[0088] These and other advantages of the present invention will be
apparent to those skilled in the art from the foregoing
specification. For example, the build process outlined may contain
more or fewer layers and more or fewer materials depending on the
end device and/or structure being made. The build process could be
stopped at any point and items or other materials maybe inserted
into the partially complete structure and the build process then
continued to embed and/or interconnect the inserted materials
and/or devices. For example, passive or active electronic devices,
magnets, powders, liquids and/or such may be put into cavities or
receptacles and the build process continued to partially or fully
interconnect or encapsulate them. Accordingly, it will be
recognized by those skilled in the art that changes or
modifications may be made to the above-described embodiments
without departing from the broad inventive concepts of the
invention. It should therefore be understood that this invention is
not limited to the particular embodiments described herein, but is
intended to include all changes and modifications that are within
the scope and spirit of the invention as set forth in the
claims.
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