U.S. patent application number 10/705726 was filed with the patent office on 2004-07-29 for methods for recognizing features as one or more objects are being fabricated by programmed material consolidation techniques.
Invention is credited to Farnworth, Warren M..
Application Number | 20040148048 10/705726 |
Document ID | / |
Family ID | 32313015 |
Filed Date | 2004-07-29 |
United States Patent
Application |
20040148048 |
Kind Code |
A1 |
Farnworth, Warren M. |
July 29, 2004 |
Methods for recognizing features as one or more objects are being
fabricated by programmed material consolidation techniques
Abstract
A programmed material consolidation apparatus includes at least
one fabrication site and a material consolidation system associated
with the at least one fabrication site. The at least one
fabrication site may be configured to receive one or more
fabrication substrates, such as semiconductor substrates. A machine
vision system with a translatable or locationally fixed camera may
be associated with the at least one fabrication site and the
material consolidation system. A cleaning component may also be
associated with the at least one fabrication site. The cleaning
component may share one or more elements with the at least one
fabrication site, or may be separate therefrom. The programmed
material consolidation apparatus may also include a substrate
handling system, which places fabrication substrates at appropriate
locations of the programmed material consolidation apparatus.
Inventors: |
Farnworth, Warren M.;
(Nampa, ID) |
Correspondence
Address: |
TRASK BRITT
P.O. BOX 2550
SALT LAKE CITY
UT
84110
US
|
Family ID: |
32313015 |
Appl. No.: |
10/705726 |
Filed: |
November 10, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60425567 |
Nov 11, 2002 |
|
|
|
Current U.S.
Class: |
700/119 ;
382/141 |
Current CPC
Class: |
B29C 64/135 20170801;
B33Y 40/00 20141201; B29C 64/35 20170801; B33Y 30/00 20141201; B29C
64/188 20170801; B33Y 50/02 20141201; B29C 64/357 20170801 |
Class at
Publication: |
700/119 ;
382/141 |
International
Class: |
G06F 019/00 |
Claims
What is claimed:
1. A method for programmed material consolidation, comprising:
viewing a portion of a field of exposure of a selective
consolidation system of a programmable material consolidation
apparatus to identify a location of at least one feature within the
field of exposure; and selectively consolidating material on or
proximate to the at least one substrate based on the location of
the at least one feature.
2. The method of claim 1, wherein viewing is effected as a camera
is scanned over the field of exposure.
3. The method of claim 1, wherein viewing includes rotatably
orienting a camera positioned at a fixed location toward the
portion of the field of exposure.
4. The method of claim 3, wherein viewing further includes
magnifying an image viewed by the camera.
5. The method of claim 1, further comprising: transmitting data
signals representative of at least one image of the field of
exposure to at least one processing element; processing the data
signals to compare a viewed feature with a representation of the at
least one feature; and based on the processing, controlling
locations at which the selectively consolidating is effected.
6. The method of claim 5, further comprising: positioning at least
one substrate within the field of exposure.
7. The method of claim 6, wherein transmitting data signals
includes transmitting data signals representative of at least one
image of at least a portion of the at least one substrate to the at
least one processing element.
8. The method of claim 5, wherein transmitting data signals
includes transmitting data signals representative of at least one
image including at least one fiducial mark within the field of
exposure.
9. The method of claim 1, further comprising: positioning at least
one substrate within a field of exposure of a selective
consolidation system of a programmable material consolidation
apparatus.
10. A method for programmed material consolidation, comprising:
instantaneously viewing an entire field of exposure of a selective
consolidation system of a programmable material consolidation
apparatus to identify a location of at least one feature within the
field of exposure; and selectively consolidating material on or
proximate to the at least one substrate based on the location of
the at least one feature.
11. The method of claim 10, wherein instantaneously viewing is
effected from a camera oriented toward the field of exposure.
12. The method of claim 11, further comprising: viewing a portion
of the field of exposure following the instantaneous viewing.
13. The method of claim 12, wherein viewing the portion of the
field is effected by rotating the camera toward the portion of the
field of exposure.
14. The method of claim 12, further comprising: magnifying an image
of the portion of the field of exposure during or following viewing
the portion.
15. The method of claim 10, further comprising viewing a portion of
the field of exposure following the instantaneous viewing.
16. The method of claim 15, further comprising: magnifying an image
of the portion of the field of exposure during or following viewing
the portion.
17. The method of claim 10, further comprising: transmitting data
signals representative of at least one image of the field of
exposure to at least one processing element; processing the data
signals to compare a viewed feature with a representation of the at
least one feature; and based on the processing, controlling
locations at which the selectively consolidating is effected.
18. The method of claim 17, further comprising: positioning at
least one substrate within the field of exposure.
19. The method of claim 18, wherein transmitting data signals
includes transmitting data signals representative of at least one
image of at least a portion of the at least one substrate to the at
least one processing element.
20. The method of claim 17, wherein transmitting data signals
includes transmitting data signals representative of at least one
image including at least one recognizable feature within the field
of exposure.
21. The method of claim 20, wherein transmitting data signals
includes transmitting data signals representative of at least one
image including at least one fiducial mark within the field of
exposure.
22. The method of claim 20 wherein transmitting data signals
includes transmitting data signals representative of at least one
image including at least one feature on the at least one
substrate.
23. The method of claim 10, further comprising: positioning at
least one substrate within a field of exposure of a selective
consolidation system of a programmable material consolidation
apparatus.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/425,567, filed Nov. 11, 2002, the disclosure of
which is hereby incorporated in its entirety by this reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to apparatus for
effecting programmed material consolidation techniques, such as
stereolithography, and, more particularly, to apparatus that are
configured to fabricate features on semiconductor devices and
related components. The present invention also relates to
programmed material consolidation methods that include use of such
apparatus.
[0004] 2. Background of Related Art
[0005] Over the past decade or so, a manufacturing technique which
has become known as "stereolithography" and which is also known as
"layered manufacturing" has evolved to a degree where it is
employed in many industries.
[0006] Basically, stereolithography, as conventionally practiced,
involves utilizing a computer, typically under control of
three-dimensional (3-D) computer-aided design (CAD) software, to
generate a 3-D mathematical simulation or model of an object to be
fabricated. The computer mathematically separates or "slices" the
simulation or model into a large number of relatively thin,
parallel, usually vertically superimposed layers. Each layer has
defined boundaries and other features that correspond to a
substantially planar section of the simulation or model and, thus,
of the actual object to be fabricated. A complete assembly or stack
of all of the layers defines the entire simulation or model. A
simulation or model which has been manipulated in this manner is
typically stored and, thus, embodied as a CAD computer file. The
simulation or model is then employed to fabricate an actual,
physical object by building the object, layer by superimposed
layer. Surface resolution of the fabricated object is, in part,
dependent upon the thickness of the layers.
[0007] A wide variety of approaches to stereolithography by
different companies has resulted in techniques for fabricating
objects from various types of materials. Regardless of the material
employed to fabricate an object, stereolithographic techniques
usually involve disposition of a layer of unconsolidated or unfixed
material corresponding to each layer of the simulation or model.
Next, the material of a layer is selectively consolidated or fixed
to at least a partially consolidated, partially fixed, or semisolid
state in those areas of a given layer that correspond to solid
areas of the corresponding section of the simulation or model.
Also, while the material of a layer is being consolidated or fixed,
that layer may be bonded to a lower layer of the object which is
being fabricated.
[0008] The unconsolidated material employed to build an object may
be supplied in particulate or liquid form. The material may itself
be consolidated or fixed. Alternatively, when the unconsolidated
material comprises particles, a separate binder material mixed
therein or coating the particles may facilitate bonding of the
particles to one another, as well as to the particles of a
previously formed layer.
[0009] Surface resolution of the features of a fabricated object
depends, at least in part, upon the material being used. For
example, when particulate materials are employed, resolution of
object surfaces is highly dependent upon particle size, whereas
when a liquid is employed, surface resolution is highly dependent
upon the minimum surface area of the liquid which can be
consolidated or fixed and the minimum thickness of a material layer
that can be generated. Of course, in either case, resolution and
accuracy of the features of an object being produced from the
simulation or model are also dependent upon the ability of the
apparatus used to consolidate or fix the material to precisely
track the mathematical instructions indicating solid areas and
boundaries for each layer of material.
[0010] Toward that end, and depending upon the type and form of
material to be fixed, stereolithographic fabrication processes have
employed various fixation approaches. For example, particles have
been selectively consolidated by particle bombardment (e.g., with
electron beams), disposition of a binder or other fixative in a
manner similar to ink-jet printing techniques, and focused
irradiation using heat or specific wavelength ranges. In some
instances, thin, preformed sheets of material may be superimposed
to build an object, each sheet being fixed to a next-lower sheet
and unwanted portions of each sheet removed, a stack of such sheets
defining the completed object.
[0011] Early on in its development, stereolithography was used to
rapidly fabricate prototypes of objects from CAD files. Prototypes
of objects might be built to verify the accuracy of the CAD file
defining the object (e.g., an object or negative of a mold to be
machined) and to detect any design deficiencies and possible
fabrication problems before a design was committed to large-scale
production. Stereolithographic techniques have also been used in
the fabrication of molds. Using stereolithographic techniques,
either male or female forms on which mold material might be
disposed could be rapidly generated.
[0012] In more recent years, stereolithography has been employed to
develop and refine object designs in relatively inexpensive
materials. Stereolithography has also been used to fabricate small
quantities of objects for which the cost of conventional
fabrication techniques is prohibitive, such as in the case of
plastic objects that have conventionally been formed by injection
molding techniques. It is also known to employ stereolithography in
the custom fabrication of products generally built in small
quantities or where a product design is rendered only once.
Finally, it has been appreciated in some industries that
stereolithography provides a capability to fabricate products, such
as those including closed interior chambers or convoluted
passageways, which cannot be fabricated satisfactorily using
conventional manufacturing techniques. It has also been recognized
in some industries that a stereolithographic object or component
may be formed or built around another, pre-existing object or
component to create a larger product.
[0013] Conventionally, stereolithographic apparatus have been used
to fabricate freestanding structures. Such structures have been
formed directly on a platen or other support system of the
stereolithographic fabrication apparatus, which is located within
the fabrication tank of the stereolithographic apparatus. As the
freestanding structures are fabricated directly on the support
system, there is typically no need to precisely and accurately
position features of the stereolithographically fabricated
structure. As such, conventional stereolithographic apparatus lack
machine vision systems for ensuring that structures are fabricated
at certain locations.
[0014] Moreover, conventional stereolithographic apparatus lack
support systems, handling systems, and cleaning equipment which are
suitable for use with relatively delicate structures, such as
semiconductor substrates and semiconductor devices that have been
fabricated thereon.
[0015] Accordingly, there is a need for stereolithography apparatus
which are configured to form structures on fabrication substrates,
such as semiconductor substrates and semiconductor device
components and which include systems for accurately positioning the
fabricated structures, supporting and handling the fabrication
substrates, and cleaning excess and residual material from the
fabrication substrates.
SUMMARY OF THE INVENTION
[0016] The present invention includes stereolithography apparatus
and other programmable material consolidation apparatus and systems
that are configured to fabricate features on semiconductor devices
or on components that are configured for use with semiconductor
devices. In addition, the present invention includes
stereolithographic and other programmed material consolidation
methods (e.g., stereolithography, layered object manufacturing
(LOM), selective laser sintering (SLS), photopolymer jetting,
selective particle atomization and consolidation (laser engineered
net shaping, or "LENS"), and other so-called "rapid prototyping"
technologies) that include use of apparatus according to the
present invention. As used herein, the term "stereolithography" and
variations thereof, where applicable, are intended to denote all
types of programmed material consolidation techniques and is used
synonymously with the phrase "programmed material consolidation"
and variations thereof.
[0017] A programmed material consolidation apparatus, or
"stereolithography apparatus" for simplicity, according to the
present invention includes a fabrication tank, which is also
referred to herein as a "fabrication chamber" or even more broadly
as a "fabrication site." The fabrication tank includes a platen or
other support system suitable for carrying substrates upon which
structures are to be stereolithographically fabricated, which may
also be termed "fabrication substrates." By way of example only,
the fabrication tank and the support therein may be sized and
configured to receive one or more semiconductor substrates, each of
which carries a plurality of semiconductor devices. Alternatively,
or in addition, the platen or other support system may be
configured to support freestanding structures as they are
fabricated. In addition, the fabrication tank may include a
reservoir that is configured to hold a volume of unconsolidated
material, such as a liquid polymer.
[0018] A material consolidation system is associated with the
fabrication tank in such a way as to direct consolidating energy
(e.g., in the form of radiation, such as a laser beam or
less-focused radiation) to a surface of the quantity of
unconsolidated material within the reservoir of the fabrication
tank. When selective consolidation is desired, a high level of
precision may be achieved when the consolidating energy is focused
and the surface of the quantity of unconsolidated material and the
focal point for the consolidating energy substantially intersect
one another.
[0019] Optionally, a stereolithography apparatus that incorporates
teachings of the present invention may include a machine vision
system. The machine vision system includes an optical detection
element, such as a camera, as well as a controller or processing
element, such as a computer processor or a collection of computer
processors, associated with the optical detection element. The
optical detection element may be positioned in a fixed location
relative to the fabrication tank or configured to move relative to
the fabrication tank.
[0020] When included as part of a stereolithographic apparatus that
incorporates teachings of the present invention, the optical
detection element of a machine vision system is useful for
identifying the locations of recognizable features, including,
without limitation, features on a fabrication substrate and
features, such as fiducial marks, at a fabrication site. For
example, the optical detection element may be configured and/or
located to "see" relatively large structures, such as those that
can be seen by the naked eye (i.e., macroscopic structures), such
as the locations of semiconductor devices upon a fabrication
substrate. Alternatively, or in addition, the optical detection
element may be configured and/or located to "see" very small, even
microscopic structures.
[0021] Another optional feature of a stereolithographic apparatus
of the present invention is a cleaning component. A cleaning
component may be positioned and configured to remove excess liquid
polymer from a fabrication substrate while the fabrication
substrate remains positioned upon a support system that is
associated with the fabrication tank. Such a cleaning component may
comprise at least a part of the fabrication tank and, thus, operate
prior to introduction of another fabrication substrate into the
fabrication tank. Alternatively, excess liquid polymer may be
removed from a fabrication substrate during or following removal
thereof from the fabrication tank.
[0022] Additionally, a stereolithographic apparatus that
incorporates teachings of the present invention may include a
material reclamation system. The material reclamation system may be
associated with one or both of the fabrication tank and a cleaning
component, if the stereolithographic apparatus includes a cleaning
component. By way of example, the material reclamation system may
collect material from the cleaning component and recycle the same
into the fabrication tank.
[0023] A programmed material consolidation system that incorporates
teachings of the present invention may include a plurality of
fabrication sites and share a common material consolidation system,
machine vision system, handling system, cleaning component, or
material reclamation system.
[0024] The present invention also includes methods for calibrating
stereolithographic apparatus that incorporate teachings of the
present invention. For example, the locations at which
unconsolidated material may be selectively consolidated may be
calibrated with a machine vision system. As another example, the
magnification of a machine vision system may be calibrated. Also, a
material consolidation system of a stereolithographic apparatus
according to the present invention may be calibrated to optimize
the linearity with which selectively consolidating energy impinges
on a surface of unconsolidated material.
[0025] Programmed material consolidation fabrication processes,
including methods of using each of the features described herein,
are also within the scope of the present invention. In particular,
stereolithographic fabrication processes that incorporate teachings
of the present invention include the use of stereolithographic
techniques to fabricate features on another structure, or
fabrication substrate, such as a semiconductor substrate or
semiconductor device component (e.g., a lead frame, a circuit
board, etc.).
[0026] Other features and advantages of the present invention will
become apparent to those of skill in the art through consideration
of the ensuing description, the accompanying drawings, and the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] In the drawings, which depict exemplary embodiments of
various features of the present invention:
[0028] FIG. 1 is a schematic representation of various possible
elements of a stereolithographic apparatus for fabricating features
on semiconductor devices or associated components in accordance
with the present invention, the elements including a fabrication
tank, a material consolidation system, a machine vision system, a
cleaning component, and a material reclamation system;
[0029] FIG. 2 schematically depicts an exemplary stereolithographic
apparatus in which a single material consolidation system and/or a
single machine vision system may be shared by a plurality of
fabrication tanks;
[0030] FIG. 3 schematically depicts an exemplary embodiment of
fabrication tank that may be used in a stereolithographic apparatus
of the present invention, the fabrication tank including a cavity
and a reservoir which are continuous with one another;
[0031] FIG. 3A illustrates an exemplary support element of the
fabrication tank of FIG. 3, which support element has a
substantially planar support surface;
[0032] FIG. 3B shows another exemplary support element of the
fabrication tank shown in FIG. 3, which support element includes
recesses formed in the support surface thereof;
[0033] FIG. 3C illustrates an exemplary volume control element of
the fabrication tank depicted in FIG. 3, which volume control
element is configured to add unconsolidated material to and/or
remove unconsolidated material from the reservoir of the
fabrication tank;
[0034] FIG. 3D depicts another exemplary volume control element of
the fabrication tank of FIG. 3, which volume control element is
configured to displace unconsolidated material located within the
reservoir of the fabrication tank;
[0035] FIG. 3E schematically depicts a stereolithographic
fabrication tank which includes another variation of volume control
and surface level control element;
[0036] FIG. 4 schematically depicts another embodiment of
fabrication tank that includes a rotatable support element and
which may be used in a stereolithographic apparatus according to
the present invention, such as those shown in FIGS. 1 and 2, which
fabrication tank also comprises a cleaning component and a material
reclamation system;
[0037] FIG. 4A is a top view of an example of a retention system
for use with a support system of the fabrication tank of FIG.
4;
[0038] FIG. 4B is a cross-section taken along line 4B-4B of FIG.
4A;
[0039] FIG. 4C is a top view of another example of a retention
system for use with a support system of the fabrication tank of
FIG. 4;
[0040] FIG. 4D is a cross-section taken along line 4D-D of FIG.
4C;
[0041] FIG. 4E is a cross-sectional representation of another
embodiment of support system that may be used in a fabrication tank
of a semiconductor fabrication apparatus according to the present
invention;
[0042] FIG. 4F is a top view of the support system shown in FIG.
4E;
[0043] FIG. 5 is a schematic representation of still another
exemplary embodiment of fabrication tank that incorporates
teachings of the present invention;
[0044] FIG. 6 is a schematic representation of an exemplary
embodiment of a material consolidation system according to the
present invention, which is configured to focus consolidating
energy so as to selectively consolidate unconsolidated material
which has been placed over a fabrication substrate;
[0045] FIG. 7 schematically depicts another exemplary embodiment of
material consolidation system, which is configured to generally
consolidate unconsolidated material which has been placed over a
fabrication substrate;
[0046] FIG. 8 schematically illustrates an exemplary embodiment of
machine vision system that may be used with a fabrication tank of a
stereolithographic apparatus according to the present invention,
with the machine vision system being configured to move relative to
a surface of unconsolidated material which is to be consolidated by
the stereolithographic apparatus;
[0047] FIG. 9 is a schematic representation of another exemplary
embodiment of machine vision system, which embodiment is configured
to remain at a fixed location relative to a surface of
unconsolidated material which is to be consolidated by a
stereolithographic apparatus with which the machine vision system
is used;
[0048] FIG. 10 is a schematic representation of another embodiment
of cleaning component, as well as an exemplary embodiment of a
material reclamation system;
[0049] FIG. 11 is a schematic representation of yet another
embodiment of cleaning component that may be used as part of a
stereolithographic apparatus according to the present
invention;
[0050] FIG. 12 is a schematic representation of the manner in which
the locations at which a layer of unconsolidated material is
selectively consolidated may be calibrated with a machine vision
system of a stereolithographic apparatus of the present
invention;
[0051] FIG. 13 is a top view of a fabrication tank, depicting an
exemplary manner in which a linearity calibration may be conducted;
and
[0052] FIG. 14 is a cross-sectional representation of a fabrication
substrate and an object being stereolithographically fabricated
thereon in accordance with teachings of the present invention.
DETAILED DESCRIPTION
[0053] An exemplary stereolithographic apparatus 10 for fabricating
features on semiconductor substrates 52, semiconductor devices 54
or associated components (e.g., lead frames, circuit boards, etc.)
(not shown) or other fabrication substrates 50 is schematically
depicted in FIG. 1. As shown, stereolithographic apparatus 10
includes a fabrication tank 100 and a material consolidation system
200, a machine vision system 300, a cleaning component 400, and a
material reclamation system 500 that are associated with
fabrication tank 100. The depicted stereolithographic apparatus 10
also includes a substrate handling system 600, such as a rotary
feed system or linear feed system available from Genmark Automation
Inc. of Sunnyvale, Calif., for moving fabrication substrates 50
from one system of stereolithographic apparatus to another.
Features of one or more of the foregoing systems may be associated
with one or more controllers 700, or processing elements, such as
computer processors or smaller groups of logic circuits, in such a
way as to effect their operation in a desired manner.
[0054] Controller 700 may comprise a computer or a computer
processor, such as a so-called "microprocessor," which may be
programmed to effect a number of different functions.
Alternatively, controller 700 may be programmed to effect a
specific set of related functions or even a single function. Each
controller 700 of stereolithographic apparatus 10 may be associated
with a single system thereof or a plurality of systems so as to
orchestrate the operation of such systems relative to one
another.
[0055] Fabrication tank 100 includes a chamber 110 which is
configured to contain a support system 130. In turn, support system
130 is configured to carry one or more fabrication substrates 50.
By way of example only, the types of fabrication substrates 50 that
support system 130 may be configured to carry may include, without
limitation, a bulk semiconductor substrate 52 (e.g., a full or
partial wafer of semiconductive material, such as silicon, gallium
arsenide, indium phosphide, a silicon-on-insulator (SOI) type
substrate, such as silicon-on-ceramic (SOC), silicon-on-glass
(SOG), or silicon-on-sapphire (SOS), etc.) that includes a
plurality of semiconductor devices 54 thereon.
[0056] Fabrication tank 100 may also have a reservoir 120
associated therewith. Reservoir 120 may be continuous with chamber
110. Alternatively, reservoir 120 may be separate from, but
communicate with, chamber 110 in such a way as to provide
unconsolidated material 126 thereto. Reservoir 120 is configured to
at least partially contain a volume 124 of unconsolidated material
126, such as a photoimageable polymer, or "photopolymer," particles
of thermoplastic polymer, resin-coated particles, or the like.
[0057] Photopolymers believed to be suitable for use with a
stereolithography apparatus 10 according to the present invention
include, without limitation, ACCURA.RTM. SI 40 HC and AR materials,
ACCURA.RTM. SI 40 ND material, and CIBATOOL SL 5170, SL 5210, SL
5530, and SL 7510 resins. The ACCURA.RTM. materials are available
from 3D Systems, Inc., of Valencia, Calif., while the CIBATOOL
resins are available from Ciba Specialty Chemicals Company of
Basel, Switzerland.
[0058] Reservoir 120 or another component associated with one or
both of fabrication tank 100 and reservoir 120 thereof may be
configured to maintain a surface 128 of a portion of volume 124
located within chamber 110 at a substantially constant elevation
relative to chamber 110.
[0059] A material consolidation system 200 is associated with
fabrication tank 100 in such a way as to direct consolidating
energy 220 into chamber 110 thereof, toward at least areas of
surface 128 of volume 124 of unconsolidated material 126 within
reservoir 120 that are located over fabrication substrate 50.
Consolidating energy 200 may comprise, for example, electromagnetic
radiation of a selected wavelength or a range of wavelengths, an
electron beam, or other suitable energy for consolidating
unconsolidated material 126. Material consolidation system 200
includes a source 210 of consolidating energy 220. If consolidating
energy 220 is focused, source 210 or a location control element 212
associated therewith (e.g., a set of galvanometers, including one
for x-axis movement and another for y-axis movement) may be
configured to direct, or position, consolidating energy 220 toward
a plurality of desired areas of surface 128. Alternatively, if
consolidating energy 220 remains relatively unfocused, it may be
directed generally toward surface 128 from a single, fixed location
or from a plurality of different locations. In any event, operation
of source 210, as well as movement thereof, if any, may be effected
under the direction of controller 700.
[0060] When material consolidation system 200 directs focused
consolidating energy 220 toward surface 128 of volume 124 of
unconsolidated material 126, stereolithographic apparatus 10 may
also include a machine vision system 300. Machine vision system 300
facilitates the direction of focused consolidating energy 220
toward desired locations of features on fabrication substrate 50.
As with material consolidation system 200, operation of machine
vision system 300 may be proscribed by controller 700. If any
portion of machine vision system 300, such as a camera 310 thereof,
moves relative to chamber 110 of fabrication tank 100, that portion
of machine vision system 300 may be positioned so as provide a
clear path to all of the locations of surface 128 that are located
over each fabrication substrate 50 within chamber 110.
[0061] Optionally, as schematically depicted in FIG. 2, one or both
of material consolidation system 200 (which may include a plurality
of mirrors 214) and machine vision system 300 of a
stereolithographic apparatus 10 may be oriented and configured to
operate in association with a plurality of fabrication tanks 100.
Of course, one or more controllers 700 would be useful for
orchestrating the operation of material consolidation system 200,
machine vision system 300, and substrate handling system 600
relative to a plurality of fabrication tanks 100.
[0062] With returned reference to FIG. 1, cleaning component 400 of
stereolithographic apparatus 10 may also operate under the
direction of controller 700. Cleaning component 400 of
stereolithographic apparatus 10 may be continuous with a chamber
110 of fabrication tank 100 or positioned adjacent to fabrication
tank 100. If cleaning component 400 is continuous with chamber 110,
any unconsolidated material 126 that remains on a fabrication
substrate 50 may be removed therefrom prior to introduction of
another fabrication substrate 50 into chamber 110.
[0063] If cleaning component 400 is positioned adjacent to
fabrication tank 100, residual unconsolidated material 126 may be
removed from a fabrication substrate 50 as fabrication substrate 50
is removed from chamber 110. Alternatively, any unconsolidated
material 126 remaining on fabrication substrate 50 may be removed
therefrom after fabrication substrate 50 has been removed from
chamber 110, in which case the cleaning process may occur as
another fabrication substrate 50 is positioned within chamber
110.
[0064] Material reclamation system 500 collects excess
unconsolidated material 126 that has been removed from a
fabrication substrate 50 by cleaning component 400, then returns
the excess unconsolidated material 126 to reservoir 120 associated
with fabrication tank 100.
Fabrication Sites
[0065] Turning now to FIGS. 3-5, various exemplary embodiments of
fabrication sites, chambers, or tanks, that may be used in a
stereolithographic apparatus 10 (FIG. 1) or other programmable
material consolidation apparatus or system that incorporates
teachings of the present invention are illustrated.
[0066] FIG. 3 shows a fabrication tank 100' which includes a
chamber 110' that is continuous with a reservoir 120'. A support
system 130', which includes a platen, or support element 132', a
positioning element 140', and an actuation element 146', is located
within reservoir 120', beneath chamber 110', and may be moved to a
plurality of different vertical positions, or elevations,
therein.
[0067] A substrate-supporting surface of support element 132',
which is also referred to herein as a support surface 134' for the
sake of simplicity, may be substantially planar, as shown in FIG.
3A. Alternatively, as depicted in FIG. 3B, support surface 134' may
have one or more recesses 136' formed therein, each recess 136'
being configured to receive at least a portion of a fabrication
substrate 50. Additionally, each recess 136' may be configured to
position a fabrication substrate 50 in a desired orientation upon
introduction of the same thereinto. Support surface 134' may be
configured to carry a single fabrication substrate 50 or a
plurality of fabrication substrates 50.
[0068] Positioning element 140' may be coupled to a bottom surface
138' of support element 132' or otherwise operatively associated
with support element 132'. Positioning element 140' is depicted as
being an elongate structure that includes a coupling end 142' that
has been secured to bottom surface 138', as well as an opposite,
actuation end 144'. Nonetheless, positioning elements 140' of other
configurations are also within the scope of the present invention.
By way of example only, positioning element 140' may comprise a
hydraulically or pneumatically actuated piston, a screw, a linear
actuator or stepper element, a series of gears, or the like.
[0069] Actuation element 146' is, of course, associated with and
configured to effect movement of positioning element 140'.
Accordingly, examples of actuation elements 146' that may be used
as part of support system 130' include, but are not limited to,
hydraulic actuators, pneumatic actuators, screw-drive motors,
stepper motors, and other known actuation means for controlling the
movement of positioning element 140' in such a way as to cause
support element 132' to move from one elevation to another in a
substantially vertical direction and with a higher degree of
dimensional precision. Additionally, positioning element 140' and
actuation element 146' may desirably elevate support element 132'
and, thus, each fabrication substrate 50 thereon out of chamber
110' to facilitate movement of each fabrication substrate 50 by
substrate handling system 600 (FIGS. 1 and 2). Alternatively, the
level at which surface 128 of volume 124 of unconsolidated material
126 is located may be lowered below support surface 134'.
[0070] Control over the operation of actuation element 146' and,
thus, over the movement of positioning element 140' and elevation
of support element 132' may be provided by controller 700 or
another processing element 105' (e.g., a processor or smaller
collection of logic circuits), which may be dedicated for use with
support system 130' or fabrication tank 100', in communication
therewith, either as a part of fabrication tank 100' or, more
generally, as a part of stereolithographic apparatus.
[0071] Reservoir 120' may include a surface level control element
150' which is configured to maintain surface 128 of volume 124 of
unconsolidated material 126 at a substantially constant elevation.
Surface level control element 150' may include a surface level
sensor 152' and an element for adjusting volume 124 of
unconsolidated material 126, which element is referred to herein as
a "volume adjustment element" 154'. Both surface level sensor 152'
and volume adjustment element 154' may communicate with controller
700 or processing element 105', which monitors the level of surface
128, as indicated by signals produced and transmitted by surface
level sensor 152', and facilitates adjustment or displacement of
volume 124 by way of volume adjustment element 154' to compensate
for changes in the elevation of surface 128 and thereby maintain
surface 128 at a substantially constant elevation.
[0072] By way of example only, surface level sensor 152' may
comprise a laser sensor and reflected laser beam, which may be used
in connection with one or more charge-coupled device (CCD) cameras
or complementary metal-oxide-semiconductor (CMOS) cameras.
Triangulation techniques may be used with such devices to determine
the distance of surface 128 from a fixed point and, thus, the
elevation, or level, at which surface 128 is located.
[0073] If volume adjustment element 154' is configured to change
volume 124 of unconsolidated material 126 within reservoir 120',
volume adjustment element 154' may comprise a pump 156' or series
of pumps 156' that may remove unconsolidated material 126 from
reservoir 120' and transport the same to an external reservoir
158', as well as add unconsolidated material 126 from an external
reservoir 158' to reservoir 120', as shown in FIG. 3C.
[0074] If volume adjustment element 154' is instead configured to
displace a portion of volume 124 located within reservoir 120',
volume adjustment element 154' may, for example, comprise a piston
or other displacement member 160' which may be incrementally
introduced into and withdrawn from reservoir 120', as shown in FIG.
3D. Of course, movement of such a displacement member 160' may be
effected by an actuator 162' therefor, such as a hydraulic
actuator, a pneumatic actuator, a screw-drive motor, a stepper
motor, or the like. Alternatively, vibrations may be transmitted
directly to unconsolidated material 126 by, for example, a piston
face, diaphragm, or the like.
[0075] Alternatively, as shown in FIG. 3E, a volume adjustment
element 154" may include one or more apertures or other openings
102 in a side wall 101 of fabrication tank 100' that have lower
edges 103 that are positioned at an elevation within fabrication
tank 100' at which surface 128 of volume 124 of unconsolidated
material 126 is to be maintained. In addition, surface level
control element 154" includes one or more receptacles 104 that
communicate with openings 102 to receive overflowing unconsolidated
material 126 as support element 132' an a substrate or other
workpiece thereon, as well as any stereolithographically fabricated
objects, are lowered into fabrication tank 100' and displace
unconsolidated material 126 therein. A pumping system or other
material recycling element 105 may communicate with each receptacle
104 in such a way as to return overflowed unconsolidated material
126 to tank 100' as support element 132' is raised to facilitate
stereolithographic fabrication of one or more other objects.
[0076] The introduction of support element 132' or one or more
fabrication substrates 50 into a volume 124 of unconsolidated
material 126 contained within reservoir 120' may result in the
introduction of gas or air bubbles into unconsolidated material
126. Accordingly, referring again to FIG. 3, fabrication tank 100'
may optionally include a bubble elimination system 165' which is
associated with a boundary or wall 114' of reservoir 120' or with
support system 130' so as to facilitate the removal of air or gas
bubbles (not shown) from unconsolidated material 126. By way of
example, bubble elimination system 165' may comprise an ultrasonic
transducer of a known type (e.g., a piezoelectric transducer),
which causes fabrication tank 100' or support system 130' thereof
to vibrate. Vibrations in fabrication tank 100' or support system
130' are transmitted to unconsolidated material 126 within
reservoir 120', causing any bubbles therein to dislodge from a
structure to which they are adhered and float to surface 128, where
they will pop or may be removed, such as by use of negative
pressure.
[0077] Referring now to FIG. 4, another exemplary embodiment of
fabrication tank 100" is illustrated. Fabrication tank 100"
includes a reservoir 120" at the base thereof and a chamber 110"
which is located over reservoir 120" and which is continuous
therewith. In addition, chamber 110" of fabrication tank 100"
includes a material reclamation zone 170", as well as a cleaning
zone 180" located above material reclamation zone 170".
[0078] As shown, reservoir 120" may be configured to contain a
substantially constant volume 124 of material, including
unconsolidated material 126 and, if stereolithographic processes
have been initiated, consolidated material 126' (FIG. 14).
Accordingly, reservoir 120" may include a surface level control
element 150', such as that described above in reference to FIGS. 3,
3C, and 3D.
[0079] A support system 130" of fabrication tank 100" includes a
support element 132" which is positionable at a plurality of
distinct, precise elevations within reservoir 120" and, optionally,
within chamber 110". Movement of support element 132" is effected
by a positioning element 140". Positioning element 140" is, in
turn, associated with an actuation element 146", which may be
actuated to cause positioning element 140" to move so as to
position support element 132" at a desired elevation within
reservoir 120" or chamber 110". Additionally, positioning element
140" may elevate support element 132" and, thus, any fabrication
substrates 50 thereon out of chamber 110" to facilitate handling of
fabrication substrates 50 by substrate handling system 600 (FIGS. 1
and 2). Actuation element 146" may communicate with controller 700
or processing element 105' in such a way that controller 700
directs the operation of actuation element 146".
[0080] In addition, actuation element 146" may be configured to
rotate support element 132" about an axis A thereof and within a
plane P in which support element 132" is located. Alternatively,
fabrication tank 100" may include a rotation element 148" that is
independent from actuation element 146" and which is configured to
cause support element 132" to rotate. Such rotation may occur under
instructions, in the form of signals or carrier waves, from
controller 700 or processing element 105'. By way of example and
not by way of limitation, a stepper motor or a screw-drive motor
that has been modified to move a screw, then maintain the screw in
a substantially constant location when the screw has reached one or
more certain positions (e.g., material reclamation zone 170" or
cleaning zone 180"), may be used as either actuation element 146"
or rotation element 148".
[0081] When support element 132" is moved into material reclamation
zone 170" or cleaning zone 180" of chamber 110", actuation element
146" or rotation element 148" may cause support element 132" to
accelerate and rotate at a sufficient speed that centrifugal force
causes any excess unconsolidated material 126 and/or cleaning
agents 127, such as water, solvents for unconsolidated material
126, detergents, combinations thereof, or the like, to be removed
from a fabrication substrate 50 carried thereby while remaining
substantially within the same plane as that within which support
element 132" is located.
[0082] Material reclamation zone 170" and cleaning zone 180" may
each be provided with a receptacle 172", 182", respectively, that
extends substantially around the periphery of an inner boundary or
wall 114" of reservoir 120". Receptacles 172" and 182" are each
positioned at approximately the same elevations within reservoir
120" that support element 132" will be located when positioned
within reclamation zone 170" and cleaning zone 180" thereof,
respectively. Accordingly, as excess unconsolidated material 126
and/or cleaning agents 127 are removed, by spinning, from each
fabrication substrate 50 that is carried by support element 132",
receptacle 172", 182" will receive substantially all of the excess
unconsolidated material 126 or cleaning agents 127 that are removed
therefrom.
[0083] Since support element 132" of fabrication tank 100" is
configured to be rotated, or spun, at relatively high speed,
support element 132" may be configured to retain one or more
fabrication substrates 50 during such rotation, or spinning. FIGS.
4A and 4B depict an example of a retention system 190 that may be
used on a support element 132" to secure a fabrication substrate 50
in place thereon, particularly when support element 132" is being
accelerated to spin at high rotational speeds.
[0084] The depicted retention system 190 includes a raised
periphery 191 that forms a receptacle 192 within which a
fabrication substrate 50 may be substantially laterally contained.
Thus, when support element 132" is rotated, or spun, raised
periphery 191 prevents a fabrication substrate 50 that is being
carried by support element 132" from being thrown laterally
therefrom. One or more alignment features 193, which ensure that
fabrication substrate 50 has been properly positioned and oriented
within receptacle 192, may also be formed by the inner border of
raised periphery 191. In addition, retention system 190 may include
one or more access elements 194 which provide access to portions of
an outer periphery 55 of a fabrication substrate 50 located within
receptacle 192, thereby facilitating removal of fabrication
substrate 50 from receptacle 192, as well as placement of another
fabrication substrate 50 therein.
[0085] Optionally, raised periphery 191 may protrude above an upper
surface 56 of fabrication substrate 50 a distance which comprises a
maximum distance a stereolithographically fabricated object (not
shown) may protrude from upper surface 56. Unconsolidated material
126 that is introduced onto upper surface 56 of fabrication
substrate 50 may be laterally contained by raised periphery 191. An
upper surface 22U' of the uppermost layer 22' of unconsolidated
material 126 within the confines of raised periphery 191 may be
planarized by translating a planarizing element 195, such as a
meniscus blade (which includes a meniscus at the trailing edge
thereof) or air knife, thereacross to remove unconsolidated
material 126 and/or smooth upper surface 22U'. An uppermost surface
of raised periphery 191 defines the level at which planarizing
element 195 may be translated across unconsolidated material
126.
[0086] Raised periphery 191 may be an integral part of a support
surface 134" of support element 132", with the majority of
retention system 190 being formed in support surface 134".
Alternatively, retention system 190 may be formed separately from
the manufacture of support element 132" and secured to support
surface 134" thereof. By way of example only, stereolithographic
processes may be employed to fabricate retention system 190 on
support surface 134", such as by using stereolithographic apparatus
10.
[0087] Additionally, retention system 190 may include a sealing
element 198, which may be positioned on support surface 134" so as
to underlie at least a periphery of a fabrication substrate 50
positioned thereover. By way of example only, sealing element 198
may comprise a somewhat flattened ring which is configured to seal
against an outer periphery 55 of fabrication substrate 50, as well
as regions of bottom surface 51 of fabrication substrate 50 which
are located adjacent to outer periphery 55. Such a sealing element
198 may prevent unconsolidated material 126 from contacting bottom
surface 51 of fabrication substrate 50 and support surface 134" of
support element 132". Exemplary materials from which sealing
element 198 may be fabricated include, without limitation,
compressible, resilient materials, such as silicone, polyurethane,
ethylene vinyl alcohol (EVA), or the like.
[0088] Also, in order to secure fabrication substrate 50 in place
relative to support surface 134", retention system 190 may include
one or more pressure ports 196, which are configured to communicate
with a pressure source 197 (e.g., a vacuum or an air compressor).
As support element 132" is configured to be rotated, each pressure
port 196 may be fitted with a valve 199, which seals that pressure
port 196 when pressure source 197 is not in communication
therewith. Of course, such valves 199 are not necessary when
support element 132" does not rotate, as in fabrication tank 100'.
As a negative pressure is applied through the one or more pressure
ports 196 to a bottom surface 51 of fabrication substrate 50, the
negative pressure pulls fabrication substrate 50 against sealing
element 198, sealing bottom surface 51 against sealing element 198.
In addition to securing fabrication substrate 50 over support
surface 134" and possibly providing a cushion for fabrication
substrate 50, as noted previously, sealing element 198 may prevent
unconsolidated material from contacting bottom surface 51 and
support surface 134". Operation of pressure source 197 and, if
necessary, communication thereof with pressure ports 196 may be
under control of controller 700, processing element 105', or
another processing element that is dedicated for use with retention
system 190.
[0089] FIGS. 4C and 4D illustrate a variation of retention system
190', which is useful with support element 132" of fabrication tank
100". Retention system 190' includes one or more ejection elements
196'. Ejection elements 196' are useful for removing fabrication
substrate 50 from receptacle 192, as well as for breaking a seal
caused by the presence of a negative pressure beneath fabrication
substrate 50, which is applied against at least a portion of bottom
surface 51 thereof. Operation of ejection elements 196' may be
controlled by way of a controller 700 in communication therewith.
By way of example only, each ejection element 196' may comprise a
mechanical piston that may be recessed within support surface 134"
to facilitate placement of a fabrication substrate 50 thereon or
raised by an actuation element 197' (e.g., a pneumatic, hydraulic,
or mechanical actuation element) to protrude from support surface
134" and eject a fabrication substrate 50 from recess 192 and raise
fabrication substrate 50 to facilitating grasping thereof by
substrate handling system 600. In this example, it is actuation
element 197' that communicates with controller 700, processing
element 105', or another processing element and that operates in
accordance with instructive signals, or carrier waves, from
controller 700, processing element 105', or the other processing
element.
[0090] Alternatively, referring again to FIGS. 4A and 4B, each
ejection element 196' may comprise a pressure port 196, which, as
described previously herein, communicates with one or more pressure
sources 197. A negative air pressure may be applied through
pressure port 196 to a bottom surface 51 of a fabrication substrate
50 to secure the same to support surface 134". Conversely, a
positive air pressure may be forced through port 196 against bottom
surface 51 to eject a fabrication substrate 50 from support surface
134". As shown, each pressure source 197 may communicate with
controller 700, processing element 105', or another processing
element (FIG. 4), which directs operation of pressure source 197 by
known means. The use of ejection element 196' to apply positive air
pressure to bottom surface 51 of fabrication substrate 50 may also
be used to break a seal, if any, between bottom surface 51 and a
feature, such as a sealing element 198, of support element
132".
[0091] Optionally, pressure ports 196 may be configured and the
output of pressure source 197 modulated so as to create a
circulating airflow beneath bottom surface 51 as positive pressure
is forced therethrough, causing fabrication substrate 50 to be
lifted off of support surface 134" in such a way as to hover
thereover in accordance with Bernoulli's Law. Such an ejection
element 196' is, therefore, useful for facilitating the grasping of
fabrication substrate 50 by a substrate handling system 600 (FIGS.
1 and 2) of stereolithography apparatus 10, 10', as well as to
remove any unconsolidated material 126 from support surface
134".
[0092] Another embodiment of support system 130'" that may be used
in a fabrication tank 100, 100', 100" of a stereolithographic
apparatus 10, 10' according to the present invention is shown in
FIGS. 4E and 4F. Support system 130'" includes a support element
132'" and a locking ring 191'" that surrounds at least a portion of
outer periphery 55 of fabrication substrate 50 to secure the same
to support element 132'". Locking ring 191'" forms a receptacle
192'" within which fabrication substrate 50 is laterally contained.
An upper surface 56 of fabrication substrate 50, however, remains
substantially exposed.
[0093] Locking ring 191'" includes an upper, laterally inwardly
extending lip 193'" which is configured to contact an upper surface
56 of fabrication substrate 50. As locking ring 191'" also defines
a fixed distance between a support surface 134'" and lip 193'",
which distance may not be the same as the thickness of a
fabrication substrate 50 to be positioned therebetween, one or more
spacers 194'" may be fabricated (e.g., stereolithographically) or
positioned on support surface 134'" so that support system 130'"
may be tailored to accommodate thinner fabrication substrates 50.
Spacers 194'" are also useful for preventing bottom surface 51 of
fabrication substrate 50 from adhering to support surface 134'" of
support element 132'". Support elements 132'" of this type,
including stereolithographically fabricated support elements 132'",
may be reused.
[0094] A thickness of lip 193'" may define a maximum distance a
stereolithographically fabricated object (not shown) may protrude
from upper surface 56 of fabrication substrate 50. The thickness of
lip 193'" may be increased by positioning or forming (e.g.,
stereolithographically) an extension ring 202'" thereon.
Unconsolidated material 126 that is introduced onto upper surface
56 of fabrication substrate 50 may be laterally contained by lip
193'". By way of example only, unconsolidated material 126 may be
introduced within the confines of lip 193'" and any extension rings
202'" thereon by lowering support system 130'" beneath surface 128
(FIG. 4) of volume 124 of unconsolidated material 126 so as to
permit unconsolidated material 126 to flow therein, then raising
support system 130'" so that an upper edge of lip 193'" or an
extension ring 202'" thereon is substantially coplanar with surface
128.
[0095] An upper surface 22U' of the uppermost layer 22' of
unconsolidated material 126 within the confines of lip 193'" and
any extension rings 202'" thereon may be planarized by translating
a planarizing element 195, such as a meniscus blade or air knife,
thereacross (FIG. 4B). An uppermost surface of lip 193'" or an
extension ring 202'" thereon defines the level at which planarizing
element 195 may be translated across unconsolidated material
126.
[0096] Optionally, with returned reference to FIG. 4, fabrication
tank 100" may include a bubble elimination system 165', such as
that described in reference to FIG. 3. Alternatively,
stereolithographic fabrication tanks 100, such as those that have
chambers 110 with relatively small volumes (e.g., which are
sufficient to contain only a single semiconductor substrate 52),
may include bubble elimination systems that create a negative
pressure, or vacuum, within the chambers thereof. Such a bubble
elimination system may, for example, include one or more sealing
elements, which substantially seal stereolithographic apparatus 10
(FIG. 1) chamber 110, as well as a negative pressure source that
communicates at least with chamber 110 so as to facilitate the
creation of a negative pressure therein.
[0097] Turning now to FIG. 5, still another embodiment of
fabrication tank 100'" that may be used in a stereolithographic
apparatus 10, 10' (FIGS. 1 and 2) according to the present
invention is shown. Fabrication tank 100'" includes substantially
all of the same elements as the embodiment of fabrication tank 100"
described in reference to FIG. 4, except for reservoir 120".
Instead of an integral reservoir, such as reservoir 120",
fabrication tank 100'" includes a dispenser 120'" for applying
unconsolidated material 126, which is drawn from an external
reservoir 159'", to a fabrication substrate 50. By way of example
only, dispenser 120'" may comprise a laminar flow dispenser or a
spray nozzle of a known type. A laminar flow dispenser is currently
preferred for use as material dispenser 120'", as laminar flow
would result in the presence of fewer air bubbles in unconsolidated
material 126 than would be present if unconsolidated material 126
were sprayed onto fabrication substrate 50 and, thus, eliminate the
need for removing such bubbles. Additionally, when dispensed with a
laminar flow dispenser, unconsolidated material 126 may be applied
to upper surface 56 of fabrication substrate 50 without covering
any structures that protrude therefrom (e.g., solder balls that
protrude from a semiconductor device 54), thereby eliminating the
need to subsequently remove consolidated material or unconsolidated
material 126 from such structures. Dispenser 120'" may apply a
predetermined quantity, or metered amount, of unconsolidated
material 126 onto fabrication substrate 50 to form a single layer
22 or multiple layers 22a, 22b, etc. of unconsolidated material 126
thereon, which are to be sequentially dispensed and, possibly,
sequentially consolidated.
[0098] Of course, operation of dispenser 120'" may be controlled by
controller 700 or by a processing element 105'" (e.g., a processor
smaller group of logic circuits) that is associated with
fabrication tank 100'".
Material Consolidation System
[0099] Various exemplary embodiments of material consolidation
systems 200 (FIGS. 1 and 2) that may be used in a
stereolithographic apparatus 10 according to the present invention
are shown in FIGS. 6 and 7.
[0100] With reference to FIGS. 1 and 6, a stereolithographic
apparatus 10 that incorporates teachings of the present invention
may include a material consolidation system 200' which is
configured to direct a focused beam of consolidating energy, such
as a laser beam 220', into a chamber 110 of a fabrication tank 100
and onto selected locations of a surface 128 of a volume 124 of
unconsolidated material 126 which is exposed to chamber 110.
[0101] When a laser beam 220' is employed as the consolidating
energy, material consolidation system 200' includes a laser 210' of
a known type that generates laser beam 220'. By way of example
only, laser 210' may include a source 211' which is configured to
generate light in the ultraviolet (UV) range of wavelengths of
electromagnetic radiation. Laser 210' may also include one or more
lenses 216 to focus a laser beam 220' that has been emitted by
source 211' to a desired resolution. A location control element
212', such as a scan controller (e.g., a galvanometer) of a known
type, may be associated with source 211' of laser 210' in such a
way as to control the path of a laser beam 220' emitted from source
211' and, thus, to effect movement of laser beam 220'. The
operation of location control element 212' and, thus, the movement
of a laser beam 220', may be controlled by controller 700 or a
processing element 205' (e.g., a processor or smaller group of
logic circuits) which is dedicated for use with laser 210', in
accordance with a CAD program and an accompanying CAD file for the
object to be fabricated.
[0102] It is well known that the resolution of a laser beam 220'
that is to be moved may be substantially maintained by keeping the
path of laser beam 220' as constant (in this case, vertical) as
possible. This may be done by increasing the path length of that
laser beam 220' (e.g., to about twelve (12) feet). Nonetheless, it
may not be practical for a stereolithographic apparatus 10 (FIG. 1)
that incorporates teachings of the present invention to include a
laser 210' with a source 211' that is positioned a sufficient
distance from surface 128 of volume 124 of unconsolidated material
126 that is to be selectively consolidated by laser beam 220'.
Accordingly, laser 210' may also include a suitable mirror 214' or
series of mirrors 214' that results in a nonlinear path for laser
210' to provide a desired path length L for laser beam 220' in a
fixed amount of available space. As depicted, the area of mirror
214' may be large enough to substantially cover the entire cone of
possible angles at which laser beam 220' may be directed by
location control element 212' and, thus, to reflect laser beam 220'
from every possible direction onto a corresponding location of
surface 128.
[0103] Optionally, or as an alternative to the use of a location
control element 212', the position and/or orientation of one or
more of mirrors 214' may be moved, such as by an actuator 215'
therefor (e.g., a motor). The operation of actuator 215' and, thus,
the movement of a mirror 214' associated therewith, may be
controlled by controller 700.
[0104] The size of the "spot" 222' of a laser beam 220' that
impinges on surface 128 of unconsolidated material 126 to
consolidate (e.g., cure) the same may be on the order of about
0.001 inch to about 0.008 inch across. It is currently preferred
that, when laser beam 220' is moved across surface 128 (i.e., in
the X-Y plane), the resolution of laser beam 220' be .+-.0.0003
inch over at least a 0.5 inch.times.0.25 inch field from a
predetermined center point C on surface 128, thereby providing a
high resolution scan across an area of at least 1.0 inch.times.0.5
inch. Of course, it is desirable to have substantially this high a
resolution across the entirety of surface 128 to be scanned by
laser beam 220', such area being termed the "field of
exposure."
[0105] FIG. 7 depicts another exemplary embodiment of material
consolidation system 200", which is configured to direct unfocused,
or blanket, consolidating energy 220" in the form of
electromagnetic radiation (e.g., light or a light beam) into a
chamber 110 of a fabrication tank 100 and onto a surface 128 of a
volume 124 of unconsolidated material 126 which is exposed to
chamber 110.
[0106] A source 210" of consolidating energy 220" may remain in a
fixed position as consolidating energy 220" is introduced into
chamber 110 or source 210" may be moved, such as by an actuation
system 217" therefor. By way of example only, such an actuation
system 217" may comprise an X-Y plotter of a known type, which may
operate and, thus, move source 210" under the direction of signals,
or carrier waves, that have been transmitted by controller 700 or
by a processing element 205" (e.g., a processor or smaller group of
logic circuits) that controls operation of machine consolidation
system 200". Operation of source 210" may be under control of
controller or processing element 205".
[0107] Of course, when unconsolidated material 126 is
nonselectively consolidated by consolidating energy 220" from
source 210", a machine vision system 300 (FIGS. 1 and 2) is not
employed at that time.
Machine Vision System
[0108] With returned reference to FIG. 1, a stereolithographic
apparatus 10 according to the present invention that employs a
material consolidation system 200 (e.g., material consolidation
system 200' shown in FIG. 6) which selectively consolidates
material 126 may also include a machine vision system 300. It is
currently preferred that the field of vision of machine vision
system 300 be substantially coextensive with the field of exposure
of a laser beam 220' (FIG. 6) or other consolidating energy 220
employed by a material consolidation system 200 to be used in
conjunction with machine vision system 300.
[0109] Examples of different types of machine vision systems 300
that may be used in accordance with teachings of the present
invention are illustrated in FIGS. 8 and 9.
[0110] In FIG. 8, a scanning embodiment of machine vision system
300', or one which is configured to move relative to a chamber 110
of a fabrication tank 100 (FIGS. 1 and 2) with which it is used, is
depicted. Machine vision system 300' includes a camera 310' which
may be carried and moved over a fabrication substrate 50 by a scan
element 312'. Scan element 312' positions camera 310' in close
proximity to (e.g., inches from) surface 128 (FIG. 1) of volume 124
of unconsolidated material 126 (FIG. 1) so as to enable camera 310'
to view minute features on a fabrication substrate 50 (e.g., bond
pads, fuses, or other circuit elements of a semiconductor device)
that is located at or near surface 128. Upon viewing fabrication
substrate 50, camera 310' communicates information about the
precise locations of such features (e.g., with an accuracy of up to
about .+-.0.1 mil (i.e., 0.0001 inch)) to a computer 320' of
machine vision system 300'.
[0111] Camera 310' may comprise any one of a number of commercially
available cameras, such as CCD cameras or CMOS cameras available
from a number of vendors. Of course, the image resolution of camera
310' should be sufficiently high as to enable camera 310' to view
the desired features of fabrication substrate 50 and, thus, to
enable computer 320' to precisely determine the positions of such
features. In order to provide one or more reference points for the
features that are viewed by camera 310', camera 310' may also
"view" one or more fiducial marks 112 within a chamber 110 (FIG. 1)
of a fabrication tank 100 (FIG. 1) with which machine vision system
300' is used.
[0112] Suitable electronic componentry, as required for adapting or
converting the signals, or carrier waves, that are output by camera
310', may be incorporated in a board 322' installed in a computer
320'. Such electronic componentry may include one or more
processors 324', other groups of logic circuits, or other
processing or control elements that have been dedicated for use in
conjunction with camera 310'. At least one processing element 324',
which may include a processor 324', another, smaller group of logic
circuits, or other control element that has been dedicated for use
in conjunction with camera 310', is programmed, as known in the
art, to process signals that represent images that have been
"viewed" by camera 310' and respond to such signals.
[0113] A self-contained machine vision system available from a
commercial vendor of such equipment may be employed as machine
vision system 300'. Examples of such machine vision systems and
their various features are described, without limitation, in U.S.
Pat. Nos. 4,526,646; 4,543,659; 4,736,437; 4,899,921; 5,059,559;
5,113,565; 5,145,099; 5,238,174; 5,463,227; 5,288,698; 5,471,310;
5,506,684; 5,516,023; 5,516,026; and 5,644,245. The disclosure of
each of the immediately foregoing patents is hereby incorporated
herein in its entirety by this reference. Such systems are
available, for example, from Cognex Corporation of Natick, Mass. As
an example, and not to limit the scope of the present invention,
the apparatus of the Cognex BGA Inspection Package.TM. or the SMD
Placement Guidance Package.TM. may be adapted for use in a
stereolithographic apparatus 10 (FIG. 1) that incorporates
teachings of the present invention, although it is currently
believed that the MVS-8000.TM. product family and the
Checkpoint.RTM. product line, the latter employed in combination
with Cognex PatMax.TM. software, may be especially suitable for use
in the present invention.
[0114] A response by computer 320' may be in the form of
instructions regarding the operation of a material consolidation
system 200 (FIGS. 1 and 2), such as the selectively consolidating
material consolidation system 200' shown in FIG. 6. These
instructions may be embodied as signals, or carrier waves. By way
of example only, such responsive instructions may be communicated
to controller 700 of stereolithographic apparatus 10, 10' (FIGS. 1
and 2, respectively) or directly to a processing element 205' (FIG.
6), such as a processor or group of processors, associated with a
material consolidation system 200 (FIGS. 1 and 2) (e.g., material
consolidation system 200' shown in FIG. 6) with which machine
vision system 300' is used. Controller 700 or control element 205'
may, in turn, cause material consolidation system 200' to operate
in such a way as to effect the stereolithographic fabrication of
one or more objects on fabrication substrate 50 precisely at the
intended locations thereof.
[0115] Due to the close proximity of camera 310' to surface 128
(FIG. 1), the field of vision of camera 310' is relatively small.
In order to enable camera 310' to view a larger area of surface 128
than that which is "covered" by or located within the field of
vision camera 310', a scan element 312' of a known type is
configured to traverse camera 310' over at least part of the area
of surface 128. Scan element 312' is also useful for moving camera
310' out of the path of any selectively consolidating energy being
directed toward surface 128. By way of example only, scan element
312' may comprise an X-Y plotter or scanner of a known type.
Generally, an X-Y plotter or scanner includes an x-axis element
313' and a y-axis element 315' that intersect one another. As
depicted, camera 310' is carried by both x-axis element 313' and
y-axis element 315' and, thus, is positioned at or near the
location where x-axis element 313' and y-axis element 315'
intersect one another.
[0116] X-axis element 313' and y-axis element 315' are both
configured to move relative to and, thus, to position camera 310'
at a plurality of locations over a fabrication substrate 50.
Movement of x-axis element 313' is effected by an actuator 314'
(e.g., a stepper motor and actuation system, such as a gear or
wheel that moves x-axis element 313' along a track) that has been
operatively coupled thereto, with actuator 314' being configured to
cause x-axis element 313' to move laterally (i.e., perpendicular to
the length thereof) along a y-axis. Y-axis element 315' is
operatively coupled to an actuator 316' therefor, which is
configured to cause y-axis element 315' to move laterally along an
x-axis. Actuators 314' and 316' may be configured to move their
respective x-axis element 313' and y-axis element 315' in a
substantially continuous fashion or in an incremental fashion.
Movement of actuators 314' and 316' may be controlled by a
processing element such as computer 320' or a scanning controller
326', such as a processor or smaller group of logic circuits, that
is dedicated to operation of scan element 312' and which may
communicate with computer 320' in such a way as to provide computer
320' with information as to the specific location of camera 310'
relative to surface 128 (FIG. 1).
[0117] FIG. 9 shows an embodiment of machine vision system 300"
that includes a camera 310" which is mounted or otherwise secured
in a fixed position relative to surface 128 and may be maintained
in a fixed position relative to a chamber 110 of a fabrication tank
100 (FIGS. 1 and 2) with which machine vision system 300" is to be
used. By way of example only, camera 310" may be positioned in
close proximity to a mirror 214' of material consolidation system
200' (FIG. 6) or at any other location which will provide camera
310" with a substantially unobstructed field of vision that covers
the areas within which fabrication substrates 50 may be
located.
[0118] Like camera 310', which is described in reference to FIG. 8,
camera 310" may comprise a CCD camera, a CMOS camera, or any other
suitable type of camera. As camera 310" is positioned farther away
from a fabrication substrate 50 to be viewed thereby, however,
camera 310" may have an effectively larger field of vision than
camera 310'. Of course, suitable optical and/or digital
magnification technology may be associated with camera 310" to
provide the desired level of resolution. Further, although camera
310" may be locationally stationary, a suitable gimbals structure
with rotational actuators may be employed to point camera 310" at a
specific location in the field of exposure with little actual
rotational movement. Thus, camera 310" may be used for both broad,
or "macro," vision and viewing and inspection of miniature
features.
[0119] While machine vision system 300" lacks a scan element, the
remaining features thereof may be the same as and operate in the
same or a similar manner to the corresponding features of machine
vision system 300', which is described in reference to FIG. 8.
Cleaning Component
[0120] Exemplary embodiments of cleaning components 400 that may be
used with a stereolithographic apparatus 10 that incorporates
teachings of the present invention, shown in FIG. 1, are depicted
in FIGS. 4, 10, and 11.
[0121] The embodiment of cleaning component 400' shown in FIG. 4 is
configured to be used with a fabrication tank 100" that is
configured like the one shown in FIG. 4. Cleaning component 400'
may include an initial material removal component 410' which is
configured to remove excess unconsolidated material 126 from a
fabrication substrate 50, an applicator 420' which is configured to
introduce one or more cleaning agents 127 (e.g., water, solvents,
detergents, etc.) onto at least an exposed surface of fabrication
substrate 50, and a secondary material removal component 430' that
removes cleaning agents 127 and any residual unconsolidated
material 126 from fabrication substrate 50.
[0122] Initial material removal component 410' of cleaning
component 400' comprises support system 130" of fabrication tank
100", as well as material reclamation zone 170" of chamber 110" and
receptacle 172" of fabrication tank 100". Support system 130" and,
in particular, actuation element 146" or rotation element 148"
thereof, is configured to accelerate rotation of a fabrication
substrate 50 carried thereby to a relatively high speed (e.g.,
about 50 to about 6,000 rpm) in such a way that any unconsolidated
material 126 thereon will be forced therefrom under centrifugal
force along substantially the same plane as that within which
fabrication substrate 50 is located, into receptacle 172", and
prevented from falling into reservoir 120".
[0123] Optionally, a protective cover 175 may be positioned beneath
support element 132" and over surface 128 of volume 124 of
unconsolidated material 126. Of course, protective cover 175 is
configured to be placed in the appropriate location in such a way
as to avoid contact with positioning element 140". Accordingly,
protective cover 175 may include two or more sections 175a, 175b,
one or more of which is configured to accommodate positioning
element 140" upon being moved into position. Each section 175a,
175b of protective cover 175 may, for example, be moved into
position in a hinged fashion (i.e., about hinges 177), as depicted,
or by horizontally sliding each section 175a, 175b into position.
In order to move protective cover 175 into position, it may be
operably coupled with an actuator 176 (e.g., a motor). Operation of
actuator 176 and, thus, movement of protective cover 175 may be
directed by controller 700 or by a processing element 178, such as
a processor or smaller group of logic circuits, that is dedicated
for use with cleaning component 400'.
[0124] As an alternative to forcing excess unconsolidated material
126 which is removed from fabrication substrate 50 into receptacle
172" by rotating, or spinning, unconsolidated material 126 may be
caused to fall into reservoir 120" and, thus, captured directly
thereby.
[0125] Once excess unconsolidated material 126 has been
substantially removed from fabrication substrate 50, positioning
element 140" is moved to raise support element 132" from material
reclamation zone 170" to cleaning zone 180".
[0126] By way of example only, applicator 420' may comprise a fixed
or movable high-pressure spray nozzle or group of nozzles that form
a spray head 421', which is in flow communication with a source
422' of cleaning agent 127 (e.g., water, solvents for
unconsolidated material 126, detergents, etc.). Applicator 420' is
configured to be oriented so as to direct one or more cleaning
agents 127 into chamber 110" of fabrication tank 100" and onto an
exposed surface of a fabrication substrate 50 that is carried by
support system 130" and located within cleaning zone 180" of
chamber 110".
[0127] Applicator 420' may be located in a fixed position relative
to fabrication tank 100" or carried by a movable element 424', such
as a robotic arm, which is configured to position applicator 420'
so as to orient the same toward fabrication substrate 50, as
depicted in FIG. 4.
[0128] Controller 700 or one or more dedicated processing elements
426' (e.g., a processor, a smaller group of logic circuits, etc.)
that communicate with controller 700, may communicate with
applicator 420' and its associated movable element 424', if any.
Accordingly, operation of applicator 420', including, without
limitation, the orientation of spray head 421' and the application
of cleaning agent 127 onto a surface of fabrication substrate 50,
may be performed under the direction of either controller 700 or a
dedicated processing element 426'.
[0129] Like initial material removal component 410', secondary
material removal component 430' of cleaning component 400' includes
support system 130" of fabrication tank 100". In addition,
secondary material removal component 430' includes cleaning zone
180" and receptacle 182 thereof of chamber 110". Support system
130" and, in particular, actuation element 146" or rotation element
148" thereof, is configured to accelerate rotation of a fabrication
substrate 50 carried thereby to a sufficiently high speed (e.g.,
about 50 to about 6,000 rpm) so that any cleaning agents 127 or
unconsolidated material 126 thereon will be forced therefrom along
substantially the same plane as that within which fabrication
substrate 50 is located, into receptacle 172", and prevented from
falling into reservoir 120".
[0130] Optionally, positive air pressure, which may be supplied by
use of a so-called "air knife," that depicted and described in
reference to FIG. 11, may be positioned over each fabrication
substrate 50 following the cleaning process to dry any residual
cleaning agents 127 therefrom.
[0131] A variation of cleaning component 400' does not comprise
part of a fabrication tank 100" but, rather, is separate therefrom
so as to completely avoid the potential for contamination of
unconsolidated material 126 within reservoir 120" with excess
unconsolidated material 126 being removed from fabrication
substrate 50 with cleaning agents 127.
[0132] Turning now to FIG. 10, another exemplary embodiment of
cleaning component 400" is depicted. Cleaning component 400"
includes a material removal component 410" and a wash element 420",
as well as a support element 430" upon which one or more
fabrication substrates 50 are supported while material removal
component 410" and wash element 420" perform their intended
tasks.
[0133] Material removal component 410", which is positioned
external to fabrication tank 100", may comprise one or more removal
heads 412", through which either a negative pressure (e.g., a
vacuum) or a positive pressure (e.g., about 30 psi (which is
typically not sufficient to puncture the skin of an operator of
stereolithographic apparatus 10, 10') or higher pressures may be
used and delivered by a so-called "air knife", such as that
manufactured by Secomak Ltd. of Middlesex, United Kingdom, at a
sufficient velocity to overcome the adhesion of unconsolidated
material 126 from fabrication substrate 50 and, thus, remove
unconsolidated material 126 from fabrication substrate 50) may be
applied to a fabrication substrate 50. Each removal head 412" may
be supported by a positioning element 414", such as a robotic arm.
Positioning element 414" places removal head 412" in sufficient
proximity to one or more surfaces of a fabrication substrate 50 so
that a negative pressure (e.g., a vacuum) or positive pressure
applied to fabrication substrate 50 by removal head 412" may
respectively draw any excess unconsolidated material 126 on
fabrication substrate 50 into removal head 412" or blow any excess
unconsolidated material 126 from fabrication substrate 50.
Alternatively, support element 430" may be transported so as to
move fabrication substrate 50 in proximity to one or more removal
heads 412". Material removal component 410" may be used in
combination with a bulk removal process, such as tipping or
inverting a fabrication substrate 50 to permit unconsolidated
material 126 to flow therefrom.
[0134] As fabrication substrate 50 is brought in proximity to wash
element 420" or wash element 420" is brought into proximity to
fabrication substrate 50, support element 430" may remain secured
to fabrication substrate 50. As shown, wash element 420" may
include one or more spray heads 421" that communicate with a source
422" of cleaning agent 127 and which may be oriented to direct
cleaning agent 127 onto fabrication substrate 50.
[0135] Any cleaning agent 127 that remains on fabrication substrate
50 may be removed therefrom by way of one or more removal heads
412", which may include at least one removal head 412" that was
used to remove excess unconsolidated material 126 from fabrication
substrate 50 or a different removal head 412".
[0136] Another embodiment of cleaning component 400'" that may be
used in a stereolithography apparatus 10, 10' (FIGS. 1 and 2,
respectively) according to the present invention is shown in FIG.
11. Cleaning component 400'" includes a tank 440'" which is at
least partially filled with one or more cleaning agents 127 and
within which one or more fabrication substrates 50 may be
introduced, such as by the illustrated wafer boat 450'".
Additionally, cleaning component 400'" may include an agitation
system 460'", which facilitates the removal of residual
unconsolidated material from fabrication substrates 50. By way of
example only, agitation system 460'" may include a vertical
agitation system, which repeatedly moves a support 452'" upon which
wafer boat 450'" is carried up and down.
[0137] As another alternative, a rotary wash system (not shown),
such as that available from Semitool of Kalispel, Mont., may be
used to remove any residual unconsolidated material from one or
more fabrication substrates.
Material Reclamation System
[0138] Again referring to FIGS. 4 and 10, an exemplary embodiment
of material reclamation system 500, shown in FIG. 1, is
illustrated.
[0139] As depicted in FIG. 4, material reclamation system 500
includes a collection conduit 510 which includes a first end 512
that communicates with receptacle 172" of cleaning component 400'
so as to receive excess unconsolidated material 126 which has been
collected by receptacle 172". When used with the embodiment of
cleaning component 400" that is shown in FIG. 10, first end 512 of
collection conduit 510 communicates with material removal component
410", such as a negative pressure head, so as to collect excess
unconsolidated material 126 that has been drawn into material
removal component 410".
[0140] The opposite, second end 514 of collection conduit 510
communicates with either reservoir 120', 120", as shown, or an
external reservoir 158' (FIG. 3C) in communication therewith.
Accordingly, unconsolidated material 126 may be returned to
reservoir 120', 120", or 158' through collection conduit 510.
[0141] One or more filters 530, which are configured to permit the
passage of unconsolidated material 126 therethrough while trapping
particulate contaminants that are larger than a selected size, may
also be positioned along the length of collection conduit 510 or at
an end 512, 514 thereof.
[0142] One or more pumps 520 (e.g., peristaltic pumps) may
communicate with collection conduit 510, each applying either a
positive or negative pressure thereto, to facilitate the transport
of unconsolidated material 126 therethrough, as well as the return
of unconsolidated material 126 to reservoir 120', 120", 158'
through conduit 510.
Calibration of the Programmed Material Consolidation Apparatus
[0143] With returned reference to FIGS. 1, 2, and 6, as well as
with reference to FIG. 12, machine vision system 300 (e.g., either
a movable machine vision system 300', such as that shown in FIG. 8,
or a stationary machine vision system 300", such as that shown in
FIG. 9) may be used to calibrate stereolithographic apparatus 10,
10' and, more particularly, material consolidation system 200
(e.g., the selective material consolidation system 200' shown in
FIG. 6) thereof. Various types of calibration may be effected,
including, but not limited to, calibration of the position (X-Y) at
which a selectively consolidating energy, such as laser beam 220',
impinges upon surface 128 of volume 124 of unconsolidated material
126, calibration of the magnification of machine vision system 300
and required movement of the selectively consolidating energy to
effect fabrication of a structure of desired dimensions, and
calibration of the "squareness" of a grid of locations at which the
selectively consolidating energy impinges upon surface 128.
[0144] The position at which selectively consolidating energy
impinges upon surface 128 may, by way example only, be calibrated
by selectively consolidating unconsolidated material 126 at one or
more calibration locations, each of which is referred to herein as
a "reference pixel" surface 128. Next, each reference pixel 750 is
"viewed" by machine vision system 300 to locate the same relative
to a reference grid (not shown), which may be stored in memory of
either computer 320' (FIG. 8) or controller 700 (FIG. 1). The
location at which each reference pixel 750 actually appears is then
compared with the anticipated location 750' for reference pixel
750. Material consolidation system 200, the reference grid, or a
combination of both may then be adjusted, as known in the art, to
compensate for any difference between anticipated location 750' and
the actual location of reference pixel 750.
[0145] The magnification with which a movable machine vision system
300', such as that shown in FIG. 8, views objects that are located
within or exposed to chamber 110 may be determined by moving camera
310' a fixed distance and determining the number of reference
pixels 750 that are "viewed" (e.g., as changes in contrast sensed
by camera 310') as camera 310' is moved. For example, if camera
310' is moved a linear distance of 10 mils (i.e., 0.010 inch) and
twenty (20) pixel widths (e.g., ten (10) pixels, each positioned
one pixel width apart from each other) are detected (e.g., as
nineteen (19) changes, or transitions, in contrast), camera 310' is
magnifying a viewed image by a value which equates to a 20:1
pixels-per-mil ratio. This process may then be repeated at least
once to check the measured magnification of camera 310'. Knowledge
of the pixel-to-mil ratio is useful for controlling the movement of
selectively consolidating energy, such as by controlling operation
of a location control element 212' (e.g., pulsing of a stepper
motor that moves a galvanometer) that moves a laser beam 220' (FIG.
6).
[0146] A calibration plate (not shown) of a known type, which, of
course, is configured specifically for the type of apparatus to be
calibrated, may be used to determine the magnification with which a
fixed camera 310" of machine vision system 300", shown in FIG. 9,
views objects that are located within or exposed to chamber 110.
The calibration plate, which is also referred to as a "prime
standard," includes features of known dimensions and locations.
These known dimensions may be compared, as known in the art, with
the image viewed by camera 310" to determine the degree to which an
image of these features is magnified or demagnified by camera
310".
[0147] The linearity with which selectively consolidating energy
impinges upon surface 128 across the field of exposure of material
consolidation system 200' may be determined and calibrated by
determining the actual locations 760 (FIG. 13), particularly at the
corners and edges of a rectangular field of exposure, at which
selectively consolidating energy, such as laser beam 220', impinges
on surface 128. The actual locations 760 at which the selectively
consolidating energy impinges on surface 128 may then be compared
to locations 760' (FIG. 13) that are anticipated if the selectively
consolidating energy were impinging on surface 128 in a linear
path. Responsive to this comparison, movement of the selectively
consolidating energy may be adjusted, or calibrated, in such a way
as to increase the linearity of the path along which the
selectively consolidating energy impinges on surface 128 and, thus,
the accuracy with which the selectively consolidating energy
impinges on surface 128, particularly at the corners and edges of
the field of exposure. In the example of a laser beam 220',
adjustments in the movement thereof may be effected by adjustments
in the manner in which location control element 212' (FIG. 6), such
as a pair of galvanometers, are moved.
[0148] With reference to FIG. 13, such linearity calibration may be
effected by positioning light-sensitive elements 770, such as
phototransistors, CCD arrays, or CMOS arrays, at selected locations
within chamber 110, such as at the four comers 116 thereof and
along the edges 118 thereof, midway between two comers 116.
Alternatively, a light-sensitive plate (not shown) of a known type
(e.g., a large phototransistor, CCD array, or CMOS array) may be
positioned within chamber 110 at an elevation which is
substantially the same as that at which surface 128 (FIG. 6) is to
be maintained during stereolithographic fabrication. As another
alternative, reference pixels 750 may be formed by use of material
consolidation system 200' (FIG. 6) and viewed by machine vision
system 300, 300', 300" (FIGS. 1, 2, 8, and 9).
Use of the Programmed Material Consolidation Apparatus
[0149] In reference again to FIGS. 1 and 2, as well as to FIG. 14,
an example of the use of a programmed material consolidation
apparatus, such as stereolithographic apparatus 10, 10', that
incorporates teachings of the present invention is described.
[0150] In order to stereolithographically fabricate one or more
objects 20, corresponding data from the .stl files, which comprise
a 3-D CAD simulation or model, resident in memory (e.g.,
random-access memory (RAM)) associated with controller 700 are
processed by controller 700. The data, which mathematically
represents the one or more objects to be fabricated, may be divided
into subsets, each subset representing a layer 22, or "slice," of
the object 20. The division of data may be effected by
mathematically sectioning the 3-D CAD model into at least one layer
22, a single layer or a "stack" of such layers 22 representing the
object 20. Each slice may be from about 0.0001 inch to about 0.0180
inch thick. A thinner slice promotes higher resolution by enabling
better reproduction of fine vertical surface features of the object
or objects to be fabricated.
[0151] Before fabrication of a first layer 22a of an object 20 is
commenced, the operational parameters for apparatus 10, 10' may be
set to adjust the size (diameter if circular) of selectively
consolidating energy (e.g., laser beam 220' shown in FIG. 6), if
such is used to at least partially consolidate unconsolidated
material 126.
[0152] In addition, controller 700 may automatically check and, if
necessary, adjust by means known in the art the elevation, or
level, of surface 128 of volume 124 of unconsolidated material 126
to maintain the same at an appropriate focal length for laser beam
220'. U.S. Pat. No. 5,174,931, the disclosure of which is hereby
incorporated herein in its entirety by this reference, discloses an
example of a suitable level control system. Alternatively, the
height of a mirror 214' (FIG. 6) that reflects laser beam 220' onto
an appropriate location of surface 128 may be adjusted responsive
to a detected elevation of surface 128 to cause the focal point of
laser beam 220' to be located precisely at surface 128, although
this approach is more complex.
[0153] A support system 130, 130', 130", 130'" upon which one or
more fabrication substrates 50 (e.g., semiconductor substrates 52)
are carried may then be submerged in unconsolidated material 126
within reservoir 120, 120', 120" to a depth equal to the thickness
of one layer 22 or slice of the object 20 to be formed so as to
form a layer 22' of unconsolidated material 126 on fabrication
substrate 50. The elevation of surface 128 may subsequently be
readjusted, as required to accommodate any differences between
unconsolidated material 126 and consolidated material 126'.
Alternatively, a layer 22' of unconsolidated material 126 may be
disposed onto an exposed upper surface 56 of fabrication substrate
50.
[0154] A machine vision system 300, 300', 300" (FIGS. 1 and 2, 8,
and 9, respectively) may then be used to view fabrication substrate
50 and to identify each location thereof over which an object 20 is
to be fabricated.
[0155] Laser 210' (FIG. 6) may then be activated so laser beam 220'
will scan surface 128 of volume 124 of unconsolidated material 126
so as to at least partially consolidate (e.g., polymerize to an at
least semisolid state) the same, thereby defining boundaries of a
layer 22 of object 20 and filling in solid portions thereof.
Support system 130, 130', 130" may then be lowered to lower
fabrication substrate 50 a distance that is substantially equal to
the desired thickness of the next layer 22 of object 20 to be
fabricated thereover, and the selective consolidation process
repeated, as often as necessary, layer by layer, until each object
20 is completed. Of course, the number of layers 22 that are
required to form object 20 may depend upon the height of object 20
and the desired thickness for each layer 22 thereof. Different
layers 22 of a stereolithographically fabricated object 20 may have
different thicknesses.
[0156] If desired, an uppermost layer 22U' of unconsolidated
material 126 may be planarized, for example, by use of a
planarizing element 195, such as that described in reference to
FIG. 4B. Planarizing elements 195 are particularly useful when one
or more layers 22' of unconsolidated material 126 are dispensed
over fabrication substrate 50 rather than being formed thereover by
submersion.
[0157] With continued reference to FIG. 14, as well as to FIG. 7,
unconsolidated material 126 of layer 22' may be consolidated with
less selectivity by exposing layer 22' to laser beam 220' which has
been emitted from laser 210' (not shown).
[0158] Although the foregoing description contains many specifics,
these should not be construed as limiting the scope of the present
invention, but merely as providing illustrations of some of the
presently preferred embodiments. Similarly, other embodiments of
the invention may be devised which do not depart from the spirit or
scope of the present invention. Moreover, features from different
embodiments of the invention may be employed in combination. The
scope of the invention is, therefore, indicated and limited only by
the appended claims and their legal equivalents, rather than by the
foregoing description. All additions, deletions, and modifications
to the invention, as disclosed herein, which fall within the
meaning and scope of the claims are to be embraced thereby.
* * * * *