U.S. patent application number 14/874235 was filed with the patent office on 2016-02-04 for high strength carbon fiber composite wafers for microfabrication.
The applicant listed for this patent is Brigham Young University, Moxtek. Inc.. Invention is credited to Andrew L. Davis, Robert C. Davis, Steven D. Liddiard, Richard Vanfleet, Kyle Zufeldt.
Application Number | 20160031188 14/874235 |
Document ID | / |
Family ID | 49621601 |
Filed Date | 2016-02-04 |
United States Patent
Application |
20160031188 |
Kind Code |
A1 |
Davis; Robert C. ; et
al. |
February 4, 2016 |
High Strength Carbon Fiber Composite Wafers For
Microfabrication
Abstract
A method of making a high strength carbon fiber composite (CFC)
wafer with low surface roughness comprising at least one sheet of
CFC including carbon fibers embedded in a matrix. A stack of at
least one sheet of CFC is provided with the stack having a first
surface and a second surface. The stack is pressed between first
and second pressure plates with a porous breather layer disposed
between the first surface of the stack and the first pressure
plate. The stack is cured by heating the stack to a temperature of
at least 50.degree. C.
Inventors: |
Davis; Robert C.; (Provo,
UT) ; Vanfleet; Richard; (Provo, UT) ;
Zufeldt; Kyle; (Orem, UT) ; Davis; Andrew L.;
(Provo, UT) ; Liddiard; Steven D.; (Springville,
UT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Brigham Young University
Moxtek. Inc. |
Provo
Orem |
UT
UT |
US
US |
|
|
Family ID: |
49621601 |
Appl. No.: |
14/874235 |
Filed: |
October 2, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13667273 |
Nov 2, 2012 |
9174412 |
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14874235 |
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|
13453066 |
Apr 23, 2012 |
8989354 |
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13667273 |
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61689392 |
Jun 6, 2012 |
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61486547 |
May 16, 2011 |
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61495616 |
Jun 10, 2011 |
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61511793 |
Jul 26, 2011 |
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Current U.S.
Class: |
428/136 ;
156/247; 156/250; 156/272.8; 156/285; 156/306.9; 156/307.1;
428/141 |
Current CPC
Class: |
B32B 3/266 20130101;
H01J 35/18 20130101; B32B 27/06 20130101; B32B 2260/023 20130101;
B32B 37/18 20130101; B32B 2307/542 20130101; B32B 2551/00 20130101;
B32B 2262/106 20130101; B32B 2379/08 20130101; B32B 2307/40
20130101; B32B 37/06 20130101; B32B 2260/04 20130101; B32B 2307/54
20130101; B32B 37/10 20130101; H01J 5/18 20130101; G21K 1/00
20130101; B32B 7/02 20130101; H01J 9/24 20130101; Y10T 428/24124
20150115; H01J 2235/183 20130101; B32B 27/34 20130101; B32B 2313/04
20130101; B32B 18/00 20130101; H01J 2235/18 20130101; B29K 2307/04
20130101; B32B 2377/00 20130101 |
International
Class: |
B32B 18/00 20060101
B32B018/00; B32B 37/10 20060101 B32B037/10; B32B 27/34 20060101
B32B027/34; B32B 37/18 20060101 B32B037/18; B32B 3/26 20060101
B32B003/26; B32B 27/06 20060101 B32B027/06; H01J 5/18 20060101
H01J005/18; B32B 37/06 20060101 B32B037/06 |
Claims
1. A method of making a wafer, the method comprising: a. providing
a stack of at least one sheet of carbon fiber composite (CFC)
including carbon fibers embedded in a matrix, the stack having a
first surface and a second surface; b. pressing the stack between
first and second pressure plates with a porous breather layer
disposed between the first surface of the stack and the first
pressure plate; and c. curing by heating the stack to a temperature
of at least 50.degree. C., defining a first curing process.
2. The method of claim 1, further comprising disposing a solid,
polished layer between the second surface of the stack and the
second pressure plate during the first curing process with the
polished layer having a root mean square surface roughness Rq of
less than 300 nm in an area of 100 micrometers by 100 micrometers,
on a side facing the stack.
3. The method of claim 1, further comprising: a. releasing pressure
from the stack; b. removing the porous layer from the stack; c.
disposing a polished layer on each side of the stack, the polished
layers having a root mean square surface roughness Rq of less than
300 nm in an area of 100 micrometers by 100 micrometers, on a side
facing the stack; and d. pressing the stack and polished layers
between first and second pressure plates; e. curing by heating the
stack to a temperature of at least 50.degree. C., defining a second
curing process.
4. The method of claim 1, wherein the porous breather layer
comprises a porous polymer layer facing the stack and a nylon mesh
facing the first pressure plate.
5. The method of claim 1, wherein providing the stack includes a
sheet of polyimide disposed adjacent to the second surface of the
stack.
6. The method of claim 1, wherein curing by heating the stack
includes creating a vacuum of less than 50 torr between the
pressure plates, and maintaining the vacuum through at least 50% of
the curing process.
7. The method of claim 1, wherein each sheet in the stack has a
thickness of between 20 to 350 micrometers.
8. The method of claim 1, further comprising micropatterning the
wafer by laser ablation, water jet, or combinations thereof to form
an x-ray window support structure comprising: a. a support frame
defining a perimeter and an aperture; b. a plurality of ribs
extending across the aperture of the support frame and carried by
the support frame; c. openings between the plurality of ribs; and
d. the support frame and the plurality of ribs comprising a support
structure.
9. The method of claim 1, wherein at least 90% of the carbon fibers
have a diameter of between 2 and 10 micrometers.
10. The method of claim 1, wherein the matrix comprises a material
selected from the group consisting of polyimide, bismaleimide,
epoxy, or combinations thereof.
11. The method of claim 1, wherein the matrix comprises a material
selected from the group consisting of amorphous carbon,
hydrogenated amorphous carbon, nanocrystalline carbon,
microcrystalline carbon, hydrogenated nanocrystalline carbon,
hydrogenated microcrystalline carbon, or combinations thereof.
12. The method of claim 1, wherein the matrix comprises a ceramic
material selected from the group consisting of silicon nitride,
boron nitride, boron carbide, aluminum nitride, or combinations
thereof.
13. The method of claim 1, further comprising a polyimide sheet
cured together with and abutting the at least one sheet of carbon
fiber composite.
14. The method of claim 13, wherein the polyimide sheet has a
thickness of between 0.1-100 micrometers.
15. The method of claim 1, wherein the matrix comprises
polyimide.
16. The method of claim 1, wherein the matrix comprises
bismaleimide.
17. A wafer formed by the method of claim 1, wherein the wafer
comprises: a. a wafer thickness of between 10-500 micrometers; b.
at least one side of the wafer having a root mean square surface
roughness Rq of less than 300 nm in an area of 100 micrometers by
100 micrometers and less than 500 nm along a line of 2 millimeter
length; c. a yield strength at fracture of greater than 0.5
gigapascals (GPa), wherein yield strength is defined as a force, in
a direction parallel with a plane of a side of the wafer, per unit
area, to cause the wafer to fracture; and d. a strain at fracture
of more than 0.01, wherein strain is defined as the change in
length caused by a force in a direction parallel with a plane of
the wafer divided by original length.
18. The wafer of claim 17, wherein the yield strength is between 2
GPa and 3.6 GPa.
19. The wafer of claim 17, wherein the root mean square surface
roughness is less than 200 nanometers in an area of 100 micrometers
by 100 micrometers.
20. The wafer of claim 17 micropatterned by laser ablation, water
jet, or combinations thereof to form an x-ray window support
structure comprising: a. a support frame defining a perimeter and
an aperture; b. a plurality of ribs extending across the aperture
of the support frame and carried by the support frame; c. openings
between the plurality of ribs; and d. the support frame and the
plurality of ribs comprising a support structure.
Description
CLAIM OF PRIORITY
[0001] This is a divisional of U.S. patent application Ser. No.
13/667,273, filed Nov. 2, 2012; which claims priority to U.S.
Provisional Patent Application Ser. No. 61/689,392, filed on Jun.
6, 2012; and which is a continuation-in-part of U.S. patent
application Ser. No. 13/453,066, filed on Apr. 23, 2012, which
claims priority to U.S. Provisional Patent Application Nos.
61/486,547, filed on May 16, 2011; 61/495,616, filed on Jun. 10,
2011; and 61/511,793, filed on Jul. 26, 2011; all of which are
hereby incorporated herein by reference in their entirety.
FIELD OF THE INVENTION
[0002] The present application is related generally to high
strength microstructures, such as for example x-ray window support
structures.
BACKGROUND
[0003] Carbon fiber composite (CFC) wafers can be used in
applications where high strength is desired. Barriers to the
development of carbon fiber based structures, especially structures
with micrometer-sized features, include difficulties in machining
or patterning, and high surface roughness of cured composites. A
root mean square surface roughness Rq of typical CFC wafers can be
greater than 1 micrometer. Root mean square surface roughness Rq
can be defined by the following equation: R.sub.q= {square root
over (.SIGMA.z.sub.i.sup.2)}. In this equation, z represents a
height of the surface at different measured locations i.
SUMMARY
[0004] It has been recognized that it would be advantageous to have
a carbon fiber composite wafer having high strength and low surface
roughness.
[0005] In one embodiment, the present invention is directed to a
method of making a carbon fiber composite (CFC) wafer that
satisfies the needs for high strength and low surface roughness.
The method comprises pressing a stack of at least one sheet of CFC
between pressure plates with a porous breather layer disposed
between at least one side of the stack and at least one of the
pressure plates; then heating the stack to a temperature of at
least 50.degree. C. to cure the stack into a CFC wafer.
[0006] In another embodiment, the present invention is directed to
a carbon fiber composite (CFC) wafer that satisfies the needs for
high strength and low surface roughness. The CFC wafer comprises at
least one sheet of CFC including carbon fibers embedded in a
matrix. The wafer can have a thickness of between 10-500
micrometers. The wafer can have a root mean square surface
roughness Rq, on at least one side, of less than 300 nm in an area
of 100 micrometers by 100 micrometers and less than 500 nm along a
line of 2 millimeter length. The wafer can have a yield strength at
fracture of greater than 0.5 gigapascals, wherein yield strength is
defined as the force, in a direction parallel with a plane of the
wafer, per unit area, to cause the wafer to fracture. The wafer can
have a strain at fracture of more than 0.01, wherein strain is
defined as the change in length caused by a force in a direction
parallel with a plane of the wafer divided by original length.
[0007] In another embodiment, the present invention is directed to
an x-ray window including a high strength support structure. The
x-ray window can comprise a support frame defining a perimeter and
an aperture with a plurality of ribs extending across the aperture
of the support frame and carried by the support frame. Openings
exist between the plurality of ribs. The support frame and the
plurality of ribs comprise a support structure. A film can be
disposed over, can be carried by, and can span the plurality of
ribs and can be disposed over and can span the openings. The film
can be configured to pass x-ray radiation therethrough. The support
structure can comprise a carbon fiber composite material (CFC). The
CFC material can comprise carbon fibers embedded in a matrix. A
thickness of the support structure can be between 10-500
micrometers. A root mean square surface roughness Rq of the support
structure on a side facing the film can be less than 500 nm along a
line of 2 millimeter length.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic top view of a carbon fiber composite
wafer, in accordance with an embodiment of the present
invention;
[0009] FIGS. 2-3 are schematic cross-sectional side views of a
carbon fiber composite wafer, in accordance with an embodiment of
the present invention;
[0010] FIG. 4 is a schematic cross-sectional side view of portion
of a carbon fiber composite wafer, showing measurement of root mean
square surface roughness Rq, in accordance with an embodiment of
the present invention;
[0011] FIG. 5 is a side view of a carbon fiber, in accordance with
an embodiment of the present invention;
[0012] FIG. 6 is a schematic cross-sectional side view of wafer
including multiple carbon fiber composite sheets abutting a
polyimide sheet, in accordance with an embodiment of the present
invention;
[0013] FIG. 7 illustrates a first curing process for manufacture of
a carbon fiber composite wafer, in accordance with a method of the
present invention;
[0014] FIG. 8 illustrates use of o-rings and a vacuum during the
first curing process for manufacture of a carbon fiber composite
wafer, in accordance with a method of the present invention;
[0015] FIG. 9 illustrates a second curing process for manufacture
of a carbon fiber composite wafer, in accordance with a method of
the present invention;
[0016] FIG. 10 is a schematic top view of an x-ray window support
structure, in accordance with an embodiment of the present
invention;
[0017] FIG. 11 is a schematic cross-sectional side view of an x-ray
window, in accordance with an embodiment of the present
invention;
[0018] FIG. 12 is a schematic cross-sectional side view of an x-ray
detector, including an x-ray window, in accordance with an
embodiment of the present invention.
DEFINITIONS
[0019] As used herein, the term "carbon fiber" or "carbon fibers"
means solid, substantially cylindrically shaped structures having a
mass fraction of at least 85% carbon, a length of at least 5
micrometers and a diameter of at least 1 micrometer.
[0020] As used herein, the term "directionally aligned," in
referring to alignment of carbon fibers with support structure
members (such as ribs for example), means that the carbon fibers
are substantially aligned with a longitudinal axis of the support
structure members and does not require the carbon fibers to be
exactly aligned with a longitudinal axis of the support structure
members.
[0021] As used herein, the term "porous" means readily permeable to
gas.
DETAILED DESCRIPTION
[0022] Illustrated in FIGS. 1-3 are carbon fiber composite (CFC)
wafers 10 and 20 comprising at least one CFC sheet 21 including
carbon fibers 12 embedded in a matrix 11. The matrix can comprise a
material that provides sufficient strength and is compatible with
the use of the wafer. For example, if the wafer will be used to
fabricate an x-ray window support structure, considerations for
matrix material may include a low atomic number elements and low
outgassing. The matrix can comprise a material selected from the
group consisting of polyimide, bismaleimide, epoxy, or combinations
thereof. The matrix can comprise a material selected from the group
consisting of amorphous carbon, hydrogenated amorphous carbon,
nanocrystalline carbon, microcrystalline carbon, hydrogenated
nanocrystalline carbon, hydrogenated microcrystalline carbon, or
combinations thereof. The matrix can comprise a ceramic material
selected from the group consisting of silicon nitride, boron
nitride, boron carbide, aluminum nitride, or combinations
thereof.
[0023] The carbon fibers 12 can be directionally aligned in a
single direction Al, directionally aligned in multiple directions,
or disposed in random directions in the matrix. Three CFC sheets
21a-c are shown in FIGS. 2-3. There may be more or less CFC sheets
21 than 3, depending on the desired application. The wafer 20 can
have a thickness Th.sub.w of between 10-500 micrometers in one
aspect, between 20 and 350 micrometers in another aspect, less than
or equal to 20 micrometers in another aspect, or greater than or
equal to 350 micrometers in another aspect.
[0024] CFC wafers per the present invention can have high yield
strength. A yield strength at fracture can be greater than 0.1
gigapascals (GPa) in one aspect, greater than 0.5 GPa in another
aspect, greater than 2 GPa in another aspect, between 2 GPa and 3.6
GPa in another aspect, or between 0.5 GPa and 6 GPa in another
aspect. Yield strength can be defined as a force F in a direction
parallel with a plane 33 or 34 of a side 32a or 32b of the wafer,
per unit area, to cause the wafer to fracture. If fibers are
directionally aligned, the force F can be aligned parallel with the
fibers.
[0025] CFC wafers per the present invention can have high strain. A
strain at fracture can be greater than 0.01 in one aspect, greater
than 0.03 in another aspect, greater than 0.05 in another aspect,
or between 0.01 and 0.080 in another aspect. Strain can be defined
as the change in length L caused by a force F in a direction
parallel with a plane 33 or 34 of the wafer divided by original
length L. If fibers are directionally aligned, the force F can be
aligned parallel with the fibers.
[0026] The wafer can have two faces or sides 32a-b and an edge 31.
The sides 32a-b can have a substantially larger surface area than
the edge 31. The sides 32a-b can be substantially parallel with
each other. One side 32a can be disposed along, or parallel with, a
single plane 33; and the other side 32b can be disposed along, or
parallel with, a different single plane 34.
[0027] At least one side 32a and/or 32b of the wafer can be smooth,
i.e. can have a low surface roughness. A low surface roughness can
be beneficial for improving adhesion to other materials, such as to
an x-ray window film for example. One measurement of surface
roughness is root mean square surface roughness Rq calculated by
the equation R.sub.q= {square root over (.SIGMA.z.sub.i.sup.2)}.
The measurement z.sub.i can be made along a surface of the wafer by
an atomic force microscope. The measurement of z.sub.i on a portion
of the wafer 40 is shown in FIG. 4. A distance from a plane 43,
substantially parallel with the wafer, or substantially parallel
with the sides 32a and 32b of the wafer, can differ by small
amounts. These small variations can be recorded, squared, summed,
then a square root may be taken of this sum to calculate root mean
square surface roughness Rq. A low Rq number can indicate a low
surface roughness. The root mean square surface roughness Rq of one
or both sides of the wafers of the present invention can be less
than 300 nm in one aspect, or between 30 nm and 300 nm in another
aspect, in an area of 100 micrometers by 100 micrometers. The root
mean square surface roughness Rq of one or both sides of the wafers
of the present invention can be less than 500 nm in one aspect, or
between 50 nm and 500 nm in another aspect, along a line of 2
millimeter length. The root mean square surface roughness Rq of one
or both sides of the wafers of the present invention can be less
than 200 nanometers in one aspect, or between 20 nm and 200 nm in
another aspect, in an area of 100 micrometers by 100
micrometers.
[0028] Shown in FIG. 5 is a side view of a carbon fiber 12, in
accordance with an embodiment of the present invention. At least
50% of the carbon fibers 12 in a wafer can have a diameter D of
between 2 and 10 micrometers in one aspect. At least 90% of the
carbon fibers 12 in a wafer can have a diameter D of between 2 and
10 micrometers in another aspect. Substantially all of the carbon
fibers 12 in a wafer can have a diameter D of between 2 and 10
micrometers in another aspect.
[0029] As shown on wafer 60 in FIG. 6, a polyimide sheet 61 can be
cured together with and can abut the sheet(s) 21 of carbon fiber
composite. The polyimide sheet can have a thickness Th.sub.p, after
curing, of between 0.1-100 micrometers.
[0030] Also shown on wafer 60 in FIG. 6 are carbon fiber composite
sheet thicknesses Th.sub.a-c. Each carbon fiber composite sheet
21a-c in the stack can have a thickness Th.sub.a-c of between 20 to
350 micrometers (20 .mu.m<Th.sub.a<350 .mu.m, 20
.mu.m<Th.sub.b<350 .mu.m, and 20 .mu.m<Th.sub.c<350
.mu.m) in one aspect, less than or equal to 20 micrometers in
another aspect, or greater than or equal to 350 micrometers in
another aspect. There may be more or less than the three carbon
fiber composite sheets 21a-c. These thicknesses are sheet 21
thicknesses after curing.
[0031] FIG. 7 illustrates a first curing process 70 for manufacture
of a carbon fiber composite wafer, in accordance with a method of
the present invention. The method can comprise providing a stack 71
of at least one sheet of CFC 21a-c, the stack having a first
surface 32a and a second surface 32b; pressing P the stack between
a first pressure plate 76a and a second pressure plate 76b with a
porous breather layer 72 disposed between the first surface 32a of
the stack and the first pressure plate 76a; and curing by heating
the stack 71 to a temperature of at least 50.degree. C. (defining a
first curing process). The amount of pressure to be used can depend
on the matrix of the carbon composite. Pressure in the range of
50-200 psi has been successfully used. Pressure may be in the range
of 25-500 psi.
[0032] A solid, polished layer 73 can be disposed between the
second surface 32b of the stack 71 and the second pressure plate
76b during the first curing process. The polished layer 73 can help
create a very smooth surface on the second surface 32b of the stack
71. The polished layer 73 can be a highly polished sheet of
stainless steel, a silicon wafer, or a glass plate. A fluorine
release layer can be used to avoid the stack sticking 71 to the
polished layer 73. For example, a fluorinated alkane monolayer can
be deposited on silicon wafers to facilitate release by placing in
a vacuum desiccator overnight with 5 mL of
Trichloro(1H,1H,2H,2H-perfluorooctyl)silane in a glass vial. The
polished layer 73 can have a root mean square surface roughness Rq
of less than 300 nm in an area of 100 micrometers by 100
micrometers, on a side facing the stack. Thus, it is not necessary
for the polished layer 73 to have a polished surface on both
sides.
[0033] A polyimide sheet 61 can be cured together with and can abut
the CFC sheet(s) 21. The polyimide sheet 61 can be disposed between
the second surface 32b of the stack 71 and the second pressure
plate 76b. The polyimide sheet 61 can be disposed between the
second surface 32b of the stack 71 and the polished layer 73 (if a
polished layer is used). Alternatively, a polyimide sheet 61 can be
disposed on both surfaces 32a and 32b of the stack 71. The
polyimide sheet(s) 61 can be useful for improving the surface of
the final wafer and/or for improving adhesion of the stack 71 to
other materials.
[0034] The porous layer 72 can allow gas, emitted by the stack, to
escape from the press. A multi-layer porous breather layer 72 can
be used. For example, the porous breather layer 72 can comprise a
porous polymer layer 72b facing the stack 71 and a nylon mesh 72a
facing the first pressure plate 76a. A vacuum can aid in removal of
the gas. A vacuum pump 75 can be attached by tubing 74 to the press
and can draw a vacuum, such as less than 50 torr, between the
pressure plates. The vacuum can be maintained through substantially
all of the curing process, or through only part of the curing
process, such as at least 50% of the curing process.
[0035] Shown in FIG. 8 are more details of the press and vacuum.
The layers (stack of CFC, porous breather layer 72, optional
polished layer 73, and optional polyimide layer 61) 81 can be in a
central portion of the pressure plates 76a-b. An o-ring 82 can
surround the layers 81. The o-ring 82 can be disposed at least
partly in a channel 83 of at least one of the pressure plates 76a
and/or 76b. The vacuum tube 74 can extend into the central portion
of the press, between the layers 81 and the o-ring 82.
[0036] FIG. 9 illustrates a second curing process 90 for
manufacture of a carbon fiber composite wafer in accordance with a
method of the present invention. After completion of the first
curing process 70, pressure P can be released from the stack and
the porous layer 72 can be removed from the stack. A polished layer
73a and 73b can be disposed on each side of the stack. Note that if
there was a polyimide sheet 61 in the first curing process, this
polyimide sheet 61 can remain for the second curing process 90. The
polished layers 73a and 73b can have a root mean square surface
roughness Rq of less than 300 nm in an area of 100 micrometers by
100 micrometers, on a side facing the stack. The stack 71 (and
optional polyimide sheet 61 if one is used) can be pressed between
the polished layers by the first and second pressure plates 76a-b.
The stack 71 (and optional polyimide layer 61) can be cured by
heating the stack to a temperature of at least 50.degree. C.
[0037] A benefit of use of the second curing process 90 is that the
gas can be removed during the first curing process 70, then
polished layers 73a and 73b can be disposed on both sides 32a and
32b of the stack 71, with the result that both sides of the wafer
can be highly polished. Thus, both sides of the wafer can have a
root mean square surface roughness Rq as specified above.
[0038] Shown in FIG. 10 is a support structure 100 for an x-ray
window. The support structure 100 can comprise a support frame 101
defining a perimeter 104 and an aperture 105. A plurality of ribs
102 can extend across the aperture 105 of the support frame 101 and
can be carried by the support frame 101, with openings 103 between
the ribs 102. The support frame 101 and the plurality of ribs 102
can comprise a support structure 100. The support structure 100 can
comprise a carbon fiber composite (CFC) material. The CFC material
can comprise carbon fibers embedded in a matrix. Carbon fibers 12
in the composite can be substantially aligned with a direction Al
of the ribs, with at least one direction of the ribs if the ribs
extend in multiple directions, or with all directions of all ribs
if the ribs extend in multiple directions.
[0039] Carbon fibers in a carbon fiber composite can be graphitic,
and thus can be highly resistant to chemical etching. Alternative
methods have been found for etching or cutting micro-sized
structures in CFC wafers in the present invention. The support
structure 100 may be made by cutting a CFC wafer to form ribs 102
and openings 103. The CFC wafer may be cut by laser milling or
laser ablation. A high power laser can use short pulses of laser to
ablate the material to form the openings 103 by ultrafast laser
ablation. A femtosecond laser may be used. A nanosecond pulsed YAG
laser may be used. Ablating wafer material in short pulses of high
power laser can be used in order to avoid overheating the CFC
material. Alternatively, a non-pulsing laser can be used and the
wafer can be cooled by other methods, such as conductive or
convective heat removal. The wafer can be cooled by water flow or
air across the wafer. The above mentioned cooling methods can also
be used with laser pulses, such as a femtosecond laser, if
additional cooling is needed.
[0040] As shown in FIG. 11, the support structure 100 can have a
thickness Th.sub.s of between 10-500 micrometers. Tops of the ribs
102 and support frame 101 can terminate substantially in a single
plane 116. A film 114 can be disposed over, can be carried by, and
can span the plurality of ribs 102 and can be disposed over and can
span the openings 103. The film 114 can be configured to pass
radiation therethrough, such as by being made of a material and
thickness that will allow x-ray radiation to pass through with
minimal attenuation of x-rays and/or minimal contamination of the
x-ray signal.
[0041] As described above regarding FIGS. 6-9, a polyimide layer 61
can be cured abutting the CFC stack 71. The polyimide layer 61 can
be cut into polyimide ribs 111 and a polyimide support frame 112,
with openings 103 between the ribs 111, along with the CFC stack
71. The polyimide ribs 111 and the polyimide support frame 112 can
be part of the support structure 100. The polyimide ribs 111 and
the polyimide support frame 112 can be disposed between the CFC
stack 71 and the film 114.
[0042] A surface of the support structure 100 facing the film can
have low surface roughness. This surface can be CFC 71 or can be
polyimide 61. This surface can have a root mean square surface
roughness Rq of less than 300 nm in one aspect, or between 30 nm
and 300 nm in another aspect, in an area of 100 micrometers by 100
micrometers. This surface can have a root mean square surface
roughness Rq of less than 500 nm in one aspect, or between 50 nm
and 500 nm in another aspect, along a line of 2 millimeter length.
This surface can have a root mean square surface roughness Rq of
less than 200 nanometers in one aspect, or between 20 nm and 200 nm
in another aspect, in an area of 100 micrometers by 100
micrometers.
[0043] The ribs 102 can have a strain at fracture of greater than
0.01 in one aspect, greater than 0.03 in another aspect, greater
than 0.05 in another aspect, or between 0.01 and 0.080 in another
aspect. Strain can be defined as a change in length caused by a
force in a direction parallel with the ribs divided by original
length. If fibers are directionally aligned, the force F can be
aligned parallel with the fibers.
[0044] The wafers described herein can also be micropatterned by
laser ablation and/or water jet to form other structures, such as a
flexure mechanical mechanism, a mesoscale mechanical mechanism, a
microscale mechanical mechanism, and/or elements in a
microelectromechanical system (MEMS).
[0045] As shown in FIG. 12, an x-ray window 125, including a
support structure 100 and a film 114, can be hermetically sealed to
a housing 122. The housing can contain an x-ray detector 123. The
x-ray detector can be configured to receive x-rays 124 transmitted
through the window, and to output a signal based on x-ray
energy.
* * * * *