U.S. patent application number 15/235934 was filed with the patent office on 2016-12-01 for etched multi-layer sheets.
The applicant listed for this patent is William HAMBURGEN, Lawrence LAM, James TANNER. Invention is credited to William HAMBURGEN, Lawrence LAM, James TANNER.
Application Number | 20160349796 15/235934 |
Document ID | / |
Family ID | 49670011 |
Filed Date | 2016-12-01 |
United States Patent
Application |
20160349796 |
Kind Code |
A1 |
HAMBURGEN; William ; et
al. |
December 1, 2016 |
ETCHED MULTI-LAYER SHEETS
Abstract
A method includes creating an opening in a first outer layer of
a multilayer sheet of material, the sheet of material having three
or more layers of material, including the first outer layer and a
second outer layer. A selective etchant is introduced through the
opening, where the etchant selectively etches an interior metal
layer of the multilayer sheet of material compared with the first
and second outer layers. The selective etchant is permitted to etch
material of the interior metal layer under the first outer
layer.
Inventors: |
HAMBURGEN; William; (Palo
Alto, CA) ; LAM; Lawrence; (San Jose, CA) ;
TANNER; James; (Los Gatos, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HAMBURGEN; William
LAM; Lawrence
TANNER; James |
Palo Alto
San Jose
Los Gatos |
CA
CA
CA |
US
US
US |
|
|
Family ID: |
49670011 |
Appl. No.: |
15/235934 |
Filed: |
August 12, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13841839 |
Mar 15, 2013 |
9445517 |
|
|
15235934 |
|
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61655240 |
Jun 4, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y10T 428/24802 20150115;
B32B 15/012 20130101; C23F 1/02 20130101; Y10T 428/24917 20150115;
Y10T 428/12347 20150115; H04M 1/0249 20130101; Y10T 428/12361
20150115; Y10T 428/24851 20150115; C22C 1/02 20130101; H05K 5/04
20130101; G06F 1/181 20130101; Y10T 428/12979 20150115; G06F 1/1633
20130101; G06F 1/1613 20130101; G06F 1/1679 20130101; Y10T 29/49002
20150115; Y10T 428/12757 20150115 |
International
Class: |
G06F 1/16 20060101
G06F001/16; C23F 1/02 20060101 C23F001/02 |
Claims
1. A method comprising: creating an opening in a first outer layer
of a multilayer sheet of material, the sheet of material having
three or more layers of material, including the first outer layer
and a second outer layer; introducing a selective etchant through
the opening, wherein the etchant selectively etches an interior
metal layer of the multilayer sheet of material compared with the
first and second outer layers; and permitting the selective etchant
to etch material of the interior metal layer under the first outer
layer.
2. The method of claim 1, wherein the first outer layer includes
stainless steel.
3. The method of claim 1, wherein the first outer layer includes a
glass-reinforced epoxy laminate.
4. The method of claim 1, wherein the interior metal layer includes
aluminum.
5. The method of claim 1, wherein creating the opening includes:
applying a layer of photoresist to the first outer layer; exposing
the layer of photoresist to a pattern of radiation; developing the
photoresist; selectively removing photoresist material from the
first outer layer to leave the pattern of the radiation in the
photoresist on the first outer layer; and applying a chemical to
the first outer layer, wherein the chemical selectively attacks the
exposed material of the first outer layer compared with the resist
material and compared with the first outer layer under the pattern
of resist material.
6. The method of claim 1, wherein the selective etchant etches the
interior metal layer at a rate more than 100 times faster than the
selective etchant etches the first outer layer.
7. The method of claim 1, wherein permitting the selective etchant
to etch material of the interior metal layer under the first outer
layer includes forming a cavity in the interior metal layer; and
further comprising: placing an electrical component of a computing
device within the cavity.
8. The method of claim 1, further comprising: creating a pattern of
openings in the first outer layer; introducing the selective
etchant through the pattern of openings; and permitting the
selective etchant to etch material of the interior metal layer in a
plurality of locations under the first outer layer.
9. The method of claim 8, further comprising adding a phase change
material to the multilayer sheet to replace at least some of the
material from the interior metal layer that is removed by the
selective etchant.
10. The method of claim 1, wherein the sheet of material has an
area that is greater than about 30 in.sup.2 and a thickness that is
less than about 2 mm.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional of U.S. application Ser.
No. 13/841,839, filed Mar. 15, 2013, and also claims priority to,
U.S. Provisional Application No. 61/655,240, filed on Jun. 4, 2012,
the disclosures of which are hereby incorporated herein by
reference in their entirety.
TECHNICAL FIELD
[0002] This description relates generally to multi-layer sheets of
material in which different layers can be differentially etched by
an etching material to selectively remove portions of one or more
particular layers.
BACKGROUND
[0003] Sheets of material can be used as housing material for a
variety of products, such as computer cases, cell phone and
smartphone cases, etc. Because the housing walls of a product can
be a major contributor to the thickness of the product, it can be
desirable to have a thin housing wall that nevertheless has
pleasing aesthetics, such as accurate contours and flats, control
of the color, texture, reflectance, feel, etc. In addition, because
a product may have several housing walls nested within each other,
the thickness of a housing wall can have a multiplier effect on the
overall thickness of the product.
SUMMARY
[0004] This description generally describes multi-layer sheets of
materials that can be selectively etched to create sheets having an
internal structure. Such sheets can have favorable structural
properties while also being low-weight.
[0005] In one general aspect, a method includes creating an opening
in a first outer layer of a multilayer sheet of material, the sheet
of material having three or more layers of material, including the
first outer layer and a second outer layer. A selective etchant is
introduced through the opening, where the etchant selectively
etches an interior metal layer of the multilayer sheet of material
compared with the first and second outer layers. The selective
etchant is permitted to etch material of the interior metal layer
under the first outer layer.
[0006] In another general aspect, a portable computing device
includes a multilayer housing wall having three or more layers of
material. The housing wall is prepared by creating an opening in a
first outer layer of the multilayer sheet of material. A selective
etchant is introduced through the opening, wherein the etchant
selectively etches an interior metal layer of the multilayer sheet
of material compared with the first outer layer. The selective
etchant is permitted to etch material of the interior metal layer
under the first outer layer.
[0007] In another general aspect, an apparatus includes a first
multilayer sheet and a second multilayer sheet. The first
multilayer sheet has three or more layers of material. A section of
the first outer layer of the first multilayer sheet includes
flanges having a width in a direction parallel to a plane of the
layers that is greater than a width of an interior layer underlying
the section. The second multilayer sheet has three or more layers
of material, and a first outer layer of the second multilayer sheet
includes two separate sections, where each section has a flange
that extends from a portion of the outer layer of the second
multilayer sheet in a direction toward the other flange and where
each flange is not supported by an underlying interior layer of the
second multilayer sheet. The flanges of the first multilayer sheet
are located between the flanges of the second multilayer sheet and
a second outer layer of the second multilayer sheet. The first
multilayer sheet being prepared by creating an opening in the first
outer layer of the first multilayer sheet of material. A selective
etchant is introduced through the opening, where the etchant
selectively etches an interior metal layer of the first multilayer
sheet of material compared with the first outer layer. The
selective etchant is permitted to etch material of the interior
metal layer under the first outer layer. The second multilayer
sheet is prepared by creating an opening in the first outer layer
of the second multilayer sheet of material. A selective etchant is
introduced through the opening, where the etchant selectively
etches an interior metal layer of the second multilayer sheet of
material compared with the first outer layer. The selective etchant
is permitted to etch material of the interior metal layer under the
first outer layer.
[0008] The details of one or more implementations are set forth in
the accompa-nying drawings and the description below. Other
features will be apparent from the description and drawings, and
from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIGS. 1A and 1B are schematic diagrams of a beam of material
illustrating parameters that affect the stiffness of the beam.
[0010] FIG. 2 is an example perspective view of a system for
producing a sheet material composed of dissimilar metals that are
pressed together, whereby they become metallurgically bonded.
[0011] FIG. 3 is a schematic diagram of a metallurgical bond
between two dissimilar metals.
[0012] FIGS. 4A and 4B are schematic diagrams of a multilayer sheet
having outer layers of stainless steel and a middle layer of
aluminum.
[0013] FIGS. 5A and 5B are schematic cross-sectional diagrams of a
multilayer sheet of material.
[0014] FIG. 6 is a schematic diagram of a multilayer sheet and
example components of an electronic product.
[0015] FIG. 7 is another schematic diagram of a multilayer sheet
and example components of an electronic product.
[0016] FIG. 8A is a schematic cross-sectional diagram of multilayer
sheet having an etched cavity that is filled with a molding
material.
[0017] FIG. 8B is a top view of a top layer of the sheet shown in
FIG. 8A.
[0018] FIG. 9 is a schematic cross-sectional diagram of another
multilayer sheet that includes a middle layer sandwiched between a
top layer and a bottom layer.
[0019] FIG. 10 is a schematic cross-sectional diagram of another
multilayer sheet that includes a middle layer sandwiched between a
top layer and a bottom layer.
[0020] FIG. 11 is a bottom view of the multilayer sheet of FIG. 9
through line A-A' in FIG. 9.
[0021] FIG. 12 is a top view of a multilayer sheet.
[0022] FIG. 13 is a schematic cross-sectional diagram of two
interlocking multilayer sheets.
[0023] FIG. 14 is a schematic cross-sectional diagram of another
multilayer sheet.
[0024] FIG. 15 is a schematic cross-sectional diagram of another
multilayer sheet 1500.
[0025] FIG. 16 is a schematic cross-sectional diagram of another
multilayer sheet 1600.
[0026] FIG. 17A is a schematic cross-sectional diagram of another
multilayer sheet 1700.
[0027] FIG. 17B and FIG. 17C are schematic cross-sectional diagrams
of another way of forming multilayer sheet having a corner
bend.
[0028] FIG. 18A is a schematic cross-sectional diagram of a
plurality of multilayer sheets.
[0029] FIG. 18B is a schematic cross-sectional diagram of a single
multilayer sheet that has been annealed and removed from the stack
of sheets shown in FIG. 18A and formed.
DETAILED DESCRIPTION
[0030] FIGS. 1A and 1B are schematic diagrams of a beam of material
illustrating parameters that affect the stiffness of the beam 100.
As shown in FIG. 1A, the parameter, L, is the span of the beam 100
between two support points 102, 104 at the ends of the beam. The
parameter, P, is a force applied to the beam 100, and the
parameter, E, represents the modulus of elasticity of the beam. The
parameter, I, is a moment of inertia for the beam 100, which is
proportional to a cube of the thickness of the beam. As shown in
FIG. 1B, the stiffness of a beam can be defined in terms of the
force required to create a particular maximum deflection value
(y.sub.max), and the stiffness (P/y.sub.max) can be proportional to
EI/L.sup.3. For a solid beam with a square cross-section of the
stiffness is equal to 48EI/L.sup.3.
[0031] To improve the stiffness of a beam, it may desirable to
focus first on the cubed terms, i.e. the moment of inertia, I,
which is proportional to the cube of the thickness of the beam and
the span, L. Thus, a product designer may desire to design a
product in which long spans are avoided and in which locally short
spans are used with thin walls over tall components housed within
the product. Additionally, the product designer may want to tightly
control the thickness of the product walls. As described herein,
etched multilayer sheets offer a structure to precisely control the
thickness of the housing walls of a product so that the wall can be
relatively thick for long spans and thin for short spans that are
used to enclose tall components within the housing.
[0032] FIG. 2 is an example perspective view of a system 200 for
producing a sheet material composed of dissimilar metals that are
pressed together, whereby they become metallurgically bonded. The
system can include rollers 202A, 202B, 204A, 20fB that apply
pressure to sheets or material 204, 206 to press the sheets of
material together to bond the sheets of material to create a single
multi-layer sheet 208. Although two sheets of material 204, 206 are
shown in FIG. 2, it is understood that more than two sheets of
material can be bonded together simultaneously. FIG. 3 is a
schematic diagram of a metallurgical bond between two dissimilar
metals, i.e., a first metal material 302 and a second metal
material 304. For dissimilar metals having different thermal
expansion coefficients, an asymmetric multilayer stack of the
bonded material can be distorted or deformed due to temperature
changes. A symmetric multilayer stack (i.e., having top and bottom
layers of a first material that sandwich a middle layer of a second
material) may not be prone to distortion or deformation due to
temperature changes.
[0033] For example, a multilayer sheet having top and bottom layers
comprised of stainless steel, or a stainless steel alloy, and a
middle layer comprised of aluminum or an aluminum alloy can offer
several advantages. It is understood that when a layer is described
in this description as being composed of a particular sort of
material (e.g., aluminum), it is understood that the material can
include an alloy of the named material, except where the material
is explicitly described as being composed of only the named
material.
[0034] The creation of a multilayer sheet through the rolling
process described above with respect to FIG. 2 can allow tight
control of the thickness of the multilayer sheet. A symmetric
multilayer sheet 208 having outer layers of stainless steel and an
inner layer of aluminum can be relatively stiff because the
stainless steel layers, which have a modulus of elasticity that is
on the order of three times that of the aluminum layer are located
far from the central axis of the multilayer sheet. However, the
stainless-aluminum-stainless multilayer sheet can be lighter than a
solid stainless steel sheet of similar thickness because the
density of aluminum is approximately three times less than the
density of stainless steel. Moreover, the thermal conductivity of a
stainless-aluminum-stainless sheet can be superior to that of a
solid stainless steel sheet because the thermal conductivity of
aluminum is approximately 10 times greater than that of stainless
steel.
[0035] As described herein, when starting with a multi-layer sheet
(e.g., a stainless-aluminum-stainless multilayer sheet), one or
more openings can be created in one of the outer layers (e.g., a
stainless steel layer), and then an etching material can be
provided through the opening(s), where the etchant selectively
etches the inner layer (e.g., the aluminum layer) to create unique
structures within the multilayer sheet.
[0036] For example, as shown in FIG. 4A, in a multilayer sheet
having outer layers 402A, 402B of stainless steel and a middle
layer 404 of aluminum, an opening can be created in one of the
stainless steel layers 402A (and possibly also through a portion of
the aluminum layer). The opening can be created in a number of
different ways. For example, the opening can be created
mechanically (e.g., by milling or drilling through the layer),
thermally (e.g., by intense laser radiation), or chemically (e.g.,
by etching with a chemical). When creating one or more openings in
a multilayer sheet using a chemical process, a resist material can
be applied to a surface of the sheet, and then a pattern can be
created in the resist material (e.g., by exposing the resist
material to a pattern of radiation). Then, the resist material
(e.g. dry film photoresist) can be developed, and resist material
can be selectively removed to leave the pattern of the resist
material on the surface of the multilayer sheet. Then, a chemical
(e.g., ferric chloride) can be applied to the surface of the sheet,
where the chemical attacks the exposed metal of the multilayer
sheet but not the resist material or the metal under the pattern of
resist material.
[0037] After creation of the openings through the top layer of
stainless steel, a selective etching material can be provided
through the opening to selectively attack the inner layer of
aluminum, to remove portions of the aluminum layer that extend
underneath the top layer of stainless steel, as shown in FIG. 4B. A
variety of different etchants can be used that selectively etch
aluminum but that have relatively little effect on stainless steel.
For example, sodium hydroxide is an etchant that aggressively
attacks aluminum but that leaves most other metals alone under
normal etching temperatures. Sodium hydroxide can etch pure
aluminum at a faster rate than aluminum alloys (e.g., on the order
of 30% faster) and can etch both pure aluminum and aluminum alloys
at a much faster rate than stainless steel (e.g., at a rate
hundreds or thousands of times faster). Potassium hydroxide has
similar properties to those of sodium hydroxide and is another
possible etchant. If a resist material has been applied to a
surface of the multilayer sheet, the resist material can be removed
either after creating the opening in the top stainless steel layer
402A or after applying the selective etchant that attacks the
aluminum metal layer 404.
[0038] FIGS. 5A and 5B are schematic cross-sectionals diagram of a
multilayer sheet of material. The sheet of material can include
outer stainless steel layers 502A, 502B and an inner aluminum layer
504. A minimum depth "pilot opening" 506 can be created in a top
stainless steel layer, and then etchant can be introduced to the
middle aluminum layer through the pilot opening 506. Then, a
selective etchant can be introduced through the pilot opening 506,
and the etchant can attack the middle aluminum layer 504 and
selectively remove the aluminum, as shown in FIG. 5B. An idealized
spherical etch front 508A, 508B is depicted in FIG. 5B, although a
typical etch front is usually flatter than what is depicted in FIG.
5B. A comparison of FIG. 4B and FIG. 5B reveals that although the
profile of the opening in the aluminum layer 402A, 502A may depend
somewhat on the depth of the initial pilot opening 406, 506 and the
maximum diameter of the opening 406, 506 in the aluminum layer, it
does not depend on the depth of the initial opening 406, 506.
Therefore, the depth of the initial opening 406, 506 into the inner
layer 404, 504 need not be precisely controlled, and the thickness
of the metal layers 402A, 402B, 502A, 502B can be precisely
maintained over a broad range of initial opening depths and etching
conditions.
[0039] These techniques of selectively etching the middle layer
404, 504 of a multilayer sheet can be used to create structures in
the housing walls for electronic products. For example, multilayer
sheets having an etched middle layer can be used as the housing
walls of computers or mobile phones. For example, the sheet of
material can form one of the external walls of a portable computing
device (e.g., a mobile phone, a tablet computer, a notebook
computer). When used as an external wall of a mobile phone, the
sheet of material can have an area that is greater than about 6
in.sup.2 and can have a thickness that is less than about 2 mm.
When used as an external wall of a tablet computer or a notebook
computer, the sheet of material can have an area that is greater
than about 30 in.sup.2 and the thickness that is less than about 2
mm. The portable computing device that includes etched multilayer
housing walls can include a plurality of integrated circuits (e.g.,
a central processing unit, a memory, etc.) mounted on a mainboard,
which is disposed inside the housing of the computing device. The
portable computing device can be, for example, a laptop computer, a
hand held computer, a tablet computer, a netbook computer, a mobile
phone, or a wearable computer a personal digital assistant.
[0040] For example, FIG. 6 is a schematic diagram of a multilayer
600 sheet and example components 612, 614, 616, 618, 620 of an
electronic product. The components 612, 614, 616, 618, 620 can be
mounted on a circuit board 630 and can be enclosed by a housing
that includes the multilayer sheet 600. The multilayer sheet 600
has a middle aluminum layer 604, sandwiched between two stainless
steel layers 602A, 602B, which can be selectively etched to make
the wall thickness of the multilayer sheet 600 locally thinner in a
region of a sheet, so that an isolated tall component 616 of the
electronic product can be accommodated by the housing wall that
includes the multilayer sheet 600. For example, inductors can be
relatively large components on printed circuit boards that protrude
up from the surface of the printed circuit board. By creating a
housing wall that is locally thin in an area near the location of
an inductor, the profile of the inductor can be accommodated by the
housing wall while maintaining a thin profile for the overall
device. The locally thin area of the housing wall also could be
used to accommodate a battery cell or could be used to create an
airflow channel around a heat-generating device within the
electronic product.
[0041] To guard against corrosion between adjacent layers of the
multilayer sheet 600, a moisture barrier can be placed over the
joint between the different layers. For example, a moisture barrier
can be placed at the joints 640, 642, 644, 646 between the aluminum
and stainless steel layers. The moisture barrier can include a
layer of wax, epoxy or thermoplastic material. The material of the
moisture barrier can be mixed with a solvent and spread along the
interface between the different layers 602A, 604, 602B. Then, when
the solvent evaporates, the moisture barrier can be left over the
joint between the different layers.
[0042] FIG. 7 is another schematic diagram of a multilayer 700
sheet and example components of an electronic product. The
multilayer sheet 700 has a middle aluminum layer 704, sandwiched
between two stainless steel layers 702A, 702B. The sheet can be
part of the housing of an electronics product. The middle layer 704
can be can be selectively etched to locally thin the sheet 700 in a
plurality of regions to accommodate various structures within the
housing of the product. For example, multiple battery cell pouches
712A, 712B having flat flanges 714A, 716A, 714B, 716B can be
accommodated, where the thick part of the pouch 712A, 712B is
positioned within the thinned part of the housing wall and the
flanges 714A, 716A, 716A, 716B of the battery cell pouches can be
overlaid on thicker portions of the housing wall. The battery cell
pouches 712A, 712B can be bonded into the cavities formed by the
removal of an inner aluminum layer 704 of the multilayer sheet
housing wall. In some implementations, the thicker portions of the
housing wall can be supported in the completed structure of the
product so that long spans of the housing wall are minimized,
thereby retaining stiffness of the housing wall. For example,
bonding material between the battery cell pouches 712A, 712B and
the stainless steel layer 702A ma create a continuous span along a
length of the multilayer sheet.
[0043] FIG. 8A is a schematic cross-sectional diagram of multilayer
sheet 800 having an etched cavity that is filled with a molding
material. The multilayer sheet 800 can include top and bottom
layers 802A, 802B that sandwich a middle layer 804. FIG. 8B is a
top view of the top layer 802A of the sheet 800. The top and bottom
layers 802A, 802B can include stainless steel and the middle layer
804 can include aluminum. As described above a cavity can be etched
within the middle layer 804 through a selective editing process.
The process can include under-cutting the middle layer 804 beneath
the top layer 802A to form a cavity within the multilayer sheet
800. After the cavity is etched, material can be molded into the
cavity. For example, after removing a portion of the middle layer
804 to form a cavity between the top and bottom layers 802A, 802B,
material 806 can be injected into the cavity and then solidified so
that the material is fixed in place. The material 806 can be a
continuous part of a molded part 808 that extends above the top
layer 802A, such that the part 808 above the top layer is firmly
attached to the sheet 800 by the molded material 806 that is molded
within the sheet.
[0044] The etched clad techniques described herein also allow
economical undercuts to create removable locking features such as
twist lock fasteners and latches (rotary), and tabs or lips
(linear). The selective etching techniques also allow locking
detent openings to be simultaneously made by the same etching
operation. For example, the dimensions of the material 806 within
the cavity in the middle layer 804 can be longer within the plane
of the page shown in FIG. 8A than in the plane that extends into
the page, and the dimensions of the opening 810 in the top layer
802A can be shorter in the plane of the page shown in FIG. 8 than
in the plane that extends into the page. For example, as shown in
FIG. 8B, a first dimension 822 of the opening can be shorter than a
second dimension 822 of the opening. Then, when the part 808 is
rotated by 90 degrees, length of the material 806 within the cavity
can be the part can be extracted from the multilayer sheet 800. For
example, as shown in FIG. 8B the width of the material 806 under
the top sheet 802A can be greater than the first dimension 820 but
smaller than the second dimension 822. Thus, when material 806 is
placed within the cavity and oriented along the direction of the
first dimension, the part is locked in place. However, when the
material 806 is oriented along the direction of the second
dimension, the part can be extracted from the multilayer sheet of
material.
[0045] FIG. 9 is a schematic cross-sectional diagram of another
multilayer sheet 900 that includes a middle layer 904 sandwiched
between a top layer 902A and a bottom layer 902B. As shown in FIG.
9, multiple cavities 904A, 904B, 904C can be formed in a multilayer
sheet of material through a selective etching process to remove
material from the sheet and therefore make the sheet lighter. The
multiple cavities can be used to house a plurality of
components.
[0046] FIG. 10 is a schematic cross-sectional diagram of another
multilayer sheet 1000 that includes a middle layer 1004 sandwiched
between a top layer 1002A and a bottom layer 1002B. As shown in
FIG. 10, allowing the etching process to continue working on the
structure shown in FIG. 9 can remove additional material from the
middle layer 1004 to create a large, continuous cavity between the
top and bottom layers. Although the middle two sections of the top
layer appear to be hovering unsupported and FIG. 10, it must be
remembered that FIG. 10 is a cross-section of a multilayer sheet of
material and shows the pilot openings 1006A, 1006B, 1006C that were
created in the top layer 1002A to introduce the etchant into the
middle layer 1004. Therefore, a view through a different section of
the multilayer sheet of material would show the top layer 1002A
extending across the entire distance from the left side to the
right side of FIG. 10, and because of this the middle two sections
of the top layer 1002A shown in FIG. 10 are supported by the rest
of the top layer of the sheet. Within the cavity 1008 formed in the
multilayer sheet shown in FIG. 10, a component 1010 of the
electronic component can be introduced. For example, the component
1010 can include a flat flexible cable, so that when the multilayer
sheet 1000 is used as a housing wall of an electronic product, the
multilayer sheet 1000 can be used to house cables for carrying
signals and power within the electronic product. In some
implementations, the component 1010 can include light emitting
devices (e.g., one or more light emitting diodes).
[0047] FIG. 11 is a bottom top view of the multilayer sheet 900
through line A-A' shown in FIG. 9. As shown in FIG. 11, a plurality
of openings 1102 can be created in the top layer 902A and etchant
can be introduced into the openings to selectively remove portions
of the middle layer 904 to create a pseudo-honeycomb structure that
can be light and stiff. Close control of the etching time allows
isolated columns or "islands" of aluminum 1104. The islands of
aluminum can reduce the risk of "doming" due to temperature
changes, where doming can be due to the different coefficients of
thermal expansion for the stainless-aluminum-stainless portions of
the sheet as compared with the stainless only portions of the sheet
in which the aluminum inner layer has been removed. Material can be
introduced between the islands of aluminum 1104. For example, a
phase change material that is used for thermal management can be
introduced in the voids formed by the removal of the portions of
the middle layer of aluminum.
[0048] FIG. 12 is a top view of a multilayer sheet. A pattern of
openings 1202, 1204, 1206, 1208 can be created in a top layer 1210
of the sheet, and then the middle layer can be attacked with an
etchant to create a design that provides structure were needed,
e.g., to provide stiffness between battery cells, and which
provides aluminum conduction paths for thermal management of heat
created from the battery packs. Aluminum has a high heat
conductivity compared to stainless steel and therefore is
advantageous for conducting heat. Although the stainless steel
outer layers have relatively low thermal conductivity they can have
a large area for coupling heat into and out of the aluminum core
structure. Other patterns can be used to manage heat from other
component types, such a transistors, integrated circuits, resistors
and inductors.
[0049] FIG. 13 is a schematic cross-sectional diagram of two
interlocking multilayer sheets 1300, 1320. As shown in FIG. 13, the
two sheets of material 1300, 1320 are coupled together. The layers
of the sheets extend into the page, and therefore sheet 1300, 1320
can slide relative to each other. For example, sheet 1320 can have
two aluminum posts 1322, 1332 topped with stainless steel sheets
1324, 1334 that extend past the edges 1323, 1333 of the posts. The
aluminum posts 1322, 1332 and the stainless steel sheets 1324, 1334
extend into the page as shown in FIG. 13. Sheet 1300 can have a
single aluminum post 1302 topped with a stainless steel sheet 1304
that extends past the edges 1306, 1308 of the post. The stainless
steel tops 1324, 1334 of sheet 1320 can interlock with the
stainless steel top 1304 of sheet 1300, so that the sheets 1300,
1320 can then slide relative to each other, into and out of the
page as shown in FIG. 13.
[0050] A variety of other structures also can be created. For
example, offset openings in the top and middle layer can create
airtight and liquid-tight passages, which could be used for
pneumatic or hydraulic logic or actuators. Passages within the
sheet could be used as electromagnetic waveguides or as acoustic
waveguides for sound.
[0051] FIG. 14 is a schematic cross-sectional diagram of another
multilayer sheet 1400. As shown in FIG. 14, a middle layer 1406 of
the multilayer sheet 1400 can be etched so that a flange 1404
extends one layer extends of the multilayer sheet. The flange 1404
can be bonded or welded to a rim 1410 of a product case. Solder or
adhesive material 1412 can be used to form the bond.
[0052] FIG. 15 is a schematic cross-sectional diagram of another
multilayer sheet 1500. As shown in FIG. 15, a middle layer 1504 of
the multilayer sheet 1500 can be etched so that one or more flanges
1502, 1512 extend from the multilayer sheet, and the one or more
flanges 1502, 1512 can be molded into a rim 1520 of a product
case.
[0053] FIG. 16 is a schematic cross-sectional diagram of another
multilayer sheet 1600. As shown in FIG. 16, a rim 1610 can be
formed directly from a multilayer sheet by bending the sheet around
a corner 1606. However, rolling of the sheet during layer
lamination to create the multilayer sheet work hardens the
stainless steel layers 1602A, 1602B, such that the stainless steel
layers of a flat multilayer sheet are typically 1/4 to 3/4 hard,
such that the multilayer sheet typically has limited formability
and has a tendency to crack when bent, particularly when bent in
corners. To ameliorate the problem of cracking, the stainless steel
layers could be partially annealed, e.g., through laser annealing,
or stress relieving could be used by holding the sheet at a high
temperature that is nevertheless below the melting temperature of
the aluminum layer for several hours.
[0054] FIG. 17A is a schematic cross-sectional diagram of another
multilayer sheet 1700. As shown in FIG. 17A, two independent
stainless steel layers 1702A, 1702B sandwich a middle aluminum
layer 1704 of the multilayer sheet 1700. The stainless steel layers
1702A, 1702B can slide over each other during the process of
forming the multilayer sheet to allow a tighter radius of a corner
1706 of the sheet. As shown in FIG. 17A, a clamp having a first
part 1710 and a second part 1712 can be applied to the full
thickness of the multilayer sheet to form the corner in both
stainless steel layers. The clamp 1710, 1712 then can be removed
after the corner is formed.
[0055] FIG. 17B and FIG. 17C are schematic cross-sectional diagrams
of another way of forming multilayer sheet having a corner bend. In
the implementation shown in FIG. 17B and FIG. 17C, the two outer
stainless steel layers can first be squeezed together by a clamp
having a first part 1720 and a second part 1722 to form an offset
bend in the multilayer sheet. Then, as shown in FIG. 17C, a corner
1706 can be formed by a second clamp having a first part 1730, a
second part 1732, and a third part 1734. The two outer stainless
steel layers 1702A, 1702B can be welded or bonded during or after
the forming and clamping process to stiffen the edge and
corner.
[0056] FIG. 18A is a schematic cross-sectional diagram of a
plurality of multilayer sheets. As shown in FIG. 18A, annealing of
the stainless steel outer layers can be performed to improve
formability of the rolled multilayer sheets. For example, prior to,
or after, stacking the sheets, a plurality of rolled multilayer
sheets (e.g., that comprise stainless steel outer layers 1802A,
1802B, 1812A, 1812B, 1822A, 1822B, and an aluminum inner layer
1804, 1814, 1824) can have a portion 1806, 1816, 1826 of the
aluminum inner layers 1804, 1814, 1824 at an edges of the sheets
removed by an etching process. Then, the stainless steel outer
layers at the edge of the sheets where the aluminum inner layer has
been etched can be annealed. Annealing can be performed with a hot
gas or a reducing flame 1830, and aluminum heatsink plates 1840,
1842, 1844, 1846 can prevent overheating of the aluminum-stainless
steel bondline of the multilayer sheets. In another implementation,
the stainless steel edges of the multilayer sheets can be
selectively laser annealed just at bend zone 1850, where the
stainless steel sheets will be bent. In addition to annealing by
laser or flame or hot gas, selective annealing of the stainless
steel portions can also be performed via contact with a hot platten
or thermode, or by immersing the edge in a hot liquid, such as
solder or a molten salt.
[0057] FIG. 18B is a schematic cross-sectional diagram of a single
multilayer sheet that has been annealed and removed from the stack
of sheets shown in FIG. 18A. In the implementation shown in FIG.
18B, a corner 1830 can be formed by a clamp having a first part
1830, a second part 1832, and a third part 1834. The two outer
stainless steel layers 1802A, 1802B can be welded or bonded during
or after the forming and clamping process to stiffen the edge and
corner.
[0058] Although the foregoing description is focused on
stainless-aluminum-stainless multilayer sheets, multilayer sheets
of many other materials are also possible. For example, other
metals such as low-carbon steel, nickel, copper, etc. could be
used, and nonmetal materials such as: glass-reinforced epoxy
laminate sheets (e.g., FR 4), including active printed circuit
boards with cables, antennas, etc.; exotic epoxy-fiber composite
sheets, including graphite, aramid, alumina, etc. materials; molded
housings with laminated interior aluminum layers and cap layers;
physical vapor deposition ceramics with sprayed on aluminum
layers.
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