U.S. patent application number 15/889791 was filed with the patent office on 2018-06-14 for shaping of brittle materials with controlled surface and bulk properties.
The applicant listed for this patent is Coherent, Inc.. Invention is credited to Timothy BOOTH, David M. GAUDIOSI, Eric JUBAN, Michael MIELKE, Michael SHIRK, Ramanujapuram A. SRINIVAS.
Application Number | 20180161918 15/889791 |
Document ID | / |
Family ID | 51387337 |
Filed Date | 2018-06-14 |
United States Patent
Application |
20180161918 |
Kind Code |
A1 |
SRINIVAS; Ramanujapuram A. ;
et al. |
June 14, 2018 |
SHAPING OF BRITTLE MATERIALS WITH CONTROLLED SURFACE AND BULK
PROPERTIES
Abstract
Methods of and devices for forming edge chamfers and through
holes and slots on a material that is machined using a laser, such
as an ultrafast laser. The shaped material has predetermined and
highly controllable geometric shape and/or surface morphology.
Further, a method of and a device for preventing re-deposition of
the particles on a material that is machined using a laser, such as
an ultrafast laser. A fluid is used to wash off the particles
generated during the laser machining process. The fluid can be in a
non-neutral condition, with one or more chemical salts added, or a
condition allowing the coagulation of the particles in the fluid,
such that the particles can be precipitated to avoid the
reattachment to the machined substrate.
Inventors: |
SRINIVAS; Ramanujapuram A.;
(Santa Clara, CA) ; GAUDIOSI; David M.; (Santa
Rosa, CA) ; BOOTH; Timothy; (Penngrove, CA) ;
SHIRK; Michael; (Brentwood, CA) ; JUBAN; Eric;
(Petaluma, CA) ; MIELKE; Michael; (Petaluma,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Coherent, Inc. |
Santa Clara |
CA |
US |
|
|
Family ID: |
51387337 |
Appl. No.: |
15/889791 |
Filed: |
February 6, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14186238 |
Feb 21, 2014 |
9919380 |
|
|
15889791 |
|
|
|
|
61768467 |
Feb 23, 2013 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C03B 33/04 20130101;
C03B 33/0222 20130101; B23K 26/354 20151001 |
International
Class: |
B23K 26/00 20060101
B23K026/00; C03B 33/04 20060101 C03B033/04; C03B 33/02 20060101
C03B033/02 |
Claims
1. An apparatus for laser processing a stock of brittle material,
the stock of brittle material having a front surface and an
opposite back surface, the apparatus comprising: a material holder
for supporting the stock of brittle material; a fluid reservoir
holding a liquid solution and positioned such that the back surface
of the stock of brittle material is contact with the liquid
solution, the liquid solution having a zeta potential of less than
about 10 mV; and a laser generating pulsed laser beam, said pulses
being in the picosecond or femtosecond range, and with the focus of
the laser beam being adjustable such that during processing, the
laser beam is incident on the front surface of the stock of brittle
material and wherein the focus of the laser beam is initially at
the back surface of the stock of brittle material and then the
focus is moved towards the front surface of the stock of brittle
material in order to removed material from the stock of brittle
material by ablation, the material removed by ablation being in the
form of debris particles, the liquid solution coagulating the
debris particles in the liquid solution, the liquid solution
thereby preventing the material removed by ablation from
reattaching to the stock of brittle material.
2. The apparatus of claim 1, wherein the liquid solution includes a
salt.
3. The apparatus of claim 2, wherein the salt is any one of
CaCl.sub.2, MgCl.sub.2, and NaCl, or a combination thereof.
4. The apparatus of claim 2, wherein the salt is a divalent
salt.
5. The apparatus of claim 1, wherein the liquid solution has a
non-neutral pH value.
6. The apparatus of claim 1, wherein the liquid solution has a pH
value lower than 5.
7. The apparatus of claim 1, wherein the debris particles removed
by ablation are one of nanoparticles and microparticles, or a
combination thereof.
8. The apparatus of claim 1, wherein the material removed by
ablation is colloidal silica.
9. The apparatus of claim 1, wherein the laser beam is scanned
along a tool path, the focused laser beam removing material from
the stock of brittle material along the tool path.
10. The apparatus of claim 9, wherein a second laser beam is
directed onto the stock of brittle material, the second laser beam
following the tool path and causing a controlled separation of the
stock of brittle material into at least two portions of brittle
material.
11. The apparatus of claim 1, wherein the laser pulses are in the
picosecond range.
12. The apparatus of claim 1, wherein the laser pulses are in the
femtosecond range.
13. The apparatus of claim 1, wherein the laser processing forms a
through hole or slot in the stock of brittle material.
14. The apparatus of claim 13, wherein the through hole or slot has
a chamfer.
15. The apparatus of claim 13, wherein the through hole or slot has
edges that are round in shape, the round shape having a radius of
curvature.
16. The apparatus of claim 1, wherein the stock of brittle material
comprises a multiple layered structure of brittle material.
17. The apparatus of the claim 16, wherein the laser beam is
focused on one layer of the multiple layered structure of brittle
material.
18. The apparatus of claim 1, wherein the stock of brittle material
is made of glass.
19. The apparatus of claim 1, wherein the stock of brittle material
is made of a consumer electronic protective glass.
20. The apparatus of claim 1, wherein the stock of brittle material
is made of sapphire.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application claims priority under 35 U.S.C. .sctn.
119(e) of the U.S. Provisional Patent Application Ser. No,
61/768,467, filed Feb. 23, 2013 and titled, "SHAPING OF BRITTLE
MATERIALS WITH CONTROLLED SURFACE AND BULK PROPERTIES," which is
hereby incorporated by reference in its entirety for ail
purposes.
FIELD OF THE INVENTION
[0002] The present invention relates to material processing. More
specifically, the present invention relates to systems for and
methods of shaping brittle materials.
BACKGROUND OF THE INVENTION
[0003] Shaping is a material modification process that often
involves the application of chemical processes and/or mechanical
forces to materials, particularly brittle materials, such as glass,
sapphire, or silicon. Other common examples of materials that are
often processed to create products via shaping include, but are not
limited to, amorphous solid materials, crystalline materials,
semiconducting materials, crystalline ceramics, polymers, and
resins.
[0004] Typical techniques for shaping brittle materials include
mechanical saw processes, scribe and break, direct laser machining,
laser thermal shock cleaving, mechanical grinding, mechanical
polishing, abrasive liquid erosion, flow honing, chemical etching,
or a combination of mechanical, laser, liquid and chemical steps.
Although the net results of these techniques are somewhat different
from one another, they all share the drawback of insufficient
control of the as-shaped surface or bulk properties.
[0005] Brittle materials are used in multiple commercial markets
for consumer, industrial and medical goods. There are aspects to be
taken into consideration when processing and manufacturing products
with brittle materials.
[0006] In the aspect of a material cutting/processing speed,
multiple figures of merit (FOM) are used in commercial markets for
quantifying the effective brittle materials shaping speed. For
example, the linear cutting speed can be calculated by dividing the
total length of material cut by the total cutting time, which
generates an effective cutting speed with measurement units in
meters per second (m/s). Depending on the exact material species,
material thickness and desired surface characteristics, the
effective cutting speed can also be in the units of millimeters per
second (minis).
[0007] Takt time, cycle time, is another example of an FOM for
quantifying the effective shaping speed for brittle materials,
which is the time required to produce a unit of the shaped portion
of brittle material from an initial substrate of brittle material.
The Takt time for a production line is often characterized by
number of seconds, or minutes, required to produce a unit. The Takt
time calculation can include the linear cutting speed as a
variable. The Takt time can also include additional steps required
to produce the finished unit as variables in the calculation, such
as grinding, polishing, etching, annealing, chemical bath, or
ion-exchange treatment.
[0008] In the material property aspect, brittle materials can be
characterized by the lack of plastic deformation prior to breaking
when a stress is applied to the material. When subjected to stress,
a brittle material breaks without significant deformation (strain).
This property is not exclusive of strength, since some brittle
materials can be very strong, such as diamond, sapphire or
strengthened glass.
[0009] In the manufacturing aspect, brittle materials can be
especially challenging to shape (e.g., cut, drill or mill), with
controlled surface properties since these materials tend to chip
and/or crack using typical methods. These defects are usually the
result of "brittle fracture," which are cracks that propagate
through a stressed material along paths of least resistance. The
intrinsic microscopic stress anisotropy of brittle materials,
and/or the randomized local stress applied by traditional shaping
tools, imposes uncontrolled surface shape and/or surface morphology
on the as-shaped edge. This uncontrolled edge quality can result
from cracks running along transgranular pathways in the brittle
material tracing the lattice orientation within each microscopic
grain element in the material. Similarly, the uncontrolled edge
quality can result from cracks running along intergranular pathways
in the brittle material traversing the grain boundaries between
individual grain elements in the material. The limitations of
controlling the as-cut edge quality of a brittle material with
traditional techniques are depending upon the grain size in the
material and/or the dislocation mobility allowed by the grain
structure.
[0010] Typical methods of shaping brittle materials fail to control
the as-shaped surface shape and/or surface morphology since they
apply a force (such as mechanical and/or thermal) that often leads
to crack propagation along native crystallographic planes of high
shear stress of the brittle material. Defects within the bulk of
the brittle material substrate can be the result of the crystal
growth process, impurities, or the stochastic grain pattern.
Similarly, defects at the surface of the brittle material substrate
can result from the crystal growth process, impurities, the
stochastic grain pattern, or the substrate forming process, e.g.,
melting, drawing, fusing, slicing, lapping or machining. The
uncontrolled crack propagation common with the typical methods can
be caused by the shaping tool. Mechanical shaping tools can have
microscopically random shapes, hardnesses, and/or applied forces.
Thermal shaping tools can create microscopically random heat
distributions in the brittle material.
[0011] FIG. 1A illustrates a typical method 100 of cutting a stock
of brittle material 101 (hereinafter "material" 101) using a
typical tool 102 such as a mechanical diamond-tipped saw. When the
typical tool 102 is applied on the material 101, a
cutting/breaking/cracking line 104 is created. A first portion 106
and a second portion 108 are formed by separating the material 101
into two or more pieces. The material 101, such as a brittle
material, forms rough surfaces 110 when the typical tool 102 is
applied to cut the material 101.
[0012] FIG. 1B illustrates three rough surfaces 112, 114, and 116
made by using typical methods and devices for cutting a brittle
material. The rough surfaces 112, 114, and 116 have respectively
large, medium and small roughness profiles of the brittle material
101 created by application of the typical tool 102. When the size
(length in any directions) of the defect 118 is greater than a size
of a critical defect, such as equal to or greater than 10-20
microns, the brittle material 101 can crack or become easy to break
at a predetermined amount of impact of force,
[0013] Although the typical methods of and devices for brittle
materials surface shaping have allowed shaping into predetermined
shapes, these typical methods and devices impose uncontrollable
surface properties in the resultant surface as shown in FIG. 1B.
Multiple-process fabrication protocols are therefore required in
the typical process and methods, whereby the shaped surface is
subsequently conditioned to achieve the desired surface properties,
which are time consuming and associated with higher manufacturing
costs. For example, an electronic display panel comprising thin
glass typically exhibits micro-cracks and chips of uncontrolled
dimensions along the shaped surface(s), and these features are
typically removed via multiple steps of fine grit polishing of the
surface(s) in the typical methods. Polishing, grinding, lapping,
etching, sanding, annealing, and/or chemical bath are part of the
subsequent steps for after-shaped edge treatment process in the
typical methods.
SUMMARY OF THE INVENTION
[0014] According to some embodiments, the present invention is
directed toward methods of and systems for material shaping. In
some embodiments, the methods and systems include directing one or
more tools to a portion of brittle material causing separation of
the material into two or more portions, where the as-shaped surface
has a predetermined and highly controllable geometric shape and/or
surface morphology. The one or more tools can comprise energy
delivered to the material without making physical contact, for
example from a laser beam or acoustic beam. In some embodiments,
one or more of the separated portions of material comprise
fragmented or particulate material and can further comprise waste
debris.
[0015] In some embodiments, the present invention is directed
toward devices that shape brittle material. These devices comprise
tools, or combinations of tools, for separating a brittle material
into two or more portions, where the as-shaped edge has a
predetermined and highly controllable geometric shape and/or
surface morphology. The one or more tools comprise energy delivered
to the material without making physical contact, for example from a
laser beam or acoustic beam. In some embodiments, one or more of
the separated portions of material comprise fragmented or
particulate material and can further comprise waste debris.
[0016] In some embodiments, the present invention is directed
toward the separate portions of a material created by a process. In
some embodiments, the process includes: (a) providing a stock of
brittle material and (b) applying one or more laser beams to a
portion of the brittle material causing separation of the material
into two or more portions in a way that precisely controls the
geometric shape and/or surface morphology of the edge(s) of at
least one of the separate portions. In some embodiments, one or
more of the separated portions of material comprise fragmented or
particulate material and can further comprise waste debris.
[0017] In one exemplary embodiment, the present invention is
directed toward methods of and systems for brittle material
shaping. The methods and systems include directing one or more
laser beams to a portion of the brittle material causing a
separation of the material into two or more portions, where at
least one of the portion surfaces created by the laser beam
exposure have a predetermined and highly controllable geometric
shape and/or surface morphology. In some embodiments, one or more
of the separated portions of material comprise fragmented or
particulate material and can further comprise waste debris.
[0018] In another exemplary embodiment, the present invention is
directed to devices that shape brittle materials. These devices
comprise one or more lasers and the laser beam directing mechanisms
for exposing a portion of the brittle material to the laser light
causing separation of the brittle material into two or more
portions, where at least one of the resultant portion surfaces
created by the laser exposure have a predetermined and highly
controllable geometric shape and/or surface morphology. It will be
appreciated that the laser beam directing mechanisms can include
changing the path of the laser beam, changing the location or
orientation of the work piece, or all in combination. In some
embodiments, one or more of the separated portions of material
comprise fragmented or particulate material and can further
comprise waste debris.
[0019] In an additional exemplary embodiment, the present invention
is directed to the separate portions of a brittle material created
by a process. The process includes: (a) providing a stock of
brittle material and (b) applying one or more laser beams to a
portion of the brittle material causing separation of the material
into two or more portions in a way that precisely controls the
geometric shape and/or surface morphology of the surfaces(s) of at
least one of the separated portions. In some embodiments, one or
more of the separated portions of material comprise fragmented or
particulate material and can further comprise waste debris.
[0020] More aspects of the invention are provided herein. In some
embodiments, a liquid assisted material processing apparatus
comprises a laser, a material holder, and a fluid cleaning system
providing a fluid in contact with a material on the material
holder. In some embodiments, the fluid cleaning system comprises a
reservoir. In other embodiments, the fluid comprises a salt. In
some other embodiments, the salt comprises NaCl. In some
embodiments, the salt comprises a divalent salt. In other
embodiments, the divalent salt comprises CaCl.sub.2, MgCl.sub.2, or
a combination thereof in some other embodiments, the fluid
comprises a non-neutral fluid. In some embodiments, the non-neutral
fluid comprises a pH value lower than 4. In other embodiments, the
non-neutral fluid comprises a pH value greater than 7.2. In some
other embodiments, the fluid has a zeta-potential lower than 8. In
some embodiments, the fluid facilitates the coagulation of the
particles that are generated from the material.
[0021] In another aspect, a method of processing a material
comprises placing a material on a holder, applying a laser beam to
the material, and using a fluid to remove particles generated at
the material due to the application of the laser beam. In some
embodiments, the method comprises coagulating the particles in the
fluid, such that the reattachment of the particles to the material
is avoided. In other embodiments, the method comprises reducing a
zeta potential. In some other embodiments, method comprises adding
a salt. In some other embodiments, the salt comprises CaCl.sub.2,
MgCl.sub.2, NaCl, or a combination thereof. In some embodiments,
the salt comprises a divalent salt. In some other embodiments, the
fluid comprises a non-neutral fluid. In some embodiments, the
non-neutral fluid has a pH value lower than 5. In other
embodiments, the particles comprise nanoparticles, microparticles,
or a combination thereof. In some other embodiments, the particles
comprise colloidal silica. In some embodiments, the method
comprises scanning the laser beam from a distal side of the
material toward a proximal side of the material.
[0022] In another aspect, a method of forming a through-feature on
a brittle material comprises applying a laser beam on a brittle
material, forming a beveled through-hole on the brittle material,
controlling the geometric shape and/or surface morphology of the
brittle material. In some embodiments, the laser beam comprises an
ultrafast laser pulse. In other embodiments, the laser beam
comprises a femtosecond laser pulse. In some other embodiments, the
beveled through-hole comprises a countersink structure. In some
embodiments, the beveled through-hole comprises an angled chamfer.
In other embodiments, the beveled through-hole comprises a round
corner. In some other embodiments, the brittle material comprises a
multiple layered structure. In some embodiments, the method
comprises applying a laser pulse to one layer of the multiple layer
material. In other embodiments, the brittle material comprises a
glass. In some other embodiments, the brittle material comprises a
consumer electronic protective glass.
[0023] In another aspect, a method of forming an edge chamfer, or
bevel, on a brittle material comprises applying a laser beam on a
brittle material and forming a chamfer or bevel on the brittle
material. In some embodiments, the laser beam comprises laser
pulses with pulse duration less than about 100 nanoseconds. In some
embodiments, the laser beam comprises laser pulses with pulse
duration less than 100 picoseconds. In some embodiments, the laser
beam comprises laser pulses with pulse duration less than about
1000 femtoseconds. In some embodiments, the method comprises
applying a laser pulse to one layer of the multiple layer material.
In other embodiments, the brittle material comprises a glass. In
some other embodiments, the brittle material comprises a consumer
electronic protective glass.
[0024] In another aspect, a method of forming an edge chamfer on a
brittle material comprising applying a laser beam on a brittle
material, forming an edge chamfer on the brittle material, and
controlling the geometric shape or surface morphology of the
brittle material. In some embodiments, the laser beam comprises an
ultrafast laser pulse in a picosecond to femtosecond time scale. In
other embodiments, the laser beam comprises a femtosecond laser
pulse. In some other embodiments, the chamfer comprises a flat
surface that is angled with respect to a body of the brittle
material. In some embodiments, the chamfer comprises a flat surface
that has an angle of at least 10 degrees with respect to a body of
the brittle material. In other embodiments, the edge chamfer
comprises a round corner. In some embodiments, the brittle material
comprises a multiple layered structure. In some embodiments, the
method further comprises applying a laser pulse to one layer of the
multiple layer material. In other embodiments, the brittle material
comprises a glass. In some embodiments, the brittle material
comprises sapphire. In other embodiments, the brittle material
comprises a consumer electronic protective glass.
[0025] Other features and advantages of the present invention will
become apparent after reviewing the detailed description of the
embodiments set forth below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Embodiments will now be described by way of examples, with
reference to the accompanying drawings which are meant to be
exemplary and not limiting. For all figures mentioned herein, like
numbered elements refer to like elements throughout.
[0027] FIG. 1A illustrates a typical method of cutting a stock of
brittle material using a typical tool.
[0028] FIG. 1B illustrates three rough edges made by using typical
methods of and devices for cutting a brittle material.
[0029] FIG. 2 illustrates an apparatus for applying a tool to a
brittle material substrate in accordance with some embodiments of
the present invention.
[0030] FIG. 3 illustrates a profile view of six edge geometric
shapes that are created by applying the tool to a brittle material
substrate in accordance with some embodiments of the present
invention.
[0031] FIG. 4 illustrates a cross sectional view of void patterns
on the brittle material made by the methods and devices in
accordance with some embodiments of the present invention.
[0032] FIG. 5 illustrates a top-down view of a tool path pattern
that includes stress relief lines in accordance with some
embodiments of the present invention.
[0033] FIG. 6 illustrates a top-down view of another tool path
pattern that includes stress relief lines in accordance with some
embodiments of the present invention.
[0034] FIG. 7 illustrates a top-down view of a tool path pattern in
accordance with some embodiments of the present invention.
[0035] FIG. 8A illustrates a temperature discontinuity separation
fixture in accordance with some embodiments of the present
invention.
[0036] FIG. 8B illustrates the resultant temperature pattern in a
brittle material substrate during application of the temperature
discontinuity separation fixture in accordance with some
embodiments of the present invention.
[0037] FIG. 9 illustrates a device for cutting a brittle material
in accordance with some embodiments of the present invention.
[0038] FIG. 10 illustrates a method of shaping a brittle material
into a brittle material portion with an encapsulated
through-feature resembling a rectangular profile with rounded
corners.
[0039] FIG. 11 illustrates a shaping method in accordance with some
embodiments of the present invention.
[0040] FIG. 12 illustrates an apparatus for shaping a material in
accordance with some embodiments of the present invention.
[0041] FIG. 13 illustrates a material shaping method using the
apparatus in accordance with some embodiments of the present
invention.
[0042] FIG. 13A is a flow chart illustrating a encapsulated
through-feature forming method in accordance with some embodiments
of the present invention.
[0043] FIGS. 14A-14C illustrate a material shaping method 1400 with
predetermined paths and patterns.
[0044] FIG. 15 illustrates encapsulated through-holes shaping
method, which can us used to shape a layered brittle material.
[0045] FIG. 16 illustrates a system for shaping brittle
materials.
[0046] FIG. 17 is a flow chart illustrating shaping a brittle
material method using a laser beam in accordance with some
embodiments of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0047] Reference is made in detail to the embodiments of the
present invention, examples of which are illustrated in the
accompanying drawings. While the invention is described in
conjunction with the embodiments below, it is understood that they
are not intended to limit the invention to these embodiments and
examples. On the contrary, the invention is intended to cover
alternatives, modifications and equivalents, which can be included
within the spirit and scope of the invention as defined by the
appended claims. Furthermore, in the following detailed description
of the present invention, numerous specific details are set forth
in order to more fully illustrate the present invention. However,
it is apparent to one of ordinary skill in the prior art having the
benefit of this disclosure that the present invention can be
practiced without these specific details. In other instances,
well-known methods and procedures, components and processes have
not been described in detail so as not to unnecessarily obscure
aspects of the present invention. It is, of course, appreciated
that in the development of any such actual implementation, numerous
implementation-specific decisions must be made in order to achieve
the developer's specific goals, such as compliance with application
and business related constraints, and that these specific goals can
vary from one implementation to another and from one developer to
another. Moreover, it is appreciated that such a development effort
can be complex and time-consuming, but is nevertheless a routine
undertaking of engineering for those of ordinary skill in the art
having the benefit of this disclosure.
[0048] In the following, methods of and devices for shaping brittle
materials with a controlled surface and bulk properties are
disclosed in accordance with some embodiments of the present
invention. The present invention is able to shape brittle
materials, such as glass, sapphire or silicon, into precise shapes
while controlling the as-shaped surface properties, such as
roughness, micro-cracking, taper or bevel, which impact structural
and cosmetic characteristics of brittle materials, such as the
bending strength and tactile user experience of an electronic
display panel.
[0049] One of the uses of the present invention is shaping brittle
materials with controlled surface quality and within a relatively
brief period of time when compared to typical available shaping
techniques.
[0050] In some embodiments, the present invention enables shaping
of brittle materials into predetermined profiles while maintaining
a high level of control over the shaped surface properties. Hence,
the subsequent conditioning processes are able to be reduced or
eliminated from the overall fabrication protocol. The present
invention can be utilized to create singulated products with
greatly varying options for geometrical configurations.
Additionally, the systems and methods disclosed herein can be
utilized to fabricate features into products with fine precision.
Examples of features include slits, apertures, holes, grooves,
notches, etching, and so forth.
[0051] In some embodiments of the present invention, the methods
are able to substantially reduce the Takt time by reducing or
eliminating some or all of the additional steps for making the
required profile and/or surface morphology.
[0052] In some embodiments of the present invention, the methods
and devices are able to prevent uncontrolled crack propagation by
pre-defining the crack propagation pathway by modification of the
intrinsic brittle material stresses or defects, or by insertion of
artificial stresses or defects, which guide the crack propagation.
The modification mechanisms can include some or all of changes to
the local lattice structure in order to create localized stress
planes, discontinuous density of the material, and/or a variation
of the energy absorption properties.
[0053] In some embodiments of the present invention, the methods
and devices are able to prevent uncontrolled crack propagation by
applying the shaping tool in a pattern that compensates for the
intrinsic granular pathways. The pattern can include localized
adjustment of energy delivered from the tool to the brittle
material, localized translation of the tool to compensate intrinsic
granularity of the brittle material, and/or selective placement of
energy from the tool to the brittle material, such as with pulsing
a beam of directed energy.
[0054] In some embodiments of the present invention, the methods
and devices are able to produce as-shaped surface geometric shape
and/or surface morphology that satisfy the shape and morphology
requirements of a finished product or finished component of a
finished product.
[0055] In some embodiments, the present invention is applied to
shape thin panels of brittle material (e.g., glass or sapphire) for
utilization in electronic displays.
[0056] In some embodiments, the present invention is used to
fabricate a portion of the brittle material having functional
surface properties, such as for controlling the optical properties
of the surface, the tactile properties of the surface and/or the
chemical reactivity of the surface. Creating the functional
properties for the as-shaped brittle material surface comprises
imparting a periodic structure with periodicity on the scale of
nanometers, micrometers, or larger. The periodic structure can be a
superposition of multiple substructures, such as combining
nanometer scale structures on top of micrometer scale
structures.
[0057] In some embodiments, the methods of the present invention
forms the functional surface properties of a brittle material,
which enhance the cosmetic appearance and enhance the structural
integrity of the resultant brittle material portion, especially
when the brittle material portion is combined with other materials
into a finished product, such as a handheld consumer electronic
device.
[0058] In some embodiments, the present invention
changes/manipulates/controls the optical properties of the
as-shaped surface. The optical properties include reflecting,
transmitting, diffracting, and/or scattering properties of light by
the surface. By changing these optical properties, the methods of
the present invention can impart a substantially different visual
performance of the as-shaped surface. The visual performance of the
as-shaped surface can be modified to be brighter or darker, shiny
or dull, and/or having a color (hue) change, as compared to the
native brittle material surface. The controlled optical properties
of the as-shaped surface exhibit different optical response
depending on the viewing angle of the surface.
[0059] In some embodiments, the present invention controls the
tactile properties of the as-shaped surface, including manipulating
the coefficients of friction of the surface and/or adding a contour
to the surface. By changing these tactile properties, the present
invention can impart a surface quality that feels smooth to the
human touch, thereby making the as-shaped portion of the brittle
material more pleasing to hold in the user's hand and/or carry
close to the body, such as in an arm-band mounted holster. The
enhanced tactile properties of the as-shaped brittle material
portion can be discernable for the portion in mechanical isolation
and/or once the portion is assembled with other materials into
finished product, such as a handheld consumer electronic device. By
changing the tactile properties of the as-cut brittle material
surface, the present invention can impart a surface quality that
makes the resultant device easier to grip.
[0060] The brittle material disclosed herein can include one or
more of the following types of materials: glass, sapphire, single
crystal or monocrystalline, polycrystalline, ceramic, tungstate,
oxide, alloy, hybrid metal/non-metal composite, or a combination of
any of these. Further, the brittle material disclosed herein can
include a doped, tinted, or color-modified version of the above
materials. Furthermore, the brittle material disclosed herein can
include a tempered or strengthened glass with an engineered stress
profile. The brittle material can comprise Gorilla.RTM. or Eagle
glass (e.g., Eagle XG.RTM.) from Corning.RTM., Dragontrail.RTM.
from Asahi Glass Co. Ltd, Lotus, Wilos, or IOX-FS, or Xensation.
The brittle material can also include one of these types of glass
that is shaped with the method of the present invention prior to
the tempering or strengthening process step. The tempering or
strengthening process step can comprise heating the glass or
subjecting the glass to an ion exchange treatment. The brittle
material can be one of these types of glass that is shaped with one
of the methods of the present invention subsequent to the tempering
or strengthening process step.
[0061] The brittle material described in the present specification
can comprise a layered material. The one or more layers of such
brittle material can exhibit different mechanical or chemical
properties that distinguish the layered regions from one to
another. In some embodiments, the different mechanical or chemical
properties of the layered regions can be created or enabled by a
brittle material strengthening process. For example, the layered
brittle material can comprise a glass that has undergone an ion
exchange treatment. The ion exchange process imparts layers of
different compressive stress or tensile stress.
[0062] In some embodiments, the brittle material described herein
comprises a layered material created by stacking two or more
brittle materials, or by stacking a brittle material with one or
more brittle, plastic (polymer) or metallic materials. This type of
brittle material is used in electronic display subassemblies, where
the layers can serve different functions in display operation. For
example, the brittle material can comprise a material stack that
includes one or more of an active layer, a filter layer, and a
cover layer. One or more of these layers can be transparent to
visible light.
[0063] Moreover, the present invention is able to cut brittle
materials that have inclusions, stress planes, discontinuities, or
other intrinsic properties that are unable to be shaped by a
typical methods and devices (e.g., diamond saw). The present
invention has many advantageous features over typical shaping
processes. The surface of the brittle material that is shaped using
the present invention has smoother as-shaped surface compared with
the surface that is shaped using typical methods, which can be
quantified and measured by measuring the size of surface
micro-cracks, spallation, and/or chips. The brittle material that
is shaped using the embodiments of the present invention has
stronger bending strength when compared with the brittle material
that is shaped using a typical method.
[0064] In some embodiments, the present invention is used to
fabricate portions of brittle materials to be integrated into
consumer electronic devices, such as smart phones, tablet
computers, personal digital assistants, laptop or notebook
computers, touch-screens, desktop computer monitors, television
sets, portable music players, computer mouse, touch-sensitive
motion controllers, and protective covers for any of these
electronic devices. In some embodiments, the portions of brittle
materials to be integrated into consumer electronic devices include
display screens, touch screens, multi-touch screens, display back
planes, display illumination layers, light emitting diode (LED)
substrates, organic light emitting diode (OLED) substrates, and/or
transparent conducting layers. The layers can comprise either an
active or passive matrix format.
[0065] In some embodiments, the present invention is used to
fabricate portions of brittle materials into cut-outs, substrates
from which additional portions will be shaped, cut-outs with
feature portions removed from within the cut-out perimeter, and/or
cut-outs having multiple macroscopic functions enabled within the
brittle material common plane. In some embodiments, the additional
shaping of the portions comprises creating an edge chamfer to
improve the functional performance of the brittle material
component. The feature portions and enabled functions can comprise
visual displays, acoustic transfer channels, photographic recording
portals, sound recording portals, mechanical buttons, mechanical
switches, ambient light sensors, photographic flash emitters,
antennas, electronic connectors, fiber optic connectors, touch
screen buttons, touch screen switches, mechanical clips, corporate
logo markings, cosmetic designs, fluid transfer channels, radio
frequency wave or microwave transmission channels, and/or thermal
transducers.
[0066] In some embodiments, the present invention is used to shape
brittle materials with a thickness (the dimension is defined by a
plane substantially parallel to the direction of tool path or
pattern) <500 micrometers while controlling the as-shaped edge
properties. Shaping thin sheets of brittle materials into separate
portions is generally very difficult since typical methods impose
collateral damage in the form of large cracks, spallation, chips or
internal faults. In some embodiments, the present invention is used
to shape brittle materials with thickness <300 micrometers while
controlling the as-shaped surface properties.
[0067] In some embodiments, the system of present invention
includes a shaping tool, tool delivery components, shaping method
software, computer-readable instructions, or templates
stored/retained in the machine memory, brittle material handling
devices, electronics to control system functionality and/or monitor
system performance, software to control system functionality,
monitor system performance and/or provide telemetry of system
operations, and/or system performance validation metrology.
[0068] In sonic embodiments, the system of present invention
includes the tool(s) that enable separating a portion of a brittle
material from a first larger portion of the material, removing
smaller sections of brittle material from within the perimeter of
the smaller portion, and modifying the edges to create chamfer,
beveling, rounding or squaring of the as-shaped edge.
[0069] In some embodiments, the as-shaped surface quality of the
brittle material using the methods and devices of the present
invention has the following features: (1) the size of the
micro-cracks on the as-shaped edge is smaller than about 15
micrometers or penetrates less than about 15 micrometers into the
bulk of the material; (2) the sizes of the chips, spall or burrs on
the as-shaped surface are smaller than 20 micrometers or penetrate
less than about 20 micrometers into the bulk of the material; (3)
the surface of the as-shaped surface is smooth to the touch of a
human finger; (4) the as-shaped surface has as shaped surface edge
root-mean-square (RMS) roughness less than about 15 micrometers;
(5) the as-shaped surface has roughness designed to minimize light
loss due to scattering; (6) the as-shaped surface has shapes of
beveled, or chamfered, sidewalls; (7) the as-shaped surface has
tapered sidewalls; (8) the as-shaped surface enables the as-shaped
portion to sustain bend strength of greater than about 60
megapascal (MPa) after shaping, as measured using a three-point, or
four-point, flexural strength test; (9) the brittle material with
the as-shaped surface enables the shaped portion to sustain bend
strength of greater than about 400 MPa after shaping and
post-shaping strengthening, as measured by a three-point, or
four-point, flexural strength test; and (10) the brittle material
with the as-shaped surface exhibits a polarized light-measured
stress field less than about 50 micrometers deep into the material.
The properties are listed as exemplary features. A person of
ordinary skill in the art appreciates that other features are
within the scope of the present invention.
[0070] The system of the present invention can implement a shaping
pattern with an arbitrary tool path, e.g. with curves,
straight-lines, sharp corners, oblique corners or independent
arbitrary cut-out features. The shaping pattern can be continuous
or discontinuous when tracing the arbitrary tool path. The shaping
pattern can traverse a tool path inside or outside the perimeter of
a previous tool path. The shaping pattern(s) can be programmable
via software or external machined commands. The tool path and/or
pattern can be enabled by a coordinated combination of scanning the
tool and translating the brittle material substrate.
[0071] In some embodiments, the present invention uses a tool
comprising selectively variable output from a femtosecond laser
source as part of the shaping process. In some embodiments, the
present invention uses a tool comprising burst mode output from a
femtosecond laser, where the individual femtosecond laser pulses
are grouped into short bursts lasting 10 to 1000 nanoseconds and
the time interval between individual pulses is about 1 to 100
nanoseconds. In some embodiments, the present invention uses shaped
bursts of femtosecond laser pulses in a burst mode format, where
the amplitude of each individual pulse within the overall burst has
a unique value. In some embodiments, the present invention uses
temporally shaped pulses on the femtosecond to picosecond time
scale. In some embodiments, the present invention uses tools
comprising a dual light source (e.g., a femtosecond laser and a
longer pulse or a continuous wave (CW laser)). In some embodiments,
the present invention uses tools comprising a femtosecond laser and
an acoustic transducer.
[0072] In some embodiments, the method of the present invention
comprises providing a stock of brittle material to be shaped,
directing a first source of energy to the brittle material along a
programmed tool path in order to impart a microscopic defect zone,
and directing a second source of energy to the brittle material,
following a substantially identical tool path as the first source
of energy, or at least a portion of that path, in order to cause a
controlled separation of the original (portion of brittle material
into two new portions of brittle material, where the as-shaped
surface quality of the one or more new portions has predetermined
and highly controllable geometric shape and/or surface
morphology.
[0073] In the following description, devices for and methods of
shaping brittle materials with controlled surface and bulk
properties are disclosed in further detail in accordance with some
embodiments of the present invention.
[0074] FIG. 2 illustrates an apparatus 200 for applying a tool 202
to a brittle material substrate 201 in accordance with some
embodiments of the present invention. The tool is generated by a
source 204 and directed to the substrate 201 by a delivery module
206. The substrate is positioned by a fixture 208.
[0075] FIG. 3 illustrates a profile view of edge geometric shapes
that are formed by applying the tool 202 to a brittle material
substrate 201 in accordance with some embodiments of the present
invention. The shape 302 is an arbitrary curved contour with
inflection points. The shape 304 is a uniform taper with an
exemplary precise taper angle. The shape 306 is a zero-taper edge.
The zero-taper edge is perpendicular to the brittle material 201
top and/or bottom edges. A person of ordinary skill in the art
appreciates that any other shapes are able to be formed using the
methods and devices of the present invention, such as rounded curve
and triangle with a sharp edge. More shapes are able to be made
using the methods and device disclosed herein. For example, the
shape 308 is a chamfered edge with a precise chamfer angle and
depth. The shape 310 is a round convex chamfered edge with precise
radius of curvature. The shape 312 is a round concave chamfered
edge with precise radius of curvature.
[0076] FIG. 4 illustrates a cross sectional side view of void
patterns on the brittle material made by the methods and devices in
accordance with some embodiments of the present invention. In some
embodiments, a first source of energy, such as a femtosecond pulse
laser beam, ablates a series of void patterns 401, 403, and 405. In
the first brittle material 402, the void pattern has the defect
zones 401 with individual voids 402A, 402B, 402C, and 402D that are
stacked vertically with stair-step lateral offset from one void to
the next. In some embodiments, a first femtosecond pulse laser beam
ablates the brittle material near the bottom side of the brittle
material and making a void 402A. Next, a second femtosecond pulse
laser beam ablates the brittle material and makes a void 402B. A
third and fourth femtosecond pulse laser beams ablate the brittle
material and makes voids 402C and 402D. The voids 402A to 402D are
able to be created in any orders. For example, a first femtosecond
pulse laser beam creates void 402D. A second femtosecond pulse
laser beam creates void 402C. A third femtosecond pulse laser beam
creates void 402B. Similarly in some other embodiments, a first
femtosecond pulse laser beam creates the void 402B and a second
femtosecond pulse laser beam creates the void 402D.
[0077] In the second brittle material 404, the void pattern has the
defect zones 403, which has individual voids 404A-404D that are
stacked vertically with no lateral offset from one void to the
next. In the third brittle material 406, the void pattern contains
the defect zones 405, which has individual voids 406A-406D that are
stacked diagonally with no lateral offset from one void to the next
with respect to the oblique diagonal. In some embodiments, some
portions of the voids are overlapping from one void to the next. A
person of ordinary skill in the art appreciates that the voids are
able to be created in any angles, any sequences, any shapes and any
patterns.
[0078] Examplary methods of and devices for shaping brittle
materials are disclosed in accordance with some embodiments of the
present invention.
[0079] In some embodiments, a method of shaping a brittle material
comprises providing a stock of brittle material to be shaped,
directing a first laser beam to the brittle material along a
programmed tool path in order to impart a microscopic defect zone,
directing a second laser beam to the brittle material following a
substantially identical or identical tool path of the first laser
beam, and causing a controlled separation of the original portion
of brittle material into two new portions of brittle material. In
some embodiments, the second laser beam generates void pattern
overlapping at least a portion of the void pattern generated by the
first last beam. Using the method of the present invention, the
as-shaped surface quality of the one or more new portions has
predetermined geometric shape and/or surface morphology.
[0080] In some embodiments, a method of shaping a brittle material
comprises providing a stock of brittle material to be shaped,
directing a first femtosecond pulse laser beam to the brittle
material along a programmed tool path in order to impart a
microscopic defect zone, directing a second long pulse or CW laser
beam (a continuous wave laser beam) to the brittle material
following a substantially identical tool path as the first laser
beam or at least a portion of that path, and causing a controlled
separation of the brittle material into two new portions of brittle
material. The as-shaped surface quality of the one or more new
portions has predetermined controllable geometric shape and/or
surface morphology.
[0081] The tool path followed by the first laser beam in this
exemplary embodiment includes a pattern that traces the outline of
the desired as-shaped device along with well-defined stress relief
pathways, or lines. The stress relief lines are positioned using
the first laser beam at predetermined locations adjacent to the
device outline portion of the pattern to facilitate the propagation
of a separation line along the device outline. These stress relief
lines are particularly useful when propagating a separation line
around a small radius feature, such as the corner of a display
panel, where the intrinsic stress of the brittle material substrate
tends to create uncontrolled pathways for material separation.
[0082] FIG. 5 illustrates a top-down view of a tool path pattern
502 that includes stress relief lines 504 in accordance with some
embodiments of the present invention. The brittle material 501 is
first exposed to the first laser beam that first follows the device
outline tool path 502, then follows the stress relief tool path
504. In some embodiments, the tool path 502 is a continuous line
506. In alternative embodiments, the tool path 502 constitutes
spatially cut points/voids 508 remote from each other.
[0083] In some embodiments after the first laser beam has traced
out the full pattern to define the preferred stress fracture
pathways 504, the brittle material 501 is then exposed to the
second laser beam that follows the device outline tool path 502.
Under exposure to the second laser beam, the brittle material 501
separates into at least five new portions comprising the new
brittle material device portion 503 along with four sacrificial
portions 510, 512, 514, and 516. The as-shaped surface quality of
the device portion 503 has predetermined and highly controllable
geometric shape and/or surface morphology.
[0084] FIG. 6 illustrates a top-down view of another tool path
pattern 602 that includes stress relief lines 604 in accordance
with some embodiments of the present invention. A first laser beam,
such as a femtosecond pulse laser beam, is applied on a brittle
material 601 following a device outline tool path pattern 602 in a
direction indicated by the arrow 606. Next, the first laser beam is
applied to the stress relief lines 604. The arrows 606 show the
directionality of the first laser beam tool path. Next, a second
laser beam, such as a second long pulse (e.g., a picosecond laser
beam) or CW laser beam, is applied on the brittle material 601
following only the device outline of the tool path 602. After the
application of the second laser beam, the brittle material 601
separates into multiple new portions comprising the new brittle
material device portion 603 along with multiple sacrificial
portions 607-617, where the as-shaped edge quality of the device
portion 603 has predetermined and highly controllable geometric
shape and/or surface morphology.
[0085] In some embodiments, the method includes removing a portion
of the brittle material from within/surrounded by a larger portion
of the brittle material. The tool path followed by the first laser
beam comprises a pattern that traces the outline of the interior
portion to be removed from a larger portion of brittle material
along with well-defined stress relief pathways or lines. The stress
relief lines are positioned using the first laser beam at a
predetermined locations adjacent to, and/or interior to, the
outline portion of the pattern to facilitate the propagation of a
separation line along the outline. These stress relief lines are
useful when propagating a separation line inside a small radius
feature, such as the interior corner of a display panel feature,
where the intrinsic stress of the brittle material substrate tends
to create uncontrolled pathways for material separation.
[0086] FIG. 7 illustrates a top-down view of a tool path pattern in
accordance with some embodiments of the present invention. The tool
path pattern includes stress relief lines 704 and 704A interior to
the outline portion 702 of the pattern. The brittle material 701 is
first exposed to the first laser beam that first follows the
outline tool path 702, then follows the stress relief tool path 704
and 704A. These tool paths can be continuous, or they can be
spatially remote from each other. After the first laser beam traced
out the full pattern to define the predetermined stress fracture
pathways, the brittle material 701 is then exposed to the second
laser beam that preferably follows only the device outline tool
path 702. After the application of the second laser beam, the
brittle material 701 is separated into multiple new portions
comprising the new brittle material device portion 703 along with
sacrificial portions 705-711 (including 704A), where the as-shaped
edge quality of the device portion 703 has predetermined and highly
controllable geometric shape and/or surface morphology.
[0087] In sonic embodiments, applying the first laser beam to the
outline tool path 702 and the stress relief tool path 704 is
preceded by creation of a "pilot hole" 704A inside the interior of
the outline 702 and stress relief lines 704, to facilitate a
cleaner separation of the sacrificial portions of brittle material
from the larger portion of brittle material. A person of ordinary
skill in the art appreciates that the patterns 703, 704A, 705-712
can be formed in any order.
[0088] In some embodiments, the first and/or second laser beams are
focused to a predetermined plane within the brittle material
substrate or on the surface of the brittle material in order to
selectively expose that plane of the brittle material. The
selective exposure can be achieved by using a
high-numerical-aperture (high-NA) lens to form a rapidly converging
beam. In some embodiments, the numerical aperture (NA) of the lens
is greater than 0.1. In other embodiments, the numerical aperture
(NA) of the lens is greater than 0.3. In some other embodiments,
the numerical aperture (NA) of the lens may be greater than 0.5. In
some embodiments, the numerical aperture (NA) of the lens may be
greater than 0.7.
[0089] In some embodiments, the first and/or second laser beams are
shaped by one or more beam shaping optical elements to provide a
predetermined laser beam wave front at a specific plane of exposure
within the brittle material substrate, or on the surface of the
brittle material. For example, the first laser beam wave front can
be optimized to provide an extended profile stress defect inside
the brittle material. This can be achieved by adding a transparent
plate between the high-NA lens and the brittle material substrate
to deliberately impose spherical aberration into the laser beam
path. This form of beam shaping enables a longer effective depth of
focus, thereby creating a stress defect with an extended
longitudinal dimension.
[0090] In some embodiments, the tool path followed by the first
laser beam is repeated two or more times, with a change in focal
plane for each iteration of the tool path. The change in focal
plane with each iteration can be utilized to form a stacked array
of voids, such as those shown in FIG. 4 as mentioned above. Each
void layer in the vertical stack is formed within one focal plane.
Each focal plane can contain a large number of individual voids
placed side-by-side to follow the pattern defined as the brittle
material portion outline 702, stress relief lines 704, or pilot
hole 704 of FIG. 7. In some embodiments, each focal plane iteration
of the tool path is able to be laterally shifted, by a microscopic
amount, such that a stair-case defect zone 401 of FIG. 4 is able to
be formed. In other embodiments, each focal plane iteration of the
tool path is able to have zero lateral shift, such that an inline
vertical defect zone 403 of FIG. 4 is able to be formed. In some
other embodiments, each focal plane iteration of the tool path can
be offset, but following along a diagonal plane, such that a tilted
inline defect zone 405 of FIG. 4 is able to be formed.
[0091] In some embodiments, the change in focal plane is provided
by an active spatial beam phase filter for the laser beam. The
phase filter comprises a two-dimensional (2D) liquid crystal
spatial light modulator or a 2D deformable mirror assembly. The
phase filter is programmable via computer control in order to
adjust the focal plane with minimal delay between iterations of
traversing the repeated tool path in the brittle material.
[0092] The active spatial beam phase filter is able to be
programmed to impart a spatial phase to the laser beam that is not
purely quadratic. Instead, the phase filter is able to be
programmed to mimic the high-NA-lens-plus-transparent-plate wave
front optimization scheme, or an alternative wave front
optimization scheme that extends the longitudinal dimension of the
resultant stress defect. The optimization scheme can be adaptive to
self-correct the imposed spatial filter function based on the
feedbacks from a laser material process monitoring sensor.
[0093] In some embodiments, the methods include removing a portion
of the as-shaped brittle material within a larger portion of the
as-shaped brittle material. This method comprises adjusting the
temperatures of the as-shaped portions of brittle material in order
to create a temperature discontinuity between the two portions. In
some embodiments, an inner portion of brittle material is cooled,
or chilled, to induce thermal material contraction, while the outer
material is held at constant temperature, or even heated. The
material contraction of the inner portion of brittle material can
result in clean separation of the inner and outer portions, so that
the separation can occur with minimal resistance from friction, or
other surface forces, between the two portions.
[0094] FIG. 8A illustrates a temperature discontinuity separation
fixture 800 in accordance with some embodiments of the present
invention. The outer portion of the as-shaped brittle material 801
is heated, or held at ambient temperature, by heaters 802 held
against the brittle material 801 with clamps 804. The inner portion
810 of brittle material 801, which is inside the portion-dividing
pattern 806, is rapidly cooled by a cooling tool 808, such as a
copper post that is chilled by liquid nitrogen. The rapid cooling
of the inner portion 810 causes a mechanical contraction of the
inner brittle material portion 810, whereby the inner brittle
material portion 810 separates cleanly from the outer portion 812
of brittle material with minimal resistance from friction, or other
surface forces, between the two portions.
[0095] FIG. 8B illustrates the resultant temperature pattern in a
brittle material substrate 811 during application of the
temperature discontinuity separation fixture 800 of FIG. 8A in
accordance with some embodiments of the present invention. The
outer portion of the temperature pattern 814 is held at ambient
temperature. In some other embodiments, the temperature pattern 814
is heated above an ambient temperature. The inner portion of the
temperature pattern 816 is cooled substantially below the
temperature of the outer portion in order to induce separation of
the two portions by way of mechanical/physical contraction of the
inner portion 816.
[0096] In some embodiments, the temperature discontinuity
separation step can be executed after the brittle material
substrate 811 is exposed to a single laser beam that creates stress
defects within the brittle material. The stress defects created by
the laser beam provide a pathway for releasing the stress imposed
by the temperature discontinuity. This arrangement enables the
simultaneous division of a brittle material substrate into two or
more portions of brittle material and the separation of the
portions while avoiding resistance from friction, or other surface
forces, between the resultant portions.
[0097] In some embodiments, the temperature discontinuity
separation step is executed after the brittle material substrate is
exposed to a first femtosecond laser beam that creates stress
defects within the brittle material and a second continuous wave,
or longer pulse, laser beam that divides the original brittle
material substrate 811 into two or more new portions of brittle
material. In some embodiments, the division into two or more
distinct new portions of brittle material, due to the second laser
exposure, does not include the separation of the portions from each
other, because of the strong friction, or other surface forces,
among the new portions. In these embodiments, the temperature
discontinuity separation step is able to be executed after exposure
of the brittle material substrate to the second laser beam in order
to separate the new portions of brittle material from each
other.
[0098] In some embodiments, the method comprises providing a stock
of a brittle material to be shaped, directing a first source of
energy tool to the brittle material along a programmed tool to
impart a microscopic detect zone, directing a second source of
energy tool to the brittle material, following a partially
identical tool path as the first source of energy tool to cause a
controlled separation of the original portion of brittle material
into multiple new portions of brittle material, and directing a
third source of energy tool to at least one edge of one of the
separated portions to further modify the edge geometry and/or
surface morphology, where the as-shaped surface quality of the one
or more new portions has predetermined and controllable geometric
shape and/or surface morphology.
[0099] In some embodiments, the third source of energy tool is used
to form a chamfer along the perimeter(s) of one of the new portions
of brittle material. The perimeter of the brittle material
comprises either, or both, an interior or exterior perimeter of the
shaped pattern. The chamfer geometry imparted to the perimeter(s)
of the brittle material portion can further improve the functional
characteristics of the new portion of brittle material, such as the
bending strength of the brittle material portion as evaluated using
a multi-point flexural strength test. The chamfer or bevel profile
can be angular or smoothly rounded.
[0100] In some embodiments, the first, second and/or third source
of energy tools comprise femtosecond pulse laser beams. In some
embodiments, the first, second and/or third source of energy tools
comprise picosecond pulse laser beams. In some embodiments, the
first, second and/or third source of energy tools comprise
nanosecond pulse laser beams. In some embodiments, the first,
second and/or third source of energy tools comprise continuous wave
(CW) laser beams, such as from a carbon dioxide (CO.sub.2) laser
source.
[0101] In some embodiments, the third source of energy tool
application to the brittle material is preceded by bonding a
sacrificial substrate to a portion of the perimeter(s) edge in
order to enhance the localized mechanical stress of a portion of
the perimeter(s) edge.
[0102] In some embodiments, the third source of energy tool
application to the brittle material is followed by a thermal shock
step to create the desired/predetermined perimeter edge profile,
such as the chamfer profile. The thermal shock step can comprise
placement of the brittle material, or a perimeter section of the
brittle material, in a bath of hot fluid. The hot fluid bath can
impart functional features to the brittle material portion, such as
an increased bending strength, as a result of an ion-exchange
process between the brittle material and the fluid.
[0103] In some embodiments, the third source of energy tool is used
to create a temporary, thin melt zone along the perimeter(s) of one
of the new portions of brittle material. The perimeter of the
brittle material comprises either, or both, an interior or exterior
perimeter of the shaped pattern. The thin melt zone is temporary
and is followed immediately by a re-solidification. The sequence of
melt-and-solidify results in a self-healing effect in the brittle
material whereby micro-cracks and/or other defects are filled-in or
otherwise erased from the perimeter of the material. The
self-healing effect imparted to the perimeter(s) of the brittle
material portion improves the functional characteristics of the new
portion of brittle material, such as the bending strength of the
brittle material portion, which is verified by using a multi-point
flexural strength test.
[0104] In some embodiments, the thin melt zone creation step is
induced by a heat source, such as a torch, a laser, a specifically
shaped resistive heating element, or a pair of arc electrodes. The
heat source is utilized to heat a thin layer of the perimeter of
the brittle material to right above the melt temperature of the
brittle material, such as 0.1.degree. C. The application of the
heat source is precisely controlled so as to only melt a very thin
region nearest the edge of the brittle material. This heat
treatment can induce a reflow of molten brittle material to fill-in
any discrete defects in the edge profile to create a substantially
smoother profile. The macroscopic properties of a brittle material,
such as flexural bending strength, can be related to the brittle
material edge quality, in terms of geometry and/or surface
roughness. Hence, the reflow of the brittle material produced by
the application of a heat source can substantially improve the
macroscopic performance of the brittle material portion.
[0105] In some embodiments, the temperature of the brittle material
is entirely raised to a temperature near the softening temperature,
or to the melting temperature, intrinsic to the brittle material
before, during, and/or after the application of a heat source for
improving the edge profile. By elevating the temperature of the
entire brittle material near the softening temperature and then
applying the heat treatment to the edge of the brittle material
portion, the process avoids thermal shock around the perimeter of
the brittle material, which can cause deleterious side effects.
[0106] In some embodiments, a heat source is applied to the
perimeter of the as-shaped brittle material in order to remove a
thin strip of the brittle material, thereby removing a sharp edge
and creating a chamfer-like geometry. This effect can be manifested
as an evaporation of the brittle material comprising the sharp
edge, or as a pealing of the thin strip of brittle material away
from the brittle portion, by way of localized thermal stress, that
is intended to be transferred onto further usage. Removal of the
sharp edge in this embodiment has the macroscopic effect of
improving the performance of the brittle material portion in terms
of transmitting light, creating optical images, and mechanically
strengthening the brittle material portion. The device that
integrates the brittle material portion with the treatments
described above can improve the cosmetic nature of the brittle
material.
[0107] In some embodiments, the thin strip removal step is induced
by a heat source, such as a torch, a laser, a specifically shaped
resistive heating element, or a pair of arc electrodes. The heat
source is utilized to remove a thin layer of the perimeter of the
brittle material to be just above the melt temperature of the
brittle material, such as 0.1.degree. C. The application of the
heat source is precisely controlled so as to only strip away a very
thin region nearest the edge of the brittle material. The
macroscopic properties of a brittle material, such as flexural
bending strength, are directly related to the brittle material edge
quality, in terms of geometry and/or surface roughness. Hence, the
removal of a thin strip from the brittle material produced by the
application of a heat source can substantially improve the
macroscopic performance of the brittle material portion.
[0108] FIG. 9 illustrates a device for shaping a brittle material
in accordance with some embodiments of the present invention. The
device includes an integrated work cell 901 that coordinates the
operation of the laser beam tools 902 and 904, delivery of the
laser beam tools to the brittle material work piece, feed of
brittle material stock, positioning precisely the brittle material,
synchronized movements of the brittle material with application of
the laser beam tool(s), and auxiliary functions, such as quality
inspection or work area cleanliness. The integrated work cell 901
can include the functions described above within a rigid platform
906 for process stability and consistency of the predetermined and
highly controllable geometric shape and/or surface morphology of
the as-shaped brittle material portion.
[0109] The work cell 901 described herein can be controlled by a
computer numerical control (CNC) apparatus to coordinate various
functions performed by work cell 901. The control system can
include a central processing unit (CPU), a software operating
system (OS), and a mixture of digital and analog electronics to
send and receive commands and communications with the work cell
hardware. The control system can be operated substantially
autonomously to take in the brittle material stock and produce
brittle material portion(s) where the as-shaped surface has a
predetermined and controllable geometric shape and/or surface
morphology.
[0110] In some embodiments, the work cell control system is coupled
to a communications network. In other embodiments, the work cell
control system contains an internet web server. In some other
embodiments, the work cell control system includes methods of
remote telemetry of the constituent functional elements and/or the
brittle material processing efficacy.
[0111] The present invention can be used to fabricate encapsulated
through-features with an arbitrary profile in a brittle
material.
[0112] FIG. 10 illustrates a method 1000 in accordance with some
embodiments of the present invention. The method 1000 can shape a
brittle material 1002 with an encapsulated through-feature 1004,
which has a rectangular profile with rounded corners. In some
embodiments, the material 1008 is removed from the substrate 1002
to form the encapsulated through-feature 1004 and residual
substrate 1006 by machining the perimeter of the feature profile
and removing the inner material portion 1008. In this manner, the
machining method is relatively fast in comparison to a process
where all of the materials within the feature profile are
machined/processed. In some embodiments, the substrate 1002
comprises a material that is transparent to the femtosecond
wavelength.
[0113] FIG. 1 l illustrates a shaping method 1100 in accordance
with some embodiments of the present invention. The method 1100 can
be used to shape a brittle material 1102 to an encapsulated
through-feature 1106 having an angular chamfer/bevel 1110. In some
embodiments, the shaping process separates the brittle material
1102 into the retained portion 1104, a large waste portion 1112,
and multiple small debris portions 1114. A person of ordinary skill
appreciates that any shapes are able to be formed using the methods
and devices disclosed herein.
[0114] FIG. 12 illustrates an apparatus 1200 for shaping a material
in accordance with some embodiments of the present invention. The
apparatus 1200 (a work cell) comprises a mounting chuck 1206 fixing
and positing the brittle material 1202 to the apparatus. The chuck
comprises a reservoir 1204 to accept the waste portion 1208 of the
brittle material 1202. The reservoir can contain a gas or liquid
for assisting the shaping process.
[0115] FIG. 13 illustrates a material shaping method 1300 using the
apparatus 1200 in accordance with some embodiments of the present
invention. In some embodiments, the brittle material 1302 is shaped
with a tool path that initially shapes the material on its backside
1306 and progressively shapes the material stepwise toward its
front side 1304. The brittle material 1302 is mounted onto a chuck
1316 with a reservoir 1314 filled with a liquid solution. A laser
beam 1308 (such as generated by the tool 200 in FIG. 2 or any other
laser device) is first directed to the backside 1306 of the brittle
material and produces laser machining via ablation 1310. The
liquid/fluid 1318 in the reservoir 1314 assists in the removal of
debris 1312 from the brittle material 1302. The laser beam 1308 is
then translated upward toward the front side 1304 in a stepwise
pattern. The liquid 1318 in the reservoir can be pulled into the
machined kerf/incision via capillary action/force. The presence of
the liquid 1318 inside the kerf can further assist the removal of
the debris 1312.
[0116] In some embodiments, the liquid 1318 comprises a non-neutral
fluid, which prevents the redeposition of the nanoparticle in the
ablative brittle material machining. During the process of
ablatively machining brittle materials (e.g., glass) with a laser,
the ablated debris settles on the surface of the
material/substrate. These debris are small enough to be very
reactive, resulting in strong, severe debris reattachment. The
ablative laser machining normally occurs near the end of the
manufacturing process, after the surface has been polished, an
abrasive cleaning is undesirable. Accordingly, the prevention of
the debris reattachment using non-neutral fluid is an advantageous
feature of the present invention. In some embodiments, the
non-neutral fluid comprises a solution having a pH not equal to 7.
In some embodiments, the non-neutral fluid comprises a solution
having a basic solution having a pH higher than 7 , such as a water
solution with an amount of sodium hydroxide. In some other
embodiments, the non-neutral fluid comprises a solution having an
acidic solution having a pH lower than 7, such as a water solution
with an amount of hydrochloric acid.
[0117] In some embodiments, the liquid 1318 comprises divalent
salts, such as CaCl, and MgCl.sub.2 which enhance the coagulation
of silica nanoparticles (5-500 nm) and/or the debris, such that the
debris reattachment to the substrate can be avoided. A person of
ordinary skill in the art appreciates that any other divalent salts
or any other chemicals that can facilitate the coagulation of the
debris are within the scope of the present invention. The term
"debris" used herein includes any particles formed during the
ablation with a laser, such as a femtosecond laser. The wavelength
of the femtosecond laser can be in the range from 300-2000 nm. In
some embodiments, the peak of the distribution of particle size is
between 90 and 150 nm. The particles can be colloidal silica or any
other particles that are generated when the laser ablates a
SiO.sub.2 purely/based material or a glass. The sizes of the debris
can be in the range from 25 nm to 500 nm.
[0118] In some embodiments, the liquid is adjusted to lower its
zeta potential, such that the coagulation or flocculation of the
debris (particles generated when the substrate received the laser
energy) occurs. In other embodiments, the liquid is adjusted to
have close to/near isoelectric point, such that the coagulation or
flocculation of the debris occurs. In some other embodiments, the
liquid is adjusted to lower the stability of the colloid in the
solution, such that the coagulation or flocculation of the debris
occurs. In some embodiments, the zeta potentials are brought to
below 10 mV, such that coagulation or flocculation occurs. In some
other embodiments, the zeta potentials are brought to below 5 or
between 0-5 mV to facilitate the coagulation or flocculation.
[0119] In some embodiments, the solution is adjusted to have a pH
between 2.0 to 3.4. In other embodiments, the solution is adjusted
to have a pH between 2.0 to 3.0. In some other embodiments, the
solution is adjusted to be in an acidic condition. In some
embodiments, the solution contains sulfuric acid having a pH around
1.0, such that the debris does not reattach to the substrate. In
some other embodiments, the solution contains citric acid having a
pH around 2.0-3.0, such that the debris does not reattach to the
substrate.
[0120] A person of ordinary skill in the art appreciates that any
chemicals that can be used to facilitate the removal of the debris
or particles floating in the solution are within the scope of the
present invention, such as adding NaCl, CaCl.sub.2, MgCl.sub.2, or
any other salts.
[0121] FIG. 13A is a flow chart illustrating an encapsulated
through-feature forming method 1350 in accordance with some
embodiments of the present invention. The method can start from a
step 1351. At Step 1352, a predetermined machining profile is
loaded into a laser scanning apparatus. The predetermined machining
profile can be any through-features to be cut out from a substrate.
At Step 1354, the substrate is placed on a holder. The back of the
holder is open and the back surface of the substrate, such as a
brittle material, is in contact with a liquid. At Step 1356, the
laser beam is adjusted to focus on the back surface of the
substrate. At Step 1358, the focus is moved upward until to the top
of the substrate and repeat the process along the predetermined
machining profile. The liquid aids in machining and the removal of
the debris. When the machining is completed, the waste generated
falls out due to gravity. The through-features can be any shapes or
features, such as a dual-chamfered edge. The method can be used to
form chamfers in any angles in any degrees, such as 45 degree, any
predetermined depth, round chamber of a predetermined radius, or a
concave chamfer.
[0122] FIGS. 14A-14C illustrate a material shaping method 1400 with
predetermined paths and patterns. The method 1400 can use laser
beams making various scanning patterns to shape the substrate 1408.
In some embodiments, the scanning patterns contains a raster scan
pattern.
[0123] In some embodiments, the laser device keeps the tool fixed
and translates the brittle material with respect to the laser
device (tool) in order to form a tool path. In some other
embodiments, the laser device provides a coordinated combination of
scanning/moving the tool and translating the brittle material.
[0124] The method disclosed herein can be used for forming a
large-area chamfer. In some embodiments, the present invention
divided the full chamfer into smaller chucks/zones. In some
embodiments, the chucks/zones are 1/2 of the size of the lens
field-of-view (FOV). Further in some embodiments, each of the
chamfer chucks are divided into layers, where the stack of the
layers forms the predetermined 3D profile of the chamfer. In some
embodiments, a laser scan/beam is set to scan a layer of one the
chucks with a single laser scan pattern. Each of the scan pattern
is indexed to a specific starting location on the material
perimeter of the substrate. The index locations of subsequent
layers are offsets by a specific amount, such that any and all edge
effects are averaged out over the full pattern, resulting in a
smooth and constant chamfer around the entire part. A computer
software can be programmed to form the predetermined chamfer
profile. In some embodiments, a stage encoder positions are fed
into the scan controller so that both the stage and scanner can be
moving during the formation of the chamfer.
[0125] FIG. 14A illustrates forming a scanning pattern in
accordance with some embodiments of the present invention. A laser
beam is applied on the substrate 1408 to form a shape 1402 of a
protective glass cover of a consumer electronic device. The
formation of the shape 1402 is performed section-by-section along
the contour of the shape 1402. The section 1404 is first scanned
with a Raster pattern within an area 1404A of the section 1404.
Next, the section 1406 is scanned with a Raster pattern with an
area 1406A of the section 1406. In some embodiments, each of the
sections 1404 and 1406 are few microns (such as 3-10 microns) in
its length.
[0126] In some embodiments, the scanning sections 1404 and 1406 are
staggered to minimize and/or avoid edge effects. For example, a
scanning section 1410 has an overlapping area with the scanning
section 1412. The scanning section 1410 can begin from the point
1410A and end at 1410.B. After the scanning laser beam reaches
point 1410B, the beam shifts down and scans in the reverse
direction back to the point 1410A. The similar pattern is performed
until the predetermined Raster pattern has ben performed within the
area section 1410. After the completion of the section 1410, a
second section 1412 is formed with a similar pattern as described
above. The beginning point 1412A of the section 1412 overlaps at
least a portion of the area of section 1410 to minimize or avoid
the edge effects.
[0127] FIG. 14B illustrates the scanning sequences of the Raster
pattern in accordance with some embodiments of the present
invention. The scanning by laser beams begins from point 1410A to
1410B (horizontally from left side to right side) forming a
scanning path 1410C. Next, the scanning point begins from 1410E,
which is vertically downward shifted with a portion of a Raster
width, to 1410F (horizontally from right to left) forming a
scanning path 1410D. The scanning path 1410C and 1410D are parallel
to each other. Following the similar process until the entire
section 1410 is scanned, such that a first area section 1410 is
completed for scanning. Next, the area section 1412 is scanned with
the same process as described for the section 1410. In some
embodiments, the Raster width 1416 described above is twice as long
as the length of the scanning path 1410C. A person of ordinary
skill in the art would appreciate that the scanning length and gaps
between the scanning paths can be in any sizes, such as from 0.5
micron to 5 micron. The Raster scanning patterns are also
applicable to scan curve lines or any other shapes.
[0128] FIG. 14C illustrates a scan pattern progression in
accordance with some embodiments of the present invention. In some
embodiments, two motion patterns (e.g., laser beam and the
substrate) occurring simultaneously. The laser beam is moving
and/or scanning across the field defined by the box 1430. The
substrate is moving with respect to the box 1430, such that the
scanning field covers a new portion of the substrate continuously.
Both laser beam and the substrate are constantly moving. A laser
beam in raster scan pattern 1410, 1412, and 1420 is applied to each
line segment area within the box 1430 with multiple sweeps to
remove multiple depth layers of materials from a discrete
transverse profile. While the part that is moving with respect to
the scan field as the raster scan is taking place, one or more
control algorithms and executable computer instructions stored in a
computer tracks where to scan the laser beam so that the actual
laser beam application area remains stationary on the part, even
though the part is moving. Once a segment (such as line 1410A) is
complete, the scanner directs the laser beam to the next segment
which is entered the scan field.
[0129] The following is an example of a laser scanning process. As
described above, a portion of the area section 1410 overlaps with
the area section of 1412 (FIG. 14A). The scanning of the section
1410 can start at right side portion 1410A. The second scanning
beam can be applied in the center portion 1410B. The third scanning
beam can be applied to the left side portion 1410C of the section
1410. The second group of scanning can begin, similar to the
scanning pattern applied to the section 1410, at the right side
portion 1412A, which connects to the left side portion 1410C. A
second scanning beam of the second group of scanning is applied in
the center 1412 of the section 1412. A third scanning beam of the
second group of scanning is applied at the left side portion 1412C
of the section 1412. Similar patterns are applied when forming
curved patterns 1420, starting from right bottom corner 1420A,
center 1420B, and then 1420C of the left top corner. The vertical
shaping can follow similar pattern described above by continuing
the shaping line of left top corner 1420C and performing bottom
shaping pattern 1122A and center shaping pattern 1422B. Similar
process can be performed along the predetermined profile line of
the predetermined shape.
[0130] FIG. 15 illustrates encapsulated through-holes shaping
method 1500, which can be used to shape a layered brittle material
1502. The laser apparatus described above is able to be used to
form one or more through-holes 1504 with pre-determined
characteristic dimensions, such as hole diameter and
center-to-center spacing. In some embodiments, the through-holes
are arranged in an array having an acoustic transfer function for
the resultant brittle material portion 1506, such as the speaker or
microphone portals in a smart phone. The encapsulated through-hole
array 1504A can be fabricated by shaping the brittle material in a
specific hole-by-hole order generating debris 1508, in order to
control mechanical or chemical coupling between shaping steps. The
through-holes can be shaped using a predetermined algorithm that
minimizes deleterious stress profiles in the brittle material. In
some embodiments, the method can be used to cut/separate the
material into separate portions.
[0131] FIG. 16 illustrates a system 1600 for shaping brittle
materials. The system 1600 comprises a computer 1602, a scan
controller 1604, motion controller 1606, a stage 1608, a optical
controlling elements 1610, such as galvo that drives mirrors for
steering the laser beams. The computer can command the motion
controller 1606 for a motion of the stage 1608 and command the scan
controller 1604 to emit laser beams based on the configurations of
the optical elements 1610.
[0132] FIG. 17 is a flow chart illustrating cutting a brittle
material method 1700 using a single laser in accordance with some
embodiments of the present invention. The method 1700 starts from a
step 1702. In a step 1704, a device is programmed for shaping a
brittle material with predetermined edge shape and/or surface
morphology. In a step 1706, a laser beam is applied to the brittle
material along a programmed tool path. In a step 1708, the brittle
material is shaped with a controlled edge shape and/or surface
morphology. In some embodiments, the controlled edge shape and/or
surface morphology is formed on the brittle material via the laser
induced breakdown of a portion of the brittle material. In a step
1710, a separation of a predetermined area of the brittle material
is performed, where at least one portion of the predetermined area
has predetermined edge shape and/or surface morphology. In some
embodiments, the separation is done by using the laser. In some
other embodiments, the separation is done by using a mechanical
force. The method 1700 stops at a step 1712.
[0133] The methods and devices disclosed herein provide many
advantageous aspects in commercial and/or industrial uses such that
the surface of the shaped brittle material does not require
additional after-shaped treatment process. In contrast, typical
methods and devices require many after-shaped mechanical treatment
steps, such as grinding, polishing, etching, annealing, chemical
bath, and ion-exchange treatments.
[0134] Further, the methods and devices disclosed herein are able
to make through-hole features and/or various shapes, such as
chamfer, on a brittle material.
[0135] The methods and devices disclosed herein are able to be
utilized to shape any amorphous solid materials, such as glass
cover for electronic devices, solar panel, ITO (indium tin oxide),
soda-lime glasses, windows, and wind shield of an automobile.
[0136] In operation, the method of the present invention comprises
providing a stock of brittle material and applying one or more
laser beams (such as femtosecond laser beams) to a portion of the
brittle material causing the separation of the material into two or
more portions in a way that precisely controls the geometric shape
and/or surface morphology of the edge(s) of at least one of the
separate portions.
[0137] The present invention has been described in terms of
specific embodiments incorporating details to facilitate the
understanding of principles of construction and operation of the
invention. Such reference herein to specific embodiments and
details thereof is not intended to limit the scope of the claims
appended hereto. It is readily apparent to one skilled in the art
that other various modifications can be made in the embodiment
chosen for illustration without departing from the spirit and scope
of the invention as defined by the claims.
* * * * *