U.S. patent application number 15/238987 was filed with the patent office on 2016-12-08 for low temperature hermetic sealing via laser.
The applicant listed for this patent is Guardian Industries Corp.. Invention is credited to Martin D. BRACAMONTE, Vijayen S. VEERASAMY.
Application Number | 20160356074 15/238987 |
Document ID | / |
Family ID | 49304351 |
Filed Date | 2016-12-08 |
United States Patent
Application |
20160356074 |
Kind Code |
A1 |
VEERASAMY; Vijayen S. ; et
al. |
December 8, 2016 |
LOW TEMPERATURE HERMETIC SEALING VIA LASER
Abstract
A method and apparatus for low temperature laser sealing of
bonded articles is disclosed. Hermetic sealing of glass substrates
using low temperature sealing techniques that do not adversely
affect bulk strength of glass substrates, the environment created
between the substrates and/or any components housed within the
sealed glass substrates is disclosed. Such low temperature sealing
techniques include use of localized laser heating of sealing
materials to form a hermetic seal between glass substrates that
does not involve heating the entire article to be sealed.
Inventors: |
VEERASAMY; Vijayen S.; (Ann
Arbor, MI) ; BRACAMONTE; Martin D.; (Pinehurst,
NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Guardian Industries Corp. |
Auburn Hills |
MI |
US |
|
|
Family ID: |
49304351 |
Appl. No.: |
15/238987 |
Filed: |
August 17, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13628653 |
Sep 27, 2012 |
9441416 |
|
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15238987 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E06B 3/6612 20130101;
H01L 2924/1461 20130101; E06B 3/67334 20130101; H01L 2924/12044
20130101; E06B 3/667 20130101; E06B 3/673 20130101; E06B 3/6733
20130101; C03C 8/24 20130101; C03C 27/10 20130101; C03C 27/08
20130101; E06B 3/6775 20130101; E06B 3/66352 20130101; H01L
2224/83896 20130101; E06B 3/66333 20130101; E06B 3/66 20130101;
E06B 3/66342 20130101; H01L 2924/1461 20130101; H01L 2924/00
20130101; H01L 2924/12044 20130101; H01L 2924/00 20130101 |
International
Class: |
E06B 3/66 20060101
E06B003/66; C03C 27/08 20060101 C03C027/08; C03C 8/24 20060101
C03C008/24; C03C 27/10 20060101 C03C027/10; E06B 3/677 20060101
E06B003/677; E06B 3/673 20060101 E06B003/673 |
Claims
1-7. (canceled)
8. A method of making a vacuum insulated glass (VIG) window unit,
the method comprising: providing a first substrate; applying a seal
material to an area of the first substrate to be sealed; forming a
seal by at least: vitrifying the seal material using laser
irradiation, the laser irradiation exposing the seal material but
not being directed toward a majority of the first substrate;
bonding the first substrate to a second substrate by continuing to
irradiate the vitrified seal material with laser irradiation to
melt the seal material; and evacuating a cavity formed between the
first and second substrates and defined by the seal to a pressure
lower than atmospheric pressure.
9. The method of claim 8, wherein said first and second substrates
comprise glass, and wherein said seal material comprises a glass
based frit.
10. The method of claim 9, wherein said glass based frit includes
an absorbing dye that absorbs laser energy.
11. The method of claim 8, further comprising: applying pressure to
one or both of the substrates during at least the bonding step, and
wherein each of the first and second substrates comprises
glass.
12. The method of claim 11, wherein said step of applying pressure
includes pumping out the cavity and/or applying pressure via a
roller.
13. The method of claim 8, wherein application of said laser
irradiation is controlled via a feedback loop.
14. The method of claim 13, wherein the feedback loop includes
information regarding a temperature in an area of the laser
irradiation.
15. The method of claim 8, wherein the laser irradiation is from
one or more of a YVO4 laser, a TI:Sapphire laser, a Cu vapor laser,
an excimer laser, a CO.sub.2 laser, an Nd:YAG laser, and a harmonic
of an Nd:YAG laser.
16. The method of claim 8, wherein the laser irradiation is pulsed
and/or continuous.
17. The method of claim 8, wherein laser irradiation is performed
by dual beams directed to opposite sides of the VIG window unit,
said dual beams rastering in opposite directions.
18. The method of claim 17, wherein the beams raster at a rate in
the range of about 100-150 mm/sec.
19. The method of claim 8, wherein laser irradiation is performed
by a single beam rastering in a single direction.
20. The method of claim 8, wherein said seal material comprises a
layer comprising metallic or substantially metallic solder.
21. The method of claim 20, wherein an absorber film is interposed
between the layer comprising solder and at least one of the
substrates.
22. The method of claim 21, wherein laser energy from said laser
irradiation is absorbed by said absorber film that in turn heats
and melts seal material in the layer comprising solder.
23. The method of claim 21, wherein said absorber film comprises
one or more of: (i) a layer comprising silicon nitride, (ii)
Si-rich silicon nitride characterized by Si.sub.zN.sub.x where z/x
is at least 0.78; and (iii) a layer comprising silicon nitride and
a layer comprising Ni and/or Cr.
24. The method according to claim 8, further comprising depositing
a metal oxide layer on the first and/or second glass substrates
prior to applying said seal material.
25. The method of claim 8, further comprising, after said bonding,
annealing the seal by laser irradiation.
26. The method of claim 8, wherein application of the laser to the
seal material is performed by the laser passing substantially
through the first and/or second substrate and irradiating the seal
material.
27. The method of claim 8, wherein application of the laser to the
seal material is performed from a side so that the laser does not
pass through either the first or second substrate of the VIG unit
to irradiate the seal material.
28. The method of claim 8, wherein the vitrifying and/or bonding
steps are performed (i) in air and/or in an inert atmosphere,
and/or (ii) at approximately room temperature.
29. The method of claim 8, further comprising: providing a
thermally conductive heat sink in thermal contact with at least one
of the substrates to control lateral heat flow during laser
irradiation.
30. A method of making an article including a sealed cavity formed
between substrates, the method comprising: providing first and
second substrates comprising glass; applying a sealing material to
at least one of the substrates; and forming a seal by irradiating
the sealing material with a laser, wherein said cavity is defined
by geometries of the substrates and the seal.
31. The method of claim 30, further comprising evacuating the
cavity to a pressure lower than atmospheric pressure.
32. The method of claim 30, wherein a temperature sensitive
component is disposed in said cavity.
33. The method of claim 32, wherein said temperature sensitive
component includes at least one of a semiconductor chip, a sensor,
an optical component, organic light emitting layers, and/or an
OLED.
34. The method of claim 30, wherein said seal is a hermetic
seal.
35. The method of claim 30, wherein said seal material comprises a
glass based frit, or a layer comprising metallic or substantially
metallic solder.
36. The method of claim 30, further comprising annealing the seal
via laser irradiation.
37. The method of claim 30, further comprising: providing a
thermally conductive heat sink in thermal contact with at least one
of the substrates to control lateral heat flow during laser
irradiation.
38. The method of claim 30, wherein application of said laser
irradiation is controlled via a feedback loop.
39. The method of claim 38, wherein the feedback loop (a) includes
information regarding a temperature in an area of the laser
irradiation, and/or (b) is used to control a power and duration of
said laser irradiation.
Description
TECHNICAL FIELD
[0001] The disclosure relates generally to hermetic sealing of
substrates that form packages that hold a vacuum, such as, for
example, vacuum insulated glass (VIG) window units, or that house
sensitive components in an inert atmosphere, such as, for example,
sensitive materials including, but not limited to, organic light
emitting layers, semiconductor chips, sensors, optical components,
or the like. The disclosure more particularly relates to hermetic
sealing of substrates (e.g., glass substrates) using low
temperature sealing techniques that do not adversely affect the
substrates, the environment created between the substrates and/or
any components housed within the sealed substrates. Such low
temperature sealing techniques include use of localized laser
heating of sealing material(s) to form a hermetic seal between
glass substrates that does not involve heating the entire article
to be sealed. The low temperature techniques disclosed herein may
also be referred to as sealing under non-thermal equilibrium
conditions.
BACKGROUND AND SUMMARY OF EXAMPLE EMBODIMENTS
[0002] Hermetic sealing of glass substrates to create a vacuum or
inert gas environment therebetween is typically made possible using
barriers of usually glassy or metallic (e.g., eutectic) materials
that are impermeable to ingress of gasses over a long time period,
typically many orders of magnitude longer than the device operating
lifetime. As will be understood, permeability involves two steps.
These steps include dissolution and diffusion. Heremetic sealing
keeps, for example, water, other liquids, oxygen and other gaseous
contaminant molecules out of packages that hold, for example, and
without limitation, a vacuum (e.g., VIG window units, thermos
flask, MEMS, and the like), or sensitive materials, such as, for
example, and without limitation, organic emitting layers (e.g.,
used in OLED devices), semiconductor chips, sensors, optical
components, or the like, held in an inert atmosphere. Gas tight
packaging of the complex interiors of such assemblies has posed
obstacles in the later stages of processing of such packages, such
as, for example prior to pumping and tip fusing in the case of VIG
window units, or last processing steps in the manufacture of OLED
devices.
[0003] Some example VIG configurations are disclosed, for example,
in U.S. Pat. Nos. 5,657,607, 5,664,395, 5,657,607, 5,902,652,
6,506,472 and 6,383,580, the disclosures of which are all hereby
incorporated by reference herein in their entireties.
[0004] FIGS. 1 and 2 illustrate a typical VIG window unit 1 and
elements that form the VIG window unit 1. For example, VIG unit 1
may include two spaced apart substantially parallel glass
substrates 2, 3, which enclose an evacuated low-pressure
space/cavity 6 therebetween. Glass sheets or substrates 2, 3 are
interconnected by a peripheral edge seal 4 which may be made of
fused solder glass or the like, for example. An array of support
pillars/spacers 5 may be included between the glass substrates 2, 3
to maintain the spacing of substrates 2, 3 of the VIG unit 1 in
view of the low-pressure space/gap 6 present between the substrates
2, 3.
[0005] A pump-out tube 8 may be hermetically sealed by, for
example, solder glass 9 or the like to an aperture/hole 10 that
passes from an interior surface of one of the glass substrates 2 to
the bottom of an optional recess 11 in the exterior surface of the
glass substrate 2, or optionally to the exterior surface of the
glass substrate 2. A vacuum is attached to pump-out tube 8 to
evacuate the interior cavity 6 to a low pressure that is less than
atmospheric pressure, for example, using a sequential pump down
operation. After evacuation of the cavity 6, a portion (e.g., the
tip) of the tube 8 is melted to seal the vacuum in low pressure
cavity/space 6. The optional recess 11 may retain the sealed
pump-out tube 8. Optionally, a chemical getter 12 may be included
within a recess 13 that is disposed in an interior face of one of
the glass substrates, e.g., glass substrate 2. The chemical getter
12 may be used to absorb or bind with certain residual impurities
that may remain after the cavity 6 is evacuated and sealed.
[0006] VIG units with peripheral hermetic edge seals 4 (e.g.,
solder glass) are typically manufactured by depositing glass frit
or other suitable material in a solution (e.g., frit paste) around
the periphery of substrate 2 (or on substrate 3). This glass frit
paste ultimately forms the edge seal 4. The other substrate (e.g.,
3) is brought down on substrate 2 so as to sandwich spacers/pillars
5 and the glass frit solution between the two substrates 2, 3. The
entire assembly including the glass substrates 2, 3, the
spacers/pillars 5 and the seal material (e.g., glass frit in
solution or paste), is then typically heated to a temperature of at
least about 500.degree. C., at which point the glass frit melts,
wets the surfaces of the glass substrates 2, 3, and ultimately
forms a hermetic peripheral/edge seal 4.
[0007] After formation of the edge seal 4 between the substrates, a
vacuum is drawn via the pump-out tube 8 to form low pressure
space/cavity 6 between the substrates 2, 3. The pressure in space 6
may be produced by way of an evacuation process to a level below
atmospheric pressure, e.g., below about 10.sup.-2 Torr. To maintain
the low pressure in the space/cavity 6, substrates 2, 3 are
hermetically sealed via the edge seal and sealing off of the
pump-out tube. Small high strength spacers/pillars 5 are provided
between the transparent glass substrates to maintain separation of
the approximately parallel glass substrates against atmospheric
pressure. As noted above, once the space 6 between substrates 2, 3
is evacuated, the pump-out tube 8 may be sealed, for example, by
melting its tip using a laser or the like.
[0008] High-temperature bonding techniques such as, for example,
anodic bonding and glass frit bonding, as discussed above, have
been widely used method for hermetically sealing (e.g., forming an
edge seal) components made of silicon, ceramics, glass, or the
like. The heat required for these high-temperature processes is
typically in the range of about 300.degree. C. to 600.degree. C.
These conventional bonding techniques typically require
oven-intensive bulk heating in which the entire device (including
the glass and any components housed within the glass housing) comes
to near thermal equilibrium with the oven for a seal to form. As a
result, a relatively long period of time is required to achieve an
acceptable seal. For example, as the device size L increases, the
sealing time may typically increase on the order of L.sup.3. It is
also the case that the most temperature sensitive component
determines the maximum allowable temperature of the entire system.
Thus, high-temperature sealing processes discussed above (e.g.,
anodic bonding and glass frit bonding) are not suitable for
fabricating heat-sensitive components such as, for example,
tempered VIG units and encapsulating sensitive components, such as,
for example, OLED devices. In the case of tempered VIG units, the
thermally tempered glass substrates of a VIG unit would rapidly
lose temper strength in the high-temperature environment. In the
case of an example OLED package, certain functional organic layers
would be destroyed at temperatures of 3000-600 degrees C.
(sometimes even as low as 100.degree. C.). In the past, one way to
address this with high-temperature bulk sealing processes was to
develop lower temperature frits, while still using bulk thermal
equilibrium heating processes.
[0009] By way of background, glass fits and/or solders are
typically mixtures of glass material and metallic oxides. Glass
composition may be tailored to match the coefficient of thermal
expansion (CTE) of the bonding substrates. Lead-based glasses are
the most common bonding/sealing material/technique used
commercially in cathode ray tubes (CRT), plasma displays and VIG
window units. Lead-based glass fits are also among the least
permeable glass sealing materials. Traditionally, these solders are
based on glassy materials and de-vitrification is suppressed.
[0010] Glass fits or solders are typically made up of a base glass,
a refractory filler and a vehicle. The base glass forms the bulk of
the frit or solder. The filler reduces the CTE as well as matching
it to the glass substrates to be joined. This matching enhances the
mechanical strength, reduces interfacial stress and improves the
crack resistance of the seal. The vehicle is typically made of a
solvent that provides fluidity for screen printing and an organic
binder.
[0011] Among the advantages of these types of glass fits or solders
is that they include a relatively low melting point (e.g., in a
range of about 480.degree. C.-520.degree. C.) glass that will stick
to most semiconductor materials, including, but not limited to,
glass, silicon, silicon oxide, most metals and ceramics, making
bonding techniques using these types of materials versatile and
widely accepted.
[0012] There are many different types of commercially available
glass frit materials having various melting points, CTEs, organing
binders and screen printing properties. However, almost all lower
melting point formulations of glass frit or solder contain some
lead. This may potentially become a major drawback, as the EU and
Japan are severely limiting, if not forbidding, the use of lead in
electronics manufacturing in the coming years. In the last few
years, fits or solders based on bismuth oxides have had some
success in replacing lead based frits, however the melting
temperature (Tg) of these types of frits is still typically above
about 450.degree. C. As with lead based fits, these bismuth oxide
based fits cannot be used for fabrication of temperature sensitive
devices using conventional oven bulk heating processes. Lower Tg
(e.g., 375.degree. C.-390.degree. C.) fits based on vanadium barium
zinc oxides (VBZ) have also been developed, including, but not
limited to, VBaZn, V phosphates, SnZnPO.sub.4. However, widespread
usage of these types of fits has heretofore been limited.
[0013] Therefore, there exists a need for a seal processing
technique that does not involve heating the entire article to be
sealed to high temperature(s). In other words, a technique that
utilizes localized heating substantially limited to an area in
which the material used to form the seal, for example,
frit-inclusive seal material, is disposed is needed. Such a
localized approach may be achieved, for example, and without
limitation, via controlled laser heating of the seal material and
resulting vitrified solder bead. In such a technique, the localized
heating may be limited to the frit, or an area proximate where the
frit is deposited, and the heating profile may be kept moderate. It
may also be advantageous to include a system for localized heat
sinking to control lateral heat flow to reduce cracking due to
stress and the relatively large differences in expansion
characteristics and temperature gradients. The molten seam or bead
formed using this type of localized process is used to join the
desired parts, e.g., the glass substrates of a VIG unit. This
process may be referred to as laser stitching since the molten seam
or bead in effect stitches the joining parts together. According to
certain alternative example embodiments, such localized controlled
laser heating may also be used with eutectic sealing materials.
[0014] In conventional oven bulk heating processes, a frit paste is
typically applied to a glass substrate and, in a process referred
to as drying, is heated at a relatively low temperature (e.g., in a
range of about 120.degree. C.-150.degree. C.) to remove the solvent
from the vehicle. Next, the glass is heated to a higher temperature
in a glazing process to glaze the frit and drive out the organic
binder material. In a subsequent vitrification process frit is then
vitrified by raising its temperature to its melting point to form a
continuous film comprising the glass network. Finally, the glass
substrates are aligned and heated above the glass melting
temperature while the substrates are squeezed together to form the
final hermetic seal between the substrates.
[0015] According to an example, non-limiting embodiment, after the
frit paste is applied, dried and glazed, localized vitrification
(e.g., instead of bulk oven processing) is performed using a laser
in air or an inert atmosphere. During this process, it may be
preferable to include localized heat sinking to control lateral
heat flow. A roller mechanism or application of a vacuum pump-down
may optionally be used to apply force between the substrates being
joined together. The substrates are aligned and the frit sealing
material is brought to temperature(s) above its melting temperature
by localized laser irradiation to perform laser induced bonding of
the frit and/or solder to the glass substrate(s). In a subsequent
step, laser annealing of the solder may also be performed to reduce
the stress between the seal and the substrate(s). It has also been
found that roughening of the glass prior to the application of the
frit sealing material provides improved bonding strength of the
frit to glass interface.
[0016] According to another example, non-limiting embodiment, the
localized heating approach may be achieved via controlled laser
heating of the vitrified solder bead and/or seam. The amount of
power delivered to the frit may be controlled by a feedback loop
using the temperature at some distance from the thermal spike as
input to a feedback loop. Monitoring and controlling the high
process temperatures in the joining area via feedback control of
the laser power and duration provides advantages in managing the
stress and breakage of the device.
[0017] According to certain alternative example embodiments, a
eutectic sealing material (e.g., metallic or metal alloy solder)
may be used instead of glass based or glass inclusive frit sealing
materials. In such alternative example embodiments, because metal
cannot typically be used directly on glass, an absorber layer may
be interposed between the eutectic seal material and the glass
substrate(s). The absorber film/layer may, for example, and without
limitation, include a first layer of or including silicon nitride
and a second layer of or including a metal such as electrodeless Ni
(or a metal alloy). In such example embodiments, the energy of the
laser beam is transmitted through a glass substrate and absorbed by
the absorber film. As a result, for example, the Si and/or metal of
the absorber locally heats up, melts the eutectic material, and the
Si is bonded to the glass substrate(s). As noted above, control of
the laser may be achieved using a feedback loop in which the high
process temperatures in the joining area are monitored and fed back
to control the laser power and duration.
[0018] In certain example embodiments of this invention, there is
provided a method of making a vacuum insulated glass (VIG) window
unit, the method comprising: providing a first substrate; applying
a seal material to an area of the first substrate to be sealed;
forming a seal by at least (a) vitrifying the seal material using
laser irradiation, the laser irradiation exposing the seal material
but not being directed toward a majority of the first substrate,
and (b) bonding the first substrate to a second substrate by
continuing to irradiate the vitrified seal material with laser
irradiation to melt the seal material; and evacuating a cavity
formed between the first and second substrates and defined by the
seal to a pressure lower than atmospheric pressure.
[0019] In certain example embodiments, there is provided a method
of making a bonded article having a cavity formed between two glass
substrates, comprising: providing first and second glass
substrates; applying a sealing material to one of the glass
substrates; and forming a seal by irradiating the sealing material
with a laser, wherein said cavity is defined by geometries of the
glass substrates and the seal, wherein the cavity is either reduced
to a pressure below atmospheric pressure or provided with an inert
gas atmosphere and may have disposed therein temperature sensitive
components.
[0020] In certain embodiments of this invention, there is provided
a vacuum insulated glass (VIG) window unit, comprising: first and
second substantially parallel spaced apart substrates comprising
glass that are bonded together by an edge seal, said first and
second substrates and said edge seal defining a cavity having a
pressure lower than atmospheric pressure; and wherein said edge
seal comprises (i) a metallic or substantially metallic layer; and
(ii) an absorber film. The edge seal may be formed via at least
laser irradiation.
[0021] These and other embodiments and advantages are described
herein with respect to certain example embodiments and with
reference to the following drawings in which like reference
numerals refer to like elements, and wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a cross sectional schematic diagram of a
conventional VIG unit;
[0023] FIG. 2 is a top plan view of a conventional VIG unit;
[0024] FIG. 3 is a schematic partial cross sectional diagram
illustrating a VIG unit and seal material being irradiated by a
laser according to an example embodiment;
[0025] FIG. 4 is a schematic partial cross sectional diagram
illustrating a VIG unit and seal material including an absorber
film and eutectic seal material being irradiated by a laser
according to another example embodiment;
[0026] FIG. 5 is a schematic partial cross sectional diagram
illustrating an electronic component package and seal material
being irradiated by a laser according to an example embodiment;
[0027] FIG. 6 is a schematic partial cross sectional diagram
illustrating an electronic component package and seal material
including an absorber film and eutectic seal material being
irradiated by a laser according to another example embodiment;
[0028] FIG. 7 is a schematic block diagram illustrating a laser
irradiation system including feedback control according to certain
example embodiments; and
[0029] FIG. 8 is a flowchart illustrating a method of sealing
substrates using a laser according to certain example
embodiments.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0030] Certain example embodiments will be described in detail
herein with reference to the foregoing drawings in which like
reference numerals refer to like elements. It will be understood
that the embodiments described herein are intended to be
illustrative, not limiting, and that those skilled in the art will
understand that various modifications may be made without departing
from the true spirit and full scope of the claims appended
hereto.
[0031] With reference to FIG. 3, a schematic partial cross
sectional diagram illustrating a VIG unit and seal material being
irradiated by a laser according to an example embodiment is
provided. The VIG unit 1 may include two spaced apart substantially
parallel glass substrates 2, 3, which enclose an evacuated
low-pressure space/cavity 6 therebetween. Glass sheets or
substrates 2, 3 are interconnected by a peripheral edge seal 4
which may be made of fused solder glass or the like, for example,
that may be formed using a laser 40 as described below with
reference to certain example embodiments. An array of support
pillars/spacers 5 may be included between the glass substrates 2, 3
to maintain the spacing of substrates 2, 3 of the VIG unit 1 in
view of the low-pressure space/gap 6 present between the substrates
2, 3. A vacuum is drawn via the pump-out tube 8 to form low
pressure space/cavity 6 between the substrates 2, 3. The pressure
in space 6 may be produced by way of an evacuation process to a
level below atmospheric pressure, e.g., below about 10.sup.-2 Ton.
To maintain the low pressure in the space/cavity 6, substrates 2, 3
are hermetically sealed via the edge seal 4 and sealing off of the
pump-out tube 8. As noted above, small high strength
spacers/pillars 5 are provided between the transparent glass
substrates to maintain separation of the approximately parallel
glass substrates against atmospheric pressure. As noted above, once
the space 6 between substrates 2, 3 is evacuated, the pump-out tube
8 may be sealed, for example, by melting its tip using a laser or
the like.
[0032] According to certain example embodiments, the edge seal 4 is
formed by controlled localized heating via a laser 40, as will be
described in greater detail herein. Because of the large
temperature gradient between the molten glass frit and the much
cooler, for example, room temperature, glass substrates 2, 3, it
may be preferable to include a localized heat sink 30, comprising a
material having good thermal conductivity, such as, for example,
and without limitation, copper, or the like and having good thermal
contact with the substrate 3. Additionally, control of laser power
in continuous or pulse mode may be accomplished using a feedback
loop that informs a laser power control unit of temperatures in the
vicinity of the molten seam or bead, thereby enabling control of
the power and duration of laser heating. It will be understood that
a pulsed or continuous application of laser energy may be used
according to certain example embodiments. An example feedback
control arrangement is discussed below with reference to FIG. 7,
and is advantageous in controlling and managing stress and breakage
of the device that might otherwise occur. The laser heat processing
technique described herein does not involve heating of the entire
article to be hermetically sealed, and instead uses a localized
approach achieved by controlled laser heating of the vitrified
solder bead to achieve low temperature or non-thermal equilibrium
sealing.
[0033] In particular, laser based sealing using glass based solder
materials according to certain example embodiments subjects
primarily the solder to heat and subjects the remainder of the
component being sealed to relatively minimal thermal loading. It is
noted that the laser based sealing techniques disclosed herein work
equally well with both low (e.g., VBZ type fits) and high Tg frit
materials. Non-limiting examples of suitable low Tg fits include,
but are not limited to, solders based on V, Ba, Zn, POx, VPOx, or
the like. Another advantage of the laser based sealing techniques
disclosed herein is that the solder is readily processable in air
at ambient temperatures and pressures. The frit matrix that is used
to form the edge seal 4 preferably includes an absorber dye that
can be tuned to the wavelength of the laser being used. In this
manner, the glass of the substrates 2, 3 allows the laser energy to
pass through without significant absorption, leaving the substrate
glass relatively unheated, while at the same time, the laser energy
is absorbed by the frit material, thereby selectively heating the
frit material to vitrify the frit and bond the substrates with a
hermetic glass seal. It may also be preferable to incorporate two
beams that raster about opposite edges of the substrates in
opposite directions to improve speed and throughput, and to ensure
more complete frit vitrification and bonding. It will be understood
that a single beam raster of the substrate edge seal materials may
also be used to seal the substrates. According to certain
embodiments, when sealing substrates of a VIG window unit, active
pumping via a roughing pump, or the like, may be used to allow the
substrates to be kept or held in place during sealing, thereby
obviating the need for using clamps. In the case of sealing a
housing in which other components may be disposed, a roller may
also be used. Subsequent rasters of laser energy may be applied to
the bonded frit area after seal formation to anneal the seal to
thereby reduce stress and later failures caused by such stress,
including, for example, cracking of the seal. It will be further
understood that the application of laser energy according to the
various embodiments disclosed herein may be performed in a pulsed
or continuous manner According to certain example embodiments,
roughening of the glass prior to the application of the frit
sealing material provides improved bonding strength of the frit to
glass interface.
[0034] Because of the high temperature gradients experienced when
using the disclosed laser based sealing techniques, it may be
preferable to include a localized heat sink to reduce the lateral
flow of heat, for example, and without limitation, across the glass
substrate(s), or to the sensitive device area in embodiments in
which sensitive electronic components are sealed in a housing.
According to certain embodiments, a localized heat sink comprising
materials having good thermal conductivity properties, such as, for
example, and without limitation, copper, may be placed on an
underside of the package (e.g., on the opposite side of the laser
application) in a vicinity of the center of the underside of the
package, and with good thermal contact between the package and the
heat sink.
[0035] FIG. 5 is a schematic partial cross sectional diagram
illustrating an electronic component package and seal material
being irradiated by a laser according to an example embodiment. The
component package 50 may include two spaced apart glass substrates
52, 53, which enclose an evacuated low-pressure or inert gas
environment space/cavity 55 therebetween. An electronic or optical
component 56, such as, for example, and without limitation, a
semiconductor device, organic light emitting device (OLED),
electronic circuits, semiconductor chips, sensors, optical
components, or the like, may be housed in a cavity 55 formed
between the glass substrates 52, 53. Glass substrates 52, 53 are
interconnected by a peripheral edge seal 54 which may be made of
fused solder glass or the like, for example, that may be formed
using a laser as described below with reference to certain example
embodiments. The pressure in space 55 may be produced by way of an
evacuation process to a level below atmospheric pressure, e.g.,
below about 10.sup.-2 Ton. To maintain the low pressure in the
space/cavity 55, substrates 52, 53 are hermetically sealed via the
edge seal 4. The cavity 55 may also be provided with an inert
gaseous atmosphere in which the component 56 may be disposed.
[0036] According to certain example embodiments, the edge seal 4 is
formed, along the lines described above with reference to FIG. 3,
by controlled localized heating via a laser 40, as will be
described in greater detail herein. Because of the large
temperature gradient between the molten glass frit and the much
cooler, for example, room temperature, glass substrates 52, 53, it
may be preferable to include a localized heat sink 30, comprising a
material having good thermal conductivity, such as, for example,
and without limitation, copper, or the like. Additionally, control
of laser power in continuous or pulse mode may be accomplished
using a feedback loop that informs a laser power control unit of
temperatures in the vicinity of the molten seam or bead, thereby
enabling control of the power and duration of laser heating. It
will be understood that a pulsed or continuous application of laser
energy may be used according to certain example embodiments. An
example feedback control arrangement is discussed below with
reference to FIG. 7, and is advantageous in controlling and
managing stress and breakage of the device that might otherwise
occur. The laser heat processing technique described herein does
not involve heating of the entire article to be hermetically
sealed, and instead uses a localized approach achieved by
controlled laser heating of the vitrified solder bead to achieve
low temperature or non-thermal equilibrium sealing.
[0037] In particular, laser based sealing using glass based solder
materials according to certain example embodiments subjects
primarily the solder to heat and subjects the remainder of the
component being sealed to relatively minimal thermal loading. It is
noted that the laser based sealing techniques disclosed herein work
equally well with both low (e.g., VBZ type fits) and high Tg frit
materials. Non-limiting examples of suitable low Tg fits include,
but are not limited to, solders based on V, Ba, Zn, POx, VPOx, or
the like. Another advantage of the laser based sealing techniques
disclosed herein is that the solder is readily processable in air
at ambient temperatures and pressures. The frit matrix that is used
to form the edge seal 4 preferably includes an absorber dye that
can be tuned to the wavelength of the laser being used. In this
manner, the glass of the substrates 52, 53 allows the laser energy
to pass through without significant absorption, leaving the
substrate glass relatively unheated, while at the same time, the
laser energy is absorbed by the frit material, thereby selectively
heating the frit material to vitrify the frit and bond the
substrates with a hermetic glass seal. It is also preferable to
incorporate two beams that raster about opposite edges of the
substrates in opposite directions to improve speed and throughput,
and to ensure more complete frit vitrification and bonding. It will
be understood that a single beam raster of the substrate edge seal
materials may also be used to seal the substrates. According to
certain embodiments, when sealing substrates, active pumping via a
roughing pump, or the like, may be used to allow the substrates to
be kept or held in place during sealing. Alternatively, a roller
may also be used. Subsequent rasters of laser energy may be applied
to the bonded frit area after seal formation to anneal the seal to
thereby reduce stress and later failures caused by such stress,
including, for example, cracking of the seal. It will be further
understood that the application of laser energy according to the
various embodiments disclosed herein may be performed in a pulsed
or continuous manner.
[0038] Because of the high temperature gradients experienced when
using the disclosed laser based sealing techniques, it may be
preferable, as noted above, to include a localized heat sink 30 to
reduce the lateral flow of heat, for example, and without
limitation, across the glass substrate(s), or to the sensitive
device area in embodiments in which sensitive electronic components
are sealed in a housing. According to certain embodiments, a
localized heat sink comprising materials having good thermal
conductivity properties, such as, for example, and without
limitation, copper, may be placed on an underside of the package
(e.g., on the opposite side of the laser application) in a vicinity
of the center of the underside of the package, and with good
thermal contact between the package and the heat sink.
[0039] According to certain alternative example, non-limiting
embodiments, a eutectic seal material may be used to seal the glass
substrates in place of a glass based frit material. Metallic based
(or eutectic) solders have an even lower melting point that glass
based seal materials. However, eutectics typically may not be used
directly onto glass substrates because of the presence of oxygen
ions. In addition, when heated, the metal solder is oxidized and
beads up giving rise to puddles and micro-bubbles. To avoid these
problems that are sometimes attendant with using eutectic solders
to seal glass substrates, according to certain example embodiments,
an absorber or absorption film may be introduced between the glass
substrate and the eutectic material. According to this alternative
embodiment, the laser energy is transmitted through the highly
transparent glass substrate 52 and is absorbed by an absorber film,
such as, for example, and without limitation, a silicon rich
SiNx/Ni or SiNx/Cr double layer film. As a result, the silicon
heats up locally and melts the eutectic material thereby forming a
eutectic seal bonding the glass substrates. Optionally, as noted
above, a small force may be applied during processing to ensure
that the materials stay in contact during laser processing. Using
this bonding technique with an interlayer of SiNx/Ni or SiNx/Cr to
glass joining the silicon and glass are locally fused together in
the process while the surrounding glass material remains at room
temperatures. According to certain example, non-limiting
embodiments, a metal oxide layer may be pre-deposited onto the
glass substrates prior to frit (e.g., seal material) deposition to
wet the glass substrates and fill gaps, for example, by capillary
action. As discussed above, pulsed single shots or continuous
application of laser energy may be used. Forming eutectic hermetic
seals requires that one material (e.g., the substrate material) be
highly transmissive while the other material, e.g., the absorber
material, be strongly absorbing at the wavelength of the selected
laser beam.
[0040] FIGS. 4 and 6, are similar to the embodiments illustrated in
FIGS. 3 and 5, but include a eutectic solder material 4, 54,
respectively, together with an absorber film 4', 54', respectively,
as described and discussed in detail above. Moreover, it will be
understood that the absorber film 4', 54' may be disposed on one or
both glass substrates 2, 3, 52, 53. As discussed above, according
to this alternative example embodiment, because metal cannot
typically be used directly on glass, an absorber layer 4', 54' may
be interposed between the eutectic seal material 4, 54 and the
glass substrate(s) 2, 3, 52, 53. The absorber film/layer 4', 54'
may, for example, and without limitation, include a first layer of
or including silicon nitride and a second layer of or including a
metal such as electrodeless Ni (or a metal alloy). The absorber
film 4', 54', according to certain example non-limiting
embodiments, may comprise a dual layer of silicon rich SiNx/Ni or
SiNx/Cr In such example embodiments, the energy of the laser beam
40 is transmitted through a glass substrate 2, 3, 52, 53 and
absorbed by the absorber film 4', 54'. As a result, for example,
the Si and/or metal of the absorber locally heats up, melts the
eutectic material, and the Si is bonded to the glass substrate(s).
As noted above, control of the laser may be achieved using a
feedback loop in which the high process temperatures in the joining
area are monitored and fed back to control the laser power and
duration, as illustrated and described herein with reference to
FIG. 7.
[0041] Among the example advantages achieved using the laser
techniques disclosed herein are that the laser technique is a
substantially non-contact technique, hence there is no wear and
tear or contamination of the substrates being bonded. Additionally,
due to the controlled application of the laser beam, processing
time, temperature and volume being heated can be controlled very
precisely, thus even complex designs (especially in the case of
component packaging) may be realized. Further, when using a laser
as the heat source, the heat input to the device can be highly
localized since the laser beam can be focused to a small spot.
Moreover, in the VIG embodiments disclosed herein, the laser may
optionally be applied to the bead from the side instead of through
the glass substrate.
[0042] FIG. 7 is a schematic block diagram illustrating an example
laser irradiation system including feedback control according to
certain example embodiments. The laser system according to this
example non-limiting embodiment includes a laser source 78 that
provides laser energy of a given power and duration to a scanner
and optics subsystem 80. The scanner and optics subsystem 80
provides a beam of a given spot size via the optics to the object
being irradiated, such as, for example, a VIG window unit 1. The
scanner and optics subsystem 80 may provide a single beam that
rasters about a periphery of the VIG window unit 1 in a given
direction, or optionally may provide two beams 40 that are applied
to opposite sides of the VIG unit 1 and raster in opposite
directions. According to certain example embodiments, the laser
beams 40 may be arranged to irradiate opposite sides (e.g., top and
bottom) of the VIG window unit 1. According to still further
example embodiments, a SWIR heater may be used in conjunction with
the application of laser beam(s) 40. The laser beams 40 may be held
and moved by robot arms to provide even greater raster control. A
sensor 72, that is preferably remote from the beam monitors the
temperature Ts in the vicinity of the bead. The sensor 72 may be
any suitable type of sensor that can monitor temperatures, such as,
for example, Ts. Such sensors may include, for example, and without
limitation, a pyrometer, bolometer, infrared imager,
micro-thermocouples, or the like. Ts is the feedback control
parameter according to this example. Ts is output by the sensor 72,
which may be located close to the article being irradiated, or may
optionally be disposed with the scanner and optics subsystem, the
laser head, or the like, for example. Ts from the sensor 72 is
provided to a temperature data logger 74, which receives and
records the Ts as it is being monitored. Ts is fed to the control
unit 76, which provides control signals to the laser source 78 to
control various parameters of the laser, including, but not limited
to, power and duration. In embodiments that use a SWIR heater, the
SWIR heater may be included in the feedback loop to provide
additional feedback control. As noted above, the laser source 78
may emit laser energy in a pulsed and/or continuous manner.
[0043] FIG. 8 is a flowchart illustrating a method of sealing
substrates using a laser according to certain example embodiments,
such as, for example, those illustrated in FIGS. 3 and 5 wherein a
glass based frit is used to form a seal between glass substrates.
According to certain example non-limiting embodiments, the glass
substrates to be sealed are provided S1. The substrates may be flat
substantially parallel plates, as illustrated for example, with
respect to the VIG embodiment illustrated in FIG. 3, or may be a
more complex geometric arrangement, such as, for example, the
component housing embodiment illustrated in FIG. 5. It will be
understood that the example embodiments disclosed herein are
equally applicable to any number of conceivable substrate
geometries regardless of complexity. Using the example illustrated
in FIG. 3 for convenience, the substrates 2, 3 are provided in step
S1. The sealing material, such as, for example, and without
limitation, a glass based frit, is then applied S3 to areas or
regions to be sealed, such as, for example, a peripheral edge of a
VIG window unit as illustrated in FIG. 3. The seal material
preferably includes an absorbing dye that may be tuned to the
characteristics of the laser being used to provide further
advantages. The seal material applied to the substrates in step S3
is subsequently dried S5 by, for example, heating at a relatively
low temperature, such as, for example, in a range of about
120.degree. C.-150.degree. C., to remove solvents from the vehicle.
Following drying S5, the frit is glazed S7 by heating the glass to
a higher temperature to glaze the frit and drive out the organic
binder material. The frit is then vitrified using laser irradiation
S9. During vitirfication S9, the frit heated using a controlled
localized laser to its melting point to form, for example, a
substantially continuous film made up of the glass network. As
noted above, the laser may be applied in a pulsed or continuous
manner, and is preferably controlled via a feedback loop based on
Ts. Additionally, it is noted that the laser may be applied in air
or in an inert atmosphere. The laser and its characteristics are
selected such that the laser energy substantially passes through
the glass substrate and is substantially absorbed by the seal
material, including, for example, and without limitation a seal
material that incorporates and absorbing dye. As also noted above,
it may be preferable to use a roughing pump or roller to keep the
substrates in place during vitrification and subsequent laser
induced bonding S11. Additionally, it may also be preferable to
provide a heat sink to control lateral heat flow to reduce cracking
due to large temperature gradients that may occur in the laser
process. After the frit is vitrified, the substrates are bonded S11
under application of laser energy by heating above the glass
melting temperature while the substrates are brought together. As
discussed above, optional use of a roughing pump or roller to keep
the substrates in place and to apply pressure is contemplated.
After the bonding process is completed, the completed seal may
optionally be annealed by applying laser energy thereto S13.
Annealing of the seal reduces stress in the seal and provides a
lower probability of failure of the seal by cracking or fracturing.
Further, as discussed above, the laser may be applied in any number
of different paths, including, but not limited to application of
dual laser beams on opposite sides of the article and rastering in
opposite directions, application of a single beam rastering in one
direction, pulsed application of the laser and/or continuous
application of the laser, or the like.
[0044] In embodiments using eutectic solders, such as, for example,
those illustrated in FIGS. 4 and 6 wherein a metallic solder based
sealing material is used to form a seal between glass substrates,
the method is similar to that illustrated in FIG. 8. However, in
eutectic bonding embodiments, the step of applying the sealing
material S3 includes application of an absorber film. The absorber
film, according to certain example non-limiting embodiments,
comprises a dual layer of silicon rich SiNx/Ni or SiNx/Cr. The
vitrification and bonding steps S9, S11 are accomplished by the
laser energy passing through the transparent substrate and being
substantially absorbed by the absorber film. The absorber film
heats up and melts the eutectic seal material, which then bonds the
substrates together as described above.
[0045] It is contemplated that any suitable laser may be used to
achieve the advantages attendant with the example embodiments
disclosed herein. For example, and without limitation, YVO4,
Ti:Sapphire, Cu vapor, excimer, Nd:YAG, CO.sub.2, ultraviolet,
infrared, harmonics of Nd:YAG lasers, or the like, at suitable
power levels, spot size and duration, may be used. According to
certain example embodiments, a 1090 nm YVO4, an 800 nm Ti:Sapphire
or 250 nm (second harmonics) Cu vapor laser, or the like may be
used. Moreover, as noted herein, application of the laser energy to
the seal material may be in a pulsed or continuous manner. For
example, and without limitation, the lasers may be pulsed using,
for example, Q-switching using repetitive rates, such as, for
example, in a range of about 1 KHz to several hundred KHz, and
preferably about 80 KHz. According to certain preferred
embodiments, a YVO4 lawer at 30W average power and pulsing at about
80 KHz focused on the frit area may be preferred. As noted above,
according to certain example embodiments, implementation of laser
sealing may be accomplished using two laser beams simultaneously
focused on opposite sides (e.g., top and bottom) of the glass
substrates being sealed together at a scan rate of about 100-150
mm/sec.
[0046] It is also noted that laser absorption or heat coupling by
the glass substrates may be avoided and/or reduced. According to
certain example embodiments, it is preferable to use glass that is
substantially transparent to the laser energy being applied so that
the glass does not substantially absorb laser energy or couple with
the laser to generate heat. For example, laser absorption by glass
may occur when using doped (e.g., Fe doped, where there is a
significant amount of iron in the glass) glass. Moreover, when
glass substrates are exposed to high-intensity beams, non-linear
effects may be induced, resulting in disadvantageous laser energy
absorption by the glass substrates. Additionally, using cladded
glass substrates in which the cladding materials are laser energy
absorbing may result in disadvantageous laser energy absorption,
and thus undesirable heating of the glass substrates. Accordingly,
use of such types of doped and/or cladded glass substrates should
be avoided.
[0047] Furthermore, surface absorption of laser energy may also
occur outside the transparent bands of the laser, such as, for
example, and without limitation at <300 nm for an excimer laser
and >2 um for CO.sub.2 lasers. These outside transparent bands
are typically used for surface modification or cutting and should
be avoided in laser sealing. Accordingly, according to certain
preferred embodiments, lasers having wavelengths in the range of
about 200 nm to just below 2000 nm (e.g., wavelengths to which the
glass substrates are substantially transparent), are preferred.
[0048] It is also noted that tempered glass is strong enough to
withstand large temperature variations, such as, for example, in
the range of about 200.degree. C. Also, as noted above, it is
typically not feasible to process tempered glass using typical bulk
heating processes because of the risk of losing temper. Therefore,
the laser sealing techniques disclosed herein are particularly well
suited to use with tempered glass substrates.
[0049] In certain embodiments of this invention, there is provided
a vacuum insulated glass (VIG) window unit, comprising: first and
second substantially parallel spaced apart substrates comprising
glass that are bonded together by an edge seal, said first and
second substrates and said edge seal defining a cavity having a
pressure lower than atmospheric pressure; and wherein said edge
seal comprises (i) a metallic or substantially metallic layer; and
(ii) an absorber film.
[0050] In the VIG window unit of the immediately preceding
paragraph, said absorber film may be at least partially diffused
into said metallic or substantially metallic layer.
[0051] In the VIG window unit of any of the preceding two
paragraphs, said edge seal may comprise first and second absorber
films, said first absorber film being located between the first
substrate and the metallic or substantially metallic layer, and the
second absorber film being located between the second substrate and
the metallic or substantially metallic layer.
[0052] In the VIG window unit of any of the preceding three
paragraphs, said absorber film(s) may comprise silicon and/or
silicon nitride.
[0053] In the VIG window unit of any of the preceding four
paragraphs, said metallic or substantially metallic layer may
comprise or consist essentially of solder.
[0054] In the VIG window unit of any of the preceding five
paragraphs, said absorber film may including a layer comprising
silicon rich silicon nitride characterized by Si.sub.zN.sub.x where
z/x is at least 0.78, more preferably at least 0.80.
[0055] In the VIG window unit of any of the preceding six
paragraphs, said absorber film(s) may comprise a first layer
comprising silicon nitride and a second layer comprising Ni and/or
Cr. In the absorber film, the layer comprising silicon nitride
(which may be doped with Al or the like) is located between the
glass substrate and the layer comprising Ni and/or Cr. Thus, for a
given absorber film, the layer comprising Ni and/or Cr is located
closer to the metallic or substantially metallic layer than is the
silicon nitride.
[0056] In certain example embodiments of this invention, there is
provided a method of making a vacuum insulated glass (VIG) window
unit, the method comprising: providing a first substrate; applying
a seal material to an area of the first substrate to be sealed;
forming a seal by at least (a) vitrifying the seal material using
laser irradiation, the laser irradiation exposing the seal material
but not being directed toward a majority of the first substrate,
and (b) bonding the first substrate to a second substrate by
continuing to irradiate the vitrified seal material with laser
irradiation to melt the seal material; and evacuating a cavity
formed between the first and second substrates and defined by the
seal to a pressure lower than atmospheric pressure.
[0057] In the method of the immediately preceding paragraph, said
first and second substrates may comprise glass.
[0058] In the method of any of the preceding two paragraphs, said
seal material may comprise a glass based frit. Said glass based
frit may include an absorbing dye that absorbs laser energy.
[0059] In the method of any of the preceding three paragraphs, the
method may include applying pressure to one or both of the
substrates during at least the bonding step. The applying of
pressure may include pumping out the cavity and/or applying
pressure via at least one roller.
[0060] In the method of any of the preceding four paragraphs,
application of said laser irradiation may be controlled via a
feedback loop. The feedback loop may include information regarding
a temperature in an area of the laser irradiation.
[0061] In the method of any of the preceding five paragraphs, the
laser irradiation may be from one or more of an excimer laser, a
CO.sub.2 laser, an Nd:YAG laser, and a harmonic of an Nd:YAG
laser.
[0062] In the method of any of the preceding six paragraphs, the
laser irradiation may be pulsed and/or continuous.
[0063] In the method of any of the preceding seven paragraphs, the
laser irradiation may be performed by dual beams directed to
opposite sides of the VIG window unit, said dual beams rastering in
opposite directions. The beams may raster at a rate in the range of
from about 100-150 mm/sec. Alternatively, the laser irradiation may
be performed by a single beam rastering in a single direction.
[0064] In the method of any of the preceding eight paragraphs, said
seal material may comprise a layer comprising metallic or
substantially metallic solder. An absorber film may be interposed
between the layer comprising solder and at least one of the
substrates. Laser energy from said laser irradiation is absorbed by
said absorber film that in turn heats and helps melts seal material
in the layer comprising solder. The absorber film may comprise one
or more of: (i) a layer comprising silicon nitride, (ii) Si-rich
silicon nitride characterized by Si.sub.zN.sub.x where z/x is at
least 0.78; and (iii) a layer comprising silicon nitride and a
layer comprising Ni and/or Cr. For example, in the dual-layer
embodiment including a silicon nitride inclusive layer and a layer
of or including Ni and/or Cr, the silicon nitride inclusive layer
may or may not be Si-rich.
[0065] In the method of any of the preceding nine paragraphs, after
said bonding, there may be performed annealing the seal by laser
irradiation.
[0066] In the method of any of the preceding ten paragraphs,
application of the laser to the seal material may be performed by
the laser passing substantially through the first and/or second
substrate and irradiating the seal material, or alternatively
application of the laser to the seal material may be performed from
a side so that the laser does not pass through either the first or
second substrate of the VIG unit to irradiate the seal
material.
[0067] In the method of any of the preceding eleven paragraphs, the
vitrifying and/or bonding steps may be performed (i) in air and/or
in an inert atmosphere, and/or (ii) at approximately room
temperature.
[0068] In the method of any of the preceding twelve paragraphs, the
method may further include depositing a metal oxide layer on the
first and/or second glass substrate(s) prior to applying said seal
material.
[0069] In certain example embodiments of this invention, there is
provided a method of making an article (e.g., electronic device,
VIG unit, or the like) including a sealed cavity formed between
substrates, the method comprising: providing first and second
substrates comprising glass; applying a sealing material to at
least one of the substrates; and forming a seal by irradiating the
sealing material with a laser, wherein said cavity is defined by
geometries of the substrates and the seal.
[0070] In the method of the immediately preceding paragraph, there
may also be a step of evacuating the cavity to a pressure lower
than atmospheric pressure.
[0071] In the method of any of the preceding two paragraphs, a
temperature sensitive component may be disposed in said cavity. The
temperature sensitive component may be at least one of a
semiconductor chip, a sensor, an optical component, organic light
emitting layers, and/or an OLED.
[0072] In the method of any of the preceding three paragraphs, said
seal may be a hermetic seal.
[0073] In the method of any of the preceding four paragraphs, said
seal material may comprise a glass based frit, or a layer
comprising metallic or substantially metallic solder.
[0074] In the method of any of the preceding five paragraphs, there
may also be a step of annealing the seal via laser irradiation.
[0075] In the method of any of the preceding six paragraphs, there
may also be a step of providing a thermally conductive heat sink in
thermal contact with at least one of the substrates to control
lateral heat flow during laser irradiation.
[0076] In the method of any of the preceding seven paragraphs,
application of said laser irradiation may be controlled via a
feedback loop. The feedback loop may (a) include information
regarding a temperature in an area of the laser irradiation, and/or
(b) be used to control a power and duration of said laser
irradiation.
[0077] In the method of any of the preceding paragraphs, there may
also be a step of providing a thermally conductive heat sink in
thermal contact with at least one of the substrates to control
lateral heat flow during laser irradiation.
[0078] While certain example embodiments have been described and
disclosed herein, it will be understood that the embodiments
described herein are intended to be illustrative, not limiting, and
that those skilled in the art will understand that various
modifications may be made without departing from the true spirit
and full scope of the claims appended hereto.
* * * * *