Two-stage hermetic seal and its manufacturing method

Abstract

The vacuum glazing assembly includes first and second spaced-apart non-metallic substrates connected together by a sealing element to form an evacuable interior space therebetween. The sealing element is formed by joining a metallic bridge element to at least one substrate by indirect welding to form a first-stage seal and a second-stage seal at least partially contacting the first-stage seal to form a second-stage seal. The sealing element is configured to seal the interior space from the surrounding environment, with both the first-stage seal and the second-stage seal contributing to the sealing performance of the sealing element.

Description

[Technical field]

[0001] [Statement Regarding Federally Sponsored Research or Study] [History] This invention was made with Government support under SBIR Support Agreement DE-SC0017841 awarded by the U.S. Department of Energy. The Government has certain rights in this invention.

[0002] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims priority to co-pending U.S. Provisional Patent Application No. 63 / 038,102, filed June 11, 2020, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a process for making a two-stage hermetic seal element for an envelope having an interior region isolated from the environment. [Background technology]

[0004] Many existing vacuum glazing assemblies (e.g., Vacuum Insulated Glass (VIG) assemblies) include two or more glass panes (e.g., panes) separated from each other by a space. Temperature differences between the assemblies can significantly affect the structure of the assembly and can potentially cause the assembly to fail. For example, when a vacuum glazing assembly is installed on the exterior wall of a temperature-controlled and / or insulated building, the temperature of the exterior panes typically approaches the outside air temperature (which contracts when exposed to cold and expands when exposed to heat). The interior panes typically remain at a relatively constant temperature that matches the interior air temperature. The movement of the exterior panes (i.e., contraction or expansion) relative to the interior panes is known as "differential pane movement," and too much differential pane movement can cause the vacuum glazing assembly to fail due to cracking, seal failure, or other mechanisms. Summary of the Invention

[0005] One type of hermetic seal element that can be used to seal between the glass panes of a vacuum glazing assembly includes a metal bridge element (e.g., a metal foil) that is welded to a metal adhesive layer deposited on the glass panes. An example of such a hermetic seal element is described in U.S. Provisional Application No. 62 / 936,140, ​​filed November 15, 2019, the entire contents of which are incorporated herein by reference.

[0006] Hermetic seal elements can fail (i.e., leak) through a variety of different mechanisms, including micro-leak paths along the interface between the metal bridge element and the glass, defects in the metal bridge element (e.g., scratches, wrinkles, microstructural damage, perforations through or along the edges of the weld, the joint between the individual segments that make up the metal bridge element, etc.), defects in the glass (e.g., scratches), defects due to uncontrolled process parameter variations (e.g., due to "tramp" metal deposited on the sonotrode), and misalignment of the weld segments where they overlap. While these failure mechanisms can be minimized using tightly controlled manufacturing processes, there is a need for a seal configuration that can provide a more reliable hermeticity in a cost-effective manner.

[0007] In one aspect, the present invention provides an evacuated glazing assembly having first and second spaced apart substrates connected together by a sealing element to define an evacuable interior space therebetween. The sealing element is formed by cold welding a metallic bridge element to at least one of the substrates to form a first stage seal and at least partially contacting the first stage seal to form a second stage seal. The sealing element is hermetic in that it is configured to effectively isolate the interior space from the surrounding environment.

[0008] In another aspect, the present invention provides an evacuated glazing assembly including a first substrate, a second substrate spaced apart from the first substrate to define an interior space therebetween, and a sealing element disposed between the first substrate and the second substrate to hermetically isolate the interior space from an ambient environment, the sealing element including a first stage seal formed by a cold weld bond between a joined metal bridge element and the first substrate, and a second stage seal in at least partial contact with the first stage seal.

[0009] In another aspect, the invention provides a method of forming a seal element for hermetically sealing between two substrates of an evacuated glass assembly, the method comprising bonding a metallic bridge element to each of the two substrates to form a first hermetic stage seal, providing a seal material in at least partial contact with the first stage hermetic seal, and heating the seal material to form a second stage hermetic seal.

[0010] Other features and aspects of the present invention will become apparent from the following description and drawings. [Brief description of the drawings]

[0011] [Figure 1] 1 is a partial cross-sectional view of an exemplary evacuated glazing assembly including an interior space and a sealing element isolating the interior space from the surrounding environment. [Diagram 2] 2 is a partial cross-sectional view showing the first and second stages of the seal element of FIG. 1 bonded to a substrate. [Diagram 3] 11 is a partial cross-sectional view showing the first and second stages of a sealing element according to another embodiment. [Figure 4] 11 is a partial cross-sectional view showing the first and second stages of a sealing element according to another embodiment. [Diagram 5] 11 is a partial cross-sectional view showing the first and second stages of a sealing element according to another embodiment. [Figure 6] 11 is a partial cross-sectional view showing the first and second stages of a sealing element according to another embodiment. [Figure 7]2 is a partial cross-sectional view of the evacuated glass assembly of FIG. 1 including a sealing element according to another embodiment. [Figure 8] 2 is a partial cross-sectional view of the evacuated glass assembly of FIG. 1 including a sealing element according to another embodiment. [Figure 9] 1 is a photograph showing a first stage and a second stage of a sealing element embodying an aspect of the present disclosure. [Figure 10] FIG. 2 is a top view showing a ribbon of foil bonded to a substrate. [Figure 11] 1 is a flow chart illustrating a sealing process according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Before describing any embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components illustrated in the following description or above the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways without departing significantly from the spirit of the invention.

[0013] As used herein, the term "glass pane" refers to a glass element intended for use as a wall element or substrate in a hermetically sealed flat enclosure assembly.

[0014] "Differential pane movement" refers to the relative pane movement between two adjacent panes that occurs when the temperature of one pane changes relative to the temperature of the other pane, or may refer to relative pane movement that occurs under mechanical or other influences (e.g., shock during handling or use).

[0015] "Hermeticity" or "level of hermeticity" refers to a measure of the maximum leak rate a seal is capable of, e.g., standard cubic centimeters of helium per second per centimeter of seal length (sccs / cm) or an equivalent measurement. Generally, the higher the hermeticity, the lower the leak rate and vice versa.

[0016] "Hermetic" refers to a seal capable of achieving a degree of hermeticity suitable or specified for the application. It should be recognized that each stage of a multi-stage seal, such as the stage seals described and illustrated herein, may be described as hermetic without inferring that the hermeticity of each stage is the same.

[0017] The term "highly-malleable" refers to an object or material having a yield stress of 10,000 psi or less (e.g., 5,500 or less).

[0018] The term "solid-state" with respect to welding or coating refers to a joining process that does not involve melting of the materials being joined.

[0019] The term "cold weld" refers to a solid state process for joining two or more parts.

[0020] The term "sonotrode" refers to a vibrating tool that transmits a translational motion to an assembly of substrates being welded by an ultrasonic bonding apparatus.

[0021] The term "mechtrode" or "mechatrode" means a mandrel or other end effector tool used for solid-state joining or coating of materials by relative motion under pressure, usually in processes that do not involve ultrasonic vibration.

[0022] The term "inboard" refers to the location of a first feature relative to a second feature on an assembly having a generally planar feature, the location of the first feature on the side of the second feature that is closer to the center of the generally planar feature.

[0023] The term "outboard" refers to the location of a first feature relative to a second feature on an assembly having a generally planar feature, the location of the first feature on the side of the second feature that is away from the center of the generally planar feature.

[0024] The term "bridge element" means an element that is bonded to a substrate and forms part of a hermetic seal element that separates an interior space from the environment.

[0025] FIG. 1 illustrates a portion of an exemplary evacuated glazing assembly 10 (e.g., a window assembly configured to be attached to an exterior wall of a building) including a first substrate 14 (e.g., a first glass pane) and a second substrate 16 (e.g., a second glass pane) spaced apart from the first substrate 14, which define an interior space 18 (also referred to as an evacuable gap or interior region) that is sealed and isolated from the environment surrounding the evacuated glazing assembly 10. One or more spacers 20 formed of an incompressible or substantially incompressible material (e.g., composite, plastic, glass, metal, etc.) can be disposed in the interior space 18 between the substrates 14, 16 to maintain a constant gap between the substrates 14, 16. The substrates 14, 16 in the illustrated embodiment are non-metallic (e.g., glass, such as annealed glass or tempered glass). In other embodiments, one or both of the substrates 14, 16 may be metallic. A sealing element 22 is attached to each of the substrates 14, 16 to seal the interior space 18 from the surrounding environment.

[0026] 1, the sealing element 22 includes a metal bridge element 30 and a sealant 34. The bridge element 30 can be formed of one or more layers of metal foil (e.g., aluminum foil). In the illustrated embodiment, the bridge element 30 is formed from two segments 30a, 30b, each of which is directly attached to the respective substrates 14, 16 via a solid-state welding process (e.g., a friction welding process using a sonotrode) to form a weld 36. In the illustrated embodiment, the two segments 30a, 30b are connected to each other by a connecting weld 42 (e.g., fusion welding such as laser welding, MicroTIG welding, resistance welding, etc., or the weld 42 can include a solid-state weld). In other embodiments, the segments 30a, 30b of the bridge element 30 can be integrally formed from a single piece of material, and the segments 30a, 30b can be connected to each other in other ways.

[0027] Referring to FIG. 2, the bridge element 30 is attached to the substrate 14 by a weld 36. The bridge element 30 extends across the interior space 18 along its peripheral boundary (i.e., between the substrates 14, 16) to hermetically seal the interior space 18. The weld 36 defines a first stage seal 38 (also called a first stage seal or a main stage seal) of the sealing element 22. The first stage seal 38 is hermetic and also provides a structural connection between the bridge element 30 and the substrate 14. That is, the first stage seal 38 is configured to resist shear forces due to thermal expansion or movement of the different glass sheets. In some embodiments, the structural connection between the bridge element 30 and the substrate 14 defined by the first stage seal 38 has a shear strength greater than the tensile strength of the bridge element 30 itself.

[0028] 3, in some embodiments, the seal element 22 further includes an intermediate layer 37, which may be made of a metal (e.g., aluminum) or an inorganic material. In particular, the intermediate layer 37 is formed as a coating that is deposited or otherwise disposed on the edge (e.g., around the outer edge) of the substrate 14. For example, in some embodiments, the intermediate layer 37 may be deposited on the substrate 14 using a mechatrode. The bridge element 30 is attached to the substrate 14 on the intermediate layer 37 and forms a weld 36 (e.g., by a solid-state welding process, such as a friction welding process using a sonotrode), thereby forming the first stage seal 38. The intermediate layer 37 may improve the mechanical strength and / or hermeticity of the first stage seal 38.

[0029] 2-3, the sealant 34 is at least partially in contact with the first stage seal 38 to define a second stage seal 40 (also referred to as a second stage seal or a next stage seal) of the seal element 22. The sealant 34 is comprised of a solder glass, a metal solder, or other material suitable for bonding to the bridge element 30 and / or the substrate 14 and forming a seal of the required hermeticity. Typically, the hermeticity of a first stage seal 38 that includes a defect is less hermetic (i.e., leaks more) than the hermeticity of a corresponding second stage seal 40. In contrast, the hermeticity of a first stage seal 38 that is free of defects is typically similar to the hermeticity of a corresponding second stage seal 40. Correspondingly, the hermeticity of the bonded two-stage seal element 22 is comparable to the hermeticity of the second stage seal 40.

[0030] In some embodiments, the seal material 34 may be an organic seal material. In such embodiments, the organic seal material is desirably an organic seal material with low outgassing and low permeability. Organic seal materials have not previously been able to provide long-lasting hermetic seal performance in passive (i.e., not actively pumped) vacuum glass assemblies. However, the two-stage seal element 22 allows for the use of organic seal materials for the second stage seal element 40 because the hermetic first stage seal 38 minimizes exposure of the second stage seal 40 to the outside environment. That is, the first stage seal 38 reduces potential gas permeation through the second stage seal 40, thereby allowing a greater variety of materials to be used for the second stage seal 40 without compromising the overall hermeticity of the seal element 22.

[0031] In the illustrated embodiment, the sealant 34 covers the entire first stage seal 38. In other embodiments, the sealant 34 may be applied to contact only a portion of the first stage seal 38 (e.g., the second stage seal 40 may abut the inner edge of the first stage seal 38 and cover the interface bond between the first stage seal 38 and the substrate 14). The sealant 34 may be adhered to one or both of the substrate 14 and the bridge element 30.

[0032] The sealant 34 has a melting and / or curing temperature that is lower than the melting temperatures of the substrates 14, 16, and other portions of the evacuated glass assembly 10. In some embodiments, a heating device is used to heat at least a portion of the article 10 including the sealant 34, thereby melting and / or curing the sealant 34 to form a bond with the substrates 14 and the bridge element 30. In some embodiments, a heating device (e.g., an oven) can be used to heat the entire assembly 10 to melt and / or cure the sealant 34, thereby forming the second stage seal 40.

[0033] 2, because the first stage seal 38 is located outside the second stage seal 40, the structural connection formed by the welds 36 between the bridge element 30 and the substrates 14, 16 bears substantially all of the shear stress that may be applied to the seal element 22. That is, when a force F is applied to the seal element 22 (e.g., due to uneven thermal expansion and / or differential glass sheet movement), substantially all of the shear stress is borne by the high strength welds 36 of the first stage seal 38, and not by the second stage seal 40. Because the second stage seal 40 is shielded from mechanical stress by the first stage seal 38, the hermeticity of the second stage seal 40 may be maintained for a longer period of time. However, in other embodiments, the second stage seal 40 may be located at least partially outside the first stage seal 38.

[0034] 4-6 show various configurations of the second stage seal 40. For example, the second stage seal 40 can be formed by melting the inner end of the bridge element 30 (FIG. 4) and / or the middle portion of the bridge element 30 (FIG. 5) in the area of ​​the first stage seal 38. In such an embodiment, the second stage seal 40 can be formed by laser welding. With reference to FIG. 6, the second stage seal 40 can be formed by cold welding the inner end of the bridge element 30 and / or the middle portion of the bridge element 30 in the area of ​​the first stage seal. The embodiments of the second stage seal 40 shown in FIGS. 4-6 allow the second stage seal 40 to be formed either before or after the first stage seal 38, providing additional flexibility in the manufacturing process.

[0035] Although only the substrate 14 is shown in Figures 2-6, the sealing element 22 includes substantially identical first and second stage seals and steps at the interface between the bridge element 30 and the second substrate 16 (Figure 1). Returning to Figure 1, a connection weld 42 can be provided on the outer extent of the bridge element 30 to bond the segments 30a, 30b of the bridge element 30 together. Referring to Figure 7, in another embodiment of a similar vacuum glass assembly 10A, the connection weld 42 can be replaced by a connection material 43 that joins the segments 30a, 30b of the bridge element 30. The connection material 43 can be, for example, a metal solder or a solder glass material. Using the connection material 43 instead of the connection weld 42 can result in lower heat input to the sealing element 22 and the substrates 14, 16 during application. In yet another embodiment, the connection material 43 can be an adhesive.

[0036] Referring to Figure 8, in another embodiment of a similar evacuated glazing assembly 10B, the bridge element 30 is formed from a single generally planar segment. As such, the connecting welds 42 and connecting material 43 shown in the embodiments of Figures 1 and 7, respectively, can be omitted. In the illustrated embodiment, the peripheral edges of the substrates 14, 16 are offset such that the outer edge of the first substrate 14 is away from the outer edge of the second substrate 16. The offset arrangement provides access for forming the outer step seals 38, 40.

[0037] FIG. 11 illustrates an exemplary process having four major steps for fabricating a two-stage seal element, such as the embodiment of seal element 22 described above with reference to FIGS. 1-8, and positioning and attaching seal element 22 to substrates 14, 16. It will be understood that FIG. 11 encompasses a general process, and that additional steps may be incorporated into the process to facilitate formation of seal element 22, as well as positioning and attaching seal element 22 onto substrates 14, 16. The general process includes i) providing a non-metallic substrate (step S100), ii) attaching a metallic bridge element to the substrate to form a first stage seal (step S104), iii) applying a seal material in at least partial contact with the first stage seal to form a second stage seal (step S108), and iv) further processing (step S112). These major steps may be performed sequentially or one or more steps may be performed simultaneously.

[0038] The first major step (step S100) involves preparing the substrate 14, 16, which includes cleaning the substrate 14, 16 (e.g., by plasma cleaning in some embodiments) and / or providing an intermediate layer (e.g., intermediate layer 37 in FIG. 3) to the substrate 14, 16. In some embodiments, the intermediate layer 37 is provided to the substrate 14, 16 using a process or method (i.e., oven-free, vacuum-chamber-free process) that does not include an oven for heating the substrate 14, 16 and does not use a vacuum chamber (i.e., oven-free, vacuum-chamber-free process). For example, in some embodiments, a malleable metal (e.g., aluminum) is applied to the non-metallic substrate using friction surfacing. Friction surfacing involves pressing a metal consumable (e.g., a mechatrode) made of a malleable metal against the surface of the non-metallic substrate and moving (i.e., moving relative to one another) the metal consumable and / or the substrate to deposit or transfer the malleable metal to the surface, thereby forming a metal layer that is part of the sealing element. In some constructions, a stable gas (eg, argon) may be used to exclude oxygen during the friction surfacing process.

[0039] In a second major step (step S104), the metallic bridge element 30 is attached to the substrates 14, 16 by a cold welding process, either directly or additionally via an intermediate layer 37. In particular, the metallic bridge element 30 can be welded using a sonotrode of an ultrasonic seam welder to form a weld 36 that defines a first stage seal 38.

[0040] The third major step (step S108) is to apply the sealant 34 at least partially in contact with the first stage seal 38. In some embodiments, the sealant 34 is provided as a powder (e.g., powdered solder glass) that is dispensed into the first stage seal 38. In some embodiments, the sealant 34 can be provided as a gel or the like. In yet other embodiments (e.g., FIGS. 4-6), the sealant 34 can be part of the metal bridge element 30 itself, and is melted or deformed by laser welding, cold welding, or other similar process to form the second stage seal 40.

[0041] Finally, in the fifth major step (step S112), further processing may occur (e.g., using an oven or other heat source) such as to melt and / or cure the sealant 34 to form the second stage seal 40. Additional processing may include evacuating the interior space 18. Further processing of the assembly can take many forms, such as igniting a getter in the interior space and possibly a secondary welding or sealing step that may be required so that the interior space can be evacuated or permanently sealed.

[0042] The two-stage seal element 22 according to the embodiments described and illustrated herein provides a number of advantages over a single stage seal element. For example, the second stage seal 40 provides a redundant or second hermetic seal that can maintain the integrity of the seal element 22 in the event that the hermeticity of the first stage seal 38 is compromised through any of a variety of different mechanisms including micro-leaks, perforations through or along the welded edge, defects (e.g., scratches, wrinkles, etc.) in the metal bridge element 30, defects (e.g., scratches) and misalignments in the substrates 14, 16. As such, the first stage seal 38 can be manufactured in a less expensive manner (e.g., with lower manufacturing tolerances, less quality control testing, etc.) while still contributing to an effective overall hermetic performance. In some embodiments, the two-stage seal element 22 can also provide a longer service life for the sealed product. It should be appreciated that the second stage seal 40 can also repair defects 50 that may be present in the first stage seal 38 (i.e., by filling voids, micro-leaks, etc.) (i.e., eliminating leakage), as shown in FIG. 9.

[0043] In some embodiments, the second stage seal 40 may be at least partially inside the first stage seal 38 such that gases that may be trapped between them or at the interface of the bridge element 30 and the substrates 14, 16 cannot communicate with the evacuated interior volume 18. This has the advantage of allowing for faster pump-down of the interior volume 18. Additionally, the use of solder glass as the sealant 34 allows the second stage seal 40 to dissolve adjacent portions of certain commonly used coatings (such as low-emissivity coatings) on the substrates 14, 16, providing a barrier against the progression of corrosion that may occur along the coating, thereby protecting the evacuated interior volume 18.

[0044] An important advantage of the dual stage seal element 22 according to the embodiment described and illustrated herein is that the metallic bridge element 30 is in both physical and adhesive contact with the non-metallic substrate, thereby improving the sealing performance.

[0045] In some embodiments, the dual seal element 22 can provide a convenient chamber to contain getter ribbons or getter particles that remove residual gas from the evacuated interior space. Such a chamber can inhibit migration of getter material into the visible region of the product after the getter has reacted.

[0046] In some embodiments (e.g., FIG. 1 ), the second stage seal 40 maintains a gap between opposing portions of the metallic bridge element 30, which may inhibit heat transfer between the two substrates 14, 16 that could occur by conduction through the metallic bridge element 30.

[0047] In some embodiments, the two-stage seal element 22 advantageously allows for the use of ribbon segments of foil (as shown in FIG. 10 ) to form the metal bridge element 30, rather than using a full foil that is then trimmed to the inside of the seal element 22. Because the ribbons of foil are connected at a comber or other transition using weld joints 54, the first stage seal 38 is more likely to develop defects that cause localized loss of tightness in the area of ​​the weld joints 54. The second stage seal 40 can seal such defects to improve the overall tightness of the seal element.

[0048] 1-8 show some exemplary products that include a two-stage sealing element, it will be understood that other products can also include the sealing element (e.g., flat panel displays), and therefore the invention described and claimed herein should not be construed to include only window assemblies.

[0049] It is understood that the present invention may be embodied in other specific forms or incorporate combinations of the embodiments described herein without departing from the spirit or characteristics of the present invention. While specific embodiments have been illustrated and described, other changes may be made without significantly departing from the spirit of the invention.

[0050] Various features of the invention are set forth in the following claims.

Claims

1. 1. A vacuum glass assembly having first and second spaced apart substrates interconnected by a sealing element to define an evacuable interior space therebetween, The sealing element comprises: a first stage seal defined by a cold weld that is a joint between a metallic bridge element and the at least one substrate, the cold weld being a joint formed without the application of heat to the metallic bridge element and the at least one substrate; a second stage seal at least partially in contact with the first stage seal and disposed at least laterally from the first stage seal and partially offset inwardly of the first stage seal so as to be at least partially bonded directly to one of the first and second substrates on which the first stage seal is provided; the second stage seal is configured to hermetically seal the first stage seal; The sealing element is configured to hermetically isolate the interior space from a surrounding environment.

2. 10. The vacuum glazing assembly of claim 1, wherein the second stage seal comprises a sealant in at least partial contact with the first stage seal.

3. The evacuated glass assembly of claim 2 , wherein the seal material comprises solder glass.

4. The evacuated glazing assembly of claim 2 , wherein the seal material comprises a metal solder.

5. The vacuum glazing assembly of claim 2 , wherein the sealant comprises an organic sealant.

6. 3. The evacuated glazing assembly of claim 2, wherein said second stage seal is a seal defined at least in part by heating said evacuated glazing assembly.

7. 10. The vacuum glazing assembly of claim 1, wherein the second stage seal is a seal defined at least in part as a weld welded to at least a portion of the first stage seal.

8. 10. The evacuated glazing assembly of claim 1, wherein said first stage seal is a seal defined by contacting a vibrating sonotrode against a metallic bridge element.

9. 2. The evacuated glazing assembly of claim 1, wherein the metallic bridge element includes a first segment bonded to the first substrate and a second segment bonded to the second substrate.

10. 10. The vacuum glazing assembly of claim 9, wherein the first segment is welded to the second segment.

11. 10. The vacuum glazing assembly of claim 9, wherein the first segment is adhered to the second segment by a connecting material.

Images