MOV / GDT devices with low voltage gas discharge characteristics.

Abstract

A gas discharge tube (GDT) based device having low voltage gas discharge characteristics is provided. A plurality of electrical devices may be manufactured that includes a number of metal oxide varistors (MOVs), each MOV including an external electrode on a first side of a metal oxide layer and an internal electrode on a second side of the metal oxide layer, and a layer of sealing material located at or near the periphery of the second side of the metal oxide layer of each MOV. A stack may be formed having one or more sets, each set including two MOVs having opposing second faces such that the respective layers of sealing material engage each other, and the engaged layers of sealing material may be fused to form a seal between the two internal electrodes of each set that forms a sealed chamber for a gas discharge tube (GDT), the seal having a thickness dimension approximately the same as a selected gap dimension between the two internal electrodes.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Application No. 63 / 294,795, filed December 29, 2021, entitled “MOV / GDT DEVICE HAVING LOW VOLTAGE GAS DISCHARGE PROPERTY,” the disclosure of which is expressly incorporated herein by reference in its entirety.

[0002] The present disclosure relates to gas discharge tube (GDT) based devices having low voltage gas discharge characteristics. [Background technology]

[0003] A gas discharge tube (GDT) is a device that has a gas between two electrodes in a sealed chamber. When a trigger condition occurs between the electrodes, the gas ionizes and allows electricity to flow between the electrodes.

[0004] Metal oxide varistors (MOVs) contain a metal oxide material, such as zinc oxide, mounted between two electrodes. Under normal conditions, MOVs are non-conductive, but become conductive when a voltage exceeds their rated voltage.

[0005] It should be noted that typical MOVs can themselves degrade due to, for example, constant AC line voltage stress. Such stress may be due to surge history, time, temperature, or a combination thereof, leading to increased leakage current and / or reduced effectiveness of the MOV. Increased leakage current can adversely affect the energy efficiency rating of the MOV due to increased standby current. Also, sustained increases in AC voltage can cause the MOV to overheat, leading to failure and / or fire.

[0006] When an MOV is combined with a GDT, the result is a GDT / MOV device in which the GDT and MOV are electrically connected in series. When operating under normal conditions, the line voltage develops primarily across the GDT, thereby effectively disconnecting the MOV from the conductors. During a surge event, the GDT switches on relatively quickly, connecting the MOV across the conductors and clamping the surge voltage to an acceptable level. Once the surge event has passed, the GDT switches off again, allowing the MOV to be disconnected as before.

[0007] Thus, GDT / MOV devices can provide many advantageous features. For example, reduced leakage current in the MOV portion can be achieved, thereby extending the operating life of the device. In other examples, GDT / MOV devices can be configured to provide voltage increase tolerance or reduced sensitivity to such voltage increases without sacrificing clamping voltage performance. Summary of the Invention [Means for solving the problem]

[0008] In some embodiments, the disclosure relates to a method for manufacturing a plurality of electrical devices. The method includes forming or providing a number of metal oxide varistors (MOVs), each MOV including an external electrode on a first side of the metal oxide layer and an internal electrode on a second side of the metal oxide layer, and forming a layer of sealing material at or near the periphery of the second side of the metal oxide layer of each MOV. The method further includes forming a stack having one or more sets, each set including two MOVs having opposing second sides such that the respective layers of sealing material engage each other. The method further includes performing a sealing step to fuse the engaged layers of sealing material to form a seal between the two internal electrodes of each set to form a sealed chamber of a gas discharge tube (GDT). The sealing step is performed such that the seal has a thickness dimension approximately the same as a selected gap dimension between the two internal electrodes.

[0009] In some embodiments, the layer of sealing material is formed such that the thickness of the layer of sealing material in one of the two MOVs in each set is substantially the same as the thickness of the layer of sealing material in the other of the two MOVs in that set.

[0010] In some embodiments, the sealing material may include glass or other high temperature insulating sealing material.

[0011] In some embodiments, forming or providing the MOVs results in the outer electrode of each MOV being substantially flat, hi some embodiments, forming or providing the MOVs results in the outer electrode of each MOV having a flared edge configuration.

[0012] In some embodiments, the stack comprises a plurality of sets.

[0013] In some embodiments, performing the sealing step includes supplying a desired gas to the stack such that the desired gas is introduced into the unsealed chambers of each set of MOVs. The desired gas may include an inert gas and / or an active gas. In some embodiments, the desired gas may include neon or argon. In some embodiments, the desired gas may include neon at approximately 500 Torr.

[0014] In some embodiments, the method may further include forming an emissive coating on each internal electrode. The emissive coating may comprise a glass or an active coating. In some embodiments, the emissive coating may comprise an active coating. In some embodiments, the active coating may comprise an alkali metal or an alkali-based compound.

[0015] In some embodiments, the gap size between the two inner electrodes, the emissive coating, and the desired gas may be selected to provide a breakdown voltage for the GDT of less than 120 V. In some embodiments, the breakdown voltage of the GDT may be less than 100 V.

[0016] In some embodiments, the selected gap dimension between the two internal electrodes may be less than 500 μm. In some embodiments, the selected gap dimension between the two internal electrodes may be in the range between 250 μm and 300 μm. In some embodiments, the selected gap dimension between the two internal electrodes may be approximately 280 μm.

[0017] In some embodiments, the seal may include a laterally extending portion formed over a portion of either or both of the internal electrodes to increase the length of the leak path between the internal electrodes, hi some embodiments, the laterally extending portion may be formed by the sealing process and / or by an extension of the sealing material formed prior to the sealing process.

[0018] In some embodiments, the sealing step may include applying a selected force to the stack to effect a thickness dimension of each set of seals.

[0019] In some embodiments, the present disclosure relates to a system for manufacturing a plurality of electrical devices. The system includes a metal oxide varistor (MOV) fabrication apparatus configured to form or provide a number of MOVs, each MOV including an external electrode on a first side of a metal oxide layer and an internal electrode on a second side of the metal oxide layer. The system further includes a gas discharge tube (GDT) fabrication apparatus configured to form a layer of sealing material at or near the periphery of the second side of the metal oxide layer of each MOV. The GDT fabrication apparatus is further configured to form a stack having one or more sets, each set including two MOVs having opposing second sides such that the respective layers of sealing material engage each other. The GDT fabrication apparatus is further configured to perform a sealing process to fuse the engaged layers of sealing material to form a seal between the two internal electrodes of each set to form a sealed chamber of the gas discharge tube (GDT), the seal having a thickness dimension approximately equal to a selected gap dimension between the two internal electrodes.

[0020] In some embodiments, the present disclosure relates to an electrical device including first and second metal oxide varistors (MOVs), each MOV including an external electrode on a first side of the respective metal oxide layer and an internal electrode on a second side of the metal oxide layer, the electrical device further including a seal located at or near the outer periphery of the second side of the metal oxide layer of each of the first and second MOVs, thereby forming a sealed chamber having a desired gas therein of a gas discharge tube (GDT) between the two internal electrodes of the first and second MOVs, the seal having a thickness dimension approximately the same as a selected gap dimension between the two internal electrodes.

[0021] In some embodiments, the seal comprises glass or other high temperature insulating sealing material.

[0022] In some embodiments, the outer electrode of each MOV may be substantially flat or have a flared edge configuration.

[0023] In some embodiments, the desired gas may include an inert gas and / or an active gas. In some embodiments, the desired gas may include neon or argon. In some embodiments, the desired gas may include neon at approximately 500 Torr.

[0024] In some embodiments, the electrical device may further include an emissive coating on each internal electrode, hi some embodiments, the emissive coating may include a glass or active coating.

[0025] In some embodiments, the emissive coating may include an active coating, hi some embodiments, the active coating may include an alkali metal or alkali-based compound.

[0026] In some embodiments, the gap size between the two inner electrodes, the emissive coating, and the desired gas may be selected to provide a breakdown voltage for the GDT of less than 120 V. The breakdown voltage of the GDT may be less than 100 V.

[0027] In some embodiments, the selected gap dimension between the two internal electrodes may be less than 500 μm. In some embodiments, the selected gap dimension between the two internal electrodes may be in the range between 250 μm and 300 μm. In some embodiments, the selected gap dimension between the two internal electrodes may be, for example, approximately 280 μm.

[0028] In some aspects, the seal may include a laterally extending portion formed over a portion of either or both of the internal electrodes to increase the length of the leak path between the internal electrodes.

[0029] For purposes of summarizing the disclosure, certain aspects, advantages, and novel features of the invention are described herein. It is to be understood that not all such advantages need to be achieved in accordance with any particular embodiment of the invention. Thus, the invention can be embodied or performed to achieve or optimize one advantage or group of advantages as taught herein, without necessarily achieving other advantages as may be taught or suggested herein. [Brief description of the drawings]

[0030] [Figure 1A] FIG. 2 is a side cross-sectional view of a MOV / GDT device. [Figure 1B] FIG. 1B is an enlarged view of the seal portion of the MOV / GDT device of FIG. 1A. [Figure 2A] FIG. 1C illustrates that in some embodiments, the MOV / GDT device of FIGS. 1A and 1B can have a rectangular profile having overall length and width dimensions. [Figure 2B] FIG. 1C illustrates that in some embodiments, the MOV / GDT device of FIGS. 1A and 1B can have a rectangular profile having overall length and width dimensions. [Figure 3A]FIG. 1C shows that in some embodiments, the MOV / GDT device of FIGS. 1A and 1B can have a circular side profile having an overall diameter. [Figure 3B] FIG. 1C shows that in some embodiments, the MOV / GDT device of FIGS. 1A and 1B can have a circular side profile having an overall diameter. [Figure 4A] FIG. 1 illustrates an example of how parts of a MOV / GDT device can be manufactured. [Figure 4B] FIG. 1 illustrates an example of how parts of a MOV / GDT device can be manufactured. [Figure 4C] FIG. 1 illustrates an example of how parts of a MOV / GDT device can be manufactured. [Figure 4D] FIG. 1 illustrates an example of how parts of a MOV / GDT device can be manufactured. [Figure 5A] FIG. 5 shows an example of how a MOV / GDT device can be manufactured using the components manufactured in the example of FIGS. 4A-4D. [Figure 5B] FIG. 5 shows an example of how a MOV / GDT device can be manufactured using the components manufactured in the example of FIGS. 4A-4D. [Figure 5C] FIG. 5 shows an example of how a MOV / GDT device can be manufactured using the components manufactured in the example of FIGS. 4A-4D. [Figure 6A] FIG. 1 shows a stack having multiple unsealed sets prior to the sealing process. [Figure 6B] FIG. 6B is an enlarged view of one side of the stack of FIG. 6A. [Figure 7] FIG. 13 illustrates that in some embodiments, a selected force can be applied to the top of an unsealed set of stacks. [Figure 8] FIG. 13 shows that in some embodiments, a force can be applied to the top of the stack of sets during the sealing process to obtain a sealed stack of sets, each set including a seal layer having a thickness dimension resulting from the fusion of two sealing layers. [Figure 9]FIG. 1B shows a MOV / GDT device having a GDT portion similar to that of FIG. 1A. [Figure 10A] FIG. 2 is a pictorial representation of a cross-sectional view of a seal portion of a MOV / GDT device having one or more features as described herein. [Figure 10B] 10B depicts the exemplary seal portion of FIG. 10A having similar dimensions as the exemplary seal portion of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Headings, if any, herein are for convenience only and do not necessarily affect the scope or intent of the claimed invention.

[0032] Disclosed herein are several examples of electrical devices having a combination of a metal oxide varistor (MOV) and a gas discharge tube (GDT), where the GDT includes a low voltage function. For convenience of explanation, such electrical devices are referred to herein as MOV / GDT devices or simply MOV / GDTs. Examples related to such MOV / GDT devices are described in International Publication No. WO2021 / 174140A1, the disclosure of which is expressly incorporated herein by reference in its entirety.

[0033] 1A is a cross-sectional side view of a MOV / GDT device 100 including a sealed chamber 116 having opposing surfaces. A first electrode 114 may be mounted on one of such opposing surfaces and a second electrode 118 may be mounted on the other surface, thereby forming a GDT configuration 104 (also referred to herein as a GDT). For purposes of explanation, the first and second electrodes 114, 118 may also be referred to herein as inner electrodes, first and second inner electrodes, GDT electrodes, first and second GDT electrodes, or some combination thereof.

[0034] In the example of FIG. 1A, the first electrode 114 of the GDT 104 is also shown to function as one of two electrodes of a first MOV configuration 102 (also referred to herein as a MOV). More specifically, a metal oxide layer 112 is shown implemented between the first electrode 114 of the GDT 104 and a first outer electrode 110, thereby providing a first MOV function. Similarly, the second electrode 118 of the GDT 104 is also shown to function as one of two electrodes of a second MOV configuration 106 (also referred to herein as a MOV). More specifically, a metal oxide layer 120 is shown implemented between the second electrode 118 of the GDT 104 and a second outer electrode 122, thereby providing a second MOV function.

[0035] FIG 1B is an expanded view of the seal portion 130 of the MOV / GDT device 100 of FIG 1A. With reference to FIGS. 1A and 1B, the GDT 104 is shown to include a sealing layer 128 formed from an electrically insulating material, such as glass. Such a sealing layer may be formed as described herein to have a thickness d3 approximately equal to the gap dimension d4 between the first and second electrodes 114, 118. In the example of FIGS. 1A and 1B, the sealing layer 128 may also define a lateral dimension d1 of the sealed chamber 116.

[0036] 1A and 1B, each of the first and second electrodes 114, 118 is shown to have a thickness of d5. In some embodiments, an emissive coating may be provided on the sealed chamber surface of each of the first and second electrodes 114, 118. For example, as shown in FIG. 1B, the first electrode 114 may be provided with an emissive coating 124 and the second electrode 118 may be provided with an emissive coating 126.

[0037] 2A and 2B show that in some embodiments, the MOV / GDT device 100 of FIGURES 1A and 1B may have a rectangular side profile having an overall length dimension d15 and an overall width dimension d15'. It will be understood that such rectangular side profiles may include square and non-square shapes.

[0038] In the rectangular shaped MOV / GDT device 100 of Figures 2A and 2B, the sealed chamber (116 of Figure 1A) may also have a rectangular side shape such that the lateral dimension d1 of Figure 1A may be the length dimension d11 of Figures 2A and 2B. In such a configuration, the width dimension of the rectangular shaped sealed chamber is shown as d11'.

[0039] In the rectangular shaped MOV / GDT device 100 of Figures 2A and 2B, the rectangular shaped sealed chamber may be defined by the rectangular shaped boundaries of a sealing layer, such as a glass sealing layer (128 in Figures 1A and 1B) having a lateral width dimension d12 (d2 in Figure 1B). In the example of Figure 2B, the lateral width dimension (d12) of the glass sealing layer along the length of the MOV / GDT device 100 is depicted as being the same as the lateral width dimension (d12) along the width of the MOV / GDT device 100. However, it will be understood that the lateral width dimension of the glass sealing layer along the length of the MOV / GDT device 100 may or may not be the same as the lateral width dimension along the width of the MOV / GDT device 100.

[0040] Figures 3A and 3B show that in some embodiments, the MOV / GDT device 100 of Figures 1A and 1B can have a circular side profile with an overall diametric dimension d25. In the circular shaped MOV / GDT device 100 of Figures 3A and 3B, the enclosed chamber (116 of Figure 1A) can also have a circular side profile such that the lateral dimension d1 of Figure 1A can be the diametric dimension d21 of Figures 3A and 3B.

[0041] In the circular-shaped MOV / GDT device 100 of Figures 3A and 3B, the aforementioned circular-shaped sealed chamber may be defined by a ring-shaped boundary of a sealing layer, such as a glass sealing layer (128 in Figures 1A and 1B) having a lateral width dimension d22 (d2 in Figure 1B).

[0042] 4A-4D and 5A-5C show an example of how a MOV / GDT device having one or more features as described herein may be fabricated to provide a desired discharge voltage (e.g., a desired low discharge voltage) characteristic of the GDT portion. In FIG. 4A-4D, such a fabrication process may include multiple process steps performed while multiple units are mounted in an array format. In FIG. 5A-5C, the fabrication process may include multiple process steps using one or more stacks of units fabricated in the process steps of FIG. 4A-4D to form multiple MOV / GDT devices.

[0043] 4A illustrates a process stage at which a metal oxide plate 150 may be provided or formed. Such a plate is shown to include a number of units 152, each unit eventually becoming part of a respective MOV / GDT device.

[0044] 4B, electrodes 154 may be formed on the metal oxide 150 of each unit 152 to form an assembly 156. In some embodiments, each such electrode may become an external electrode (e.g., 110 or 122 in FIG. 1A) of a respective MOV / GDT device.

[0045] 4C, an electrode 158 may be formed on the metal oxide 150 opposite electrode 154 of each unit 152. In some embodiments, each such electrode may become an internal electrode (e.g., 114 or 118 in FIG. 1A) for the GDT portion of a respective MOV / GDT device.

[0046] The process step of Figure 4C is shown to further include a layer 160 of sealing material formed at or near the periphery of each unit 152 to form an assembly 164. In some embodiments, each such sealing layer 160 may be formed from an electrically insulating material, such as an insulating sealing glass or other high temperature insulating sealing material. In some embodiments, the sealing layer 160 may be sized to provide one or more functions described herein, including providing a desired gap dimension (e.g., d4 in Figure 1B) in the respective MOV / GDT device.

[0047] 4C may further include an emissive coating 162 formed on the laterally inner portion of the corresponding electrode 158. It will be understood that in some embodiments, the emissive coating 162 may or may not be used.

[0048] At the process step of FIG. 4D, the assembly 164 of FIG. 4C can be separated (eg, along separation lines 166) into a plurality of individual units 170.

[0049] 5A-5C show one example of how multiple individual units 170 of FIG. 4D may be assembled to form one or more MOV / GDT devices.

[0050] FIG 5A illustrates that in some embodiments, one or more sets of individual units 170 of FIG 4D may be stacked within an apparatus 180. More specifically, the exemplary apparatus 180 of FIG 5A is shown to include two stacking receptacles 182a, 182b, each stacking receptacle sized to receive one or more sets 172 of individual units 170. Each stacking receptacle (182a or 182b) is shown to include a floor surface (183a or 183b). It will be understood that the apparatus 180 may include more or less than the exemplary number of two stacking receptacles in FIG 5A.

[0051] Each set 172 of individual units 170 is shown to include two individual units 170 oriented with the faces having their respective sealing layers (160 in FIG. 4D) facing each other. A first stacking receptacle 182a is shown with three sets of individual units 170 already stacked. A second stacking receptacle 182b is shown with the same number of sets of individual units 170 in the process of being placed into the receptacle 182b.

[0052] Once the stacking process is complete, as with the stack in the first receptacle 182a, the apparatus 180 can supply the desired gas (e.g., an inert gas, an active gas, or some combination thereof) such that the unsealed chambers of each set of units 170 are filled with gas. The stack can then be heated such that the sealing layers (160 in FIG. 4D) of each set of units 170 fuse to form fused units 190 having respective seals 186 and sealed chambers 184 with the desired gas therein, as shown in FIG. 5B.

[0053] FIG. 5C shows that once the stack has cooled from the heating process, each fused unit 190 can be removed from its respective receptacle to become a MOV / GDT device 100 having one or more features as described herein.

[0054] Figures 6-8 show an example of how a plurality of MOV / GDT devices having one or more features as described herein may be formed in the stack configuration of Figures 5A-5C. Figure 6A shows a stack having a plurality of unsealed sets 172 prior to the encapsulation step, each set having two individual units (170 in Figure 5A) oriented such that the faces having the respective encapsulation layers (160 in Figure 4D) face each other, similar to the example of Figure 5A. A stack of such sets 172 is shown supported by a floor 183 (e.g., floor 183a of stacking receptacle 182a in Figure 5A).

[0055] Figure 6B is an expanded view of one side of the stack of Figure 6A, in which three exemplary sets are each shown as 172, each set having a dimension d31 of the first outer electrode (154 in Figure 4D), a dimension d32 of the first MOV layer (150 in Figure 4C), a dimension d33 of the first inner electrode (158 in Figure 4D), a dimension d34 of the first encapsulation layer (160 in Figure 4D), a dimension d34 of the second encapsulation layer (160 in Figure 4D), a dimension d33 of the second inner electrode (158 in Figure 4D), a dimension d32 of the second MOV layer (150 in Figure 4C), and a dimension d31 of the second outer electrode (154 in Figure 4D). Thus, the total height of the three stacks of FIG. 6B is approximately 3×(d31+d32+d33+d34+d34+d33+d32+d31) from floor 183 when the stacks are in an unsealed state.

[0056] 7 illustrates that in some embodiments, a selected force F (shown as arrow 173) can be applied to the top of the unsealed stack of sets 172. Such force allows the unsealed stack of sets 172 to remain stacked on a floor surface 183 as the sealing process is introduced.

[0057] FIG. 8 illustrates that in some embodiments, a force F (shown as arrow 173) may be applied to the top of a stack of multiple sets during a sealing process to form a sealed stack of multiple sets 190, each set including a sealing layer (128 in FIG. 1B) having a thickness dimension of d3 formed by fusing two sealing layers (160 in FIG. 4D, each having a thickness dimension of d34 in FIG. 7). It should be noted that during the sealing process under force F, the thickness of the sealing layer may be reduced from the thickness of the two unfused sealing layers (i.e., 2×d34) due to the fusing of the two sealing layers. Thus, by applying an appropriate force F before and / or during the sealing process, the two fused sealing layers melt and fuse with mechanical properties including the flexible mechanical properties of the fusion layer, so that a desired thickness value of d3 in FIG. 8 can be obtained. As described herein, such thickness value of the sealing layer generally forms a gap dimension between two internal electrodes facing each other in a respective GDT.

[0058] In some embodiments, the force F in the example of Figure 7 (before the sealing step) and the force F in the example of Figure 8 (during the sealing step) may or may not be the same. In some embodiments, the force in the example of Figure 8 (during the sealing step) may be a constant force, a time-varying force, or a combination thereof.

[0059] With reference to FIGS. 5-8, it should be noted that in some embodiments, the desired thickness dimension (d3 in FIG. 8) of the seal (186 in FIG. 5B) of each MOV / GDT device can be achieved by, for example, some or all of the following: (1) precise control of the printing of the glass (e.g., if the seal is a glass seal) to obtain a uniform amount of glass relative to the surface area of ​​the internal electrodes and total volume of glass covered; and (2) the amount of force (e.g., force 173 in FIG. 8) applied to the stack during the sealing process.

[0060] 1-8, each MOV / GDT device 100 is depicted as having a planar external electrode (e.g., 110 and 122 in FIG. 1A) formed on a respective planar external surface (e.g., 112 and 120 in FIG. 1A) of a metal oxide layer. In some embodiments, a MOV / GDT device may include a non-planar external surface of a metal oxide layer and a respective non-planar external electrode.

[0061] For example, Figure 9 illustrates a MOV / GDT device 100 having a GDT portion 104 similar to the MOV / GDT device 100 of Figure 1A. However, for the MOV / GDT device 100 of Figure 9, the first metal oxide layer 112 is shown to include a non-planar outer surface to accommodate the first outer electrode 110 having a flared edge configuration. Similarly, the second metal oxide layer 120 is shown to include a non-planar outer surface to accommodate the second outer electrode 122 having a flared edge configuration. Further details regarding MOVs having one or more flared edge electrodes can be found in International Publication No. WO 2021 / 174140 A1, referenced above.

[0062] In the example of Figure 9, the GDT portion 104 of the MOV / GDT device 100 may be similar to the example of Figure 1A. Thus, the seal portion 130 of the MOV / GDT device 100 of Figure 9 may be similar to the seal portion 130 of the MOV / GDT device 100 of Figures 1A and 1B. It will be appreciated that the gap dimension (d4 in Figure 1B) between the two internal electrodes (114, 118 in Figure 1B) provided by the selected thickness of the sealing layer (128 in Figure 1B) may or may not be the same between the MOV / GDT device 100 of Figure 1A and the MOV / GDT device 100 of Figure 9.

[0063] In some embodiments, the MOV / GDT device 100 of Figure 9 can be fabricated similarly to the examples described herein with reference to Figures 4-8. In some embodiments, the additional process step of forming recesses for each unit on the surface of the metal oxide plate (150 in Figure 4A) can be accomplished as described in International Publication No. WO2021 / 174140A1 referenced above.

[0064] Figure 10A shows a photographic line drawing of a cross-section of a seal portion 130 of a MOV / GDT device having one or more features as described herein. Figure 10B depicts the seal portion of Figure 10A having similar dimensions as the exemplary seal portion of Figure 1B.

[0065] 10A and 10B show that in some embodiments, the sealing layer 128, which provides a thickness dimension of d3 to form a desired gap dimension d4 between opposing electrodes 114, 118 of the sealed chamber 116, can include a laterally extending portion 129 formed to cover a respective portion of either or both of the electrodes 114, 118. In the example of FIG. 10A and 10B, such an extending portion of the sealing layer 128 is shown to cover a respective portion of both of the electrodes 114, 118. In the example of FIG. 10B, each of the first and second electrodes 114, 118 is shown to have a thickness of d5.

[0066] In some embodiments, such a seal extension is desirable to increase the length of the leak path to reduce leakage of current between the two electrodes 114, 118. Further details regarding such seal extensions can be found in International Publication No. WO2021 / 174140A1 referenced above.

[0067] In various examples described herein, a set of individual units (e.g., set 172 of individual units 170 in FIG. 5A) that are processed to form a MOV / GDT device is assumed to include two identical individual units oriented such that the faces having the internal electrodes (158 in FIG. 4D) and encapsulation layers (160 in FIG. 4D) face each other. However, it will be understood that in some embodiments, the two individual units of a set need not necessarily be identical to form a MOV / GDT device having one or more features as described herein.

[0068] For example, one individual unit may have a sealing layer that has a different pre-sealing thickness than the sealing layer of another individual unit, and such different thickness values ​​of the sealing layers may be selected such that when the pair is sealed, the resulting seal has the desired dimensions, including thickness.

[0069] In another example, one individual unit may have a sealing layer while the other individual unit does not have a sealing layer prior to the sealing process. The sealing layer on one such individual unit may have a thickness value selected such that when the pair is sealed, the resulting seal has the desired dimensions, including thickness.

[0070] In the experiments, various configurations of MOV / GDT devices with low voltage GDT capability were tested. In such MOV / GDT devices, the gap in the GDT electrodes is formed by the thickness of the glass seal, allowing for smaller device sizes and lower voltages. Neon and argon gases were tested to provide low voltage capability. Additionally, the chemistry of the emissive coatings (e.g., glass and active coatings) was varied to provide and / or enhance low voltage capability. In some embodiments, the active coatings can be configured to produce a substantially uniform and repeatable breakdown voltage at a selected level.

[0071] In the control configuration, the MOV / GDT device contained an emissive coating made of glass and used argon as the GDT gas. Both the type of emissive coating and the type of gas were varied, and it was expected that the MOV / GDT device with neon gas (e.g., about 500 torr) and an active emissive coating would have the lowest breakdown GDT voltage among the various neon / argon and glass coating / active coating combinations.

[0072] It has been found that the selection of the gap dimension provided by the thickness of the glass seal reduces the breakdown GDT voltage, regardless of the type of gas and the type of coating. It has also been found that the combination of neon gas with an active coating distributes the breakdown GDT voltage to a very low value of about 90V. In some embodiments, such an active coating may include one or more alkali metals, such as cesium or sodium, one or more compounds based on an alkali metal, or a combination thereof. Such a distribution of very low values ​​of the breakdown GDT voltage may be more effective because the combination minimizes or reduces the amount of energy required to induce activation of the alkali elements and / or compounds.

[0073] In some embodiments, a MOV / GDT device having one or more features as described herein includes a planar arrangement of internal electrodes, thereby providing a capacitance similar to a parallel plate capacitor that depends only on the gap dimension established by the thickness of the seal (e.g., glass seal). Thus, the capacitance characteristics of such a MOV / GDT device can be increased by increasing the thickness of the seal and decreased by decreasing the thickness of the seal.

[0074] In one example of a MOV / GDT device, a gap distance of about 280 μm was provided between two inner electrodes having an active emissive coating. About 500 torr of neon gas was provided in the resulting sealed chamber. In a sample count of 140, such MOV / GDT devices exhibited an average GDT breakdown voltage of about 111 V before conditioning and about 95 V after conditioning.

[0075] Unless the context clearly requires otherwise, throughout the specification and claims, words such as "comprises," "comprising," and the like are to be interpreted in an inclusive sense, i.e., "including, but not limited to," as opposed to an exclusive or exhaustive sense. Generally, as used herein, the term "coupled" means that two or more elements are directly connected or connected through one or more intermediate elements. Also, the words "herein," "above," "below," and similar words, when used in this application, refer to this application as a whole and not to any particular portion of this application. Herein, where the context permits, words in the singular or plural form in the specification can include the plural or singular, respectively. The word "or" referring to a list of two or more items includes all of the following interpretations: any of the items in the list, all of the items in the list, and any combination in the list.

[0076] The above detailed description of the embodiments of the present invention is not intended to be exhaustive or to limit the invention to the precise form disclosed above. Although specific embodiments of, and examples for, the present invention have been described above for illustrative purposes, various equivalent modifications are possible within the scope of the present invention, as those skilled in the relevant art will recognize. For example, while processes or blocks are shown in a certain order, alternative embodiments may perform routines having steps or use systems having blocks in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and / or modified. Each of these processes or blocks may be implemented in a variety of different ways. Also, while processes or blocks may be shown to be performed in series, these processes or blocks may instead be performed in parallel or at different times.

[0077] The teachings of the invention provided herein may be applied to other systems, not necessarily those described above. Elements and acts of the various embodiments described above may be combined to provide further embodiments.

[0078] Although several embodiments of the present invention have been described, these embodiments are presented for illustrative purposes only and are not intended to limit the scope of the present disclosure. Indeed, the novel methods and systems described herein may be embodied in various other forms, and various omissions, substitutions, and modifications of the forms of the methods and systems described herein may be made without departing from the spirit of the present disclosure. The appended claims and their equivalents are intended to cover such forms or modifications that would fall within the scope and spirit of the present disclosure.

Claims

1. 1. A method for manufacturing a plurality of electrical devices, comprising: forming or providing a number of metal oxide varistors (MOVs), each MOV including an external electrode on a first side of a metal oxide layer and an internal electrode on a second side of the metal oxide layer; forming a layer of encapsulation material at or near a periphery of the second surface of the metal oxide layer of each MOV; forming a stack having one or more sets, each set including two MOVs having opposing second surfaces such that respective layers of sealing material engage each other; performing a sealing process for fusing mated layers of sealing material to form a seal between two of the internal electrodes of each set to form a sealed chamber of a gas discharge tube (GDT), the seal having a thickness dimension approximately equal to a selected gap dimension between the two internal electrodes; The method includes:

2. 2. The method of claim 1, wherein forming the layer of encapsulation material results in a thickness of the layer of encapsulation material of one of the two MOVs in each set being substantially the same as a thickness of the layer of encapsulation material of the other of the two MOVs in that set.

3. The method of claim 1 , wherein the sealing material comprises glass or other high temperature insulating sealing material.

4. The method of claim 1 , wherein forming or providing the MOVs causes the outer electrode of each MOV to be substantially planar.

5. The method of claim 1 , wherein forming or providing the MOVs results in the outer electrode of each MOV having a flared edge configuration.

6. The method of claim 1 , wherein the stack comprises a plurality of sets.

7. 2. The method of claim 1, wherein performing the sealing step includes supplying a desired gas to the stack such that the desired gas is introduced into the unsealed chambers of each set of MOVs.

8. The method of claim 7 , wherein the desired gas comprises an inert gas and / or an active gas.

9. The method of claim 7 , wherein the desired gas comprises neon or argon.

10. 10. The method of claim 9, wherein the desired gas comprises neon at approximately 500 Torr.

11. The method of claim 7 further comprising forming an emissive coating on each of the inner electrodes.

12. The method of claim 11 , wherein the emissive coating comprises a glass or an active coating.

13. The method of claim 12 , wherein the emissive coating comprises the active coating.

14. The method of claim 13 , wherein the active coating comprises an alkali metal or alkali-based compound.

15. 12. The method of claim 11, wherein the gap size between the two inner electrodes, the emissive coating, and the desired gas are selected to provide a breakdown voltage of the GDT of less than 120V.

16. 12. The method of claim 11, wherein the breakdown voltage of the GDT is less than 100V.

17. The method of claim 7 , wherein the selected gap dimension between the two inner electrodes is less than 500 μm.

18. 20. The method of claim 17, wherein the selected gap dimension between the two inner electrodes is in the range between 250 μm and 300 μm.

19. 20. The method of claim 18, wherein the selected gap dimension between the two inner electrodes is approximately 280 μm.

20. 2. The method of claim 1, wherein the seal includes a laterally extending portion formed to cover a portion of either or both of the internal electrodes to increase a leak path length between the internal electrodes.

21. 21. The method of claim 20, wherein the laterally extending portion is formed by the sealing step and / or by an extension of the sealing material formed prior to the sealing step.

22. The method of claim 1 , wherein the sealing step includes applying a selected force to the stack to effect the thickness dimension of each set of the seals.

23. 1. A system for manufacturing a plurality of electrical devices, comprising: a metal oxide varistor (MOV) fabrication apparatus configured to form or provide a number of MOVs, each MOV including an external electrode on a first side of a metal oxide layer and an internal electrode on a second side of the metal oxide layer; a gas discharge tube (GDT) fabrication apparatus configured to form a layer of sealing material at or near an outer periphery of the second surface of the metal oxide layer of each MOV, the GDT fabrication apparatus being further configured to form a stack having one or more sets, each set including two MOVs having opposing second surfaces such that the respective layers of sealing material engage each other, the GDT fabrication apparatus being further configured to perform a sealing step of fusing the engaged layers of sealing material to form a seal between two internal electrodes of each set forming a sealed chamber of the gas discharge tube (GDT), the seal having a thickness dimension approximately the same as a selected gap dimension between the two internal electrodes; A system having

24. first and second metal oxide varistors (MOVs), each MOV including an external electrode on a first side of a respective metal oxide layer and an internal electrode on a second side of the metal oxide layer; a seal located at or near the outer periphery of the second surface of the metal oxide layer of each of the first and second MOVs, thereby forming a sealed chamber having a desired gas therein of a gas discharge tube (GDT) between the two internal electrodes of the first and second MOVs, the seal having a thickness dimension approximately equal to a selected gap dimension between the two internal electrodes; An electrical device having

25. 25. The electrical device of claim 24, wherein the seal comprises glass or other high temperature insulating sealing material.

26. 25. The electrical device of claim 24, wherein the outer electrode of each MOV is substantially flat.

27. 25. The electrical device of claim 24, wherein the outer electrode of each MOV has a flared edge configuration.

28. 25. The electrical device of claim 24, wherein the desired gas comprises an inert gas and / or an active gas.

29. 30. The electrical device of claim 28, wherein the desired gas comprises neon or argon.

30. 30. The electrical device of claim 29, wherein the desired gas comprises neon at approximately 500 Torr.

31. 31. The electrical device of claim 30, further comprising an emissive coating on each of the internal electrodes.

32. 32. The electrical device of claim 31, wherein the emissive coating comprises a glass or an active coating.

33. 33. The electrical device of claim 32, wherein the emissive coating comprises the active coating.

34. 34. The electrical device of claim 33, wherein the active coating comprises an alkali metal or alkali-based compound.

35. 32. The electrical device of claim 31, wherein the gap size between the two inner electrodes, the emissive coating, and the desired gas are selected to provide a breakdown voltage of the GDT of less than 120V.

36. 36. The electrical device of claim 35, wherein the GDT has a breakdown voltage of less than 100V.

37. 25. The electrical device of claim 24, wherein the selected gap dimension between the two internal electrodes is less than 500 [mu]m.

38. 38. The electrical device of claim 37, wherein the selected gap dimension between the two internal electrodes is in the range between 250 μm and 300 μm.

39. 40. The electrical device of claim 38, wherein the selected gap dimension between the two internal electrodes is approximately 280 μm.

40. 25. The electrical device of claim 24, wherein the seal includes a laterally extending portion formed to cover a portion of either or both of the internal electrodes to increase a length of a leak path between the internal electrodes.

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