Gas discharge tube with improved ratio of leak path length to gap dimension.

Abstract

In some embodiments, a gas discharge tube (GDT) can include first and second electrodes, each including an edge and an inwardly facing surface, where the inwardly facing surfaces of the first and second electrodes face each other. The GDT can further include a sealing portion mounted to join and seal portions of the edges of the inwardly facing surfaces of the first and second electrodes to define a sealed chamber between the inwardly facing surfaces of the first and second electrodes. The GDT can further include an electrical insulator mounted to form a surface within the sealed chamber and cover a portion of each inwardly facing surface of at least one of the first and second electrodes, whereby a leak path within the sealed chamber includes the surface of the electrical insulator.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Application No. 62 / 863,777, filed June 19, 2019, entitled “GAS DISCHARGE TUBE HAVING ENHANCED RATIO OF LEAKAGE PATH LENGTH TO GAP DIMENSION,” the disclosure of which is expressly incorporated herein by reference in its entirety.

[0002] The present disclosure relates to gas discharge tubes (GDTs) and related methods and apparatus. [Background technology]

[0003] A gas discharge tube (GDT) is a device that has a volume of gas enclosed between two electrodes. When a sufficient potential difference is applied between the two electrodes, the gas ionizes and becomes a conductive medium, thereby capable of producing an electric current in the form of an arc.

[0004] Based on these principles of operation, GDTs can be constructed to provide reliable and effective protection for a variety of applications during electrical disturbances. In some applications, GDTs may be preferred over semiconductor discharge devices due to characteristics such as low capacitance and low insertion / return loss. Thus, GDTs are frequently used in telecommunications and other applications where protection against electrical disturbances such as overvoltages is desired. Summary of the Invention [Means for solving the problem]

[0005] In some embodiments, the disclosure relates to a gas discharge tube (GDT) including first and second electrodes, each including an edge and an inwardly facing surface, the inwardly facing surfaces of the first and second electrodes facing each other. The GDT further includes a sealing portion mounted to join and seal a portion of the edges of the inwardly facing surfaces of the first and second electrodes to define a sealed chamber between the inwardly facing surfaces of the first and second electrodes. The GDT further includes an electrical insulator mounted to form a surface within the sealed chamber and cover a portion of each inwardly facing surface of at least one of the first and second electrodes, such that a leak path within the sealed chamber includes the surface of the electrical insulator.

[0006] In some aspects, electrical insulation may be implemented on each of both the first and second electrodes.

[0007] In some aspects, the GDT may further include a spacer mounted between the first and second electrodes. The spacer may have a first surface and a second surface and define an opening having an inner wall extending from the first surface to the second surface, such that the sealed chamber is further defined by the inner wall. In some aspects, the spacer may be formed of an electrically insulating material, such as a ceramic. In some aspects, the leak path may have a length that is greater than a thickness dimension of the spacer. In some aspects, the leak path may have a length that includes the sum of a path associated with each electrical insulation portion and a thickness dimension of the spacer.

[0008] In some aspects, the seal may include a seal layer mounted between each of the first and second faces of the spacer and the corresponding electrode.

[0009] In some aspects, the sealing layer may be formed of an electrically conductive material. In some aspects, each electrically insulating portion may extend laterally inward from an inner wall of the opening in the spacer, and each sealing layer may be separated from the electrically insulating portion by the electrically insulating material of the spacer.

[0010] In some embodiments, the sealing layer may be formed of an electrically insulating material. In some embodiments, each of the electrical insulators may also be formed of the electrically insulating material of the sealing layer. In some embodiments, each of the electrical insulators and the sealing layer may form a continuous structure. In some embodiments, the electrically insulating material of the sealing layer may include glass.

[0011] In some aspects, the spacer may be dimensioned to extend laterally from an inner wall to an outer wall that is generally coplanar with the outer edges of the first and second electrodes.

[0012] In some aspects, the spacer may have a dimension such that it extends laterally from the inner wall to the outer wall laterally beyond the outer edges of the first and second electrodes. The spacer may include a notch structure at a corner of the outer wall of at least one of the first and second sides, the notch structure resulting in separation of the spacer from other spacers. The spacer extending laterally beyond the outer edges of the first and second electrodes may increase an external leak path length between the first and second electrodes.

[0013] In some embodiments, the sealing portion may be formed of an electrically insulating material and configured to directly bond and seal the first and second electrodes without a spacer. Each of the electrically insulating portions may extend laterally inward from the sealing portion. In some embodiments, each of the electrically insulating portions may also be formed of the electrically insulating material of the sealing portion. In some embodiments, the electrically insulating portion and the sealing portion may form a continuous structure. In some embodiments, the electrically insulating material of the sealing portion may include glass.

[0014] In some embodiments, each of the first and second electrodes may be formed of a metal layer. Each electrical insulation portion may be sized to expose a discharge portion on the inwardly facing surface of the respective electrode. In some embodiments, the discharge portion of the electrode may include one or more layers mounted on the inwardly facing surface of the metal layer. Such one or more layers may include a silver ink layer. Such one or more layers may further include a silver textured layer on the silver ink layer. Such one or more layers may further include an emissive coating layer on the silver textured layer.

[0015] In some aspects, the discharge portion of the electrode may include a textured structure formed on the inwardly facing surface of the metal layer. The textured structure may include a stamped metal structure formed on the metal layer. In some aspects, the discharge portion of the electrode may further include an emissive coating layer on the textured structure.

[0016] In some aspects, the discharge portion and the portion of each inwardly facing surface covered by the electrical insulation portion may be substantially flat.

[0017] In some aspects, the discharge portion and the portion of the respective inwardly facing surface covered by the respective electrical insulation portion may form a concave surface. In some aspects, the concave surface may include a substantially flat inner portion and an angled outer portion, such that at least a portion of the angled outer portion is covered by the respective electrical insulation portion. In some aspects, substantially all of the angled outer portion may be covered by the respective electrical insulation portion.

[0018] In some embodiments, the present disclosure relates to a method of manufacturing a gas discharge tube (GDT). The method includes forming or providing first and second electrodes, each including an edge and an inwardly facing surface. The method further includes covering a portion of each inwardly facing surface of at least one of the first and second electrodes with an electrically insulating material. The method further includes bonding and sealing portions of the edges of the inwardly facing surfaces of the first and second electrodes to define a sealed chamber between the inwardly facing surfaces of the first and second electrodes, such that a leak path in the sealed chamber includes the surface of the electrically insulating material.

[0019] In some aspects, joining and sealing portions of the edges of the inwardly facing surfaces of the first and second electrodes may include providing an electrically insulating spacer between the first and second electrodes, the spacer having a first side and a second side and defining an opening having an inner wall extending from the first side to the second side, such that the sealed chamber is further defined by the inner wall.

[0020] In some aspects, joining and sealing portions of the edges of the inwardly facing surfaces of the first and second electrodes may further include forming a sealing layer mounted between each of the first and second surfaces of the spacer and the corresponding electrode.

[0021] In some aspects, joining and sealing portions of the edges of the inwardly facing surfaces of the first and second electrodes may include forming an electrical insulator formed of an electrically insulating material that directly joins and seals the first and second electrodes without a spacer.

[0022] In some embodiments, the present disclosure relates to a method of manufacturing a plurality of gas discharge tubes (GDTs). The method includes providing or forming an electrically insulating plate defining an array of spacer units, each spacer unit having a first and second side and defining an opening having an interior wall extending from the first side to the second side. The method further includes forming or providing first and second electrodes, each including an edge and an inwardly facing surface. The method further includes covering a portion of each inwardly facing surface of at least one of the first and second electrodes with an electrically insulating material. The method further includes sealing the opening of each spacer unit with the first and second electrodes, such that portions of the edges of the inwardly facing surfaces of the first and second electrodes define a sealed chamber between the inward faces of the first and second electrodes and such that a leak path within the sealed chamber includes the surface of the electrically insulating material.

[0023] In some aspects, the method may further comprise separating the array of spacer units into a plurality of separate units.

[0024] In some embodiments, the method may further include providing or forming a metal sheet having an array of electrode units and separating the array of electrode units to provide the first and second electrodes.

[0025] In some embodiments, the disclosure relates to a circuit protection device including a gas discharge tube (GDT) having first and second electrodes, each having an edge and an inwardly facing surface, the inwardly facing surfaces of the first and second electrodes facing each other. The GDT further includes a sealing portion mounted to join and seal a portion of the edges of the inwardly facing surfaces of the first and second electrodes to define a sealed chamber between the inwardly facing surfaces of the first and second electrodes. The GDT further includes an electrical insulator mounted to form a surface within the sealed chamber and cover a portion of each of the inwardly facing surfaces of at least one of the first and second electrodes, such that a leak path within the sealed chamber includes the surface of the electrical insulator. The circuit protection device further includes a first clamping device electrically connected to the first electrode of the GDT.

[0026] In some aspects, the first clamping device may be directly connected to the first electrode. In some aspects, the first clamping device may be a metal oxide varistor (MOV) having first and second electrodes and a metal oxide layer mounted between the first and second electrodes. In some aspects, one of the first and second electrodes of the MOV may be configured as a terminal of the circuit protection device and the other electrode of the MOV may be another electrode electrically connected to the first electrode of the GDT. In some aspects, one of the first and second electrodes of the MOV may be configured as a terminal of the circuit protection device and the first electrode of the GDT may be configured as the other electrode of the MOV.

[0027] In some embodiments, the GDT may further include a second clamping device electrically connected to a second electrode of the GDT, hi some embodiments, the second clamping device may be a metal oxide varistor (MOV) having first and second electrodes and a metal oxide layer mounted between the first and second electrodes.

[0028] 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]

[0029] [Figure 1A] FIG. 1 illustrates a gas discharge tube (GDT) having a leakage path that includes a relatively thick spacer thickness dimension. [Figure 1B] FIG. 1B illustrates a thinner GDT than the example of FIG. 1A, in which the spacer is shown to include inward protrusions to increase the leak path length for a reduced spacer thickness. [Diagram 2] FIG. 13 shows an example of a GDT with increased leak path length while using a relatively thin and simple spacer shape. [Diagram 3] FIG. 13 shows an example of a GDT with increased leak path length where the spacer can have an outer wall that is approximately flush with the outer wall of the electrode. [Figure 4] FIG. 13 shows an example of a GDT with increased leak path length where the spacer can have an outer wall that is laterally outboard of the outer wall of the electrode. [Diagram 5] FIG. 5 is a diagram showing a more specific example of the GDT of FIG. [Figure 6] FIG. 13 illustrates that in some embodiments, a GDT can include separate structures that provide a sealing function and structures that laterally increase the leak path length. [Figure 7] FIG. 13 also illustrates that in some embodiments, a spacer in a GDT having one or more features as described herein can include two or more layers. [Figure 8A]6 illustrates various stages of a process that can be used to manufacture the example GDT of FIG. 5. [Figure 8B] 6 illustrates various stages of a process that can be used to manufacture the example GDT of FIG. 5. [Figure 8C] 6 illustrates various stages of a process that can be used to manufacture the example GDT of FIG. 5. [Figure 8D] 6 illustrates various stages of a process that can be used to manufacture the example GDT of FIG. 5. [Figure 8E] 6 illustrates various stages of a process that can be used to manufacture the example GDT of FIG. 5. [Figure 8F] 6 illustrates various stages of a process that can be used to manufacture the example GDT of FIG. 5. [Figure 8G] 6 illustrates various stages of a process that can be used to manufacture the example GDT of FIG. 5. [Figure 8H] 6 illustrates various stages of a process that can be used to manufacture the example GDT of FIG. 5. [Figure 8I] 6 illustrates various stages of a process that can be used to manufacture the example GDT of FIG. 5. [Figure 8J] 6 illustrates various stages of a process that can be used to manufacture the example GDT of FIG. 5. [Figure 9A] 1A-1D are plan views of an array or group of singulated units at various stages of a process that can be used to manufacture multiple GDT devices. [Figure 9B] 1A-1D are plan views of an array or group of singulated units at various stages of a process that can be used to manufacture multiple GDT devices. [Figure 9C] 1A-1D are plan views of an array or group of singulated units at various stages of a process that can be used to manufacture multiple GDT devices. [Figure 9D]1A-1D are plan views of an array or group of singulated units at various stages of a process that can be used to manufacture multiple GDT devices. [Figure 9E] 1A-1D are plan views of an array or group of singulated units at various stages of a process that can be used to manufacture multiple GDT devices. [Figure 9F] 1A-1D are plan views of an array or group of singulated units at various stages of a process that can be used to manufacture multiple GDT devices. [Figure 9G] 1A-1D are plan views of an array or group of singulated units at various stages of a process that can be used to manufacture multiple GDT devices. [Figure 9H] 1A-1D are plan views of an array or group of singulated units at various stages of a process that can be used to manufacture multiple GDT devices. [Figure 9I] 1A-1D are plan views of an array or group of singulated units at various stages of a process that can be used to manufacture multiple GDT devices. [Figure 9J] 1A-1D are plan views of an array or group of singulated units at various stages of a process that can be used to manufacture multiple GDT devices. [Figure 10A] 9A-9J are cross-sectional side views of various stages of the process. [Figure 10B] 9A-9J are cross-sectional side views of various stages of the process. [Figure 10C] 9A-9J are cross-sectional side views of various stages of the process. [Figure 10D] 9A-9J are cross-sectional side views of various stages of the process. [Figure 10E] 9A-9J are cross-sectional side views of various stages of the process. [Figure 10F] 9A-9J are cross-sectional side views of various stages of the process. [Figure 10G] 9A-9J are cross-sectional side views of various stages of the process. [Figure 10H]9A-9J are cross-sectional side views of various stages of the process. [Figure 10I] 9A-9J are cross-sectional side views of various stages of the process. [Figure 10J] 9A-9J are cross-sectional side views of various stages of the process. [Figure 11A] FIG. 1 illustrates an exemplary GDT in which an electrically insulating seal may join first and second electrodes to form a sealed chamber without a separate spacer. [Figure 11B] FIG. 13 illustrates another exemplary GDT in which an electrically insulating seal may join first and second electrodes to form a sealed chamber without a separate spacer. [Figure 12A] FIG. 1 illustrates an exemplary GDT in which an electrically insulating seal may join first and second electrodes having inwardly facing surfaces to form a chamber without a separate spacer. [Figure 12B] FIG. 13 illustrates another exemplary GDT in which an electrically insulating seal may join first and second electrodes having inwardly facing surfaces to form a chamber without a separate spacer. [Figure 13] FIG. 14 shows an example GDT having first and second electrodes similar to the example of FIGS. 12A and 12B, but including an electrically insulating seal configured to increase the leak path length. [Figure 14] FIG. 1 illustrates an example of a circuit protection device including a GDT in combination with a clamp device having one or more features described herein. [Figure 15] 1 illustrates another example of a circuit protection device having one or more features described herein and including a GDT in combination with a first clamping device on one side and a second clamping device on the other side. [Figure 16] 15 is a diagram showing a circuit protection device that may be a more specific example of the circuit protection device of FIG. 14. [Figure 17] 16 is a diagram showing a circuit protection device that may be a more specific example of the circuit protection device of FIG. 15. [Figure 18A] 1 illustrates various stages of a process that may be performed to manufacture a plurality of circuit protection devices. [Figure 18B] 1 illustrates various stages of a process that may be performed to manufacture a plurality of circuit protection devices. [Figure 18C] 1 illustrates various stages of a process that may be performed to manufacture a plurality of circuit protection devices. [Figure 18D] 1 illustrates various stages of a process that may be performed to manufacture a plurality of circuit protection devices. [Figure 18E] 1 illustrates various stages of a process that may be performed to manufacture a plurality of circuit protection devices. [Figure 18F] 1 illustrates various stages of a process that may be performed to manufacture a plurality of circuit protection devices. [Figure 18G] 1 illustrates various stages of a process that may be performed to manufacture a plurality of circuit protection devices. [Figure 18H] 1 illustrates various stages of a process that may be performed to manufacture a plurality of circuit protection devices. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Headings, if any, herein are for convenience only and do not necessarily affect the scope or intent of the claimed invention.

[0031] A gas discharge tube (GDT) is a device that has a sealed gas chamber with opposing electrodes. When such a GDT is exposed to an electrical condition, such as an overvoltage condition, an arc occurs between the electrodes and through the sealed gas, thereby discharging the overvoltage condition. Thus, the design of a GDT may include, for example, the type of gas, the gap size between the electrodes, and the overall dimensions of the device, depending on the intended use of the GDT.

[0032] In a typical GDT, leakage currents may exist between the electrodes. Such leakage currents typically follow leakage paths from one electrode to the other along various sides of the sealed chamber. In many applications of GDTs, it is desirable to reduce such leakage currents. To achieve such a reduction in leakage currents, the corresponding leakage paths may be increased. In some embodiments, it is desirable to have long leakage paths relative to the gap dimensions of the corresponding electrodes.

[0033] 1A and 1B show examples of how the leak path can be increased to reduce leakage current. For example, FIG. 1A shows a GDT 10 having a leak path 19 that includes the thickness dimension of a relatively thick spacer 14. Such a spacer is shown joining first and second electrodes 12a, 12b and respective seals 16a, 16b to form a sealed chamber 18. In such a configuration, the electrodes 12a, 12b (with optional emissive coatings 15a, 15b) are spaced apart from each other by a desired gap dimension d. gap It will be appreciated that in such a configuration, the relatively thick spacers 14 will result in the GDT 10 being relatively thick.

[0034] In another example, Figure IB shows a GDT 20 that is thinner than the example of Figure IA. In the example of Figure IB, the spacer 24 is shown to include an inward protrusion such that the leak path length increases for a spacer of reduced thickness. Such a spacer is shown to join the first and second electrodes 22a, 22b and their respective seals 26a, 26b to form a sealed chamber 28. In the example of Figure IB, the electrodes 22a, 22b (with optional emissive coatings 25a, 25b) are spaced apart from the desired gap dimension d due to the reduced spacer thickness. gap 1A) to form a spacer 24 having inward protrusions. Note that in the example of FIG. 1B, the spacers 24 having inward protrusions generally have a more complex shape than, for example, the spacers of FIG. 1A.

[0035] In some embodiments, the GDT can have an increased leak path length while using relatively thin and simple spacer geometries. As described herein, such GDTs can also desirably include relatively simple electrodes.

[0036] 2 shows a GDT 100 having upper and lower electrodes 102a, 102b that may be formed from relatively simple structures such as flat conductive plates. As described herein, the discharge portions of such electrodes may be implemented with one or more layers 105a, 105b formed on the respective flat conductive plates.

[0037] In the example of FIG. 2, each electrode (102a or 102b) has a desired gap dimension d gap When a flat spacer with an aperture is mounted such that the inner wall of the aperture is at or within the edge of the discharge, the resulting leak path length is essentially the thickness of the flat spacer.

[0038] 2, if the inner wall of the opening in the flat spacer 104 is located outside the edge of the discharge portion, the resulting leak path 110 will include a lateral offset (formed by a portion of the respective insulating seal 106a, 106b) from the edge of each discharge portion to the inner wall of the opening in the flat spacer 104 in addition to the thickness of the flat spacer 104. In some embodiments, as described herein, the insulating seal (106a, 106b) associated with each electrode (102a, 102b) can include a surface of insulating material (e.g., glass) to form the above-mentioned lateral offset for the leak path 110.

[0039] In the example of Figure 2, the inner walls of the opening in the spacer 104, portions of the insulating seals 106a, 106b, and the discharge portions of the electrodes 102a, 102b are shown forming a sealed chamber 108. Additional examples related to the GDT 100 of Figure 2 are described in more detail herein.

[0040] 3 and 4 show more detailed examples of the increased leak path length discussed above with reference to FIG. 2. In each of FIGS. 3 and 4, the GDT 100 has a gap dimension d gap 1. The discharge portion of an electrode is shown to include first and second electrodes 102a, 102b disposed relative to one another such that they are separated by a gap 104. For purposes of explanation, it will be understood that the discharge portion of an electrode refers to where a discharge begins or ends at the discharge portion.

[0041] 3 and 4, each of the first and second electrodes 102a, 102b is depicted as including a flat portion and a protruding discharge portion, in some embodiments, such discharge portion may be implemented in one or more layers formed on the flat portion, as described herein.

[0042] 3 and 4, the electrical insulation seal (106a or 106b) (also referred to herein as the insulation seal) can be implemented to occupy a part or all of the space surrounding the lateral outer portion of the corresponding discharge portion. Thus, in some embodiments, the protruding discharge portion and the insulation seal (106a or 106b) can have approximately the same thickness. In such configurations, the electrode (102a or 102b) and the insulation seal (106a or 106b) can form a substantially planar structure. Although some examples are described herein in the context of such a substantially planar structure, it will be understood that the insulation seal can have a thickness that is greater or less than the thickness of the protruding discharge portion.

[0043] It will also be understood that the discharge portion of the electrode may or may not protrude from the conductive surface of the electrode. For example, in some embodiments, a flat portion of the flat conductive surface of the electrode may be surrounded by an electrically insulating seal as described herein, and the exposed portion of such flat conductive surface may be the discharge portion of the electrode. When one or more layers, such as a silver texture layer and an emissive coating layer, are formed on such exposed portion, the resulting layer having a thickness less than, equal to, or greater than the surrounding electrically insulating seal may be considered to be the discharge portion of the electrode.

[0044] 3 and 4, in some embodiments, the GDT 100 can further include a generally planar spacer 104 having an opening that defines a chamber 108. In each of the examples in Figures 3 and 4, the inner wall of the spacer 104 is shown recessed outwardly from the outer edge of the discharge portion of each electrode 102a, 102b. Thus, the resulting recess has a lateral dimension d recess Therefore, if the dimensions of the discharge portions of the electrodes 102a and 102b are similar, the leakage path 110 between the outer edge of one discharge portion to the outer edge of the other discharge portion is approximately d recess +d gap +drecess length.

[0045] It will be appreciated that in some embodiments, the discharge portions of electrodes 102a, 102b may or may not be of the same size.

[0046] FIG. 3 shows that in some embodiments, the spacer 104 can have an outer wall that is approximately flush with the outer walls of the electrodes 102a, 102b.

[0047] FIG. 4 illustrates that in some embodiments, the spacer 104 can have an outer wall that is laterally outboard of the outer walls of the electrodes 102a, 102b. In such a configuration of FIG. 4, the laterally protruding spacer (beyond the outer walls of the electrodes 102a, 102b) can form a wing-like structure when the GDT 100 is viewed from the side. In some embodiments, such a wing-like structure can facilitate some desirable manufacturing processes. Examples of such manufacturing processes are described in more detail herein. It should also be noted that the outer wing-like structure described above can also form a long leak path on the outside of the GDT 100.

[0048] FIG. 5 illustrates a more specific example of the GDT of FIG. 4. In the example of FIG. 5, the GDT 100 is shown to include first and second electrodes 102a, 102b mounted on first and second sides (e.g., upper and lower sides when oriented as in FIG. 5) of an electrically insulating spacer 104. In some embodiments, the first electrode 102a can include a first metal sheet 120a (e.g., a stamped flat metal sheet) on which multiple layers can be formed to provide discharges. For example, a silver ink layer 122a can be formed to substantially cover one side of the metal sheet 120a. A silver texture layer 124a and an emissive coating layer 126a are shown formed on a central portion of the silver ink layer 122a to form a discharge in the central portion of the first electrode 102a. It will be appreciated that such discharge portions may be formed symmetrically about a centerline extending between the first and second electrodes 102a, 102b, or may be formed asymmetrically away from the center portion.

[0049] Similarly, referring to FIG. 5, the second electrode 102b may include a second metal sheet 120b (e.g., a stamped flat metal sheet) on which multiple layers may be formed to provide discharges. For example, a silver ink layer 122b may be formed to substantially cover one side of the metal sheet 120b. A silver texture layer 124b and an emissive coating layer 126b are shown formed on a central portion of the silver ink layer 122b to form discharges in the central portion of the second electrode 102b. It will be appreciated that such discharges may be formed symmetrically about a centerline extending between the first and second electrodes 102a, 102b, or asymmetrically away from the central portion. It will also be appreciated that the individual layers of the second electrode 102b may or may not be the same as the individual layers of the first electrode 102a.

[0050] In some embodiments, an electrode for a GDT having one or more features as described herein (such as the example of FIG. 5) can be implemented as a metal electrode (e.g., copper or 42 alloy metal) without the use of silver ink or texture. In such embodiments, the textured structure can be stamped onto the metal electrode. Such stamping of the textured structure can be done during the formation of the electrode itself (in examples where the electrode is a stamped metal electrode) or in a separate step before or after the electrode formation step. In some embodiments, an emissive coating may or may not be formed on the stamped textured structure of the metal electrode.

[0051] 5, the electrically insulating spacer 104 is shown defining an opening with an inner wall of the spacer 104. In some embodiments, such an electrically insulating spacer may be, for example, a ceramic spacer.

[0052] FIG. 5 shows that in some embodiments, each of the first and second electrodes 102a, 102b can be provided with an electrically insulating seal. For example, the first electrically insulating seal 106a (e.g., a glass seal) can be implemented on the silver ink layer 122a so as to laterally surround the discharge portion including the silver texture layer 124a and the emissive coating layer 126a. In another example, in the context of the stamped metal electrode configuration described above, the first electrically insulating seal 106a (e.g., a glass seal) can be implemented on the metal electrode itself so as to laterally surround the discharge portion including the stamped texture structure and the emissive coating layer (if implemented). Such an electrically insulating seal can be dimensioned such that its inner lateral edge defines the outer edge of the discharge portion and its outer lateral portion engages with a corresponding surface (e.g., an upper surface) of the electrically insulating spacer 104. Thus, the outer edge of the discharge portion of the first electrode 102a is shown laterally separated from the inner wall of the opening in the electrically insulating spacer 104 by the electrically insulating material of the first seal 106a.

[0053] Similarly, a second electrically insulating seal 106b (e.g., a glass seal) can be implemented on the silver ink layer 122b to laterally surround the discharge portion including the silver texture layer 124b and the emissive coating layer 126b. In the context of the stamped metal electrode configuration described above, a second electrically insulating seal 106b (e.g., a glass seal) can be implemented on the metal electrode itself to laterally surround the discharge portion including the stamped texture structure and the emissive coating layer (if implemented). Such an electrically insulating seal can be dimensioned such that its lateral inner edge defines the outer edge of the discharge portion and its lateral outer portion engages a corresponding surface (e.g., a lower surface) of the electrically insulating spacer 104. Thus, the outer edge of the discharge portion of the second electrode 102b is shown to be laterally separated from the inner wall of the opening of the electrically insulating spacer 104 by the electrically insulating material of the second seal 106b. It will be appreciated that the first and second electrically insulating seals 106a, 106b may or may not be the same.

[0054] As configured above, the inner walls of the opening in the spacer 104, the laterally inner portions of the first and second electrically insulating seals 106a, 106b, and the discharge portions of the first and second electrodes 102a, 102b are shown to define a sealed chamber 108. As described herein, such a sealed chamber may be filled with a gas or mixture of gases to provide a desired discharge function.

[0055] 5, the inner walls of the openings in the spacer 104 are shown to be laterally recessed from the outer edges of the first and second discharge portions (e.g., by the lateral dimension of the lateral inner portions of the first and second electrically insulating seals 106a, 106b). Thus, such lateral dimensions associated with each of the first and second electrically insulating seals 106a, 106b can contribute to an increased leak path length between the discharge portions of the first and second electrodes 102a, 102b.

[0056] In the example of Figure 5, the laterally outer portion of the spacer 104 is shown extending laterally beyond the wall defined by the first and second electrodes 102a, 102b. In some embodiments, as described herein, such lateral extension of the spacer 104 can be utilized to facilitate the manufacturing of multiple GDTs. Also, as described herein, the lateral extension of the spacer 104 as an outer wing-like structure can also form a longer leak path outside the corresponding GDT.

[0057] In the example of Figure 5, a single electrically insulating structure (e.g., a glass seal) serves both the sealing function (between one electrode and the corresponding surface of the spacer) and the lateral increase in leak path length (inside and / or outside). In some embodiments, either or both of these functions may be implemented in different ways.

[0058] For example, FIG. 6 illustrates that in some embodiments, the GDT 100 can include separate structures for providing a sealing function and structures for providing a lateral increase in leak path length. In the example of FIG. 6, each of the first and second electrodes 102a, 102b can include a metal sheet (120a or 120b) (e.g., a stamped flat metal sheet) on which one or more layers can be formed to provide a discharge portion. For example, an emissive coating layer (126a or 126b) can be formed on a central portion of the metal sheet (120a or 120b) to form a discharge portion at the central portion of the electrode (102a or 102b). It will be appreciated that such a discharge portion can be formed symmetrically about a centerline extending between the first and second electrodes 102a, 102b, or asymmetrically away from the central portion.

[0059] In the example of FIG. 6, each of the first and second electrodes 102a, 102b may be provided with an electrical insulating layer. For example, a first electrical insulating layer 130a (e.g., a glass layer) may be mounted on the metal sheet 120a so as to laterally surround the discharge portion including the emissive coating layer 126a. Such an electrical insulating layer may be dimensioned to laterally separate the outer edge of the emissive coating layer 126a from the inner wall of the opening defined by the electrically insulating spacer 104. It is noted that the first electrical insulating layer 130a does not provide a sealing function between the electrically insulating spacer 104 and the metal sheet 120a of the first electrode 102a. It is also noted that in some embodiments, the first electrical insulating layer 130a and the electrically insulating spacer 104 may be configured such that the joint between them does not allow a portion of the metal sheet 120a to spill over the joint and damage the leak path. In some embodiments, such a joint may include a configuration in which an outer portion of the first electrically insulating layer 130a sufficiently engages with an inner portion of the electrically insulating spacer 104 to prevent breakdown of a leak path between the first electrically insulating layer 130a and the electrically insulating spacer 104.

[0060] Similarly, a second electrically insulating layer 130b (e.g., a glass layer) can be mounted on the metal sheet 120b to laterally surround the discharge portion including the emissive coating layer 126b. Such an electrically insulating layer can be dimensioned to laterally separate the outer edge of the emissive coating layer 126b from the inner wall of the opening defined by the electrically insulating spacer 104. The second electrically insulating layer 130b can be disposed between the electrically insulating spacer 104 and the first electrically insulating layer 130b. 2 It should be noted that the second electrically insulating layer 130b and the electrically insulating spacer 104 do not provide a sealing function between the metal sheet 120b of the electrode 102b. It should also be noted that in some embodiments, the second electrically insulating layer 130b and the electrically insulating spacer 104 can be configured such that the joint therebetween does not allow a portion of the metal sheet 120b to spill over the joint and damage the leak path. In some embodiments, such a joint can include a configuration in which an outer portion of the second electrically insulating layer 130b sufficiently engages an inner portion of the electrically insulating spacer 104 to prevent damage to the leak path between the second electrically insulating layer 130b and the electrically insulating spacer 104.

[0061] Configured as described above, the first and second electrically insulating layers 130a, 130b can provide a lateral increase in leakage path length between the first and second electrodes 102a, 102b, respectively.

[0062] In the example of Fig. 6, the sealing function is shown to be provided by structures other than the electrical insulating layers 130a, 130b. For example, the sealing assembly between one side (e.g., the upper side when oriented as in Fig. 6) of the electrical insulating spacer 104 and the first metal sheet 120a can include a bonding surface layer 132a (e.g., a CuSil alloy brazing metal) formed on the first metal sheet 120a and a bonding surface layer 134a (e.g., a tungsten metallization layer) formed on the electrical insulating spacer 104. Similarly, the sealing assembly between the other side (e.g., a lower side) of the electrical insulating spacer 104 and the second metal sheet 120b can include a bonding surface layer 132b (e.g., a CuSil alloy brazing metal) formed on the second metal sheet 120b and a bonding surface layer 134b (e.g., a tungsten metallization layer) formed on the electrical insulating spacer 104.

[0063] It should be noted that in the example of Figure 6, each of the sealing assemblies (e.g., 132a / 134a and 132b / 134b) may be conductive or non-conductive. Even if the sealing assembly is conductive, it is electrically isolated from the leakage path between the discharge portions of the two electrodes 102a, 102b.

[0064] In some embodiments, the sealing assemblies described above can provide a sealing function by bonding (e.g., by application of heat) the respective bonding surface layers during the manufacturing process. The inner wall of the spacer 104, the first and second electrically insulating layers 130a, 130b, and the first and second discharge portions are shown to define a sealed chamber 108 when sealed. As described herein, such a sealed chamber can be filled with a gas or mixture of gases to provide a desired discharge function.

[0065] 6, it is noted that the spacer 104 is an electrically insulating spacer (e.g., a ceramic spacer). Thus, the bonding surface layers 132, 134 can be electrically insulating layers, conductive layers, or some combination thereof. It is noted that if the bonding surface layers 132, 134 are formed of a conductive material, such layers can be formed to provide a sealing function but far enough away from the inner walls of the openings in the spacer 104 so as not to interfere with the electrical properties associated with the first and second electrodes 102a, 102b.

[0066] In the examples of Figures 5 and 6, each GDT is configured with a single electrode on one side of the spacer and another single electrode on the other side of the spacer. Figure 7 illustrates that in some embodiments, a GDT having one or more features as described herein can include more than one electrode on a given side of the spacer. Figure 7 also illustrates that in some embodiments, a spacer in a GDT having one or more features as described herein can include more than one layer.

[0067] For example, referring to FIG. 7, two electrodes 102a, 102b are mounted on one side of the spacer assembly (e.g., the upper side when oriented as in FIG. 7) and one electrode 102c is mounted on the other side of the spacer assembly. The spacer assembly is shown to include a first layer 127a and a second layer 127c. Such layers may be electrically insulating layers, such as ceramic layers, and may be joined by a sealing layer 129, such as a glass seal. The first layer 127a is depicted to include a middle portion 127b that supports the laterally separated upper electrodes 102a, 102b. In some embodiments, the middle portion 127b may or may not be connected to the laterally outer portions of the first layer 127a.

[0068] As configured above, the lateral outer portion of each electrode 102a, 102b is shown mating with the outer portion of the first layer 127a, and the lateral inner portion of each electrode 102a, 102b is shown mating with the middle portion 127b. In the example of Figure 7, each of the electrodes 102a, 102b can include individual layers to form the respective discharge portions, similar to the example of Figure 5. Additionally, sealing portions 125a, 125b, similar to the example of Figure 5, can provide sealing functionality and increased leak path length.

[0069] In the example of Figure 7, the lower electrode 102c can be configured in a manner similar to the example of Figure 5 and fitted to the second layer 127c. By configuring as shown in Figure 7, the leakage path associated with any portion of the three example discharges (associated with the three electrodes 102a, 102b, 102c) can be increased by a portion of the respective sealing structure (e.g., 125a or 125c) by forming a lateral offset to the nearest inner wall of the insulating layer (e.g., 127a or 127c).

[0070] In the examples of Figures 5-7, each GDT includes a single sealed chamber. However, it will be understood that a GDT having one or more features as described herein can include two or more sealed chambers. In such configurations having multiple sealed chambers, at least one sealed chamber can be associated with an increased leak path length as described herein.

[0071] Figures 8A-8J illustrate various stages of a process that can be used to manufacture the exemplary GDT 100 of Figure 5. Figures 8A and 8B relate to the electrically insulating spacer 104, Figures 8C-8G relate to each electrode (102a or 102b), and Figures 8H-8J relate to the assembly of the electrodes to the electrically insulating spacer.

[0072] 8A is a side view of an electrically insulating spacer 104 (e.g., a ceramic spacer) having an opening 200. In some embodiments, such openings may be formed in a subsequent step or may be pre-formed. For purposes of illustration in FIGS. 8A-8J, the electrically insulating spacer 104 may be a ceramic spacer, although it will be understood that such electrically insulating spacers may be formed of other materials.

[0073] 8B illustrates forming a glass layer 202a on one side of the ceramic spacer 104 and forming a glass layer 202b on the other side of the ceramic spacer 104 to produce an assembly 204. Examples related to the formation of such glass layers are described in U.S. Patent Application Publication No. 2019 / 0074162, entitled "GLASS SEALED GAS DISCHARGE TUBES," the entirety of which is expressly incorporated herein by reference, the disclosure of which is considered a part of this specification. It will be understood that layers 202a, 202b can be formed of other materials, including non-glass insulating materials.

[0074] 8C is a side view of a metal sheet 120 used as an electrode. In some embodiments, such a metal sheet can be stamped from a larger sheet or strip of metal.

[0075] 8D illustrates the formation of a silver ink layer 122 on one side of the metal sheet 120 to produce the assembly 206. In some embodiments, such a silver ink layer may be formed, for example, by printing or spraying, followed by a curing step. In some embodiments, this step may be omitted in configurations in which the electrodes are implemented as stamped metal structures, as described herein with reference to FIG.

[0076] 8E illustrates forming a glass layer 208 over the silver ink layer 122 to produce assembly 210. In some embodiments, such a glass layer can be formed around the outer edge of the silver ink layer 122 with a width dimension that increases the leak path length as described herein. In some embodiments, as described herein with reference to FIG. 5, the glass layer 208 can be formed around the outer edge of the metal sheet 120 (e.g., directly on the metal sheet 120) in configurations where the electrodes are implemented as stamped metal structures.

[0077] 8F illustrates forming a silver texture layer 124 on the silver ink layer 122 such that it is disposed laterally between the glass layers 122 along the outer edges to produce the assembly 212. In some embodiments, the silver texture layer 124 can be omitted, and instead, a similar texture structure can be formed on the metal sheet 120 (e.g., as a stamped structure) in configurations where the electrodes are implemented as stamped metal structures, as described herein with reference to FIG.

[0078] 8G illustrates forming an emissive coating layer 126 on the silver texture layer 124 (or on the stamped structure of a corresponding stamped metal electrode) so as to be disposed laterally between the glass layers 122 along the outer edges to produce an assembly 214. The assembly 214 can be used as either the first or second electrodes 102a, 102b of the example of FIG.

[0079] Figure 8H is an assembly view of the assembly 204 of Figure 8B being sandwiched between the two assemblies 214a, 214b of Figure 8G. It will be appreciated that in some embodiments, the assemblies 214a, 214b can be mated to the assembly 204 simultaneously, mated to the assembly 204 sequentially, or some combination thereof.

[0080] 81 shows an assembled view of assembly 204 mated with two assemblies 214a, 214b, with mating joints (216a, 216b) yet to be cured and sealed, to produce assembly 220. During or prior to the formation of such an assembly, a desired gas can be introduced into volume 218 to be sealed.

[0081] FIG. 8J shows an assembled view in which the mating joints (216a, 216b in FIG. 8I) have been cured to produce a GDT 100 having a sealed chamber 108 and an increased leak path length that includes a portion of each seal and the inner walls of the opening in the spacer 104, as described herein.

[0082] The example manufacturing steps of Figures 8A-8J are described in the context of a single unit, it will be understood that a GDT having one or more features as described herein can be manufactured as a stand-alone unit, as a single, separate unit from an array of similar units, or any combination thereof.

[0083] Figures 9A-9J and 10A-10J show examples of various stages of a process that can be used to manufacture multiple GDT devices, with Figures 9A-9J being plan views and Figures 10A-10J being side views (and side cross-sectional views where shown) of an array or group of singulated units.

[0084] For purposes of illustration in Figures 9A-9J and 10A-10J, each such GDT device is similar to the exemplary GDT 100 of Figure 5. However, it will be understood that one or more features of such techniques may be used to manufacture GDTs having other configurations.

[0085] Figures 9A, 9B, 10A and 10B relate to the array-wise fabrication of electrically insulating spacers 104. Figures 9C-9G and 10C-10G relate to the array-wise fabrication of electrodes (102a or 102b). Figures 9H-9J and 10H-10J relate to the array-wise assembly of electrodes to electrically insulating spacers.

[0086] FIG. 9A shows a plan view and FIG. 10A shows a cross-sectional side view of an electrically insulating spacer plate 300 (e.g., a ceramic spacer) having a plurality of unsingulated spacer units 104. Each such spacer unit, when singulated, would be similar to the spacer 104 of FIG. 8A. In FIG. 9A, each spacer unit 104 is shown to include an opening 200. In some embodiments, such openings may be formed in a subsequent step or may be pre-formed. For purposes of the discussion of FIGS. 9A-9J and 10A-10J, the electrically insulating spacer plate 300 may be a ceramic spacer plate, although it will be understood that such electrically insulating spacer plates may include other materials.

[0087] In FIG. 10A, the ceramic plate 300 is depicted with boundaries 306 that are the edges of the singulated units. In some embodiments, separation at or near such boundaries can be facilitated by separation structures 302, 304 (e.g., score lines) shown in FIG. 9A. Such separation structures can be formed in a subsequent step, pre-formed, or some combination thereof. In some embodiments, such separation structures can be formed on the ceramic plate 300 using one or more laser beams.

[0088] 9B and 10B show forming a glass layer 202a for each spacer unit 104 on one side of the ceramic spacer plate and forming a glass layer 202b for each spacer unit 104 on the other side of the ceramic spacer plate to produce an assembly 308. Examples relating to the formation of such glass layers are described in the above-mentioned U.S. Patent Application Publication No. 2019 / 0074162. It will be understood that layers 202a, 202b can be formed of other materials, including non-glass insulating materials.

[0089] Fig. 9C shows a plan view and Fig. 10C shows a cross-sectional side view of a metal sheet 310 having a number of single, unseparated units 120. Each such unit is similar to the metal sheet 120 of Fig. 8C and can be used as an electrode.

[0090] 9C and 10C, the metal sheet 310 is depicted as having boundaries 312, 314 that define the edges of the singulated units 120. In some embodiments, the metal sheet 310 can be cut by stamping to form a plurality of singulated units 120.

[0091] 9D and 10D show the step of forming a silver ink layer 122 for each unit 120 on one side of the metal sheet 310 to produce the assembly 316. In some embodiments, such a silver ink layer can be formed, for example, by printing or spraying followed by a curing step. In some embodiments, this step can be omitted in configurations where the electrodes are implemented as stamped metal structures, as described herein with reference to FIG.

[0092] 9E and 10E show forming a glass layer 208 for each unit 120 on the silver ink layer 122 to produce an assembly 322. In some embodiments, such a glass layer can be formed around the periphery of the silver ink layer 122 with a width dimension that increases the leak path length, as described herein. In some embodiments, as described herein with reference to FIG. 5, the glass layer 208 can be formed around the periphery of each unit 120 (e.g., directly on the metal) in configurations where the electrodes are implemented as stamped metal structures.

[0093] 9F and 10F show forming a silver texture layer 124 and an emissive coating layer 126 for each unit 120 on the silver ink layer 122 so as to be disposed laterally between the glass layers 208 along the periphery to produce an assembly 324. In some embodiments, as described herein with reference to FIG. 5, the silver texture layer 124 can be omitted and instead, a similar texture structure (e.g., stamped structure) can be formed on the metal of each unit 120 in configurations where the electrodes are implemented as stamped metal structures.

[0094] 9G and 10G illustrate singulating the assembly 324 of FIG. 9F and FIG. 10F along boundaries 312, 314 to form a plurality of singulated units 214. Each of the singulated units 214 can be used as either the first or second electrodes 102a, 102b of the example of FIG.

[0095] Figures 9H and 10H show assembly diagrams in which each unit 104 of assembly 308 of Figures 9B and 10B is sandwiched between two singulated units 214a, 214b of Figures 9G and 10G to produce assembly 330. It will be appreciated that in some embodiments, singulated units 214a, 214b can be mated to their respective units 104 simultaneously, mated to units 104 sequentially, or some combination thereof.

[0096] 9H and 10H, the mating joints have not yet been cured and sealed. A desired gas can be introduced into the volume 218 associated with each unit 104 during or prior to the sealing process.

[0097] 9I and 10I show an assembled view in which the mating joints have been cured to obtain a plurality of singulated GDT units 220 to produce an assembly 332. Each such unsingulated GDT unit is shown to include a sealed chamber 108 and an increased leak path length that includes a portion of each of the insulating seals 106a, 106b, as described herein.

[0098] 9J and 10J illustrate separating the assembly 332 of FIGs. 9I and 10I along the boundaries (312, 314 of FIG. 9A) to provide a plurality of singulated GDTs 100. Each of the singulated GDTs 100 can be similar to the example of FIG.

[0099] In the examples of Figures 9A-9J and 10A-10J, the lateral shape of the GDT is depicted as rectangular. Such a shape may allow for a single separation of the machined units, for example, by snapping facilitated by score lines on the corresponding spacer plates. Also, such GDTs are depicted as having rectangular chambers and associated electrodes. Thus, in such configurations, the electrical insulation layer that increases the leak path length associated with each electrode may have a rectangular shaped ring surrounding the corresponding discharge portion of the electrode. It will be understood that a GDT having one or more features described herein may include other lateral shapes, including a circular shape. It will also be understood that different portions of a GDT having one or more features as described herein may have different lateral shapes. For example, the spacer may have a rectangular shape and its opening may have a circular shape. In such configurations, the corresponding electrodes and associated portions, such as the insulating seal, may have a circular shape.

[0100] In various examples described with reference to Figures 2-10, a spacer is used between a pair of opposing electrodes, with the thickness of the spacer being part of the leak path length. Such leak path length is shown to be increased by implementing an electrically insulating layer that laterally surrounds the discharge portion of each electrode, thereby increasing the leak path length that represents the dimension between the edge of the discharge portion and the inner wall of the spacer opening. As described herein, such an electrically insulating layer can be configured to provide a sealing function (e.g., as in the example of Figure 5) or can be configured to primarily provide isolation between the discharge portion and the inner wall of the spacer.

[0101] It will thus be appreciated that a GDT having one or more features described herein may have an increased leak path length with or without a spacer between a pair of opposing electrodes. For example, Figures 11-13 show various examples of GDTs each having a sealed chamber formed by a pair of opposing electrodes joined and sealed by a sealing structure without the use of a separate spacer. It should be noted that in some embodiments, such GDT configurations may be desirable with or without increased leak path length.

[0102] FIG. 11A illustrates, in some embodiments, a GDT 400 having flat surfaces facing each other and a gap dimension d gap 11A shows that the semiconductor device may include first and second electrodes 402a, 402b separated by a gap 402b. Such first and second electrodes may be implemented, for example, as flat metal sheets. In the example of FIG. 11A, an electrically insulating sealing structure 406 (e.g., a glass seal) is shown joining and sealing the periphery of the electrodes 402a, 402b to form a sealed chamber 408. Thus, the leak path 409 between the first and second electrodes 402a, 402b is essentially the dimension of the walls of the sealed chamber 408 defined by the insulating sealing structure 406.

[0103] Similarly, FIG. 11B illustrates that in some embodiments, the GDTs 410 have flat surfaces that face each other and have a gap dimension d gap 11B, an electrically insulating sealing structure 416 (e.g., a glass seal) is shown to join and seal the periphery of the electrodes 412a, 412b to form a sealed chamber 418. Thus, the leak path 419 between the first and second electrodes 412a, 412b is essentially the dimension of the wall of the sealed chamber 418 defined by the insulating sealing structure 416. In the example of FIG. 11B, the insulating sealing structure 416 is shown to have a lateral dimension significantly larger than the lateral dimension of the insulating sealing structure 406 of the example of FIG. 11A.

[0104] With reference to the examples of FIG. 11A and FIG. 11B, the respective gap dimensions (d gap ) is similar, the increase in the lateral dimension of the insulating sealing structure alone does not affect the gap dimension (d gap ) does not result in an increase in leak path length. More specifically, in the example of FIG. 11A and FIG. 11B, each GDT has a gap dimension (d gap ) is essentially the same ratio of leak path length (approximately the wall height) to

[0105] FIG. 12A illustrates that in some embodiments, the GDTs 420 have contoured (e.g., concave) surfaces facing each other and a minimum separation gap dimension d gap 12A shows that the semiconductor device may include first and second electrodes 422a, 422b having an insulating seal structure 426 (e.g., a glass seal) that is shown joining and sealing the periphery of the electrodes 422a, 422b to form a sealed chamber 428. Thus, the leak path 429 between the first and second electrodes 422a, 422b is essentially the dimension of the walls of the sealed chamber 428 defined by the insulating seal structure 426.

[0106] Similarly, FIG. 12B illustrates that in some embodiments, the GDTs 430 may have contoured (e.g., concave) surfaces facing each other and a minimum separation gap dimension d gap 12A. In the example of FIG. 12B, an electrically insulating sealing structure 436 (e.g., a glass seal) is shown joining and sealing the periphery of the electrodes 432a, 432b to form a sealed chamber 438. Thus, the leak path 439 between the first and second electrodes 432a, 432b is essentially the dimension of the wall of the sealed chamber 438 defined by the insulating sealing structure 436. In the example of FIG. 12B, the insulating sealing structure 436 is shown to have lateral dimensions significantly larger than the lateral dimensions of the insulating sealing structure 426 of the example of FIG. 12A.

[0107] 12A and 12B, and assuming that the concave surfaces of each GDT have similar dimensions, it can be seen that increasing the lateral dimension of insulating sealing structure 436 in FIG. 12B increases the wall dimension, and therefore the leak path length, of chamber 438 (defined by insulating sealing structure 436) significantly more than the wall dimension / leak path length of the GDT in FIG. 12A. However, in the example of FIG. 12B, the minimum separation gap dimension d gap Also, the minimum separation gap dimension d in the example of FIG. gap Therefore, simply increasing the size of the insulating sealing structure will not reduce the gap size (d gap ) does not necessarily increase the leak path length relative to the gap dimension (d gap ) are similar.

[0108] FIG. 13 illustrates a GDT 440 having an electrode configuration similar to the example of FIGS. 12A and 12B. In the example of FIG. 13, an electrically insulating sealing structure 446 (e.g., a glass seal) is shown joining and sealing the outer periphery of the first and second electrodes 442a, 442b to form a sealed chamber 448. The electrically insulating sealing structure 446 is shown to further include a separate cover portion for each of the first and second electrodes 442a, 442b. More specifically, a first cover portion is shown extending from the sealing portion of the electrically insulating sealing structure 446 to cover at least a portion of the concave shape of the inwardly facing surface of the first electrode 442a. Similarly, a second cover portion is shown extending from the sealing portion of the electrically insulating sealing structure 446 to cover at least a portion of the concave shape of the inwardly facing surface of the second electrode 442b. Thus, the leak path 449 between the first and second electrodes 442a, 442b is shown to include the extended length of each of the first and second coated portions of the electrically insulating sealing structure 446, rather than being essentially similar to the dimensions of a linear wall of the sealed chamber as in the example of FIG. 12B.

[0109] In the example of Figure 13, each concave surface of a respective electrode is shown to include an inner portion (441a or 441b) and an outer portion (443a or 443b). Such inner and outer portions may have a rectilinear shape as shown in Figure 13, however, it will be understood that in some embodiments, either or both of the inner and outer portions may have a curved shape.

[0110] In the example of FIG. 13, each coated portion of the electrically insulating sealing structure 446 extends inwardly to cover the entire outer portion (443a or 443b) and a portion of the inner portion (441a or 441b) to form an exemplary leak path 449, and the ends of the coated portions are spaced apart by a gap dimension d. gap If each covering portion is sized to cover only a portion of the respective outer portion (443a or 443b), the resulting gap dimension d gapNote that φ can be the separation distance between the two electrodes 442a, 442b at the ends of the covered portion. In such a configuration, the resulting ratio of leak path length to gap dimension may or may not be sufficient for a desired GDT configuration.

[0111] Thus, in some embodiments, the electrically insulating sealing structure can include separate covered portions that extend a selected distance along the concave surface of each electrode to provide a desired ratio of leak path length to gap dimension. In some embodiments, each covered portion of the electrically insulating sealing structure can extend partially along the respective outer portion (443a or 443b) of the concave surface, thereby leaving the entire inner portion (441a or 441b) uncovered. In some embodiments, each covered portion of the electrically insulating sealing structure can extend to substantially cover the respective outer portion (443a or 443b) of the concave surface, leaving the inner portion (441a or 441b) substantially uncovered. In some embodiments, each covered portion of the electrically insulating sealing structure can cover the respective outer portion (443a or 443b) of the concave surface and extend to cover a portion of the inner portion (441a or 441b), thereby leaving the remaining portion of the inner portion uncovered.

[0112] Based at least on various examples provided herein, in some embodiments, a gas discharge tube (GDT) can include first and second electrodes, each including an inwardly facing surface, the inwardly facing surfaces of the first and second electrodes facing each other. The GDT can further include a sealing portion implemented to join and seal a portion of an edge of the inwardly facing surfaces of the first and second electrodes to define a sealed chamber between the inwardly facing surfaces of the first and second electrodes. The GDT can further include an electrical insulation layer implemented to cover a portion of each inwardly facing surface of at least one of the first and second electrodes to define a discharge portion on the respective inwardly facing surface not covered by the electrical insulation layer, such that the sealed chamber is further defined by a surface of the electrical insulation layer and the discharge portion of the respective electrode, and further such that a leak path within the sealed chamber includes the surface of the electrical insulation layer and a wall of the sealed chamber.

[0113] It should be noted that in various examples described herein, the sealing portion of the GDT may include a sealing member, and may or may not include a spacer. For example, each of the GDTs shown in Figures 2-7 includes one or more spacers. In such a configuration, the wall of the sealed chamber may include a wall of each opening of the one or more spacers. In another example, the GDT shown in Figure 13 does not include a separate spacer. In such a configuration, the wall of the sealed chamber may include a portion where at least one electrically insulating layer interfaces with the sealing member (e.g., when only one electrically insulating layer is provided) or with another electrically insulating layer (e.g., when both inwardly facing surfaces are provided with an electrically insulating layer).

[0114] It should also be noted that in the various examples depicted in the figures, each of the first and second electrodes is shown to have an electrical insulating layer thereon, thereby increasing the internal leakage path length of the respective GDT, although it will be appreciated that in some embodiments, a GDT having one or more features as described herein may still have its internal leakage path length increased by having only one electrode provided with an electrical insulating layer.

[0115] In some embodiments, a GDT having one or more features described herein may be utilized by itself, for example as a circuit protection device. In some embodiments, a GDT having one or more features as described herein may be combined with other devices or components.

[0116] For example, Figures 14 and 15 illustrate that in some embodiments, a GDT having one or more features as described herein can be combined with one or more electrical devices or components to create a circuit protection device. For example, Figure 14 illustrates a circuit protection 500 in which a GDT 100 is coupled (e.g., in series) to a clamping device 502. Such coupling between the GDT 100 and the clamping device 502 can be via one or more conductive paths (e.g., wires) or such that the two devices are in physical contact with one another.

[0117] 15 shows a circuit protection device 500 in which the GDT 100 is coupled to a first clamp device 502a on one side and a second clamp device 502b on the other side. In some embodiments, such an arrangement can be in series. In some embodiments, such coupling between the GDT 100 and each of the clamp devices 502a, 502b can be via one or more conductive paths (e.g., wires) or such that the coupled devices are in physical contact with each other.

[0118] FIG. 16 shows a circuit protection device 500 that may be a more specific example of the circuit protection device 500 of FIG. 14, and FIG. 17 shows a circuit protection device 500 that may be a more specific example of the circuit protection device 500 of FIG.

[0119] 16 illustrates that in some embodiments, a circuit protection device 500 can include a GDT portion 100 and a varistor portion 502. In some embodiments, such a varistor portion can be configured as a metal oxide varistor (MOV) having a metal oxide layer 512 mounted between an electrode 510 and an electrode 514. The electrode 514 is shown to be a common electrode between the MOV 502 and the GDT 100. Thus, the common electrode 514 is also shown as a first electrode 522a of the GDT 100. The GDT 100 is shown to further include a second electrode 522b such that a sealed chamber 528 exists between the first and second electrodes 522a, 522b.

[0120] In the example of FIG. 16, each of the first and second electrodes 522a, 522b is shown to include a concave surface similar to the example of FIG. 13. Also, similar to the example of FIG. 13, the first and second electrodes 522a, 522b are shown to be joined and sealed by an insulating sealing structure 526 configured to form a separate covering portion on each of the first and second electrodes 522a, 522b. More specifically, a first covering portion 527a is shown to cover an edge portion of the concave surface of the first electrode 522a, and a second covering portion 527b is shown to cover an edge portion of the concave surface of the second electrode 522b. Thus, as described herein, such separate covering portions can provide a desirable increase in the internal leak path length between the first and second electrodes 522a, 522b.

[0121] In the example of Figure 16, the concave surface of each of the first and second electrodes 522a, 522b that is not covered by the respective coating portion (527a or 527b) may be the discharge portion of the respective electrode. As described herein, such discharge portion may or may not include one or more layers (524a, 524b), such as a silver texture layer or an emissive coating layer.

[0122] 16, the common electrode 514 / 522a is shown forming a concave surface of the GDT 100. The other surface of the common electrode 514 / 522a is shown forming a convex surface having an edge portion that flares away from the other electrode 510 of the MOV 502. Such a flared edge configuration can desirably reduce the possibility of damage to the MOV 502 at or near the edge portion.

[0123] 17 shows that in some embodiments, a circuit protection device 500 can include a GDT section 100 and varistor sections on both sides of the GDT section 100. Thus, a first varistor 502a is shown on a first side of the GDT section 100 and a second varistor 502b is shown on a second side of the GDT section 100.

[0124] In some embodiments, each such varistor portion may be configured as a metal oxide varistor (MOV). Thus, a first MOV 502a is shown having a first metal oxide layer 512a implemented between an electrode 510a and an electrode 514a. The electrode 514a is shown to be a common electrode between the MOV 502a and the GDT 100. Thus, the common electrode 514a is also shown as the first electrode 522a of the GDT 100. The GDT 100 is shown to further include a second electrode 522b such that a sealed chamber 528 exists between the first and second electrodes 522a, 522b.

[0125] In the example of FIG. 17, each of the first and second electrodes 522a, 522b is shown to include a concave surface similar to the example of FIG. 13. Also, similar to the example of FIG. 13, the first and second electrodes 522a, 522b are shown to be joined and sealed by an insulating sealing structure 526 configured to form a separate covering portion on each of the first and second electrodes 522a, 522b. More specifically, a first covering portion 527a is shown to cover an edge portion of the concave surface of the first electrode 522a, and a second covering portion 527b is shown to cover an edge portion of the concave surface of the second electrode 522b. Thus, as described herein, such separate covering portions can provide a desirable increase in the internal leak path length between the first and second electrodes 522a, 522b.

[0126] 17, the concave surface of each of the first and second electrodes 522a, 522b that is not covered by the respective coating portion (527a or 527b) may be the discharge portion of the respective electrode. As described herein, such discharge portion may or may not include one or more layers (524a, 524b), such as a silver texture layer or an emissive coating layer.

[0127] In the example of FIG. 17, the first common electrode 514a / 522a is shown forming a concave surface on a first side of the GDT 100, and the second common electrode 514b / 522b is shown forming a concave surface on a second side of the GDT 100. The other side of the first common electrode 514a / 522a is shown forming a convex surface with an edge portion that flares away from the other electrode 510a of the first MOV 502a. Such a flared edge configuration can desirably reduce the possibility of damage to the first MOV 502a at or near the edge portion. Similarly, the other side of the second common electrode 514b / 522b is shown forming a convex surface with an edge portion that flares away from the other electrode 510b of the second MOV 502b. Such a flared edge configuration can desirably reduce the possibility of damage to the second MOV 502b at or near the edge portion.

[0128] For purposes of this description, a concave surface may include a central portion and an edge portion, the edge portion extending parallel to the plane defined by the central portion toward the plane of the side facing the concave surface. Similarly, a convex surface may include a central portion and an edge portion, the edge portion extending parallel to the plane defined by the central portion away from the plane of the side facing the convex surface. An edge portion may include a shape having one or more straight portions, one or more curved portions, or any combination thereof.

[0129] Figures 18A-18H illustrate various stages of a process that may be used to manufacture a plurality of circuit protection devices, such as circuit protection device 500 of Figure 17. In some embodiments, such a fabrication process may include at least some of the process steps being performed while a plurality of units are mounted in an array format.

[0130] 18A illustrates a process step in which a metal oxide plate 552 may be provided or formed. Such a plate is shown to include a number of units 550, each unit ultimately becoming a circuit protection device with the functions of a GDT and MOV.

[0131] In the process step of FIG. 18B, a shaped depression 554 may be formed on one side of the metal oxide 552 of each unit 550 to form an assembly 556.

[0132] In the process step of FIG. 18C, an electrode 558 can be formed on the metal oxide 552 to partially or completely cover the molded recess (554 in FIG. 18B) of each unit 550 to form an assembly 562. In some embodiments, such an assembly can further include an emissive coating 560 formed on a lateral inner portion of the electrode 558. It will be understood that in some embodiments, the emissive coating 560 may or may not be used. It is noted that the electrode 558 includes an inner portion and an outer portion implemented as described herein.

[0133] 18D, a layer 564 of encapsulant may be formed around a periphery of each unit 550 of assembly 562 to form assembly 566. In some embodiments, each such encapsulant layer 564 may be formed of a material that includes glass.

[0134] In the process step of Figure 18E, the two assemblies 566 of Figure 18D can be assembled by joining the inwardly facing portions of the two assemblies (566, 566'). More specifically, a first assembly 566 (similar to assembly 566 of Figure 18D) can be inverted and placed on top of a second assembly 566' (also similar to assembly 566 of Figure 18D).

[0135] In the process step of FIG. 18F, the assembly of FIG. 18E (566 and 566') may be further processed to form the seals 568 and corresponding sealed chambers 570 of each unit to form an assembly 572.

[0136] In the process step of Figure 18G, first and second external electrodes 574, 576 can be formed for each unit on the assembly 572 of Figure 18F to form an assembly 580. In some embodiments, such external electrodes can have a lateral dimension to allow for a single separation of each unit along the score line 578.

[0137] In the process step of FIG. 18H, multiple units of the assembly 580 of FIG. 18G can be separated into multiple separate circuit protection devices 500 having the functions of GDT and MOV, each of which is similar to the circuit protection device 500 of FIG. 17.

[0138] In some examples disclosed herein, including the examples in Figures 9, 10, and 18, a plurality of units are described as being processed while in an array format. For purposes of illustration, an array can include an arrangement of M x N units, where M is an integer equal to or greater than 1, and N is an integer equal to or greater than 1. Such an array of M x N units can be arranged, for example, in a single row array format having a plurality of units in a single row, a single column array format having a plurality of units in a single column, or a rectangular array format having multiple rows and multiple columns. It will be appreciated that an array can also include non-rectangular arrangements of the plurality of units.

[0139] Unless the context clearly requires otherwise, throughout the specification and claims, words such as "comprises," "comprising," and the like, should be interpreted in an inclusive sense, i.e., "including," 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.

[0140] 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.

[0141] 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.

[0142] 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. first and second electrodes, each including an edge and an inwardly facing surface, the inwardly facing surfaces of the first and second electrodes facing one another; a spacer mounted between the first and second electrodes, the spacer having a thickness and formed of an electrically insulating material to provide a first side and a second side and defining an opening having an inner wall extending from the first side to the second side; a sealing portion including a sealing layer mounted between each of the first and second faces of the spacer and a corresponding electrode to bond and seal a portion of the edge of the inwardly facing surfaces of the first and second electrodes to provide a sealed chamber defined between the inwardly facing surfaces of the first and second electrodes and the inner wall of the spacer; an electrical insulator forming a surface within the sealed chamber and mounted to cover a portion of the inwardly facing surface of each of at least one of the first and second electrodes, such that a leak path within the sealed chamber includes the surface of the electrical insulator; and A gas discharge tube (GDT) equipped with a

2. The GDT of claim 1 , wherein the electrically insulating material of the spacer comprises a ceramic material.

3. The GDT of claim 1 , wherein the leak path has a length greater than a thickness dimension of the spacer.

4. The GDT of claim 1 , wherein the leak path has a length that includes the sum of a path associated with each electrical insulation portion and a thickness dimension of the spacer.

5. The GDT of claim 1 , wherein the encapsulation layer is formed of a conductive material.

6. 6. The GDT of claim 5, wherein each electrical insulator extends laterally inward from the inner wall of the opening in the spacer, and each of the sealing layers is separated from the electrical insulator by the electrically insulating material of the spacer.

7. The GDT of claim 1 , wherein the encapsulation layer is formed of an electrically insulating material.

8. The GDT of claim 7 , wherein each of the electrical insulation portions is also formed from the electrical insulation material of the encapsulation layer.

9. The GDT of claim 8 , wherein each of the electrical insulation and encapsulation layers forms a continuous structure.

10. The GDT of claim 7 , wherein the electrically insulating material of the sealing layer comprises glass.

11. The GDT of claim 1 , wherein the spacer is sized to extend laterally from the inner wall to an outer wall that is generally coplanar with outer edges of the first and second electrodes.

12. The GDT of claim 1 , wherein the spacer is sized to extend laterally from the inner wall to an outer wall laterally beyond outer edges of the first and second electrodes.

13. 13. The GDT of claim 12, wherein the spacer includes a notch structure at a corner of the outer wall of at least one of the first and second sides, the notch structure resulting in separation of the spacer from other spacers.

14. 13. The GDT of claim 12, wherein the spacer extends laterally beyond the outer edges of the first and second electrodes to increase an external leakage path length between the first and second electrodes.

15. A method for manufacturing a semiconductor device comprising: first and second electrodes, each including an edge and an inwardly facing surface, the inwardly facing surfaces of the first and second electrodes facing each other; a sealing portion implemented to bond and seal portions of the edges of the inwardly facing surfaces of the first and second electrodes to define a sealed chamber between the inwardly facing surfaces of the first and second electrodes, the sealing portion being formed of an electrically insulating material and configured to directly bond and seal the first and second electrodes without a spacer; an electrical insulator forming a surface within the sealed chamber and mounted to cover a portion of the inwardly facing surface of each of at least one of the first and second electrodes, such that a leak path within the sealed chamber includes the surface of the electrical insulator; and A gas discharge tube (GDT) equipped with a

16. The GDT of claim 15 , wherein each electrical insulator is also formed from the electrical insulator material of the encapsulation portion.

17. The GDT of claim 16, wherein each electrically insulating portion extends laterally inward from the sealing portion.

18. 17. The GDT of claim 16, wherein the electrical insulation portion and the sealing portion form a continuous structure.

19. The GDT of claim 16 , wherein the electrically insulating material of the seal comprises glass.

20. The GDT of claim 1 , wherein each of the first and second electrodes is formed from a metal layer.

21. 21. The GDT of claim 20, wherein each electrical insulation portion is sized to expose a discharge portion on the inwardly facing surface of the respective electrode.

22. 22. The GDT of claim 21, wherein the discharge portion of the electrode includes one or more layers mounted on the inwardly facing surface of the metal layer.

23. 23. The GDT of claim 22, wherein the one or more layers mounted on the inwardly facing surface of the metal layer include a silver ink layer.

24. 24. The GDT of claim 23, wherein the one or more layers mounted on the inwardly facing surface of the metal layer further comprises a silver texture layer on the silver ink layer.

25. 25. The GDT of claim 24, wherein the one or more layers mounted on the inwardly facing surface of the metal layer further comprises an emissive coating layer on the silver texture layer.

26. 22. The GDT of claim 21, wherein the discharge portion of the electrode includes a textured structure formed on the inwardly facing surface of the metal layer.

27. 27. The GDT of claim 26, wherein the textured structure comprises a stamped metal structure formed on the metal layer.

28. 30. The GDT of claim 27, wherein the discharge portion of the electrode further comprises an emissive coating layer on the textured structure.

29. 22. The GDT of claim 21, wherein the discharge portion and the portion of each of the inwardly facing surfaces covered by the electrical insulation portion are substantially flat.

30. The GDT of claim 15 , wherein the portions of each of the inwardly facing surfaces form a concave surface.

31. 31. The GDT of claim 30, wherein the concave surface includes a substantially flat inner portion and an angled outer portion, such that at least a portion of the angled outer portion is covered by the respective electrical insulation.

32. 32. The GDT of claim 31, wherein substantially all of the angled outer portion is covered by the respective electrical insulation.

33. forming or providing first and second electrodes, each including an edge and an inwardly facing surface; forming or providing a spacer dimensioned to be mounted between the first and second electrodes, the spacer being formed of an electrically insulating material having a thickness to provide a first side and a second side and defining an opening having an inner wall extending from the first side to the second side; covering a portion of the inwardly facing surface of each of the first and second electrodes with an electrically insulating material; bonding and sealing portions of the edges of each of the inwardly facing surfaces of the first and second electrodes with a sealing layer to each of the first and second sides of the spacer to provide a sealed chamber defined between the inwardly facing surfaces of the first and second electrodes and the inner wall of the spacer, such that a leak path within the sealed chamber includes a surface of electrically insulating material of the portions covering the inwardly facing surfaces of each of the electrodes; 1. A method for manufacturing a gas discharge tube (GDT), comprising:

34. A method of manufacturing a semiconductor device comprising: forming or providing first and second electrodes, each of the first and second electrodes including an edge and an inwardly facing surface; covering a portion of the inwardly facing surface of each of the first and second electrodes with an electrically insulating material; bonding and sealing portions of the edges of the inwardly facing surfaces of the first and second electrodes to define a sealed chamber between the inwardly facing surfaces of the first and second electrodes, wherein a leak path within the sealed chamber includes a surface of an electrically insulating material, forming an electrical insulator that directly bonds and seals the first and second electrodes without a spacer; A method for manufacturing a gas discharge tube (GDT), comprising:

35. providing or forming an electrically insulating plate defining an array of spacer units, each spacer unit having a first and second surface and defining an aperture having an inner wall extending from the first surface to the second surface; forming or providing a metal sheet having an array of electrode units to provide first and second electrodes, each electrode including an edge and an inwardly facing surface; covering a portion of the inwardly facing surface of each of at least one of the first and second electrodes with an electrically insulating material; sealing the opening of each spacer unit with the first and second electrodes, wherein portions of the edges of the inwardly facing surfaces of the first and second electrodes define a sealed chamber between the inwardly facing first and second electrodes and such that a leak path within the sealed chamber includes a surface of an electrically insulating material; A method for manufacturing a plurality of gas discharge tubes (GDTs), comprising:

36. 36. The method of claim 35, further comprising separating the array of spacer units into a plurality of separate units.

37. A gas discharge tube (GDT) including first and second electrodes each including an edge and an inwardly facing surface, the inwardly facing surfaces of the first and second electrodes facing one another, the GDT further including a spacer mounted between the first and second electrodes, the spacer having a thickness and formed of an electrically insulating material to provide a first side and a second side and defining an opening having an inner wall extending from the first side to the second side, the GDT defining a sealed chamber defined between the inwardly facing surfaces of the first and second electrodes and the inner wall of the spacer. the GDT further comprising a sealing portion including a sealing layer mounted between each of the first and second surfaces of the spacer and a corresponding one of the electrodes to bond and seal a portion of the edge of the inwardly facing surfaces of the first and second electrodes to provide a barrier, the GDT further comprising an electrical insulator formed in the sealed chamber and mounted to cover a portion of the inwardly facing surface of at least one of the first and second electrodes, the electrical insulator being mounted such that a leak path within the sealed chamber includes the surface of the electrical insulator; a first clamping device electrically connected to the first electrode of the GDT; A circuit protection device comprising:

38. 38. The circuit protection device of claim 37, wherein the first clamping device is connected directly to the first electrode.

39. 40. The circuit protection device of claim 38, wherein the first clamp device is a metal oxide varistor (MOV) having first and second electrodes and a metal oxide layer mounted between the first and second electrodes.

40. 40. The circuit protection device of claim 39, wherein one of the first and second electrodes of the MOV is configured as a terminal of the circuit protection device, and the other electrode of the MOV is another electrode electrically connected to the first electrode of the GDT.

41. 40. The circuit protection device of claim 39, wherein one of the first and second electrodes of the MOV is configured as a terminal of the circuit protection device and the first electrode of the GDT is configured as the other electrode of the MOV.

42. 38. The circuit protection device of claim 37, further comprising a second clamp device electrically connected to the second electrode of the GDT.

43. 43. The circuit protection device of claim 42, wherein the second clamp device is a metal oxide varistor (MOV) having first and second electrodes and a metal oxide layer mounted between the first and second electrodes.

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