Metal oxide-polyaniline polymer matrix piezoresistor

Abstract

A method of making a metal oxide varistor (MOV), the method comprising placing an amount of an MOV composition in a stamper, the MOV composition comprising metal oxide particles mixed with a polyaniline-polymer; performing a pressing operation including operating a press mold to press the MOV composition into a solid MOV sheet; and applying a first electrode and a second electrode to the opposing first and second sides of the MOV sheet, wherein the pressing operation is performed at a temperature in the range of 15 DEG C to 200 DEG C.

Description

Technical Field

[0001] The present disclosure generally relates to the field of circuit protection devices. More specifically, the present disclosure relates to a metal oxide varistor that can be produced using a low temperature process and is resistant to thermal shock. Background Art

[0002] Metal oxide varistors (MOVs) are voltage-dependent, non-linear devices that provide transient voltage suppression in electronic circuits. MOVs have a high resistance when subjected to low voltages, and a low resistance when subjected to high voltages. When connected in parallel with the circuit component being protected, in the event of a high transient voltage in the circuit, the MOV can clamp the voltage to a safe level. Thus, the MOV absorbs energy that would otherwise damage the protected component.

[0003] Conventional MOV sheets are made of a composition of metal oxide particles embedded in a ceramic matrix. A disadvantage associated with such MOV compositions is that they must undergo a sintering process performed at very high temperatures to form the sheet. In addition, the ceramic matrix is ​​brittle and susceptible to cracking if subjected to thermal shock, which can occur during abnormal overvoltage events. This can lead to overheating and combustion.

[0004] It is desirable to provide an MOV sheet that can be manufactured using low temperatures (eg, room temperature). It is also desirable to provide an MOV sheet that is resistant to thermal shock.

[0005] It is with respect to these and other considerations that improvements of the present invention may be useful. Summary of the invention

[0006] This summary is provided to introduce a series of concepts in a simplified form that will be further described in the detailed description below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to assist in determining the scope of the claimed subject matter.

[0007] A metal oxide varistor (MOV) according to an embodiment of the present disclosure includes a MOV sheet, a first electrode disposed on a first side of the MOV sheet, and a second electrode disposed on a second side of the MOV sheet, wherein the MOV sheet is formed of a MOV composition including metal oxide particles embedded in a polyaniline-polymer matrix.

[0008] A method of manufacturing a metal oxide varistor (MOV) according to an embodiment of the present disclosure includes: placing a certain amount of an MOV composition in a die, the MOV composition including metal oxide particles mixed with a polyaniline-polymer; performing a pressing operation, the pressing operation including operating the die to press the MOV composition into a solid MOV sheet; and applying a first electrode and a second electrode to opposite first and second sides of the MOV sheet, wherein the pressing operation is performed at a temperature in the range of 15°C to 200°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] By way of example, various embodiments of the present disclosure will now be described with reference to the accompanying drawings, in which:

[0010] Figure 1A is a front perspective view showing an MOV according to an embodiment of the present disclosure;

[0011] Figure 1B It is shown Figure 1A Rear perspective view of the MOV;

[0012] Figure 1C is shown with a polymer coating Figure 1A A rear perspective view of the MOV; and

[0013] Figures 2A-2F is a series of perspective views illustrating a method of manufacturing an MOV according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0014] As used herein, unless otherwise specified, elements or operations that are described in singular form and begin with the word "a" or "an" should be understood to include plural elements or operations. In addition, various embodiments have been described herein in the context of one or more elements or parts. Elements or parts may include any structure that is arranged to perform certain operations. Although embodiments may be described by way of example with a limited number of elements in a specific topology, embodiments may include more or less elements in an alternative topology according to the needs of a given implementation. Note that any reference to "one embodiment" or "embodiment" means that the specific features, structures or characteristics described in conjunction with the embodiment are included in at least one embodiment. The phrases "in one embodiment", "in some embodiments" and "in various embodiments" that appear in different positions in the specification do not necessarily all refer to the same embodiment.

[0015] Embodiments of metal oxide varistors (MOVs) and methods of making the same according to the present disclosure will now be described more fully with reference to the accompanying drawings, in which preferred embodiments of the present disclosure are presented. However, MOVs and methods of making the same may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will convey certain aspects of the MOVs and methods of making the same to those skilled in the art. In the drawings, unless otherwise specified, the same numerals always represent the same elements.

[0016] refer to Figure 1A and 1B , showing a perspective front view and a perspective rear view of a metal oxide varistor (MOV) 10 according to the present disclosure. For convenience and clarity, terms such as "front", "rear", "top", "bottom", "up", "down", "above", "below", etc. may be used herein to describe the relative positions and orientations of various components of the MOV 10, each component relative to the geometry and orientation of the MOV 10, such as Figure 1A The terminology will include the words specifically mentioned, derivatives thereof and words of similar import.

[0017] refer to Figure 1A and Figure 1B , the MOV 10 may include a MOV sheet 12 having substantially identical first and second electrodes 14a, 14b disposed on opposite front and rear sides thereof. The first and second electrodes 14a, 14b may be formed of any suitable conductive material, including but not limited to copper, copper alloys, aluminum, aluminum coated with copper, silver, tin, nickel, etc., and may be attached to the MOV sheet 12 by cold pressing, brazing, conductive adhesives, etc., or deposited on the MOV sheet by sputtering. The present disclosure is not limited thereto. The MOV sheet 12 and the first and second electrodes 14a, 14b are depicted as being generally circular, but this is not critical. It is contemplated that one or more of the MOV sheet 12 and the first and second electrodes 14a, 14b may have different shapes, such as rectangular, triangular, irregular, etc., without departing from the scope of the present disclosure.

[0018] The MOV 10 may also include conductive first and second leads 15 and 16 connected to the first and second electrodes 14a and 14b, respectively, for facilitating electrical connection of the MOV 10 within a circuit. In various non-limiting embodiments, the first and second leads 15 and 16 may be formed of copper, tin, silver, etc., and may be electrically connected to the first and second electrodes 14a and 14b by soldering, welding, conductive adhesives, etc. The present disclosure is not limited thereto.

[0019] refer to Figure 1C, the MOV 10 may further include a dielectric polymer coating 20 covering the MOV sheet 12, the first and second electrodes 14a and 14b, and a portion of the first and second leads 15 and 16. The polymer coating 20 may protect the covered components of the MOV 10 from environmental factors and may prevent electrical shorts between the MOV 10 and surrounding circuit components.

[0020] The MOV sheet 12 can be formed from an MOV composition that is suitable for resisting thermal shock and can be formed into sheets using a low temperature process, as further described below. For example, the MOV composition can include metal oxide particles (e.g., zinc oxide particles) embedded in a polyaniline-polymer matrix. Through testing, it was found that the polyaniline-polymer matrix of the present disclosure is much stronger and less prone to cracking when subjected to abnormal overvoltage conditions relative to the ceramic matrix used in conventional MOV sheets. Therefore, the risk of catastrophic failure (e.g., combustion) is greatly reduced relative to conventional MOV sheets.

[0021] refer to Figures 2A-2F , a series of perspective views illustrating an exemplary method of manufacturing the above-described MOV 10 according to the present disclosure are shown. Figures 1A-1C The method is described with reference to the diagram of the MOV 10 presented in FIG.

[0022] exist Figure 2A In the embodiment of the present invention, a certain amount of the above MOV composition (hereinafter referred to as "MOV composition 22") can be placed in a die 24. The MOV composition 22 can be a powder or a particle mixture including metal oxide particles (e.g., zinc oxide particles) mixed with a polyaniline-polymer. Figure 2B In the embodiment of the present invention, the die 24 can be operated to press the MOV composition 22 into a solid MOV sheet 12. This process can be carried out at relatively low temperatures (e.g., between 15°C and 200°C), without the need for high temperatures (e.g., 1500°C to 1700°C) typically associated with sintering processes used to form MOV sheets from traditional MOV compositions (i.e., metal oxide particles embedded in a ceramic matrix). The thickness of the MOV sheet 12 can be determined by the density and weight of the MOV composition 22 and the pressure applied by the die 24. By varying the ratio of the metal oxide and the polyaniline-polymer in the MOV composition 22, the robustness and breakdown voltage of the MOV sheet 12 can be easily adjusted.

[0023] refer to Figure 2C , the MOV sheet 12 can be removed from the die 24, as Figure 2DAs shown, the first electrode 14a and the second electrode 14b can be applied to the opposite front and back sides of the MOV sheet 12 (the first electrode 14a is shown applied to the front side of the MOV sheet 12, and the second electrode 14b is shown in the process of being applied to the back side of the MOV sheet 12). In various embodiments, for example, the first electrode 14a and the second electrode 14b can be applied to the opposite front and back sides of the MOV sheet 12 using a cold press process or a sputtering process. The present disclosure is not limited thereto.

[0024] refer to Figure 2E , the conductive first lead 15 and the second lead 16 can be connected to the first electrode 14a and the second electrode 14b, respectively (the first lead 15 is shown connected to the first electrode 14a, and the second lead 16 is shown in the process of being connected to the second electrode 14b). In various non-limiting embodiments, the first lead 15 and the second lead 16 can be electrically connected to the first electrode 14a and the second electrode 14b by soldering, welding, a conductive adhesive, etc. The present disclosure is not limited thereto.

[0025] refer to Figure 2F , a dielectric polymer coating 20 may be applied to the MOV sheet 12, the first electrode 14a and the second electrode 14b, and a portion of the first lead 15 and the second lead 16. The polymer coating 20 may protect the covered parts of the MOV 10 from environmental factors and may prevent electrical shorts between the MOV 10 and surrounding circuit components. In various embodiments, the dielectric polymer coating 20 may be applied using a conventional dipping process. The present disclosure is not limited thereto.

[0026] Those of ordinary skill in the art will appreciate that the above-described MOV 10 and associated methods of manufacture provide a number of advantages. For example, the above-described MOV composition 22 including a polyaniline-polymer matrix is ​​much stronger and less prone to cracking when subjected to abnormal overvoltage conditions, relative to the ceramic matrix used in conventional MOV sheets. As a result, the risk of catastrophic failure (e.g., combustion) is greatly reduced relative to conventional MOV sheets. In addition, the MOV composition 22 can be formed into MOV sheets using a pressing process performed at low temperatures, avoiding the need for a high-temperature sintering process that is typically used to form MOV sheets from conventional MOV compositions (i.e., metal oxide particles embedded in a ceramic matrix). In addition, the robustness and breakdown voltage of the MOV sheet 12 of the present disclosure can be easily adjusted by varying the ratio of metal oxide to polyaniline-polymer in the MOV composition 22.

[0027] As used herein, an element or step recited in the singular and preceded by the word "a" or "an" should be understood as not excluding plural elements or steps, unless such exclusion is explicitly stated. In addition, reference to "one embodiment" of the present disclosure is not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the described features.

[0028] Although the present disclosure has mentioned certain embodiments, many modifications, substitutions and changes to the described embodiments are possible without departing from the field and scope of the present disclosure as defined by the appended claims. Therefore, it is intended that the present disclosure is not limited to the described embodiments, but has the full scope defined by the following claims and their equivalent language.

Claims

1. A metal oxide varistor (MOV), comprising: MOV film; a first electrode disposed on a first side of the MOV sheet; and a second electrode disposed on a second side of the MOV sheet; The MOV sheet is formed from a MOV composition comprising metal oxide particles embedded in a polyaniline-polymer matrix. 2 . The MOV of claim 1 , further comprising conductive first and second leads connected to the first and second electrodes, respectively.

3. The MOV of claim 2, further comprising a dielectric polymer coating covering the MOV sheet, the first and second electrodes, and a portion of the first and second leads.

4. The MOV of claim 1, wherein the first electrode and the second electrode are formed of one of copper, a copper alloy, aluminum, aluminum coated with copper, silver, tin, and nickel. The MOV of claim 1 , wherein the metal oxide particles are zinc oxide particles.

6. A metal oxide varistor (MOV) composition comprising metal oxide particles mixed with a polyaniline-polymer.

7. The MOV composition of claim 6, wherein the metal oxide particles are zinc oxide particles.

8. A method of manufacturing a metal oxide varistor (MOV), the method comprising: placing an amount of an MOV composition comprising metal oxide particles mixed with a polyaniline-polymer in a compression mold; performing a compression operation, including operating the compression mold to compress the MOV composition into a solid MOV tablet; and First and second electrodes are applied to opposing first and second sides of the MOV sheet.

9. The method of claim 8, wherein the metal oxide particles are zinc oxide particles.

10. The method of claim 8, wherein the pressing operation is performed at a temperature ranging from 15°C to 200°C.

11. The method of claim 8, wherein the first and second electrodes are applied to the MOV sheet using one of a cold pressing method and a sputtering method. 12 . The method of claim 8 , further comprising applying conductive first and second leads to the first and second electrodes, respectively.

13. The method of claim 8, further comprising covering the MOV sheet, the first and second electrodes, and a portion of the first and second leads with a dielectric polymer coating.

14. The method of claim 8, wherein the first electrode and the second electrode are formed of one of copper, a copper alloy, aluminum, aluminum coated with copper, silver, tin, and nickel.

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