METAL OXIDE-POLYANILINE POLYMER MATRIX VARISTOR

Abstract

A method of manufacturing a metal oxide varistor (MOV), the method including placing a quantity of a MOV composition in a pressing die, the MOV composition including metal oxide granules mixed with a polyaniline-polymer, performing a pressing operation including operating the pressing die to compress the MOV composition into a solid MOV chip, and applying first and second electrodes to opposing first and second sides of the MOV chip, wherein the pressing operation is performed at a temperature in a range of 15 degrees Celsius to 200 degrees Celsius.

Claims

1. A metal oxide varistor (MOV) comprising: a MOV chip; a first electrode disposed on a first side of the MOV chip; and a second electrode disposed on a second side of the MOV chip; wherein the MOV chip is formed of a MOV composition comprising metal oxide granules embedded in a polyaniline-polymer matrix.

2. The MOV of claim 1, further comprising electrically 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 chip, the first and second electrodes, and portions of the first and second leads.

4. The MOV of claim 1, where the first and second electrodes are formed of one of copper, copper alloy, aluminum, aluminum covered with copper, silver, tin, and nickel.

5. The MOV of claim 1, further comprising electrically conductive first and second leads connected to the first and second electrodes, respectively.

6. The MOV of claim 1, wherein the metal oxide granules are zinc oxide granules.

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

8. The MOV composition of claim 7, wherein the metal oxide granules are zinc oxide granules.

9. A method of manufacturing a metal oxide varistor (MOV), the method comprising: placing a quantity of a MOV composition in a pressing die, the MOV composition comprising metal oxide granules mixed with a polyaniline-polymer; performing a pressing operation including operating the pressing die to compress the MOV composition into a solid MOV chip; and applying first and second electrodes to opposing first and second sides of the MOV chip.

10. The method of claim 9, wherein the metal oxide granules are zinc oxide granules.

11. The method of claim 9, wherein the pressing operation is performed at a temperature in a range of 15 degrees Celsius to 200 degrees Celsius.

12. The method of claim 9, wherein the first and second electrode are applied to the MOV chip using one of a cold pressing process and a sputtering process.

13. The method of claim 9, further comprising applying electrically conductive first and second leads to the first and second electrodes, respectively.

14. The method of claim 9, further comprising covering the MOV chip, the first and second electrodes, and portions of the first and second leads with a dielectric polymer coating.

15. The method of claim 9, where the first and second electrodes are formed of one of copper, copper alloy, aluminum, aluminum covered with copper, silver, tin, and nickel.

Description

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, wherein:

[0010] FIG. 1A is a front perspective view illustrating a MOV in accordance with an embodiment of the present disclosure;

[0011] FIG. 1B is a rear perspective view illustrating the MOV of FIG. 1A;

[0012] FIG. 1C is a rear perspective view illustrating the MOV of FIG. 1A with a polymer coating; and

[0013] FIGS. 2A-2F are a series of perspective views illustrating a method of manufacturing a MOV in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0014] As used herein, an element or operation recited in the singular and proceeded with the word a or an are understood as possibly including plural elements or operations, except as otherwise indicated. Furthermore, various embodiments herein have been described in the context of one or more elements or components. An element or component may comprise any structure arranged to perform certain operations. Although an embodiment may be described with a limited number of elements in a certain topology by way of example, the embodiment may include more or less elements in alternate topologies as desired for a given implementation. Note any reference to one embodiment or an embodiment means a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrases in one embodiment, in some embodiments, and in various embodiments in various places in the specification are not necessarily all referring to the same embodiment.

[0015] Embodiments of a metal oxide varistor (MOV) and a method of manufacturing the same in accordance with 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. The MOV and the method of manufacture may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will convey certain aspects of the MOV and the method of manufacture to those skilled in the art. In the drawings, like numbers refer to like elements throughout unless otherwise noted.

[0016] Referring to FIGS. 1A and 1B, perspective front and rear views of a metal oxide varistor (MOV) 10 in accordance with the present disclosure are shown. For the sake of convenience and clarity, terms such as front, rear, top, bottom, up, down, above, below, etc. may be used herein to describe the relative placement and orientation of various components of the MOV 10, each with respect to the geometry and orientation of the MOV 10 as it appears in FIG. 1A. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.

[0017] Referring to FIGS. 1A and 1B, the MOV 10 may include a MOV chip 12 having substantially identical first and second electrodes 14a, 14b disposed on opposing front and rear sides thereof. The first and second electrodes 14a, 14b may be formed of any suitable, electrically conductive material, including, but not limited to, copper, copper alloy, aluminum, aluminum covered with copper, silver, tin, nickel, etc., and may be affixed to the MOV chip 12 by cold pressing, solder, electrically conductive adhesive, etc., or deposited on the MOV chip by sputtering. The present disclosure is not limited in this regard. The MOV chip 12 and the first and second electrodes 14a, 14b are depicted as being generally circular in shape, but this is not critical. It is contemplated that one or more of the MOV chip 12 and the first and second electrodes 14a, 14b may have a different shape, such as rectangular, triangular, irregular, etc. without departing from the scope of the present disclosure.

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

[0019] Referring to FIG. 1C, the MOV 10 may further include a dielectric polymer coating 20 that covers the MOV chip 12, the first and second electrodes 14a, 14b, and portions of the first and second leads 15, 16. The polymer coating 20 may protect the covered components of the MOV 10 from environmental elements and may prevent electrical shorting between the MOV 10 and surrounding circuit components.

[0020] The MOV chip 12 may be formed of a MOV composition that is adapted to resist thermal shock and that can be formed into a chip using low temperature processes as further described below. For example, the MOV composition may include metal oxide granules (e.g., zinc oxide granules) embedded in a polyaniline-polymer matrix. It has been found through testing that the polyaniline-polymer matrix of the present disclosure is far more robust and far less susceptible to cracking when subjected to abnormal overvoltage conditions relative to ceramic matrices used in conventional MOV chips. The risk of catastrophic failure (e.g., combustion) is therefore greatly mitigated relative to conventional MOV chips.

[0021] Referring to FIG. 2A-2F, a series of perspective view illustrating an exemplary method for manufacturing the above-described MOV 10 in accordance with the present disclosure is shown. The method will now be described in conjunction with the illustrations of the MOV 10 presented in FIGS. 1A-1C.

[0022] In FIG. 2A, a quantity of the above-described MOV composition (hereinafter the MOV composition 22) may be placed in a pressing die 24. The MOV composition 22 may be a powder or granular mixture that includes metal oxide granules (e.g., zinc oxide granules) mixed with a polyaniline-polymer. In FIG. 2B, the pressing die 24 may be operated to compress the MOV composition 22 into a solid MOV chip 12. This process can be performed at relatively low temperatures (e.g., between 15 degrees Celsius and 200 degrees Celsius), and does not require high temperatures (e.g., 1500 degrees Celsius to 1700 degrees Celsius) typically associated with sintering processes that are used to form MOV chips from conventional MOV compositions (i.e., metal oxide granules embedded in a ceramic matrix). The thickness of the MOV chip 12 may be determined by the density and weight of the MOV composition 22 as well as the pressure applied by the pressing die 24. The robustness and breakdown voltage of the MOV chip 12 can be easily tuned by varying the ratio of metal oxide and polyaniline-polymer in the MOV composition 22.

[0023] Referring to FIG. 2C, the MOV chip 12 may be removed from the pressing die 24 and, as shown in FIG. 2D, the first and second electrodes 14a, 14b may be applied to opposing front and rear sides of the MOV chip 12 (the first electrode 14a is shown applied to the front side of the MOV chip 12, and the second electrode 14b is shown in the process of being applied to the rear side of the MOV chip 12). In various embodiments, the first and second electrodes 14a, 14b may be applied to the opposing front and rear sides of the MOV chip 12 using a cold pressing process or a sputtering process, for example. The present disclosure is not limited in this regard.

[0024] Referring to FIG. 2E, the electrically conductive first and second leads 15, 16 may be connected to the first and second electrodes 14a, 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 and second leads 15, 16 may be electrically connected to the first and second electrodes 14a, 14b via soldering, welding, electrically conductive adhesive, etc. The present disclosure is not limited in this regard.

[0025] Referring to FIG. 2F, the dielectric polymer coating 20 may be applied to the MOV chip 12, the first and second electrodes 14a, 14b, and portions of the first and second leads 15, 16. The polymer coating 20 may protect the covered components of the MOV 10 from environmental elements and may prevent electrical shorting 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 in this regard.

[0026] Those of ordinary skill in the art will appreciate that the above-described MOV 10 and associated method of manufacture provide numerous advantages. For example, the above-described MOV composition 22, which includes a polyaniline-polymer matrix, is far more robust and far less susceptible to cracking when subjected to abnormal overvoltage conditions relative to ceramic matrices used in conventional MOV chips. The risk of catastrophic failure (e.g., combustion) is therefore greatly mitigated relative to conventional MOV chips. Additionally, the MOV composition 22 can be formed into a MOV chip using a pressing process performed at low temperatures, avoiding the need for high-temperature sintering processes that are typically employed to form MOV chips from conventional MOV compositions (i.e., metal oxide granules embedded in a ceramic matrix). Still further, the robustness and breakdown voltage of the MOV chip 12 of the present disclosure can be easily tuned by varying the ratio of metal oxide and polyaniline-polymer in the MOV composition 22.

[0027] As used herein, an element or step recited in the singular and proceeded with the word a or an should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to one embodiment of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

[0028] While the present disclosure makes reference to certain embodiments, numerous modifications, alterations and changes to the described embodiments are possible without departing from the sphere and scope of the present disclosure, as defined in the appended claim(s). Accordingly, it is intended that the present disclosure not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof.