US-12626842-B2 - 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.

Inventors

• OLUWASEUN KEHINDE OYEWOLE
• Marco Doms

Assignees

• LITTELFUSE, INC.

Dates

Publication Date

20260512

Application Date

20230809

Claims (9)

1. 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; electrically conductive first and second leads connected to the first electrode and the second electrode, respectively; wherein the MOV chip is formed of a MOV composition comprising metal oxide granules embedded in a polyaniline-polymer matrix, wherein the metal oxide granules are zinc oxide granules and further comprising a dielectric polymer coating covering the MOV chip, the first and second electrodes, and portions of the first and second leads.
2. 2 . The MOV of claim 1 , where the first electrode and the second electrode are formed of one of copper, copper alloy, aluminum, aluminum covered with copper, silver, tin, and nickel.
3. 3 . A metal oxide varistor (MOV) composition comprising metal oxide granules mixed with a polyaniline-polymer, wherein the metal oxide granules are zinc oxide granules.
4. 4 . 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, wherein the metal oxide granules are zinc oxide granules.
5. 5 . The method of claim 4 , wherein the pressing operation is performed at a temperature in a range of 15 degrees Celsius to 200 degrees Celsius.
6. 6 . The method of claim 4 , wherein the first and second electrode are applied to the MOV chip using one of a cold pressing process and a sputtering process.
7. 7 . The method of claim 4 , further comprising applying electrically conductive first and second leads to the first and second electrodes, respectively.
8. 8 . The method of claim 4 , further comprising covering the MOV chip, the first and second electrodes, and portions of the first and second leads with a dielectric polymer coating.
9. 9 . The method of claim 4 , where the first and second electrodes are formed of one of copper, copper alloy, aluminum, aluminum covered with copper, silver, tin, and nickel.

Description

BACKGROUND Field The present disclosure relates generally 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 that is resistant to thermal shock. Description of Related Art Metal oxide varistors (MOVs) are voltage dependent, nonlinear devices that provide transient voltage suppression in electronic circuits. A MOV has high electrical resistance when subjected to a low voltage and a low electrical resistance when subjected to a high voltage. When connected in parallel with a protected circuit component, a MOV can clamp voltage to a safe level in the event of a high transient voltage in the circuit. The MOV thus absorbs energy that could otherwise damage the protected component. A conventional MOV chip is made from a composition of metal oxide granules embedded in a ceramic matrix. A shortcoming associated with such MOV compositions is that they must be subjected to a sintering process performed at very high temperatures to form a chip. Additionally, the ceramic matrix is brittle and is prone to cracking if subjected to thermal shock, which can occur during an abnormal overvoltage event. This can lead to excessive heating and combustion. It would be desirable to provide a MOV chip that can be manufactured using low temperature (e.g., room temperature) processes. It would also be desirable to provide a MOV chip that is resistant to thermal shock. It is with respect to these and other considerations that the present improvements may be useful. SUMMARY This Summary is provided to introduce a selection of concepts in a simplified form further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is the summary intended as an aid in determining the scope of the claimed subject matter. A metal oxide varistor (MOV) in accordance with an embodiment of the present disclosure includes 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. A method of manufacturing a metal oxide varistor (MOV) in accordance with an embodiment of the present disclosure includes 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. BRIEF DESCRIPTION OF THE DRAWINGS By way of example, various embodiments of the present disclosure will now be described, with reference to the accompanying drawings, wherein: FIG. 1A is a front perspective view illustrating a MOV in accordance with an embodiment of the present disclosure; FIG. 1B is a rear perspective view illustrating the MOV of FIG. 1A; FIG. 1C is a rear perspective view illustrating the MOV of FIG. 1A with a polymer coating; and 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 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. 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 herei