CN116936208A - Thermal link for thermally protecting metal oxide varistors - Google Patents

Thermal link for thermally protecting metal oxide varistors Download PDF

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Publication number
CN116936208A
CN116936208A CN202210348712.7A CN202210348712A CN116936208A CN 116936208 A CN116936208 A CN 116936208A CN 202210348712 A CN202210348712 A CN 202210348712A CN 116936208 A CN116936208 A CN 116936208A
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CN
China
Prior art keywords
lead
thermal link
tpv
thermal
main side
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202210348712.7A
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Chinese (zh)
Inventor
萧演敬
宋东健
涂军潮
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Dongguan Littelfuse Electronic Co Ltd
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Dongguan Littelfuse Electronic Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Dongguan Littelfuse Electronic Co Ltd filed Critical Dongguan Littelfuse Electronic Co Ltd
Priority to CN202210348712.7A priority Critical patent/CN116936208A/en
Publication of CN116936208A publication Critical patent/CN116936208A/en
Pending legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/10—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material voltage responsive, i.e. varistors
    • H01C7/12—Overvoltage protection resistors
    • H01C7/126—Means for protecting against excessive pressure or for disconnecting in case of failure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C1/00—Details
    • H01C1/14—Terminals or tapping points or electrodes specially adapted for resistors; Arrangements of terminals or tapping points or electrodes on resistors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
    • H01C17/28—Apparatus or processes specially adapted for manufacturing resistors adapted for applying terminals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/10—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material voltage responsive, i.e. varistors
    • H01C7/105—Varistor cores
    • H01C7/108—Metal oxide

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Manufacturing & Machinery (AREA)
  • Thermistors And Varistors (AREA)

Abstract

A thermal link for thermally protecting a metal oxide varistor is disclosed. The TPV apparatus herein may include: a varistor body comprising a first main side opposite a second main side; a first lead and a second lead connected to the first main side, and a third lead connected to the second main side. The TPV device can also include a thermal link connecting the first and second leads, and an insulating adhesive formed on the thermal link.

Description

Thermal link for thermally protecting metal oxide varistors
Technical Field
The present disclosure relates generally to protecting electrical and electronic circuits and devices from power surges, and more particularly to a thermal protection varistor having a thermal link.
Background
Overvoltage protection devices are used to protect electronic circuits and components from damage caused by overvoltage fault conditions. These overvoltage protection devices may include a Metal Oxide Varistor (MOV) connected between the circuit to be protected and a ground line. MOVs have specific current-voltage characteristics that allow the MOVs to be used to protect such circuits from catastrophic voltage surges. When a voltage greater than a rated or threshold voltage is applied to the device, current flows through the MOV, thereby generating heat. This may cause the linking element to melt. Once the link melts, an open circuit is created, thereby preventing the MOV from firing.
In case of sustained overvoltage or thermal runaway due in part to the above mentioned electrical stress, a thermal breaker opening device may be used. It is desirable to locate the thermal disconnect mechanism very close to the MOV disc so that the thermal response time is as fast as possible. Thus, the purpose of thermally disconnecting a MOV is to provide a relatively benign fault when subjected to conditions that lead to thermal runaway.
While thermal protection varistors are currently available, the thermal disconnect varistors currently available include complex components and are costly to manufacture. Thus, there is a need for a varistor of high efficiency construction to protect sensitive circuits and equipment from abnormal overvoltage transients, which is easy to maintain and repair. Current improvements are provided based on these and other considerations.
Disclosure of Invention
This summary is provided to introduce a selection of concepts in a simplified form that are 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 it intended to be used as an aid in determining the scope of the claimed subject matter.
In one method according to the present disclosure, a Thermal Protection Varistor (TPV) device may include: a varistor body comprising a first main side opposite a second main side; a first lead and a second lead connected to the first main side, and a third lead connected to the second main side. The TPV device can also include a thermal link connecting the first and second leads, and an insulating adhesive formed on the thermal link.
In another method according to the present disclosure, a Thermal Metal Oxide Varistor (TMOV) assembly may include: a varistor body having a first major side opposite a second major side; a thermode along the first major side; and a first lead and a second lead connected to the thermode. The TMOV assembly may further include a third lead connected to the second main side, a thermal link connecting the first lead and the second lead, and an insulating adhesive formed on the thermal link.
In another method according to the present disclosure, a method of forming a Thermal Metal Oxide Varistor (TMOV) assembly may include: providing a varistor body comprising a first main side opposite a second main side, wherein the thermodes are formed along the first main side; and connecting the first lead and the second lead to the thermode, and connecting the third lead to the second main side. The method may further include forming a thermal link between the first lead and the second lead, and forming an insulating adhesive on the thermal link.
Drawings
The drawings illustrate exemplary methods of the disclosed embodiments, which have heretofore been devised for the practical application of the principles thereof, wherein:
FIG. 1 is a perspective view of a TPV apparatus according to embodiments of the disclosure;
FIG. 2 is a perspective view of a TPV apparatus after formation of an insulating adhesive on a thermal link in accordance with an embodiment of the disclosure;
FIG. 3 is a perspective view of a TPV device after an overvoltage event has occurred in accordance with an embodiment of the disclosure;
FIG. 4 is a perspective view of a TPV device after an overvoltage event has occurred in accordance with an embodiment of the disclosure; and
fig. 5 is a flow chart of a method according to an embodiment of the present disclosure.
The figures are not necessarily drawn to scale. The drawings are merely representations, not intended to portray specific parameters of the disclosure. The drawings are intended to depict typical embodiments of the disclosure, and therefore should not be considered as limiting the scope. In the drawings, like numbering represents like elements. Moreover, some elements in some of the figures may be omitted or not to scale for clarity of illustration. Moreover, some reference numerals may be omitted from some of the figures for clarity.
Detailed Description
Embodiments in accordance with the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings. The system/circuit may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the systems and methods to those skilled in the art.
As described herein, a Thermal Protection Varistor (TPV) device is provided that includes a thermal link that forms an open circuit under overvoltage conditions. Conventional thermal protection solutions use low melting temperature TCO wires as the thermal link on the main circuit to connect the MOV body to the power supply. When the MOV chip is heated due to an overvoltage condition, the TCO wire will melt and form an open circuit. However, the molten liquid tends to flow uncontrollably, potentially reconnecting the power supply, which would fail to cut off the short circuit current and cause a catastrophic fire.
Embodiments of the present disclosure overcome the deficiencies of the prior art by using a thermally responsive glue with high arc extinction and high dielectric strength on a thermal link. Once the thermal link forms an open circuit, the glue will become a spacer fluid and fill the gap formed in the thermal link. The glue breaks the melted thermal links apart, ensuring that the thermal links do not reconnect again.
Turning now to fig. 1, a Thermal Protection Varistor (TPV) assembly/device (hereinafter "device") 100 according to an embodiment of the present disclosure will be described. As shown, the TPV device 100 includes a varistor body 102, in this embodiment, the varistor body 102 has a square or rectangular shape generally defined by an outer perimeter 103. The varistor body 102 includes a first electrode 104 arranged along the first side 106 and a second electrode (not shown) arranged along the second side 110. In some embodiments, the first and/or second electrodes 104, 106 may be thermodes. The thermodes may be ceramic, silver, copper, aluminum or copper plus aluminum metallization. The first lead 112 and the second lead 114 are electrically connected to the first electrode 104, and the third lead 116 is electrically connected to the second electrode.
The device 100 may also include a terminal assembly 118 coupled to the varistor body 102. In some embodiments, the terminal assembly 118 may include an insulating plate 120 between the first and second leads 112, 114, and a thermal link 124 extending between the first and second leads 112, 114. Although not limiting, the thermal link 124 may include solder. If the thermal link 124 exceeds the melting point, for example, in the event of an over-current condition, the thermal link 124 will break, thereby causing the first lead 112 or the second lead 114 to disconnect from the power source. As shown, a first end 128 of the thermal link 124 may be directly connected to the first lead 112 and a second end 130 of the thermal link 124 may be directly connected to the second lead 114. In some embodiments, a portion of the thermal link 124 may be formed on top of the insulating plate 120.
As shown in fig. 2, the device 100 may also include an insulating adhesive 135 formed on the thermal link 124. In some embodiments, the insulating adhesive 135 may be a thermally responsive glue, such as a thermoplastic hot melt glue (e.g., thermoplastic polyamide). An insulating adhesive 135 may surround the thermal link 124. When the thermal link 124 is below the melting point, physical/electrical contact is maintained with the first electrode 104. However, when the thermal link 124 heats up and exceeds the melting point of the thermal link 124, the thermal link 124 melts and begins to flow, thereby forming an insulating gap 140 through the thermal link 124, as shown in fig. 3. The gap 140 breaks the electrical connection between the first lead 112 and the second lead 114. The gap 140 further breaks the connection between the first and second leads 112, 114 and the first and second electrodes of the varistor body 102.
As the insulating adhesive 135 continues to heat, it will become a highly insulating liquid to fill and separate the melted wire segments of the thermal link 124, as shown in fig. 4. During use, the insulating adhesive 135 expands to create a channel internally for the thermal link 124. This prevents the thermal link 124 from flowing randomly and from possibly reconnecting back to the circuit. Advantageously, this high arc shielding solution has thermal protection reliability and long life, and is widely applicable to various thermal link designs.
Turning now to fig. 5, a method 200 according to an embodiment of the present disclosure will be described in more detail. At block 201, the method 200 may include providing a varistor body including a first major side opposite a second major side, wherein a thermoelectric electrode is formed along the first major side. In some embodiments, the thermode is formed along the second major side.
At block 202, the method 200 may include connecting the first lead and the second lead to the thermode, and connecting the third lead to the second major side. In some embodiments, an insulating plate is formed on top of the first lead. In some embodiments, the second lead is formed on top of the insulating plate.
At block 203, the method 200 may include forming a thermal link between the first lead and the second lead. In some embodiments, the thermal link is solder directly connected to the first and second leads.
At block 204, the method may further include forming an insulating adhesive on the thermal link. In some embodiments, the insulating adhesive is a thermoplastic hot melt adhesive. In some embodiments, the insulating adhesive completely surrounds the thermal link. In some embodiments, the insulating adhesive is a thermoplastic polyamide. In some embodiments, a gap is then formed by the thermal link upon occurrence of an overvoltage event, and an insulating adhesive enters the gap to prevent the thermal link from flowing back together and/or along the first main side of the varistor body towards other areas.
The foregoing discussion has been presented for purposes of illustration and description and is not intended to limit the disclosure to the form or forms disclosed herein. For example, various features of the disclosure may be combined together in one or more aspects, embodiments, or configurations to simplify the present disclosure. However, it should be understood that various features of certain aspects, embodiments, or configurations of the present disclosure may be combined in alternative aspects, embodiments, or configurations. Furthermore, the following claims are hereby incorporated into this detailed description by reference, with each claim standing on its own as a separate embodiment of this disclosure.
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.
The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Thus, the terms "comprising," "including," or "having," and variants thereof, are open-ended and are used interchangeably herein.
The phrases "at least one," "one or more," and/or "as used herein are open-ended expressions and are both connected and separated in operation. For example, each of the expressions "at least one of A, B and C", "at least one of A, B or C", "one or more of A, B and C", "one or more of A, B or C", and "A, B and/or C" represents a alone, B alone, C, A and B together, a and C together, B and C together, or A, B and C together.
All directional references (e.g., proximal, distal, upper, lower, upward, downward, left, right, transverse, longitudinal, front, rear, top, bottom, above, below, vertical, horizontal, radial, axial, clockwise, and counterclockwise) are only used for identification purposes to aid the reader's understanding of the present disclosure, and do not create limitations, particularly as to the position, orientation, or use of the present disclosure. Unless otherwise indicated, connective references (e.g., additional, coupled, connected, and combined) are to be construed broadly and may include intermediate members between a collection of elements and relative movement between elements. Thus, a connective reference does not necessarily infer that two elements are directly connected and in fixed relation to each other.
Furthermore, identifying references (e.g., primary, secondary, first, second, third, fourth, etc.) does not imply importance or priority, but rather is used to distinguish one feature from another. The drawings are for illustrative purposes only and the sizes, positions, sequences and relative sizes reflected in the accompanying drawings may vary.
Furthermore, the terms "substantial" or "substantially" and the terms "approximately" or "approximately" may be used interchangeably in some embodiments and may be described using any relevant metric acceptable to one of ordinary skill in the art. For example, these terms may be used as a comparison to a reference parameter to indicate a deviation that can provide the intended function. Although not limiting, the deviation from the reference parameter may be in an amount of, for example, less than 1%, less than 3%, less than 5%, less than 10%, less than 15%, less than 20%, etc.
Furthermore, while the illustrative method 200 described above is described as a series of acts or events, the present disclosure is not limited by the illustrated ordering of such acts or events, unless specifically noted. For example, some acts may occur in different orders and/or concurrently with other acts or events apart from those illustrated and/or described herein, in accordance with the disclosure. Moreover, not all illustrated acts or events are required to implement a methodology in accordance with the present disclosure. Furthermore, method 300 may be implemented in connection with the formation and/or processing of structures shown and described herein, as well as in connection with other structures not shown.
The scope of the present disclosure is not limited by the specific embodiments described herein. Indeed, various other embodiments and modifications of the present disclosure in addition to those described herein will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Accordingly, such other embodiments and modifications are intended to be within the scope of this disclosure. Furthermore, the present disclosure is described herein in the context of particular embodiments in a particular environment for a particular purpose. Those of ordinary skill in the art will recognize that the usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the following claims are to be interpreted in accordance with the full breadth and spirit of the present disclosure as described herein.

Claims (19)

1. A Thermal Protection Varistor (TPV) apparatus comprising:
a varistor body comprising a first main side opposite a second main side;
first and second leads connected to the first main side, and a third lead connected to the second main side;
a thermal link connecting the first lead and the second lead; and
an insulating adhesive formed over the thermal link.
2. The TPV device of claim 1, further comprising a thermode along the first major side of the varistor body.
3. The TPV apparatus of claim 2, wherein the first and second leads are in direct contact with the thermode, and wherein the thermal link is in direct contact with the first and second leads.
4. The TPV apparatus of claim 1 wherein the insulating adhesive is a thermoplastic hot melt adhesive.
5. The TPV apparatus of claim 1, wherein a gap is formed through the thermal link upon occurrence of an overvoltage event, and wherein the insulating adhesive enters the gap.
6. The TPV apparatus of claim 1, further comprising an insulating plate positioned on top of the first lead.
7. The TPV apparatus of claim 6, wherein the second lead is located on top of the insulator plate.
8. A Thermal Metal Oxide Varistor (TMOV) assembly, comprising:
a varistor body comprising a first main side opposite a second main side;
a thermode along the first major side;
first and second leads connected to the thermode, and a third lead connected to the second main side;
a thermal link connecting the first lead and the second lead; and
an insulating adhesive formed over the thermal link.
9. The TPV assembly of claim 8, wherein the thermal link is in direct contact with the first lead and the second lead.
10. The TPV assembly of claim 8, wherein the insulating adhesive is a thermoplastic hot melt adhesive.
11. The TPV assembly of claim 8, wherein a gap is formed through the thermal link upon occurrence of an overvoltage event, and wherein the insulating adhesive enters the gap.
12. The TPV assembly of claim 8, further comprising an insulator plate positioned on top of the first lead.
13. The TPV assembly of claim 12, wherein the second lead is formed on top of the insulator plate.
14. A method of forming a Thermal Metal Oxide Varistor (TMOV) assembly, comprising:
providing a varistor body comprising a first main side opposite a second main side, wherein a thermode is formed along the first main side;
connecting a first lead and a second lead to the thermode and a third lead to the second main side;
forming a thermal link between the first lead and the second lead; and
an insulating adhesive is formed over the thermal link.
15. The method of claim 14, wherein the thermal link is in direct contact with the first and second leads.
16. The method of claim 14, wherein the insulating adhesive is a thermoplastic hot melt adhesive.
17. The method of claim 14, further comprising forming a gap through the thermal link upon occurrence of an overvoltage event, wherein the insulating adhesive enters the gap.
18. The method of claim 14, further comprising forming an insulating plate on top of the first lead.
19. The method of claim 18, wherein the second lead is formed on top of the insulating plate.
CN202210348712.7A 2022-04-01 2022-04-01 Thermal link for thermally protecting metal oxide varistors Pending CN116936208A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202210348712.7A CN116936208A (en) 2022-04-01 2022-04-01 Thermal link for thermally protecting metal oxide varistors

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210348712.7A CN116936208A (en) 2022-04-01 2022-04-01 Thermal link for thermally protecting metal oxide varistors

Publications (1)

Publication Number Publication Date
CN116936208A true CN116936208A (en) 2023-10-24

Family

ID=88391213

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202210348712.7A Pending CN116936208A (en) 2022-04-01 2022-04-01 Thermal link for thermally protecting metal oxide varistors

Country Status (1)

Country Link
CN (1) CN116936208A (en)

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