A varistor with a reflowable thermal protection device on its surface.

Abstract

More specifically, regarding the protection of electrical and electronic circuits and equipment from power surges, we provide a thermally protected varistor having a reflowable surface-mount circuit protection device. [Solution] The circuit protection device may include a varistor body including a first surface, where a thermal electrode is positioned along the first surface, a first lead electrically connected to the thermal electrode, and a second lead electrically connected to the second surface. The circuit protection device may further include a reflowable circuit protection device located on the thermal electrode, and a third lead connected to the reflowable circuit protection device, where the end of the third lead is a spring connected to the thermal electrode by a conductive element.

Description

Technical Field

[0001] [Cross - Reference to Related Applications] This application claims priority to U.S. Provisional Patent Application No. 63 / 691,573, filed on September 6, 2024, which is hereby incorporated by reference in its entirety.

[0002] The present disclosure generally relates to the protection of electrical and electronic circuits and devices from power surges, and more particularly to thermally protected varistors having reflowable surface - mount circuit protection devices.

Background Art

[0003] Over - voltage protection devices are used to protect electronic circuits and components from damage caused by over - voltage fault conditions. These over - voltage protection devices may include a metal oxide varistor (MOV) connected between the circuit to be protected and the ground wire. The MOV has specific current - voltage characteristics that enable it to be used to protect such a circuit from destructive voltage surges. Typically, these devices utilize spring elements and link elements that can melt during abnormal conditions to form an open circuit. In particular, when a voltage greater than the normal or threshold voltage is applied to the device, current flows through the MOV, which generates heat. This causes the link element to melt. When the link element melts, an open circuit is created when the spring moves, thereby preventing the MOV from catching fire.

[0004] Thermally protected varistors are currently available, but currently available thermal - isolation varistors may be less reliable in some cases, particularly for automotive applications (e.g., AEC - Q specifications). In view of the above and other matters, this improvement is provided.

Summary of the Invention

[0005] The circuit protection device may include a varistor body including a first surface, where a thermal electrode is positioned along the first surface, a first lead electrically connected to the thermal electrode, and a second lead electrically connected to the second surface. The circuit protection device may further include a reflowable circuit protection device located on the thermal electrode, and a third lead connected to the reflowable circuit protection device, where the end of the third lead is a spring connected to the thermal electrode by a conductive element.

[0006] The fuse may include a varistor body having a first surface opposite to a second surface and a thermal electrode arranged along the first surface, where a first lead is electrically connected to the thermal electrode and a second lead is electrically connected to the second surface. The fuse may further include a reflowable circuit protection device connected to the thermal electrode and a third lead connected to the reflowable circuit protection device, where the end of the third lead is a spring connected to the thermal electrode by a conductive element.

[0007] A method for operating a circuit protection device may include the steps of electrically connecting a first lead to a thermal electrode along a first surface of a varistor body, and electrically connecting a second lead to a second surface of a varistor body. The method may further include connecting a reflowable circuit protection device to the thermal electrode, and connecting a third lead to the reflowable circuit protection device, where the end of the third lead is a spring connected to the thermal electrode by a conductive element. The method may further include, in response to a thermal event, moving the end of the third lead away from the thermal electrode in response to a force on a limiting element of the reflowable circuit protection device. [Brief explanation of the drawing]

[0008] The attached drawings illustrate exemplary approaches of the disclosed embodiments that have been devised to date for the practical application of the principle.

[0009] [Figure 1]This is a top view of a circuit protection device, including a reflowable circuit protection device, according to an embodiment of the present disclosure.

[0010] [Figure 2A] This is a top view of a circuit protection device, including a reflowable circuit protection device, according to an embodiment of the present disclosure. [Figure 2B] This is a top view of a circuit protection device, including a reflowable circuit protection device, according to an embodiment of the present disclosure.

[0011] [Figure 3A] The operation of a reflowable circuit protection device according to an embodiment of the present disclosure is shown. [Figure 3B] The operation of a reflowable circuit protection device according to an embodiment of the present disclosure is shown. [Figure 3C] The operation of a reflowable circuit protection device according to an embodiment of the present disclosure is shown.

[0012] [Figure 4A] This invention demonstrates the operation of a circuit protection device, including a reflowable circuit protection device, according to an embodiment of this disclosure. [Figure 4B] This invention demonstrates the operation of a circuit protection device, including a reflowable circuit protection device, according to an embodiment of this disclosure. [Figure 4C] This invention demonstrates the operation of a circuit protection device, including a reflowable circuit protection device, according to an embodiment of this disclosure.

[0013] [Figure 5A] This invention demonstrates the operation of a circuit protection device, including a reflowable circuit protection device, according to an embodiment of this disclosure. [Figure 5B] This invention demonstrates the operation of a circuit protection device, including a reflowable circuit protection device, according to an embodiment of this disclosure. [Figure 5C] This invention demonstrates the operation of a circuit protection device, including a reflowable circuit protection device, according to an embodiment of this disclosure.

[0014] [Figure 6A] Shows the operation of a circuit protection device including a reflowable circuit protection device according to an embodiment of the present disclosure. [Figure 6B] Shows the operation of a circuit protection device including a reflowable circuit protection device according to an embodiment of the present disclosure. [Figure 6C] Shows the operation of a circuit protection device including a reflowable circuit protection device according to an embodiment of the present disclosure.

[0015] [Figure 7A] Shows the operation of a reflowable circuit protection device according to an embodiment of the present disclosure. [Figure 7B] Shows the operation of a reflowable circuit protection device according to an embodiment of the present disclosure. [Figure 7C] Shows the operation of a reflowable circuit protection device according to an embodiment of the present disclosure. [Figure 7D] Shows the operation of a circuit protection device including a reflowable circuit protection device according to an embodiment of the present disclosure.

[0016] [Figure 8A] Shows the operation of a circuit protection device including a reflowable circuit protection device according to an embodiment of the present disclosure. [Figure 8B] Shows the operation of a circuit protection device including a reflowable circuit protection device according to an embodiment of the present disclosure. [Figure 8C] Shows the operation of a circuit protection device including a reflowable circuit protection device according to an embodiment of the present disclosure. [Figure 8D] Shows the operation of a circuit protection device including a reflowable circuit protection device according to an embodiment of the present disclosure.

[0017] [Figure 9] Shows one non-limiting chart showing solder link resistance versus reflow count and temperature.

[0018] The drawings are not necessarily to scale. The drawings are for illustrative purposes only and are not intended to represent any particular parameter of the disclosure. The drawings are intended to depict a typical embodiment of the disclosure and should therefore not be considered limiting. In the drawings, similar reference numerals represent similar elements.

[0019] Furthermore, certain elements in some figures may be omitted or shown without being proportional to the actual size to facilitate the explanation. Additionally, for clarity, some reference numerals may be omitted in certain figures. [Modes for carrying out the invention]

[0020] Herein, embodiments of the present disclosure are described more fully below with reference to the accompanying drawings. The system / circuit may be embodied in numerous different forms and should not be construed as being limited to the embodiments described herein. Rather, these embodiments are provided so as to ensure that the present disclosure is sufficient and complete and so as to convey the scope and methods of the system to those skilled in the art.

[0021] As will become apparent herein, the circuit protection devices of this disclosure can address the problems of the prior art, namely high cost and low reliability, by using a fuse coupled to a reflowable circuit protection device to form a reliable open circuit. During overheating events caused by abnormal overvoltage conditions, the circuit protection device can protect the circuit from damage.

[0022] Referring here to Figure 1, a circuit protection assembly / device 10 for use with an electrical circuit according to an embodiment of the present disclosure is described. As shown, the device 10 includes a varistor body 12, which in this embodiment has a circular or cylindrical shape generally defined by a periphery 13. The varistor body 12 includes a first face opposite a second face and a thermal electrode 18 positioned along the first face. A first lead 21 is electrically connected to the thermal electrode 18, a second lead 22 is electrically connected to the second face, and a third lead 23 is electrically connected to a reflowable circuit protection device (RTP) 24 and the thermal electrode 18. In some embodiments, the thermal electrode 18 is a ceramic, silver, copper, aluminum, or copper-aluminum metallization layer. The first lead 21, the second lead 22, and / or the third lead 23 may be fixed to the first and second faces of the varistor 12, respectively, using hot solder. Although not shown, device 10 may be encapsulated / surrounded by conformal epoxy or other highly insulating material. If RTP24 includes a low-temperature thermal sensing element, RTP24 is a reflowable circuit protection device. If no thermal sensing element is present, RTP24 is a reflowable thermal protection device.

[0023] In some embodiments, the RTP24 may be soldered to the surface of the thermal electrode 18 and connected to terminals, or the RTP may be mounted on the outer periphery 13. The RTP124 may be a high-current reflowable thermal protection device, which is a low-resistance surface-mountable thermal protector. The RTP may have a set open-circuit temperature and can be mounted using lead-free surface-mount device (SMD) assemblies and reflow processes.

[0024] Generally, the RTP24 includes a conductive element through which the load current flows, and an elastic element adapted to apply force to the conductive element. In some embodiments, the conductive element incorporates a sensing element. When the temperature of the sensing element exceeds a threshold, the sensing element becomes susceptible to deformation and / or breakage due to the force applied to the conductive element by the elastic element. Ultimately, the conductive element is mechanically opened under that force, resulting in an open-circuit condition. In other embodiments, the sensing element and the conductive element are separate, and the sensing element acts to keep the conductive element in a low-resistance state.

[0025] During the reflow process, the sensing element may lose its elasticity. To prevent the force applied by the elastic element from disengaging the conductive element during installation, a limiting element may be used to maintain the elastic element in a state where it does not exert force on the conductive element. After the reflowable thermal fuse is mounted on the panel and passed through the reflow oven, the limiting element may be deactivated by applying an activation current to the limiting element. This, in turn, activates the reflowable thermal fuse. Further details of RTP24 are described below. The attached drawings are included to provide further understanding and are incorporated into and form part of this specification.

[0026] Figures 2A and 2B show an exemplary device 100 in more detail. The device 100 includes a varistor body 112 containing a thermal electrode 118. A first lead 121 is electrically connected to the thermal electrode 118, a second lead 122 is electrically connected to a second surface, and a third lead 123 is electrically connected to an RTP 124. In some embodiments, a conductive element 126 (e.g., solder and / or internal electrode) may be positioned along the thermal electrode 118, where the third lead 123 forms an electrical connection 128 with the conductive element 126. The end 131 of the third lead 123 may be an elastic element 130 (e.g., a spring), which is connected to the thermal electrode 118 by the conductive element 126. The elastic element 130 may be made of a conductive material such as copper or stainless steel, or a non-conductive material such as plastic or fiber-reinforced plastic composite. Other materials and structures may be used. The elastic element 130 may be subjected to the flow of current and may be adapted to apply a force to the conductive element 126. When the temperature of the conductive element 126 exceeds a threshold, it becomes susceptible to deformation and / or breakage due to the force from the elastic element 130. Ultimately, the conductive element 126 is mechanically opened under that force, resulting in an open-circuit condition as shown in Figure 2B.

[0027] During the reflow process, to prevent the force applied by the elastic element 130 from opening the conductive element 126 during installation, one or more limiting elements 132, 134 may be used as part of the RTP 124 to maintain the elastic element 130 in a state where it does not exert force on the conductive element 126. After the reflowable thermal fuse is installed in the varistor body 112, the limiting elements 132, 134 may be switched off by applying an activation current and / or mechanical force through the limiting elements 132, 134. This, in turn, activates the reflowable thermal fuse.

[0028] Figures 3A to 3C show various states of one embodiment of the RTP 124. In Figure 3A, the RTP 124 is in the initial / reflow state. In this state, the limiting element 132 is used to prevent the elastic element 130 from applying force to the conductive element 136.

[0029] Figure 3B shows the RTP 124 in the activated / operated state. In the shown embodiment, an electrical or mechanical force 138 may be applied to the limiting element 132 to move the limiting element 132 away from the conductive element 136 and / or the elastic element 130. Once the release is formed, the elastic element 130 may be released, thereby applying force to the conductive element 136.

[0030] Figure 3C shows the RTP124 under fault / active protection conditions. In this state, the force applied by the elastic element 130 creates an opening in the conductive element 136.

[0031] Figures 4A to 4C show various states of one embodiment of device 200. Device 200 may be the same as or similar to device 10 described herein. Therefore, for brevity, only specific aspects of device 200 will be described below. Device 200 includes a varistor body 212 including a thermal electrode 218. A first lead 221 is electrically connected to the thermal electrode 218, a second lead 222 is electrically connected to a second surface, and a third lead 223 is electrically connected to an RTP 224. As shown, a conductive element 226 (e.g., solder and / or internal electrode) may be arranged along the thermal electrode 218, where the end 231 of the third lead 223 forms an electrical connection with the conductive element 226. The third lead 223 may include an elastic element 230 (e.g., a spring), which is connected to the thermal electrode 218 by the conductive element 226. The elastic element 230 may be subjected to the flow of current and may be adapted to apply force to the conductive element 226.

[0032] In Figure 4A, the RTP224 is in its initial / reflow state. In this state, the limiting element 232 is used to prevent the elastic element 230 from applying force to the conductive element 226.

[0033] Figure 4B shows the RTP 224 in the activated / operated state. In the shown embodiment, an electrical or mechanical force 238 may be applied to the limiting element 232 to move the limiting element 232 away from the elastic element 230. Once the release is formed, the elastic element 230 may be released, thereby applying force to the conductive element 226.

[0034] Figure 4C shows the RTP224 under fault / active protection conditions. In this state, for example, when the conductive element 226 exceeds the temperature threshold and begins to soften / deform, the force applied by the elastic element 230 creates an opening between the end 231 and the conductive element 226.

[0035] Figures 5A to 5C show various states of one embodiment of device 300. Device 300 may be the same as or similar to the device described herein. Therefore, for brevity, only specific aspects of device 300 will be described below. Device 300 includes a varistor body 312 including a thermal electrode 318. A first lead 321 is electrically connected to the thermal electrode 318, a second lead 322 is electrically connected to a second surface, and a third lead 323 is electrically connected to an RTP 324. A conductive element 326 (e.g., solder and / or internal electrode) may be arranged along the thermal electrode 318, where the end 331 of the third lead 323 forms an electrical connection with the conductive element 326. The third lead 323 may include an elastic element 330 (e.g., a spring), which is connected to the thermal electrode 318 by the conductive element 326. The elastic element 330 may be subjected to the flow of current and may be adapted to apply force to the conductive element 326.

[0036] In Figure 5A, the RTP 324 is in its initial / reflow state. In this state, the limiting element 332 is used to prevent the elastic element 330 from applying force to the conductive element 326. More specifically, the end 331 of the elastic element 330 may be held within the slot 340 of the limiting element 332. As shown, the limiting element 332 may be positioned directly above the conductive element 326.

[0037] Figure 5B shows the RTP 324 in the activated / operated state. In the shown embodiment, an electrical or mechanical force 338 may be applied to the limiting element 332 to move the limiting element 332 away from the elastic element 330. Once the release is formed, the elastic element 330 may be released, thereby applying force to the conductive element 326.

[0038] Figure 5C shows the RTP324 under fault / active protection conditions. In this state, for example, when the conductive element 326 exceeds a temperature threshold and begins to soften / deform, the force applied by the elastic element 330 creates an opening between the end 331 and the conductive element 326.

[0039] Figures 6A to 6C show various states of one embodiment of device 400. Device 400 includes a varistor body 412 containing a thermal electrode 418. A first lead 421 is electrically connected to the thermal electrode 418, a second lead 422 is electrically connected to a second surface, and a third lead 423 is electrically connected to an RTP 424. A conductive element 426 (e.g., solder and / or internal electrode) may be positioned along the thermal electrode 418, where the end 431 of the third lead 423 forms an electrical connection with the conductive element 426. The third lead 423 may include an elastic element 430 (e.g., a spring), which is connected to the thermal electrode 418 by the conductive element 426. The elastic element 430 may be subject to current flow and may be adapted to apply force to the conductive element 426.

[0040] In Figure 6A, the RTP 424 is in its initial / reflow state. In this state, the limiting element 432 is used to prevent the elastic element 430 from applying force to the conductive element 426. More specifically, the end 431 of the elastic element 430 may be held below the limiting element 432.

[0041] Figure 6B shows the RTP 424 in the activated / operated state. In the shown embodiment, an electrical or mechanical force 438 may be applied to the limiting element 432 to move the limiting element 432 away from the elastic element 430. Once the release is formed, the elastic element 430 may be released, thereby applying force to the conductive element 426.

[0042] Figure 6C shows the RTP424 under fault / active protection conditions. In this state, for example, when the conductive element 426 exceeds the temperature threshold and begins to soften / deform, the force applied by the elastic element 430 creates an opening between the end 431 and the conductive element 426.

[0043] Figures 7A to 7D show various states of one embodiment of the RTP524. In this embodiment, the RTP524 may include a limiting element 532 in the form of a fusible link, which may be made from a material having a melting temperature higher than the reflow temperature. As shown, the fusible link may have a weak central section 539. The limiting element 532 may be made from copper, stainless steel, or an alloy. Other materials and structures may be used.

[0044] In Figure 7A, the RTP 524 is in the initial / reflow state. In this state, the limiting element 532 is used to prevent the elastic element 530 from applying force to the conductive element 536.

[0045] Figure 7B shows the RTP 524 in the activated / operated state. In the shown embodiment, current may be supplied to the limiting element 532, thereby causing the limiting element 532 to break / open, for example, at its weak central section 539, as shown in Figure 7C. Once the opening is formed, the elastic element 530 may be released, thereby applying force to the conductive element 536.

[0046] Figure 7D shows the RTP 524 under fault / active protection conditions. In this state, the force applied by the elastic element 530 creates an opening in the conductive element 536.

[0047] Figures 8A to 8D show various states of one embodiment of device 500. Device 500 includes a varistor body 512 including a thermal electrode 518. A first lead 521 is electrically connected to the thermal electrode 518, a second lead 522 is electrically connected to a second surface, and a third lead 523 is electrically connected to an RTP 524. A conductive element 526 (e.g., solder and / or internal electrode) may be positioned along the thermal electrode 518, where the end 531 of the third lead 523 forms an electrical connection with the conductive element 526. The third lead 523 may include an elastic element 530 (e.g., a spring), which is connected to the thermal electrode 518 by the conductive element 526. The elastic element 530 may be subject to current flow and may be adapted to apply force to the conductive element 526.

[0048] In Figure 8A, the RTP 524 is in its initial / reflow state. In this state, the limiting element 532 is used to prevent the elastic element 530 from applying force to the conductive element 526.

[0049] Figure 8B shows the RTP 524 in the activated / operated state. In the shown embodiment, current may be supplied to the limiting element 532, thereby causing the limiting element 532 to break / open, for example, at its weak central section 539, as shown in Figure 8C. Once the opening is formed, the elastic element 530 may be released, thereby it may exert force on the conductive element 536.

[0050] Figure 8D shows the RTP524 under fault / active protection conditions. In this state, for example, when the conductive element 426 exceeds the temperature threshold and begins to soften / deform, the force applied by the elastic element 430 creates an opening between the end 431 and the conductive element 426.

[0051] Figure 9 shows a non-limiting chart illustrating solder link resistance versus reflow cycles and temperature.

[0052] For convenience and clarity, terms such as “top,” “bottom,” “upper side,” “lower side,” “vertical,” “horizontal,” “lateral,” and “longitudinal” are used herein to describe the relative arrangement and orientation of various components and their constituent parts. The aforementioned technical terms will include the words specifically mentioned, their derivatives, and words with similar meanings.

[0053] When used herein, elements or actions described in the singular form and following the word "a" or "an" should be understood not to exclude multiple elements or actions, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” in this disclosure are not intended to be construed as excluding the existence of additional embodiments that also incorporate the described features.

[0054] Furthermore, in the following description and / or claims, the terms “on,” “covering,” “positioned,” and “on top of” may be used in the following description and claims. “On,” “covering,” “positioned,” and “on top of” may be used to refer to two or more elements being in direct physical contact with one another. However, “on,” “covering,” “positioned,” and “on top of” may also mean that two or more elements are not in direct contact with one another. For example, “over” may mean that one element is on top of another element but is not in contact with one another, and that there may be another element or more elements in between the two elements. Furthermore, the scope of the subject matter described in the claims is not limited in this respect, but the terms “and / or” may mean “and,” “or,” “exclusive ‘or’,” “one,” “some but not all,” “either one,” and / or “both.”

[0055] While this disclosure has been described with reference to a particular approach, many modifications, alterations, and changes to the described approach are possible without departing from the subject and scope of this disclosure as defined in the attached claims. Therefore, this disclosure is not limited to the described approach but is intended to encompass the entire scope and its equivalents as defined by the following claims.

Claims

1. A circuit protection device, This is the barista machine itself. The first side; and A thermal electrode is arranged along the first surface, where a first lead is electrically connected to the thermal electrode and a second lead is electrically connected to the second surface. Barista body having; A reflowable circuit protection device located on the thermal electrode; and A third lead connected to the reflowable circuit protection device, wherein the end of the third lead is a spring connected to the thermal electrode by a conductive element. A circuit protection device equipped with the following features.

2. The reflowable circuit protection device according to claim 1, wherein the reflowable circuit protection device includes one or more limiting elements and one or more elastic elements.

3. The circuit protection device according to claim 2, wherein the spring of the third lead is coupled to the one or more limiting elements.

4. The circuit protection device according to claim 3, wherein in a first configuration, one or more limiting elements hold the spring in a first position, and in a second configuration, one or more limiting elements release the spring to a second position.

5. The circuit protection device according to claim 2, wherein the one or more limiting elements are fusible elements.

6. The circuit protection device according to claim 5, wherein the current passing through the fusible element causes the weak central portion of the fusible element to open.

7. The circuit protection device according to claim 2, wherein the one or more elastic elements are second springs.

8. It is a fuse, This is the barista machine itself. The first face opposite the second face; and A thermal electrode is arranged along the first surface, where a first lead is electrically connected to the thermal electrode and a second lead is electrically connected to the second surface. Barista body having; A reflowable circuit protection device connected to the thermal electrode; and A third lead connected to the reflowable circuit protection device, wherein the end of the third lead is a spring connected to the thermal electrode by a conductive element. A fuse equipped with this feature.

9. The fuse according to claim 8, wherein the reflowable circuit protection device comprises one or more limiting elements and one or more elastic elements.

10. The fuse according to claim 9, wherein the spring of the third lead is coupled to the one or more limiting elements.

11. The fuse according to claim 10, wherein in a first configuration, one or more limiting elements hold the spring in a first position, and in a second configuration, one or more limiting elements release the spring to a second position.

12. The fuse according to claim 9, wherein the one or more limiting elements are fusible elements.

13. The fuse according to claim 12, wherein the current passing through the fusible element causes the weak central portion of the fusible element to open.

14. The fuse according to claim 9, wherein the one or more elastic elements are second springs.

15. The first step is to electrically connect the first lead to the thermal electrode along the first surface of the varistor body; The step of electrically connecting the second lead to the second surface of the varistor body; The step of connecting a reflowable circuit protection device to the thermal electrode; and The third lead is connected to the reflowable circuit protection device, where the end of the third lead is a spring connected to the thermal electrode by a conductive element; A step in which, in response to a thermal event, the end of the third lead is moved away from the thermal electrode in response to a force on the limiting element of the reflowable circuit protection device. A method for operating a circuit protection device that includes the following features.

16. The method according to claim 15, wherein in the first configuration, the limiting element holds the spring in a first position, and in the second configuration, the limiting element releases the spring to a second position.

Images