A protective element

Abstract

This invention belongs to the field of circuit protection technology, specifically relating to a protection element, equivalent to a high-current protection element consisting of two independent protection elements connected in parallel. The high-current protection element is considered as a back-side circuit module and a front-side circuit module stacked on the front and back sides of a ceramic substrate, connected to an external circuit via supporting conductor terminals. This invention features fuse assemblies on both the front and back sides of the ceramic substrate, enabling dual-path current flow. The supporting conductor terminals serve as the input ports for external current or voltage, while also supporting the ceramic substrate. Ultimately, the high-current protection element achieves high current carrying capacity through two parallel-connected fuse assemblies. This approach avoids the need for novel fuse materials with suitable melting points and low resistivity, while also preventing the increased risk of rapid fuse failure due to excessively increasing fuse size and thickness.

Description

Technical Field

[0001] This invention belongs to the field of circuit protection technology, specifically relating to a protection element with dual overcurrent and overvoltage protection. Its main features are dual current-blowout paths and high current-carrying capacity. Background Technology

[0002] Lithium-ion rechargeable batteries are widely used in portable mobile devices such as mobile phones, laptops, tablets, and digital cameras, and are increasingly being applied to many new fields such as energy storage batteries, two-wheeled vehicle batteries, drones, and robotic vacuum cleaners. While possessing many superior performance characteristics, they still have drawbacks such as the potential for fire, combustion, and explosion if not properly managed during charging and discharging. This is especially true in electric vehicles, where the number or volume of lithium-ion batteries used is enormous, and a fire or explosion could even pose a life-threatening danger.

[0003] Currently, the main protection components include PPTC, SMD fuses, breakers, self-controlled protection components, and IC plus MOS components as secondary protection components. Self-controlled protection components, as a safer protection component that can prevent both overcurrent and overvoltage, are receiving increasing development and attention. Most self-controlled protection components widely used in the market are low-current (12A, 15A), such as those used in portable mobile devices like mobile phones and tablets. However, in high-current applications such as energy storage, electric bicycles, drones, sweepers, and electric balance scooters, where high-current self-controlled protection components are unavailable, multiple components are often used in parallel.

[0004] For market applications, while parallel connection of multiple low-current self-controlled protection components can meet the needs of some high-current terminal equipment applications (such as two-wheeled vehicles with a current of around 60A), it is difficult to meet the needs of ultra-high current applications, such as energy storage applications with currents of 200A and above. Furthermore, parallel connection of multiple components results in a larger design board area, higher design complexity, and concerns about component performance consistency. Therefore, the market urgently needs a high-current self-controlled protection component.

[0005] The conventional approach to designing high-current self-controlled protection components is to increase the product size. However, within the same size, either a conductor material with lower resistivity is used, or a larger and thicker fuse assembly is employed to reduce the product's internal resistance. Firstly, due to product requirements, the product must meet heat resistance requirements exceeding 260℃, while simultaneously needing to fuse quickly upon triggering protection. This necessitates a fuse assembly with the lowest possible melting point. In this case, the fuse assembly's melting point needs to be between 260℃ and 320℃. However, fuse assemblies within this temperature range have high resistivity, making it difficult to find fuse assemblies with both a high melting point and low resistivity. Therefore, using a larger and thicker fuse assembly is a feasible solution, but excessively increasing the size and thickness of the fuse assembly will increase the risk of rapid fuse failure.

[0006] Therefore, it is necessary to design a completely new product solution and develop a self-controlled protection element that meets the requirements of high current applications. Summary of the Invention

[0007] The purpose of this invention is to provide a protection element that has dual overcurrent and overvoltage protection functions and high current electrical parameter specifications to meet the requirements of use in high current terminal fields.

[0008] The present invention achieves the above objective through the following technical solution: a protective element, comprising:

[0009] The ceramic substrate may have several plug holes and through holes;

[0010] The heating element is disposed on a ceramic substrate, and is not limited to the front or back of the ceramic substrate, or can even be disposed on both sides;

[0011] An insulating layer is stacked on a ceramic substrate and covers the heating element;

[0012] The top electrode is divided into a front top electrode and a back top electrode, which are stacked on the front and back sides of the ceramic substrate, respectively.

[0013] The intermediate electrode is divided into a front intermediate electrode and a back intermediate electrode, which can be connected to the lead-out electrode of the heating element on the same side.

[0014] The fuse assembly is stacked on both the front and back sides of the ceramic substrate and is divided into a front fuse assembly and a back fuse assembly. It has a dual current path that allows current to flow simultaneously. When current or voltage flows through the heating element, it can melt and form a current path at the same time.

[0015] Both the front and rear fuse assemblies are connected to an upper electrode and a middle electrode (soldering methods include high-temperature soldering and reflow soldering), and flux is applied above them. Furthermore, they are enclosed by a housing, forming a space with the ceramic substrate, including but not limited to the fuse assembly within this space.

[0016] Next, the external electrode connected to the back electrode has one or more supporting conductor terminals on it. All supporting conductor terminals are coplanar and are higher than or not lower than the height of the back shell. These supporting conductor terminals are metal bumps or metal pillars and can be soldered to the external electrode.

[0017] Through these supporting conductor terminals, external current can flow in from the supporting conductor terminals on one side of the external electrode, and then flow through the front fuse assembly and the back fuse assembly, and finally flow out from the supporting conductor terminals on the external electrode on the other side of the ceramic substrate; external voltage or current can enter from the third port (supporting conductor terminal), the heating element works, and at the same time melts the front fuse assembly and the back fuse assembly, realizing the circuit cut-off function.

[0018] This invention takes a different approach, starting with product structuring, and creates dual current paths on a ceramic substrate, thus meeting the requirements for high-current applications.

[0019] The high-current protection element of this invention features fuse assemblies on either the front or back of the ceramic substrate, enabling dual-path current flow. The supporting conductor terminals serve as both the input ports for external current or voltage and the support for the ceramic substrate. Ultimately, the high-current protection element achieves its high current-carrying capacity through two parallel-connected fuse assemblies. This approach avoids the need for novel fuse materials with suitable melting points and low resistivity, while also preventing the increased risk of rapid product failure caused by simply increasing the size and thickness of the fuse assembly. Attached Figure Description

[0020] Figure 1 This is a cross-sectional structural schematic diagram of the high current protection element of the present invention;

[0021] Figure 2 This is a schematic diagram of the principle of the high current protection element of the present invention;

[0022] Figure 3 is a plan view of the ceramic substrate back circuit module and the ceramic substrate front circuit module without the cover component according to the present invention. Figure 3-1 This is a schematic diagram of the rear loop module; Figure 3-2 This is a schematic diagram of the front loop module;

[0023] Figure 4 This is a schematic diagram illustrating the principle of other variations of the high-current protection element of the present invention;

[0024] Figure 5 This is a cross-sectional structural schematic diagram of other variations of the high-current protection element of the present invention;

[0025] Figure 6 is a plan view of other variations of the ceramic substrate back circuit module and the ceramic substrate front circuit module without a cover component according to the present invention, wherein... Figure 6-1 This is a schematic diagram of the rear loop module. Figure 6-2 This is a schematic diagram of the front loop module;

[0026] Figure 7 This is a cross-sectional structural schematic diagram of other variations of the high-current protection element of the present invention;

[0027] Figure 8 is a plan view of other variations of the ceramic substrate back circuit module and the ceramic substrate front circuit module without a cover component according to the present invention, wherein... Figure 8-1 Schematic diagram of the rear loop module. Figure 8-2 Schematic diagram of the front loop module;

[0028] The markings in the diagram are explained as follows:

[0029] 000—High current protection element;

[0030] 100 — Ceramic substrate back-side circuit module;

[0031] 200—Ceramic substrate front-side loop module;

[0032] 101—Ceramic substrate;

[0033] 102—Through-plugging conductor;

[0034] 103a—External electrode, 103b—Top electrode on the back side;

[0035] 104a – Electrode a is introduced; 104b – Electrode b is introduced.

[0036] 105 – Heating element; 106 – Insulation layer;

[0037] 107—Intermediate electrode; 108—Solder;

[0038] 109 – Back-side fuse assembly; 110 – Flux for fusing;

[0039] 111 – Blocking line; 112 – Back cover;

[0040] 113 – Support conductor terminal; 114 – Through hole;

[0041] 201 – Front top electrode; 202 – Front fuse assembly;

[0042] 203 – Front cover; 204 – Adhesive. Detailed Implementation

[0043] Hereinafter, the high-current protection element of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, the present invention is not limited to the embodiments described below, and various modifications can be made without departing from the essential points of the invention. Additionally, the drawings are schematic, and the proportions of various dimensions may differ from reality. Specific dimensions should be determined by referring to the following description. Furthermore, it is obvious that even among the drawings, there may be differences in position, size, proportion, or relationship between them.

[0044] There are multiple ways to implement the high-current protection element of this invention, and the embodiments are as follows:

[0045] Example 1

[0046] A protective element, such as Figure 1 A cross-sectional structural schematic diagram of the high-current protection element of the present invention. Figure 2 The schematic diagram of the high-current protection element of the present invention and Figure 3 are planar schematic diagrams of the ceramic substrate back circuit module (omitting the cover component) and the ceramic substrate front circuit module (omitting the cover component) of the present invention, wherein... Figure 3-1 This is a schematic diagram of the rear loop module; Figure 3-2 Schematic diagram of the front loop module:

[0047] The present invention provides a protection element equivalent to a high-current protection element 000 consisting of two independent protection elements connected in parallel, while... Figure 1 As shown, the high current protection element 000 can be considered as Figure 3-1 The back loop module 100 and Figure 3-2 The front circuit module 200 is stacked on both sides of the ceramic substrate and connected to the external circuit through the supporting conductor terminal 113.

[0048] like Figure 1 and Figure 3-1As shown, the ceramic substrate back-side circuit module 100 includes: a ceramic substrate 101 having a plurality of plug conductors 102 and through holes 114; a heating element 105 stacked on the ceramic substrate 101 and covered by an insulating layer 106; back-side upper electrodes 103b formed at both ends of the ceramic substrate 101; lead-in electrodes a104a and b104b formed on the ceramic substrate 101 as current leads for the heating element 105; a heating element lead-out electrode—intermediate electrode 107 stacked on the insulating layer 106 in an overlapping manner with the heating element 105; and a back-side fuse assembly 109 bridging the back-side upper electrodes 103b at both ends with solder 108. Above the hot lead electrode—intermediate electrode 107, the blocking line 111 acts as a limit; flux 110 is added above the center of the back fuse assembly 109; the back cover component 112 is bonded to the ceramic substrate 101 with adhesive 204, covering the back fuse assembly 109 and other components, while ensuring sufficient internal space; the back upper electrode 113b is connected to the external electrode 103a, and the external electrode 113a and the lead electrode a104a are provided with one or more supporting conductor terminals 113. All supporting conductor terminals 113 are coplanar and are higher than or not lower than the height of the back cover component 112, serving as access terminals for external circuits;

[0049] like Figure 1 and Figure 3-2 As shown, the structure of the ceramic substrate front circuit module 200 is similar to that of the ceramic substrate back circuit module 100, and includes: a ceramic substrate 101 with a plurality of plug conductors 102 and through holes 114; a heating element 105 stacked on the ceramic substrate 101 and covered by an insulating layer 106; front electrodes 201 formed at both ends of the ceramic substrate 101; and lead-in electrodes a104a and b104b formed on the ceramic substrate 101 as current leads to and from the heating element 105; and electrodes 201 on the insulating layer 106 and the heating element 105. The heating element lead-out electrode—intermediate electrode 107 is stacked in an overlapping manner; the front fuse assembly 202 is bridging and soldered to the front upper electrode 201 and the heating element lead-out electrode—intermediate electrode 107 at both ends by solder 108, at which time the blocking line 111 acts as a limit; the fluxing agent 110 is added to the center of the front fuse assembly 109; the front cover component 203 is bonded to the ceramic substrate 101 by adhesive 204, covering the front fuse assembly 202 and other components, while ensuring sufficient internal space.

[0050] The ceramic substrate 101 can be formed in a generally square shape using insulating materials such as alumina, glass ceramics, mullite, and zirconium oxide. Alternatively, the ceramic substrate 101 can also be made of materials used for printed wiring substrates, such as glass oxide substrates and phenolic substrates, but care must be taken to consider the temperature at which the fuse assembly melts.

[0051] The ceramic substrate 101 has several pairs of plugging holes (filled with plugging conductors 102) or through holes 114, wherein the plugging conductors 102 can be conductors with low resistivity that are mainly Ag.

[0052] The lead-in electrode a104a, lead-in electrode b104b, front upper electrode 201, middle electrode 107, back upper electrode 103b, and their connecting external electrode 103a are all low resistivity conductors, primarily composed of Ag, and all serve to carry current. Specifically, lead-in electrodes a104a and b104b function as current-introducing and leading conductors for the heating element 105, with one or more supporting conductor terminals 113 (P3) on lead-in electrode a104a; the front upper electrode 201, back upper electrode 103b, and middle electrode 107 are all fuse assemblies spanning the welding position; the back upper electrode 113b, connected to the external electrode 103a, has one or more supporting conductor terminals 113 (P1) and 113 (P2).

[0053] The heating element 105 is a conductive component with an ohmic resistance value that generates heat when energized, and is made of materials such as W, Mo, Ru, Ag, and Pd. These alloys or compounds are mixed in powder form with resin binders to form a paste, which is then screen-printed onto a ceramic substrate 101 and subsequently sintered at high temperature.

[0054] The insulating layer 106 is a highly insulating component with high voltage resistance. For example, it is formed by mixing glass powders such as alumina and silica with resin binders to form a paste, and then using screen printing technology. The insulating layer 106 is configured to cover the heating element 105.

[0055] The back fuse assembly 109 and the front fuse assembly 202 melt rapidly due to the heating of the heating element, and are conductor materials with low resistivity and suitable melting point range. For example, lead-free solder with Sn as the main component, alloy high-melting-point solder with Sn, Pb, Ag or other such main components, or conductor units formed by layering and wrapping low-melting-point and high-melting-point (Ag, Cu or such as these as the main components).

[0056] Solder 108 is similar in material to the fuse assembly and is used to weld the fuse assembly across.

[0057] Fusible interfering agent 110 is added to the fuse assembly to improve the wettability of the fuse assembly during melting and to prevent oxidation of the fuse assembly. It can be a mixture of at least one of free natural rosin, polymerized rosin, and hydrogenated rosin.

[0058] The supporting conductor terminal 113 is a metal bump or metal pillar, which is soldered to an external electrode. It supports the ceramic substrate at a height that is not higher than or equal to the back cover component 112, and all terminals are coplanar. This allows the supporting conductor terminal 113(P1) to be connected to an external circuit, such as... Figure 2 As shown, current can flow in from the support conductor terminal 113 (P1) on the external electrode on one side, and then flow through the back fuse assembly 109 and the front fuse assembly 202 through the plug conductor 102, and finally flow out from the support conductor terminal 113 (P1) on the external electrode on the other side of the ceramic substrate. The support conductor terminal 113 (P3) is located on the input electrode a104a, which allows external voltage or current to enter from the support conductor terminal 113 (P3). The through hole 114 (Q1) serves as a connection point. The heating elements 105 on the front and back sides of the ceramic substrate work simultaneously, and simultaneously melt the back fuse assembly 109 and the front fuse assembly 202 to achieve the circuit cut-off function.

[0059] Example 2

[0060] One type of protective element differs from Embodiment 1 in that the front loop module does not contain a heating element or its heating circuit, such as... Figure 4 Schematic diagrams of other modifications of the high-current protection element of the present invention. Figure 5 Figure 6 is a cross-sectional structural schematic diagram of other modifications of the high-current protection element of the present invention, and a plan view of other modifications of the ceramic substrate back circuit module and the ceramic substrate front circuit module without the cover component of the present invention. Figure 6-1 This is a schematic diagram of the rear loop module. Figure 6-2 The schematic diagram of the front loop module is shown below:

[0061] Other variations of the rear loop module and the front loop module applicable to the present invention will be described. In the following description, the same reference numerals are used for the same parts as those in the rear loop module 100 and the front loop module 200, and their details are omitted.

[0062] Figure 4 This is a schematic diagram illustrating the principle of other variations of the high-current protection element of the present invention. Compared to Figure 2 Alternatively, only one heating element can be provided, which can be located on the back side or the front side of the ceramic substrate, thus creating two different variant embodiments.

[0063] When the heating element is located on the back side of the ceramic substrate, please refer to the cross-sectional structural diagram for details. Figure 5 In the plan view 6 omitting the cover component, here are other modified examples of the ceramic substrate back circuit module diagram. Figure 6-1 and Figure 3-1Similarly; planar schematic of other variations of the front-side loop module diagram of the ceramic substrate. Figure 6-2 and Figure 3-2 Slightly different.

[0064] The ceramic substrate front circuit module 200 structure includes: a plurality of plug conductors 102 and through holes 114 disposed on the front side of a ceramic substrate 101; front upper electrodes 201 formed at both ends of the ceramic substrate 101; an intermediate electrode 107 stacked in the middle of the front side of the ceramic substrate 101; a front fuse assembly 202 bridging the front upper electrodes 201 and the intermediate electrode 107 at both ends by solder 108, at which time the blocking line 111 acts as a limit; flux 110 added above the center of the back fuse assembly 109; and a front cover component 203 bonded to the ceramic substrate 101 by adhesive 204, covering the front fuse assembly 202 and other components, while ensuring sufficient internal space.

[0065] This allows the support conductor terminal 113(P1) and the support conductor terminal 113(P1) to be connected to an external circuit, such as... Figure 4 As shown, current can flow in from the support conductor terminal 113 (P1) on one side of the external electrode, and then flow through the back fuse assembly 109 and the front fuse assembly 202 through the plug conductor 102, and finally flow out from the support conductor terminal 113 (P1) on the other side of the ceramic substrate. The support conductor terminal 113 (P3) is located on the input electrode a104a, which allows external voltage or current to enter through the support conductor terminal 113 (P3), so that the heating element 105 on the back of the ceramic substrate works, and at the same time melts the back fuse assembly 109 and the front fuse assembly 202 to achieve the function of cutting off the circuit.

[0066] Example 3

[0067] One type of protective element differs from Embodiment 1 in that the rear circuit module does not contain a heating element or its heating circuit, such as... Figure 7 Figure 8 is a cross-sectional structural schematic diagram of other modifications of the high-current protection element of the present invention, and a plan view of other modifications of the ceramic substrate back circuit module and the ceramic substrate front circuit module without the cover component of the present invention. Figure 8-1 Schematic diagram of the rear loop module. Figure 8-2 The schematic diagram of the front loop module is shown below:

[0068] This embodiment uses only one heating element, unlike Embodiment 2, the heating element is located in the front circuit module. The arrangement of the heating element on the front side of the ceramic substrate will now be described. In the high-current protection elements described below, components identical to those in the high-current protection element 000 described above are labeled with the same reference numerals, and their details are omitted.

[0069] When the heating element is located on the front side of the ceramic substrate 101, see the cross-sectional structural diagram for details. Figure 7 And a plan view of the ceramic substrate front circuit module diagram 8 (without the cover component omitted), and other variations thereof. Figure 8-2 and Figure 3-2 Similarly; planar schematic of other variations of the ceramic substrate back-side loop module diagram. Figure 8-1 and Figure 3-1 Slightly different.

[0070] The ceramic substrate back-side circuit module 100 includes: a ceramic substrate 101 having a plurality of plug conductors 102 and through holes 114; back-side upper electrodes 103b formed at both ends of the ceramic substrate 101; an introduction electrode a104a formed on the ceramic substrate 101; an intermediate electrode 107 stacked in the middle of the back side of the ceramic substrate 101; a back-side fuse assembly 109 being soldered across the back-side upper electrodes 103b and the intermediate electrode 107 at both ends by solder 108, at which time the blocking line 111 acts as a limit; and a flux 110 being added to the center of the back-side fuse assembly 109.

[0071] The support conductor terminal 113(P1) can be connected to an external circuit. Current can flow in from the support conductor terminal 113(P1) on one side of the external electrode, and then flow through the back fuse assembly 109 and the front fuse assembly 202 through the plug conductor 102, and finally flow out from the support conductor terminal 113(P1) on the other side of the ceramic substrate. The support conductor terminal 113(P3) is located on the inlet electrode a of 104a, which allows external voltage or current to enter through the support conductor terminal 113(P3), and through the through hole 114(Q1) to make the heating element 105 on the front side of the ceramic substrate work, while melting the front fuse assembly 109 and the front fuse assembly 202 to realize the circuit cut-off function.

[0072] The above embodiment is merely an example for ease of understanding. Researchers or engineers in this field may make minor adjustments by changing one or a few steps, but the schematic diagram remains the same. Figure 1 All structures are considered to be within the scope of the claims of this patent application.

Claims

1. A protective element comprising a ceramic substrate and electrodes, characterized in that, The ceramic substrate is provided with several conductor plugs and through holes; A heating element is disposed on the front and / or back of a ceramic substrate; An insulating layer is stacked on a ceramic substrate and covers the heating element; The top electrode is divided into a front top electrode and a back top electrode, which are stacked on the front and back sides of the ceramic substrate, respectively. The intermediate electrode is divided into a front intermediate electrode and a back intermediate electrode, which are connected to the lead-out electrodes of the heating element located on the same side. The fuse assembly is stacked on both the front and back sides of the ceramic substrate and is divided into a front fuse assembly and a back fuse assembly. Electrically, it provides dual current paths on both the front and back sides, and can melt simultaneously when current or voltage flows through the heating element. Both the front fuse assembly and the back fuse assembly are connected to an upper electrode and a middle electrode, and both are provided with fluxing agent. The housing is divided into a front housing and a back housing, which form a certain space with the ceramic substrate, including but not limited to the fuse assembly within the space; The back electrode is connected to the external electrode. Multiple supporting conductor terminals are provided on the external electrode. All supporting conductor terminals are coplanar and are higher than or not lower than the height of the back shell. These supporting conductor terminals are metal bumps or metal pillars and are soldered to the external electrode by solder. Through these supporting conductor terminals, external current flows in from the supporting conductor terminals on one side of the external electrode, and then flows through the front fuse assembly and the back fuse assembly, finally flowing out from the supporting conductor terminals on the external electrode on the other side of the ceramic substrate; external voltage or current enters from the port of the third supporting conductor terminal, the heating element works, and at the same time melts the front fuse assembly and the back fuse assembly, realizing the circuit cut-off function.

2. The protective element as described in claim 1, characterized in that, The fuse assemblies on the front and back sides of the ceramic substrate are connected in parallel through several plug holes provided in the ceramic substrate.

3. A protective element as described in claim 1, characterized in that, Fuse assemblies are conductor materials with low resistivity and suitable melting point range, including lead-free solder with Sn as the main component, and high-melting-point alloy solder with Sn, Pb or Ag as the main components, which are formed by stacking or wrapping to form structural conductor units; or low-melting-point metals and high-melting-point metals Ag, Cu or materials with these as the main components, which are formed by stacking or wrapping to form structural conductor units.

4. A protective element as described in claim 1, characterized in that, The front top electrode and the front middle electrode are connected to the front fuse assembly, and the back top electrode and the back middle electrode are connected to the back fuse assembly. The welding method is high-temperature welding or reflow welding.

5. A protective element as described in any one of claims 1 to 4, characterized in that, This is equivalent to a high-current protection element consisting of two independent protection elements connected in parallel. The high-current protection element is considered as a back-side circuit module and a front-side circuit module stacked on the front and back sides of a ceramic substrate, connected to an external circuit via supporting conductor terminals; wherein, The ceramic substrate is provided with several plug conductors and through holes; The ceramic substrate back-side circuit module comprises: a heating element stacked on the back of the ceramic substrate and covered with an insulating layer; back-side upper electrodes formed at both ends of the ceramic substrate; lead-in electrodes a and b formed on the ceramic substrate as current leads for the heating element; a heating element lead-out electrode—intermediate electrode—stacked on the insulating layer in an overlapping manner with the heating element; a back-side fuse assembly bridging and soldering the back-side upper electrodes and the heating element lead-out electrode—intermediate electrode at both ends, where the blocking line acts as a limit; a fluxing agent added above the center of the back-side fuse assembly; a back-side cover component bonded to the ceramic substrate with adhesive, covering the back-side components including the fuse assembly while ensuring sufficient internal space; a back-side upper electrode connected to an external electrode, wherein the external electrode and lead-in electrode a are provided with three supporting conductor terminals, all of which are coplanar and are higher than or not lower than the height of the back-side cover component, serving as access terminals for external circuits; The ceramic substrate front circuit module structure and the ceramic substrate back circuit module include: a heating element stacked on the front of the ceramic substrate and covered with an insulating layer; front upper electrodes formed at both ends of the ceramic substrate; lead-in electrodes a and b formed on the ceramic substrate as current leads for the heating element; a heating element lead-out electrode—intermediate electrode—stacked on the insulating layer in an overlapping manner with the heating element; a front fuse assembly bridging and soldering the front upper electrodes and the heating element lead-out electrode—intermediate electrode at both ends; a blocking line for limiting; a fluxing agent added to the center of the front fuse assembly; and a front cover component bonded to the ceramic substrate with adhesive, covering the electrical components on the front including the fuse assembly, while ensuring sufficient internal space. After the current flows in from the support conductor terminal P1 on the external electrode on one side, it flows through the back fuse assembly and the front fuse assembly through the hole-blocking conductor, and finally flows out from the support conductor terminal P2 on the external electrode on the other side of the ceramic substrate. The support conductor terminal P3 is located on the input electrode a, so that the external voltage or current can enter from the support conductor terminal P3. The through hole serves as the connection point, and the heating elements on the front and back sides of the ceramic substrate work simultaneously, melting the back fuse assembly and the front fuse assembly at the same time, thus realizing the circuit cut-off function.

6. A protective element as described in claim 5, characterized in that, No heating element is installed in the front loop module.

7. A protective element as described in claim 5, characterized in that, No heating element is installed in the rear loop module.

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