A three-terminal fuse structure based on a circuit board structure and a manufacturing method thereof

Abstract

The application relates to the technical field of circuit protection, and provides a three-terminal protection structure based on a circuit board structure, which comprises a supporting body, a heating body and a protection circuit; an insulating layer is arranged on the supporting body, and the heating body is arranged between the supporting body and the insulating layer; an inflow pad, an outflow pad and a control pad are arranged on the insulating layer; the protection circuit is located above the insulating layer and is electrically connected with the inflow pad, the outflow pad and the control pad respectively; the heating body is electrically connected with the inflow pad and the control pad and forms a control circuit; under an overcurrent state, the protection circuit is fused; under an overvoltage state, the heating body generates heat, and the generated heat penetrates through the insulating layer to fuse the protection circuit. The application replaces a ceramic substrate with a commonly used substrate of a printed circuit board, so that the three-terminal circuit protection unit can be mass-produced in a large area, the cost is reduced, and the overall thickness of components and devices is reduced.

Description

Technical Field

[0001] This invention relates to the field of circuit protection technology, and in particular to a three-terminal fuse structure based on a circuit board structure and its manufacturing method. Background Technology

[0002] Circuit protection is designed to prevent electronic equipment from being damaged by abnormal voltage or current surges. It automatically triggers the fuses, resistor changes, or other physical changes in relevant functional components to cut off the circuit or suppress sudden changes in current or voltage. As the integration of electronic equipment increases, the role of circuit protection devices becomes particularly important in order to reduce energy loss, reduce heat generation, and extend service life.

[0003] Circuit protection devices are widely used in various electronic products and power systems, especially in consumer electronics such as mobile phones and laptops, as well as in vehicle-mounted equipment and communication devices, to ensure their stable and safe operation. Three-terminal fuses are an important protective device for electronic equipment, primarily used to prevent damage caused by overcurrent, short circuits, and overvoltage. Their core principle is to utilize the properties of conductive materials to automatically disconnect the circuit when the current exceeds a set value, thereby reducing damage to the electronic equipment. The working principle of three-terminal fuses includes thermal protection, electromagnetic protection, and overvoltage protection. These mechanisms ensure a rapid response and interruption of current when abnormalities occur in the circuit, thus providing protection.

[0004] In existing technologies, the substrate of a three-terminal fuse is usually a ceramic substrate, and the electrodes and fusible metal are both disposed on the ceramic substrate. This has at least the following technical problems: due to the characteristics of the ceramic substrate, the overall thickness of the three-terminal fuse is increased; the manufacturing process involves more steps, resulting in low production efficiency and high cost. Summary of the Invention

[0005] The main objective of this invention is to provide a three-terminal fuse structure based on a circuit board structure, aiming to solve the technical problems of large thickness and high manufacturing cost of three-terminal fuses.

[0006] To achieve the above objectives, the present invention provides a three-terminal fuse structure based on a circuit board structure, including a support, a heating element, and a fuse circuit;

[0007] An insulating layer is provided on the support body, and the heating element is disposed between the support body and the insulating layer;

[0008] The insulating layer is provided with inflow pads, outflow pads and control pads;

[0009] The fuse circuit is located above the insulating layer and is electrically connected to the inflow pad, outflow pad, and control pad respectively. The heating element is electrically connected to the inflow pad and control pad to form a control circuit.

[0010] Under overcurrent conditions, the fuse blows.

[0011] Under overvoltage conditions, the heating element heats up, and the heat generated passes through the insulation layer and melts the fuse circuit.

[0012] Optionally, it also includes three separate terminals: an inflow terminal, an outflow terminal, and a control terminal, which are electrically connected to the fuse circuit.

[0013] Optionally, the inflow terminal is disposed on the lower surface of the inflow pad, and the inflow terminal is electrically connected to the fuse circuit through the inflow pad;

[0014] The outgoing terminal is located on the lower surface of the outgoing pad, and the outgoing terminal is electrically connected to the fuse circuit through the outgoing pad;

[0015] The control terminal is located on the lower surface of the insulating layer, and the control terminal is electrically connected to the control pad through the heating element.

[0016] Optionally, the inflow terminal, outflow terminal, and control terminal are disposed on the lower surface of the support body. The inflow terminal is electrically connected to the inflow pad through the inflow end conductive hole, the outflow terminal is electrically connected to the outflow pad through the outflow end conductive hole, and the control terminal is electrically connected to the control pad through the heating element.

[0017] Optionally, the control terminal is electrically connected to the control pad through the heating element as follows: both ends of the heating element are provided with heating pads, the control terminal is electrically connected to the heating pad at one end of the heating element through a heating conductive hole, and the control pad is electrically connected to the heating pad at the other end of the heating element through a heating conductive hole.

[0018] Optionally, a flux layer is provided on the fuse circuit, and the longitudinal projection position of the flux layer coincides with the longitudinal projection position of the heating element by 80% to 100% of its area. The longitudinal projection position of the heating element is located within the longitudinal projection of the fuse circuit.

[0019] Optionally, it also includes a top cover, which covers the insulating layer, and the flux layer and fuse circuit are located in the space formed by the top cover and the insulating layer.

[0020] Optionally, the material of the support includes at least one of the following: glass fiber, epoxy resin, phenolic resin, polyimide, polytetrafluoroethylene, and BT resin; the material of the insulation layer includes at least one of the following: glass fiber, epoxy resin, phenolic resin, polyimide, polytetrafluoroethylene, and BT resin.

[0021] Optionally, the insulating layer has heat-conducting holes uniformly arranged in the upper or lower half; or, the insulating layer has heat-conducting holes staggered in the upper and lower half and uniformly arranged; the heat-conducting holes are filled with a material with high thermal conductivity.

[0022] Another aspect of the present invention provides a method for manufacturing a three-terminal fuse structure based on a circuit board structure, comprising the following steps:

[0023] Step 1: Material preparation; provision of support structure;

[0024] The support is a substrate with three separate terminals at the bottom;

[0025] Alternatively, the support is a copper frame filled with molding compound, and the copper frame consists of three separate terminals;

[0026] The three separate terminals are the inflow terminal, the outflow terminal, and the control terminal;

[0027] Step 2: First graphic creation; Create the graphic on the upper surface of the support, add the heating element, and add heating pads at both ends of the heating element;

[0028] Step 3: Pressing; Press the insulating layer and copper foil onto the upper surface of the support and the heating element, with the copper foil forming at least three pads;

[0029] The three pads are the inflow pad, the outflow pad, and the control pad;

[0030] Step 4: Drilling; Drill holes in the pressed support and insulating plate to obtain: conductive holes for the inflow terminals and inflow pads; conductive holes for the outflow terminals and outflow pads; conductive holes for the control terminals and heating pads, and conductive holes for the control pads and heating pads.

[0031] Step 5: Metallization of conductive holes; resulting in conductive inflow end conductive holes, outflow end conductive holes, and heating end conductive holes;

[0032] Step Six: Second graphic creation; create the wiring on the upper and lower surfaces of the three-terminal safety structure;

[0033] Step 7: Fuse fabrication;

[0034] Solder the fuse circuit on the inflow pad, outflow pad, and control pad;

[0035] Alternatively, a layer of pure metal or alloy can be added to the inflow pad, outflow pad, and control pad, which serves as a safety circuit.

[0036] Step 8: Apply flux;

[0037] After slotting the insulating film to obtain a receiving groove, it is then pressed onto the insulating layer, the fuse circuit, the inflow pad, the outflow pad, and the control pad to form a flux insulating layer. Flux is then applied into the receiving groove to obtain a flux layer that at least covers part of the upper surface of the fuse circuit. Solder resist material is then applied to the upper surface of the flux insulating layer to obtain a solder resist layer.

[0038] Alternatively, flux can be applied directly to the fuse circuit to obtain a flux layer that at least partially covers the upper surface of the fuse circuit;

[0039] Step 9: Attach the cap; attach the top cap to the upper surface of the flux insulation layer;

[0040] Alternatively, the top cover can be bonded to the upper surface of the insulation layer;

[0041] Complete the fabrication of the three-terminal safety structure.

[0042] Beneficial effects: The technical solution provided by this invention uses a substrate commonly used in printed circuit boards to replace the ceramic substrate, thereby enabling the use of processes such as lamination and planar embedded resistors in the manufacturing process. This allows for the mass production of three-terminal fuse structures. Unlike ceramic substrates, which have smaller unit sizes in a single processing step, resin or organic substrates have larger unit sizes in a single processing step, thus increasing the number of three-terminal fuse structures produced per batch, improving production efficiency, and reducing costs. The commonly used substrate in printed circuit boards allows the heating element, fuse layer, and flux layer to be embedded inside the substrate, making the overall three-terminal fuse structure compact, reasonable, and reducing the overall thickness.

[0043] The manufacturing method of the three-terminal safety structure is suitable for mass production, with low production costs and high efficiency. Attached Figure Description

[0044] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0045] Figure 1 This is a cross-sectional schematic diagram of the three-end safety structure according to Embodiment 1 of the present invention;

[0046] Figure 2 This is a cross-sectional view of the three-end safety structure according to Embodiment 1 of the present invention from another angle;

[0047] Figure 3 This is a cross-sectional view of the three-end safety structure according to Embodiment 1 of the present invention from another angle;

[0048] Figure 4 This is a schematic diagram of the welding fuse circuit and the cross-sectional structure with added flux of the three-terminal fuse structure according to Embodiment 1 of the present invention.

[0049] Figure 5 This is a cross-sectional schematic diagram of the insulating layer of a three-terminal safety structure according to an embodiment of the present invention;

[0050] Figure 6 This is an exploded view of the three-terminal safety structure according to Embodiment 1 of the present invention;

[0051] Figure 7 This is a cross-sectional schematic diagram of the electroplated fuse circuit of the three-terminal fuse structure according to Embodiment 2 of the present invention;

[0052] Figure 8 This is a cross-sectional schematic diagram of the three-terminal safety structure of the present invention with the addition of a flux insulation layer and a flux layer in Embodiment 2 of the present invention;

[0053] Figure 9 This is a cross-sectional structural diagram of the three-terminal safety structure of the present invention with added solder resist layer and top cover in Embodiment 2 of the present invention;

[0054] Figure 10 This is a cross-sectional schematic diagram of the three-end safety structure according to Embodiment 3 of the present invention;

[0055] Figure 11 This is a cross-sectional structural diagram of the support body of the three-end safety structure according to Embodiment 3 of the present invention;

[0056] Figure 12 This is a schematic diagram of the welding fuse circuit and the cross-sectional structure with added flux of the three-terminal fuse structure according to Embodiment 3 of the present invention;

[0057] Figure 13 This is a cross-sectional schematic diagram of the electroplated fuse circuit of the three-terminal fuse structure according to Embodiment 4 of the present invention;

[0058] Figure 14 This is a cross-sectional schematic diagram of the three-terminal safety structure with added flux insulation layer according to Embodiment 4 of the present invention;

[0059] Figure 15 This is a cross-sectional schematic diagram of the three-terminal safety structure with added flux layer according to Embodiment 4 of the present invention;

[0060] Figure 16 This is a cross-sectional schematic diagram of the three-terminal safety structure with added solder resist layer according to Embodiment 4 of the present invention;

[0061] Figure 17 This is a cross-sectional schematic diagram of the three-end safety structure according to Embodiment 4 of the present invention;

[0062] Figure 18 This is a cross-sectional schematic diagram of the three-end safety structure according to Embodiment 5 of the present invention;

[0063] Figure 19 This is a cross-sectional view of the three-end safety structure of Embodiment 5 of the present invention from another angle;

[0064] Figure 20 This is an exploded view of the three-terminal safety structure of Embodiment 5 of the present invention;

[0065] Figure 21 This is a cross-sectional view of the three-end safety structure of Embodiment 5 of the present invention from another angle.

[0066] Reference numerals: Support body 10, molding layer 101, insulating layer 11, heating end conductive hole 111, heat conduction hole 112, fuse circuit 12, heating element 13, heating end pad 131, inflow terminal 14, inflow end conductive hole 141, outflow terminal 15, outflow end conductive hole 151, control terminal 16, inflow pad 17, outflow pad 18, control pad 19, solder resist layer 20, protective layer 21, flux layer 22, top cover 23, flux insulating layer 24, receiving channel 241. Detailed Implementation

[0067] To facilitate understanding of the present invention, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is described as being "fixed to" another element, it can be directly on the other element, or one or more intermediate elements may exist between them. When an element is described as being "connected to" another element, it can be directly connected to the other element, or one or more intermediate elements may exist between them. The terms "vertical," "horizontal," "left," "right," "inner," "outer," and similar expressions used in this specification are for illustrative purposes only. In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating relative importance or implying the number of indicated technical features. Thus, unless otherwise stated, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; "multiple" means two or more. The term "comprising" and any variations thereof mean non-exclusive inclusion, where one or more other features, integers, steps, operations, units, components, and / or combinations thereof may be present or added.

[0068] Furthermore, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections via an intermediate medium, or internal communication between two components. All technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0069] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0070] Example 1

[0071] Please refer to Figures 1-6 A three-terminal fuse structure based on a circuit board structure includes a support body 10, a heating element 13, and a fuse circuit 12.

[0072] An insulating layer 11 is provided on the support body 10, and the heating element 13 is disposed between the support body 10 and the insulating layer 11;

[0073] The insulating layer 11 is provided with inflow pad 17, outflow pad 18 and control pad 19;

[0074] The fuse circuit 12 is located above the insulating layer 11 and is electrically connected to the inflow pad 17, the outflow pad 18, and the control pad 19 respectively. The heating element 13 is electrically connected to the inflow pad 17 and the control pad 19 to form a control circuit.

[0075] Under overcurrent conditions, fuse 12 blows;

[0076] Under overvoltage conditions, the heating element 13 heats up, and the heat generated passes through the insulation layer 11 and melts the fuse circuit 12.

[0077] In the technical solution provided by this invention, a substrate commonly used in printed circuit boards is used instead of a ceramic substrate, thereby enabling the use of processes such as lamination and planar buried resistors in the manufacturing process. This allows for the mass production of three-terminal fuse structures. Unlike ceramic substrates, resin substrates or organic substrates have a larger unit size per processing step, which increases the number of three-terminal fuse structures produced per batch, improves production efficiency, and reduces costs. The commonly used substrate in printed circuit boards allows the heating element 13, the fusion layer, and the flux layer 22 to be embedded inside the substrate, thereby reducing the overall thickness of the three-terminal fuse structure.

[0078] In this embodiment, three separate terminals are also included: inflow terminal 14, outflow terminal 15, and control terminal 16. Inflow terminal 14, outflow terminal 15, and control terminal 16 are electrically connected to the fuse circuit 12.

[0079] Reference Figure 2 The inflow terminal 14, the outflow terminal 15, and the control terminal 16 are disposed on the lower surface of the support body 10. The inflow terminal 14 is electrically connected to the inflow pad 17 through the inflow end conductive hole 141, the outflow terminal 15 is electrically connected to the outflow pad 18 through the outflow end conductive hole 151, and the control terminal 16 is electrically connected to the control pad 19 through the heating element 13.

[0080] In this embodiment, please refer to the specific details. Figure 3 The control terminal 16 is electrically connected to the control pad 19 through the heating element 13 as follows: both ends of the heating element 13 are provided with heating end pads 131. The control terminal 16 and the heating end pad 131 at one end of the heating element 13 are electrically connected through the heating end conductive hole 111. The control pad 19 and the heating end pad 131 at the other end of the heating element 13 are electrically connected through the heating end conductive hole 111.

[0081] The inflow terminal 14 and the outflow terminal 15 are connected in series with the external overcurrent protection circuit. The inflow terminal 14 and the control terminal 16 are connected in series with the external overvoltage protection circuit. The external overcurrent protection circuit and the overvoltage protection circuit are connected in parallel. The overvoltage protection circuit is equipped with a MOSFET. When the voltage on the overvoltage protection circuit reaches the protection threshold, the MOSFET will cause the overvoltage protection circuit to change from an open circuit to a closed circuit.

[0082] The fuse circuit 12 is made of a thin layer of metal and forms a weak electrical connection with the external circuit. The weak electrical connection allows the current to pass through the fuse circuit 12 normally without causing the fuse circuit 12 to blow during normal circuit operation. However, when the external circuit is operating under overcurrent and / or overvoltage conditions, the fuse circuit 12 can blow quickly.

[0083] The material of the fuse circuit 12 is usually at least one of tin, lead, copper, silver, zinc, aluminum, and any combination thereof, and in this embodiment, tin is preferred.

[0084] In the overcurrent state, the current flows sequentially into terminal 14, into pad 17, fuse circuit 12, out of pad 18 and out of terminal 15; at this time, fuse circuit 12 heats up and melts itself, thereby changing the overcurrent protection circuit from a closed circuit to an open circuit.

[0085] Under overvoltage conditions, the MOSFET in the overvoltage protection circuit causes the overvoltage protection circuit to switch from an open circuit to a closed circuit. The overvoltage current flows sequentially into terminal 14, pad 17, fuse circuit 12, control pad 19, heating element 13, and control terminal 16. It should be noted that the heating element 13 is made of a resistor. When the overvoltage current passes through the heating element 13, the heating element 13 heats up. The heat generated by the heating element 13 passes through the insulating layer 11, thereby causing the fuse circuit 12 to melt and the overvoltage protection circuit to switch from a closed circuit to an open circuit.

[0086] In this embodiment, refer to Figure 4 The fuse circuit 12 is provided with a flux layer 22. The longitudinal projection position of the flux layer 22 coincides with the longitudinal projection position of the heating element 13 by 80% to 100% of its area. The longitudinal projection position of the heating element 13 is located within the longitudinal projection of the fuse circuit 12.

[0087] The flux layer 22 assists in the melting of the fuse circuit 12. The longitudinal projection positions of the flux layer 22 and the heating element 13 coincide, so that when the heat from the heating element 13 is transferred to the fuse circuit 12, the flux layer 22 can better promote the melting of the fuse circuit 12 and improve the melting sensitivity of the fuse circuit 12. The longitudinal projection positions of the flux layer 22 and the heating element 13 overlap by 80%, 90%, or 100% of their area, with 100% overlap being the most preferred. The longitudinal projection position of the heating element 13 is located within the longitudinal projection of the fuse circuit 12, so that the heat from the heating element 13 can be accurately transferred to the fuse circuit 12, thereby causing the fuse circuit 12 to melt under overvoltage conditions.

[0088] In this embodiment, the material of the support 10 includes at least one or more of the following: glass fiber material, epoxy resin material, phenolic resin material, polyimide material, polytetrafluoroethylene material, and BT resin material.

[0089] Specifically, the material of the support 10 can be glass fiber, epoxy resin, phenolic resin, polyimide, polytetrafluoroethylene, BT resin, or other commonly used resin substrates and organic substrates that can be produced in large areas. Compared with ceramics, resin substrates and organic substrates have the characteristics of high output and low cost, which can further reduce processing costs and improve production efficiency.

[0090] In this embodiment, the support 10 is preferably an FR-4 substrate, but it can also be replaced by other substrates with good heat dissipation, thermal conductivity, and high temperature resistance, except for ceramic substrates. The support 10 can be an FR-4 epoxy glass cloth laminate, made of glass fiber cloth impregnated with epoxy resin, which has good mechanical strength, electrical insulation properties, and high temperature resistance; it can also be a CEM-1 or CEM-2 substrate, which is a paper-based or composite substrate, usually made of cellulose paper impregnated with phenolic resin or epoxy resin; it can also be a polyimide (PI) substrate, which has excellent heat resistance, electrical insulation, and mechanical properties, and is often used in high-performance or high-reliability electronic applications; it can also be a high-Tg material, where Tg represents the glass transition temperature. High-Tg materials remain stable at high temperatures and are suitable for applications requiring high reliability.

[0091] The support 10 uses common printed circuit board substrate materials. Printed circuit board drilling, embedded resistors and capacitors, lamination and other processes are relatively mature. Large-area lamination can be directly carried out during manufacturing, resulting in high production efficiency and reduced costs. However, ceramic substrates are limited by the ceramic material itself and cannot be manufactured in large areas, resulting in lower production efficiency and higher costs.

[0092] In this embodiment, the insulating layer 11 is made of at least one or more of the following materials: glass fiber, epoxy resin, phenolic resin, polyimide, polytetrafluoroethylene, and BT resin.

[0093] Specifically, the insulating layer 11 can be made of glass fiber, epoxy resin, phenolic resin, polyimide, polytetrafluoroethylene, polyester film, BT resin, etc.

[0094] In this embodiment, the insulating layer 11 is preferably made of materials such as BT resin or PP.

[0095] In this embodiment, refer to Figure 5 The insulating layer 11 may have heat-conducting holes 112 uniformly arranged in the upper or lower half; or the upper and lower half of the insulating layer 11 may have heat-conducting holes 112 staggered and uniformly arranged; the heat-conducting holes 112 are filled with a high thermal conductivity material.

[0096] In this embodiment, the high thermal conductivity material filling the heat conduction hole 112 is preferably copper. Specifically, the heat conduction hole 112 is filled by copper plating or copper electroplating, and the thickness of copper plating is preferably 1 to 2 μm, and the thickness of copper electroplating is preferably 12 to 20 μm.

[0097] The heat-conducting holes 112 provided on the insulating layer 11 can serve as heat channels to accelerate heat transfer and speed up the heat transfer rate of the heat generated by the heating element 13. This allows the insulating layer 11 to maintain its overall insulation performance while improving the thermal conductivity of the corresponding local or specific areas of the fuse circuit 12.

[0098] In this embodiment, a top cover 23 is also included, which covers the insulating layer 11. The flux layer 22, the fuse circuit 12, the inflow pad 17, the outflow pad 18, and the control pad 19 are located in the space formed by the top cover 23 and the insulating layer 11.

[0099] The top cover 23 is used to isolate the sparks generated when the fuse circuit 12 and the flux layer 22 melt, so as to prevent the combustion of other external components and devices.

[0100] The manufacturing method of the three-terminal safety structure in this embodiment includes the following steps:

[0101] Step 1: Material preparation; Provide support body 10;

[0102] The support 10 is a commonly used PCB substrate other than ceramic substrate and metal substrate;

[0103] The bottom of the substrate is provided with three separate terminals, namely, inflow terminal 14, outflow terminal 15, and control terminal 16;

[0104] Step 2: First graphic creation; Create the graphic on the upper surface of the support 10, add the heating element 13, and add heating end pads 131 at both ends of the heating element 13;

[0105] Step 3: First pressing; Press the insulating layer 11 and copper foil onto the upper surface of the support 10 and the heating element 13. The copper foil forms at least three pads, namely the inflow pad 17, the outflow pad 18 and the control pad 19.

[0106] Step 4: Drilling; Drill holes in the pressed support 10 and the insulating plate to obtain: inflow end conductive holes 141 that connect the inflow terminal 14 and the inflow pad 17; outflow end conductive holes 151 that connect the outflow terminal 15 and the outflow pad 18; and heating end conductive holes 111 that connect the control terminal 16 and the heating end pad 131, and the control pad 19 and the heating end pad 131.

[0107] Step 5: Metallization of conductive holes; specifically, copper plating and electroplating to make the conductive holes 141 at the inflow end, 151 at the outflow end, and 111 at the heating end conductive holes conductive to conduct electricity.

[0108] The inflow conductive hole 141 and the outflow conductive hole 151 are plugged.

[0109] Step Six: Second graphic creation; create the wiring on the upper and lower surfaces of the three-terminal safety structure;

[0110] Solder resist material is applied to the upper and lower surfaces of the three-terminal safety structure; after surface coating, the entire large substrate is cut into individual product sizes;

[0111] Step 7: Fuse fabrication;

[0112] Solder the fuse circuit 12 on the inflow pad 17, outflow pad 18, and control pad 19;

[0113] Step 8: Apply flux;

[0114] Flux is applied directly to the fuse circuit 12 to obtain a flux layer 22 that covers at least part of the upper surface of the fuse circuit 12;

[0115] Step 9: Attach the lid;

[0116] The top cover 23 is bonded to the upper surface of the insulating layer 11;

[0117] Complete the fabrication of the three-terminal safety structure.

[0118] In existing technologies, three-terminal fuses made using ceramic substrates require up to eight printing processes, making the manufacturing process quite complex. Furthermore, the small area of ​​the ceramic substrate results in fewer fuses produced per batch, leading to higher costs. In contrast, the solution provided in this application uses commonly used PCB substrate materials to fabricate the three-terminal fuse structure. During manufacturing, this substrate has a larger processable area compared to ceramic substrates, allowing for a larger quantity of three-terminal fuses produced per batch, resulting in higher processing efficiency and lower costs. Additionally, this three-terminal fuse structure substrate can be manufactured using common processes such as lamination and planar embedded resistors, and its thickness is also less than that of ceramic substrates, reducing the overall structural thickness. The manufacturing process is also relatively simple and mature.

[0119] Example 2

[0120] Please refer to Figure 5 , Figure 7 , Figure 8 and Figure 9 A three-terminal fuse structure based on a circuit board structure includes a support body 10, a heating element 13, and a fuse circuit 12.

[0121] An insulating layer 11 is provided on the support body 10, and the heating element 13 is disposed between the support body 10 and the insulating layer 11;

[0122] The insulating layer 11 is provided with inflow pad 17, outflow pad 18 and control pad 19;

[0123] The fuse circuit 12 is located above the insulating layer 11 and is electrically connected to the inflow pad 17, the outflow pad 18, and the control pad 19 respectively. The heating element 13 is electrically connected to the inflow pad 17 and the control pad 19 to form a control circuit.

[0124] Under overcurrent conditions, fuse 12 blows;

[0125] Under overvoltage conditions, the heating element 13 heats up, and the heat generated passes through the insulation layer 11 and melts the fuse circuit 12.

[0126] In the technical solution provided in this embodiment, a substrate commonly used in printed circuit boards is used instead of a ceramic substrate. This allows for the use of processes such as lamination and planar buried resistors in the manufacturing process, enabling the mass production of the three-terminal fuse structure. Unlike ceramic substrates, which have smaller unit sizes in a single processing step, resin or organic substrates have larger unit sizes in a single processing step, thereby increasing the number of three-terminal fuse structures produced per batch, improving production efficiency, and reducing costs. The commonly used substrate in printed circuit boards allows the heating element 13, the fusion layer, and the flux layer 22 to be embedded inside the substrate, thereby reducing the overall thickness of the three-terminal fuse structure.

[0127] In this embodiment, three separate terminals are also included: inflow terminal 14, outflow terminal 15, and control terminal 16. Inflow terminal 14, outflow terminal 15, and control terminal 16 are electrically connected to the fuse circuit 12.

[0128] The inflow terminal 14, the outflow terminal 15, and the control terminal 16 are disposed on the lower surface of the support body 10. The inflow terminal 14 is electrically connected to the inflow pad 17 through the inflow end conductive hole 141, the outflow terminal 15 is electrically connected to the outflow pad 18 through the outflow end conductive hole 151, and the control terminal 16 is electrically connected to the control pad 19 through the heating element 13.

[0129] In this embodiment, the control terminal 16 is electrically connected to the control pad 19 through the heating element 13 as follows: both ends of the heating element 13 are provided with heating end pads 131, the control terminal 16 and the heating end pad 131 at one end of the heating element 13 are electrically connected through the heating end conductive hole 111, and the control pad 19 and the heating end pad 131 at the other end of the heating element 13 are electrically connected through the heating end conductive hole 111.

[0130] The inflow terminal 14 and the outflow terminal 15 are connected in series with the external overcurrent protection circuit. The inflow terminal 14 and the control terminal 16 are connected in series with the external overvoltage protection circuit. The external overcurrent protection circuit and the overvoltage protection circuit are connected in parallel. The overvoltage protection circuit is equipped with a MOSFET. When the voltage on the overvoltage protection circuit reaches the protection threshold, the MOSFET will cause the overvoltage protection circuit to change from an open circuit to a closed circuit.

[0131] The fuse circuit 12 is made of a thin layer of metal and forms a weak electrical connection with the external circuit. The weak electrical connection allows the current to pass through the fuse circuit 12 normally without causing the fuse circuit 12 to blow during normal circuit operation. However, when the external circuit is operating under overcurrent and / or overvoltage conditions, the fuse circuit 12 can blow quickly.

[0132] The material of the fuse circuit 12 is usually at least one of tin, lead, copper, silver, zinc, aluminum, and any combination thereof, and in this embodiment, tin is preferred.

[0133] In the overcurrent state, the current flows sequentially into terminal 14, into pad 17, fuse circuit 12, out of pad 18 and out of terminal 15; at this time, fuse circuit 12 heats up and melts itself, thereby changing the overcurrent protection circuit from a closed circuit to an open circuit.

[0134] Under overvoltage conditions, the MOSFET in the overvoltage protection circuit causes the overvoltage protection circuit to switch from an open circuit to a closed circuit. The overvoltage current flows sequentially into terminal 14, pad 17, fuse circuit 12, control pad 19, heating element 13, and control terminal 16. It should be noted that the heating element 13 is made of a resistor. When the overvoltage current passes through the heating element 13, the heating element 13 heats up. The heat generated by the heating element 13 passes through the insulating layer 11, thereby causing the fuse circuit 12 to melt and the overvoltage protection circuit to switch from a closed circuit to an open circuit.

[0135] In this embodiment, a flux layer 22 is provided on the fuse circuit 12. The longitudinal projection position of the flux layer 22 overlaps with the longitudinal projection position of the heating element 13 by 80% to 100% of its area. The longitudinal projection position of the heating element 13 is located within the longitudinal projection of the fuse circuit 12.

[0136] The flux layer 22 assists in the melting of the fuse circuit 12. The longitudinal projection positions of the flux layer 22 and the heating element 13 coincide, so that when the heat from the heating element 13 is transferred to the fuse circuit 12, the flux layer 22 can better promote the melting of the fuse circuit 12 and improve the melting sensitivity of the fuse circuit 12. The longitudinal projection positions of the flux layer 22 and the heating element 13 overlap by 80%, 90%, or 100% of their area, with 100% overlap being the most preferred. The longitudinal projection position of the heating element 13 is located within the longitudinal projection of the fuse circuit 12, so that the heat from the heating element 13 can be accurately transferred to the fuse circuit 12, thereby causing the fuse circuit 12 to melt under overvoltage conditions.

[0137] In this embodiment, the material of the support 10 includes at least one or more of the following: glass fiber material, epoxy resin material, phenolic resin material, polyimide material, polytetrafluoroethylene material, and BT resin material.

[0138] Specifically, the material of the support 10 can be glass fiber, epoxy resin, phenolic resin, polyimide, polytetrafluoroethylene, BT resin, or other commonly used resin substrates and organic substrates that can be produced in large areas. Compared with ceramics, resin substrates and organic substrates have the characteristics of high output and low cost, which can further reduce processing costs and improve production efficiency.

[0139] In this embodiment, the support 10 is preferably an FR-4 substrate, but it can also be replaced by other substrates with good heat dissipation, thermal conductivity, and high temperature resistance, except for ceramic substrates. The support 10 can be an FR-4 epoxy glass cloth laminate, made of glass fiber cloth impregnated with epoxy resin, which has good mechanical strength, electrical insulation properties, and high temperature resistance; it can also be a CEM-1 or CEM-2 substrate, which is a paper-based or composite substrate, usually made of cellulose paper impregnated with phenolic resin or epoxy resin; it can also be a polyimide (PI) substrate, which has excellent heat resistance, electrical insulation, and mechanical properties, and is often used in high-performance or high-reliability electronic applications; it can also be a high-Tg material, where Tg represents the glass transition temperature. High-Tg materials remain stable at high temperatures and are suitable for applications requiring high reliability.

[0140] The support 10 uses common printed circuit board substrate materials. Printed circuit board drilling, embedded resistors and capacitors, lamination and other processes are relatively mature. Large-area lamination can be directly carried out during manufacturing, resulting in high production efficiency and reduced costs. However, ceramic substrates are limited by the ceramic material itself and cannot be manufactured in large areas, resulting in lower production efficiency and higher costs.

[0141] In this embodiment, the insulating layer 11 is made of at least one or more of the following materials: glass fiber, epoxy resin, phenolic resin, polyimide, polytetrafluoroethylene, and BT resin.

[0142] Specifically, the insulating layer 11 can be made of glass fiber, epoxy resin, phenolic resin, polyimide, polytetrafluoroethylene, BT resin, etc.

[0143] In this embodiment, the insulating layer 11 is preferably made of materials such as BT resin or PP.

[0144] In this embodiment, the insulating layer 11 may have heat-conducting holes 112 uniformly arranged in the upper or lower half of the insulating layer 11; or the upper and lower half of the insulating layer 11 may be staggered and uniformly arranged with heat-conducting holes 112; the heat-conducting holes 112 are all filled with a high thermal conductivity material.

[0145] In this embodiment, the high thermal conductivity material filling the heat conduction hole 112 is preferably copper. Specifically, the heat conduction hole 112 is filled by copper plating or copper electroplating, and the thickness of copper plating is preferably 1 to 2 μm, and the thickness of copper electroplating is preferably 12 to 20 μm.

[0146] The heat-conducting holes 112 provided on the insulating layer 11 can serve as heat channels to accelerate heat transfer and speed up the heat transfer rate of the heat generated by the heating element 13. This allows the insulating layer 11 to maintain its overall insulation performance while improving the thermal conductivity of the corresponding local or specific areas of the fuse circuit 12.

[0147] In this embodiment, a fluxing insulating layer 24 is provided on the insulating layer 11. The fluxing insulating layer 24 covers the insulating layer 11, flows into the pad 17, flows out of the pad 18, and controls the pad 19.

[0148] The flux insulating layer 24 has a receiving slot 241, and the flux layer 22 and at least part of the fuse circuit 12 are disposed in the receiving slot 241.

[0149] In this embodiment, a solder resist layer 20 is provided on the flux insulating layer 24, and the solder resist layer 20 at least covers the upper surface of the flux layer 22; when the solder resist layer 20 is used to solder other components, it isolates the fuse circuit 12 and / or the flux layer 22 from the high-temperature sparks to prevent the fuse circuit 12 and / or the flux layer 22 from melting, thus avoiding the scrapping of the three-terminal fuse structure.

[0150] In this embodiment, a top cover 23 is also included, which covers the top of the flux insulation layer 24.

[0151] The top cover 23 is used to isolate the sparks generated when the fuse circuit 12 and the flux layer 22 melt, so as to prevent the combustion of other external components and devices.

[0152] The manufacturing method of the three-terminal safety structure in this embodiment includes the following steps:

[0153] Step 1: Material preparation; Provide support body 10;

[0154] The support 10 is a commonly used PCB substrate other than ceramic substrate and metal substrate;

[0155] The bottom of the substrate is provided with three separate terminals, namely, inflow terminal 14, outflow terminal 15, and control terminal 16;

[0156] Step 2: First graphic creation; Create the graphic on the upper surface of the support 10, add the heating element 13, and add heating end pads 131 at both ends of the heating element 13;

[0157] Step 3: First pressing; Press the insulating layer 11 and copper foil onto the upper surface of the support 10 and the heating element 13. The copper foil forms at least three pads, namely the inflow pad 17, the outflow pad 18 and the control pad 19.

[0158] Step 4: Drilling; Drill holes in the pressed support 10 and the insulating plate to obtain: inflow end conductive holes 141 that connect the inflow terminal 14 and the inflow pad 17; outflow end conductive holes 151 that connect the outflow terminal 15 and the outflow pad 18; and heating end conductive holes 111 that connect the control terminal 16 and the heating end pad 131, and the control pad 19 and the heating end pad 131.

[0159] Step 5: Metallization of conductive holes; specifically, copper plating and electroplating to make the conductive holes 141 at the inflow end, 151 at the outflow end, and 111 at the heating end conductive holes conductive to conduct electricity.

[0160] The inflow conductive hole 141 and the outflow conductive hole 151 are plugged.

[0161] Step Six: Second graphic creation; create the wiring on the upper and lower surfaces of the three-terminal safety structure;

[0162] Step 7: Fuse fabrication;

[0163] A layer of tin, zinc, or aluminum, or a composite alloy thereof, is added to the inflow pad 17, outflow pad 18, and control pad 19 by chemical deposition, vapor deposition, sputtering, or electroplating. This layer serves as the fuse circuit 12. (See details...) Figure 7 ;

[0164] The flux insulating layer 24 with the receiving slot 241 is pressed onto the fuse circuit 12;

[0165] Step 8: Apply flux;

[0166] Flux is applied to the receiving channel 241 to form a flux layer 22, such that at least a portion of the upper surface of the fuse circuit 12 is coated with the flux layer 22;

[0167] The upper and lower surfaces of the structure obtained through the above steps are coated with a solder resist material to obtain a solder resist layer 20.

[0168] Step 9: Attach the lid;

[0169] The top cover 23 is bonded to the upper surface of the structure obtained in the above steps;

[0170] Furthermore, individual cutting is performed; the entire large substrate is cut into the size of a single product.

[0171] Complete the fabrication of the three-terminal insurance structure, referring to the following for details. Figure 9 .

[0172] The difference between this embodiment and embodiment one is that: the flux insulating layer 24 with the receiving slot 241 is pressed onto the fuse circuit 12, and flux is applied to the receiving slot 241 to form a flux layer 22, so that at least part of the upper surface of the fuse circuit 12 is coated with flux, and solder resist material is also applied to the upper surface of the flux insulating layer 24 and the flux layer 22; so that this embodiment has the advantages of large production capacity, low cost, and cleanable product.

[0173] Example 3

[0174] Please refer to Figure 10 , Figure 11 and Figure 12A three-terminal fuse structure based on a circuit board structure includes a support body 10, a heating element 13, and a fuse circuit 12.

[0175] An insulating layer 11 is provided on the support body 10, and the heating element 13 is disposed between the support body 10 and the insulating layer 11;

[0176] The insulating layer 11 is provided with inflow pad 17, outflow pad 18 and control pad 19;

[0177] The fuse circuit 12 is located above the insulating layer 11 and is electrically connected to the inflow pad 17, the outflow pad 18, and the control pad 19 respectively. The heating element 13 is electrically connected to the inflow pad 17 and the control pad 19 to form a control circuit.

[0178] Under overcurrent conditions, fuse 12 blows;

[0179] Under overvoltage conditions, the heating element 13 heats up, and the heat generated passes through the insulation layer 11 and melts the fuse circuit 12.

[0180] In this embodiment, the support 10 is a copper frame filled with molding compound, and the copper frame is composed of three mutually separated terminals; the three mutually separated terminals are inflow terminal 14, outflow terminal 15, and control terminal 16.

[0181] The inflow terminal 14, the outflow terminal 15, and the control terminal 16 are located at the lower part of the support body 10. The inflow terminal 14 is electrically connected to the inflow pad 17 through the inflow end conductive hole 141, the outflow terminal 15 is electrically connected to the outflow pad 18 through the outflow end conductive hole 151, and the control terminal 16 is electrically connected to the control pad 19 through the heating element 13.

[0182] In the technical solution provided by this invention, a commonly used copper frame filled with molding compound is used instead of a ceramic substrate. The copper frame serves both as a connection terminal and as a support for the load-bearing components. By using a copper frame filled with molding compound, the process of filling through-holes is avoided when connecting the internal circuit pads of the three-terminal fuse structure to the copper frame. This allows the three-terminal fuse structure to be mass-produced on a large scale, reducing complex processes and lowering costs. The molding compound filling between the pads in the copper frame substrate ensures that the pads will not short-circuit. At the same time, the characteristics of the copper frame enable fast heat dissipation and improve overall thermal conductivity, allowing the heat generated by the heating element 13 during overvoltage to be quickly transferred to the fuse circuit 12, making the fuse circuit 12 more sensitive.

[0183] In this embodiment, the control terminal 16 is electrically connected to the control pad 19 through the heating element 13 as follows: both ends of the heating element 13 are provided with heating end pads 131, the control terminal 16 and the heating end pad 131 at one end of the heating element 13 are electrically connected through the heating end conductive hole 111, and the control pad 19 and the heating end pad 131 at the other end of the heating element 13 are electrically connected through the heating end conductive hole 111.

[0184] The inflow terminal 14 and the outflow terminal 15 are connected in series with the external overcurrent protection circuit. The inflow terminal 14 and the control terminal 16 are connected in series with the external overvoltage protection circuit. The external overcurrent protection circuit and the overvoltage protection circuit are connected in parallel. The overvoltage protection circuit is equipped with a MOSFET. When the voltage on the overvoltage protection circuit reaches the protection threshold, the MOSFET will cause the overvoltage protection circuit to change from an open circuit to a closed circuit.

[0185] The fuse circuit 12 is made of a thin layer of metal and forms a weak electrical connection with the external circuit. The weak electrical connection allows the current to pass through the fuse circuit 12 normally without causing the fuse circuit 12 to blow during normal circuit operation. However, when the external circuit is operating under overcurrent and / or overvoltage conditions, the fuse circuit 12 can blow quickly.

[0186] The material of the fuse circuit 12 is usually at least one of tin, lead, copper, silver, zinc, aluminum, and any combination thereof, and in this embodiment, tin is preferred.

[0187] In the overcurrent state, the current flows sequentially into terminal 14, into pad 17, fuse circuit 12, out of pad 18 and out of terminal 15; at this time, fuse circuit 12 heats up and melts itself, thereby changing the overcurrent protection circuit from a closed circuit to an open circuit.

[0188] Under overvoltage conditions, the MOSFET in the overvoltage protection circuit causes the overvoltage protection circuit to switch from an open circuit to a closed circuit. The overvoltage current flows sequentially into terminal 14, pad 17, fuse circuit 12, control pad 19, heating element 13, and control terminal 16. It should be noted that the heating element 13 is made of a resistor. When the overvoltage current passes through the heating element 13, the heating element 13 heats up. The heat generated by the heating element 13 passes through the insulating layer 11, thereby causing the fuse circuit 12 to melt and the overvoltage protection circuit to switch from a closed circuit to an open circuit.

[0189] In this embodiment, a flux layer 22 is provided on the fuse circuit 12. The longitudinal projection position of the flux layer 22 overlaps with the longitudinal projection position of the heating element 13 by 80% to 100% of its area. The longitudinal projection position of the heating element 13 is located within the longitudinal projection of the fuse circuit 12.

[0190] The flux layer 22 assists in the melting of the fuse circuit 12. The longitudinal projection positions of the flux layer 22 and the heating element 13 coincide, so that when the heat from the heating element 13 is transferred to the fuse circuit 12, the flux layer 22 can better promote the melting of the fuse circuit 12 and improve the melting sensitivity of the fuse circuit 12. The longitudinal projection positions of the flux layer 22 and the heating element 13 overlap by 80%, 90%, or 100% of their area, with 100% overlap being the most preferred. The longitudinal projection position of the heating element 13 is located within the longitudinal projection of the fuse circuit 12, so that the heat from the heating element 13 can be accurately transferred to the fuse circuit 12, thereby causing the fuse circuit 12 to melt under overvoltage conditions.

[0191] In this embodiment, the insulating layer 11 is made of at least one or more of the following materials: glass fiber, epoxy resin, phenolic resin, polyimide, polytetrafluoroethylene, and polyester film.

[0192] Specifically, the insulating layer 11 can be made of glass fiber, epoxy resin, phenolic resin, polyimide, polytetrafluoroethylene, BT resin, etc.

[0193] In this embodiment, the insulating layer 11 is preferably made of materials such as BT resin or PP.

[0194] In this embodiment, the insulating layer 11 may have heat-conducting holes 112 uniformly arranged in the upper or lower half of the insulating layer 11; or the upper and lower half of the insulating layer 11 may be staggered and uniformly arranged with heat-conducting holes 112; the heat-conducting holes 112 are all filled with a high thermal conductivity material.

[0195] In this embodiment, the high thermal conductivity material filling the heat conduction hole 112 is preferably copper. Specifically, the heat conduction hole 112 is filled by copper plating or copper electroplating, and the thickness of copper plating is preferably 1 to 2 μm, and the thickness of copper electroplating is preferably 12 to 20 μm.

[0196] The heat-conducting holes 112 provided on the insulating layer 11 can serve as heat channels to accelerate heat transfer and speed up the heat transfer rate of the heat generated by the heating element 13. This allows the insulating layer 11 to maintain its overall insulation performance while improving the thermal conductivity of the corresponding local or specific areas of the fuse circuit 12.

[0197] In this embodiment, a top cover 23 is also included, which covers the insulating layer 11. The flux layer 22, the fuse circuit 12, the inflow pad 17, the outflow pad 18, and the control pad 19 are located in the space formed by the top cover 23 and the insulating layer 11.

[0198] The top cover 23 is used to isolate the sparks generated when the fuse circuit 12 and the flux layer 22 melt, so as to prevent the combustion of other external components and devices.

[0199] The manufacturing method of the three-terminal safety structure in this embodiment includes the following steps:

[0200] Step 1: Material preparation; Provide support body 10;

[0201] The support 10 is a copper frame filled with molding compound; the copper frame serves two purposes: supporting the components it carries and providing electrical connections to internal and external circuitry via conductive pads. Specifically, the copper frame is configured with three separate terminals: an inflow terminal 14, an outflow terminal 15, and a control terminal 16.

[0202] The upper surfaces of the inflow terminal 14, the outflow terminal 15, and the control terminal 16 are filled with molding compound, and the molding compound is pressed together to form a molding layer 101. Copper foil is then embedded in the molding layer 101. See details [link to relevant documentation]. Figure 11 ;

[0203] Step 2: First pattern creation; Create a pattern on the upper surface of the molding layer 101, add a heating element 13, and add heating end pads 131 at both ends of the heating element 13;

[0204] Step 3: Pressing; Press the insulating layer 11 and copper foil onto the upper surface of the molding layer 101 and the heating element 13. The copper foil forms three pads, namely the inflow pad 17, the outflow pad 18 and the control pad 19.

[0205] Step 4: Drilling; Drill holes in the pressed support 10 and the insulating plate to obtain: inflow end conductive holes 141 that connect the inflow terminal 14 and the inflow pad 17; outflow end conductive holes 151 that connect the outflow terminal 15 and the outflow pad 18; and heating end conductive holes 111 that connect the control terminal 16 and the heating end pad 131, and the control pad 19 and the heating end pad 131.

[0206] Step 5: Metallization of conductive holes; specifically, copper plating and electroplating to make the conductive holes 141 at the inflow end, 151 at the outflow end, and 111 at the heating end conductive holes conductive to conduct electricity.

[0207] Step Six: Second graphic creation; create the wiring on the upper and lower surfaces of the three-terminal safety structure;

[0208] Solder resist material is applied to the upper and lower surfaces of the three-terminal safety structure; after surface coating, the entire large substrate is cut into individual product sizes;

[0209] Step 7: Fuse fabrication;

[0210] Solder the fuse circuit 12 on the inflow pad 17, outflow pad 18, and control pad 19;

[0211] Step 8: Apply flux;

[0212] Flux is applied directly to the fuse circuit 12 to obtain a flux layer 22 that covers at least part of the upper surface of the fuse circuit 12;

[0213] Step 9: Attach the lid;

[0214] The top cover 23 is bonded to the upper surface of the insulating layer 11;

[0215] Complete the fabrication of the three-terminal safety structure.

[0216] In existing technologies, three-terminal fuses made using ceramic substrates require up to eight printing processes, making the manufacturing process quite complex. Furthermore, the small area of ​​the ceramic substrate results in a limited number of fuses produced per batch, leading to higher costs. The technical solution provided in this application uses common PCB substrate materials, specifically copper frames and molding compounds, to fabricate the three-terminal fuse structure. During manufacturing, this substrate has a larger processable area compared to ceramic substrates, allowing for a larger output of three-terminal fuse structures per batch, resulting in higher processing efficiency and lower costs. Additionally, this three-terminal fuse structure substrate can be manufactured using common processes such as lamination and planar embedded resistors, and its thickness is less than that of ceramic substrates, reducing the overall structural thickness. The manufacturing process is also relatively simple and mature.

[0217] Example 4

[0218] Please refer to Figures 13-17 A three-terminal fuse structure based on a circuit board structure includes a support body 10, a heating element 13, and a fuse circuit 12.

[0219] An insulating layer 11 is provided on the support body 10, and the heating element 13 is disposed between the support body 10 and the insulating layer 11;

[0220] The insulating layer 11 is provided with inflow pad 17, outflow pad 18 and control pad 19;

[0221] The fuse circuit 12 is located above the insulating layer 11 and is electrically connected to the inflow pad 17, the outflow pad 18, and the control pad 19 respectively. The heating element 13 is electrically connected to the inflow pad 17 and the control pad 19 to form a control circuit.

[0222] Under overcurrent conditions, fuse 12 blows;

[0223] Under overvoltage conditions, the heating element 13 heats up, and the heat generated passes through the insulation layer 11 and melts the fuse circuit 12.

[0224] In this embodiment, the support 10 is a copper frame filled with molding compound, and the copper frame is composed of three mutually separated terminals; the three mutually separated terminals are inflow terminal 14, outflow terminal 15, and control terminal 16.

[0225] The inflow terminal 14, the outflow terminal 15, and the control terminal 16 are located at the lower part of the support body 10. The inflow terminal 14 is electrically connected to the inflow pad 17 through the inflow end conductive hole 141, the outflow terminal 15 is electrically connected to the outflow pad 18 through the outflow end conductive hole 151, and the control terminal 16 is electrically connected to the control pad 19 through the heating element 13.

[0226] In this embodiment, the control terminal 16 is electrically connected to the control pad 19 through the heating element 13 as follows: both ends of the heating element 13 are provided with heating end pads 131, the control terminal 16 and the heating end pad 131 at one end of the heating element 13 are electrically connected through the heating end conductive hole 111, and the control pad 19 and the heating end pad 131 at the other end of the heating element 13 are electrically connected through the heating end conductive hole 111.

[0227] The inflow terminal 14 and the outflow terminal 15 are connected in series with the external overcurrent protection circuit. The inflow terminal 14 and the control terminal 16 are connected in series with the external overvoltage protection circuit. The external overcurrent protection circuit and the overvoltage protection circuit are connected in parallel. The overvoltage protection circuit is equipped with a MOSFET. When the voltage on the overvoltage protection circuit reaches the protection threshold, the MOSFET will cause the overvoltage protection circuit to change from an open circuit to a closed circuit.

[0228] The fuse circuit 12 is made of a thin layer of metal and forms a weak electrical connection with the external circuit. The weak electrical connection allows the current to pass through the fuse circuit 12 normally without causing the fuse circuit 12 to blow during normal circuit operation. However, when the external circuit is operating under overcurrent and / or overvoltage conditions, the fuse circuit 12 can blow quickly.

[0229] In this embodiment, the material of the fuse circuit 12 is preferably tin;

[0230] In the overcurrent state, the current flows sequentially into terminal 14, into pad 17, fuse circuit 12, out of pad 18 and out of terminal 15; at this time, fuse circuit 12 heats up and melts itself, thereby changing the overcurrent protection circuit from a closed circuit to an open circuit.

[0231] Under overvoltage conditions, the MOSFET in the overvoltage protection circuit causes the overvoltage protection circuit to switch from an open circuit to a closed circuit. The overvoltage current flows sequentially into terminal 14, pad 17, fuse circuit 12, control pad 19, heating element 13, and control terminal 16. It should be noted that the heating element 13 is made of a resistor. When the overvoltage current passes through the heating element 13, the heating element 13 heats up. The heat generated by the heating element 13 passes through the insulating layer 11, thereby causing the fuse circuit 12 to melt and the overvoltage protection circuit to switch from a closed circuit to an open circuit.

[0232] In this embodiment, a flux layer 22 is provided on the fuse circuit 12. The longitudinal projection position of the flux layer 22 overlaps with the longitudinal projection position of the heating element 13 by 80% to 100% of its area. The longitudinal projection position of the heating element 13 is located within the longitudinal projection of the fuse circuit 12.

[0233] In this embodiment, the insulating layer 11 is preferably made of materials such as BT resin or PP.

[0234] In this embodiment, the insulating layer 11 may have heat-conducting holes 112 uniformly arranged in the upper or lower half of the insulating layer 11; or the upper and lower half of the insulating layer 11 may be staggered and uniformly arranged with heat-conducting holes 112; the heat-conducting holes 112 are all filled with a high thermal conductivity material.

[0235] In this embodiment, the high thermal conductivity material filling the heat conduction hole 112 is preferably copper. Specifically, the heat conduction hole 112 is filled by copper plating or copper electroplating, and the thickness of copper plating is preferably 1 to 2 μm, and the thickness of copper electroplating is preferably 12 to 20 μm.

[0236] The heat-conducting holes 112 provided on the insulating layer 11 can serve as heat channels to accelerate heat transfer and speed up the heat transfer rate of the heat generated by the heating element 13. This allows the insulating layer 11 to maintain its overall insulation performance while improving the thermal conductivity of the corresponding local or specific areas of the fuse circuit 12.

[0237] In this embodiment, a fluxing insulating layer 24 is provided on the insulating layer 11. The fluxing insulating layer 24 covers the insulating layer 11, flows into the pad 17, flows out of the pad 18, and controls the pad 19. The fluxing insulating layer 24 has a receiving slot 241, and the fluxing layer 22 and at least part of the fuse circuit 12 are disposed in the receiving slot 241.

[0238] A solder resist layer 20 is provided on the flux insulating layer 24, and the solder resist layer 20 at least covers the upper surface of the flux layer 22. When the solder resist layer 20 is used to solder other components, it isolates the fuse circuit 12 and / or the flux layer 22 from the high-temperature sparks to prevent the fuse circuit 12 and / or the flux layer 22 from melting and avoids the three-terminal fuse structure from being scrapped.

[0239] It also includes a top cover 23, which covers the flux insulation layer 24; the top cover 23 is used to isolate the sparks generated when the fuse circuit 12 and the flux layer 22 melt, so as to prevent the combustion of other external components and devices.

[0240] The manufacturing method of the three-terminal safety structure in this embodiment includes the following steps:

[0241] Step 1: Material preparation; Provide support body 10;

[0242] The support 10 is a copper frame filled with molding compound; the copper frame serves two purposes: supporting the components it carries and providing electrical connections to internal and external circuitry via conductive pads. Specifically, the copper frame is configured with three separate terminals: an inflow terminal 14, an outflow terminal 15, and a control terminal 16.

[0243] The upper surfaces of the inflow terminal 14, the outflow terminal 15 and the control terminal 16 are filled with molding compound, and the molding compound is pressed to form a molding layer 101, and copper foil is embedded in the molding layer 101.

[0244] Step 2: First graphic creation; Create the graphic on the upper surface of the support 10, add the heating element 13, and add heating end pads 131 at both ends of the heating element 13;

[0245] Step 3: Pressing; Press the insulating layer 11 and copper foil onto the upper surfaces of the support 10 and the heating element 13. The copper foil forms at least three pads, namely the inflow pad 17, the outflow pad 18 and the control pad 19.

[0246] Step 4: Drilling; Drill holes in the pressed support 10 and the insulating plate to obtain: inflow end conductive holes 141 that connect the inflow terminal 14 and the inflow pad 17; outflow end conductive holes 151 that connect the outflow terminal 15 and the outflow pad 18; and heating end conductive holes 111 that connect the control terminal 16 and the heating end pad 131, and the control pad 19 and the heating end pad 131.

[0247] Step 5: Metallization of conductive holes; specifically, copper plating and electroplating to make the conductive holes 141 at the inflow end, 151 at the outflow end, and 111 at the heating end conductive holes conductive to conduct electricity.

[0248] The inflow conductive hole 141 and the outflow conductive hole 151 are plugged.

[0249] Step Six: Second graphic creation; create the wiring on the upper and lower surfaces of the three-terminal safety structure;

[0250] Step 7: Fuse fabrication;

[0251] A layer of tin, zinc, or aluminum, or a composite alloy thereof, is added to the inflow pad 17, outflow pad 18, and control pad 19 by chemical deposition, vapor deposition, sputtering, or electroplating. This layer serves as the fuse circuit 12. (Refer to...) Figure 13 ;

[0252] The flux insulating layer 24 with the receiving slot 241 is then pressed onto the fuse circuit 12; refer to Figure 14 ;

[0253] Step 8: Apply flux;

[0254] Flux is applied to the receiving channel 241 to form a flux layer 22, such that at least a portion of the upper surface of the fuse circuit 12 is coated with the flux layer 22; see reference. Figure 15 ;

[0255] The upper and lower surfaces of the structure obtained through the above steps are coated with solder resist material to obtain solder resist layer 20; refer to Figure 16 ;

[0256] Step 9: Attach the lid;

[0257] The top cover 23 is bonded to the upper surface of the structure obtained in the above steps; refer to Figure 17 ;

[0258] Furthermore, individual cutting is performed; the entire large substrate is cut into the size of a single product.

[0259] Complete the fabrication of the three-terminal safety structure.

[0260] In this embodiment, commonly used PCB substrate materials, specifically copper frame and molding compound, are used to fabricate a substrate with a three-terminal fuse structure. During the fabrication process, this substrate has a larger processable area compared to a ceramic substrate. In a single batch production, the number of three-terminal fuse structures produced using commonly used PCB substrate materials is larger, resulting in higher processing efficiency and lower cost. In addition, the fuse circuit 12 in this embodiment is a layer of pure metal or composite alloy added to the inflow pad 17, outflow pad 18, and control pad 19 by chemical deposition, evaporation, sputtering, or electroplating. This allows the fuse circuit 12 to be electrically connected to the inflow pad 17, outflow pad 18, and control pad 19, thereby enabling the fuse circuit 12 to melt and provide overcurrent and overvoltage protection.

[0261] Example 5

[0262] Please refer to Figures 18-21 A three-terminal fuse structure based on a circuit board structure includes a support body 10, a heating element 13, and a fuse circuit 12.

[0263] An insulating layer 11 is provided on the support body 10, and the heating element 13 is disposed between the support body 10 and the insulating layer 11;

[0264] The insulating layer 11 is provided with inflow pad 17, outflow pad 18 and control pad 19;

[0265] The fuse circuit 12 is located above the insulating layer 11 and is electrically connected to the inflow pad 17, the outflow pad 18, and the control pad 19 respectively. The heating element 13 is electrically connected to the inflow pad 17 and the control pad 19 to form a control circuit.

[0266] Under overcurrent conditions, fuse 12 blows;

[0267] Under overvoltage conditions, the heating element 13 heats up, and the heat generated passes through the insulation layer 11 and melts the fuse circuit 12.

[0268] In this embodiment, three separate terminals are also included: an inflow terminal 14, an outflow terminal 15, and a control terminal 16. The inflow terminal 14, the outflow terminal 15, and the control terminal 16 are electrically connected to the fuse circuit 12.

[0269] Specifically, refer to Figure 18 The inflow terminal 14 is disposed on the lower surface of the inflow pad 17, and the inflow terminal 14 is electrically connected to the fuse circuit 12 through the inflow pad 17.

[0270] The outgoing terminal 15 is disposed on the lower surface of the outgoing pad 18, and the outgoing terminal 15 is electrically connected to the fuse circuit 12 through the outgoing pad 18.

[0271] The control terminal 16 is disposed on the lower surface of the insulating layer 11, and the control terminal 16 is electrically connected to the control pad 19 through the heating element 13.

[0272] In this embodiment, refer to Figure 19 The control terminal 16 is electrically connected to the control pad 19 through the heating element 13 as follows: both ends of the heating element 13 are provided with heating end pads 131. The control terminal 16 and the heating end pad 131 at one end of the heating element 13 are electrically connected through the heating end conductive hole 111. The control pad 19 and the heating end pad 131 at the other end of the heating element 13 are electrically connected through the heating end conductive hole 111.

[0273] The inflow terminal 14 and the outflow terminal 15 are connected in series with the external overcurrent protection circuit. The inflow terminal 14 and the control terminal 16 are connected in series with the external overvoltage protection circuit. The external overcurrent protection circuit and the overvoltage protection circuit are connected in parallel. The overvoltage protection circuit is equipped with a MOSFET. When the voltage on the overvoltage protection circuit reaches the protection threshold, the MOSFET will cause the overvoltage protection circuit to change from an open circuit to a closed circuit.

[0274] The fuse circuit 12 is made of a thin layer of metal and forms a weak electrical connection with the external circuit. The weak electrical connection allows the current to pass through the fuse circuit 12 normally without causing the fuse circuit 12 to blow during normal circuit operation. However, when the external circuit is operating under overcurrent and / or overvoltage conditions, the fuse circuit 12 can blow quickly.

[0275] In this embodiment, the material of the fuse circuit 12 is preferably tin;

[0276] In the overcurrent state, the current flows sequentially into terminal 14, into pad 17, fuse circuit 12, out of pad 18 and out of terminal 15; at this time, fuse circuit 12 heats up and melts itself, thereby changing the overcurrent protection circuit from a closed circuit to an open circuit.

[0277] Under overvoltage conditions, the MOSFET in the overvoltage protection circuit causes the overvoltage protection circuit to switch from an open circuit to a closed circuit. The overvoltage current flows sequentially into terminal 14, pad 17, fuse circuit 12, control pad 19, heating element 13, and control terminal 16. It should be noted that the heating element 13 is made of a resistor. When the overvoltage current passes through the heating element 13, the heating element 13 heats up. The heat generated by the heating element 13 passes through the insulating layer 11, thereby causing the fuse circuit 12 to melt and the overvoltage protection circuit to switch from a closed circuit to an open circuit.

[0278] In this embodiment, the longitudinal projection position of the heating element 13 is located within the longitudinal projection of the fuse circuit 12.

[0279] The longitudinal projection of the heating element 13 is located within the longitudinal projection of the fuse circuit 12, so that the heat of the heating element 13 can be accurately transferred to the fuse circuit 12, thereby causing the fuse circuit 12 to melt under overvoltage conditions.

[0280] In this embodiment, the support 10 can be made of glass fiber, epoxy resin, phenolic resin, polyimide, polytetrafluoroethylene, or other commonly used resin substrates and organic substrates that can be produced in large areas. Resin substrates and organic substrates have the characteristics of high output and low cost compared with ceramics, which can further reduce processing costs and improve production efficiency.

[0281] In this embodiment, the support 10 is preferably an FR-4 type substrate, specifically an FR-4 epoxy glass cloth laminate, which is made of glass fiber cloth impregnated with epoxy resin and has good mechanical strength, electrical insulation properties and high temperature resistance.

[0282] In this embodiment, a protective layer 21 is provided on the side of the support 10 away from the insulating layer 11. The protective layer 21 is used to protect the support 10. Specifically, the protective layer 21 can be made of solder resist ink.

[0283] The protective layer 21 can protect the support 10 from external environmental erosion, such as oxidation and corrosion, to a certain extent, thus extending the service life of the support 10.

[0284] In this embodiment, the insulating layer 11 is preferably made of materials such as BT resin or PP.

[0285] In this embodiment, the insulating layer 11 may have heat-conducting holes 112 uniformly arranged in the upper or lower half of the insulating layer 11; or the upper and lower half of the insulating layer 11 may be staggered and uniformly arranged with heat-conducting holes 112; the heat-conducting holes 112 are all filled with a high thermal conductivity material.

[0286] In this embodiment, the high thermal conductivity material filling the heat conduction hole 112 is preferably copper. Specifically, the heat conduction hole 112 is filled by copper plating or copper electroplating, and the thickness of copper plating is preferably 1 to 2 μm, and the thickness of copper electroplating is preferably 12 to 20 μm.

[0287] The heat-conducting holes 112 provided on the insulating layer 11 can serve as heat channels to accelerate heat transfer and speed up the heat transfer rate of the heat generated by the heating element 13. This allows the insulating layer 11 to maintain its overall insulation performance while improving the thermal conductivity of the corresponding local or specific areas of the fuse circuit 12.

[0288] The manufacturing method of the three-terminal safety structure in this embodiment includes the following steps:

[0289] Step 1: Material preparation; wherein, a commonly used PCB substrate other than ceramic substrate and metal substrate is used as the support 10, and the support 10 is preferably an organic substrate and a resin substrate.

[0290] Step 2: First graphic creation; Create a graphic on the upper surface of the support 10, add the heating element 13, and add heating end pads 131 at both ends of the heating element 13;

[0291] Step 3: First pressing; Press the insulating layer 11 and copper foil onto the upper surface of the support 10 and the heating element 13. The copper foil forms three pads and one connection terminal. The three pads are the inflow pad 17, the outflow pad 18 and the control pad 19. The connection terminal is the control terminal 16.

[0292] Step 4: Drilling; Drill holes at the positions of the heating end pads 131 at both ends of the insulating layer 11 corresponding to the heating element 13 to form heating end conductive holes 111. The control terminal 16 is connected to the heating end pad 131 at one end of the heating element 13 through the heating end conductive holes 111, and the control pad 19 is connected to the heating end pad 131 at the other end of the heating element 13 through the heating end conductive holes 111.

[0293] Step 5: First copper plating and electroplating; to make the conductive hole 111 at the heating end conductive end conductive;

[0294] Step Six: Second graphic creation; create the wiring on the upper and lower surfaces of the three-terminal safety structure;

[0295] Step 7: Fuse fabrication; Electroplating tin onto the three pads to obtain a tin plating layer as fuse circuit 12;

[0296] Step 8: Solder resist fabrication; A layer of solder resist material is uniformly coated on the surface of the fuse circuit 12 to obtain solder resist layer 20;

[0297] Step 9: Second electroplating; The control terminal 16 is electroplated to thicken it, and the inflow pad 17 and outflow pad 18 are electroplated to form the inflow terminal 14 and the outflow terminal 15.

[0298] Step 10: Surface coating; Apply solder resist material to the lower surface of the support 10 as a protective layer 21;

[0299] Step 11: Cut individual pieces; cut the entire large substrate into the size of individual products to complete the three-end safety structure.

[0300] In the overall structure of this embodiment, the bottom of the insulating layer 11 is provided with an inflow terminal 14, an outflow terminal 15, and a control terminal 16, and the inflow terminal 14, the outflow terminal 15, and the control terminal 16 are connected through a fuse circuit 12. When the circuit is overcurrent or overvoltage, the fuse circuit 12 melts. Since the fuse circuit 12 is located on the side where the inflow terminal 14, the outflow terminal 15, and the control terminal 16 are connected to the circuit, the sparks generated when the fuse melts will not scatter or splash to other devices, thus avoiding damage to other devices or fire, and improving safety performance. Furthermore, such a structure does not require a cover, thereby reducing the space occupied, making the overall structure more compact, and also reducing costs.

[0301] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Under the concept of the present invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the present invention as described above. For the sake of brevity, they are not provided in detail. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A three-terminal fuse structure based on a circuit board structure, characterized by It includes a support (10), a heating element (13), and a fuse circuit (12); An insulating layer (11) is provided on the support (10), and the heating element (13) is disposed between the support (10) and the insulating layer (11); The insulating layer (11) is provided with inflow pads (17), outflow pads (18) and control pads (19); The fuse circuit (12) is located above the insulating layer (11) and is electrically connected to the inflow pad (17), the outflow pad (18), and the control pad (19) respectively. The heating element (13) is electrically connected to the inflow pad (17) and the control pad (19) to form a control circuit. Under overcurrent conditions, the fuse circuit (12) blows; Under overvoltage conditions, the heating element (13) heats up, and the heat generated passes through the insulating layer (11) and melts the fuse circuit (12); The material of the support (10) includes at least one of glass fiber material, epoxy resin material, phenolic resin material, polyimide material, polytetrafluoroethylene material, and BT resin material; the material of the insulating layer (11) includes at least one of glass fiber material, epoxy resin material, phenolic resin material, polyimide material, polytetrafluoroethylene material, and BT resin material. The fuse circuit (12) is made of a thin layer of metal and forms a weak electrical connection with the external circuit; The insulating layer (11) has heat-conducting holes (112) uniformly arranged in the upper or lower half of the layer; Alternatively, the insulating layer (11) is staggered in the upper and lower halves and uniformly provided with heat-conducting holes (112); The heat-conducting holes (112) are all filled with a material with high thermal conductivity.

2. The circuit board based three-terminal fuse structure of claim 1, wherein It also includes three separate terminals: an inflow terminal (14), an outflow terminal (15), and a control terminal (16), which are electrically connected to the fuse circuit (12).

3. The circuit board based three-terminal crowbar structure of claim 2, wherein, The inflow terminal (14) is disposed on the lower surface of the inflow pad (17), and the inflow terminal (14) is electrically connected to the fuse circuit (12) through the inflow pad (17); The outgoing terminal (15) is disposed on the lower surface of the outgoing pad (18), and the outgoing terminal (15) is electrically connected to the fuse circuit (12) through the outgoing pad (18); The control terminal (16) is disposed on the lower surface of the insulating layer (11), and the control terminal (16) is electrically connected to the control pad (19) through the heating element (13).

4. The circuit board based three-terminal fuse structure of claim 2, wherein, The inflow terminal (14), the outflow terminal (15), and the control terminal (16) are disposed on the lower surface of the support body (10). The inflow terminal (14) is electrically connected to the inflow pad (17) through the inflow end conductive hole (141). The outflow terminal (15) is electrically connected to the outflow pad (18) through the outflow end conductive hole (151). The control terminal (16) is electrically connected to the control pad (19) through the heating element (13).

5. The circuit board structure-based three-terminal fuse structure according to claim 3 or 4, wherein The control terminal (16) is electrically connected to the control pad (19) through the heating element (13) as follows: both ends of the heating element (13) are provided with heating pads (131), the control terminal (16) and the heating pad (131) at one end of the heating element (13) are electrically connected through the heating conductive hole (111), and the control pad (19) and the heating pad (131) at the other end of the heating element (13) are electrically connected through the heating conductive hole (111).

6. The circuit board based three-terminal crowbar structure of claim 1, wherein, The fuse circuit (12) is provided with a flux layer (22), the longitudinal projection position of the flux layer (22) coincides with the longitudinal projection position of the heating element (13) by 80% to 100% of the area, and the longitudinal projection position of the heating element (13) is located within the longitudinal projection of the fuse circuit (12).

7. The circuit board based three-terminal crowbar structure of claim 6, wherein, It also includes a top cover (23) that covers the insulating layer (11), and the flux layer (22) and the fuse circuit (12) are located in the space formed by the top cover (23) and the insulating layer (11).

8. A manufacturing method of a three-terminal fuse structure based on a circuit board structure, characterized by, At least the following steps are included: Step 1: Material preparation; Provide support structure (10); The support (10) is a substrate with three mutually separated terminals at the bottom. The material of the support (10) includes at least one of the following: glass fiber material, epoxy resin material, phenolic resin material, polyimide material, polytetrafluoroethylene material, and BT resin material. Alternatively, the support (10) is a copper frame filled with molding compound, the copper frame being composed of three mutually separate terminals; The three separate terminals are the inflow terminal (14), the outflow terminal (15), and the control terminal (16); Step 2: First pattern making; make a pattern on the upper surface of the support (10), add a heating element (13), and add heating end pads (131) at both ends of the heating element (13); Step 3: Pressing; Press an insulating layer (11) and copper foil onto the upper surfaces of the support (10) and the heating element (13), wherein the copper foil forms at least three pads; The three pads are the inflow pad (17), the outflow pad (18), and the control pad (19); The insulating layer (11) is made of at least one of the following materials: glass fiber material, epoxy resin material, phenolic resin material, polyimide material, polytetrafluoroethylene material, and BT resin material; Among them, the fuse circuit (12) is made of a thin layer of metal and forms a weak electrical connection with the external circuit; The insulating layer (11) has heat-conducting holes (112) uniformly arranged in the upper or lower half of the layer; Alternatively, the insulating layer (11) is staggered in the upper and lower halves and uniformly provided with heat-conducting holes (112); The heat-conducting holes (112) are all filled with a material with high thermal conductivity; Step 4: Drilling; Drill holes in the pressed support (10) and the insulating layer to obtain: an inflow end conductive hole (141) connecting the inflow terminal (14) and the inflow pad (17); an outflow end conductive hole (151) connecting the outflow terminal (15) and the outflow pad (18); and a heating end conductive hole (111) connecting the control terminal (16) and the heating end pad (131), and the control pad (19) and the heating end pad (131). Step 5: Metallization of conductive holes; to obtain conductive inflow end conductive hole (141), outflow end conductive hole (151), and heating end conductive hole (111); Step Six: Second graphic creation; create the wiring on the upper and lower surfaces of the three-terminal safety structure; Step 7: Fuse fabrication; A fuse circuit (12) is soldered onto the inflow pad (17), the outflow pad (18), and the control pad (19); Alternatively, a layer of pure metal or alloy may be added to the inflow pad (17), the outflow pad (18), and the control pad (19), which serves as a fuse circuit (12); Step 8: Apply flux; After slotting the insulating film to obtain the receiving groove (241), it is then pressed onto the insulating layer (11), the fuse circuit (12), the inflow pad (17), the outflow pad (18), and the control pad (19) to form a flux insulating layer (24). Flux is applied into the receiving groove (241) to obtain a flux layer (22) that at least partially covers the upper surface of the fuse circuit (12). Solder resist material is applied to the upper surface of the flux insulating layer (24) to obtain a solder resist layer (20). Alternatively, flux can be applied directly to the fuse circuit (12) to obtain a flux layer (22) that covers at least part of the upper surface of the fuse circuit (12); Step 9: Adhere the cap; Adhere the top cap (23) to the upper surface of the flux insulation layer (24); Alternatively, a top cover (23) may be bonded to the upper surface of the insulating layer (11).

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