Three-terminal circuit protection unit

Abstract

The utility model relates to the technical field of circuit protection, and discloses a three-terminal circuit protection unit, which is characterized by comprising a support body, the support body is provided with a plastic package layer, an inflow terminal, an outflow terminal and a control terminal, and the inflow terminal, the outflow terminal and the control terminal are arranged at the lower part of the support body. The plastic packaging layer is filled between every two adjacent ends of the inflow end, the outflow end and the control end and at the upper part of the inflow end, the outflow end and the control end; a heating body and a first insulating layer are arranged at the upper part of the supporting body, and the first insulating layer is arranged at the upper part of the heating body; a safety circuit is arranged on the first insulating layer and is electrically connected with the inflow end, the outflow end and the control end respectively; in an overcurrent state, the safety circuit is fused; in an overvoltage state, the heating body is electrically connected with the inflow end and the control end to form a control circuit, the heating body emits heat, and heat penetrates through the first insulating layer to fuse the safety circuit; the problems that a three-terminal fuse is large in thickness and high in manufacturing cost are solved.

Description

Technical Field

[0001] The utility model relates to the field of circuit protection, in particular to a three-terminal circuit protection unit. Background Art

[0002] Circuit protection is to prevent electronic equipment from being damaged by abnormal voltage or current surges. It cuts off the circuit or suppresses sudden changes in current and voltage by automatically triggering the fusing, resistance mutation or other physical changes of relevant functional parts. 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, particularly in consumer electronics such as mobile phones and laptops, as well as in automotive and communications equipment, to ensure stable and safe operation. Three-terminal fuses are an important electronic device protection device, primarily used to prevent damage to electronic equipment caused by current overloads, short circuits, and overvoltage. Their core principle is to utilize the properties of conductive materials to automatically disconnect the circuit when the current or voltage exceeds a set value, thereby minimizing damage to electronic equipment. The operating principles of three-terminal fuses include thermal protection, electromagnetic protection, and overcurrent and overvoltage protection. These mechanisms ensure a rapid response to circuit anomalies, cutting off the current and thus providing protection.

[0004] In existing technologies, the carrier substrate of a three-terminal fuse is typically a ceramic substrate, on which both the electrodes and the fuse metal are disposed. This presents at least the following technical issues: Due to the characteristics of the ceramic substrate, the overall thickness of the three-terminal fuse increases; and the manufacturing process involves numerous steps, resulting in low production efficiency and high costs. Utility Model Content

[0005] The main purpose of the utility model is to provide a three-terminal circuit protection unit, aiming to solve the problem that the three-terminal fuse is relatively thick and has a high manufacturing cost.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a three-terminal circuit protection unit, characterized in that it includes a support body, the support body is provided with a plastic sealing layer, an inlet end, an outlet end, and a control end, the inlet end, the outlet end, and the control end are arranged at the lower part of the support body, and the plastic sealing layer is filled between and above each adjacent end of the inlet end, the outlet end, and the control end;

[0007] A heating element and a first insulating layer are provided on the upper portion of the support body, wherein the first insulating layer is provided on the upper portion of the heating element;

[0008] A safety circuit is provided on the first insulating layer, and the safety circuit is electrically connected to the inflow end, the outflow end and the control end respectively;

[0009] In the overcurrent state, the fuse circuit is blown;

[0010] Under the overvoltage state, the heating element is electrically connected to the inflow end and the control end to form a control circuit. The heating element generates heat, and the heat passes through the first insulating layer to melt the fuse circuit.

[0011] Optionally, an inlet end pad, an outlet end pad and a control end pad are provided on the first insulating layer, and the inlet end pad, the outlet end pad and the control end pad are electrically connected to the insurance circuit respectively;

[0012] The inflow end is electrically connected to the inflow end pad through the inflow end conductive hole, the outflow end is electrically connected to the outflow end pad through the outflow end conductive hole, and the control end is electrically connected to the control end pad through the heating element.

[0013] Optionally, the control end is electrically connected to the control end pad through the heating element: a heating element inlet end pad and a heating element outlet end pad are respectively provided at both ends of the heating element, the control end pad and the heating element outlet end pad are electrically connected through the heating element outlet end conductive hole, and the inlet end pad and the heating element inlet end pad are electrically connected through the heating element inlet end conductive hole.

[0014] Optionally, a fluxing layer is provided on the safety circuit, the longitudinal projection position of the fluxing layer overlaps with the longitudinal projection position of the heating element by 80% to 100% of its area, and the longitudinal projection position of the heating element is located within the longitudinal projection of the safety circuit.

[0015] Optionally, a top cover is further included, which covers the first insulating layer, and the inlet end pad, outlet end pad, control end pad, insurance circuit and fluxing layer are located in the space formed by the top cover and the first insulating layer.

[0016] Optionally, a second insulating layer is provided on the first insulating layer, the second insulating layer is provided with a receiving groove, and the fluxing layer is provided in the receiving groove.

[0017] Optionally, a solder resist layer is provided on the second insulating layer, and a top cover is provided on the solder resist layer.

[0018] Optionally, the materials of the inflow end, the outflow end and the control end respectively include at least one or more of copper, copper-iron-phosphorus alloy, copper-nickel-silicon alloy, copper-chromium-zirconium alloy, copper-silver alloy and copper-tin alloy.

[0019] Optionally, the material of the first insulating layer includes at least one or more of glass fiber material, epoxy resin material, phenolic resin material, polyimide material, polytetrafluoroethylene material, and BT resin material.

[0020] Optionally, the material of the support body includes at least one or more of glass fiber material, epoxy resin material, phenolic resin material, polyimide material, polytetrafluoroethylene material, and BT resin material.

[0021] Beneficial effects: In the technical solution provided by the present invention, a copper frame commonly used in printed circuit boards is used to fill plastic packaging material to replace the ceramic substrate. The copper frame has the function of connecting terminals and supporting load-bearing components. The copper frame is filled with plastic packaging material, so that when the internal circuit pads of the three-terminal fuse are connected to the copper frame, the process flow of through-hole plugging is avoided, so that the three-terminal circuit protection unit can be mass-produced on a large scale, reducing complex processes and reducing costs; the pads in the substrate made of the copper frame are filled with plastic packaging material to ensure that the pads will not short-circuit. At the same time, the characteristics of the copper frame make the heat dissipation fast and the overall thermal conductivity is also improved, so that the heat generated by the heating element during overvoltage can be quickly transferred to the fuse circuit, making the fuse work more sensitive; the heating element, the fuse circuit, and the flux layer can be embedded in the first insulating layer and the second insulating layer, so that the overall thickness of the components and the device is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] One or more embodiments are exemplarily illustrated by corresponding drawings, which do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0023] Figure 1 This is a schematic cross-sectional view of an embodiment of a three-terminal circuit protection unit of the present invention;

[0024] Figure 2 This is a schematic cross-sectional structural diagram of a support body of an embodiment of a three-terminal circuit protection unit of the present invention;

[0025] Figure 3 This is a schematic cross-sectional structural diagram of a support body with a heating body added to an embodiment of a three-terminal circuit protection unit of the present invention;

[0026] Figure 4 This is a schematic cross-sectional view of a support body of an embodiment of a three-terminal circuit protection unit of the present invention with a first insulating layer added thereto;

[0027] Figure 5 This is a schematic cross-sectional view of a support body of an embodiment of a three-terminal circuit protection unit of the present invention after adding pads and drilling holes;

[0028] Figure 6 This is a schematic cross-sectional structural diagram of a support body of an embodiment of a three-terminal circuit protection unit of the present invention with a fuse circuit and a flux layer added;

[0029] Figure 7 This is a schematic cross-sectional structural diagram of a support body of another embodiment of a three-terminal circuit protection unit of the present invention with a fuse circuit added;

[0030] Figure 8 This is a schematic cross-sectional view of a support body of another embodiment of a three-terminal circuit protection unit of the present invention with a second insulating layer added;

[0031] Figure 9 This is a schematic cross-sectional view of a support body of another embodiment of a three-terminal circuit protection unit of the present invention with a fluxing layer added thereto;

[0032] Figure 10 This is a schematic cross-sectional view of a support body of another embodiment of a three-terminal circuit protection unit of the present invention with a solder resist layer added thereto;

[0033] Figure 11 This is a schematic cross-sectional view of another embodiment of a three-terminal circuit protection unit of the present invention.

[0034] In the figure: 1. Support body; 11. Inflow end; 12. Outflow end; 13. Control end; 14. Plastic sealing layer; 2. First insulating layer; 3. Heating element; 31. Heating element inflow end pad; 32. Heating element outflow end pad; 4. Fuse circuit; 5. Flux layer; 6. Second insulating layer; 61. Accommodating groove; 7. Top cover; 8. Solder mask layer; 01. Inflow end conductive hole; 02. Outflow end conductive hole; 03. Heating element inflow end conductive hole; 04. Heating element outflow end conductive hole; 05. Inflow end pad; 06. Outflow end pad; 07. Control end pad. DETAILED DESCRIPTION

[0035] To facilitate understanding of the present invention, the present invention is described in more detail 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 attached to the other element, or one or more elements can be interposed therebetween. When an element is described as being "connected to" another element, it can be directly connected to the other element, or one or more elements can be interposed therebetween. 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 solely for descriptive purposes and are not to be construed as indicating relative importance or implicitly specifying the number of technical features indicated. Therefore, unless otherwise specified, features specified as "first" or "second" may explicitly or implicitly include one or more of such features; "plurality" means two or more. The term "comprising" and any variations thereof are intended to be non-exclusive, and one or more other features, integers, steps, operations, units, components, and / or combinations thereof may be present or added.

[0036] In addition, unless otherwise expressly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, an indirect connection through an intermediate medium, or internal communication between two components. All technical and scientific terms used in this specification have the same meaning as those commonly understood by technicians in the technical field of this utility model. The terms used in the specification of this utility model are only for the purpose of describing specific embodiments and are not used to limit the utility model. The term "and / or" used in this specification includes any and all combinations of one or more related listed items.

[0037] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] Example 1

[0039] Please refer to Figures 1-6 , Figure 1 Schematic diagram of the cross-sectional structure of an embodiment of a three-terminal circuit protection unit of the present invention. Specifically: The present invention provides a three-terminal circuit protection unit, characterized in that it includes a support body 1, the support body 1 is provided with a plastic sealing layer 14, an inlet end 11, an outflow end 12 and a control end 13, the inlet end 11, the outflow end 12 and the control end 13 are arranged at the lower part of the support body 1, and the plastic sealing layer 14 is filled between and above each adjacent end of the inlet end 11, the outflow end 12 and the control end 13;

[0040] A heating element 3 and a first insulating layer 2 are provided on the upper portion of the support body 1 , wherein the first insulating layer 2 is provided on the upper portion of the heating element 3 ;

[0041] A safety circuit 4 is provided on the first insulating layer 2, and the safety circuit 4 is electrically connected to the inflow end 11, the outflow end 12 and the control end 13 respectively;

[0042] In the overcurrent state, the fuse circuit 4 is blown;

[0043] In the overvoltage state, the heating element 3 is electrically connected to the inflow end 11 and the control end 13 to form a control circuit. The heating element 3 generates heat, and the heat passes through the first insulating layer 2 to melt the fuse circuit 4.

[0044] In the technical solution provided by the present invention, a commonly used copper frame filled with plastic sealing compound is used to replace the ceramic substrate. The copper frame has both the function of connecting terminals and the function of supporting the load-bearing components. The copper frame is filled with plastic sealing compound, so that when the internal circuit pads of the three-terminal fuse are connected to the copper frame, the process flow of through-hole plugging processing is avoided, so that the three-terminal circuit protection unit can be mass-produced over a large area, reducing complex processes and lowering costs; the plastic sealing compound is filled between the pads in the substrate made of the copper frame, ensuring that the pads will not be short-circuited. At the same time, the characteristics of the copper frame make the heat dissipation fast and the overall thermal conductivity is also improved, so that the heat generated by the heating element 3 during overvoltage can be quickly transferred to the fuse circuit 4, making the fuse work more sensitive.

[0045] In this embodiment, the first insulating layer 2 is provided with an inlet end pad 05, an outlet end pad 06 and a control end pad 07, and the inlet end pad 05, the outlet end pad 06 and the control end pad 07 are electrically connected to the insurance circuit 4 respectively;

[0046] The inflow end 11 is electrically connected to the inflow end pad 05 through the inflow end conductive hole 01 , the outflow end 12 is electrically connected to the outflow end pad 06 through the outflow end conductive hole 02 , and the control end 13 is electrically connected to the control end pad 07 through the heating element 3 .

[0047] In this embodiment, the control end 13 is electrically connected to the control end pad 07 through the heating element 3 as follows: a heating element inlet end pad 31 and a heating element outlet end pad 32 are respectively provided at both ends of the heating element 3, the control end pad 07 and the heating element outlet end pad 32 are electrically connected through the conductive hole 02 at the outlet end of the heating element 3, and the inlet end pad 05 and the heating element inlet end pad 31 are electrically connected through the conductive hole 01 at the inlet end of the heating element 3.

[0048] The inflow end 11 and the outflow end are connected in series with an external overcurrent protection circuit, and the inflow end 11 and the control end 13 are connected in series with an external overvoltage protection circuit. The external overcurrent protection circuit and the overvoltage protection circuit are connected in parallel. A field effect transistor (MOSFET) is provided on the overvoltage protection circuit. When the voltage on the overvoltage protection circuit reaches the protection threshold, the MOSFET will turn the overvoltage protection circuit from open circuit to open circuit.

[0049] The fuse circuit 4 is made of thin metal and forms a weak electrical connection with the external circuit. This weak electrical connection allows the external circuit to pass through the fuse circuit 4 without causing the fuse circuit 4 to fuse during normal operation. When the external circuit operates under overcurrent and / or overvoltage conditions, the fuse circuit 4 can fuse quickly. The material of the fuse circuit 4 is generally at least one of tin, lead, copper, silver, zinc, aluminum, and alloys of any combination thereof. In this embodiment, tin is preferably used.

[0050] In the overcurrent state, the current flows into the inflow terminal 11, the inflow terminal pad 05, the fuse circuit 4, the outflow terminal pad 06 and the outflow terminal 12 in sequence. The fuse circuit 4 heats up and melts, thereby turning the overcurrent protection circuit from a path to an open circuit.

[0051] In the overvoltage state, the MOSFET in the overvoltage protection circuit causes the overvoltage protection circuit to be converted from an open circuit to a closed circuit. The overvoltage current sequentially enters the inflow terminal 11, the inflow terminal pad 05, the fuse circuit 4, the control terminal pad 07, the heating element inflow terminal pad 31, the heating element 3, the heating element outflow terminal pad 32 and the control terminal 13. The heating element 3 is made of a resistor. When the overvoltage current passes through the heating element 3, the heating element 3 heats up. The heat of the heating element 3 passes through the first insulating layer 2, thereby causing the fuse circuit 4 to melt, causing the overvoltage protection circuit to be converted from a closed circuit to an open circuit.

[0052] In this embodiment, a flux layer 5 is provided on the fuse circuit 4 , and the longitudinal projection position of the flux layer 5 overlaps with the longitudinal projection position of the heating element 3 by 80% to 100% of the area, and the longitudinal projection position of the heating element 3 is located within the longitudinal projection of the fuse circuit 4 .

[0053] The fluxing layer 5 is used to assist the fuse circuit 4 in melting. The longitudinal projection position of the fluxing layer 5 and the heating element 3 coincide with each other, so that when the heat of the heating element 3 is transferred to the fuse circuit 4, the fluxing layer 5 can better promote the melting of the fuse circuit 4 and improve the melting sensitivity of the fuse circuit 4; the longitudinal projection position of the fluxing layer 5 and the heating element 3 coincides with 80% of the area, or 90% of the area, or 100% of the area, and 100% of the overlapping area is the most preferred; the longitudinal projection position of the heating element 3 is located within the longitudinal projection of the fuse circuit 4, so that the heat of the heating element 3 can be accurately transferred to the fuse circuit 4, thereby causing the fuse circuit 4 to melt under overvoltage conditions.

[0054] In this embodiment, a top cover 7 is further included, which covers the first insulating layer 2. The inlet end pad 05, the outlet end pad 06, the control end pad 07, the insurance circuit 4 and the fluxing layer 5 are located in the space formed by the top cover 7 and the first insulating layer 2.

[0055] The top cover 7 is used to isolate the sparks generated when the fusible layer and the fluxing layer 5 are melted, so as to avoid burning other external components and devices.

[0056] In this embodiment, the material of the first insulating layer 2 includes at least one or more of a glass fiber material, an epoxy resin material, a phenolic resin material, a polyimide material, a polytetrafluoroethylene material, and a BT resin material. Specifically, the material of the first insulating layer 2 can be a glass fiber material, an epoxy resin material, a phenolic resin material, a polyimide material, a polytetrafluoroethylene material, a BT resin material, or a mixture of one or more of the following polyester film materials. In this embodiment, the first insulating layer 2 is preferably made of a material such as BT resin or PP, which has good heat resistance and / or thermal conductivity.

[0057] In this embodiment, the material of the safety circuit 4 is generally at least one of tin alloy, lead-tin alloy, copper alloy, silver alloy, and zinc alloy. In this embodiment, tin and tin-copper alloy are preferred.

[0058] In this embodiment, the steps of manufacturing a three-terminal circuit protection unit are:

[0059] Step 1: Cutting the material. The substrate is a copper frame, but can also be any other commonly used conductive metal lead frame. The substrate supports the components and serves as a conductive pad for electrical connection to internal and external circuits. Specifically, the copper frame is configured with three separate terminals: an inlet port 11, an outlet port 12, and a control port 13.

[0060] Step 2: First pressing; filling the three terminals (inflow end 11, outflow end 12 and control end 13) and the upper surface of the copper frame with plastic compound, pressing the plastic compound to form a plastic layer 14, and burying the copper foil on the plastic layer 14;

[0061] Step 3: First pattern making; Pattern making is performed on the upper surface of the plastic layer 14 to add the heating element 3 and the pads at both ends of the heating element 3 (the heating element inlet end pad 31 and the heating element outlet end pad 32);

[0062] Step 4: Second lamination; Laminating the first insulating layer 2 and the copper foil on the upper surface of the heating element 3 and the plastic sealing layer 14, and forming the inflow end pad 05, the outflow end pad 06 and the control end pad 07 on the copper foil;

[0063] Step 5: Drilling; drilling holes at the positions of the three pads (inflow end pad 05, outflow end pad 06 and control end pad 07) formed on the copper foil to form an inflow end conductive hole 01, an outflow end conductive hole 02, and a control end conductive hole 13, so that the inflow end pad 05 is connected to the inflow end 11 through the inflow end conductive hole 01, the outflow end pad 06 is connected to the outflow end 12 through the outflow end conductive hole 02, the control end pad 07 is connected to the heating element inflow end pad 31 of the heating element through the inflow end conductive hole 01 of the heating element 3, and the heating element outflow end pad 32 of the heating element 3 is connected to the outflow end 12 through the outflow end conductive hole 02 of the heating element 3;

[0064] Step 6: Copper deposition and electroplating; make the blind holes and blind holes conductive; conduct electricity in the inlet conductive hole 01, the outlet conductive hole 02, the control end conductive hole 13, the heating element 3 inlet conductive hole 01 and the heating element 3 outlet conductive hole 02;

[0065] Step 7: Second pattern making: making the lines on the upper and lower surfaces of the three-terminal circuit protection unit;

[0066] Step 8: Solder mask and surface coating: Apply solder mask material on the upper and lower surfaces of the three-terminal circuit protection unit;

[0067] Step 9: Cutting single grains; cutting the entire large substrate into the size of a single product;

[0068] Step 10: Fuse welding; weld the fuse circuit on a single product;

[0069] Step 11: Apply flux; apply flux layer 5 on the upper surface of the fuse circuit;

[0070] Step 12: Bonding the cover; bonding the top cover 7 to the upper surface of the three-terminal circuit protection unit to complete the production of the three-terminal circuit protection unit.

[0071] In the prior art, three-terminal fuses made from ceramic substrates require only eight layers of printing steps, such as drilling, plugging, and electroplating, resulting in a relatively complex manufacturing process. Furthermore, the base material area of ​​ceramic substrates is small, and during batch production, the number of fuses produced in a single batch is small, resulting in high costs. The technical solution provided in this application utilizes commonly used PCB substrate materials (copper frames and plastic encapsulation materials) as the substrate for the three-terminal fuses. During production, the substrate has a larger processable area than a ceramic substrate. During single batch production, a larger number of three-terminal fuses produced using commonly used PCB substrate materials can be produced, resulting in higher processing efficiency and lower costs. Furthermore, the three-terminal fuses using commonly used PCB substrate materials can be manufactured using commonly used processes such as lamination and planar embedded resistors. The substrate thickness is also lower than that of ceramic substrates, reducing the overall product thickness and making the manufacturing process relatively simple and mature.

[0072] Example 2

[0073] Please refer to Figure 2-Figure 5 and Figure 7-11 , Figure 11 : This is a schematic cross-sectional view of another embodiment of a three-terminal circuit protection unit of the present invention. Specifically: The present invention provides a three-terminal circuit protection unit, characterized in that it includes a support body 1, the support body 1 is provided with a plastic sealing layer 14, an inlet end 11, an outflow end 12 and a control end 13, the inlet end 11, the outflow end 12 and the control end 13 are arranged at the lower part of the support body 1, and the plastic sealing layer 14 is filled between and above each adjacent end of the inlet end 11, the outflow end 12 and the control end 13;

[0074] A heating element 3 and a first insulating layer 2 are provided on the upper portion of the support body 1 , wherein the first insulating layer 2 is provided on the upper portion of the heating element 3 ;

[0075] A safety circuit 4 is provided on the first insulating layer 2, and the safety circuit 4 is electrically connected to the inflow end 11, the outflow end 12 and the control end 13 respectively;

[0076] In the overcurrent state, the fuse circuit 4 is blown;

[0077] In the overvoltage state, the heating element 3 is electrically connected to the inflow end 11 and the control end 13 to form a control circuit. The heating element 3 generates heat, and the heat passes through the first insulating layer 2 to melt the fuse circuit 4.

[0078] In the technical solution provided by the present invention, a commonly used copper frame filled with plastic sealing compound is used to replace the ceramic substrate. The copper frame has the function of connecting terminals and supporting the load-bearing components. The copper frame is filled with plastic sealing compound, so that when the internal circuit pads of the three-terminal fuse are connected to the copper frame, the process flow of through-hole plugging is avoided, so that the three-terminal circuit protection unit can be mass-produced over a large area, reducing complex processes and lowering costs; the plastic sealing compound is filled between the pads in the substrate made of the copper frame, ensuring that the pads will not short-circuit. At the same time, the characteristics of the copper frame also improve the overall thermal conductivity, so that the heat generated by the heating element 3 during overvoltage can be quickly transferred to the fuse circuit 4, making the fuse work more sensitive.

[0079] In this embodiment, the first insulating layer 2 is provided with an inlet end pad 05, an outlet end pad 06 and a control end pad 07, and the inlet end pad 05, the outlet end pad 06 and the control end pad 07 are electrically connected to the insurance circuit 4 respectively;

[0080] The inflow end 11 is electrically connected to the inflow end pad 05 through the inflow end conductive hole 01 , the outflow end 12 is electrically connected to the outflow end pad 06 through the outflow end conductive hole 02 , and the control end 13 is electrically connected to the control end pad 07 through the heating element 3 .

[0081] In this embodiment, the control end 13 is electrically connected to the control end pad 07 through the heating element 3 as follows: a heating element inlet end pad 31 and a heating element outlet end pad 32 are respectively provided at both ends of the heating element 3, the control end pad 07 and the heating element outlet end pad 32 are electrically connected through the conductive hole 02 at the outlet end of the heating element 3, and the inlet end pad 05 and the heating element inlet end pad 31 are electrically connected through the conductive hole 01 at the inlet end of the heating element 3.

[0082] The inflow end 11 and the outflow end are connected in series with an external overcurrent protection circuit, and the inflow end 11 and the control end 13 are connected in series with an external overvoltage protection circuit. The external overcurrent protection circuit and the overvoltage protection circuit are connected in parallel. A field effect transistor (MOSFET) is provided on the overvoltage protection circuit. When the voltage on the overvoltage protection circuit reaches the protection threshold, the MOSFET will turn the overvoltage protection circuit from open circuit to open circuit.

[0083] The fuse circuit 4 is made of thin metal and forms a weak electrical connection with the external circuit. This weak electrical connection allows the external circuit to pass through the fuse circuit 4 without causing the fuse circuit 4 to fuse during normal operation. When the external circuit operates under overcurrent and / or overvoltage conditions, the fuse circuit 4 can fuse quickly. The material of the fuse circuit 4 is generally at least one of tin, lead, copper, silver, zinc, aluminum, and alloys of any combination thereof. In this embodiment, tin is preferably used.

[0084] In the overcurrent state, the current flows into the inflow terminal 11, the inflow terminal pad 05, the fuse circuit 4, the outflow terminal pad 06 and the outflow terminal 12 in sequence. The fuse circuit 4 heats up and melts, thereby turning the overcurrent protection circuit from a path to an open circuit.

[0085] In the overvoltage state, the MOSFET in the overvoltage protection circuit causes the overvoltage protection circuit to be converted from an open circuit to a closed circuit. The overvoltage current sequentially enters the inflow terminal 11, the inflow terminal pad 05, the fuse circuit 4, the control terminal pad 07, the heating element inflow terminal pad 31, the heating element 3, the heating element outflow terminal pad 32 and the control terminal 13. The heating element 3 is made of a resistor. When the overvoltage current passes through the heating element 3, the heating element 3 heats up. The heat of the heating element 3 passes through the first insulating layer 2, thereby causing the fuse circuit 4 to melt, causing the overvoltage protection circuit to be converted from a closed circuit to an open circuit.

[0086] In this embodiment, a flux layer 5 is provided on the fuse circuit 4 , and the longitudinal projection position of the flux layer 5 overlaps with the longitudinal projection position of the heating element 3 by 80% to 100% of the area, and the longitudinal projection position of the heating element 3 is located within the longitudinal projection of the fuse circuit 4 .

[0087] The fluxing layer 5 is used to assist the fuse circuit 4 in melting. The longitudinal projection position of the fluxing layer 5 and the heating element 3 coincide with each other, so that when the heat of the heating element 3 is transferred to the fuse circuit 4, the fluxing layer 5 can better promote the melting of the fuse circuit 4 and improve the melting sensitivity of the fuse circuit 4; the longitudinal projection position of the fluxing layer 5 and the heating element 3 coincides with 80% of the area, or 90% of the area, or 100% of the area, and 100% of the overlapping area is the most preferred; the longitudinal projection position of the heating element 3 is located within the longitudinal projection of the fuse circuit 4, so that the heat of the heating element 3 can be accurately transferred to the fuse circuit 4, thereby causing the fuse circuit 4 to melt under overvoltage conditions.

[0088] In this embodiment, a second insulating layer 6 is provided on the first insulating layer 2 . The second insulating layer 6 is provided with a receiving groove 61 . The fluxing layer 5 is provided in the receiving groove 61 .

[0089] The heating element 3, the safety circuit 4, and the flux layer 5 can all be embedded in the first insulating layer 2 and the second insulating layer 6, thereby reducing the overall thickness of the components and the device.

[0090] In this embodiment, a solder resist layer 8 is provided on the second insulating layer 6, and a top cover 7 is provided on the solder resist layer 8. The solder resist layer 8 covers at least the upper surface of the fluxing layer 5. The solder resist layer 8 is used to prevent the fuse circuit 4 and / or the fluxing layer 5 from melting due to high-temperature sparks when soldering the top cover 7 or other components, thereby rendering the three-terminal circuit fuse unit useless. The top cover 7 is used to isolate sparks generated when the fuse layer and fluxing layer 5 melt, preventing them from burning other external components and devices.

[0091] In this embodiment, the materials of the inflow end 11, outflow end 12, and control end 13 are respectively at least one of copper, copper-iron-phosphorus alloy, copper-nickel-silicon alloy, copper-chromium-zirconium alloy, copper-silver alloy, and copper-tin alloy. The inflow end 11, outflow end 12, and control end 13 are preferably copper lead frames. Copper frames are commonly used in the production of circuit boards. The copper frame is filled with plastic encapsulation material, so that when the internal circuit pads of the three-terminal fuse are connected to the copper frame, the process flow of through-hole plugging is avoided, thereby allowing the three-terminal circuit protection unit to be mass-produced on a large scale, reducing complex processes and lowering costs. The plastic encapsulation material is filled between the pads in the substrate made of the copper frame to ensure that the pads will not short-circuit. At the same time, the characteristics of the copper frame also improve the overall thermal conductivity, so that the heat generated by the heating element 3 during overvoltage can be quickly transferred to the fuse circuit 4, making the fuse more sensitive.

[0092] In this embodiment, the material of the first insulating layer 2 includes at least one or more of a glass fiber material, an epoxy resin material, a phenolic resin material, a polyimide material, a polytetrafluoroethylene material, and a BT resin material. Specifically, the material of the first insulating layer 2 can be a glass fiber material, an epoxy resin material, a phenolic resin material, a polyimide material, a polytetrafluoroethylene material, a BT resin material, or a mixture of one or more of the following polyester film materials. In this embodiment, the first insulating layer 2 is preferably made of a material such as BT resin or PP, which has good heat resistance and / or thermal conductivity.

[0093] In this embodiment, the material of the second plastic encapsulation layer 14 includes at least one or more of a glass fiber material, an epoxy resin material, a phenolic resin material, a polyimide material, a polytetrafluoroethylene material, and a BT resin material. Specifically, the material of the second insulating layer 6 can be a glass fiber material, an epoxy resin material, a phenolic resin material, a polyimide material, a polytetrafluoroethylene material, a BT resin material, or a mixture of one or more of the following polyester film materials. In this embodiment, the second insulating layer 6 is preferably made of a material such as BT resin or PP, which has good heat resistance and / or thermal conductivity.

[0094] In this embodiment, the material of the safety circuit 4 is generally at least one of tin, lead, copper, silver, zinc, aluminum and any combination thereof. In this embodiment, tin and tin-copper alloy are preferred.

[0095] In this embodiment, the steps of manufacturing a three-terminal circuit protection unit are:

[0096] Step 1: Cutting the material. The substrate is a copper frame, but can also be any other commonly used conductive metal lead frame. The substrate supports the components and serves as a conductive pad for electrical connection to internal and external circuits. Specifically, the copper frame is configured with three separate terminals: an inlet port 11, an outlet port 12, and a control port 13.

[0097] Step 2: First pressing; filling the three terminals (inflow end 11, outflow end 12 and control end 13) and the upper surface of the copper frame with plastic compound, pressing the plastic compound to form a plastic layer 14, and burying the copper foil on the plastic layer 14;

[0098] Step 3: First pattern making; Pattern making is performed on the upper surface of the plastic layer 14 to add the heating element 3 and the pads at both ends of the heating element 3 (the heating element inlet end pad 31 and the heating element outlet end pad 32);

[0099] Step 4: Second lamination; Laminating the first insulating layer 2 and the copper foil on the upper surface of the heating element 3 and the plastic sealing layer 14, and forming the inflow end pad 05, the outflow end pad 06 and the control end pad 07 on the copper foil;

[0100] Step 5: Drilling; drilling holes at the positions of the three pads (inflow end pad 05, outflow end pad 06 and control end pad 07) formed on the copper foil to form an inflow end conductive hole 01, an outflow end conductive hole 02, and a control end conductive hole 13, so that the inflow end pad 05 is connected to the inflow end 11 through the inflow end conductive hole 01, the outflow end pad 06 is connected to the outflow end 12 through the outflow end conductive hole 02, the control end pad 07 is connected to the heating element inflow end pad 31 of the heating element through the inflow end conductive hole 01 of the heating element 3, and the heating element outflow end pad 32 of the heating element 3 is connected to the outflow end 12 through the outflow end conductive hole 02 of the heating element 3;

[0101] Step 6: Copper deposition and electroplating; make the blind holes and blind holes conductive; conduct electricity in the inlet conductive hole 01, the outlet conductive hole 02, the control end conductive hole 13, the heating element 3 inlet conductive hole 01 and the heating element 3 outlet conductive hole 02;

[0102] Step 7: Second pattern making: making the lines on the upper and lower surfaces of the three-terminal circuit protection unit;

[0103] Step 8: Fuse fabrication: A layer of tin, zinc, aluminum, or a composite alloy is added to the upper surfaces of the first insulating layer 2, the inflow pad 05, the outflow pad 06, and the control pad 07 by chemical deposition, evaporation, sputtering, or electroplating. This layer serves as a fuse circuit 4. The fuse circuit 4 is electrically connected to the inflow pad 05, the outflow pad 06, and the control pad 07.

[0104] Step nine: pressing; groove the insulating film material and press it onto the first insulating layer 2, the fuse circuit 4, the inflow end pad 05, the outflow end pad 06 and the control end pad 07 to form a second insulating layer 6. The groove on the second insulating layer 6 accommodates the through groove 61, and the fluxing layer 5 is arranged in the accommodating through groove 61.

[0105] Step 10: Apply flux; apply a flux layer 5 in the receiving groove 61, so that the flux layer 5 covers at least a portion of the upper surface of the insurance circuit 4;

[0106] Step 11: Solder mask and surface coating; Apply solder mask material on the upper and lower surfaces of the three-terminal circuit protection unit to form a solder mask layer 8; the material of the solder mask layer 8 can be commonly used materials such as epoxy resin and polyimide;

[0107] Step 12: Bonding the cover; bonding the top cover 7 on the solder resist layer 8 of the three-terminal circuit protection unit to complete the production of the three-terminal circuit protection unit.

[0108] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Under the idea of ​​the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes in different aspects of the present invention as described above. For the sake of simplicity, they are not provided in detail. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in this field should understand that it is still possible to modify the technical solutions recorded in the above embodiments, or to make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A three-terminal circuit protection unit, characterized in that: The invention comprises a support body (1), wherein the support body (1) is provided with a plastic sealing layer (14), an inflow end (11), an outflow end (12) and a control end (13), wherein the inflow end (11), the outflow end (12) and the control end (13) are arranged at the lower part of the support body (1), and the plastic sealing layer (14) is filled between each adjacent end and the upper part of the inflow end (11), the outflow end (12) and the control end (13); A heating element (3) and a first insulating layer (2) are provided on the upper portion of the support body (1), and the first insulating layer (2) is provided on the upper portion of the heating element (3); A safety circuit (4) is provided on the first insulating layer (2), and the safety circuit (4) is electrically connected to the inflow end (11), the outflow end (12), and the control end (13), respectively; In the overcurrent state, the fuse circuit (4) is blown; In an overvoltage state, the heating element (3) is electrically connected to the inflow end (11) and the control end (13) to form a control circuit. The heating element (3) generates heat, and the heat passes through the first insulating layer (2) to melt the safety circuit (4).

2. The three-terminal circuit protection unit according to claim 1, wherein: An inlet end pad (05), an outlet end pad (06) and a control end pad (07) are provided on the first insulating layer (2); the inlet end pad (05), the outlet end pad (06) and the control end pad (07) are electrically connected to the insurance circuit (4) respectively; The inflow end (11) is electrically connected to the inflow end pad (05) through the inflow end conductive hole (01), the outflow end (12) is electrically connected to the outflow end pad (06) through the outflow end conductive hole (02), and the control end (13) is electrically connected to the control end pad (07) through the heating element (3).

3. The three-terminal circuit protection unit according to claim 2, wherein: The control end (13) is electrically connected to the control end pad (07) via the heating element (3): a heating element inlet pad (31) and a heating element outlet pad (32) are respectively provided at both ends of the heating element (3); the control end pad (07) and the heating element outlet pad (32) are electrically connected via the heating element outlet conductive hole (04); and the inlet pad (05) and the heating element inlet pad (31) are electrically connected via the heating element inlet conductive hole (03).

4. The three-terminal circuit protection unit according to claim 3, wherein: A fluxing layer (5) is provided on the safety circuit (4), the longitudinal projection position of the fluxing layer (5) overlaps with the longitudinal projection position of the heating element (3) by 80% to 100% of its area, and the longitudinal projection position of the heating element (3) is located within the longitudinal projection of the safety circuit (4).

5. The three-terminal circuit protection unit according to claim 4, wherein: The invention also includes a top cover (7), the top cover (7) covers the first insulating layer (2), and the inflow end pad (05), the outflow end pad (06), the control end pad (07), the insurance circuit (4) and the fluxing layer (5) are located in a space formed by the top cover (7) and the first insulating layer (2).

6. The three-terminal circuit protection unit according to claim 4, wherein: A second insulating layer (6) is provided on the first insulating layer (2), the second insulating layer (6) is provided with a receiving groove (61), and the fluxing layer (5) is provided in the receiving groove (61).

7. The three-terminal circuit protection unit according to claim 6, wherein: A solder resist layer (8) is provided on the second insulating layer (6), and a top cover (7) is provided on the solder resist layer (8).

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