A bidirectional transient voltage suppression diode with built-in fuse

Abstract

The application discloses a bidirectional transient voltage suppression diode with a built-in fuse, which comprises a plastic sealing shell, and a bidirectional TVS tube, a fuse, a first electrode sheet and a second electrode sheet are packaged in the plastic sealing shell. One end of the bidirectional TVS tube is connected with a positive electrode lead wire, the other end is connected with one end of the fuse through the first electrode sheet, the other end of the fuse is connected with a negative electrode lead wire through the second electrode sheet, and the positive and negative electrode lead wires are bent and attached to the bottom from both sides of the plastic sealing shell. The bidirectional transient voltage suppression diode with a built-in fuse integrates surge protection and open-circuit failure protection functions, greatly reduces the PCB area, reduces the circuit design complexity, and significantly improves the mechanical strength and electrical reliability of the device through optimization of the lead wire structure and welding process.

Description

Technical Field

[0001] This invention relates to a bidirectional transient voltage suppression diode with a built-in fuse. Background Technology

[0002] Bidirectional transient voltage suppressor diodes (TVS) are core components in electronic circuits used for surge protection and voltage limiting. When subjected to high-energy transient overvoltage pulses, they can rapidly reduce impedance to extremely low levels, conduct large currents, and clamp the voltage to a safe level, protecting precision components from damage. In practical applications, to prevent TVS diodes from short-circuiting and causing system failure after being subjected to excessive surges, engineers commonly use a solution of discrete TVS diodes connected in series with independent fuses. This solution occupies a large PCB area, which contradicts the trend of miniaturization in electronic devices; it increases the workload of circuit design, requiring separate selection and matching of TVS diode and fuse parameters; it requires a large number of solder joints, increases potential failure points, and reduces the overall reliability of the system.

[0003] Current integrated technology solutions, such as CN105895623A which discloses a substrate design and its formation method for semiconductor packages, adopt a ceramic packaging structure, which is costly and bulky, and cannot meet the needs of low-cost surface mount applications; and CN110265372A which discloses a semiconductor device and wafer-level package with a redistribution structure and its manufacturing method, but its lead structure design is unreasonable, its mechanical strength is insufficient, and its internal space utilization is low, making it impossible to achieve a compact design. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the prior art by improving the traditional DO-214AB plastic encapsulation frame, integrating the bidirectional TVS tube and fuse into the same plastic solid package, and realizing a compact, low-cost, and highly reliable open-circuit failure type bidirectional TVS device through optimized internal structure and lead design.

[0005] The technical solution of the present invention: A bidirectional transient voltage suppressor diode with a built-in fuse includes a plastic-encapsulated housing containing a bidirectional TVS diode, a fuse, a first electrode, and a second electrode. One end of the bidirectional TVS diode is connected to the positive lead, and the other end is connected to one end of the fuse via the first electrode. The other end of the fuse is connected to the negative lead via the second electrode. The positive and negative leads extend from opposite sides of the plastic-encapsulated housing, with their ends bent and pressed against the bottom of the housing. By integrating the bidirectional TVS diode and fuse into a single package, the bidirectional TVS diode provides surge voltage clamping, and the fuse provides overcurrent protection. When a transient overvoltage pulse occurs in the circuit, the bidirectional TVS diode quickly conducts, clamping the voltage to a safe level. When the surge energy exceeds the bidirectional TVS diode's withstand capacity, causing it to short-circuit and fail, the large short-circuit current causes the fuse to quickly blow, isolating the failed device from the circuit and creating an open-circuit protection loop, preventing damage to the upstream power supply and downstream load. Meanwhile, the integrated design makes full use of the internal space of the package, reducing the PCB area by more than 50%, eliminating the need for additional fuse mounting locations, and significantly reducing the workload of circuit design.

[0006] Furthermore, both the positive and negative leads include a solder pad and a support frame. The solder pad is housed within the plastic encapsulation shell; the support frame is square, with one end extending into the plastic encapsulation shell to connect with the solder pad, and the other end fitting against the bottom of the plastic encapsulation shell. This combination of the solder pad and support frame provides ample soldering area, ensuring reliable electrical connection with internal components. The support frame increases the contact area between the lead and the plastic encapsulation shell, improving the lead's mechanical strength and adhesion, preventing detachment or breakage during use. The square support frame structure effectively disperses stress, enhancing the device's vibration and impact resistance.

[0007] Furthermore, the solder pads on the positive and negative leads are on the same plane. By making the two solder pads coplanar, it is ensured that the bidirectional TVS tube, the first electrode plate, the fuse, and the second electrode plate can be assembled on the same horizontal plane, improving assembly accuracy and consistency, avoiding welding defects or stress concentration problems caused by height differences, and improving product yield.

[0008] Furthermore, the welding base and support frame are integrally molded, with the welding base connected to the support frame at one parallel end. A Z-shaped bend ensures that the height of the welding base is lower than the upper height of the support frame. This integral molding process guarantees the overall strength and conductivity of the lead wires, avoiding contact resistance and mechanical strength issues associated with separate connections. The height difference created by the Z-shaped bend provides ample space for internal component installation, while also forming a stress-buffering structure at the bend, effectively absorbing stress generated by thermal expansion and contraction, and improving the device's temperature cycling reliability.

[0009] Furthermore, the top and bottom ends of the sidewalls of the plastic package are machined into bevels, and there is a gap between the middle of the support frame and the plastic package. The bevels on the sidewalls of the plastic package facilitate the mounting and soldering of components on the PCB, improving production efficiency. The gap between the middle of the support frame and the plastic package forms a thermal expansion buffer space, relieving the stress caused by the difference in thermal expansion coefficients between the molding compound and the metal leads, and preventing the plastic package from cracking or the leads from falling off.

[0010] Furthermore, the bidirectional TVS diode is fixed to the first electrode plate and the positive lead, and the fuse is fixed to the second electrode plate and the negative lead using solder paste. Solder paste welding is a simple and efficient process that simultaneously achieves mechanical fixing and electrical connection between conductive components, resulting in welded joints with good conductivity and mechanical strength.

[0011] Furthermore, the solder paste is a high-temperature sintered solder paste, used to achieve mechanical fixation and low-impedance electrical connection between various conductive components. The high-temperature sintered solder paste forms a metallurgical bond at high temperatures, resulting in stronger weld joints, better conductivity, and excellent high-temperature resistance and anti-aging properties, significantly improving the long-term reliability and lifespan of the device. Low-impedance electrical connections reduce power loss and improve device operating efficiency.

[0012] Furthermore, the height of the second electrode is equal to the sum of the heights of the first electrode and the bidirectional TVS diode. By precisely matching the height of the second electrode, the fuse can be placed horizontally above the first and second electrodes, ensuring uniform force distribution at both ends of the fuse and avoiding poor soldering or stress concentration problems caused by tilting. This height-matching design makes full use of the vertical space inside the package, resulting in a more compact overall structure.

[0013] Furthermore, the encapsulated housing is integrally molded from epoxy resin molding compound, completely sealing and encapsulating the bidirectional TVS diode, fuse, first electrode plate, second electrode plate, and the portions of the negative and positive leads that extend into the housing. Epoxy resin molding compound possesses excellent insulation properties and mechanical strength. Integral molding provides comprehensive protection for the internal components, preventing the intrusion of dust, moisture, and harmful substances, thus improving the device's environmental adaptability. The completely sealed structure also prevents mechanical damage to the internal components, further enhancing the device's vibration and shock resistance.

[0014] The beneficial effects of this invention are: 1. Advantages of integrated design: The bidirectional TVS diode and fuse are integrated into the same package, realizing the integration of surge protection and open circuit failure protection. Compared with the traditional discrete solution, the PCB area is reduced by more than 50%, and there is no need to match the fuse parameters, which greatly reduces the complexity of circuit design and production costs.

[0015] 2. Improved mechanical performance: The integrated lead structure combining the welding base and support frame is adopted, and stress buffering is formed by Z-shaped bending, which significantly improves the mechanical strength and adhesion of the lead, and enhances the device's vibration and impact resistance by more than 30%.

[0016] 3. Enhanced electrical reliability: The use of high-temperature sintered solder paste to form a low-impedance metallurgical bond significantly improves the reliability of the welded joints, eliminates parasitic parameters in board-level connections, accelerates surge response speed by more than 20%, and extends the mean time between failures of devices by more than 2 times.

[0017] 4. Compact and efficient structure: By precisely controlling the size and position of each component, the internal space utilization is maximized, the overall structure is compact, the assembly accuracy and consistency are high, and the production efficiency and product yield are significantly improved.

[0018] 5. Strong environmental adaptability: The epoxy resin molded one-piece encapsulated shell has excellent insulation, moisture-proof and corrosion-proof properties, and can work stably in harsh industrial environments. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the present invention.

[0020] Figure 2 This is a schematic diagram of the circuit principle of the present invention.

[0021] Figure 3 This is a schematic diagram illustrating the application principle of the present invention in a circuit.

[0022] Figure 4 This is a schematic diagram of the external structure of the present invention.

[0023] In the diagram: 1-Plastic encapsulation shell, 2-Solder paste, 3-First electrode sheet, 4-Bidirectional TVS tube, 5-Fuse, 6-Second electrode, 7-Negative lead, 71-Soldering base, 72-Support frame, 8-Positive lead. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0025] Example 1: like Figures 1-4As shown, the bidirectional transient voltage suppressor diode with a built-in fuse provided in this embodiment includes a plastic encapsulation housing 1, within which a bidirectional TVS diode 4, a fuse 5, a first electrode plate 3, and a second electrode plate 6 are encapsulated. One end of the bidirectional TVS diode 4 is connected to the positive lead 8, and the other end is connected to one end of the fuse 5 via the first electrode plate 3. The other end of the fuse 5 is connected to the negative lead 7 via the second electrode plate 6. The positive lead 8 and the negative lead 7 extend from opposite sides of the plastic encapsulation housing 1, and their ends are bent relative to each other and then tightly attached to the bottom ends of the plastic encapsulation housing 1.

[0026] Both the positive lead 8 and the negative lead 7 include a soldering base 71 and a support frame 72. The soldering base 71 is placed inside the plastic encapsulation shell 1. The support frame 72 is square, with one end extending into the plastic encapsulation shell 1 and connecting to the soldering base 71, and the other end fitting against the bottom of the plastic encapsulation shell 1. The soldering bases 71 on the positive lead 8 and the negative lead 7 are on the same plane. The soldering base 71 and the support frame 72 are integrally formed, with the connection end of the soldering base 71 parallel to that of the support frame 72. A Z-shaped bend is used to make the height of the soldering base 71 lower than the height of the upper end of the support frame 72. The upper and lower ends of the sidewall of the plastic encapsulation shell 1 are machined into bevels, and a gap is left between the middle of the support frame 72 and the plastic encapsulation shell 1.

[0027] The bidirectional TVS diode 4 is fixed to the first electrode plate 3 and the positive lead 8, and the fuse 5 is fixed to the second electrode plate 6 and the negative lead 7 by high-temperature sintering solder paste 2. The height of the second electrode plate 6 is equal to the sum of the heights of the first electrode plate 3 and the bidirectional TVS diode 4. The plastic-encapsulated shell 1 is integrally molded from epoxy resin through a molding process, completely sealing and encapsulating the internal parts of all internal components and leads.

[0028] Operating Procedure: Under normal operating conditions, the bidirectional TVS diode 4 is in the off state, and the circuit current flows to the load through fuse 5. The device presents high impedance, which does not affect the normal operation of the circuit. When a transient overvoltage pulse occurs in the circuit, the bidirectional TVS diode 4 quickly conducts within nanoseconds, its impedance drops to an extremely low level, allowing a large current to pass through, while clamping the voltage to a predetermined safe level to protect the precision components downstream. At this time, the current that fuse 5 withstands is within its rated range, and it will not blow.

[0029] When the surge energy exceeds the withstand capacity of the bidirectional TVS diode 4, the TVS diode breaks down and eventually short-circuits, resulting in a very large short-circuit current in the circuit. When this current flows through the fuse 5, it causes the fuse element to heat up rapidly and melt, completely isolating the failed bidirectional TVS diode 4 from the circuit. The protection circuit is in an open-circuit state, preventing damage to the upstream power supply due to short circuit, while ensuring that the downstream load is not impacted by the short-circuit current, thus ensuring the safety of the entire system.

[0030] Implementation Results: The devices in this embodiment use a DO-214AB compatible package size. Compared with traditional discrete solutions, the PCB area occupied is reduced from approximately 20mm². 2 Reduced to approximately 9mm 2 It saves 55% of space. The surge response time is less than 1ns, which is 25% faster than discrete solutions. Reliability testing shows that the device can withstand 1000 temperature cycles from -40℃ to 125℃ without failure, has a vibration resistance of 20g, and an impact resistance of 1000g, fully meeting the requirements of industrial applications.

[0031] Example 1: Depending on the voltage level and surge energy requirements of different application scenarios, bidirectional TVS diode chips and fuses of different specifications can be selected. For example, for a 12V power supply system, a bidirectional TVS diode with a breakdown voltage of 18V and a fuse with a rated current of 5A can be selected; for a 24V power supply system, a bidirectional TVS diode with a breakdown voltage of 36V and a fuse with a rated current of 3A can be selected.

[0032] Example 2: The structure of this invention can be extended to other surface mount package sizes, such as DO-214AA and DO-214AC, to adapt to different PCB design requirements. Only the dimensions of the plastic package and the proportions of the internal components need to be adjusted accordingly to maintain the same functionality and performance.

[0033] Example 3: Multiple independent open-circuit failure TVS units can be integrated into the same package to form a multi-channel protection device. For example, two units can be integrated together to achieve simultaneous protection of positive and negative power lines; or four units can be integrated together to achieve protection of four signal lines.

Claims

1. A bidirectional transient voltage suppressor diode with a built-in fuse, characterized in that: The encapsulated housing (1) contains a bidirectional TVS tube (4), a fuse (5), a first electrode plate (3), and a second electrode (6). One end of the bidirectional TVS tube (4) is connected to the positive lead (8), and the other end of the bidirectional TVS tube (4) is connected to one end of the fuse (5) through the first electrode plate (3). The other end of the fuse (5) is connected to the negative lead (7) through the second electrode plate (6). The positive lead (8) and negative lead (7) extend from opposite sides of the plastic-encapsulated shell (1), and their ends are bent and attached to the bottom of the plastic-encapsulated shell (1).

2. The bidirectional transient voltage suppression diode with a built-in fuse according to claim 1, characterized in that: Both the positive lead (8) and the negative lead (7) include a soldering base (71) and a support frame (72), with the soldering base (71) placed inside the plastic-encapsulated shell (1); The support frame (72) is square, with one end extending into the plastic-encapsulated shell (1) and connecting to the welding seat (71), and the other end fitting against the bottom of the plastic-encapsulated shell (1).

3. The bidirectional transient voltage suppression diode with a built-in fuse according to claim 2, characterized in that: The soldering bases (71) on the positive lead (8) and the negative lead (7) are on the same plane.

4. The bidirectional transient voltage suppression diode with a built-in fuse according to claim 2, characterized in that: The welding seat (71) and the support frame (72) are integrally formed. The welding seat (71) is connected to the support frame (72) at one end parallel to it, and the height of the welding seat (71) is lower than the height of the upper end of the support frame (72) by Z-shaped bending.

5. The bidirectional transient voltage suppression diode with a built-in fuse according to claim 2, characterized in that: The upper and lower ends of the side wall of the plastic-encapsulated shell (1) are respectively processed into bevels, and there is a gap between the middle of the support frame (72) and the plastic-encapsulated shell (1).

6. The bidirectional transient voltage suppression diode with a built-in fuse according to claim 1, characterized in that: The bidirectional TVS tube (4) is fixed to the first electrode plate (3) and the positive lead (8) by solder paste (2), and the fuse (5) is fixed to the second electrode plate (6) and the negative lead (7).

7. The bidirectional transient voltage suppression diode with a built-in fuse according to claim 6, characterized in that: The solder paste (2) is a high-temperature sintered solder paste used to achieve mechanical fixation and low-impedance electrical connection between various conductive components.

8. The bidirectional transient voltage suppression diode with a built-in fuse according to claim 1, characterized in that: The height of the second electrode plate (6) is equal to the sum of the height of the first electrode plate (3) and the bidirectional TVS tube (4).

9. The bidirectional transient voltage suppression diode with a built-in fuse according to claim 1, characterized in that: The encapsulated shell (1) is integrally molded from epoxy resin encapsulating material through a molding process, and completely seals and encapsulates the bidirectional TVS tube (4), fuse (5), first electrode plate (3), second electrode (6), and the portions of the negative electrode lead (7) and positive electrode lead (8) that extend into the encapsulated shell (1).

Images