High-power TVS (Transient Voltage Suppressor) applied to vehicle gauge system and preparation method

Abstract

The invention relates to the technical field of semiconductors, in particular to a high-power TVS (Transient Voltage Suppressor) applied to a vehicle gauge system and a preparation method. Comprising a first frame which comprises a pin area, a bending area and a first connecting area which are connected in sequence; the first connecting area is provided with a first chip connecting area which protrudes upwards; the first chip is electrically connected to the first chip bearing area; the second chip is positioned on the top surface of the first chip and is electrically connected with the first chip; one end of the copper clamping piece is provided with a second chip connecting area which protrudes downwards and is electrically connected with the top surface of the second chip; the second frame is fixedly connected with the other end of the copper clamping piece; and the plastic package body wraps the copper clamping piece, the second chip, the first chip, the bending area and the first connecting area. The connection failure risk under vehicle-mounted working conditions such as vibration and impact is reduced, and the mechanical stability of the device is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a high-power TVS for automotive-grade systems and its fabrication method. Background Technology

[0002] A high-power TVS (Transient Voltage Suppressor) is a power semiconductor device used to suppress transient overvoltages. It is a derivative of the Zener diode and is specifically designed for high-energy transient interference (such as lightning strikes, surges, and power grid fluctuations). It can clamp excessively high voltages to a safe level within nanoseconds, protecting downstream circuits or equipment from damage. Compared to ordinary low-power TVS, high-power TVS has higher peak pulse power (typically from hundreds of watts to kilowatts, or even megawatts) and greater current carrying capacity, making it suitable for scenarios requiring high-energy transient impacts, such as power systems, industrial control, new energy, and rail transportation.

[0003] The core structure of high-power TVS is based on the PN junction avalanche breakdown principle. It includes components such as chips, packages, and electrodes, and is widely used in on-board charging systems, battery management systems, and sensor protection.

[0004] However, existing high-power TVS devices face severe heat dissipation bottlenecks in high-power-density applications, which seriously restricts the reliability and lifespan of the devices. The problem of heat accumulation is prominent: When high-power TVS discharges transient energy, the avalanche breakdown process generates a large amount of Joule heat, and the heat is released in a short period of time from nanoseconds to microseconds. However, the thermal conductivity of materials such as epoxy resin and alumina ceramic used in existing packaging technologies is low (e.g., the thermal conductivity of alumina ceramic is only 20~30 W / (m・K)). Factors such as air gaps in the packaging structure and the interfacial thermal resistance between the chip and the substrate cause the heat conduction efficiency to be much lower than the heat generation rate. Heat is easily retained inside the chip and the package, causing the chip to overheat and be damaged.

[0005] Local hot spots pose a risk of failure: Power semiconductor chips themselves have problems such as uneven doping uniformity and uneven electrode contact resistance. In addition, packaging stress can easily cause gaps in chip bonding, resulting in severely uneven chip temperature distribution. The temperature of local hot spots can reach 1.5 to 2 times the overall temperature. Local hot spots will generate significant thermal and temperature stress, which will accelerate the occurrence of failure modes such as bond wire detachment, solder layer fatigue, and package delamination, and may even lead to thermal fatigue failure.

[0006] Packaging heat dissipation capacity cannot match the demand for increased power density: As the power density of power electronic devices continues to increase, the transient power and current carrying capacity requirements of high-power TVS are constantly being upgraded. However, the heat dissipation design of traditional packaging structures (such as bolt-on, modular, and surface-mount packaging) has not been optimized in sync. The heat conduction path of the package is blocked, and the heat generated by the chip cannot be effectively transferred to the external heat dissipation system. This leads to a continuous decline in the reliability of the device during long-term operation, making it difficult to meet the stable operation requirements in high power density scenarios.

[0007] The aforementioned heat dissipation-related issues not only limit the further improvement of the power density of high-power TVS, but also pose a serious threat to its long-term stability, becoming a key technical bottleneck restricting the large-scale application of high-power TVS in the field of high-end power electronics. Summary of the Invention

[0008] To address the above problems, this invention provides a high-power TVS for automotive-grade systems and its fabrication method that overcomes the limitation of heat dissipation bottlenecks on increasing the power density of high-power TVS within existing size specifications, thus solving the problem that its heat dissipation defects prevent its large-scale application in the field of high-end power electronics.

[0009] The technical solution of this invention is: A high-power TVS for automotive-grade systems includes: The first frame includes a pin area, a bending area, and a first connection area connected in sequence; the first connection area is provided with an upwardly protruding first chip connection area. The first chip is electrically connected to the first chip carrier area; The second chip is located on the top surface of the first chip and is electrically connected to the first chip; The copper clip has a second chip connection area at one end that protrudes downward and is electrically connected to the top surface of the second chip; The second frame is fixedly connected to the other end of the copper clip; The molding compound is wrapped around the copper clip, the second chip, the first chip, the bending area, and the first connection area.

[0010] Specifically, one end of the copper clip extends upward and is provided with a first horizontal extension.

[0011] Specifically, the other end of the copper clip extends downward and is provided with a second horizontal extension.

[0012] Specifically, the negative terminal of the first chip is electrically connected to the connection area of ​​the first chip.

[0013] Specifically, the positive terminal of the first chip is electrically connected to the negative terminal of the second chip.

[0014] Specifically, the positive electrode of the second chip is electrically connected to the copper clip.

[0015] Specifically, the first frame and / or the second frame are provided with V-shaped grooves located within the molding compound.

[0016] Specifically, the first chip and the second chip are connected by a high-lead solder paste layer.

[0017] Specifically, the first frame and the second frame extend downward from the outer ends of the encapsulated body, respectively.

[0018] A method for fabricating a high-power TVS for automotive-grade systems includes the following steps: Step 1: Mechanically roughen the copper clip and the second chip connection surface to make the surface roughness Ra > 3um; Step 2: Fix the first frame and the second frame onto the automatic line track respectively, and clamp them with the finger clamps; Step 3: Using a matching dispensing tip, apply solder paste to the first chip connection area of ​​the first frame, near the center. Step 4: After picking up the first chip, attach it to the first chip connection area; Step 5: Using a matching dispensing tip, apply solder paste to the surface of the first chip, near the center area. Step 6: After picking up the second chip, attach it to the surface of the first chip; Step 7: Using a matching dispensing tip, apply solder paste to the surface of the second chip, near the center area. Step 8: Take the copper clip after the mechanical roughening process in Step 1 and place it on the second chip to interconnect the connection area of ​​the second chip with the second chip. Step nine: After the second frame is extracted, it is welded to the copper clips; Step 10: Place the product completed in Step 9 into a vacuum reflow soldering furnace or tunnel furnace for sintering; after sintering, seal, cure, pre-cut ribs, tin plate, and shape the ribs.

[0019] This invention employs copper clips to achieve front-side interconnection of the second chip. Compared to traditional wire bonding, the high thermal conductivity of the copper clips significantly reduces the thermal resistance between the chip and external circuitry, accelerating the conduction of transient Joule heat generated during chip operation. Simultaneously, the raised connection structure between the copper clips and the second chip increases the contact area, further optimizing the heat transfer path and effectively solving the problems of heat retention and localized hot spots under high power density, preventing chip damage due to overheating. The first frame, through the integrated design of the pin area, bending area, and first connection area, combined with the rigid connection between the second frame and the copper clips, replaces the flexible connection of traditional leads, reducing the risk of connection failure under automotive conditions such as vibration and impact, and improving the mechanical stability of the device. Attached Figure Description

[0020] Figure 1 This is a three-dimensional structural diagram illustrating the connection between the chip and the frame. Figure 2 This is a schematic diagram of the three-dimensional structure of the first frame; Figure 3 This is a schematic diagram of the three-dimensional structure of the second frame; Figure 4 This is a schematic diagram of the three-dimensional structure after plastic sealing; Figure 5 This is a schematic diagram of the three-dimensional structure after the pins are bent. In the diagram, 100 represents the first frame, 110 the pin area, 120 the bending area, 130 the first connection area, and 131 the first chip connection area. 200 is the first chip. 300 is the second chip. 400 is a copper clip, 410 is the second chip connection area, 420 is the first horizontal extension, and 430 is the second horizontal extension. 500 is the second framework. 600 is a plastic encapsulated form. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0022] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "vertical," and "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] The following is for reference. Figure 1-5 Describe the present invention; A high-power TVS for automotive-grade systems includes: The first frame 100 includes a pin area 110, a bending area 120 and a first connection area 130 connected in sequence; the first connection area 130 is provided with an upwardly protruding first chip connection area 131. The first chip 200 is electrically connected to the first chip carrier area 130; Specifically, the negative electrode of the first chip 200 is electrically connected to the first chip connection region 131. The positive electrode of the first chip 200 is electrically connected to the negative electrode of the second chip 300. This invention adopts a double-layer cascaded structure. The interconnection and sintering of the first chip 200 and the second chip 300 is achieved using high-lead solder paste, removing the metal oxide layer on the chip surface to form a high-bonding, high-thermal-conductivity connection layer with a void ratio of <15% and a shear strength >40MPa.

[0025] The second chip 300 is located on the top surface of the first chip 200 and is electrically connected to the first chip 200; the positive terminal of the second chip 300 is electrically connected to the copper clip 400. The first chip 200 and the second chip 300 are connected by a high-lead solder paste layer with a lead content exceeding 37%.

[0026] The copper clip 400 has a second chip connection area 410 at one end that protrudes downward and is electrically connected to the top surface of the second chip 300; one end of the copper clip 400 extends upward and has a first horizontal extension 420. The other end of the copper clip 400 extends downward and has a second horizontal extension 430 for welding to the second frame 500. In this case, the width of the copper clip 400 is greater than the width of the second frame 500.

[0027] While pure copper clips have high thermal conductivity, their large coefficient of thermal expansion can easily lead to packaging stress due to thermal expansion mismatch with the chip. Furthermore, the frame is prone to breakage under vehicle vibration conditions due to excessive rigidity, resulting in interruption of the heat dissipation path. This copper clip 400 utilizes an oxygen-free copper-graphene composite material with a micro-nano textured surface. The graphene composite copper clip increases thermal conductivity by 20%, while the micro-nano texture increases the contact area with the chip by 40%, further reducing interfacial thermal resistance. Further optimization involves creating an annular perforated groove in the second chip connection area 410 and / or the first chip connection area 131. An annular thermally conductive ceramic element can be fixedly connected within this groove, allowing for rapid heat dissipation from the chip. Simultaneously, a rectangular hole is provided between the second chip connection area 410 and the second horizontal extension 430 (at the interval from the second chip 300) to facilitate gas removal during soldering, reduce solder voids, lower product thermal resistance, and improve product performance.

[0028] The second frame 500 is fixedly connected to the other end of the copper clip 400; the first frame 100 and the second frame 500 are made of copper-tungsten alloy (W content 30%). The thermal expansion coefficient of the copper-tungsten alloy frame is matched with that of the SiC chip by 50%, reducing the risk of chip cracking caused by thermal stress. The bending area buffer structure increases the frame's vibration fatigue life by 3 times and ensures long-term stability of the heat dissipation path.

[0029] The first frame 100 and / or the second frame 500 of this invention are provided with V-shaped grooves located within the molding compound 600. Through their connection with the molding compound 600, these grooves improve the device's resistance to moisture and block the entry of moisture along the frame interface. The first frame 100 and the second frame 500 extend downwards from the outer ends of the molding compound 600, as shown... Figure 5 As shown.

[0030] The molding compound 600 is wrapped around the copper clip 400, the second chip 300, the first chip 200, the bending area 120 and the first connection area 130.

[0031] The first connection area 130 of the first frame 100 features an upwardly protruding first chip connection area 131, which, together with the protruding second chip connection area 410 of the copper clip 400, makes the chip stacking layout more compact and the heat dissipation path shorter. Combined with the encapsulation of the core heat-generating components by the molding compound 600, heat accumulation inside the package is reduced, improving the overall heat dissipation efficiency of the device. The low impedance characteristics and large-area interconnect structure of the copper clip 400 can quickly dissipate transient high-energy currents such as lightning strikes and surges. Compared with the thin wire connections of wire bonding, it avoids the risk of local overheating or melting caused by current concentration, significantly improving the device's ability to withstand transient lightning surges and meeting the reliability requirements of automotive-grade systems under extreme operating conditions.

[0032] In this case, the first chip 200 and the second chip 300 are interconnected using high-lead solder paste, with a solder layer thickness of 40-60um; the first chip 200 and the raised first chip connection area 131 are interconnected using high-lead solder paste, with a solder layer thickness of 20-40um; the second chip 300 and the second chip connection area 410 are interconnected using high-lead solder paste, with a solder layer thickness of 20-40um; through the corresponding uniform solder paste layer thickness, the heat of the chip is quickly dissipated, avoiding the formation of hot spots on the chip surface and improving the thermal conductivity of the product.

[0033] A method for fabricating a high-power TVS for automotive-grade systems includes the following steps: Step 1: Mechanical roughening process is performed on the connection surface between the copper clip 400 and the second chip 300 to make the surface roughness Ra>3um, thereby improving product delamination and enhancing the interfacial bonding of the product. Step 2: Fix the first frame 100 and the second frame 500 on the automatic line track respectively, and clamp them with the finger clamps; Step 3: Using a matching dispensing head, apply solder paste to the first chip connection area 131 of the first frame 100 near the center. Step 4: After picking up the first chip 200, attach it to the first chip connection area 131; Step 5: Apply solder paste to the surface of the first chip 200 near the center using a matching dispensing head. Step 6: After picking up the second chip 300, attach it to the surface of the first chip 200; Step 7: Using a matching dispensing head, apply solder paste to the surface of the second chip 300, near the center area. Step 8: Take the copper clip 400 after the mechanical roughening process in Step 1 and place it on the second chip 300, so that the second chip connection area 410 is interconnected with the second chip 300. Step 9: After the second frame 500 is extracted, it is welded to the copper clip 400; Step 10: Place the product completed in Step 9 into a vacuum reflow soldering furnace or tunnel furnace for sintering; after sintering, seal, cure, pre-cut ribs, tin plate, and shape the ribs.

[0034] The molding compound 600 in this case uses a molding compound material with a flexural modulus of 450 N / mm², which improves the mechanical strength and resistance to bending deformation of the product after aging at 150°C, and enhances the structural stability, crack resistance and thermal cycle life of the encapsulation.

[0035] Regarding the information disclosed in this case, the following points need to be clarified: (1) The accompanying drawings of the embodiments disclosed in this case only involve the structures involved in the embodiments disclosed in this case. Other structures can refer to the general design. (2) Where there is no conflict, the embodiments and features disclosed in this case can be combined with each other to obtain new embodiments; The above are merely specific embodiments disclosed in this case, but the scope of protection of this disclosure is not limited thereto. The scope of protection disclosed in this case shall be determined by the scope of protection of the claims.

Claims

1. A high-power TVS for automotive-grade systems, characterized in that, include: The first frame (100) includes a pin area (110), a bending area (120) and a first connection area (130) connected in sequence; the first connection area (130) is provided with an upwardly protruding first chip connection area (131). The first chip (200) is electrically connected to the first chip carrier area (130); The second chip (300) is located on the top surface of the first chip (200) and is electrically connected to the first chip (200); The copper clip (400) has a second chip connection area (410) at one end that protrudes downward and is electrically connected to the top surface of the second chip (300). The second frame (500) is fixedly connected to the other end of the copper clip (400); A molding compound (600) is wrapped around the copper clip (400), the second chip (300), the first chip (200), the bending area (120), and the first connection area (130).

2. The high-power TVS applied to automotive-grade systems according to claim 1, characterized in that, The end of one end of the copper clip (400) extends upward and is provided with a first horizontal extension (420).

3. A high-power TVS for automotive-grade systems according to claim 1, characterized in that, The other end of the copper clip (400) extends downward and is provided with a second horizontal extension (430).

4. A high-power TVS for automotive-grade systems according to claim 1, characterized in that, The negative terminal of the first chip (200) is electrically connected to the first chip connection area (131).

5. A high-power TVS for automotive-grade systems according to claim 1, characterized in that, The positive terminal of the first chip (200) is electrically connected to the negative terminal of the second chip (300).

6. A high-power TVS for automotive-grade systems according to claim 1, characterized in that, The positive electrode of the second chip (300) is electrically connected to the copper clip (400).

7. A high-power TVS for automotive-grade systems according to claim 1, characterized in that, The first frame (100) and / or the second frame (500) are provided with V-shaped grooves located within the encapsulated body (600).

8. A high-power TVS for automotive-grade systems according to claim 1, characterized in that, The first chip (200) and the second chip (300) are connected by a high-lead solder paste layer.

9. A high-power TVS for automotive-grade systems according to claim 1, characterized in that, The first frame (100) and the second frame (500) extend downward from the outer ends of the encapsulated body (600).

10. A method for fabricating a high-power TVS for automotive-grade systems, as described in claim 1, characterized in that... Includes the following steps: Step 1: Mechanical roughening process is performed on the connection surface between the copper clip (400) and the second chip (300) to make the surface roughness Ra > 3um; Step 2: Fix the first frame (100) and the second frame (500) on the automatic line track respectively, and clamp them by pressing fingers; Step 3: Using a matching dispensing head, apply solder paste to the first chip connection area (131) of the first frame (100) near the center region; Step 4: After picking up the first chip (200), attach it to the first chip connection area (131); Step 5: Apply solder paste to the surface of the first chip (200) near the center area using a matching dispensing head; Step 6: After picking up the second chip (300), attach it to the surface of the first chip (200); Step 7: Using a matching dispensing head, apply solder paste to the surface of the second chip (300) near the center area; Step 8: Take the copper clip (400) after the mechanical roughening process in Step 1 and place it on the second chip (300) so that the connection area (410) of the second chip is interconnected with the second chip (300); Step nine: After the second frame (500) is taken out, it is welded to the copper clip (400); Step 10: Place the product completed in Step 9 into a vacuum reflow soldering furnace or tunnel furnace for sintering; after sintering, seal, cure, pre-cut ribs, tin plate, and shape the ribs.

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