A copper-aluminum hybrid interconnection packaging structure for car-grade discrete devices

Abstract

The utility model relates to the technical field of semiconductor packaging, specifically relates to a copper-aluminum hybrid interconnection packaging structure for vehicle-grade discrete devices, which comprises a lead frame, the lead frame comprises a first lead frame, a second lead frame and a third lead frame that are electrically isolated from each other; a chip is fixed on the first lead frame; a copper clamp, the first end surface of the copper clamp is fixed on the first electrode area of the chip, and the second end surface is fixed on the second lead frame; an aluminum connecting piece, the first end of the aluminum connecting piece is connected to the second electrode area of the chip, and the second end is connected to the third lead frame. The utility model improves the conductivity and heat dissipation performance of the main current path through the copper clamp, and realizes signal connection by using aluminum wire. While optimizing electrical performance and reducing parasitic inductance, the reliability and cost are taken into account, meeting the stringent requirements of vehicle-grade devices under high frequency, large current and high temperature.

Description

Technical Field

[0001] This utility model relates to the field of semiconductor packaging technology, specifically to a copper-aluminum hybrid interconnect packaging structure for automotive-grade discrete devices. Background Technology

[0002] As power electronic devices continue to evolve towards higher efficiency, higher power density, and higher reliability, the internal interconnect structure of discrete devices has become one of the key factors affecting overall performance. In existing processes, aluminum-based wire bonding technology has become the mainstream solution for low- and medium-power applications due to its low cost and strong adaptability. However, limited by the inherent physical properties of aluminum, this technology has gradually revealed performance deficiencies in high-frequency, high-current, and high-temperature operating scenarios, making it difficult to meet the increasingly stringent electrical and thermal management requirements.

[0003] Although the industry has tried to optimize traditional aluminum interconnect technology locally by increasing the bonding area, it is still unable to overcome the bottlenecks in the material's electrical and thermal conductivity.

[0004] Therefore, how to effectively improve the conductivity, thermal conductivity and long-term reliability of interconnect structures while controlling costs has become a core issue that urgently needs to be addressed in the process of discrete devices expanding into high-power and high-frequency applications. Utility Model Content

[0005] To address the above technical problems, this utility model provides a technical solution for a copper-aluminum hybrid interconnect packaging structure for automotive-grade discrete devices.

[0006] The technical problem solved by this utility model can be achieved by the following technical solution: A copper-aluminum hybrid interconnect package structure for automotive-grade discrete devices includes: A lead frame, the lead frame comprising a first lead frame, a second lead frame, and a third lead frame that are electrically isolated from each other; The chip is fixed to the first lead frame; A copper clip, wherein the first end face of the copper clip is fixed to the first electrode area of ​​the chip, and the second end face is fixed to the second lead frame; An aluminum connector, wherein the first end of the aluminum connector is connected to the second electrode region of the chip, and the second end is connected to the third lead frame.

[0007] Preferably, the first electrode region of the chip is the source or emitter main current channel, and the second electrode region is the gate or gate signal channel.

[0008] Preferably, the first lead frame has an integrally formed heat dissipation area and a chip soldering area; The chip is fixed to the chip soldering area by solder.

[0009] Preferably, the first end face of the copper clip is fixed to the first electrode region of the chip by a sintered bonding layer, and the second end face of the copper clip is fixed to the pin bonding region of the second lead frame by solder.

[0010] Preferably, the pin bonding area extends in a direction away from the chip to form a plurality of side-by-side main power pins.

[0011] Preferably, the second end of the aluminum connector is connected to the pin bonding area of ​​the third lead frame; The pin bonding area extends in a direction away from the chip to form signal pins.

[0012] Preferably, the package further includes a housing, which covers the top of the first lead frame, the second lead frame, and the third lead frame, and the heat dissipation area of ​​the first lead frame, the main power pin of the second lead frame, and the signal pin of the third lead frame are all exposed outside the housing.

[0013] Preferably, the first end face of the copper clip is provided with a groove that is adapted to the surface structure of the chip.

[0014] Preferably, the thickness of the copper clip is 0.2 mm to 0.4 mm.

[0015] Preferably, the aluminum connector is an aluminum wire with a diameter of 5 mil.

[0016] Beneficial effects: This utility model significantly improves the conductivity and heat dissipation efficiency of the main current path by introducing copper clips with high electrical and thermal conductivity to connect the first electrode of the chip and the second lead frame. At the same time, it uses aluminum connectors to be compatible with chip processes and connect the third lead frame. While optimizing electrical performance and reducing parasitic inductance, it also takes into account reliability and cost control, effectively meeting the stringent requirements of automotive-grade discrete devices for interconnect structure performance under high frequency, high current and high temperature conditions. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the internal interconnection of the packaging structure of this utility model; Figure 2 This is an enlarged view showing the details of the chip and copper clip welding of this utility model; Figure 3 This is a schematic diagram of the copper clip planar structure of this utility model; Figure 4 This is a schematic diagram of the cross-sectional structure of the copper clip of this utility model; Figure 5 This is a schematic diagram of the overall packaging structure of this utility model.

[0018] Explanation of reference numerals in the attached diagram: 1. First lead frame; 11. Heat dissipation area; 12. Chip soldering area; 2. Second lead frame; 21. Main power pin; 3. Third lead frame; 31. Signal pin; 4. Chip; 41. First electrode area; 42. Second electrode area; 5. Copper clip; 6. Aluminum connector; 7. Solder; 8. Package housing. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention.

[0022] Reference Figure 1 This utility model provides a copper-aluminum hybrid interconnect package structure for automotive-grade discrete devices, comprising: A leadframe, comprising a first leadframe 1, a second leadframe 2, and a third leadframe 3 that are electrically isolated from each other; Chip 4 is fixed to the first lead frame 1; Copper clip 5, the first end face B of the copper clip 5 is fixed to the first electrode area 41 of the chip 4, and the second end face C is fixed to the second lead frame 2; An aluminum connector 6, the first end of which is connected to the second electrode region 42 of the chip 4, and the second end of which is connected to the third lead frame 3.

[0023] Specifically, in this embodiment of the invention, in order to address the problems of high parasitic inductance, high resistance, and insufficient heat dissipation capacity of traditional aluminum wire bonding under high frequency and high current, a large-area, low-arc copper clip 5 is used as the main current path, and an aluminum connector 6 is used to complete the auxiliary connection. This avoids the conductivity and heat dissipation bottleneck of pure aluminum interconnect and the welding compatibility problem of pure copper interconnect chip 4, and achieves a significant reduction in parasitic inductance, a significant improvement in current carrying capacity and heat dissipation efficiency, while ensuring the long-term reliability of the packaging structure.

[0024] Specifically, the flat structure of the copper clip 5 increases the conductive cross-sectional area and shortens the current path, while its excellent electrical and thermal conductivity directly optimizes electrical performance and thermal management. The aluminum connector 6 utilizes the good matching of the thermal expansion coefficients of aluminum and chip 4, as well as mature bonding technology, to ensure the mechanical stability of the connection interface. This synergistic design of copper and aluminum hybrids comprehensively improves the overall performance of the interconnect structure while controlling costs.

[0025] In a preferred embodiment of the present invention, the first electrode region 41 of the chip 4 is the source or emitter main current channel, and the second electrode region 42 is the gate or gate signal channel.

[0026] Specifically, in this embodiment of the invention, for the source or emitter, which carries high current and easily generates a large amount of Joule heat, a copper clip 5 with low resistance and high thermal conductivity is used for connection. Its large cross-sectional area can significantly reduce the path resistance and parasitic inductance, while efficiently dissipating the core heat of the chip 4 to the lead frame, overcoming the performance bottleneck of traditional aluminum wires in power circuits. For the gate and Kelvin source, which have low current but are extremely sensitive to control signals, the mature and reliable aluminum wire bonding technology is used. This not only avoids the reliability risks caused by intermetallic compounds (IMC) that may be generated by direct bonding of copper to the gate aluminum pad, but also makes full use of the advantages of low cost and high flexibility of aluminum bonding process.

[0027] More specifically, in this embodiment of the present invention, chip 4 is a SiC chip, whose operating frequency and current density are much higher than those of traditional silicon-based devices, which places more stringent requirements on interconnect performance; the first electrode region 41 is a source aluminum pad, which achieves a firm mechanical connection and excellent electrothermal conduction with the copper clip 5; the second electrode region 42 is a gate or gate pad, which is bonded to the third lead frame 3 by one or more thin aluminum wires, ensuring the integrity of the drive signal and effectively suppressing gate oscillation caused by parasitic parameters.

[0028] In a preferred embodiment of the present invention, the first lead frame 1 has an integrally formed heat dissipation area 11 and a chip soldering area 12. The chip 4 is fixed to the chip soldering area 12 by solder 7.

[0029] Specifically, in the embodiments of this utility model, reference is made to Figure 1 The first lead frame 1 adopts an integral molding structure, and its chip soldering area 12 provides stable mechanical support and electrical grounding for the chip 4, while the large exposed heat dissipation area 11 (such as...) Figure 5 The heat generated by chip 4 during operation (as shown in the diagram) serves as the main heat dissipation path, efficiently dissipating the heat generated by chip 4 to the external environment or heat sink.

[0030] More specifically, in the embodiments of this utility model, referring to Figure 2 Region A shows a close-up of the microscopic morphology of the solder joints of chip 4. Solder 7 is applied to the chip soldering region 12, and the SiC chip 4 is soldered to the chip soldering region 12 using reflow soldering technology. The solder 7 used is a sintered silver paste with high thermal conductivity or a tin-silver-copper lead-free solder. This solder layer not only achieves a firm electrical interconnection between chip 4 and the first lead frame 1, but also forms an efficient heat conduction channel from chip 4 to the heat dissipation region 11, significantly reducing the thermal resistance of the lead frame.

[0031] In a preferred embodiment of the present invention, the first end face B of the copper clip 5 is fixed to the first electrode region 41 of the chip 4 by a sintered connecting layer, and the second end face C of the copper clip 5 is fixed to the pin bonding area of ​​the second lead frame 2 by solder 7.

[0032] Specifically, in the embodiments of this utility model, reference is made to Figure 3 and Figure 4 The copper clip 5 consists of three parts: a first end face B, which serves as a chip connection part and achieves large-area surface contact with the first electrode area 41 of the chip 4 through a sintered connection layer; a second end face C, which serves as a frame connection part and is fixed to the pin bonding area of ​​the second lead frame 2 by solder 7; and a connecting bridge part D, which serves as a conductive and structural bridge between the first end face B and the second end face C.

[0033] During assembly, the first electrode area 41 is a source aluminum pad. Solder 7 is applied to this source aluminum pad area. By precisely controlling the reflow soldering process parameters, the chip connection part (first end face B) of the copper clip 5 and the source aluminum pad form a metallurgical bond with low void ratio and high reliability. At the same time, solder 7 is applied to the welding area of ​​the second lead frame 2. The frame connection part (second end face C) of the copper clip 5 is firmly welded to the second lead frame 2 by the same reflow soldering process.

[0034] This double-ended welding structure together creates a low-resistance, low-inductance main power path from inside chip 4, through copper clip 5, to the external circuit, significantly improving current carrying capacity and heat dissipation efficiency.

[0035] Furthermore, considering the material compatibility challenges of directly bonding the copper clip 5 to the aluminum pad on the surface of the chip 4, the aluminum and copper interface is prone to forming brittle intermetallic compounds at high temperatures, affecting its reliability. In this embodiment of the invention, a compound is deposited on the surface of the chip 4 to improve the contact between the two materials. Specifically, metallization treatment is performed on the surface of the first electrode region 41 of the chip 4, for example, by sequentially depositing nickel / palladium / gold or nickel / gold layers.

[0036] This coating structure serves two purposes: firstly, it acts as a diffusion barrier layer, effectively suppressing the formation and growth of brittle intermetallic compounds between copper and aluminum during high-temperature processes and subsequent service; secondly, it provides an excellent solderable surface, ensuring that the sintered bonding layer or solder 7 can form a strong and stable interface connection with the chip surface, thereby guaranteeing the long-term reliability of the interconnect structure under harsh automotive-grade conditions.

[0037] In a preferred embodiment of the present invention, the pin bonding area extends in a direction away from the chip 4 to form a plurality of side-by-side main power pins 21.

[0038] Specifically, in the embodiments of this utility model, reference is made to Figure 1 The pin bonding area of ​​the second lead frame 2 extends outward to form multiple parallel main power pins 21. This structural design effectively increases the cross-sectional area of ​​the current output terminal, further reduces the overall resistance and parasitic inductance of the path, and provides a larger soldering area and heat dissipation path, which is beneficial to improving the power handling capability and thermal reliability of the package module, and facilitates soldering and heat dissipation management on the PCB board.

[0039] In a preferred embodiment of the present invention, the first end face B of the copper clip 5 is provided with a groove that is adapted to the surface structure of the chip 4.

[0040] Specifically, since power chips (such as SiC MOSFETs) typically have steps or trench structures on their surfaces for gate lead-out or inter-electrode isolation, to ensure that the copper clip 5 can form an effective and reliable large-area contact with the source aluminum pad, while avoiding electrical short circuits or mechanical damage to adjacent gate regions, in this embodiment of the invention, referring to... Figure 4 A groove structure is provided in the middle of the first end face B of the copper clip 5. This groove precisely avoids non-source areas (such as gate contact points or termination structures) on the surface of the chip 4, allowing the flat contact surface of the copper clip 5 to fully conform to the source aluminum pad. This design not only ensures the contact quality and mechanical stability of the main current channel, but also effectively prevents chip stress or potential short-circuit risks caused by assembly interference, improving interconnect accuracy and packaging yield.

[0041] In a preferred embodiment of this utility model, the thickness of the copper clip 5 is 0.2 mm to 0.4 mm.

[0042] Specifically, in this embodiment of the invention, based on factors such as current carrying capacity, thermal management requirements, mechanical strength, and packaging space limitations of conventional power devices, the thickness of the copper clip 5 is set to 0.2mm to 0.4mm. This thickness range ensures that the copper clip 5 has sufficient conductive cross-sectional area to maintain low on-resistance when carrying large currents, while also possessing good structural rigidity to support itself and maintain morphological stability during the manufacturing process, avoiding a decrease in connection reliability due to deformation.

[0043] Specifically, the dimensions (including thickness, width, and length) of the copper clip 5 are not fixed, but can be customized and adjusted according to the specific chip size, current rating, heat dissipation requirements, and packaging form. For higher power or higher performance applications, the copper clip thickness can be increased to 0.4mm or more to further improve its current carrying capacity and heat dissipation performance; conversely, for cost-sensitive or space-constrained applications, the dimensions can be appropriately optimized.

[0044] This flexible design strategy enables the structure to precisely adapt to a wide range of needs, from conventional industrial-grade to automotive-grade high-performance devices, achieving the best balance between electrical performance, thermal reliability, and manufacturing cost.

[0045] In a preferred embodiment of the present invention, the second end of the aluminum connector 6 is connected to the pin bonding area of ​​the third lead frame 3; The pin bonding area extends in a direction away from the chip 4 to form signal pins 31.

[0046] Specifically, in the embodiments of this utility model, reference is made to Figure 1 One end of the aluminum connector 6 is bonded to the second electrode region 42 of the chip 4, i.e., the gate or Kelvin source, and the other end is bonded to the pin bonding area on the third lead frame 3. This area extends outward to form an independent signal pin 31. This structure achieves complete isolation between the control signal and the main power current in the physical path and on the external pins, effectively avoiding interference from the power circuit to the sensitive gate signal and ensuring the integrity and stability of the drive signal.

[0047] Furthermore, the aluminum connector 6 preferably uses aluminum wire with a diameter of approximately 5 mil (0.127 mm), and the connection is achieved through a mature ultrasonic bonding process. This connection method fully utilizes the natural compatibility between the aluminum wire and the aluminum pad material on the chip surface, eliminating the need for additional metallization layer treatment. This not only simplifies the process and reduces costs, but also fundamentally avoids the risk of brittle intermetallic compounds (IMCs) that may arise at the copper-aluminum interface in the signal channel, greatly improving the reliability of the gate interconnect interface under long-term thermal cycling.

[0048] For gates and Kelvin sources that carry weak signals, aluminum wire bonding provides optimal process gentleness, connection reliability, and cost-effectiveness while meeting their current transport requirements.

[0049] As a preferred embodiment of the present invention, it further includes a packaging housing 8, which covers the top of the first lead frame 1, the second lead frame 2 and the third lead frame 3, and the heat dissipation area 11 of the first lead frame 1, the main power pin 21 of the second lead frame 2 and the signal pin 31 of the third lead frame 3 are all exposed outside the packaging housing 8.

[0050] Specifically, in the embodiments of this utility model, reference is made to Figure 5 The encapsulation housing 8 is preferably integrally formed using a high-performance epoxy molding compound through a transfer molding process, providing mechanical protection and electrical insulation for key components such as the internal chip 4, copper clip 5, and aluminum connector 6.

[0051] The heat dissipation area 11 of the first lead frame 1 is exposed on the back of the package housing 8, forming the main heat dissipation path of the device, which facilitates the direct mounting of external heat sinks and greatly improves the heat dissipation efficiency of the module. The main power pin 21 of the second lead frame 2 and the signal pin 31 of the third lead frame 3 are led out from the side of the package housing 8 and exposed, forming a well-structured and well-organized external electrical connection port.

[0052] This pin layout not only facilitates soldering and routing on the PCB, but also effectively separates power flow from signal flow, reducing mutual electrical interference and ensuring the stability of the device in complex electromagnetic environments. This package structure achieves a compact layout while also ensuring efficient heat dissipation, convenient assembly, and high reliability, fully meeting the stringent requirements of automotive-grade power modules.

[0053] In summary, this utility model provides a copper-aluminum hybrid interconnect packaging structure for automotive-grade discrete devices. By using copper clips 5 in the first electrode region 41 to achieve high-current, low-inductance main power interconnection, and using aluminum wire bonding in the second electrode region 42 to achieve low-cost, high-reliability signal connection, combined with the synergistic design of an integrated lead frame and optimized packaging, the current carrying capacity, heat dissipation efficiency, switching characteristics, and long-term reliability of the packaged module are successfully improved while controlling manufacturing costs. This provides an advanced packaging solution for the development of a new generation of high-efficiency, high-power-density automotive-grade power devices.

[0054] The above description is only a preferred embodiment of the present utility model and does not limit the implementation method and protection scope of the present utility model. Those skilled in the art should realize that all solutions obtained by equivalent substitutions and obvious changes made based on the description and illustrations of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A copper-aluminum hybrid interconnect packaging structure for automotive-grade discrete devices, characterized in that, include: The lead frame includes a first lead frame (1), a second lead frame (2), and a third lead frame (3) that are electrically isolated from each other. The chip (4) is fixed on the first lead frame (1); A copper clip (5) is fixed at its first end face (B) to the first electrode region (41) of the chip (4) and at its second end face (C) to the second lead frame (2). An aluminum connector (6) is provided, with its first end connected to the second electrode region (42) of the chip (4) and its second end connected to the third lead frame (3).

2. The copper-aluminum hybrid interconnect packaging structure for automotive-grade discrete devices according to claim 1, characterized in that, The first electrode region (41) of the chip (4) is the source or emitter main current channel, and the second electrode region (42) is the gate or gate signal channel.

3. The copper-aluminum hybrid interconnect packaging structure for automotive-grade discrete devices according to claim 1, characterized in that, The first lead frame (1) has an integrally formed heat dissipation area (11) and a chip bonding area (12). The chip (4) is fixed to the chip soldering area (12) by solder (7).

4. The copper-aluminum hybrid interconnect packaging structure for automotive-grade discrete devices according to claim 1, characterized in that, The first end face (B) of the copper clip (5) is fixed to the first electrode area (41) of the chip (4) by a sintered bonding layer, and the second end face (C) of the copper clip (5) is fixed to the pin bonding area of ​​the second lead frame (2) by solder (7).

5. A copper-aluminum hybrid interconnect packaging structure for automotive-grade discrete devices according to claim 4, characterized in that, The pin bonding area extends in a direction away from the chip (4) to form multiple side-by-side main power pins (21).

6. The copper-aluminum hybrid interconnect packaging structure for automotive-grade discrete devices according to claim 1, characterized in that, The second end of the aluminum connector (6) is connected to the pin bonding area of ​​the third lead frame (3); The pin bonding area extends in a direction away from the chip (4) to form a signal pin (31).

7. A copper-aluminum hybrid interconnect packaging structure for automotive-grade discrete devices according to claim 2, characterized in that, It also includes a package housing (8), which covers the top of the first lead frame (1), the second lead frame (2) and the third lead frame (3), and the heat dissipation area (11) of the first lead frame (1), the main power pin (21) of the second lead frame (2) and the signal pin (31) of the third lead frame (3) are exposed to the package housing (8).

8. A copper-aluminum hybrid interconnect packaging structure for automotive-grade discrete devices according to claim 1, characterized in that, The first end face (B) of the copper clip (5) is provided with a groove that is adapted to the surface structure of the chip (4).

9. A copper-aluminum hybrid interconnect packaging structure for automotive-grade discrete devices according to claim 1, characterized in that, The thickness of the copper clip (5) is 0.2 mm to 0.4 mm.

10. A copper-aluminum hybrid interconnect packaging structure for automotive-grade discrete devices according to claim 1, characterized in that, The aluminum connector (6) is an aluminum wire with a diameter of 5 mil.

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