Lead electrode, lead frame and packaging structure thereof

Abstract

The utility model provides a lead electrode, a lead frame and a packaging structure thereof, the lead electrode comprises a plurality of integrally formed pins, the upper section and the lower section of any pin are parallel to each other, and the widths of the lower sections of any two pins are consistent; the lower sections of the pins are in bonding connection with the DBC board; the upper sections of the pins are used for connecting a lead frame or an external circuit. According to the utility model, the bonding between the lead electrode and the DBC board in the prior art is solved. The efficiency is low; and the bonding quality is not high. By optimizing the size design of the electrode, the lead electrode and the DBC board can be bonded by using unified bonding parameters in the bonding process, and the stability and durability of a product are remarkably improved.

Description

Technical Field

[0001] The utility model relates to the field of semiconductor device packaging, in particular to a lead electrode, a lead frame and a packaging structure thereof. Background Art

[0002] In the field of semiconductor device packaging, the lead frame is a key component that connects the chip to the external circuitry. Its structural design has a significant impact on product quality, production efficiency, and product variety. Current lead frames often feature lead electrodes of varying widths, depending on product requirements, such as the size of the external PCB board's application connection terminals and specific electrode requirements.

[0003] refer to Figure 1 To facilitate the subsequent rib cutting process, the lead structure of existing lead electrodes is typically narrowed from the lower end of the lead (bonding end of the DBC board) to the flat plated end of the lead frame, where it connects to the rib, while the rest of the lead structure remains the same width as the upper end of the lead. Therefore, during the bonding process with the DBC board, the uneven force applied to the bonding end of the lead electrode due to the different widths of the lead, may cause the bonded lead to fall off or a weak bond. Alternatively, it may cause uneven stress distribution on the lead frame when subjected to force, causing the electrode to bend or deform, affecting the stability of the electrical connection.

[0004] In addition, during the bonding process between the lead electrode pins and the DBC board (direct bonding copper), the bonding parameters need to be adjusted for electrode pins of different sizes, which not only reduces the bonding efficiency but may also affect the bonding quality; especially for narrower electrode pins, due to the smaller contact area with the DBC board, the bonding reliability is also relatively poor.

[0005] In order to solve the above technical problems, the utility model proposes a lead electrode, a lead frame and a packaging structure thereof. Utility Model Content

[0006] In response to the deficiencies in the prior art, the utility model provides a lead electrode, a lead frame and a packaging structure thereof, which can provide sufficient electrode bonding area when packaging the device, thereby solving the problems of low bonding efficiency and poor bonding quality between the lead electrode and the DBC board in the prior art.

[0007] In the first aspect, an embodiment of the present invention provides a lead electrode, characterized in that it comprises a plurality of pins, the pins adopting an integrally formed structure, the upper section and the lower section of any pin are parallel to each other, the width of the lower sections of different pins are consistent and not less than 2 mm, so as to facilitate bonding connection with the DBC board; the upper section of the pin is used to connect to the lead frame or external circuit.

[0008] Preferably, the upper section and the lower section of the pin are connected via a connecting section, and the connecting section has the same width as the upper section of the corresponding connected pin.

[0009] Preferably, the contact surface between the lower section of the pin and the DBC board is square, and the width of the upper section of the pin is adaptively selected according to specific circumstances, and the width of the upper section is not less than 1 mm.

[0010] Preferably, the pins include Z-shaped pins or S-shaped pins.

[0011] In a second aspect, an embodiment of the present invention further provides a lead frame, comprising: the lead electrode according to any one of the above technical solutions, further comprising:

[0012] Frame body,

[0013] a plurality of lead frame units, wherein the plurality of lead frame units are distributed on the frame body in a rectangular array;

[0014] reinforcing ribs for securing adjacent lead frame units to the frame body;

[0015] The lead frame unit includes connecting ribs and a plurality of lead electrodes.

[0016] The plurality of lead electrodes are arranged in sequence and relatively connected to the lead frame unit via connecting ribs.

[0017] Preferably, outer surfaces of the plurality of lead frame units, reinforcing ribs and lead electrodes are all plated with a tin layer.

[0018] In a third aspect, an embodiment of the present utility model further provides a packaging structure, comprising a lead electrode as described in any one of the above technical solutions, and further comprising a DBC board;

[0019] The outer surface of the DBC board is plated with a plurality of copper cladding layers arranged in blocks;

[0020] The edge of the copper clad layer block is provided with a fixed bubble point;

[0021] A number of chips are mounted on the power working area of ​​the copper clad layer block, and aluminum wires are bonded between the copper clad layer block and each chip to form an electrical connection between the DBC board and the chip;

[0022] The copper clad layer block is also bonded to the lower section of any pin in the lead electrode to form a packaging structure.

[0023] Preferably, the lower section of any pin is bonded to the middle position of any copper clad layer block, and the middle position is a fixed distance of 0.5mm to 1mm between the two side edges of the lower section of the pin and the edge of the copper clad layer block.

[0024] Preferably, the width of the copper clad layer block is 3 mm to 3.4 mm, and the thickness of the copper clad layer block is not less than 0.38 mm.

[0025] Preferably, the chip includes one or more of an IGBT chip, an FRD chip, a MOSFET chip and an NTC chip.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] By redesigning the pin structure of the lead electrode, sufficient bonding area can be provided for the connection end of the electrode pin and the DBC board, while improving the bonding efficiency and quality of the packaged device. Specifically, the dimensions of the bonding end of the electrode pin and the DBC board are standardized, and the width and area of ​​the electrode pin are unified, so that unified bonding parameters can be applied during the bonding process of the device package, thereby simplifying the operation process. The pull-out force after bonding can meet strict design requirements and application conditions, effectively avoiding electrode loosening and virtual pressure phenomena, significantly improving the stability and durability of the product, and solving the problems of low bonding efficiency and low bonding quality during device packaging in the existing technology.

[0028] In addition, this solution can achieve efficient and consistent welding results by optimizing the size design of the lead electrodes and simplifying the bonding process without changing the size of the lead frame, thereby improving production efficiency while ensuring high product quality standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the structure of the existing lead electrode in the background technology of this utility model;

[0030] Figure 2 A schematic structural diagram of a lead electrode provided by the utility model;

[0031] Figure 3 A schematic diagram of the three-dimensional structure of a lead electrode provided by the utility model;

[0032] Figure 4 A schematic diagram of the planar structure of a lead electrode provided by the utility model;

[0033] Figure 5 A schematic structural diagram of a lead frame provided by the utility model;

[0034] Figure 6 This is a structural schematic diagram of a lead frame provided by the utility model.

[0035] In the above figures: 1. Upper section of the pin; 2. Lower section of the pin; 3. Connecting section; 4. Lead frame; 5. Frame body; 6. Lead frame unit; 7. Reinforcement ribs; 8. Connecting ribs; 9. Lead electrodes; 10. DBC board; 11. Copper cladding area; 12. Chip; 13. Aluminum wire; 14. Package structure; 15. Bubble point; 16. Power working area. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0037] refer to Figure 1 During the current manufacturing process of the lead frame 4, its structural dimensions are designed based on the specifications of the lead electrodes 9. The prepared lead frame 4 is then bonded to the DBC board 10 via the lead electrodes 9 to form a complete device package. The width of the lead electrodes 9 varies depending on the product requirements, adapting to the dimensions of the circuit board's connection terminals or meeting specific electrode requirements. This can result in uneven distribution of the lead electrodes 9 on the lead frame 4, impacting the overall performance and stability of the device.

[0038] At the same time, to facilitate rib cutting, the lower section 2 of the existing lead (the end that bonds to the DBC board) is narrowed only where it connects to the connecting rib 8, from the flat plated end of the lead frame 4. The rest of the lead structure remains the same width as the upper section 1 of the lead. This design requires different bonding parameters for different electrode lead sizes when bonding the lead electrode 9 to the DBC board 10 (direct bond copper). This not only affects bonding efficiency and effectiveness, but also reduces bonding reliability, especially for the smaller lower section 2 of the lead, due to its relatively small contact area with the DBC board.

[0039] Therefore, the embodiment of the present application provides a lead electrode, a lead frame and its packaging structure, and redesigns the size of the lead electrode 9, so that during the device packaging process, sufficient bonding area can be provided for the connection between the electrode pin and the DBC board, while also improving the bonding efficiency and quality.

[0040] In order to make the purpose, technical solutions and effects of the present disclosure more clear and explicit, the present disclosure is further described in detail below with reference to the accompanying drawings and in combination with preferred embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and are not intended to limit the scope of protection of the present disclosure.

[0041] Example 1

[0042] like Figure 2As shown, the present invention provides a lead electrode comprising several pins. These pins are integrally formed, with the upper section 1 and lower section 2 of each pin parallel to each other. The width of the lower sections 2 of different pins is consistent and not less than 2 mm, facilitating bonding with a DBC board. The upper section 1 of the pin is used to connect to a lead frame or external circuitry.

[0043] In this embodiment, the leads are integrally formed, and the upper segment 1 and lower segment 2 of each lead are parallel to each other. The lower segments 2 of any two leads have the same width. During the bonding process between the lead electrode 9 and the DBC (direct bonded copper) plate, a bonding machine is used to bond the lead electrode 9 to the DBC plate, so that the lead electrode 9 and the DBC plate form a eutectic surface, achieving a welding effect.

[0044] like Figure 3 As shown, Figure 3 The diagram is a three-dimensional structure diagram of a lead electrode provided by the present invention, wherein the upper section 1 and the lower section 2 of the lead are connected via a connecting section 3, and the connecting section 3 has the same width as the upper section 1 of the corresponding connected lead.

[0045] Specifically, the upper and lower segments 1 and 2 of the lead are connected via a connecting segment 3, and the width of the connecting segment 3 matches the width of the corresponding upper segment 1 of the lead. Furthermore, because the DBC board is not coplanar with the lead frame or external circuitry, the lead of the lead electrode 9 needs to be bent three-dimensionally to achieve electrical connection.

[0046] like Figure 4 As shown, Figure 4 This is a schematic diagram of the planar structure of a lead electrode provided by the utility model.

[0047] In some embodiments, the contact surface between the lower section 2 of the pin and the DBC board is square, and the width of the upper section 1 of the pin is adaptively selected according to specific circumstances, and the width of the upper section 1 is not less than 1 mm.

[0048] Specifically, the width of the lower portion 2 of the pin is designed to range from 2mm to 2.2mm. The width of the upper portion 1 of the pin is determined based on the size of the external circuit's application connection terminal. Specifically, the width of the lower portion 2 of the pin can be designed to be 2mm to 2.2mm wide, suitable for external circuit connection terminals with matching widths; or the width of the lower portion 2 of the pin can be designed to be 1mm to 1.2mm narrow, suitable for narrower external circuit connection terminals.

[0049] It should be noted that in the current bonding process for electrode pins, the bonding force required for pins of different sizes varies. This results in frequent adjustments to the bonding force during bonding machine operation, reducing efficiency. Furthermore, pins of varying widths can lead to unstable bonding, especially narrower electrode pins, which can fall off or experience loose bonds when bonding to the DBC board.

[0050] Therefore, a lead electrode proposed in this embodiment is adopted, wherein the width of the lower sections 2 of any two pins of the lead electrode 9 is consistent. By unifying the width of the lower sections 2 of the pins bonded to the DBC board 10, and keeping the width of the connecting section 3 consistent with the upper section 1 of the corresponding connected pin, the overall size of the original lead frame 4 can be kept unchanged, that is, the size of the bonding pins is optimized without changing the frame size. It is achieved that during the bonding process, technicians can use the same bonding parameters to bond the lead electrode 9 and the DBC board 10, thereby improving the efficiency and quality of the bonding. By adopting the technical solution of this embodiment, the pull-out force of the bonding end after bonding can meet the design requirements and application conditions, and the lead electrode 9 will not be loose or under pressure, which solves the problem of low efficiency and low quality of the bonding process due to uneven force on the pins due to different pin specifications.

[0051] Example 2

[0052] refer to Figure 5 The present invention also provides a lead frame, comprising:

[0053] Frame body 5,

[0054] a plurality of lead frame units 6 , wherein the plurality of lead frame units 6 are distributed on the frame body 5 in a rectangular array;

[0055] reinforcing ribs 7 for fixing adjacent lead frame units 6 to the frame body 5;

[0056] The lead frame unit 6 includes a connecting rib 8 and a plurality of lead electrodes 9.

[0057] The plurality of lead electrodes 9 are arranged in sequence and relatively connected to the lead frame unit 6 via connecting ribs 8 .

[0058] The frame body 5 provides support for the entire structure. At the same time, several lead frame units 6 are distributed on the frame body 5 in the form of a rectangular array. Adjacent lead frame units 6 are fixed to the frame body 5 by reinforcing ribs 7 to enhance the stability and structural strength of the entire frame. Connecting ribs 8 connect several lead electrodes 9 to the lead frame units 6 to increase structural strength, making it less likely for the electrodes to tilt and deform, thereby improving the consistency and flatness of the electrodes after bonding.

[0059] In practice, several lead electrodes 9 on the lead frame 4 are bonded to the DBC board. The bonded lead frame 4 is then subjected to rib cutting, retaining the electrode structure on the lead frame 4 while removing other components from the lead frame 4. This ultimately results in several structurally complete package units. Furthermore, the number of lead frame units 6, ribs 7, and lead electrodes 9 provided on the lead frame 4 can be determined based on actual needs and is not limited in this embodiment.

[0060] In some embodiments, the outer surfaces of the lead frame units 6, the reinforcing ribs 7, and the lead electrodes 9 are all plated with a tin layer. The tin plating on the outer surface can prevent the lead electrodes 9 from being oxidized and improve the solderability of the product.

[0061] Example 3

[0062] like Figure 6 As shown, an embodiment of the present invention further provides a packaging structure, including a lead electrode 9 as described in any one of the above technical solutions, and also including a DBC board 10; the outer surface of the DBC board 10 is plated with a copper clad layer arranged in a plurality of block blocks; a plurality of chips 12 are mounted on the copper clad layer block 11, and aluminum wires 13 are bonded between the copper clad layer block 11 and each chip 12 to form an electrical connection between the DBC board 10 and the chip 12; the copper clad layer block 11 is also bonded to the lower section 2 of any pin in the lead electrode 9 to form a packaging structure 14.

[0063] The lower section 2 of any pin is bonded to the middle position of any copper clad layer block 11 , and the middle position is a fixed distance of 0.5mm to 1mm between the two side edges of the lower section 2 of the pin and the edge of the copper clad layer block 11 .

[0064] The width of the copper clad layer block 11 is 3 mm to 3.4 mm, and the thickness of the copper clad layer block 11 is not less than 0.38 mm.

[0065] In the current bonding process between lead electrodes 9 and DBC board 10, the narrow lead electrodes 9 lead pullout force after bonding fails to meet design requirements and application conditions, resulting in loose electrodes and false pressure. However, this technical solution not only standardizes the width of the electrode lead bonding surface, enabling uniform bonding parameters to be applied during the bonding process to address low bonding efficiency, but also further optimizes the area and distribution of the copper cladding layer on the DBC board 10.

[0066] Specifically, the copper clad layer of the DBC board 10 is divided into blocks, and the width of each copper clad layer block 11 is set to 3 mm to 3.4 mm, so that the improved DBC board 10 matches the lead electrode 9, ensuring that the bonded electrode is located in the middle position of the copper clad layer block 11, while leaving appropriate margins on both sides of the electrode.

[0067] Specifically, since the width of the lower section 2 of the pin bonded to the copper clad layer of the DBC board 10 is 2mm to 2.2mm, the technician fixes the lower section 2 of the pin in the middle position of the copper clad layer block 11 during bonding, and controls the distance between the two side edges of the lower section of the pin and the edge of the copper clad layer block 11 to be maintained at 0.5mm to 1mm. Then, a bonding machine is used to apply pressure to the bonding interface between the lower section 2 of the pin and the DBC board 10 to achieve diffusion bonding and establish a stable connection. The entire bonding process takes only a few milliseconds. In this way, not only the eutectic bonding area between the lead electrode 9 and the DBC board 10 is increased, but also the bonding strength is enhanced, ensuring that the pull-out force after bonding meets the design requirements and application conditions, effectively avoiding the problems of loose electrodes and virtual pressure, significantly improving the quality and efficiency of the bonding between the lead electrode 9 and the DBC board 10, and ensuring the accuracy and reliability of the bonding.

[0068] In some embodiments, the chip 12 is provided as a single chip or a combination chip, wherein the combination chip is an IGBT chip and an FRD chip arranged in parallel, and the single chip can be a silicon-based MOSFET chip or a SiC MOSFET chip. Furthermore, the package structure can also include an NTC thermistor according to the actual power level. The chip 12 is provided in the power operating area 16 of the copper-clad layer block 11 of the DBC board. Simultaneously, the edge of the copper-clad layer block 11 can be provided with a bubble point 15 according to the actual product conditions to prevent the DBC board 10 from cracking due to high ultrasonic bonding energy or thermal stress during pin bonding and chip soldering, further improving product production yield.

[0069] During the specific implementation process, an automatic placement machine can be used to mount one or more IGBT chips, FRD chips, MOSFET chips and SiCMOSFET chips on the copper-clad layer block 11 of the DBC board 10, and aluminum wires 13 are bonded between the copper-clad layer block 11 and each chip to form an electrical connection between the DBC board 10 and the chip 12. The bonding of the aluminum wire 13 provides good electrical conductivity, ensuring that the current and signals between the chip 12 and the DBC board 10 can be effectively transmitted. The connection points between the aluminum wire 13 and the DBC board 10 and the chip 12 have high mechanical strength and can withstand subsequent packaging processes and thermal cycle tests during use, providing a stable and reliable foundation for the subsequent bonding process and ensuring the performance of the entire packaging structure 14.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model and are not limiting. Although the utility model is described in detail with reference to the preferred embodiments, ordinary technicians in this field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the utility model, which should be included in the scope of the claims of the utility model.

Claims

1. A lead electrode, characterized in that: It includes several pins, which adopt an integrally formed structure. The upper and lower sections of any pin are parallel to each other, and the width of the lower sections of different pins is consistent and not less than 2mm, so as to facilitate bonding with the DBC board; the upper section of the pin is used to connect to the lead frame or external circuit; The upper section and the lower section of the pin are connected via a connecting section, and the connecting section has the same width as the upper section of the corresponding connected pin.

2. A lead electrode according to claim 1, characterized in that: The contact surface between the lower section of the pin and the DBC board is square, and the width of the upper section of the pin is adaptively selected according to specific circumstances, and the width of the upper section is not less than 1 mm.

3. A lead electrode according to any one of claims 1 to 2, characterized in that: The pins include Z-shaped pins or S-shaped pins.

4. A lead frame, characterized in that: comprising the lead electrode according to any one of claims 1 to 3, further comprising Frame body, a plurality of lead frame units, wherein the plurality of lead frame units are distributed on the frame body in a rectangular array; reinforcing ribs for securing adjacent lead frame units to the frame body; The lead frame unit includes connecting ribs; Several pins in the lead electrode are arranged in sequence and relatively connected to the lead frame unit through connecting ribs.

5. The lead frame according to claim 4, wherein: The outer surfaces of the lead frame units, the reinforcing ribs and the lead electrodes are all plated with a tin layer.

6. A packaging structure, characterized in that: A lead frame according to claim 4 or 5, further comprising a DBC board; The outer surface of the DBC board is provided with a plurality of copper clad blocks arranged in blocks; The edge of the copper clad layer block is provided with a fixed bubble point; A number of chips are mounted on the power working area of ​​the copper clad layer block, and aluminum wires are bonded between the copper clad layer block and each chip to form an electrical connection between the DBC board and the chip; The copper clad layer block is also bonded to the lower section of any pin of the lead electrode.

7. The packaging structure according to claim 6, characterized in that: The lower section of any pin is bonded to the middle position of any copper clad layer block, and the middle position is a fixed distance of 0.5mm to 1mm between the two side edges of the lower section of the pin and the edge of the copper clad layer block.

8. The packaging structure according to claim 6, wherein: The width of the copper clad layer block is 3 mm to 3.4 mm, and the thickness of the copper clad layer block is not less than 0.38 mm.

9. The packaging structure according to claim 6, wherein: The chip includes a single chip or a combination chip; wherein the single chip is configured by a MOSFET chip, and the combination chip is configured by connecting an IGBT chip and an FRD chip in parallel.

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