Seagull-foot double-chip laminated packaging method

Abstract

The invention discloses a sea gull foot double-chip laminated packaging method, which comprises the following steps of: respectively forming a flat-head bonding pad and a convex-point bonding pad through a bottom lead and an upper lead, sequentially stacking a first core particle and a second core particle along a vertical direction, and completing up-and-down welding connection of the double core particles under the condition of controlled temperature and pressure. And putting the laminated and welded assembly into a mold pressing mold, and forming a packaging main body by adopting transfer molding, so that the electric connection of the lead and the core particle is fixed by a plastic packaging body. And after packaging is completed, axially flattening and bending the wire leads extending out of the two sides, and enabling the tail ends of the wire leads to form outward-extending sea gull foot welding sections which are used as surface mounting bonding pads. According to the invention, the pressure uniformity and the welding reliability of the laminated welding spots are improved through the vertical stacking structure of the flat-head welding pads, the convex spot welding pads and the core particles; through the flattening and bending process of the lead, the axial lead structure is compatible with the SMD installation, and the miniaturized SMD packaging suitable for the high-voltage-resistant diode is realized.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device packaging technology, specifically a seagull-foot dual-chip stacked packaging method. Background Technology

[0002] Among existing diode packaging forms, axially packaged devices are widely used in high-voltage products due to their simple structure and short heat dissipation path. However, axial devices are relatively large and not suitable for surface mount applications where mounting space is critical. On the other hand, surface mount packages such as SOD and SMB, while offering advantages such as miniaturization and reflow soldering assembly, have certain limitations in terms of increasing device voltage withstand and implementing chip series structures.

[0003] To improve voltage withstand capability, existing technologies often enhance electrical performance by increasing the area of ​​a single chip or by connecting chips in parallel / series. However, increasing the area of ​​a single chip leads to decreased wafer utilization and increased chip cost; while dual-chip series structures in existing surface mount packages typically require larger package space or complex lead frame structures, which is not conducive to maintaining the device's external dimensions. Furthermore, traditional surface mount package lead frames are mostly based on stamped sheets, limiting processing flexibility and making it difficult to simultaneously achieve standardized pad structures for chip stacking and external pins in small-size packages.

[0004] Furthermore, traditional surface mount packages typically lack the wire lead structure for axial devices, making it difficult to balance the advantages of axial leads, such as ease of fabrication and the ability to form diverse pad shapes like bumps and flat tops. In multi-chip series scenarios, existing SMD packages often require special pad steps, stepped metal supports, or multi-segment frame structures, leading to complex processes and increased packaging costs, making them unsuitable for low-cost mass production of high-voltage diodes. Therefore, designing a gull-feet dual-chip stacked package method is essential. Summary of the Invention

[0005] The purpose of this invention is to provide a seagull-foot dual-chip stacked packaging method to solve the problems mentioned in the background art.

[0006] To solve the above technical problems, the present invention provides the following technical solution: a seagull-foot dual-chip stacked packaging method, comprising the following steps: (1) providing bottom leads and top leads, flattening the front end of the bottom lead to form a flat pad, and arching the front end of the top lead to form a bump pad; (2) placing the first chip on the flat pad and setting solder in the contact area; (3) placing the second chip on the first chip, stacking the first chip and the second chip in a vertical direction; (4) pressing the bump pad downwards with a welding head, so that the bump pad and the top of the second chip are connected. The surface forms a welded connection under controlled temperature and pressure, and the first core particle is welded to the flat pad, thus forming a series conductive path of bottom lead-first core particle-second core particle-top lead; (5) the welded component is placed into the molding die, and the encapsulation body covering the stacked core particle and the welding area is formed by transfer molding, so that the non-welded parts of the bottom lead and the top lead extend outward from both sides of the encapsulation body; (6) the extended bottom lead and the top lead are axially flattened to form a flat section, and the flat section is bent to form an outwardly extending seagull foot welding section at its end.

[0007] According to the above technical solution, the flat-head pad is a rectangular flat structure, and its width and thickness are controlled by a preset size, which is used to support the lower surface of the first core chip.

[0008] According to the above technical solution, the bump pad is a slightly raised pressure arch structure, which is used to provide concentrated contact pressure to the second core during the crimping process.

[0009] According to the above technical solution, the transfer molding causes the packaging body to form a rectangular block-shaped solidified structure, and the interior forms a chip mounting cavity for accommodating the first chip, the second chip, and the lead bonding area.

[0010] According to the above technical solution, the bottom surface of the seagull-foot welding section provides a flat surface mount pad structure for mounting the packaged device onto the PCB circuit board surface.

[0011] According to the above technical solution, the bending process includes: bending the flat section downward to form a curved section, and further bending the end to form a horizontally extending mounting section, thereby constituting the seagull foot welding section.

[0012] Compared with existing technologies, the beneficial effects achieved by this invention are as follows: This invention, by setting up flat-head pads, bump pads, and a vertically stacked structure of the first and second core chips, enables the dual core chips to achieve a stable stress state during the welding process. The concentrated pressure provided by the bump pads ensures uniform pressure at the welding interface of the upper and lower core chips, thereby improving the consistency and withstand voltage performance of the stacked solder joints. The package body formed by transfer molding completely covers the stacked structure and welding area, ensuring the mechanical stability and electrical reliability of the core-lead connection. Furthermore, by flattening and bending the extended portions of the bottom and top leads, the ends of the flat sections form gull-foot welding sections, thereby achieving a surface mount structure without changing the traditional axial lead materials and processes, enabling the packaged device to be compatible with SMD surface mount technology. In summary, this invention simultaneously achieves a compact size, stable solder joint quality, and flexible mounting methods, and is particularly suitable for stacked packaging of high-voltage, miniaturized diodes. Attached Figure Description

[0013] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a cross-sectional view of a seagull-foot dual-chip stacked packaging method provided by the present invention; Figure 2 This is a schematic diagram of the overall structure of a seagull-foot dual-chip stacked packaging method provided by the present invention; Figure 3 This is a schematic diagram of the low, middle, bottom, and top lead structure of a dual-chip stacked packaging method for seagull feet provided by the present invention.

[0014] In the diagram: 1 Package body, 2 Bottom lead, 21 Flat pad, 3 Top lead, 31 Bump pad, 4 First chip, 5 Second chip, 6 Soldering segment. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] like Figures 1-3 As shown, a seagull-feet dual-chip stacked packaging method is described. The packaging structure of this embodiment mainly includes a packaging body 1, a bottom lead 2, an upper lead 3, a first chip 4, a second chip 5, and seagull-feet external soldering sections 6 located at both ends of the device.

[0017] The encapsulation body 1 is a molded and cured plastic encapsulation body with an overall rectangular block structure, used to encapsulate the dual-chip stacked structure and the soldering connection area. The central area inside the encapsulation body 1 forms a chip mounting cavity to accommodate the first chip 4 and the second chip 5 of the stacked structure. Figure 1 The two core chips are stacked one above the other, forming a double-core layer connection structure with the lead wire structure.

[0018] like Figure 3 As shown, the bottom lead 2 is made of metal wire, and its front end is flattened to form a flat-head pad 21. The flat-head pad 21 has a regular flat surface. The flat-head pad 21 is used to support the lower surface of the first core 4 and is the main welding support surface of the first core. The rest of the bottom lead 2 retains the wire shape and is used for subsequent forming operations.

[0019] The leading edge of the top lead 3 is formed into a bump pad 31 by end arching. This bump has a slightly raised shape and features concentrated pressure and a fixed contact surface. The bump pad 31 is used to press the second core 5 downward during the soldering process, forming a reliable soldering interface between its upper surface and the bump pad. The rest of the top lead 3 also maintains the wire shape.

[0020] During the chip assembly process, the bottom lead 2 and the top lead 3 are positioned by a fixture, so that the flat pad 21 and the bump pad 31 are respectively located below and above the chip stack. First, the first chip 4 is placed on the flat pad 21 of the bottom lead 2, and a preset solder is applied to the contact area. Then, the second chip 5 is placed above the first chip 4, so that the two chips are stacked vertically. Subsequently, a special welding head is used to press the bump pad 31 of the top lead 3 against the upper surface of the second chip 5 from top to bottom, and the welding of the dual-chip stack is completed under controlled temperature and pressure conditions. After welding, the first chip 4 is electrically connected to the flat pad 21 of the bottom lead 2, and the second chip 5 is electrically connected to the bump pad 31 of the top lead 3, thus forming a dual-chip series conduction path.

[0021] After the laminated structure is welded, the assembly consisting of the leads and dual-core chips is placed into a molding die. A transfer molding process is then used to form the encapsulation body 1, which covers the internal laminated structure and secures the electrical connection between the leads and the core chips. After encapsulation, the extended portions of the leads protrude from both sides of the encapsulation body, appearing as wires. Subsequently, a flattening die is used to axially flatten the extended portions of the leads, making them into flat segments of uniform width. Then, a bending die is used to bend the flat segments downwards to form curved segments, creating outward-extending horizontal planes at the ends, thus forming the gull-foot welding segment 6.

[0022] like Figure 2As shown, the bottom surface of the seagull-feet soldering section 6 forms a surface mount pad, which can be directly mounted on the PCB circuit board, realizing surface mount capability in a small-size package. The flattening and bending morphology of the entire lead is similar to... Figure 2 The three-dimensional shape is consistent, and the main body of the package 1 maintains a standard rectangular structure.

[0023] In summary, by employing a bottom lead flat-top pad 21, an upper lead bump pad 31, and a stacked first chip 4 and second chip 5, this invention enables the stacking and soldering of two chips based on axial leads. Subsequent processes such as flattening and bending then form a seagull-feet surface mount structure. This invention combines the voltage withstand advantage of stacking technology with the mounting advantage of surface mount packaging, achieving a small-scale SMD package suitable for high-voltage diodes.

[0024] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0025] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A sea gull foot dual-chip package-on-package method, characterized by, Includes the following steps: (1) Provide a bottom lead (2) and an upper lead (3), flatten the front end of the bottom lead (2) to form a flat pad (21), and arch the front end of the upper lead (3) to form a bump pad (31). (2) Place the first core (4) on the flat-top pad (21) and apply solder to the contact area; (3) Place the second core (4) on the first core (4) so ​​that the first core (4) and the second core (5) are stacked in a vertical direction; (4) The bump pad (31) is pressed down by the welding head, so that the bump pad (31) and the upper surface of the second core (5) are welded together under controlled temperature and pressure. At the same time, the first core (4) is welded to the flat pad (21), thus forming a series conductive path of bottom lead (2) - first core (4) - second core (5) - top lead (3); (5) The welded components are placed into a molding die and a package body (1) covering the stacked core and the welding area is formed by transfer molding, so that the non-welded parts of the bottom lead (2) and the top lead (3) extend outward from both sides of the package body (1); (6) The outward-extending bottom lead (2) and top lead (3) are axially flattened to form a flat section, and the flat section is bent so that its end forms an outward-extending gull-foot welding section (6).

2. The gull-wing dual-chip package method of claim 1, wherein: The flat pad (21) is a rectangular flat structure, and its width and thickness are controlled by a preset size. It is used to support the lower surface of the first core (4).

3. The gull-wing dual-chip package method of claim 1, wherein: The bump pad (31) is a slightly raised pressure arch structure used to provide concentrated contact pressure to the second core (5) during the crimping process.

4. The method of claim 1, wherein: Transfer molding causes the package body (1) to form a rectangular block solidified structure, with a chip mounting cavity inside for accommodating the first chip (4), the second chip (5), and the lead bonding area.

5. The seagull-foot dual-chip stacked packaging method according to claim 1, characterized in that: The bottom surface of the gull-foot solder section (6) provides a flat surface mount pad structure for mounting packaged devices onto the PCB board surface.

6. The seagull-foot dual-chip stacked packaging method according to claim 1, characterized in that: The bending process includes: bending the flat section downward to form a curved section, and further bending the end to form a horizontally extending mounting section, thereby forming the gull-foot welding section (6).

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