Lead frame and semiconductor packaging structure

Abstract

The utility model discloses a lead frame and a semiconductor packaging structure, and relates to the technical field of semiconductor packaging. The lead frame comprises a metal frame and a base island connected with the metal frame, the top surface of the base island is used for mounting a chip, the metal frame is provided with a pin assembly, the pin assembly comprises an inner pin and an outer pin which are stacked and connected with each other, the inner pin is connected with the metal frame, and the outer pin is connected with the metal frame. The outer pins protrude out of the bottom surfaces of the metal frame and the base island, the inner pins are used for being connected with the chip, and the outer pins are used for being connected with a circuit board. The lead frame can solve the problem that when an existing lead frame base island and a PCB bonding pad are welded, residual air between welding flux layers is prone to forming a cavity, and the product reliability is affected.

Description

Technical Field

[0001] This application relates to the field of semiconductor packaging technology, and more specifically, to a lead frame and semiconductor packaging structure. Background Technology

[0002] Quad Flat No-lead (QFN) packages hold a significant share of the packaging market due to their excellent heat dissipation, high packaging efficiency, and extremely low impedance and self-inductance. QFN packaging offers advantages such as mature technology, low cost, and good thermoelectric performance. As semiconductor devices rapidly move towards functionalization and miniaturization, the demand for QFN packaging is also expanding.

[0003] When using QFN packaging, the leadframe base island primarily serves the crucial functions of mounting and securing the chip, as well as assisting in chip heat dissipation. However, when mounting QFN products onto a circuit board, due to the relatively large area of ​​the leadframe base island, air between the solder layers is difficult to completely escape during the soldering process between the leadframe base island and the circuit board pads. This residual air forms voids, severely impacting product reliability and becoming a key factor restricting product quality improvement. Utility Model Content

[0004] The purpose of this application is to provide a lead frame and semiconductor packaging structure that can solve the problem that residual air between the solder layer during the soldering of the lead frame base island and the PCB board pads can easily form voids and affect product reliability.

[0005] The embodiments of this application are implemented as follows:

[0006] A first aspect of this application provides a leadframe, including a metal frame and a base island connected to the metal frame. The top surface of the base island is used for mounting a chip. A pin assembly is disposed on the metal frame. The pin assembly includes stacked and interconnected inner pins and outer pins. The inner pins are connected to the metal frame, and the outer pins protrude from the bottom surfaces of the metal frame and the base island. The inner pins are used to connect to the chip, and the outer pins are used to connect to a circuit board. This leadframe can solve the problem that residual air between the solder layer and the PCB pads during soldering of existing leadframes can easily form voids, affecting product reliability.

[0007] As one possible implementation, the orthogonal projection of the outer pin onto the inner pin falls within the range of the orthogonal projection of the inner pin.

[0008] As one possible implementation, the sidewall of the outer pin is provided with an inwardly recessed arc-shaped recess and / or an outwardly protruding arc-shaped protrusion.

[0009] In one possible implementation, the metal frame has a ring-shaped closed structure, and the base island is located in the central region of the ring-shaped closed structure.

[0010] In one possible implementation, the number of pin assemblies is multiple, and the multiple pin assemblies are distributed at circumferential intervals along the metal frame.

[0011] In one possible implementation, the metal frame and the base island are connected by a plurality of reinforcing ribs, which are distributed at intervals along the circumference of the metal frame.

[0012] As one possible implementation, the height of the reinforcing rib is equal to the height of the base island or the metal frame along the line connecting the top and bottom surfaces of the base island.

[0013] As one possible implementation, the height of the base island is less than the height of the metal frame along the line connecting the top and bottom surfaces of the base island.

[0014] In one possible implementation, the bottom surface of the base island is flush with the bottom surface of the metal frame, and the top surface of the base island is recessed into the top surface of the metal frame.

[0015] A second aspect of this application provides a semiconductor packaging structure including the lead frame described above. This lead frame can solve the problem that residual air between the solder layer and the solder pads on the PCB board during the soldering of existing lead frames can easily form voids, affecting product reliability.

[0016] The beneficial effects of the embodiments of this application include:

[0017] The leadframe includes a metal frame and a base island connected to the metal frame. The top surface of the base island is used for chip mounting. A pin assembly is disposed on the metal frame, comprising stacked and interconnected inner and outer pins. The inner pins are connected to the metal frame, and the outer pins protrude from the bottom surface of the metal frame and the base island. The inner pins are used to connect to the chip, and the outer pins are used to connect to the circuit board. Compared to existing technologies, the stacked arrangement of inner and outer pins provided in this application increases the number and density of pins, meeting the increasing pin requirements of chips and adapting to the trend of miniaturization and high performance in electronic devices. The interconnection of inner and outer pins ensures the continuity and stability of signal transmission, while improving the overall mechanical strength of the pin assembly, enabling it to withstand greater external forces without easily breaking or desoldering. The design of the outer pins protruding from the bottom surface of the metal frame and the base island makes soldering the leadframe to the circuit board easier, allowing for better positioning and alignment during soldering, thus improving the success rate and quality of soldering. More importantly, the external leads provide channels for solder flow and air venting, reducing the formation of solder voids, thereby enhancing the mechanical strength and electrical connection performance of the solder joints, reducing the risk of open circuits or short circuits caused by poor soldering, and thus improving the reliability and stability of the product. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is one of the structural schematic diagrams of the lead frame provided in the embodiments of this application;

[0020] Figure 2 for Figure 1 The front view;

[0021] Figure 3 This is the second schematic diagram of the lead frame provided in the embodiments of this application;

[0022] Figure 4 for Figure 3 The front view;

[0023] Figure 5 for Figure 3 Side view.

[0024] Icons: 100-lead frame; 10-metal frame; 11-pin assembly; 111-inner pin; 112-outer pin; 1121-arc recess; 20-base island; 30-reinforcing rib; 30A-first reinforcing rib; 30B-second reinforcing rib. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0026] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. These terms are used only for the convenience of describing this application and for 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. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "horizontal," "vertical," etc., do not indicate that the component must be absolutely horizontal or suspended, but can be slightly tilted. The terms "first," "second," and "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0027] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" 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 a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0028] Please refer to the reference. Figures 1 to 5This application provides a leadframe 100, including a metal frame 10 and a base island 20 connected to the metal frame 10. The top surface of the base island 20 is used for mounting chips. A pin assembly 11 is disposed on the metal frame 10. The pin assembly 11 includes inner pins 111 and outer pins 112 stacked and interconnected. The inner pins 111 are connected to the metal frame 10, and the outer pins 112 protrude from the bottom surface of the metal frame 10 and the base island 20. The inner pins 111 are used for connecting to the chip, and the outer pins 112 are used for connecting to the circuit board. This leadframe 100 can solve the problem that residual air between the solder layers during soldering of the base island 20 and the PCB board pads in existing leadframes 100 can easily form voids, affecting product reliability.

[0029] It should be noted that, as Figures 1 to 5 As shown, in this embodiment, the lead frame 100 includes a metal frame 10 and a base island 20. The metal frame 10 serves as the main structure of the lead frame 100, supporting and fixing other components. The metal frame 10 can be made of a metal material with good conductivity and certain mechanical strength, such as copper or gold, to ensure stable current conduction within the metal frame 10, while also ensuring the stability of the metal frame 10 under various environments, preventing deformation and maintaining the integrity of the overall structure. The top surface of the base island 20 is used to mount chips, providing a mounting platform for the chips. The base island 20 typically has good electrical and thermal conductivity. Connected to the metal frame 10, the base island 20 not only fixes the specific position of the chip during operation but also conducts away the heat generated by the chip, thus assisting in chip heat dissipation and ensuring the normal operation of the chip.

[0030] A pin assembly 11 is provided on the metal frame 10. The pin assembly 11 includes stacked and interconnected inner pins 111 and outer pins 112. The inner pins 111 connect to the metal frame 10 on one hand, realizing electrical connection with external circuits, and on the other hand, connect to the chip, transmitting signals from the chip to the external circuits, acting as a bridge. The inner pins 111 typically have high precision and good conductivity to ensure the accuracy and stability of signal transmission. The outer pins 112 protrude from the bottom surface of the metal frame 10 and the base island 20 for connection with the circuit board. During the soldering process, the outer pins 112 protruding from the bottom surface provide a flow channel for the solder, allowing more air to escape from the soldering area. At the same time, the presence of the outer pins 112 also changes the heat transfer and solder flow pattern during soldering, which helps to distribute the solder more evenly and reduces the possibility of solder voids caused by air retention. The shape and size design of the outer pins 112 can also be matched with the pads on the circuit board to ensure good soldering effect and electrical connection performance.

[0031] Compared to existing technologies, the stacked arrangement of inner pins 111 and outer pins 112 provided in this application increases the number and density of pins, meeting the increasing pin requirements of chips and adapting to the trend of miniaturization and high performance in electronic devices. The interconnection of inner pins 111 and outer pins 112 ensures the continuity and stability of signal transmission, while also improving the overall mechanical strength of the pin assembly 11, enabling it to withstand greater external forces without easily breaking or detaching. The design of the outer pins 112 protruding from the bottom surface of the metal frame 10 and the base island 20 makes soldering the lead frame 100 to the circuit board easier, allowing for better positioning and alignment during soldering, thus improving the success rate and quality of soldering. More importantly, the outer pins 112 provide channels for solder flow and air expulsion, reducing the formation of solder voids, thereby enhancing the mechanical strength and electrical connection performance of the solder joint, reducing the risk of open circuits or short circuits due to poor soldering, and ultimately improving the reliability and stability of the product.

[0032] As one possible implementation method, such as Figure 2 and Figure 4 As shown, in this embodiment, the orthographic projection of the outer pin 112 onto the inner pin 111 falls within the range of the orthographic projection of the inner pin 111.

[0033] It should be noted that, as Figure 2 and Figure 4 As shown, in this embodiment, in the lead frame 100 structure, when viewed from a direction perpendicular to the plane containing the inner pin 111 and the outer pin 112, the projection of the outer pin 112 on the plane is completely contained within the projection of the inner pin 111 on the same plane. This means that the outer pin 112 is relatively compact in spatial position relative to the inner pin 111, and does not exceed the range defined by the inner pin 111. This design aims to optimize the spatial layout of the lead frame 100 while ensuring pin functionality, making the entire structure more compact and reasonable, and contributing to the miniaturization of the lead frame 100.

[0034] Furthermore, the relative positional relationship between the inner pin 111 and the outer pin 112 can make the electric field distribution between the pin assemblies 11 more uniform, reducing electromagnetic coupling and crosstalk between the pin assemblies 11. Because the projection of the outer pin 112 does not exceed the inner pin 111, it can effectively reduce mutual interference between signals of different pin assemblies 11 during signal transmission, improve the accuracy and stability of signal transmission, and help improve the electrical performance of the entire electronic device.

[0035] As one possible implementation method, such as Figure 3 and Figure 4 As shown, in this embodiment, the sidewall of the outer pin 112 is provided with an inwardly recessed arc-shaped recess 1121 and / or an outwardly protruding arc-shaped protrusion.

[0036] It should be noted that, as Figure 3 and Figure 4 As shown, in this embodiment, the outer pin 112 is the part of the lead frame 100 used for connection with the circuit board. It has an inwardly recessed arc-shaped recess 1121 and / or an outwardly protruding arc-shaped protrusion on its sidewall, which is a special design for the structure of the outer pin 112. The arc-shaped recess 1121 is an arc-shaped area that is recessed inward on the sidewall of the pin, while the arc-shaped protrusion is an arc-shaped portion that protrudes outward. These arc-shaped structures can be continuous or discontinuous, and their shape and size can be adjusted according to specific design requirements and process requirements.

[0037] Through the aforementioned special design, the shape of the sidewall of the outer pin 112 is altered, making it no longer a simple planar or straight shape, thereby increasing the surface area of ​​the sidewall of the outer pin 112. During soldering, more solder can adhere to the outer pin 112, thus increasing the bonding area between the solder and the outer pin 112, improving the strength and reliability of the solder joint, enabling the solder joint to better withstand mechanical and electrical stresses, and reducing the occurrence of soldering defects such as cold solder joints and solder detachment.

[0038] Furthermore, the arc-shaped structure guides the flow of solder during the soldering process. When the solder contacts the outer pin 112, it flows along the surface of the arc-shaped concave portion 1121 and the arc-shaped convex portion, helping to distribute the solder more evenly around the outer pin 112 and preventing solder buildup in certain localized areas, thereby improving the quality and consistency of the soldering. Simultaneously, this guiding effect also makes it easier for the solder to fill the gap between the outer pin 112 and the circuit board, reducing the formation of solder voids.

[0039] Meanwhile, during the soldering process, air around the outer pin 112 needs to be expelled in a timely manner; otherwise, air bubbles or voids will form in the solder, affecting the soldering quality. The arc-shaped protrusion allows air at the outer pin 112 to escape along the outward arc, preventing residual air bubbles in the solder from causing poor bonding between the outer pin 112 and the circuit board. The arc-shaped concave portion 1121 also provides a certain escape channel for air, allowing it to escape smoothly during the solder flow, further reducing the probability of soldering voids.

[0040] As one possible implementation method, such as Figures 1 to 4 As shown, in this embodiment, the metal frame 10 has a ring-shaped closed structure, and the base island 20 is located in the central region of the ring-shaped closed structure.

[0041] It should be noted that, as Figures 1 to 4As shown, in this embodiment, the metal frame 10 has a closed annular structure. This annular structure can be various shapes such as circular, elliptical, or square (with rounded corners), and its main characteristics are continuity and closure. The base island 20 is located at the center of the closed annular structure enclosed by the metal frame 10. From a spatial layout perspective, the base island 20 is evenly surrounded by the metal frame 10 in the middle, and the base island 20 and various parts of the metal frame 10 can maintain a relatively balanced distance.

[0042] The annular closed metal frame 10 provides uniform support for the base island 20 and the chip, making the entire lead frame 100 structure more stable. Compared with other non-closed or irregular frame structures, the annular closed structure can better disperse stress when subjected to external forces, reducing the risk of local deformation or damage, thereby improving the reliability of the lead frame 100 during manufacturing, assembly, and use, and protecting the chip from damage caused by external impacts.

[0043] In addition, the annular closed metal frame 10 can provide a certain degree of electromagnetic shielding. It can limit the leakage of electromagnetic fields generated by the internal chip and pin assembly 11 to the outside, while also reducing the impact of external electromagnetic interference on the chip, improving the stability of chip operation and the accuracy of signal transmission. Especially for some electronic devices with high requirements for electromagnetic compatibility, such as mobile phones and computers, this structure helps to improve the overall performance of the device.

[0044] Meanwhile, the base island 20 is located in the central region of the annular closed structure, which allows for a more uniform electric field distribution around the base island 20. This is beneficial for the electrical connection between the chip and the pin assembly 11, reduces electric field concentration, lowers the possibility of partial discharge, improves the insulation performance and electrical reliability of the lead frame 100, and ensures that the chip can operate in a stable electrical environment.

[0045] As one possible implementation method, such as Figures 1 to 4 As shown, in this embodiment, there are multiple pin assemblies 11, and the multiple pin assemblies 11 are distributed at intervals along the circumference of the metal frame 10.

[0046] It should be noted that, as Figures 1 to 4 As shown, in this embodiment, the metal frame 10 has a ring-shaped closed structure, and there are multiple pin assemblies 11. These pin assemblies 11 are arranged sequentially along the circumference of the metal frame 10 at certain intervals to avoid current concentration in certain local areas, thereby reducing resistance loss and heat generation. Each pin assembly 11 is connected to the metal frame 10, and a relatively uniform interval is maintained between adjacent pin assemblies 11 to ensure good electrical connection and mechanical stability when connected to other electronic components.

[0047] Furthermore, the multiple pin assemblies 11 are spaced apart circumferentially along the metal frame 10, increasing the heat dissipation area. During operation, the pin assemblies 11 can conduct heat generated by the chip and base island 20 to the surrounding environment through the metal frame 10. Because the pin assemblies 11 are more dispersed, heat can be dissipated more evenly, preventing heat accumulation in localized areas. This improves the overall heat dissipation performance of the lead frame 100, reduces the chip's operating temperature, and thus ensures the chip's performance and reliability.

[0048] As one possible implementation method, such as Figures 1 to 4 As shown, in this embodiment, the metal frame 10 and the base island 20 are connected by a plurality of reinforcing ribs 30, which are distributed at intervals along the circumference of the metal frame 10. As one possible implementation, such as... Figure 1 and Figure 3 As shown, in this embodiment, along the line connecting the top and bottom surfaces of the base island 20, the height of the reinforcing rib 30 is equal to the height of the base island 20 or the metal frame 10. For example, in this embodiment, the height of the first reinforcing rib 30A is equal to the height of the metal frame 10, and the height of the second reinforcing rib 30B is equal to the height of the base island 20.

[0049] It should be noted that, as Figures 1 to 4 As shown, in this embodiment, the metal frame 10 is the external support part of the entire structure, the base island 20 is the internal support part located in the central region of the metal frame 10 for carrying the chip, and the reinforcing rib 30 is a structural component for connecting the metal frame 10 and the base island 20. Multiple reinforcing ribs 30 are evenly distributed along the circumference of the metal frame 10 at certain intervals, like a bridge, firmly connecting the metal frame 10 and the base island 20 together, making the entire structure an organic whole.

[0050] The presence of stiffeners 30 increases the connection points and connection area between the metal frame 10 and the base island 20, making the connection between the two more robust. Multiple stiffeners 30 are distributed circumferentially to evenly transfer force and avoid stress concentration in a local area, thereby effectively preventing problems such as loosening or detachment between the base island 20 and the metal frame 10, and improving the reliability of the entire structure when subjected to external impact or vibration.

[0051] The stiffeners 30 enhance the rigidity of the overall structure composed of the metal frame 10 and the base island 20. Multiple stiffeners 30 can resist structural deformation to a certain extent, maintain the relative positional accuracy of the base island 20 and the metal frame 10, and reduce structural torsion and deformation even under large external forces, ensuring that components such as chips can operate in a stable environment.

[0052] Furthermore, the reinforcing ribs 30 provide an additional path for heat transfer from the base island 20 to the metal frame 10. Since the reinforcing ribs 30 are tightly connected to both the metal frame 10 and the base island 20, when the chip on the base island 20 generates heat, the heat can be quickly conducted to the metal frame 10 through the reinforcing ribs 30, and then dissipated into the surrounding environment by the metal frame 10. The multiple reinforcing ribs 30 are distributed circumferentially, allowing heat to be more evenly distributed across the entire metal frame 10, increasing the heat dissipation area, improving heat dissipation efficiency, helping to reduce the chip's operating temperature, and extending its lifespan.

[0053] As one possible implementation method, such as Figure 1 and Figure 3 As shown, in this embodiment, along the line connecting the top and bottom surfaces of the base island 20, the height of the base island 20 is less than the height of the metal frame 10. As one possible implementation, such as... Figure 1 and Figure 3 As shown, in this embodiment, the bottom surface of the base island 20 is flush with the bottom surface of the metal frame 10, and the top surface of the base island 20 is recessed into the top surface of the metal frame 10.

[0054] It should be noted that, as Figure 1 and Figure 3 As shown, in this embodiment, along the line connecting the top and bottom surfaces of the base island 20, the height of the base island 20 is lower than the height of the lead frame 100. This height design facilitates chip stacking operations, allowing multiple chips to be stacked and installed within a limited space, thus improving product integration. Furthermore, since the height of the metal frame 10 is greater than the height of the base island 20, when the lead frame 100 is subjected to external mechanical impact or collision, the metal frame 10 can act as a buffer and protect the outer periphery of the base island 20, reducing the intensity of external forces acting directly on the base island 20. This reduces the risk of damage to the base island 20 and the chips mounted on it due to external forces, improving the mechanical reliability of the entire lead frame 100 structure.

[0055] This application also provides a semiconductor package structure, including the lead frame 100 described above. Since the structure and beneficial effects of the lead frame 100 have been described in detail in the foregoing embodiments, they will not be repeated here.

[0056] The above description is merely an optional embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

[0057] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this application will not describe the various possible combinations separately.

Claims

1. A leadframe, characterized by, The lead frame comprises a metal frame and an island connected with the metal frame, a top surface of the island is used for mounting a chip, a pin assembly is arranged on the metal frame, the pin assembly comprises inner pins and outer pins which are arranged in a stack and connected with each other, the inner pins are connected with the metal frame, the outer pins protrude from the metal frame and a bottom surface of the island, the inner pins are used for connecting with the chip, and the outer pins are used for connecting with a circuit board.

2. The leadframe of claim 1, wherein, A normal projection of the outer pin on the inner pin falls within a range of a normal projection of the inner pin.

3. The leadframe of claim 2, wherein, An arc-shaped recess is arranged inwardly on a side wall of the outer pin and / or an arc-shaped protrusion is arranged outwardly on the side wall of the outer pin.

4. The leadframe of claim 1, wherein, The metal frame is in a ring-shaped closed structure, and the island is located in a central region of the ring-shaped closed structure.

5. The leadframe of claim 4, wherein, The number of the pin assemblies is multiple, and the multiple pin assemblies are distributed along a circumferential direction of the metal frame.

6. The leadframe of claim 4, wherein, The metal frame and the island are connected through multiple reinforcing ribs, and the multiple reinforcing ribs are distributed along the circumferential direction of the metal frame.

7. The leadframe of claim 6, wherein, Along a connecting direction of the top surface and the bottom surface of the island, a height of the reinforcing rib is equal to a height of the island or the metal frame.

8. The leadframe of claim 1, wherein, Along the connecting direction of the top surface and the bottom surface of the island, a height of the island is less than a height of the metal frame.

9. The leadframe of claim 8, wherein, The bottom surface of the island is flush with a bottom surface of the metal frame, and a top surface of the island is recessed from a top surface of the metal frame.

10. A semiconductor package structure, comprising: The lead frame comprises the lead frame according to any one of claims 1 to 9.

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