A lead frame with extended pins

Abstract

This utility model discloses a lead frame with extended pins, relating to the field of semiconductor packaging technology. The lead frame includes a base island, a first pin array, and a second pin array. The base island, from top to bottom, includes an electrical shielding layer, a heat diffusion layer, a dielectric isolation layer, a signal transmission layer, a stress conditioning layer, and an interface enhancement layer. The heat diffusion layer is fixed above the electromagnetic shielding layer via interface metallurgical bonding, with its edge extending upwards to form a ring-shaped support platform. The first pin array extends horizontally outwards from the outer wall of the ring-shaped support platform of the heat diffusion layer and extends to the outer side of the base island. The second pin array extends inwards from the central region of the dielectric isolation layer towards the inner side of the ring-shaped support platform. This lead frame with extended pins, through a multi-layer composite base island structure and the coordinated design of the extended pins, achieves performance optimization in electromagnetic shielding, high-frequency signal attenuation reduction, and mechanical strength enhancement.

Description

Technical Field

[0001] This utility model relates to the field of semiconductor packaging technology, specifically to a lead frame with internally extended pins. Background Technology

[0002] In today's rapidly developing semiconductor technology, semiconductor packaging is of paramount importance, and the lead frame, as its key carrier, directly impacts the reliability of devices in scenarios such as high-frequency communication and high-power applications. However, traditional lead frame structures have many shortcomings.

[0003] In terms of electromagnetic compatibility, traditional lead frames mostly use a single-layer metal substrate or a simple stacked design. Faced with high-frequency interference above 10GHz, their electromagnetic shielding layer has a suppression efficiency of less than 30 dB, making it difficult to effectively block external high-frequency interference. At the same time, the pin layout lacks electromagnetic field conduction design, which leads to increased signal crosstalk.

[0004] Thermal management is also a major challenge for traditional lead frames. Mismatch in the coefficient of thermal expansion (CTE) of interlayer materials can cause stress at the interface due to the different degrees of thermal expansion and contraction of each layer within the temperature range of -50 to 150°C. This can easily lead to interface delamination and seriously affect the structural and electrical performance of the lead frame.

[0005] During high-frequency signal transmission, the skin effect causes the signal attenuation rate to exceed -2 ​​dB / cm, while the insulation strength of conventional dielectric layers is insufficient to block electromagnetic leakage, further aggravating signal attenuation and interference. In addition, the interlayer bonding energy of lead frames prepared by traditional sputtering processes is low, and the interface crack propagation rate reaches 35% after multiple thermal cycles, which greatly shortens the package life.

[0006] Current improvement solutions mostly focus on single performance optimization, such as using ceramic-filled resin to improve dielectric strength or improving heat dissipation through pin bending design. However, these solutions are difficult to solve the problem of multi-physics coupling in a coordinated manner.

[0007] Therefore, to address the above issues, the applicant needs to design a lead frame with internally extending pins to solve the problem. Utility Model Content

[0008] The purpose of this invention is to provide a lead frame with inwardly extending pins to solve the problems mentioned in the background section.

[0009] To achieve the above objectives, this utility model provides the following technical solution: a lead frame with inwardly extending leads, comprising a base island, a first lead array, and a second lead array. The base island comprises, from top to bottom, an electrical shielding layer, a heat diffusion layer, a dielectric isolation layer, a signal transmission layer, a stress adjustment layer, and an interface enhancement layer. The electrical shielding layer is composed of an iron-nickel alloy matrix and dispersed silicon carbide particles, with a periodic concave-convex microstructure formed on its surface. The heat diffusion layer is fixed above the electromagnetic shielding layer by an interface metallurgical bonding method, with its edge extending upward to form an annular support platform. The first lead array extends horizontally outward from the outer wall of the annular support platform of the heat diffusion layer and extends to the outside of the base island, with its extension direction consistent with the wave crest direction of the concave-convex microstructure of the electromagnetic shielding layer. The second lead array extends from the central region of the dielectric isolation layer to the inner side of the annular support platform.

[0010] Furthermore, the dielectric isolation layer covers the upper surface of the thermal diffusion layer, and the dielectric isolation layer material is silicon nitride composite ceramic.

[0011] Through the above structural design, silicon nitride composite ceramic materials significantly enhance the synergistic advantages of interlayer insulation performance and thermal stability, thereby improving overall stability.

[0012] Furthermore, a tree-like fractal conductive path is etched on the surface of the dielectric isolation layer, and the signal transmission layer is placed inside the conductive path.

[0013] Through the above structural design, the tree-like fractal conductive path optimizes the current distribution characteristics through biomimetic principles, thereby increasing the effective conductive cross-sectional area and reducing the current skin effect.

[0014] Furthermore, the material of the signal transmission layer is a nanocrystalline copper-graphene composite material.

[0015] Through the above structural design, the nanocrystalline copper-graphene composite material achieves a breakthrough in electrical and mechanical properties. Vertical graphene sheets prepared by chemical vapor deposition are interspersed in the copper matrix to form a three-dimensional conductive network, thereby reducing the resistivity of the material.

[0016] Furthermore, the stress buffer layer covers the outside of the signal transmission layer and is provided with a wave-shaped stress relief groove that matches the conductive path.

[0017] Through the above structural design, the wave-shaped stress relief groove achieves dynamic stress dissipation through a geometric nonlinear deformation mechanism. It can reduce the local stress concentration factor by changing the curvature of the groove. Combined with the viscoelastic properties of silicone rubber, it can absorb a large amount of thermal stress within the temperature range of -55℃ to 150℃.

[0018] Furthermore, the stress buffer layer is made of silicone rubber.

[0019] Through the above structural design, silicone rubber has a strong ability to withstand harsh environments, making the lead frame widely applicable.

[0020] Furthermore, the interface enhancement layer is composed of alternating depositions of copper nanopillar arrays and diamond-like carbon films.

[0021] Through the above structural design, the alternating structure of copper nanopillars / diamond-like carbon films enhances the interlayer bonding through the interfacial nano-interlocking mechanism. At the same time, the copper nanopillars prepared by focused ion beam and the diamond-like carbon film form a mechanical-chemical dual composite interface. The high hardness of the diamond-like film, combined with the plastic deformation capability of the copper pillars, allows the intact interface structure to be maintained after multiple thermal cycles.

[0022] Compared with the prior art, the beneficial effects of this utility model are:

[0023] This leadframe with extended pins achieves multi-dimensional performance breakthroughs through a multi-layered composite structure design: the synergistic effect of a silicon nitride composite ceramic dielectric isolation layer and a dendritic fractal conductive path ensures insulation strength while reducing high-frequency signal transmission loss and significantly suppressing electromagnetic crosstalk; the nanocrystalline copper-graphene composite signal layer constructs a three-dimensional conductive network, improving conductivity and tensile strength, and combined with a corrugated stress relief groove and a silicone rubber buffer layer, it achieves high-strength thermal stress absorption and electromagnetic-mechanical vibration suppression; the alternating interface reinforcement layer of copper nanopillars / diamond-like carbon film enhances interlayer bonding energy and maintains stability after multiple thermal cycles through a mechanical-chemical composite bonding mechanism, and combined with the periodic microstructure of the iron-nickel alloy-silicon carbide electric shielding layer, it forms a comprehensive advantage that combines electromagnetic shielding, thermal expansion matching, and directional heat dissipation. The overall structure exhibits excellent reliability and signal fidelity over a wide temperature range. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall three-dimensional structure of the present invention;

[0025] Figure 2 This is a schematic diagram of the base island structure of this utility model;

[0026] Figure 3 This is a schematic diagram of the layered structure of the base island of this utility model.

[0027] In the diagram: 1. Base island; 2. First pin array; 3. Ring-shaped support platform; 4. Second pin array; 5. Electromagnetic shielding layer; 6. Thermal diffusion layer; 7. Dielectric isolation layer; 8. Signal transmission layer; 9. Stress conditioning layer; 10. Interface enhancement layer. Detailed Implementation

[0028] 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.

[0029] like Figures 1-3 As shown, a lead frame with inwardly extending pins according to this utility model includes a base island 1, a first pin array 2, and a second pin array 4. The base island 1 includes, from top to bottom, an electrical shielding layer 5, a heat diffusion layer 6, a dielectric isolation layer 7, a signal transmission layer 8, a stress adjustment layer 9, and an interface reinforcement layer 10. The electrical shielding layer 5 is composed of an iron-nickel alloy matrix and dispersed silicon carbide particles, and its surface forms a periodic concave-convex microstructure. The heat diffusion layer 6 is fixed above the electromagnetic shielding layer 5 by an interface metallurgical bonding method, and its edge extends upward to form an annular support platform 3. The first pin array 2 extends horizontally outward from the outer wall of the annular support platform 3 of the heat diffusion layer 6 and extends to the outside of the base island 1. Its extension direction is consistent with the wave crest direction of the concave-convex microstructure of the electromagnetic shielding layer 5. The second pin array 4 extends from the central region of the dielectric isolation layer 7 to the inner side of the annular support platform 3.

[0030] The dielectric isolation layer 7 covers the upper surface of the heat diffusion layer 6, and the material of the dielectric isolation layer 7 is silicon nitride composite ceramic. The silicon nitride composite ceramic material significantly improves the synergistic advantages of interlayer insulation performance and thermal stability. The high dielectric strength of silicon nitride effectively blocks electromagnetic crosstalk between the signal layer and the heat diffusion layer. The yttrium oxide reinforcing phase doped in the composite ceramic can control the thermal expansion coefficient of the material by forming a grain boundary pinning effect, which will achieve thermal expansion matching with the upper and lower metal layers, avoid interlayer delamination caused by temperature cycling, and thus ensure high stability of the device during long-term operation.

[0031] The surface of the dielectric isolation layer 7 is etched to form a tree-like fractal conductive path, and the signal transmission layer 8 is placed inside the conductive path. The tree-like fractal conductive path optimizes the current distribution characteristics through bionic principles, thereby increasing the effective conductive cross-sectional area and reducing the current skin effect.

[0032] The material of signal transmission layer 8 is a nanocrystalline copper-graphene composite material. The nanocrystalline copper-graphene composite material achieves a breakthrough in conductivity and mechanical properties. Vertical graphene sheets prepared by chemical vapor deposition are interspersed in the copper matrix to form a three-dimensional conductive network, which reduces the resistivity of the material and improves its tensile strength.

[0033] The stress buffer layer 9 covers the outside of the signal transmission layer 8 and is provided with a wave-shaped stress relief groove that matches the conductive path. The wave-shaped stress relief groove realizes dynamic stress dissipation through geometric nonlinear deformation mechanism. The local stress concentration factor can be reduced by changing the curvature of the groove. Combined with the viscoelastic properties of silicone rubber, it can absorb a large amount of thermal stress in the temperature range of -55℃ to 150℃. The phase matching design between the groove and the conductive path further reduces the amplitude of electromagnetic-mechanical coupling vibration and effectively prevents microcracks from propagating along the conductive channel.

[0034] The stress buffer layer 9 is made of silicone rubber. The selection of silicone rubber material is based on its hyperelastic-glass transition characteristics. By controlling the phenyl content in the polydimethylsiloxane chain segment, the material maintains an elastic modulus of less than 5 MPa at -100℃, and a compression set of less than 8% at a high temperature of 180℃. Its volume resistivity is greater than 1×10^15 Ω·cm to ensure the reliability of interlayer insulation.

[0035] The interface reinforcement layer 10 is composed of alternating deposition of copper nanopillar arrays and diamond-like carbon films. The alternating structure of copper nanopillars / diamond-like carbon films enhances the interlayer bonding through the interface nano-interlocking mechanism. At the same time, the copper nanopillars prepared by focused ion beam and the diamond-like carbon film form a mechanical-chemical dual composite interface. The diamond-like film has high hardness, which, combined with the plastic deformation capability of the copper pillars, maintains the complete interface structure after multiple thermal cycles.

[0036] Based on the above-described preferred embodiments of this utility model, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the technical concept of this utility model. The technical scope of this utility model is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A lead frame with inwardly extending leads, characterized in that: The device includes a base island (1), a first pin array (2), and a second pin array (4). The base island (1) includes, from top to bottom, an electrical shielding layer (5), a heat diffusion layer (6), a dielectric isolation layer (7), a signal transmission layer (8), a stress adjustment layer (9), and an interface enhancement layer (10). The electrical shielding layer (5) is composed of an iron-nickel alloy matrix and dispersed silicon carbide particles, and its surface forms a periodic concave-convex microstructure. The heat diffusion layer (6) is fixed above the electromagnetic shielding layer (5) by an interface metallurgical bonding method, and its edge extends upward to form an annular support platform (3). The first pin array (2) extends horizontally outward from the outer wall of the annular support platform (3) of the heat diffusion layer (6) and extends to the outside of the base island (1). Its extension direction is consistent with the wave peak direction of the concave-convex microstructure of the electromagnetic shielding layer (5). The second pin array (4) extends from the central region of the dielectric isolation layer (7) to the inner side of the annular support platform (3).

2. A lead frame with inwardly extending leads according to claim 1, characterized in that: The dielectric isolation layer (7) covers the upper surface of the heat diffusion layer (6), and the material of the dielectric isolation layer (7) is silicon nitride composite ceramic.

3. A lead frame with inwardly extending leads according to claim 1, characterized in that: The surface of the dielectric isolation layer (7) is etched to form a tree-like fractal conductive path, and the signal transmission layer (8) is placed inside the conductive path.

4. A lead frame with inwardly extending leads according to claim 3, characterized in that: The material of the signal transmission layer (8) is a nanocrystalline copper-graphene composite material.

5. A lead frame with inwardly extending leads according to claim 4, characterized in that: The stress buffer layer (9) covers the outside of the signal transmission layer (8) and is provided with a wave-shaped stress relief groove that matches the conductive path.

6. A lead frame with inwardly extending leads according to claim 5, characterized in that: The stress buffer layer (9) is made of silicone rubber.

7. A lead frame with inwardly extending leads according to claim 1, characterized in that: The interface enhancement layer (10) is composed of an array of copper nanopillars and a diamond-like carbon film deposited alternately.

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