A lead frame for enhancing the plastic encapsulation strength, its application, and a packaging method

Abstract

The present invention provides a lead frame for enhancing the plastic encapsulation strength, its application and a plastic encapsulation method. The lead frame includes a fixed bottom plate, terminals and pins; the terminals are distributed on different edges or in the middle of the fixed bottom plate, and are integrally formed with the fixed bottom plate, and are bent towards the upper surface of the fixed bottom plate at the bottom end; the pins are placed on one side of the fixed bottom plate where no terminals are provided, and are separated from the fixed bottom plate. The lead frame for enhancing the plastic encapsulation strength disclosed by the present invention greatly increases the contact area between the lead frame and the plastic encapsulant, improves the bonding effect, and the vertical terminals can serve as the internal skeleton of the plastic encapsulant, enhancing the strength of the entire composite structure in the vertical direction and reducing the risk of collapse, and ultimately comprehensively enhancing the mechanical strength of the plastic encapsulated device.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuit packaging, and particularly to a lead frame for enhancing the strength of plastic packaging, its application, and a packaging method. Background Art

[0002] In the field of integrated circuit packaging, a lead frame is a main structure used in plastic packaging technology. It mainly functions to carry an IC chip, connect the chip to external board-level circuits, transmit electrical signals, and provide installation and fixation. In the actual application scenarios of plastic-packaged components, such as in the automotive and aerospace industries, plastic-packaged components may face extremely harsh environments such as drop impacts and high-speed collisions. To ensure the normal operation of plastic-packaged components in such harsh environments, extremely high requirements are placed on the strength of the plastic packaging structure. To improve the various performance of plastic-packaged devices, higher requirements are put forward for the lead frames of plastic-packaged devices, requiring them to have better electrical conductivity, thermal conductivity, and higher frame strength to meet the complex application requirements in multiple fields.

[0003] The existing measures to strengthen the structural strength of plastic-packaged lead frames are generally divided into two types: One is to optimize the selection of frame materials. Different types of copper materials or iron-nickel alloy materials are selected according to different strength requirements, or dopants are added to the plastic packaging material to enhance the strength characteristics of the plastic-packaged component material and reduce the risk of deformation and damage. The other is to conduct directional design and processing on the lead frame. The bonding strength between the frame and the plastic packaging material is improved through the design of grooves, holes, and shaped edges to prevent delamination, separation, and cracking of the contact surface under external mechanical stress. For example, in the prior art, notches, double-layer grooves, protrusions, pinholes, and V-shaped scratches are designed on the frame to enhance the bonding strength between the plastic packaging material and the frame, or circular holes are formed by stamping or drilling methods in the design to fully contact and improve airtightness. Or in the design, the outer side of the metal-based island is inclined, and the outer side wall is embedded in the plastic packaging body to improve the delamination phenomenon between the lead frame and the plastic packaging body.

[0004] Although the above-mentioned method of directional design of the frame structure can improve the reliability of the structure to a certain extent, there are still certain limitations. The method of improving the bonding strength of the plastic packaging material through the design of grooves, holes, etc. is mainly achieved by increasing the contact area. The lead frame in plastic packaging is a two-dimensional planar structure as a whole. The increased contact area by setting local microstructures will not exceed 10% of the original. Therefore, the overall strength improvement is limited. At the same time, the support of the vast majority of the plastic packaging material perpendicular to the upper side of the lead frame by the frame matrix is also relatively limited. When subjected to strong external mechanical stress, large-area collapse may occur only relying on the single mechanical support of the plastic packaging material itself. Therefore, it is impossible to effectively protect the internal structures such as chips and bonding wires. Summary of the Invention

[0005] In view of this, the present invention provides a lead frame for enhancing the plastic packaging strength, its application and a packaging method, which solve the problem that the contact area between the plastic packaging material and the lead frame is limited in the three-dimensional space level.

[0006] To achieve this goal, the present invention adopts the following technical solutions:

[0007] As the first aspect of the present invention, a lead frame for enhancing the plastic packaging strength is disclosed. The frame includes a fixed bottom plate, terminals and pins.

[0008] The terminals are distributed on different edges or in the middle of the fixed bottom plate, and are integrally formed with the fixed bottom plate, and are bent towards the upper surface direction of the fixed bottom plate at the bottom end.

[0009] The pins are divided into single pins and pin groups. The single pins and pin groups are placed side by side on one side of the fixed bottom plate where there are no terminals, and are separated from the fixed bottom plate.

[0010] Preferably, the top end of the terminal is bent towards the inner side direction of the fixed bottom plate.

[0011] Preferably, the inner surfaces of the bent parts at the bottom end and the top end of the terminal are arc chamfers.

[0012] Preferably, through holes are provided in the middle area of the terminal.

[0013] Preferably, the number of terminals is adjusted according to actual needs.

[0014] As the second aspect of the present invention, an application of a lead frame for enhancing the plastic packaging strength is disclosed. The application is to apply the aforementioned lead frame for enhancing the plastic packaging strength in the plastic packaging that requires the use of a lead frame.

[0015] Preferably, the plastic packaging that requires the use of a lead frame includes but is not limited to TO packaging and QFN packaging.

[0016] As the third aspect of the present invention, a plastic packaging method is disclosed. The method uses the above-mentioned lead frame for enhancing the plastic packaging strength and plastic packaging material for plastic packaging. During packaging, the plastic packaging material completely covers the terminals of the lead frame, completely fills the through holes in the middle of the terminals, and partially covers the single pins and pin groups.

[0017] The beneficial effects of the present invention are as follows: The lead frame for enhancing the plastic encapsulation strength disclosed in the present invention adds a plurality of protruding terminals to the lead frame, and bends the terminals to the side of the chip and bonding wires. When plastic encapsulation is carried out, the terminals thereon are embedded in the plastic encapsulant. At the same time, with the microstructural design such as through holes on the terminals, the contact area between the lead frame and the plastic encapsulant is greatly increased, enhancing the bonding effect. Moreover, the vertical terminals can serve as the internal skeleton of the plastic encapsulant, improving the strength of the entire composite structure in the vertical direction and reducing the risk of collapse. Ultimately, the mechanical strength of the plastic encapsulated device is comprehensively improved. The lead frame disclosed in the present invention can be used in plastic encapsulation technologies that require the use of lead frames. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic structural diagram of the lead frame for enhancing the plastic encapsulation strength in an embodiment of the present invention;

[0019] Figure 2 It is a schematic diagram of the processing implementation of the lead frame for enhancing the plastic encapsulation strength in an embodiment of the present invention;

[0020] Figure 3 It is a schematic diagram of the relative positions of the plastic encapsulant and the lead frame when plastic encapsulation is carried out using the lead frame for enhancing the plastic encapsulation strength in an embodiment of the present invention;

[0021] Figure 4 It is a simulation diagram comparing the performance of the lead frame of the present invention with that of a planar lead frame in an embodiment of the present invention;

[0022] In the figure: 1. Fixed bottom plate; 2. Pin group; 3. Single pin; 4. Intermediate terminal; 5. Intermediate terminal through hole; 6. Edge terminal I; 7. Edge terminal I through hole; 8. Edge terminal II; 9. Edge terminal II through hole. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] Those of ordinary skill in the art will realize that the embodiments described herein are for helping readers understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed in the present invention, and these deformations and combinations are still within the protection scope of the present invention.

[0024] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] The lead frame for enhancing the plastic packaging strength disclosed in the present invention expands the three-dimensional space inside the plastic packaging material compared to various existing lead frame designs at the present stage, greatly increasing the contact area between the plastic packaging material and the lead frame. Through calculation, the introduction of a highly practical vertical terminal can increase the interface area between the plastic packaging material and the lead frame by up to 50%. The introduction of through-holes further strengthens the connection strength between the lead frame and the plastic packaging material, further reducing the deformation under mechanical shock stress and protecting the fragile chips inside. Through Figure 4 the finite element simulation results comparison of the in-plane lead frame plastic packaging device( Figure 4 left side) and the vertical terminal lead frame packaging device of the present invention( Figure 4 right side), it can be seen that the stress response value on the chip packaged by the vertical terminal lead frame is 4% lower than that on the chip plastic packaged by the in-plane lead frame, and the deformation amount of the in-plane lead frame is significantly larger than that of the vertical terminal lead frame.

[0026] Embodiment

[0027] As Figure 1 shown, the lead frame for enhancing the plastic packaging strength in this embodiment includes a fixed bottom plate 1, three terminals, a single pin 3, and a pin group 2; among them, the three terminals include: an intermediate terminal 4, an edge terminal I 6, and an edge terminal II 8. The three terminals are integrally formed with the fixed bottom plate 1 and are all bent upward from the bottom end toward the upper surface of the fixed bottom plate 1, forming a 90° angle with the fixed bottom plate 1. Moreover, the top ends of the three terminals are also bent inward toward the fixed bottom plate 1, forming a 90° angle. In order to avoid generating sharp edges at the bending positions and damaging the packaging effect, the inner surfaces of the bottom ends and the top ends of the three terminals at the bending positions are chamfered with arc surfaces. At the same time, intermediate terminal through-holes 5, edge terminal I through-holes 7, and edge terminal II through-holes 9 are provided on the three terminals to increase the contact area between the plastic packaging material and the lead frame during plastic packaging.

[0028] As shown in the figure, the single pin 3 and the pin group 2 are placed side by side on the side of the fixed bottom plate 1 where no terminals are provided and are separated from the fixed bottom plate 1.

[0029] The above embodiments are only for illustrating this patent. In actual applications, the vertical terminals embedded in the plastic packaging material can be flexibly adjusted according to actual conditions in terms of specific parameters such as terminal size, bending position, bending angle, bending direction, through-hole size, through-hole quantity, and through-hole position to generate alternative solutions.

[0030] The manufacturing implementation of the above lead frame for enhancing the plastic packaging strength is as Figure 2As shown above, the manufacturing process of the lead frame of the present invention is described by the above embodiments. First, conventional lead frame stamping, surface treatment and other process steps are carried out. The maximum size of the obtained planar frame is 7.25×7.4×0.254 mm. Subsequently, three terminals that need to be bent are selected, and through holes with a diameter of 0.4 mm are opened at the middle position protruding from the bottom plate. Then, the terminals are bent upward by 90° along the root connected to the bottom plate. Finally, the top ends of the terminals are bent inward by 90° again, and a certain chamfer is maintained at the bent part, with a radius of about 0.1 mm.

[0031] The lead frame for enhancing the plastic encapsulation strength of the present invention is not only applicable to a specific encapsulation type. The design therein can be extended to most plastic encapsulation technologies that require the use of lead frames, such as TO encapsulation, QFN encapsulation, etc.

[0032] Regarding the plastic encapsulation method of the lead frame for enhancing the plastic encapsulation strength of the present invention, the plastic encapsulant is distributed according to the contour shown by the dotted line in Figure 3 so as to completely cover the three terminals, and the through holes thereon are also completely filled. The plastic encapsulant partially covers the single pin and the pin group. Such a design expands the three-dimensional space inside the plastic encapsulant, greatly increases the contact area between the plastic encapsulant and the lead frame, and the limiting effect of the through holes further strengthens the locking of the lead frame to the plastic encapsulant. On the premise that the three terminals are smooth and do not damage the structure of the plastic encapsulant, the frame design of this patent can effectively improve the anti-mechanical shock strength of the plastic encapsulated device.

Claims

1. A lead frame for enhancing the strength of plastic encapsulation, characterized in that, The lead frame includes a fixed base plate, terminals, and pins; The terminals are distributed on different edges or in the middle of the fixed base plate, are integrally formed with the fixed base plate, and are bent upward toward the upper surface of the fixed base plate at the bottom end; The pins are divided into single pins and pin groups, the single pins and the pin groups are placed side by side on one side of the fixed base plate where no terminals are provided, and are separated from the fixed base plate; The top ends of the terminals are bent inward toward the inside of the fixed base plate; The lead frame is first subjected to stamping and surface treatment process steps. Subsequently, three terminals that need to be bent are selected, and through holes are opened at the middle position protruding from the base plate. Then, the terminals are bent upward by 90° along the root connected to the base plate. Finally, the top ends of the terminals are bent inward by 90° again, and a certain chamfer is maintained at the bent part; During encapsulation, the encapsulant completely covers the terminals of the lead frame, completely fills the through holes in the middle of the terminals, and partially covers the single pins and pin groups.

2. The lead frame for enhancing the plastic encapsulation strength according to claim 1, wherein The inner surfaces of the bent parts at the bottom ends and top ends of the terminals are chamfered with arc surfaces.

3. The lead frame for enhancing the plastic encapsulation strength according to claim 2, wherein Through holes are provided in the middle area of the terminals.

4. The lead frame for enhancing the plastic encapsulation strength according to claim 3, wherein The number of the terminals is adjusted according to actual requirements.

5. Application of a lead frame for enhancing the strength of plastic encapsulation, characterized in that, The application is to use the lead frame for enhancing the encapsulation strength according to any one of claims 1 to 3 in the encapsulation that requires the use of a lead frame.

6. The application of the lead frame for enhancing the plastic encapsulation strength according to claim 5, characterized in that, The encapsulation that requires the use of a lead frame includes, but is not limited to, TO encapsulation and QFN encapsulation.

Images