Lead frame structure
By reinforcing the solid ribs between the pins and the base island in the lead frame structure, the problem of lateral rib breakage during the semi-etching process of DFN products was solved, achieving higher fracture resistance and stable molding effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- JCET GROUP CO LTD
- Filing Date
- 2025-03-31
- Publication Date
- 2026-04-28
AI Technical Summary
During the semi-etching process of DFN products, the transverse central ribs on both sides of the lead frame are prone to vertical cracks, leading to DB abnormalities and the generation of bubbles in the molding process.
In the lead frame structure, a second solid rib is added between the pin and the base island. Combined with the semi-etched rib, it enhances the support and fracture resistance, avoids cracking, and solves the problem of film-paper separation by increasing the bonding force between the solid rib and the base film.
This improves the fracture resistance of the lead frame, avoids cracking and film separation, and ensures the stability and bubble-free sealing effect of DFN products.
Smart Images
Figure CN224178601U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor packaging, and more particularly to a lead frame structure. Background Technology
[0002] DFN (Dual Flat No-leads Package) is an advanced semiconductor packaging technology belonging to the surface mount technology (SMT) category. It features miniaturization, high performance, and efficient heat dissipation. DFN uses a flat package form factor, with the exposed copper islands directly soldered to the PCB board. The absence of traditional lead structures effectively shortens electrical paths and reduces parasitic inductance. DFN products are widely used in consumer electronics, industrial and communications, automotive electronics, and high-power devices, especially in ultra-thin products.
[0003] To improve DFN dicing efficiency, the center ribs located outside the encapsulation lines of DFN products undergo partial etching. During the MOLD (molding and encapsulation) process, specifically during handling or film removal, the transverse center ribs on both sides of the lead frame (the center ribs on the sides without leads) are prone to penetrating cracks. This can lead to abnormal film-paper separation after DB (die bonding), cause the WB (wire bonding) wires to easily peel the material layer or pattern from the substrate, and result in air bubbles during the molding process. Summary of the Invention
[0004] The problem this application aims to solve is to provide a lead frame structure that enhances the fracture resistance of the transverse central ribs on both sides of the lead frame at the gap positions corresponding to the pins and the base island.
[0005] To address the above problems, this application provides a lead frame structure, comprising:
[0006] A lead frame body, the lead frame body including a base island and pins, the base island being located in the middle of the lead frame body for fixing a chip, and the pins being disposed on at least one side of the base island;
[0007] A central rib is provided around the lead frame body. The central rib includes a first rib and a second rib that are connected to each other. The first rib is located on the side of the lead frame body with pins and is connected to the pins. The second rib is located on the side of the lead frame body without pins.
[0008] The second rib area corresponding to the position between the pin and the base island is a solid rib, and the remaining area of the second rib is a semi-etched rib.
[0009] Since the second rib does not require connection to the pin, there is no need to worry about excessive cutting burrs (causing short circuits in the product). At the same time, the addition of solid ribs strengthens the support and fracture resistance of the lead frame structure. Furthermore, the second rib is not completely encapsulated at the corresponding position of the gap between the pin and the base island. During handling or film removal, the transverse central ribs on both sides of the lead frame (the two sides without pins) are less likely to experience vertical through-cracks at the corresponding positions of the gap between the pin and the base island.
[0010] In an optional embodiment, the first rib is a semi-etched rib.
[0011] In an optional embodiment, the first rib has a solid reinforcing rib in the middle.
[0012] In one alternative embodiment, the thickness of the solid rib is less than or equal to the thickness of the base island, but greater than the thickness of the half-etched rib.
[0013] In one optional embodiment, the thickness of the solid rib is equal to the thickness of the base island, the back of the solid rib is flush with the back of the base island, and the total area of the back of the solid rib, the back of the base island, and the back of the pin is greater than or equal to 30% of the total area of the back of the lead frame structure.
[0014] In an optional embodiment, the pins include two sets, respectively disposed on opposite sides of the base island;
[0015] The first rib and the second rib each consist of two parts, which are sequentially and alternately connected to form the outer frame structure of the central rib.
[0016] In an optional embodiment, a connecting rib is further included, the two ends of which are respectively connected to the base island and the second rib.
[0017] In an optional embodiment, the connecting rib is a semi-etched rib and is connected to the semi-etched rib in the second rib.
[0018] In an optional embodiment, an insulating layer is also included that fills the area between the base island, the pin, and the center rib, as well as the gaps corresponding to the half-etched ribs.
[0019] In one optional embodiment, the two sides of the solid rib of the second rib are insulating layers.
[0020] In one optional embodiment, the pins are a pin array structure, comprising a plurality of pins spaced apart.
[0021] In one optional embodiment, the lead frame structure is a DFN lead frame structure.
[0022] The advantages of the technical solution in this application are:
[0023] Provided that the cutting does not exceed the standard and there are no burrs on both sides of the tube pin, the addition of solid ribs in the second rib area corresponding to the position between the tube pin and the base island strengthens the support and fracture resistance of the lead frame structure. During the handling or film tearing process, the second rib of the lead frame is less likely to experience vertical through-cracks at the position corresponding to the position between the tube pin and the base island.
[0024] Meanwhile, the addition of solid ribs increases the exposed solid area on the back of the lead frame structure, and also increases the area where the exposed solid area of the lead frame structure adheres to the bottom film. This strengthens the bonding force between the lead frame structure and the bottom film, thereby solving the problem of film-paper separation in the molding process, preventing bubble generation in chip molding, and solving the problem that WB (wire bonding) wire bonding can easily peel off the material layer or pattern from the substrate. Attached Figure Description
[0025] Figure 1 This is a bottom view of the lead frame structure in one embodiment of this application;
[0026] Figure 2 for Figure 1 A schematic diagram of the cross-sectional structure along the cutting line AA;
[0027] Figure 3 This is a bottom view of the lead frame structure in another embodiment of this application.
[0028] The labels for the attached figures are as follows:
[0029] 1. Base island; 2. Pipe foot; 3. Middle rib; 31. First rib; 32. Second rib; 33. Connecting rib; 4. Solid rib; 5. Insulation layer; 6. Product sealing line; 7. Back of base island; 8. Solid reinforcing rib. Detailed Implementation
[0030] The specific embodiments of this application will be described in detail below with reference to the accompanying drawings. In describing the embodiments of this application in detail, for ease of explanation, the schematic diagrams may be partially enlarged without adhering to the general scale, and the schematic diagrams are merely examples and should not limit the scope of protection of this application. Furthermore, in actual manufacturing, the three-dimensional spatial dimensions of length, width, and depth should be included.
[0031] Through experiments, the inventors discovered that the transverse central ribs on both sides of the lead frame (without the central ribs on both sides of the pins) are prone to vertical through-cracks at the gap between the pins and the base island. Research revealed that the main reason is that the vertical through-cracks in the transverse central ribs occur between the pins and the base island. The area between the pins and the base island is entirely covered by plastic sealant. Due to the large area of the base island, the transverse central ribs corresponding to the area between the pins and the base island are prone to generating significant stress during handling or film removal, resulting in vertical through-cracks.
[0032] Therefore, this application provides a lead frame structure, in conjunction with reference to the reference. Figure 1 and Figure 2 ,in Figure 1 This is a bottom view of the lead frame structure (hidden insulation layer 5). Figure 2 for Figure 1 A cross-sectional structural diagram along the cutting line AA, including:
[0033] The lead frame body includes a base island 1 and pins 2. The base island 1 is located in the middle of the lead frame body and is used to fix the chip (not shown in the figure). The pins 2 are located on opposite sides of the base island 1.
[0034] A central rib 3 is provided around the lead frame body. The central rib 3 includes a first rib 31 and a second rib 32 that are connected to each other. The first rib 31 is located on opposite sides of the lead frame body with pins 2 and is connected to the pins 2. The second rib 32 is located on opposite sides of the lead frame body without pins.
[0035] The first rib 31 and the second rib 32 are semi-etched ribs, and the position of the second rib 32 corresponding to the gap between the pin 2 and the base island 1 is a solid rib 4.
[0036] Since the first rib 31 and the second rib 32 are semi-etched ribs, and the thickness of the semi-etched ribs is less than the total thickness of the base island, it facilitates the cutting process of the DFN frame structure and effectively reduces the problem of excessive cutting burrs. Furthermore, since the second rib 32 does not connect to the pin 2, there is no need to worry about excessive cutting burrs (leading to short circuits in the product). The corresponding position of the second rib 32 at the gap between the pin 2 and the base island 1 is a solid rib 4, and the thickness of the solid rib 4 is equal to the total thickness of the base island. The corresponding solid rib 4 is not semi-etched, thus strengthening the support and fracture resistance of the lead frame structure. Even if the corresponding position between the pin 2 and the base island 1 is fully encapsulated, the reinforcement of the corresponding second rib 32 prevents vertical through-cracks in the transverse central ribs 3 (the second ribs on both sides without pins) at the corresponding positions between the pin 2 and the base island 1 during handling or film removal.
[0037] In this embodiment, the thickness of the solid rib 4 is equal to the total thickness of the base island 1, and greater than the thickness of the half-etched rib; therefore, the solid rib 4 is not subjected to half-etching. In other embodiments, a portion of the thickness of the solid rib is etched, and the thickness of the solid rib is less than the total thickness of the base island, but still greater than the thickness of the half-etched rib.
[0038] In one embodiment, when the thickness of the solid rib 4 is equal to the thickness of the base island 1, the back of the solid rib 4 is flush with the back of the base island, and the total area of the back of the solid rib 4, the back of the base island 7, and the back of the pin 2 is greater than or equal to 30% of the total area of the back of the lead frame structure, and after verification, the exposed solid area (the total area of the back of the solid rib, the back of the base island, and the back of the pin) is ≥30% of the total area of the back of the lead frame structure, the problem of film-paper separation can be effectively solved, and the generation of air bubbles in the product during the plastic sealing process can be avoided.
[0039] In practical use, the lead frame structure is set on the bottom film, and the lower surface of the lead frame structure is in contact with the bottom film. The solid ribs 4 increase the exposed solid area of the lead frame structure. At the same time, the area of the exposed solid (solid ribs, base islands and pins) on the back of the lead frame structure connected to the bottom film also increases. The bonding force between the lead frame structure and the bottom film is enhanced, thereby solving the problem of film-paper separation in the molding process, eliminating the generation of air bubbles in chip molding, and solving the problem that WB (wire bonding) wire bonding easily peels the material layer or pattern off the substrate.
[0040] In one embodiment, the pins 2 include two sets, which are respectively disposed on opposite sides of the base island 1;
[0041] The first rib 31 and the second rib 32 each consist of two parts, which are connected in an alternating manner to form the outer frame structure of the central rib 3.
[0042] In one embodiment, the pin 2 is a pin array structure, comprising a plurality of spaced-apart pins 2.
[0043] In one specific embodiment, the single-sided pin 2 includes four pins 2 spaced apart along the length direction of the first rib 31.
[0044] In another embodiment, the single-sided pin 2 includes eight pins 2 spaced apart along the length of the first rib 31.
[0045] In another embodiment, there is only one set of pins, located only on one side of the base island, and there is only one first rib, which is located on the side with the pins and connected to the pins. The second ribs are located on the three sides of the lead frame body without pins.
[0046] In one embodiment, a connecting rib 33 is further included, with its two ends connected to the base island 1 and the second rib 32, respectively.
[0047] In one specific embodiment, at least two connecting ribs 33 are connected to the second rib 32 on one side.
[0048] In one embodiment, the connecting rib 33 is a semi-etched rib and is connected to the semi-etched rib in the second rib 32.
[0049] In this embodiment, the second rib region corresponding to the position between the pin and the base island is a solid rib, and the remaining region of the second rib is a semi-etched rib.
[0050] In other embodiments, the area of the solid rib can also be increased. The area of the second rib corresponding to the position between the first rib on one side of the pin and the base island is a solid rib, and the remaining area of the second rib is a semi-etched rib. This can both facilitate the cutting process of the DFN frame structure and enhance the support and fracture resistance of the lead frame structure.
[0051] The lead frame structure also includes an insulating layer 5 that fills the area between the base island 1, the pin 2 and the central rib 3, and the corresponding gaps of the semi-etched ribs. The material of the insulating layer 5 is a molding compound.
[0052] In one embodiment, the solid rib 4 of the second rib 32 has insulating layers 5 on both sides, so there will be no problem of excessive cutting burrs. Even if the corresponding position between the pin 2 and the base island 1 is completely encapsulated, the second rib 32 at the corresponding position is reinforced. During the handling or film removal process, the second rib of the lead frame is not prone to vertical through-cracks at the position between the pin 2 and the base island 1.
[0053] Because cutting the metal lead frame structure is difficult, the lead frame structure located around the product encapsulation line 6 is thinned before the DFN product undergoes the cutting process. Meanwhile, since the solid rib 4 is located outside the product encapsulation line 6, it is absent from the cut DFN product, thus not affecting the product appearance required by the customer.
[0054] In another embodiment, in conjunction with reference Figure 3 , Figure 3 This is a bottom view of the lead frame structure in another embodiment of this application. The first rib 31 has a solid reinforcing rib 8 in the middle. The solid reinforcing rib 8 can be used to increase the exposed area of the middle rib 3, reduce the problem of film-paper separation in the molding process, and the solid reinforcing rib 8 also increases the stability and strength of the frame, so that the frame can reduce shaking during the production line operation, thereby improving the performance of the product.
[0055] Although this application has been disclosed above with reference to preferred embodiments, it is not intended to limit this application. Any person skilled in the art can make possible changes and modifications to the technical solutions of this application by utilizing the methods and techniques disclosed above without departing from the spirit and scope of this application. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this application without departing from the content of the technical solutions of this application shall fall within the protection scope of the technical solutions of this application.
Claims
1. A lead frame structure, characterized in that, include: A lead frame body, the lead frame body including a base island and pins, the base island being located in the middle of the lead frame body for fixing a chip, and the pins being disposed on at least one side of the base island; A central rib is provided around the lead frame body. The central rib includes a first rib and a second rib that are connected to each other. The first rib is located on the side of the lead frame body with pins and is connected to the pins. The second rib is located on the side of the lead frame body without pins. The second rib area corresponding to the position between the pin and the base island is a solid rib, and the remaining area of the second rib is a semi-etched rib.
2. The lead frame structure as described in claim 1, characterized in that, The first rib is a semi-etched rib.
3. The lead frame structure as described in claim 2, characterized in that, The first rib has a solid reinforcing rib in the middle.
4. The lead frame structure as described in claim 1, characterized in that, The thickness of the solid rib is less than or equal to the thickness of the base island, but greater than the thickness of the semi-etched rib.
5. A lead frame structure as described in claim 1, characterized in that, The thickness of the solid rib is equal to the thickness of the base island, the back of the solid rib is flush with the back of the base island, and the total area of the back of the solid rib, the back of the base island and the back of the pin is greater than or equal to 30% of the total area of the back of the lead frame structure.
6. The lead frame structure as described in claim 1, characterized in that, The pins include two sets, which are respectively located on opposite sides of the base island; The first rib and the second rib each consist of two parts, which are sequentially and alternately connected to form the outer frame structure of the central rib.
7. A lead frame structure as described in claim 1, characterized in that, It also includes connecting ribs, the two ends of which are connected to the base island and the second rib body, respectively.
8. A lead frame structure as described in claim 7, characterized in that, The connecting rib is a semi-etched rib and is connected to the semi-etched rib in the second rib.
9. A lead frame structure as described in claim 1, characterized in that, It also includes an insulating layer that fills the area between the base island, pins and center ribs, and the corresponding gaps of the semi-etched ribs.
10. A lead frame structure as described in claim 9, characterized in that, The two sides of the solid rib of the second rib are insulating layers.
11. A lead frame structure as described in claim 1, characterized in that, The pins are a pin array structure, containing multiple pins spaced apart.
12. A lead frame structure as described in claim 1, characterized in that, The lead frame structure is a DFN lead frame structure.