A thick material-based to-252 lead frame and a packaging structure thereof

Abstract

The utility model relates to a kind of TO-252 lead frame and packaging structure based on thick material, lead frame includes frame body, frame body has several array arrangement encapsulation unit, encapsulation unit includes base island, first pin and two second pins, first pin is connected with base island, two second pins are distributed in the two sides of first pin;Encapsulation unit has glue locking structure, glue locking structure is at least distributed in second pin, glue locking structure includes glue locking hole, glue injection well and flow guide groove, glue locking hole and glue injection well are along vertical horizontal direction layout, and pass through the upper and lower surfaces of encapsulation unit, flow guide groove is communicated with the lower end of glue locking hole and glue injection well.This technical solution can realize three-dimensional anchoring through glue locking structure after solidification of molten state packaging material, while reducing the micro-cracks and expansion induced by the alternating change of power device operating temperature, and further ensure the long-term reliability of power device operation.

Description

Technical Field

[0001] This utility model relates to the field of power module technology, and more specifically to a TO-252 lead frame based on thick material and its packaging structure. Background Technology

[0002] Semiconductor packaging technology is a key manufacturing process for electronic components that electrically connects, physically protects, and heats up bare chips after wafer dicing, and forms them into a standardized shape to achieve functional integration and reliable application.

[0003] As the core carrier in semiconductor packaging, the lead frame provides mechanical support, electrical interconnection and heat dissipation channels for the chip, while also forming the standard pin structure outside the package. The TO-252 lead frame is a typical type among many standard package lead frames, mainly used for surface mount power device packaging.

[0004] The TO-252 leadframe includes several packaging units. Each packaging unit consists of a base island, a first pin, and two second pins. The first pin connects to the base island, and the two second pins are independent pins. In the packaging process, after the TO-252 leadframe is bonded, it needs to be encapsulated by injection molding. Molten packaging material (usually epoxy resin) is injected into the mold cavity to completely cover the chip, bonding wires, and the connection parts of the leadframe. After curing, a protective shell with a predetermined shape and physical properties is formed. In order to enhance the bonding force between the TO-252 leadframe and the epoxy resin and prevent the leadframe from shifting or warping due to resin flow during the packaging process, especially to maintain a stable distance between the base island connecting the first pin and the second pin, a locking structure is usually set on the leadframe. However, this locking structure only includes locking holes, and these holes are straight holes of equal diameter. After the epoxy resin cures, the straight hole walls of the locking holes form a simple columnar interface with the epoxy resin. This not only limits the contact area but also makes it difficult to achieve three-dimensional anchoring, resulting in insufficient anti-delamination ability. At the same time, the shrinkage stress of the epoxy resin during the curing process will be concentrated in a single axial direction. Under the alternating changes in the operating temperature of the power device, microcracks are easily induced and propagated at the interface, which seriously affects the long-term reliability of the power device.

[0005] For example, Chinese patent CN202816920 discloses a TO-252 package lead frame structure, which includes a TO-252 frame with three pins: a center pin and two side pins. The frame portion of the side pins has circular flow holes (equivalent to adhesive locking holes). These locking holes guide epoxy resin to uniformly fill the gaps in the frame, anchoring it to the frame after curing. This improves the bonding strength between the frame and the epoxy resin, effectively suppressing the internal stress caused by resin curing shrinkage and reducing delamination or bubble defects caused by uneven colloid flow.

[0006] As shown in the Chinese Patent with the publication number CN221632562U and the patent title "A TDFN2510-10L Chip Frame Structure", hollowed-out portions are provided on both sides in the width direction of the die pad to form first glue locking holes, four second pins on the same side in the width direction of the die pad form cross-shaped second glue locking holes in the circumferential direction, and the second glue locking holes are in communication with the first glue locking holes; a third glue locking hole is provided at the end of the chip fixing unit in the length direction, and the third glue locking hole is in communication with the second glue locking hole; the first glue locking hole, the second glue locking hole and the third glue locking hole form a king-shaped structure on one side of the die pad. Although the improvement of the shape of the glue locking holes makes the connection between the frame and the encapsulation colloid tighter, overall, the improvement of the glue locking holes is only limited to the shape change in the width direction, the irregular hole pattern mainly generates a unidirectional transverse mechanical engaging force with the encapsulation shell, and the anchoring effect in the vertical direction is poor, so the overall delamination resistance of the lead frame after encapsulation is still insufficient. Content of the Utility Model

[0007] In view of the above situation, in order to overcome the problems that the existing glue locking structure of the TO-252 lead frame is only a straight glue locking hole with equal diameter, which is difficult to achieve three-dimensional anchoring after epoxy resin curing, resulting in insufficient delamination resistance, and under the alternating change of the working temperature of the power device, microcracks are easily induced at the interface to generate and propagate, which affects the reliability of the power device, the purpose of the present utility model is to provide a TO-252 lead frame and the encapsulation structure thereof, which can realize three-dimensional anchoring after epoxy resin curing, reduce the microcracks and propagation induced by the alternating change of the working temperature of the power device, so as to ensure the long-term reliable operation of the power device.

[0008] In order to achieve the above purpose, the technical solution of the present utility model is as follows:

[0009] A TO-252 lead frame based on thick material comprises a frame body, the frame body is provided with a plurality of encapsulation units arranged in an array, each encapsulation unit comprises a die pad, a first pin and two second pins, the first pin is connected with the die pad, and the two second pins are distributed on two sides of the first pin;

[0010] The encapsulation unit is provided with a glue locking structure, the glue locking structure is at least distributed on the second pins, the glue locking structure comprises glue locking holes, glue injection wells and flow guide grooves, the glue locking holes and the glue injection wells are arranged along the vertical horizontal direction and penetrate through the upper and lower surfaces of the encapsulation unit, and the flow guide grooves are communicated with the lower ends of the glue locking holes and the glue injection wells;

[0011] The locking hole includes an upper hole section, a lower hole section, and a side hole section. The vertical projection of the upper hole section on the reference plane is smaller than the vertical projection of the lower hole section on the reference plane, and they at least partially overlap. The side hole section laterally penetrates the lower hole section. The guide groove is connected to the lower hole section. The upper hole section and the lower hole section are respectively connected to the upper and lower surfaces of the packaging unit.

[0012] Preferably, the vertical projection area of ​​the upper hole segment on the reference plane is smaller than the vertical projection area of ​​the lower hole segment on the reference plane, and the upper hole segment completely coincides with the vertical projection of the lower hole segment on the reference plane.

[0013] Preferably, the upper opening of the injection well and the upper section opening of the locking hole are both flared.

[0014] Preferably, the glue-locking structure is also distributed on the base island, and the upper and lower ends of the glue-locking holes and glue injection wells of the glue-locking structure are respectively connected to the upper and lower surfaces of the base island.

[0015] Preferably, the locking structures distributed on the base island are in multiple sets and arranged sequentially along the diagonal of the base island.

[0016] Preferably, the thickness of the frame body is 0.65 to 0.8 mm.

[0017] Preferably, the packaging unit also includes a heat sink, which is connected to the base island, and a stress dispersion hole is provided at the junction of the heat sink and the base island, with dovetail grooves provided on the left and right sides of the stress dispersion hole.

[0018] A packaging structure includes the aforementioned TO-252 lead frame, and further includes a plastic encapsulation shell, a copper-clad laminate, a chip, and bonding wires. The copper-clad laminate is disposed inside the plastic encapsulation shell. The base island of the frame body and the tail ends of the second pin are soldered to the copper-clad laminate. The chip is soldered to the base island. The chip is bonded to the tail ends of the second pin through bonding wires. The front ends of the first pin and the second pin extend through the plastic encapsulation shell to the external space and are bent.

[0019] Preferably, it also includes a heat dissipation substrate, and a heat dissipation cavity is formed at the bottom of the plastic-encapsulated housing, with the heat dissipation substrate embedded in the heat dissipation cavity.

[0020] Compared with the prior art, the advantages of this utility model are:

[0021] The locking holes, injection wells, and guide channels of the sealing structure are located at different heights, forming a hierarchical distribution, and are connected to form a U-shaped flow channel. During subsequent encapsulation, molten encapsulation material is simultaneously injected from the locking holes and injection wells into the guide channels to achieve a gradient release of flow pressure, avoiding stress concentration. After the encapsulation material solidifies and cools, it forms a plastic encapsulation shell. The plastic encapsulation shell has embedded snaps that match the shape of the U-shaped flow channel. These snaps include a first snap body that mates with the locking holes, a second snap body that mates with the injection wells, and a third snap body that mates with the guide channels, thereby significantly increasing the contact area with the encapsulation unit and achieving three-dimensional anchoring. The first and second snap bodies and the third snap body... The transition between the two parts avoids the concentration of shrinkage stress in a single axial direction during the curing process of the encapsulation material. Axial constraint is achieved through the mechanical stop of the upper encapsulation unit. The cooperation of the first and second locking bodies with the locking hole and the injection well creates an interlock between the plastic encapsulation shell and the encapsulation unit. This further suppresses encapsulation delamination and prevents axial displacement and circumferential deflection of the plastic encapsulation shell, significantly improving anti-delamination capability. It solves the problem of microcracks being induced and propagating at the interface under the alternating temperature changes of power devices after encapsulation. This ensures that the encapsulation unit of the encapsulation unit is stably clamped by the plastic encapsulation shell body, ensuring the long-term reliability of the power device. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the TO-252 lead frame of this utility model; Figure 2 This is a partial structural schematic diagram of one of the packaging units of the TO-252 lead frame of this utility model; Figure 3 This is a partial structural schematic diagram of one of the packaging units of the TO-252 leadframe of this utility model (only the perspective of the locking structure on the second pin is shown, and the vertical projection of the lower hole section of the locking hole completely covers the upper hole section). Figure 4 This is a utility model Figure 3 A partial cross-sectional view of the second pin of the middle packaging unit (the arrow indicates the injection direction of the molten packaging material); Figure 5 This is a partial structural schematic diagram of one of the packaging units of the TO-252 leadframe of this utility model (only the perspective of the locking structure on the second pin is shown, and the vertical projection of the lower hole section of the locking hole partially overlaps with the upper hole section). Figure 6 This is a utility model Figure 5 A partial cross-sectional view of the second pin of the middle packaging unit (the arrow indicates the injection direction of the molten packaging material); Figure 7 This is a schematic diagram of the internal structure of the power module after the TO-252 lead frame of this utility model is packaged and formed.

[0023] As shown in the figure:

[0024] 100. Frame body; 200. Packaging unit; 21. Base island; 22. First pin; 23. Second pin; 2a. Locking structure; 24. Locking hole; 24a. Upper hole section; 24b. Lower hole section; 24c. Side hole section; 24d. Flaring; 25. Glue well; 26. Heat sink; 27. Stress dispersion hole; 28. Dovetail groove; 29. ​​Guide groove; 300. Molded shell; 31. Heat dissipation cavity; 400. Copper clad laminate; 500. Chip; 600. Bonding wire; 700. Heat dissipation substrate. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application and how they solve the aforementioned technical problems will be clearly and completely described below with reference to specific embodiments and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0026] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0027] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and 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.

[0028] The terms "first," "second," "third," "fourth," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0029] In this application, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0030] As mentioned in the background section, the TO-252 leadframe is a standard packaging leadframe. During the packaging process, the dynamic pressure generated during the flow of the molten packaging material and the shrinkage stress after solidification and cooling can easily cause the leadframe to shift or warp. To address this, a locking structure 2a is usually provided on the leadframe. Conventional TO-252 leadframes typically use locking holes 24 as their locking structure 2a. The locking holes 24 are straight holes of equal diameter. After the molten packaging material solidifies, the straight hole wall of the locking hole 24 forms a simple columnar interface with the packaging material. This not only limits the contact area but also makes it difficult to achieve three-dimensional anchoring, resulting in insufficient anti-delamination capability. At the same time, the shrinkage stress will be too concentrated during the solidification process. Under the alternating temperature changes of the power device, it is easy to induce the generation and propagation of microcracks at the interface, which seriously affects the long-term reliability of the power device.

[0031] like Figure 1 As shown, based on this, this application provides a TO-252 lead frame based on thick material. Its basic structural features, such as frame shape and pin layout, are consistent with conventional lead frames of the same type and conform to the TO standard shape specification. More specifically, it includes a frame body 100, which has several packaging units 200 arranged in an array inside the frame body 100. Each packaging unit 200 includes a base island 21 for carrying a semiconductor chip 500, a first pin 22 connected to the base island 21, and second pins 23 symmetrically distributed on both sides of the base island 21. The first pin 22 is a drain pin, and the second pins 23 are independent pins, namely a source pin and a gate pin. The first pin 22 and the two second pins 23 are connected by internal connecting ribs. The second pins 23 of adjacent packaging units 200 are connected across units by external connecting ribs, thereby forming a structurally stable lead frame and ensuring the mechanical positioning accuracy of each packaging unit 200 during the punching and packaging process.

[0032] like Figures 2 to 6 As shown, the packaging unit 200 has a locking structure 2a. Since the second pin 23, which is an independent pin, lacks mechanical connection with the adjacent base island 21, it is susceptible to positional displacement or warping due to the pressure generated by the flow of molten packaging material during packaging. Therefore, the locking structure 2a is distributed at least on the second pin 23, which is an independent pin.

[0033] The locking structure 2a includes a locking hole 24, a filling well 25, and a flow channel 29. The locking hole 24 and the filling well 25 are arranged in a direction perpendicular to the horizontal plane, and the upper and lower ends of the locking hole 24 and the filling well 25 respectively penetrate the upper and lower surfaces of the packaging unit 200. Depending on the arrangement, the upper and lower ends of the locking hole 24 and the filling well 25 penetrate the upper and lower surfaces of the second pin 23, or penetrate the upper and lower surfaces of other parts of the packaging unit 200. The flow channel 29 is connected to the locking hole 24 and the filling well 25. Since the entire lead frame is a thin sheet structure, the flow channel 29 cannot be pre-embedded inside the packaging unit 200. Therefore, the flow channel 29 is opened on the lower surface of the packaging unit 200. The lower surface referred to here can be the lower surface of the second pin or other parts of the packaging unit, and it is connected to the lower end of the locking hole 24 and the filling well 25. Molten packaging material can be injected into the flow channel 29 simultaneously through the locking hole and the filling well.

[0034] Overall, the locking holes 24, injection wells 25, and guide channels 29 are located at different heights, forming a hierarchical distribution, and are connected to form a U-shaped flow channel. During the subsequent encapsulation process, the molten encapsulation material is simultaneously injected into the guide channels 29 from the locking holes 24 and injection wells 25 to achieve a gradient release of flow pressure, avoiding stress concentration. After the encapsulation material solidifies and cools, it forms a plastic encapsulation shell 300. The plastic encapsulation shell 300 has embedded snaps that match the shape of the U-shaped flow channel. These snaps include a first snap body that mates with the locking holes 24, a second snap body that mates with the injection wells 25, and a third snap body that mates with the guide channels 29, thereby significantly increasing the contact area with the encapsulation unit and achieving three-dimensional anchoring. The first and second snap bodies and the third snap body form a transition. To avoid the concentration of shrinkage stress in a single axial direction during the curing process of the encapsulation material, and to achieve axial constraint through the mechanical stop of the upper encapsulation unit 200 (second pin 23 or other parts), the cooperation of the first and second locking bodies with the locking hole 24 and the injection well 25 makes the plastic encapsulation shell 300 and the encapsulation unit 200 interlocked, thereby further suppressing the encapsulation delamination phenomenon and preventing the axial displacement and circumferential deflection of the plastic encapsulation shell 300, significantly improving the anti-delamination ability, and solving the problem that microcracks are easily induced and propagated at the interface under the alternating temperature changes of the power device after encapsulation. This ensures that the encapsulation unit 200 is stably clamped by the main body of the plastic encapsulation shell 300, ensuring the long-term reliability of the power device.

[0035] In addition, it should be mentioned that the injection well 25 adds a path for the molten encapsulation material to be injected into the lower hole section 24b. The molten encapsulation material can be injected into the guide channel 29 through two independent paths, the upper hole section 24a and the injection well 25. This not only significantly shortens the filling time of the guide channel 29, but also ensures that the encapsulation material is fully filled at the end of the flow. This improves the encapsulation efficiency and effectively avoids defects at the interlocking interface caused by insufficient filling.

[0036] like Figure 2 , Figure 3 and Figure 5 As shown, in one embodiment, the locking holes 24 are distributed on the second pin 23, which is an independent pin. The mortise formed after the molten material is injected and solidified will maintain a stable distance between the second pin 23 and the first pin 22 and the base island 21. The upper and lower ends of the locking holes 24 and the injection wells 25 are respectively connected to the upper and lower surfaces of the second pin 23, thereby extending the length of the formed mortise and further increasing the contact area between the molding compound and the pin. This allows the mortise to form a continuous anchor in the axial direction, effectively suppressing the risk of misalignment caused by material flow pressure during the packaging process.

[0037] like Figures 2 to 5 As shown, the locking hole 24 is a composite hole composed of three parts: an upper hole section 24a, a lower hole section 24b, and a side hole section 24c. The upper hole section 24a and the lower hole section 24b are vertically connected and pass through the upper and lower surfaces of the packaging unit 200, respectively. The vertical projection of the upper hole section 24a on the reference plane is smaller than the vertical projection of the lower hole section 24b on the reference plane, and they at least partially overlap. That is to say, the diameter of the upper hole section 24a is smaller than that of the lower hole section 24b. Thus, a step position will be formed at the junction of the upper hole section 24a and the lower hole section 24b. This step position is defined as the first step position. The guide groove 29 is connected to the lower hole section 24b.

[0038] like Figure 5 and Figure 6 As shown, in one embodiment, the central axis of the upper hole segment 24a is not collinear with the central axis of the lower hole segment 24b, that is, the upper hole segment 24a and the lower hole segment 24b are misaligned, so that the joint forms a first step position of turning. The side hole segment 24c is located outside the lower hole segment 24b and laterally penetrates the lower hole segment 24b, so that the cross-sectional shape of the lower hole segment 24b is non-circular.

[0039] In the forming process, the present invention specifically selects a frame body 100 with a thickened base material to ensure that sufficient material allowance is provided for the upper hole section 24a and the lower hole section 24b when performing axial depth machining of the locking hole, reducing the deformation generated during the stamping process of the frame body 100, and improving the forming quality of the punched section, thereby ensuring the accuracy of the upper hole section 24a and the lower hole section 24b as well as the smoothness of the first step at the transition.

[0040] The first buckle body formed during the subsequent encapsulation process includes an upper buckle body that mates with the upper hole section 24a, a lower buckle body that mates with the lower hole section 24b, and a limiting protrusion formed by the side hole section 24c. The diameter of the upper buckle body is smaller than that of the lower buckle body, and a transition step is formed at the joint between the two. A second step is defined at this step. The first step of the locking hole 24 abuts against the second step of the buckle, forming a stepped fit that provides axial support for the encapsulation unit 200. Combined with the downward pressure of the plastic encapsulation shell 300 body, it forms a bidirectional clamping effect on the encapsulation unit 200, thereby limiting its radial and axial displacement. The limiting protrusion makes the cross-section of the lower buckle body appear as... When the non-circular shape mates with the lower hole section 24b of the connecting side hole section 24c, it effectively suppresses the circumferential sway of the packaging unit 200. In addition, the transition between the first step and the second step increases the contact area between the locking hole 24 and the buckle, achieving three-dimensional anchoring, significantly improving the anti-delamination capability, and avoiding the concentration of shrinkage stress in a single axial direction during the curing process of the packaging material. This solves the problem of the generation and propagation of microcracks at the interface under the alternating temperature changes of the power device after packaging, so that the packaging unit 200 is stably clamped between the second step and the main body of the plastic shell 300, ensuring the long-term reliability of the power device.

[0041] like Figure 3 and Figure 4 As shown, in another real-time mode, the vertical projection area of ​​the upper hole segment 24a on the reference plane is smaller than the vertical projection area of ​​the lower hole segment 24b on the reference plane, and completely coincides with the vertical projection of the lower hole segment 24b on the reference plane. That is to say, when the upper hole segment 24a and the lower hole segment 24b are projected axially onto the same reference plane, the projection of the upper hole segment 24a is completely contained within the projection range of the lower hole segment 24b, and the two projection areas completely overlap, thus synchronously forming a transition step of the first step position at the joint.

[0042] like Figure 4 and Figure 6 As shown, the upper opening of the injection well 25 and the upper hole section 24a opening of the locking hole 24 are both tapered flares 24d, meaning their cross-sections are inclined flow guide surfaces. During the encapsulation process, they act as flow guide surfaces, causing the molten encapsulation material to generate a directional flow effect when it contacts the flares 24d, effectively reducing the material injection resistance. At the same time, the flares 24d of the upper hole section 24a and the flares 24d corresponding to the injection well 25 will increase the filling rate of the molten encapsulation material per unit time, thereby ensuring the rapid and uniform filling of the locking hole 24.

[0043] like Figure 2 , Figure 3 and Figure 5As shown, in one embodiment, the locking structure 2a is also distributed on the base island 21. The locking hole 24 and the injection well 25 of the locking structure 2a are respectively connected to the upper and lower surfaces of the base island 21. During encapsulation, a three-dimensional snap is formed at the position of the base island 21, which significantly improves the anti-delamination ability and avoids the shrinkage stress of the encapsulation material during the curing process from concentrating in a single axial direction, so that the base island 21, the first pin 22 and the second pin 23 maintain a fixed distance, thereby improving the reliability of the power device after encapsulation.

[0044] like Figure 2 , Figure 3 and Figure 5 As shown, the locking structure 2a distributed on the base island 21 has multiple sets, and each set of locking structure 2a is arranged sequentially along the diagonal of the base island 21. The buckles formed after the encapsulation material is cured will also be evenly distributed along the diagonal of the base island 21 to achieve interlocking strength between the buckles and the base island 21. This ensures that the base island 21, the first pin 22 and the second pin 23 maintain a precise relative position during the encapsulation process and after the interlocking encapsulation is completed. Therefore, it is suitable for power device encapsulation with high reliability requirements.

[0045] Furthermore, the lead frame is made of 0.65 to 0.8 mm thick material and uses step-by-step stamping to form locking holes to reduce the risk of hole wall deformation and microcracks.

[0046] like Figure 2 , Figure 3 and Figure 5 As shown, the packaging unit 200 also includes a heat sink 26, which is connected to the base island 21. A stress-dispersing hole 27 is provided at the junction of the heat sink 26 and the base island 21. Dovetail grooves 28 are provided on the left and right sides of the stress-dispersing hole 27. During packaging, the heat sink 26 extends to the outside of the cured plastic package 300. As an exposed heat dissipation structure, it will provide heat dissipation for the chip 500 soldered on the base island 21. The stress-dispersing hole 27 and the dovetail grooves 28 can disperse the stress caused by the shrinkage and curing of the packaging material during the subsequent packaging process, thereby improving the bonding force between the lead frame and the plastic package 300 and improving the reliability and service life of the power module.

[0047] like Figure 7As shown, this application also relates to a packaging structure having the aforementioned TO-252 lead frame, characterized in that it further includes a plastic encapsulation shell 300, a copper-clad laminate 400, a chip 500, and bonding wires 600. The copper-clad laminate 400 is disposed inside the plastic encapsulation shell 300. The base island 21 and the tail ends of the second pin 23 of the frame body 100 are soldered to the copper-clad laminate 400, thus also being encapsulated within the plastic encapsulation shell 300. The chip 500 is soldered to the base island 21. It should be noted that a metal plating layer is formed on the surface of the base island 21 through an electroplating process. The plating layer is preferably a silver layer or a nickel-containing composite layer, configured according to the soldering process requirements. The plating provides the metallurgical bonding interface required for welding the chip 500, ensuring welding strength and good thermal conductivity. The chip 500 is bonded to the tail end of the second pin 23 via the bonding wire 600. After the lead frame is welded to the copper-clad laminate 400, it is placed into the cavity of the injection mold, and molten encapsulation material is injected into the cavity. After the encapsulation material solidifies, it forms a rigid plastic shell 300, which provides protection for the chip 500, the base island 21, the first pin 22, the second pin 23, and the bonding wire 600. The front ends of the first pin 22 and the second pin 23 extend through the plastic shell 300 into the external space and are bent.

[0048] like Figure 7 As shown, it also includes a heat dissipation substrate 700, which is connected to the plastic package 300 and adjacent to the copper clad laminate 400. More specifically, the bottom of the plastic package 300 is provided with a heat dissipation cavity 31 that is adapted to the shape of the heat dissipation substrate 700. The heat dissipation substrate 700 is embedded in the heat dissipation cavity 31 and fixed to the plastic package 300. The copper clad laminate 400 is located on the other side of the heat dissipation cavity 31. The heat generated by the chip 500 during operation can also be exchanged with the external space through the following heat conduction path, namely, through the base island 21, the copper clad laminate 400, and the plastic package 300, and finally transferred to the heat dissipation substrate 700, thereby achieving efficient heat dissipation and significantly improving the thermal management performance of the power module.

[0049] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this application can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this application can be achieved, and this is not limited herein.

[0050] The embodiments and descriptions above are merely illustrative of the principles and preferred embodiments of this application. Various changes and modifications may be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed.

Claims

1. A TO-252 lead frame based on thick material, comprising a frame body (100), the frame body (100) having a plurality of package units (200) arranged in an array, the package unit (200) comprising a base island (21), a first pin (22) and two second pins (23), the first pin (22) being connected to the base island (21), and the two second pins (23) being distributed on both sides of the first pin (22); The encapsulation unit (200) has a locking structure (2a), characterized in that, The glue-locking structure (2a) is distributed at least on the second pin (23). The glue-locking structure (2a) includes a glue-locking hole (24), a glue injection well (25), and a flow guide groove (29). The glue-locking hole (24) and the glue injection well (25) are arranged in a vertical and horizontal direction and penetrate the upper and lower surfaces of the packaging unit (200). The flow guide groove (29) is connected to the lower end of the glue-locking hole (24) and the glue injection well (25). The locking hole (24) includes an upper hole section (24a), a lower hole section (24b), and a side hole section (24c). The vertical projection of the upper hole section (24a) on the reference plane is smaller than the vertical projection of the lower hole section (24b) on the reference plane, and they at least partially overlap. The side hole section (24c) laterally penetrates the lower hole section (24b). The guide groove (29) is connected to the lower hole section (24b). The upper hole section (24a) and the lower hole section (24b) are respectively connected to the upper and lower surfaces of the packaging unit (200).

2. The TO-252 lead frame based on thick material according to claim 1, characterized in that, The vertical projection area of ​​the upper hole segment (24a) on the reference plane is smaller than the vertical projection area of ​​the lower hole segment (24b) on the reference plane, and completely coincides with the vertical projection of the lower hole segment (24b) on the reference plane.

3. A TO-252 lead frame based on thick material according to claim 2, characterized in that, The upper opening of the glue injection well (25) and the upper hole section (24a) of the glue locking hole (24) are both flared (24d).

4. A TO-252 lead frame based on thick material according to claim 1, characterized in that, The glue-locking structure (2a) is also distributed on the base island (21), and the upper and lower ends of the glue-locking hole (24) and the glue injection well (25) of the glue-locking structure (2a) are respectively connected to the upper and lower surfaces of the base island (21).

5. A TO-252 lead frame based on thick material according to claim 4, characterized in that, The base island (21) has multiple sets of locking structures (2a) arranged sequentially along the diagonal of the base island (21).

6. A TO-252 lead frame based on thick material according to claim 1, characterized in that, The thickness of the frame body (100) is 0.65 to 0.8 mm.

7. A TO-252 lead frame based on thick material according to claim 1, characterized in that, The encapsulation unit (200) also includes a heat sink (26), which is connected to the base island (21), and a stress dispersion hole (27) is provided at the junction of the heat sink (26) and the base island (21). Dovetail grooves (28) are provided on the left and right sides of the stress dispersion hole (27).

8. A packaging structure comprising the TO-252 lead frame as described in any one of claims 1 to 7, characterized in that, It also includes a plastic encapsulation shell (300), a copper-clad laminate (400), a chip (500), and bonding wires (600). The copper-clad laminate (400) is disposed inside the plastic encapsulation shell (300). The base island (21) and the tail end of the second pin (23) of the frame body (100) are soldered to the copper-clad laminate (400). The chip (500) is soldered to the base island (21). The chip (500) is bonded to the tail end of the second pin (23) through the bonding wires (600). The front ends of the first pin (22) and the second pin (23) extend through the plastic encapsulation shell (300) to the external space and are bent.

9. The packaging structure according to claim 8, characterized in that, It also includes a heat dissipation substrate (700), and a heat dissipation cavity (31) is provided at the bottom of the plastic encapsulation shell (300), and the heat dissipation substrate (700) is embedded in the heat dissipation cavity (31).

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