Four-point ultrasonic support positioning three-copper surface double-sided heat dissipation power device and preparation method thereof

Abstract

The application provides a four-point ultrasonic support positioning three-copper-face double-face heat dissipation power device and a preparation method thereof, relates to the field of power semiconductor packaging, and comprises a three-needle lead frame, an aluminum bonding wire, a power chip, a first heat dissipation copper face, double independent outward heat dissipation copper sheets and a heat insulation plastic encapsulation body. The application connects the foot of the lead of the three-needle lead frame to the front surface of the power chip through the aluminum bonding wire, sets the middle part of the double independent outward heat dissipation copper sheets as a plastic encapsulation lettering area, forms a second heat dissipation copper face and a third heat dissipation copper face on the left and right sides, and a plurality of welding positioning holes are formed on the second heat dissipation copper face and the third heat dissipation copper face. The three-copper-face double-face heat dissipation structure improves the heat dissipation efficiency of the power chip, the welding positioning holes reduce the possibility of the double independent outward heat dissipation copper sheets being deviated in the welding process, thereby improving the product qualification rate of the power device, and the aluminum bonding wire reduces the processing cost of the power device.

Description

Technical Field

[0001] This invention relates to the field of power semiconductor packaging, specifically to a power device with four-point ultrasonic support positioning, three copper surfaces, and double-sided heat dissipation, and its fabrication method. Background Technology

[0002] With the rapid development of high-power power electronics fields such as photovoltaic inverters, energy storage converters, industrial frequency converters, and automotive power supplies, the market demands for the heat dissipation performance, high-frequency operating stability, and product yield of high-power devices such as MOSFETs, IGBTs, and silicon carbide are continuously increasing. There are many types of high-power devices; this discussion focuses on the TO247-3L three-pin package. The heat dissipation capacity, electrical performance, and process reliability of the TO247-3L three-pin package directly determine the overall operating performance and lifespan of the power device. Therefore, optimizing the TO247-3L three-pin package process and structure, and addressing packaging shortcomings under high-power conditions, has become a key research focus for those skilled in the art.

[0003] Among related technologies, the TO247-3L three-pin package manufacturing process, which is widely used in the industry, is relatively mature. It mainly includes core processes such as chip mounting, plasma cleaning, wire bonding, molding and curing, pin plating, and final product testing. Specifically, the power chip is first fixed to the pre-set mounting area of ​​the lead frame using solder. Then, a plasma cleaning process is used to remove organic matter, oxides, and other impurities adhering to the surface of the chip and lead frame, ensuring the reliability of subsequent connections. Next, electrical connection between the chip pads and the lead frame pins is achieved through wire bonding. Then, a special molding compound is used to encapsulate the chip, bonding wires, and other core structures. After molding, a heat treatment process is used to ensure complete curing and shaping of the molding compound. Afterward, the device pins are electroplated to improve solderability. Finally, electrical parameter testing is used to screen and eliminate unqualified products, completing the device packaging process. To address the limitations of single-sided heat dissipation in traditional TO247-3L packages, various auxiliary heat dissipation solutions have been developed. The mainstream solutions are mainly divided into two categories: one is the CLIP ultrasonic welding structure, which simultaneously undertakes the dual functions of device conductivity and auxiliary heat dissipation; the other is the independent copper sheet auxiliary heat dissipation structure, which adds an independent copper sheet to enhance the device's heat dissipation capacity while retaining aluminum wires for electrical connection.

[0004] However, the existing TO247-3L three-pin package technology and its corresponding auxiliary heat dissipation solutions still have many unavoidable technical defects, making it difficult to adapt to the operating requirements of high-power, high-frequency devices. First, when the TO247-3L relies solely on the single-sided heat dissipation copper surface on the back, heat cannot be dissipated upwards under high-power, high-frequency switching conditions, leading to a continuous increase in junction temperature and potential thermal fatigue failure due to prolonged high temperatures. Second, when using a CLIP ultrasonic welding structure, where the CLIP simultaneously performs both conductivity and heat dissipation, the CLIP requires dedicated stamping dies and electroplating processes, resulting in high material costs. Furthermore, the longer current loop length leads to higher parasitic inductance, which is detrimental to the switching performance of high-frequency devices. Finally, when using independent copper sheets for heat dissipation and aluminum wire conductivity, the copper sheets can float freely during ultrasonic vibration, easily resulting in forward / backward, left / right, and vertical warping. This can cause voids and poor solder joints at the welding interface, leading to uneven pressure distribution when the solder head is pressed down, and even causing thin power chips to crack, reducing product yield. Summary of the Invention

[0005] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a power device with four-point ultrasonic support positioning, three copper surfaces, and double-sided heat dissipation, as well as its fabrication method. This solves the problems of existing packaged semiconductors having a single heat dissipation channel, insufficient heat dissipation capacity, high cost of front-side heat dissipation CLIP structures, and the free floating of the heat dissipation copper sheets during ultrasonic welding, resulting in front-back, left-right, and up-down warping.

[0006] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a power device with four-point ultrasonic support positioning, three copper surfaces and double-sided heat dissipation, including a three-pin lead frame, aluminum bonding wires, a power chip, a first heat dissipation copper surface, two independent outward heat dissipation copper sheets and a heat insulation plastic encapsulation. The lower surface of the power chip is connected to the first heat dissipation copper surface, and the first heat dissipation copper surface is connected to the three-pin lead frame. The pin roots of the three-pin lead frame are connected to the upper surface of the power chip via the aluminum bonding wires, which cross the first heat dissipation copper surface. The upper surface of the power chip is connected to the lower surface of the dual independent outward heat dissipation copper sheets; The upper surface of the dual independent outward heat dissipation copper sheet is provided with a plastic seal printing area, a second heat dissipation copper surface and a third heat dissipation copper surface. The plastic seal printing area is located in the middle area of ​​the upper surface of the dual independent outward heat dissipation copper sheet. The second heat dissipation copper surface and the third heat dissipation copper surface are respectively located on both sides of the plastic seal printing area. Welding positioning holes are opened on both the second heat dissipation copper surface and the third heat dissipation copper surface. The thermal insulation molding compound covers the power chip, the aluminum bonding wire, the pin roots of the three-pin lead frame, and the molding printing area; The surfaces of the first heat dissipation copper surface, the second heat dissipation copper surface, and the third heat dissipation copper surface are all exposed to the external environment.

[0007] Preferably, the total number of welding positioning holes is four, with two welding positioning holes respectively opened on the second heat dissipation copper surface and the third heat dissipation copper surface.

[0008] Preferably, the device model, electrical parameters, and production batch are laser-marked or screen-printed on the plastic seal printing area.

[0009] Preferably, the power device is a TO247-3L power device.

[0010] Preferably, the heat-insulating encapsulant is epoxy resin.

[0011] Secondly, the present invention provides a method for fabricating a power device with four-point ultrasonic support positioning and three copper surfaces for double-sided heat dissipation as described above, comprising: S1. Lead frame processing: The three-pin lead frame of standard TO247-3L is integrally stamped and formed from pure copper strip. The first heat dissipation copper surface is integrally formed, and the surface of the first heat dissipation copper surface is successively plated with nickel and gold to complete the anti-oxidation treatment. S2. Chip die bonding: The lower surface of the power chip is bonded and fixed to the first heat dissipation copper surface by using a soldering or silver sintering process, and solidified to form a back heat-conducting bonding layer. S3, Aluminum wire bonding: The gate, source, and drain of the power chip on the upper surface are connected to the three pins of the three-pin lead frame via the aluminum bonding wires. S4. Prefabrication of dual independent outward heat dissipation copper sheets: The dual independent outward heat dissipation copper sheets are obtained by stamping pure copper plates and forming the welding positioning holes by stamping the four corners. The central area is polished as the plastic seal printing area. The left and right sides are stretched and widened to form the second heat dissipation copper surface and the third heat dissipation copper surface. The welding area on the lower surface of the dual independent outward heat dissipation copper sheets is roughened. S5, Four-point self-supporting ultrasonic welding: The semi-finished product with aluminum wire bonding is placed in the ultrasonic welding station. The double independent outward heat dissipation copper sheet is supported and limited by the four welding positioning holes at the four corners. The ultrasonic welding head is directly pressed down onto the upper surface of the double independent outward heat dissipation copper sheet and constant pressure is applied in conjunction with ultrasonic vibration. S6. Partitioned directional molding: The welded semi-finished product is placed into the molding mold and epoxy resin is injected and cured at high temperature; the epoxy resin only fills and wraps the power chip, the aluminum bonding wire, the three pin roots of the three-pin lead frame and the molding printing area of ​​the dual independent outward heat dissipation copper sheet, and completely exposes the first heat dissipation copper surface, the second heat dissipation copper surface and the third heat dissipation copper surface. S7. Post-processing and full inspection: After molding, remove burrs and trim and shape the leads. Laser mark the upper surface of the heat-insulating molded body in the area of ​​the molded printing. Then, complete the electrical performance test, withstand voltage test, steady-state thermal resistance test, and appearance inspection in sequence. After passing the inspection, the product is put into storage.

[0012] Preferably, both the pure copper strip and the pure copper plate are made of oxygen-free copper material.

[0013] Preferably, the ultrasonic welding head is provided with a frustum-shaped protrusion corresponding to the welding positioning hole.

[0014] Preferably, the diameter of the lower base of the frustum-shaped protrusion is smaller than the diameter of the upper base.

[0015] Preferably, the maximum outer diameter of the frustum-shaped protrusion is smaller than the diameter of the welding positioning hole.

[0016] (III) Beneficial Effects This invention provides a power device with four-point ultrasonic support positioning, three copper surfaces, and double-sided heat dissipation, as well as its fabrication method. Compared with the prior art, it has the following advantages: First, this invention employs a three-dimensional, double-sided heat dissipation structure with three copper surfaces: a first, a second, and a third. Heat is conducted downwards through the first copper surface, while the second and third copper surfaces simultaneously convect upwards on the left and right sides, forming two independent top heat dissipation areas. The central area between the second and third copper surfaces is covered and isolated by a thermally insulating encapsulation, preventing hot air flowing through the second copper surface from directly reaching the third. This interrupts the formation of a continuous thermal boundary layer, ensuring that both sides can contact air for convective heat transfer. The three parallel heat dissipation paths—bottom conduction and top convection—work synergistically to remove heat from the chip, thereby reducing the steady-state thermal resistance of the power device.

[0017] Secondly, by opening four welding positioning holes on the dual independent outward heat dissipation copper sheets, the present invention provides four-point rigid limiting throughout the welding process, eliminating the need for pressure array tooling. This reduces the possibility of the dual independent outward heat dissipation copper sheets shifting, warping, and poor soldering, thereby evenly distributing the pressure to four points, improving the stability of the welding process, reducing the chip breakage defect rate, and thus improving the pass rate of power devices.

[0018] Third, this invention achieves electrical interconnection between the power chip and the pins of the three-pin lead frame through aluminum wire bonding, which shortens the current loop length, reduces parasitic inductance, and is conducive to improving high-frequency switching performance. The independent copper sheet only undertakes the heat dissipation function, eliminating the need for CLIP-specific molds, stamping, and electroplating processes, simplifying the bill of materials, and effectively reducing the overall packaging manufacturing cost. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A front-view three-dimensional structural diagram of the power device with four-point ultrasonic support positioning, three copper surfaces, and double-sided heat dissipation provided by the present invention. Figure 2 A top-view planar structural diagram of the power device with four-point ultrasonic support positioning, three copper surfaces, and double-sided heat dissipation provided by the present invention. Figure 3 A bottom-view planar structural diagram of the power device with four-point ultrasonic support positioning, three copper surfaces, and double-sided heat dissipation provided by the present invention. Figure 4 A schematic diagram of the main cross-sectional planar structure of the aluminum bonding wire and welding positioning hole provided by the present invention; Figure 5 A schematic diagram of the main cross-sectional planar structure of the aluminum bonding wire, power chip, first heat dissipation copper surface, and heat insulation plastic package provided by the present invention; Figure 6 A front-view three-dimensional structural diagram of the ultrasonic welding head and the two independent outward heat dissipation copper sheets in the fabrication method of the four-point ultrasonic support positioning three-copper-surface double-sided heat dissipation power device provided by the present invention. Figure 7 The schematic diagram of the main view cross-sectional structure of the ultrasonic welding head and the two independent outward heat dissipation copper sheets in the fabrication method of the four-point ultrasonic support positioning three-copper-surface double-sided heat dissipation power device provided by the present invention.

[0021] The above figures include the following reference numerals: 1. Three-pin lead frame; 2. Aluminum bonding wire; 3. Power chip; 4. First heat dissipation copper surface; 5. Dual independent outward heat dissipation copper sheets; 51. Molded printing area; 52. Second heat dissipation copper surface; 53. Third heat dissipation copper surface; 54. Soldering positioning hole; 6. Thermal insulation molding body. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] This application provides a power device with four-point ultrasonic support positioning and three copper surfaces for double-sided heat dissipation, and its fabrication method. This solves the problems of low heat dissipation performance, easy displacement and warping of copper sheets during welding, and high processing cost of CLIP structure power devices in the prior art. It achieves the goals of improving heat dissipation performance, increasing the yield rate of finished power devices, and reducing the processing cost of power devices.

[0024] The technical solution in this application is to solve the above-mentioned technical problems, and the general idea is as follows: This invention improves the heat dissipation performance of power devices by ultrasonically bonding the upper surface of the power chip to two independent outward-facing heat dissipation copper sheets with solderless metal bonding, and connecting the lower surface to the first heat dissipation copper surface, forming a three-copper-surface double-sided heat dissipation architecture. Simultaneously, by setting welding positioning holes on both sides of the heat dissipation surfaces of the two independent outward-facing copper sheets, and combining this with corresponding protrusions on the ultrasonic welding head to achieve four-point support positioning, the position of the copper sheets during the welding process is effectively constrained, preventing them from shifting forward, backward, left, right, or up and down, thereby improving welding accuracy and product qualification rate. Furthermore, by using a one-piece stamped copper sheet to replace the complex bending clamps in the traditional CLIP structure, the processing steps are simplified, and mold and assembly costs are reduced. Moreover, by designing the middle of the two independent outward-facing copper sheets as a plastic-sealed printing area and retaining the two sides as exposed heat dissipation surfaces, the marking function and heat dissipation function do not conflict. While ensuring clear printing of product information, the maximum effective heat dissipation area is maintained, further optimizing the thermal management capabilities of the power devices.

[0025] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0026] See Figure 1 , Figure 2 , Figure 3 and Figure 6 The present invention provides a power device with four-point ultrasonic support positioning, three copper surfaces and double-sided heat dissipation, including a three-pin lead frame 1, aluminum bonding wire 2, power chip 3, first heat dissipation copper surface 4, two independent outward heat dissipation copper sheets 5 and heat insulation plastic encapsulation 6.

[0027] The lower surface of the power chip 3 is connected to the first heat dissipation copper surface 4, and the first heat dissipation copper surface 5 is connected to the three-pin lead frame 1.

[0028] The pin roots of the three-pin lead frame 1 are connected to the upper surface of the power chip 3 via aluminum bonding wires 2 across the first heat dissipation copper surface 5; thereby achieving electrical interconnection and ensuring that the power device has no CLIP conductive interconnect structure.

[0029] The upper surface of the power chip 3 is connected to the lower surface of the dual independent outward heat dissipation copper sheets 5.

[0030] It should be noted that the connection between the dual independent outward heat dissipation copper sheets 5 and the upper surface of the power chip 3 serves only as a heat dissipation conduction path and does not participate in the conductive circuit of the device.

[0031] The upper surface of the dual independent outward heat dissipation copper sheet 5 is provided with a plastic-sealed printing area 51, a second heat dissipation copper surface 52, and a third heat dissipation copper surface 53. The plastic-sealed printing area 51 is located in the middle area of ​​the upper surface of the dual independent outward heat dissipation copper sheet 5. The second heat dissipation copper surface 52 and the third heat dissipation copper surface 53 are respectively located on both sides of the plastic-sealed printing area 51. Welding positioning holes 54 are provided on both the second heat dissipation copper surface 52 and the third heat dissipation copper surface 53.

[0032] Understandably, the dual independent outward heat dissipation copper sheets 5 only serve the function of heat dissipation and do not participate in the conductive interconnection of the power circuit. Therefore, the materials and processes for CLIP stamping and electroplating are eliminated, thereby reducing the packaging production cost.

[0033] The heat-insulating encapsulation 6 covers the pin roots of the power chip 3, aluminum bonding wire 2, three-pin lead frame 1, and the encapsulation printing area 51.

[0034] The surfaces of the first heat dissipation copper surface 4, the second heat dissipation copper surface 52, and the third heat dissipation copper surface 53 are all exposed to the external environment.

[0035] It should be noted that the surfaces of the first heat dissipation copper surface 4, the second heat dissipation copper surface 52, and the third heat dissipation copper surface 53 are completely exposed to air. The second heat dissipation copper surface 52 and the third heat dissipation copper surface 53 form a convection heat dissipation channel during the process of contacting the air.

[0036] It should be noted that the power device with four-point ultrasonic support positioning and three copper surfaces for double-sided heat dissipation relies on the coordinated heat conduction of one metal heat dissipation surface at the bottom and two independent metal heat dissipation surfaces at the top to form a three-dimensional double-sided heat dissipation structure with three copper surfaces.

[0037] See Figure 2As a preferred embodiment of the present invention, the total number of welding positioning holes 54 is four, with two welding positioning holes 54 respectively provided on the second heat dissipation copper surface 52 and the third heat dissipation copper surface 53.

[0038] As a preferred embodiment of the present invention, the four welding positioning holes 54 are respectively distributed at the four corner edges of the double independent outward heat dissipation copper sheet 5. When the ultrasonic welding head presses down, the four welding positioning holes 54 synchronously and evenly distribute the pressure, lock the X, Y, and Z axis displacement of the double independent outward heat dissipation copper sheet 5, and avoid the heat sink tilting and shifting, the welding interface being poorly welded, and the power chip 3 being locally cracked due to pressure.

[0039] The device model, electrical parameters, and production batch are laser-marked or screen-printed on the plastic-sealed printing area 51.

[0040] It should be noted that the surface of the above-mentioned plastic-sealed lettering area 51 is smooth and without protrusions. The heat-insulating plastic sealant 6 fills the plastic-sealed lettering area 51 to achieve a closed shielding, and the plastic-sealed lettering area 51 does not participate in heat dissipation.

[0041] The power device is a TO247-3L power device, which is compatible with existing PCB circuit boards and automated insertion equipment. It can be directly replaced without redesigning the PCB circuit board or adjusting the automated insertion equipment, making the product replacement application threshold low.

[0042] The heat-insulating encapsulation body 6 is made of epoxy resin.

[0043] This invention uses insulating and heat-insulating epoxy resin to form a transverse heat-insulating barrier on the outer surface of the power device. This allows the dual independent outward heat dissipation copper sheets 5 to be exposed only on the left and right sides. Apart from the copper sheet body itself, the inner side is wrapped and sealed by the plastic-encapsulated sidewall. As a result, the heat on the second heat dissipation copper surface 52 only flows to the left and upward with the air, and the heat on the third heat dissipation copper surface 53 only flows to the right and upward with the air. The top surface of the plastic-encapsulated printing area 51 is completely covered by plastic and does not participate in air convection heat dissipation.

[0044] See Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 This invention provides a method for fabricating a power device with four-point ultrasonic support positioning and three copper surfaces for double-sided heat dissipation as described above. The fabrication method specifically includes the following steps: S1. Lead frame processing: The three-pin lead frame 1 of standard TO247-3L is formed by integral stamping of pure copper strip, and the first heat dissipation copper surface 4 is integrally formed. The surface of the first heat dissipation copper surface 4 is plated with nickel and gold in sequence to complete the anti-oxidation treatment. S2. Chip die bonding: Using soldering or silver sintering processes, the lower surface of the power chip 3 is bonded and fixed to the first heat dissipation copper surface 4, and solidified to form a back heat-conducting bonding layer. S3, Aluminum wire bonding: Aluminum bonding wire 2 is used to connect the gate, source, and drain of the upper surface of the power chip 3 to the three pins of the three-pin lead frame 1 to complete all electrical interconnection. No CLIP conductive parts are assembled throughout the process. It should be added that in step S3 above, only aluminum wire is used to achieve electrical interconnection between the chip and the pins, and the independent copper sheet only serves the function of heat dissipation. The CLIP structure is eliminated, thereby eliminating the CLIP-specific mold, stamping, and electroplating processes, so as to simplify the package bill of materials, reduce stamping and electroplating processes, and reduce the overall manufacturing cost.

[0045] S4. Prefabrication of dual independent outward heat dissipation copper sheet 5: The dual independent outward heat dissipation copper sheet 5 is obtained by stamping pure copper sheet, and welding positioning holes 54 are formed by stamping the four corners. The middle area is polished as the plastic seal printing area. The left and right sides are stretched and widened to form the second heat dissipation copper surface 52 and the third heat dissipation copper surface 53. The welding area on the lower surface of the dual independent outward heat dissipation copper sheet 5 is roughened to improve the ultrasonic bonding strength. S5, Four-point self-supporting ultrasonic welding: The semi-finished product with aluminum wire bonding is placed in the ultrasonic welding station. The dual independent outward heat dissipation copper sheet 5 is supported and limited by the four welding positioning holes 54 at the four corners. The ultrasonic welding head is pressed directly down to the top surface of the dual independent outward heat dissipation copper sheet 5. Constant pressure is applied in conjunction with ultrasonic vibration to achieve solderless atomic-level metal bonding between the dual independent outward heat dissipation copper sheet 5 and the front side of the power chip 3. Pressure holding and cooling are used to fix the dual independent outward heat dissipation copper sheet 5. It should be noted that step S5 above relies on the four corner support bumps of the dual independent outward heat dissipation copper sheets to form a four-point rigid positioning reference, eliminating the need for additional external tooling such as pressure arrays and pressure blocks, thereby reducing the chip breakage defect rate. At the same time, the dual independent outward heat dissipation copper sheets and the front metal layer of the chip achieve atomic-level metal bonding through high-frequency ultrasound, without solder interlayers, and there is no problem of high-temperature melting, long-term aging, or void failure, thereby improving the reliability of temperature cycling and power cycling.

[0046] S6. Partitioned directional molding: The welded semi-finished product is placed into the molding mold and epoxy resin is injected and cured at high temperature; the epoxy resin only fills and wraps the power chip 3, aluminum bonding wire 2, the three pin roots of the three-pin lead frame 1 and the molding printing area 51 of the dual independent outward heat dissipation copper sheet 5, and fully exposes the first heat dissipation copper surface 4, the second heat dissipation copper surface 52 and the third heat dissipation copper surface 53.

[0047] The first heat dissipation copper surface 4 conducts heat downwards, while the second heat dissipation copper surface 52 and the third heat dissipation copper surface 53 simultaneously conduct heat upwards through convection. The three independent outward-facing metal heat dissipation channels work together to dissipate the chip's heat.

[0048] S7. Post-processing and full inspection: After plastic sealing, remove burrs and trim and shape the leads. Laser marking is carried out on the surface of the heat-insulating plastic seal 6 on the printing area 51 of the plastic seal. Electrical performance test, withstand voltage test, steady-state thermal resistance test and appearance inspection are completed in sequence. After passing the inspection, the product is put into storage.

[0049] Both the pure copper strip and the pure copper plate are made of oxygen-free copper material.

[0050] In step S5, the ultrasonic welding head is provided with a frustum-shaped protrusion corresponding to the welding positioning hole 54.

[0051] See Figure 7 The frustum-shaped protrusion is tapered toward the welding positioning hole, and the maximum outer diameter of the frustum-shaped protrusion is smaller than the diameter of the welding positioning hole 54.

[0052] Heat is conducted downward through the first heat dissipation copper surface 4 of the finished power device, and heat is simultaneously dissipated upward through the two independent outward heat dissipation copper sheets 5 on the left and right sides. The three independent metal heat dissipation channels work simultaneously to reduce the steady-state thermal resistance of the power device.

[0053] It should be noted that the dual independent outward heat dissipation copper sheet 5 of the present invention is prefabricated by a whole copper sheet body metal. The continuous whole copper sheet body metal only represents solid thermal conduction and interconnection, but the external convection heat dissipation channel is completely isolated. It is encapsulated and isolated by the intermediate heat insulation plastic seal 6, thereby splitting the exposed area of ​​the dual independent outward heat dissipation copper sheet 5 into two sets of non-interfering external convection heat dissipation channels to achieve the purpose of bidirectional independent convection heat dissipation.

[0054] The manufacturing method provided by this invention utilizes a three-copper-surface double-sided heat dissipation design, allowing heat to be simultaneously discharged through three independent channels formed by the first heat dissipation copper surface 4 at the bottom, the second heat dissipation copper surface 52 at the top, and the third heat dissipation copper surface 53. The air thermal boundary layer is cut off by the encapsulation between the second heat dissipation copper surface 52 and the third heat dissipation copper surface 53, forcing the heat to diffuse evenly to both sides laterally, reducing the thermal stress directly above the chip. Through the cooperation of the welding positioning holes 54 at the four corners and the frustum-shaped protrusions on the ultrasonic welding head, the self-supporting and precise positioning of the copper sheet is achieved without relying on additional clamping fixtures, thereby reducing the possibility of welding misalignment and warping. By eliminating the CLIP conductive components and their matching molds, stamping, and electroplating processes, the bill of materials and process flow are simplified, thereby reducing the overall manufacturing cost.

[0055] To facilitate a thorough understanding and implementation of the technical solution of this invention by those skilled in the art, and to clearly elucidate the structural features and process flow of this invention, the invention will be further described in detail and completely below with reference to specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of this invention.

[0056] Example 1: A power device with four-point ultrasonic support positioning, three copper surfaces, and double-sided heat dissipation is disclosed. The three-pin lead frame is a standard three-pin structure integrally stamped from 0.4mm oxygen-free copper. The first heat dissipation copper surface is 1.2mm thick, and its surface is electroplated with a 3μm nickel layer and a 0.05μm thin gold layer for oxidation prevention. The power chip is a 1200V silicon carbide MOS chip, which is fixed to the first heat dissipation copper surface using a silver sintering process. The front of the power chip uses multiple aluminum wires to bond the gate, source, and drain leads respectively, without a clip conductive structure. The two independent outward heat dissipation copper sheets are 0.6mm thick, with four symmetrically arranged welding positioning holes at the four corners. The central plastic-encapsulated printing area measures 6mm in length and 2.5mm in width. The second and third heat dissipation copper surfaces on the left and right sides each extend outward by 2.3mm. The heat-insulating plastic encapsulation is made of insulating and heat-insulating epoxy resin, which only covers the power chip, aluminum bonding wires, the pin roots of the three-pin lead frame, and the plastic-encapsulated printing area. The surfaces of the first heat dissipation copper surface, the second heat dissipation copper surface on the left and right sides of the dual independent outward heat dissipation copper sheets are completely exposed. The ultrasonic welding relies on the welding positioning holes on the dual independent outward heat dissipation copper sheets for self-support and limitation, ultimately forming three independent outward heat dissipation metal heat dissipation channels at the bottom, left, and right.

[0057] Example 2: A method for fabricating a power device with four-point ultrasonic support positioning and three copper surfaces for double-sided heat dissipation, comprising the following complete steps: S1. The oxygen-free copper strip is integrally stamped with a TO247-3L three-pin lead frame, and the first heat dissipation copper surface is nickel-plated and gold-plated for anti-oxidation treatment. S2, silver sintering and crystal bonding, sintering temperature 220℃, holding temperature for 40min, to achieve low thermal resistance bonding between the power chip and the first heat dissipation copper surface; S3. Aluminum bonding wires complete the electrical interconnection between the gate, source, and drain of the power chip and the three pins of the three-pin lead frame through aluminum wire bonding. S4. Stamping process for double independent outward heat dissipation copper sheets with welding positioning holes; polishing process for the middle part of the double independent outward heat dissipation copper sheets; roughening process for the welding area of ​​the double independent outward heat dissipation copper sheets to improve ultrasonic bonding force. S5. The dual independent outward heat dissipation copper plates are supported and positioned by four welding positioning holes. The ultrasonic bonding without solder is completed with an ultrasonic power of 2000W, a welding pressure of 85N, and a holding pressure of 0.6s. S6, directional molding injection, curing temperature 175℃, heat preservation for 90min, the heat insulation molding body only seals the upper surface of the molding printing area, leaving three metal heat dissipation surfaces fully exposed; S7. After molding, remove burrs and trim and shape the leads. Laser mark product information on the surface of the heat-insulating molded body in the middle of the molded area of ​​the dual independent outward heat dissipation copper sheet. Then, conduct high voltage withstand voltage test, switch characteristic test, steady-state thermal resistance test, and full appearance inspection in sequence. After passing the inspection, the product is put into storage.

[0058] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0059] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power device with four-point ultrasonic support positioning, three copper surfaces, and double-sided heat dissipation, characterized in that, Includes a three-pin lead frame, aluminum bonding wires, power chip, first heat dissipation copper surface, dual independent outward heat dissipation copper sheets, and thermal insulation encapsulation; The lower surface of the power chip is connected to the first heat dissipation copper surface, and the first heat dissipation copper surface is connected to the three-pin lead frame. The pin roots of the three-pin lead frame are connected to the upper surface of the power chip via the aluminum bonding wires, which cross the first heat dissipation copper surface. The upper surface of the power chip is connected to the lower surface of the dual independent outward heat dissipation copper sheets; The upper surface of the dual independent outward heat dissipation copper sheet is provided with a plastic seal printing area, a second heat dissipation copper surface and a third heat dissipation copper surface. The plastic seal printing area is located in the middle area of ​​the upper surface of the dual independent outward heat dissipation copper sheet. The second heat dissipation copper surface and the third heat dissipation copper surface are respectively located on both sides of the plastic seal printing area. Welding positioning holes are opened on both the second heat dissipation copper surface and the third heat dissipation copper surface. The thermal insulation molding compound covers the power chip, the aluminum bonding wire, the pin roots of the three-pin lead frame, and the molding printing area; The surfaces of the first heat dissipation copper surface, the second heat dissipation copper surface, and the third heat dissipation copper surface are all exposed to the external environment.

2. The power device with four-point ultrasonic support positioning, three copper surfaces, and double-sided heat dissipation as described in claim 1, characterized in that, The total number of welding positioning holes is four, with two welding positioning holes respectively opened on the second heat dissipation copper surface and the third heat dissipation copper surface.

3. The power device with four-point ultrasonic support positioning, three copper surfaces, and double-sided heat dissipation as described in claim 1, characterized in that, The device model, electrical parameters, and production batch are laser-marked or screen-printed on the plastic-sealed printing area.

4. The power device with four-point ultrasonic support positioning, three copper surfaces, and double-sided heat dissipation as described in claim 1, characterized in that, The power device is a TO247-3L power device.

5. The power device with four-point ultrasonic support positioning, three copper surfaces, and double-sided heat dissipation as described in claim 1, characterized in that, The heat-insulating encapsulation material is epoxy resin.

6. A method for fabricating a power device with four-point ultrasonic support positioning, three copper surfaces, and double-sided heat dissipation as described in any one of claims 1 to 5, characterized in that, include: S1. Lead frame processing: The three-pin lead frame of standard TO247-3L is integrally stamped and formed from pure copper strip. The first heat dissipation copper surface is integrally formed, and the surface of the first heat dissipation copper surface is successively plated with nickel and gold to complete the anti-oxidation treatment. S2. Chip die bonding: The lower surface of the power chip is bonded and fixed to the first heat dissipation copper surface by using a soldering or silver sintering process, and solidified to form a back heat-conducting bonding layer. S3, Aluminum wire bonding: The gate, source, and drain of the power chip on the upper surface are respectively connected to the three pins of the three-pin lead frame through the aluminum bonding wire; S4. Prefabrication of dual independent outward heat dissipation copper sheets: The dual independent outward heat dissipation copper sheets are obtained by stamping pure copper plates and forming the welding positioning holes by stamping the four corners. The central area is polished as the plastic seal printing area. The left and right sides are stretched and widened to form the second heat dissipation copper surface and the third heat dissipation copper surface. The welding area on the lower surface of the dual independent outward heat dissipation copper sheets is roughened. S5, Four-point self-supporting ultrasonic welding: The semi-finished product with aluminum wire bonding is placed in the ultrasonic welding station. The double independent outward heat dissipation copper sheet is supported and limited by the four welding positioning holes at the four corners. The ultrasonic welding head is pressed directly down to the top surface of the double independent outward heat dissipation copper sheet and constant pressure is applied in conjunction with ultrasonic vibration. S6. Partitioned directional molding: The welded semi-finished product is placed into the molding mold and epoxy molding compound is injected and cured at high temperature; the epoxy molding compound only fills and wraps the power chip, the aluminum bonding wire, the three pin roots of the three-pin lead frame and the molding printing area of ​​the dual independent outward heat dissipation copper sheet, and completely exposes the first heat dissipation copper surface, the second heat dissipation copper surface and the third heat dissipation copper surface; S7. Post-processing and full inspection: After plastic sealing, remove burrs and trim and shape the leads. Laser mark the surface of the heat-insulating plastic seal on the printed area of ​​the plastic seal. Then, complete the electrical performance test, withstand voltage test, steady-state thermal resistance test, and appearance inspection in sequence. After passing the inspection, the seal is put into storage.

7. The method for fabricating a power device with four-point ultrasonic support positioning, three copper surfaces, and double-sided heat dissipation as described in claim 6, characterized in that, Both the pure copper strip and the pure copper plate are made of oxygen-free copper material.

8. The method for fabricating a power device with four-point ultrasonic support positioning and three copper surfaces for double-sided heat dissipation as described in claim 6, characterized in that, The ultrasonic welding head is provided with a frustum-shaped protrusion corresponding to the welding positioning hole.

9. The method for fabricating a power device with four-point ultrasonic support positioning, three copper surfaces, and double-sided heat dissipation as described in claim 8, characterized in that, The frustum-shaped protrusion is gradually tapered toward the welding positioning hole.

10. The method for fabricating a power device with four-point ultrasonic support positioning, three copper surfaces, and double-sided heat dissipation as described in claim 8, characterized in that, The maximum outer diameter of the frustum-shaped protrusion is smaller than the diameter of the welding positioning hole.

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