Power module and packaging method thereof

Abstract

According to the power module and the packaging method thereof provided by the invention, the packaging process is improved, and the chip to be packaged is electrically connected with the substrate and the printed circuit board through the soldering paste, so that the prepared power module can realize the shortest distance between the circuit between the chip and the bus terminal, thereby greatly reducing the circuit inductance and improving the reliability of the power module. In addition, after the line inductance is reduced, the switching loss of the power device can be lower, the front face and the back face of the to-be-packaged chip do not need to be subjected to copper pre-plating treatment, the complexity of the packaging technology is greatly reduced, the manufacturing cost of the power module is controlled, a driving chip can be integrated on the power module through the packaging method, and the packaging efficiency is improved. Compared with the prior art, a driving function is added to the power module, the power module is simpler and more convenient to use, and in addition, the power module obtained through the packaging method has good heat dissipation capacity and can meet the requirement for high power of an automobile.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor integrated circuit manufacturing, and in particular to a power module and a packaging method thereof. Background Art

[0002] A power semiconductor module refers to a power electronic device that encapsulates power semiconductor chips (IGBT, MOSFET, etc.) in an insulating shell according to a certain circuit structure. Its main function is to realize power electronic power conversion. It is the core component of energy conversion and is widely used in rail transportation, smart grid, industrial energy conservation, electric vehicles and new energy equipment.

[0003] The packaging technology for embedding chips with PCB (printed circuit board) includes two forms: direct chip embedding into PCB and indirect chip embedding into PCB. Among them, direct chip embedding into PCB can significantly shorten the conductive line, thereby effectively reducing stray inductance and greatly improving power density, which is attracting widespread attention. So far, digital logic chips and low-power chips have been successfully embedded directly with PCB, which undoubtedly provides strong technical support for the miniaturization, lightweight and high efficiency of electronic products. However, for automotive power chips, due to their relatively harsh working environment, they have extremely stringent requirements on heat dissipation efficiency, insulation withstand voltage performance and operating reliability, which makes the direct embedding of automotive power chips into PCB encounter many technical difficulties. On the one hand, due to the relatively limited thermal conductivity of prepreg (a thermosetting material commonly used in packaging), its thermal conductivity is generally low, which undoubtedly limits the heat dissipation efficiency of automotive power chips, thereby affecting the stable operation of the entire power module. In addition, in order to avoid damage to automotive power chips during laser drilling, it is usually necessary to pre-plate a layer of copper on the front and back of the chip, which increases the complexity of the process.

[0004] The chip indirect embedding PCB technology can improve the heat dissipation capacity of the chip. It builds an efficient heat dissipation channel by welding a copper block under the chip or drilling and copper plating under the chip, and leads this channel to the outside of the PCB for better heat dissipation. However, since this heat dissipation channel is charged, it is necessary to stick a layer of insulating thermal conductive film to achieve insulation protection. Although the thermal conductivity of insulating thermal conductive film has been improved to a certain extent in recent years, it is still difficult to meet the high standards of heat dissipation performance of the power module of the automotive electric drive system. At the same time, this technology also puts forward more stringent requirements for the process management of the PCB factory. In addition, in order to ensure that the chip is not damaged during the laser drilling process, the chip still needs to be specially treated, that is, a copper layer with a thickness greater than 8 microns is pre-plated on the front and back or front of the chip. This step further increases the complexity of the packaging process.

[0005] Therefore, it is necessary to provide a power module and a packaging method thereof. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a power module and a packaging method thereof, which are used to solve the problems that the power module in the prior art cannot meet the low inductance and high power density characteristics of embedded PCB packaging while meeting the heat dissipation requirements of the power module and the complex process.

[0007] To achieve the above object and other related objects, the present invention provides a packaging method for a power module, comprising the following steps: A substrate is provided, the substrate comprising a top metal layer, a dielectric layer, and a bottom metal layer, and a first solder paste printing is performed at a preset position on the top metal layer to form a first solder layer; Mounting the chip to be packaged and the raised copper pillars on the first welding layer; Performing a first soldering on the substrate on which the chip and the copper pillar are mounted, so that the chip to be packaged is electrically connected to the top metal layer; Performing a second solder paste printing on the chip to be packaged and the copper pillar to form a second soldering layer, and combining the substrate formed with the second soldering layer with a customized printed circuit board and loading them into a fixture, wherein a plurality of circuit ports are arranged on the lower surface of the customized printed circuit board; Soldering the fixture and the substrate for a second time so that the circuit port is electrically connected to the chip to be packaged and the second welding layer on the copper column respectively; Preheating the substrate after the second welding and performing plastic sealing; Systematically welding the plastic-encapsulated substrate and the heat dissipation structure to connect the bottom metal layer with the heat dissipation structure to form a heat dissipation channel; A third solder paste printing is performed on the upper surface of the printed circuit board to form a third soldering layer, a driving chip is mounted on the third soldering layer, and a third soldering is performed simultaneously and an electrical performance test is performed.

[0008] Optionally, a plurality of power terminals and signal terminals are further provided on the upper surface of the printed circuit board, and after the electrical performance test, the power terminals and the signal terminals are electrically connected to an additionally provided busbar by welding.

[0009] Optionally, the type of the chip to be packaged includes at least one of MOSFET, IGBT, diode or thyristor.

[0010] Optionally, the second welding layer occupies 50% to 90% of the area of ​​the chip to be packaged, and the second welding layer occupies 50% to 90% of the area of ​​the top of the copper column.

[0011] Optionally, the heat dissipation structure includes a heat dissipation base plate fixed on the bottom metal layer and facing away from the top metal layer, and heat dissipation pin fins fixed on the heat dissipation base plate and facing away from the bottom metal layer.

[0012] Optionally, after the first welding, the step of surface treating the substrate on which the chip to be packaged and the copper pillar are mounted is also included, and after the second welding, the step of surface treating the substrate is also included, and the surface treatment method includes multi-stage ultrasonic cleaning.

[0013] Optionally, oxygen-free copper, bare copper, nickel-plated copper or tin-plated copper is provided on the circuit port, and the circuit port corresponds one-to-one to the chip to be packaged and the area of ​​the copper column on the substrate.

[0014] Optionally, resistors and capacitors are also mounted on the third welding layer.

[0015] Optionally, the type of the substrate includes a ceramic double-sided copper-clad substrate, and the top metal layer and the bottom metal layer have the same thickness.

[0016] The present invention also provides a power module, and the power module is packaged by adopting the above-mentioned power module packaging method.

[0017] As described above, the power module and packaging method thereof of the present invention have the following beneficial effects: Compared with the directly embedded and indirectly embedded PCB packages in the traditional power module, the power module of the present invention integrates a driving chip, thereby increasing the driving function of the power module and being simpler and more convenient to use.

[0018] Compared with traditional power modules, the power module of the present invention can achieve the shortest connection between the chip and the bus terminal, thereby greatly reducing the circuit inductance. After the line inductance is reduced, the switching loss of the power device is lower, which saves more energy.

[0019] The volume of the power module of the present invention is approximately one-half of that of the traditional power module, so that the power density of the product is higher.

[0020] The packaging form of the power module in the present invention does not require pre-copper plating on the front and back sides of the chip, which greatly reduces the complexity of the packaging process and controls the chip cost.

[0021] The power module of the present invention has good heat dissipation capability and can meet the high power requirements of automobiles. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Shown is a process flow chart of the power module packaging method of the present invention.

[0023] Figure 2 It is a schematic structural diagram of the power module packaging method of the present invention after the first welding layer is formed.

[0024] Figure 3 It is a schematic diagram showing the structure of the power module packaging method of the present invention after mounting the chip to be packaged.

[0025] Figure 4 It is a schematic diagram of the cross-sectional structure after forming the second welding layer of the power module packaging method of the present invention.

[0026] Figure 5 A schematic structural diagram showing the lower surface of a customized printed circuit board according to the power module packaging method of the present invention.

[0027] Figure 6 It is a schematic structural diagram showing the substrate and the customized printed circuit board after plastic packaging in the power module packaging method of the present invention.

[0028] Figure 7 It is a schematic structural diagram of the power module packaging method of the present invention after the heat dissipation structure is formed.

[0029] Figure 8 It is a schematic diagram showing the structure of the power module packaging method of the present invention after mounting the driver chip.

[0030] Component number description 10. Substrate; 101. Bottom metal layer; 102. Dielectric layer; 103. Top metal layer; 13. First welding layer; 14. Chip to be packaged; 15. Copper pillar; 16. Second welding layer; 17. Printed circuit board; 171. Lower surface; 1711. Circuit port; 172. Upper surface; 1721. Mounting area; 18. Plastic layer; 19. Heat dissipation structure; 191. Heat dissipation base plate; 192. Heat dissipation pin fins; 20. Driver chip; S1~S8: steps. DETAILED DESCRIPTION

[0031] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0032] For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the schematic diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0033] For convenience of description, spatially relative terms such as "under", "below", "below", "below", "above", "on", etc. may be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It will be understood that these spatially relative terms are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the drawings.

[0034] In the context of the present application, a structure in which a first feature is described as being "above" a second feature may include embodiments in which the first and second features are in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0035] It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and therefore the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0036] Example 1

[0037] This embodiment provides a packaging method for a power module, such as Figure 1 FIG. 1 is a process flow chart of the packaging method of the power module, comprising the following steps: S1: providing a substrate 10, wherein the substrate 10 comprises a top metal layer 103, a dielectric layer 102, and a bottom metal layer 101, and performing a first solder paste printing at a preset position on the top metal layer 103 to form a first solder layer 13; S2: mounting the chip 14 to be packaged and the raised copper pillars 15 on the first welding layer 13; S3: performing a first welding on the mounted chip 14 to be packaged and the substrate 10 of the copper pillar 15, so that the chip 14 to be packaged is electrically connected to the top metal layer 103; S4: performing a second solder paste printing on the chip 14 to be packaged and the copper pillar 15 to form a second soldering layer 16, and combining the substrate 10 with the second soldering layer 16 and the customized printed circuit board 17 into a fixture, wherein a plurality of circuit ports 1711 are arranged on the lower surface 171 of the customized printed circuit board 17; S5: welding the fixture and the substrate 10 for a second time, so that the circuit port 1711 is electrically connected to the chip to be packaged 14 and the second welding layer 16 on the copper pillar 15 respectively; S6: preheating the substrate 10 after the second welding, and performing plastic packaging to form a plastic packaging layer 18; S7: Systematically welding the plastic-encapsulated substrate 10 and the heat dissipation structure 19 to connect the bottom metal layer 101 with the heat dissipation structure 19 to form a heat dissipation channel; S8: Print solder paste for a third time on the upper surface 172 of the printed circuit board 17 to form a third soldering layer, mount the driver chip 20 on the third soldering layer, and simultaneously perform a third soldering and electrical performance test.

[0038] The packaging method of the power module is further introduced below in conjunction with the accompanying drawings. It should be noted that the above sequence does not strictly represent the packaging method of the power module protected by the present invention, and those skilled in the art may change it according to the actual preparation steps. The packaging method of the power module is further introduced below in conjunction with the accompanying drawings, as follows: In step S1, see Figure 1 and Figure 2 , a substrate 10 is provided, wherein the substrate 10 includes a top metal layer 103 , a dielectric layer 102 , and a bottom metal layer 101 , and a first solder paste printing is performed at a preset position on the top metal layer 103 to form a first soldering layer 13 .

[0039] As an example, the type of the substrate 10 includes a ceramic double-sided copper-clad substrate or other suitable circuit boards. In this embodiment, a ceramic double-sided copper-clad substrate is used as the substrate 10, that is, the material of the top metal layer 103 is copper, the material of the bottom metal layer 101 is copper, and the dielectric layer 102 is a ceramic layer. The material of the dielectric layer 102 can be Al2O3, Si3N4, AlN and other ceramic materials. The process of making the top metal layer 103 and the bottom metal layer 101 on the dielectric layer 102 can be thin film, thick film, electroplated copper, direct copper, activated brazing copper, brazing copper, and hard brazing copper. The specific substrate 10 manufacturing process is selected according to the needs of the power module or the generation process requirements.

[0040] Specifically, the thickness of the top metal layer 103 is generally in the range of 0.2 mm to 0.8 mm, for example, it can be 0.20 mm, 0.25 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.8 mm, and the specific thickness of the top metal layer 103 can be selected according to actual needs; the thickness of the dielectric layer 102 is generally in the range of 0.25 mm to 1 mm, for example, it can be 0.25 mm, 0.32 mm, 0.38 mm, 0.63 mm, 1.0 mm, and the dielectric layer 1 The thickness of the bottom metal layer 101 can be selected according to actual needs; generally, the thickness of the bottom metal layer 101 ranges from 0.2mm to 0.8mm, for example, it can be 0.20mm, 0.25mm, 0.3mm, 0.4mm, 0.5mm, 0.8mm. The thickness of the bottom metal layer 101 can be selected according to actual needs. Under the condition of ensuring the performance of the power module, the thickness of the bottom metal layer 101 can be different from or the same as the thickness of the top metal layer 103, depending on specific needs. In this embodiment, preferably, the thickness of the bottom metal layer 101 is the same as the thickness of the top metal layer 103, and both are 0.3mm.

[0041] like Figure 2 As shown, there are multiple preset positions on the top metal layer 103, and the preset positions are isolated from each other to facilitate the electrical interconnection between the chips 14 to be packaged in the power module. The first solder paste printing process is performed at the preset positions, and the solder paste at the preset positions forms the first welding layer 13 through the welding process. Optionally, the type of solder paste used in the first solder paste printing process includes one or more of tin paste, silver paste or copper paste. When silver paste or copper paste is selected, the substrate 10, the chip 14 to be packaged and the copper pillar 15 need to be placed in a sintering furnace for a sintering process to achieve electrical connection between the chip 14 to be packaged and the copper on the top metal layer 103. Preferably, in this embodiment, the type of solder paste used in the first solder paste printing process is selected as tin paste.

[0042] In steps S2 and S3, see Figure 1 and Figure 3 , the chip 14 to be packaged and the raised copper pillars 15 are mounted on the first welding layer 13, and the substrate 10 with the chip and the copper pillars 15 mounted thereon is subjected to the first welding, so that the chip is electrically connected to the top metal layer 103.

[0043] Specifically, Figure 3As shown, the chip 14 to be packaged and the raised copper pillar 15 are mounted at a preset position on the top metal layer 103. Optionally, the method of mounting the chip 14 to be packaged and the raised copper pillar 15 includes manual placement, placement machine placement or other suitable placement methods. In this embodiment, the chip 14 to be packaged and the raised copper pillar 15 are placed on the first welding layer 13 at a preset position on the top metal layer 103 by a placement machine placement method, so that after the first subsequent welding process, an electrical connection is formed between the chip 14 to be packaged and the top metal layer 103. The copper pillar 15 plays the role of circuit connection here, for example: carrying the current between the C and E poles of the IGBT chip or carrying the current between the D and S poles of the Mosfet chip.

[0044] Specifically, the types of the chip 14 to be packaged include MOS, IGBT, diode, thyristor or other suitable electronic devices.

[0045] In this embodiment, the substrate 10 on which the chip and the copper pillar 15 are mounted is subjected to the first soldering. Specifically, the type of solder paste used in the first solder paste printing process is tin paste. The substrate 10 on which the chip 14 to be packaged and the copper pillar 15 are mounted is placed in a vacuum soldering furnace, which is heated and evacuated by the furnace so that the first soldering layer 13 formed by the tin paste can be melted and then cooled, so that the chip 14 to be packaged is soldered together with the top metal layer 103 to form an electrical connection.

[0046] In one embodiment, after the first welding, the substrate 10 on which the chip 14 to be packaged and the copper pillar 15 are mounted needs to be surface treated, and the surface treatment method includes dry etching, wet etching or other suitable methods. In this embodiment, the excess solder paste residue can be removed by wet etching, and then the substrate 10 can be cleaned in combination with multi-stage ultrasonic cleaning. In the actual production process, different levels of ultrasonic cleaning have different cleaning capabilities, and surface impurities can be effectively cleaned. Different levels of ultrasonic cleaning can produce different cleaning effects by adjusting the frequency of ultrasonic equipment. This technical means is a prior art and will not be described in detail here.

[0047] In step S4, see Figure 1 , Figure 4 and Figure 5 , a second solder paste printing is performed on the chip 14 to be packaged and the copper pillar 15 to form a second soldering layer 16, and the substrate 10 forming the second soldering layer 16 is combined with a customized printed circuit board 17 and loaded into a fixture, and a plurality of circuit ports 1711 are provided on the lower surface 171 of the customized printed circuit board 17.

[0048] like Figure 4 As shown, a second solder paste printing process is performed on the chip to be packaged 14 and the copper pillar 15, respectively, and the solder paste on the chip and the copper pillar 15 forms a second solder layer 16 through a welding process. Optionally, the type of solder paste used in the second solder paste printing process includes one or more of tin paste, silver paste or copper paste. Preferably, in this embodiment, the type of solder paste used in the second solder paste printing process is tin paste.

[0049] In one embodiment, in order to achieve a better welding effect, the area of ​​the second solder paste printing process is set according to the size of the gate, E-pole, and S-pole areas of the chip 14 to be packaged. Specifically, the formed second welding layer 16 occupies 50% to 90% of the area of ​​the chip 14 to be packaged, and the second welding layer 16 occupies 50% to 90% of the top area of ​​the copper pillar 15.

[0050] In another embodiment, if Figure 5 As shown, a customized printed circuit board 17 is provided, and a plurality of circuit ports 1711 are arranged on the lower surface 171 of the customized printed circuit board 17, and oxygen-free copper, bare copper, nickel-plated copper or tin-plated copper are arranged on the circuit ports 1711, and the circuit ports 1711 correspond one-to-one to the areas of the chip 14 to be packaged and the copper pillars 15 on the substrate 10, and then the substrate 10 forming the second welding layer 16 and the customized printed circuit board 17 are combined and fixed in a fixture, so that the circuit port 1711 can be arranged in contact with the chip 14 to be packaged and the second welding layer 16 on the copper pillars 15, so that the circuit port 1711 can form an electrical connection with the chip 14 to be packaged and the copper pillars 15 through a subsequent welding process.

[0051] In steps S5 and S6, see Figure 1 and Figure 6 , the fixture and the substrate 10 are welded for a second time, so that the circuit port 1711 is electrically connected to the chip 14 to be packaged and the second welding layer 16 on the copper pillar 15 respectively, the substrate 10 that has been welded for the second time is preheated, and plastic-sealed to form a plastic sealing layer 18.

[0052] In this embodiment, the clamp and the substrate 10 are soldered for a second time. Specifically, the type of solder paste used in the second solder paste printing process is tin paste. The clamp and the substrate 10 are placed in a vacuum soldering furnace, which is heated and evacuated so that the second soldering layer 16 formed by the tin paste can be melted and then cooled, so that the chip 14 to be packaged and the copper column 15 are soldered together with the circuit port 1711 of the printed circuit board 17 to form an electrical connection.

[0053] In one embodiment, after the second soldering, the substrate 10 needs to be surface treated, and the surface treatment method includes dry etching, wet etching or other suitable methods. In this embodiment, the excess solder paste residue can be removed by wet etching, and then the substrate 10 can be cleaned in combination with multi-stage ultrasonic cleaning.

[0054] Furthermore, after the second welding and cleaning steps are completed, a drying step is also included, in which the cleaned substrate 10 is placed in a constant temperature box for preheating treatment to remove moisture. After the preheating treatment is completed, the substrate 10 is plastic-sealed to form a plastic sealing layer 18.

[0055] Optionally, the plastic encapsulation method includes compression molding, transfer molding, liquid sealing molding, vacuum lamination, spin coating or other suitable methods. Specifically, in this embodiment, the substrate 10 and the printed circuit board 17 are placed in a packaging mold of a suitable size, and the packaging glue is injected and the packaging glue in the packaging mold is cured to complete the plastic encapsulation of the substrate 10.

[0056] Optionally, the plastic encapsulation material includes epoxy resin, polyimide, silica gel, polymaleimide triazine resin, polyphenylene ether, polytetrafluoroethylene or other suitable dielectric materials. Specifically, in this embodiment, epoxy resin plastic encapsulation material is used to fill and coat the gap between the substrate 10 and the printed circuit board 17 and the edge of the substrate 10, and the formed plastic encapsulation layer 18 can not only play the role of sealing insulation and stress buffering, but also play the role of mechanical protection for the substrate 10 and the printed circuit board 17. After the plastic encapsulation is completed, the copper layer on the bottom metal layer 101 of the substrate 10 is exposed to the outside as a heat dissipation surface.

[0057] In step S7, refer to Figure 1 and Figure 7 The plastic-encapsulated substrate 10 and the heat dissipation structure 19 are systematically welded to connect the bottom metal layer 101 with the heat dissipation structure 19 to form a heat dissipation channel.

[0058] As an example, Figure 7 , which is a schematic diagram of the structure after the heat dissipation channel is formed, the substrate 10 and the heat dissipation structure 19 are systematically welded, so that the bottom metal layer 101 and the heat dissipation structure 19 are electrically connected to form a heat dissipation channel.

[0059] Specifically, the heat dissipation structure 19 is used to improve the heat dissipation performance of the power module, and the heat dissipation structure 19 can also provide physical support for the power module.

[0060] Specifically, the heat dissipation structure 19 may be made of copper, aluminum or other materials with high thermal conductivity.

[0061] As an example, the heat dissipation structure 19 includes a heat dissipation base plate 191 fixed on the bottom metal layer 101 and facing away from the top metal layer 103 and a heat dissipation pin fin 192 fixed on the heat dissipation base plate 191 and facing away from the bottom metal layer 101 .

[0062] Specifically, the size of the heat dissipation base plate 191 is not less than the size of the substrate 10, so as to increase the contact area between the bottom metal layer 101 of the substrate 10 and the heat dissipation structure 19, so that the heat in the substrate 10 can be quickly diffused to the heat dissipation base plate 191, wherein the thickness and shape of the heat dissipation base plate 191 can be selected according to actual conditions and are not limited here. In this embodiment, the size of the heat dissipation base plate 191 is larger than the size of the substrate 10 after plastic encapsulation.

[0063] Specifically, the heat dissipation pin fins 192 are used to increase the contact area between the heat dissipation structure 19 and the air, so that the heat conducted from the substrate 10 to the heat dissipation structure 19 can be quickly transferred to the air, wherein the number, shape and distance between adjacent heat dissipation pin fins 192 can be selected according to actual conditions and are no longer restricted here.

[0064] As an example, a pre-welding sheet is provided between the bottom surface of the substrate 10 and the heat dissipation base plate 191 . The pre-welding sheet is melted and then cooled by system welding so that the heat dissipation base plate 191 is fixed to the bottom metal layer 101 of the substrate 10 .

[0065] Specifically, by melting and cooling the pre-solder sheet, a fixed connection is formed between the bottom metal layer 101 of the substrate 10 and the heat dissipation base plate 191. The material forming the pre-solder sheet generally has high thermal conductivity and the ability to firmly connect the substrate 10 and the heat dissipation base plate 191.

[0066] In step S8, refer to Figure 1 and Figure 8 , a third solder paste printing is performed on the upper surface 172 of the printed circuit board 17 to form a third soldering layer, a driving chip 20 is mounted on the third soldering layer, and a third soldering is performed simultaneously and an electrical performance test is performed.

[0067] Specifically, a mounting area 1721 for the driver chip 20 is reserved on the upper surface 172 of the printed circuit board 17, and a third solder paste printing process is performed on these reserved mounting areas 1721 to form a third welding layer in the reserved mounting areas 1721 on the upper surface 172 of the printed circuit board 17. Optionally, the type of solder paste used in the third solder paste printing process includes one or more of tin paste, silver paste or copper paste. Preferably, in this embodiment, the type of solder paste used in the third solder paste printing process is tin paste.

[0068] A driver chip 20 is mounted on the third welding layer, and other types of components such as resistors and capacitors are also mounted on the third welding layer. Then, the substrate 10 mounted with the driver chip 20 and the resistors and capacitors is welded for the third time. Specifically, the substrate 10 mounted with the driver chip 20 and the resistors and capacitors is placed in a vacuum welding furnace, and the vacuum welding furnace is used to heat and evacuate, so that the third welding layer formed by the solder paste can be melted and then cooled, so that the driver chip 20 is welded together with the mounting area 1721 for the driver chip 20 set on the upper surface 172 of the printed circuit board 17, and an electrical connection is formed.

[0069] Specifically, after mounting the driver chip 20 on the printed circuit board 17 and completing the third welding process, a step of performing an electrical performance test on the formed power module is also included to ensure the product quality of the power module.

[0070] Specifically, a plurality of power terminals and signal terminals are further provided on the upper surface 172 of the printed circuit board 17. After the electrical performance test reaches qualified product quality, the additionally provided busbars can be electrically connected to the reserved power terminals and signal terminals. The method of electrically connecting the power terminals and signal terminals to the corresponding busbars includes wire bonding, welding or other suitable electrical connection methods. In this embodiment, the power terminals and signal terminals are electrically connected to the provided busbars by welding.

[0071] The packaging method of the power module of this embodiment improves the packaging process of packaging the power module, electrically connects the chips 14 to be packaged through copper pillars 15, and electrically connects the chips 14 to be packaged, the substrate 10 and the printed circuit board 17 through solder paste, so that there is no need to pre-copper-plate the front and back sides of the chips 14 to be packaged, so that the manufacturing cost of the power module is controlled. Moreover, since the packaging method integrates a driving chip, compared with the prior art, the power module has an additional driving function, which is simpler and more convenient to use. The chips 14 to be packaged are electrically connected to the substrate 10 and the printed circuit board 17 through solder paste, so that the power module can achieve the shortest distance between the chip 14 to be packaged and the bus terminal, thereby greatly reducing the circuit inductance. After the line inductance is reduced, the switching loss of the power device can also be lower.

[0072] Example 2

[0073] This embodiment provides a power module, and the power module is packaged by using the power module packaging method described in Embodiment 1.

[0074] Specifically, the power module includes at least one substrate 10, a chip to be packaged 14, a copper pillar 15, a first welding layer 13, a second welding layer 16, a customized printed circuit board 17, a plastic sealing layer 18, a heat dissipation structure 19, a third welding layer and a driving chip 20, wherein the substrate 10 includes a top metal layer 103, a dielectric layer 102 and a bottom metal layer 101, a plurality of preset positions are set on the top metal layer 103 for mounting the chip to be packaged 14 and the copper pillar 15, the first welding layer 13 is located at the preset position, the second welding layer 16 is located above the chip to be packaged 14 and the copper pillar 15, a plurality of circuit ports 1711 are set on the lower surface 171 of the customized printed circuit board 17, and the printed A mounting area 1721 for the driver chip 20 is reserved on the upper surface 172 of the circuit board 17. The multiple circuit ports 1711 on the lower surface 171 of the customized printed circuit board 17 correspond one-to-one to and are electrically connected to the second welding layer 16. The plastic packaging layer 18 fills the gap between the substrate 10 and the printed circuit board 17, covers the edge of the substrate 10 and exposes the bottom metal layer 101 of the substrate 10, and the heat dissipation structure 19 is electrically connected to the bottom metal layer 101 of the substrate 10 to form a heat dissipation channel. The third welding layer is located in the mounting area 1721 for the driver chip 20 reserved on the upper surface 172 of the printed circuit board 17, and the driver chip 20 is mounted on the third welding layer.

[0075] Specifically, the top metal layer 103 and the bottom metal layer 101 are made of copper or other suitable conductive materials. In this embodiment, copper is used as the top metal layer 103 and the bottom metal layer 101.

[0076] Specifically, the material of the dielectric layer 102 includes Al2O3, AlN, Si3N4 or other suitable dielectric materials. In this embodiment, Si3N4 is used as the dielectric layer 102.

[0077] Specifically, under the condition of ensuring the performance of the power module, the multiple preset positions set on the top metal layer 103 can be selected according to actual conditions, and are not limited here.

[0078] Specifically, the types of the chip 14 to be packaged include MOS, IGBT, diode, thyristor or other suitable electronic devices.

[0079] Specifically, while ensuring the function of the power module, the number of chips 14 to be packaged can be set according to actual conditions and is no longer restricted here; the interconnection of electrical connections between the chips 14 to be packaged can be set according to actual conditions and is no longer restricted here.

[0080] Specifically, under the condition of ensuring the safety of various chips 14 to be packaged after electrical connection, the thickness of the plastic packaging layer 18 can be set according to actual conditions, and is not limited here.

[0081] Specifically, the heat dissipation structure 19 includes a heat dissipation base plate 191 fixed on the bottom metal layer 101 and facing away from the top metal layer 103, and heat dissipation pin fins 192 fixed on the heat dissipation base plate 191 and facing away from the bottom metal layer 101. Under the condition of ensuring the heat dissipation performance of the power module, the size and thickness of the heat dissipation base plate 191 can be selected according to actual conditions and are no longer restricted here. The heat dissipation pin fins 192 are used to increase the contact area between the heat dissipation structure 19 and the air, so that the heat conducted from the substrate 10 to the heat dissipation structure 19 can be quickly transferred to the air. The number, shape and distance between adjacent heat dissipation pin fins 192 can be selected according to actual conditions and are no longer restricted here.

[0082] Specifically, while ensuring the performance of the power module, the multiple circuit ports 1711 on the lower surface 171 of the customized printed circuit board 17 can be set according to actual conditions and are no longer restricted here; the mounting area 1721 reserved for the driving chip 20 on the upper surface 172 of the customized printed circuit board 17 can be set according to actual conditions and is no longer restricted here.

[0083] Specifically, resistors and capacitors are mounted on the third welding layer.

[0084] Specifically, a plurality of power terminals and signal terminals are provided on the upper surface 172 of the customized printed circuit board 17 for achieving electrical connection with a busbar provided by a customer.

[0085] The power module of this embodiment is packaged by adopting the packaging method of the power module described in Example 1, so that the power module can achieve the shortest distance between the chip 14 to be packaged and the bus terminal, thereby greatly reducing the circuit inductance. After the line inductance is reduced, the switching loss of the power device can also be lower.

[0086] In summary, the power module and packaging method of the present invention improve the packaging process of the packaged power module, and electrically connect the chip to be packaged with the substrate and the printed circuit board through solder paste, so that the power module can realize the shortest distance between the chip to be packaged and the bus terminal, thereby greatly reducing the circuit inductance, and after the line inductance is reduced, the switching loss of the power device can be lower, and since there is no need to pre-copper-plate the front and back of the chip to be packaged, the complexity of the packaging process is greatly reduced, so that the manufacturing cost of the power module is controlled, and the packaging method can also integrate the driver chip on the power module, compared with the prior art, so that the power module adds a driving function, which is simpler and more convenient to use. In addition, the power module obtained by the packaging method has good heat dissipation capacity and can meet the high power requirements of automobiles. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has a high industrial utilization value.

[0087] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for packaging a power module, characterized in that: The packaging method comprises at least the following steps: A substrate is provided, the substrate comprising a top metal layer, a dielectric layer, and a bottom metal layer, and a first solder paste printing is performed at a preset position on the top metal layer to form a first solder layer; Mounting the chip to be packaged and the raised copper pillars on the first welding layer; Performing a first soldering on the substrate on which the chip and the copper pillar are mounted, so that the chip to be packaged is electrically connected to the top metal layer; Performing a second solder paste printing on the chip to be packaged and the copper pillar to form a second soldering layer, and combining the substrate formed with the second soldering layer with a customized printed circuit board and loading them into a fixture, wherein a plurality of circuit ports are arranged on the lower surface of the customized printed circuit board; Soldering the fixture and the substrate for a second time so that the circuit port is electrically connected to the chip to be packaged and the second soldering layer on the copper pillar respectively; Preheating the substrate after the second welding and performing plastic sealing; Systematically welding the plastic-encapsulated substrate and the heat dissipation structure to connect the bottom metal layer with the heat dissipation structure to form a heat dissipation channel; A third solder paste printing is performed on the upper surface of the printed circuit board to form a third soldering layer, a driving chip is mounted on the third soldering layer, and a third soldering is performed simultaneously and an electrical performance test is performed.

2. The packaging method of a power module according to claim 1, characterized in that: A plurality of power terminals and signal terminals are also provided on the upper surface of the printed circuit board, and after the electrical performance test, the power terminals and the signal terminals are electrically connected to an additionally provided busbar by welding.

3. The packaging method of a power module according to claim 1, characterized in that: The type of the chip to be packaged includes at least one of MOSFET, IGBT, diode or thyristor.

4. The packaging method of a power module according to claim 1, characterized in that: The second welding layer occupies 50% to 90% of the area of ​​the chip to be packaged, and the second welding layer occupies 50% to 90% of the top area of ​​the copper column.

5. The packaging method of a power module according to claim 1, characterized in that: The heat dissipation structure comprises a heat dissipation base plate fixed on the bottom metal layer and away from the top metal layer, and a heat dissipation pin fin fixed on the heat dissipation base plate and away from the bottom metal layer.

6. The method for packaging a power module according to claim 1, wherein: After the first welding, the method further includes a step of surface treating the substrate on which the chip to be packaged and the copper pillar are mounted. After the second welding, the method further includes a step of surface treating the substrate, wherein the surface treatment method includes multi-stage ultrasonic cleaning.

7. The method for packaging a power module according to claim 1, wherein: Oxygen-free copper, bare copper, nickel-plated copper or tin-plated copper is arranged on the circuit port, and the circuit port corresponds to the chip to be packaged and the area of ​​the copper column on the substrate one by one.

8. The method for packaging a power module according to claim 1, wherein: The third welding layer also has resistors and capacitors mounted on it.

9. The packaging method of a power module according to claim 1, characterized in that: The type of the substrate includes a ceramic double-sided copper-clad substrate, and the top metal layer and the bottom metal layer have the same thickness.

10. A power module, characterized in that: The power module is packaged by using the power module packaging method according to any one of claims 1 to 9.

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