Silicon carbide power module packaging structure and method

Abstract

The invention belongs to the field of semiconductor devices, and discloses a silicon carbide power module packaging structure, which comprises a circuit substrate, and a heat dissipation bottom plate and an insulation sealing element which are respectively arranged on two sides of the circuit substrate, a heat dissipation fin array is arranged on the surface of one side, far away from the circuit substrate, of the heat dissipation bottom plate, and glue locking grooves are formed in the other surfaces, except the surface where the heat dissipation fin array is located, of the heat dissipation bottom plate; the insulation sealing element wraps the circuit substrate and the surface connected with the heat dissipation bottom plate, the glue locking groove is filled with the insulation sealing element, the insulation sealing element and the heat dissipation bottom plate are mutually nested through the glue locking groove, the heat dissipation fin array is exposed out of the insulation sealing element, and the heat dissipation fin array is exposed out of the insulation sealing element. According to the invention, the technical problem that the reliability of the module is influenced by layering and cracking of the plastic package body due to mismatching of thermal expansion coefficients between the heat dissipation bottom plate and the plastic package body is solved.

Description

Technical Field

[0001] This application belongs to the field of semiconductor devices, specifically relating to a silicon carbide power module packaging structure and method. Background Technology

[0002] With the increasing demands for power density and reliability in power electronic systems from fields such as new energy vehicles, rail transit, and industrial frequency converters, wide-bandgap semiconductor power devices, represented by silicon carbide (SiC), are being widely used. In traditional power module packaging solutions, epoxy resin and other molding materials are typically used to encapsulate the direct copper-clad ceramic (CCC) substrate for electrical insulation and mechanical protection. This structure has multiple thermal interfaces and material layers, resulting in high thermal resistance and a long heat dissipation path, making it difficult to effectively dissipate the high-density heat generated by the SiC chip. To improve heat dissipation efficiency, the industry has begun to develop integrated thermal packaging technology. For example, a metal heat sink with a pin-fin structure is directly bonded to the circuit board and encapsulated using molding compound. The pin-fin portion can be directly immersed in coolant, forming a highly efficient liquid cooling channel. However, while improving heat dissipation performance, this structure introduces new reliability risks. The significant difference in the coefficients of thermal expansion (CTE) between the metal heat sink and the encapsulating epoxy resin means the module needs to withstand substantial temperature cycling. The two mismatched CTE materials generate enormous alternating thermal stress at the bonding interface. This stress can easily cause delamination at the interface between the molding compound and the metal base plate, and may even cause the molding compound itself to crack, which severely restricts the application of such efficient heat dissipation packaging solutions in high-reliability fields. Summary of the Invention

[0003] This application provides a silicon carbide power module packaging structure and method, which solves the technical problem that the mismatch in thermal expansion coefficients between the integrated metal heat sink and the outer plastic package can easily lead to delamination or cracking of the plastic package during temperature cycling, thereby affecting the reliability of the module.

[0004] To solve the above-mentioned technical problems, this application provides a silicon carbide power module packaging structure, including: a circuit board and a heat dissipation base plate and an insulating seal respectively disposed on both sides of the circuit board; The heat dissipation base plate has a heat dissipation fin array on the side surface away from the circuit board, and the heat dissipation base plate has a locking groove on the other surfaces except the surface where the heat dissipation fin array is located. The insulating sealant covers the circuit board and the surface connected to the heat dissipation base plate, and fills the locking groove, so that the insulating sealant and the heat dissipation base plate are nested together through the locking groove, and the heat dissipation fin array is exposed outside the insulating sealant.

[0005] Furthermore, the adhesive locking groove includes a first adhesive locking groove, a second adhesive locking groove, a third adhesive locking groove, and a fourth adhesive locking groove. The first adhesive locking groove and the second adhesive locking groove are disposed on the side of the heat dissipation base plate that connects to the circuit board, and the second adhesive locking groove is connected between the first adhesive locking groove and the side of the heat dissipation base plate. The third and fourth locking grooves are located on the side of the heat dissipation base plate, with the third locking groove parallel to the side edge of the heat dissipation base plate.

[0006] Furthermore, the first locking groove is a square locking groove, and each side of the first locking groove is parallel to the adjacent side of the heat dissipation base plate. The second locking groove and the third locking groove are both line segment locking grooves. The fourth locking groove is a V-shaped locking groove, and the V-shaped opening of the fourth locking groove is set towards the side of the circuit board.

[0007] Furthermore, the heat dissipation fin array is a needle-shaped heat dissipation fin array, and the heat dissipation fin array is integrally formed with the heat dissipation base plate.

[0008] This application also provides a silicon carbide power module packaging method, including: A corrosion-resistant coating is formed on the surface of the heat dissipation base plate by electroplating. Remove the corrosion-resistant coating from the connection surface on the heat dissipation base plate that is intended to contact the insulating seal; The connecting surfaces are machined to form locking grooves for nesting with the insulating sealant; The connecting surfaces after removing the corrosion-resistant material are subjected to plasma cleaning; A layer of interface material is sprayed onto the cleaned joint surface; The processed heat dissipation base plate and the circuit components assembled with the heat dissipation base plate are placed into the molding die, and the molding die is pre-bent. Liquid epoxy resin is poured into the pre-bent molding die, and after curing, it forms an insulating seal that covers the circuit components and is bonded to the heat dissipation base plate through the interface layer.

[0009] Furthermore, the interface layer material includes a first type of functional group and a second type of functional group, wherein the first type of functional group is used to bond with the metal surface of the heat dissipation base plate, and the second type of functional group is used to bond with the epoxy resin material.

[0010] Furthermore, the connecting surface is roughened, which includes processing with a laser or a cutting tool to form a three-dimensional morphology on the roughened connecting surface, and the surface height difference of the three-dimensional morphology is greater than 0.05 mm.

[0011] Furthermore, based on the expected warpage after the power module product is encapsulated and cured, the initial flatness of the incoming heat dissipation base plate is pre-bent to compensate, and the cavity surface of the encapsulation mold is pre-bent in the reverse direction to adjust, wherein the expected warpage is 0.1mm to 1.2mm.

[0012] Furthermore, the cast liquid epoxy resin material contains inorganic fillers, and the inorganic fillers have a mass fraction of 70% to 90% in the epoxy resin material.

[0013] Furthermore, the inorganic filler is one or more of silicon dioxide, aluminum oxide, silicon nitride, aluminum nitride, and calcium carbonate.

[0014] This application utilizes a locking groove on the surface of the heat sink base plate to allow the insulating sealant to flow into and fill the groove during injection molding and curing, forming a robust mechanical interlocking structure with the heat sink base plate. This physical nesting enhances the bonding force between the two materials, effectively resisting shear stress generated during temperature cycling due to differences in thermal expansion coefficients, thereby suppressing the risk of interface delamination and molding cracking. The heat sink base plate's heat dissipation fin array is directly exposed to the coolant, ensuring low thermal resistance and high heat dissipation capacity, meeting the heat dissipation requirements of silicon carbide power modules operating at high power density. Pre-bending of the molding die ensures that the heat sink base plate and circuit components are under predetermined stress before encapsulation, partially offsetting the internal stress generated by differences in material thermal expansion coefficients during encapsulation, curing, and subsequent operation. Plasma cleaning efficiently and uniformly removes surface organic contaminants and oxides, and the intermediate layer of interface material is sprayed onto the surface, resulting in a stable and highly active surface state, ensuring uniformity and high strength of the interface bonding. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application 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 a part of the embodiments of this application, and not all of the embodiments. For those skilled in the art, other drawings obtained from these drawings without creative effort are all within the scope of protection of this application.

[0016] Figure 1 This is a schematic diagram of a silicon carbide power module packaging structure provided in an embodiment of this application.

[0017] Figure 2 for Figure 1 A schematic diagram of the first structure of the heat dissipation base plate.

[0018] Figure 3 for Figure 2 A schematic diagram of the second structure of the heat dissipation base plate.

[0019] Figure 4 This is a flowchart of a silicon carbide power module packaging method.

[0020] Explanation of reference numerals in the attached figures: 1-Heat dissipation base plate, 2-Insulating sealant, 3-Circuit board, 4-Pin; 11-Heat dissipation fin array, 12-First adhesive groove, 13-Second adhesive groove, 14-Third adhesive groove, 15-Fourth adhesive groove. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0022] To make the description of this disclosure more detailed and complete, illustrative descriptions of the implementation methods and specific embodiments of this application are provided below; however, this is not the only form of implementing or utilizing the specific embodiments of this application. The implementation methods cover the features of multiple specific embodiments and the method steps and their order for constructing and operating these specific embodiments. However, other specific embodiments can also be used to achieve the same or equivalent functions and step sequences. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] Figure 1 This is a schematic diagram of a silicon carbide power module packaging structure provided in an embodiment of this application, as shown below. Figure 1As shown, the silicon carbide power module packaging structure includes a circuit board 3 and a heat dissipation base plate 1 and an insulating seal 2 respectively disposed on both sides of the circuit board 3. The circuit board 3 has conductive lines and a power semiconductor chip mounting area. The heat dissipation base plate 1 is a pin-fin heat dissipation base plate disposed on one side of the circuit board 3. Its surface away from the circuit board 3 has an integrally formed heat dissipation fin array 11, which is a needle-shaped array. The insulating seal 2 covers part of the surface of the circuit board, the power semiconductor chip, and part of the electrical connection structure, and extends to cover the peripheral area of ​​the heat dissipation base plate 1, exposing the heat dissipation fin array 11 to the external environment. The heat dissipation fin array 11 of the heat dissipation base plate is directly immersed in the coolant, ensuring low thermal resistance and high heat dissipation capacity, which can meet the heat dissipation requirements of the silicon carbide power module under high power density operation. The insulating seal is made of insulating epoxy resin. The packaging structure also includes multiple pins 4. The pins 4 are partially embedded in the insulating seal 2 and electrically connected to the conductive lines on the circuit board 3, and partially extend outward to provide an external electrical connection interface. The insulating sealant 2 covers and seals the circuit board 1 and the connection parts, ensuring electrical insulation performance and moisture and dirt protection.

[0024] Figure 2 for Figure 1 A schematic diagram of the first structure of the heat dissipation base plate. Figure 3 for Figure 1 A schematic diagram of the second structure of the heat dissipation base plate. (See diagram below.) Figure 2 As shown, the outer surface of the heat dissipation base plate 1 is provided with a locking groove, wherein the first locking groove 12 and the second locking groove 13 are provided on the side where the heat dissipation base plate 1 and the circuit board 3 are connected. The first locking groove 12 is a square locking groove. The square locking groove is provided close to the side of the heat dissipation base plate, providing a local anchoring area to bear and disperse the main stress from the side. The second adhesive groove 13 consists of several line segments. The second adhesive groove 13 connects the first adhesive groove 12 and the side of the heat dissipation base plate 1. The second adhesive groove 13 is set perpendicular to the first adhesive groove. The second adhesive groove 13 acts as a reinforcing rib, effectively transmitting the anchoring effect of the square adhesive groove to the edge of the heat dissipation base plate, avoiding excessive stress concentration in a local area. At the same time, it increases the flow path of epoxy resin on the horizontal plane and enhances the bonding ability of the substrate connection surface edge.

[0025] The heat dissipation base plate 1 has three locking grooves 14 parallel to the sides of each of its four sides, with two sets of these grooves on each side. These three locking grooves 14 form multiple annular locking structures on the vertical sides of the heat dissipation base plate. After the epoxy resin fills and cures these grooves, it effectively resists the tendency for the insulating sealant to peel off from the heat dissipation base plate 1 in the vertical direction.

[0026] Figure 3This is a schematic diagram of the second structure of the heat dissipation base plate. The structure of the first locking groove 12 is the same as that in the first structural schematic diagram. The second locking groove 13 consists of several sets of line segment locking grooves. Each set of line segment locking grooves includes two locking grooves perpendicular to the side and one locking groove not perpendicular to the side. A third locking groove 14 is provided on one set of opposite sides of the heat dissipation base plate. The third locking groove 14 is parallel to the side. A fourth locking groove 15 is provided on another set of opposite sides of the heat dissipation base plate 1. The fourth locking groove 15 is a V-shaped locking groove, with its opening facing the circuit board 3. The fourth locking groove 15 is a preferred structure. When the V-shaped groove is subjected to a tensile force perpendicular to its opening direction, the groove wall will exert an oblique squeezing force on the cured resin filled in it, which can effectively resist the tendency of the insulating sealant to peel off from the side of the heat dissipation base plate and provide a stronger mechanical locking force than a simple parallel groove.

[0027] By setting a locking groove on the surface of the heat dissipation base plate 1, the insulating sealant can flow into and fill the groove during the injection molding and curing process, forming a strong mechanical interlocking structure with the heat dissipation base plate 1. This physical nesting combination enhances the bonding force between the two materials, effectively resisting the shear stress generated during temperature cycling due to the difference in thermal expansion coefficients, thereby suppressing the risk of interface delamination and molding cracking, and improving the reliability of the module.

[0028] Figure 4 A flowchart of a silicon carbide power module packaging method includes: S1 forms a corrosion-resistant coating on the surface of the heat dissipation base plate through an electroplating process; Optionally, a layer of nickel can be electroplated on the surface of the heat sink base plate to block the direct corrosion of the underlying metal by the cooling medium and prevent corrosion and oxidation of the heat sink base plate.

[0029] S2 Remove the corrosion-resistant coating from the connection surface of the heat dissipation base plate that is intended to contact the insulating seal; Optionally, the step of removing the corrosion-resistant material includes surface roughening of the connecting surface. This is achieved by laser processing or machining to create a rough surface with a specific three-dimensional undulating structure, where the peak-valley height difference of the surface profile is greater than 0.05 mm. This roughening process enhances the physical bonding strength of the connecting surface. The resulting microscopic three-dimensional undulating structure increases the effective contact area of ​​the metal surface, providing a more sufficient adhesion substrate for the subsequent sprayed interface layer material. Simultaneously, during the molding process, the epoxy resin can more thoroughly impregnate and fill these rough surfaces.

[0030] S3 processes the connecting surface to form a locking groove for nesting with the insulating sealant; by setting the locking groove on the surface of the heat dissipation base plate, the insulating sealant can flow into and fill these grooves during the injection molding and curing process, forming a strong mechanical interlocking structure with the heat dissipation base plate, which enhances the bonding force of the two material interfaces, effectively resists the shear stress generated by the difference in thermal expansion coefficients during temperature cycling, and suppresses the risk of interface delamination and molding cracking.

[0031] S4 performs plasma cleaning on the connecting surface after removing the corrosion-resistant material; Optionally, the plasma cleaning process uses gases such as hydrogen, argon, or mixtures thereof to generate plasma under vacuum or specific pressure conditions. The active particles in the plasma are used to treat the surface of the connection surface. This process provides deep cleaning and surface activation to the roughened metal connection surface. The high-energy particles in the plasma effectively bombard and remove residual trace organic contaminants, oxides, and adsorbed water vapor, resulting in a clean substrate surface. Simultaneously, active groups are introduced onto the metal surface, increasing its surface energy.

[0032] S5 Sprays an interface layer material onto the cleaned connecting surface; Optionally, an interface layer material is coated onto the bonding surface after plasma cleaning using a spraying process. This interface material contains two types of functional groups in its molecular structure: the first type is designed to form chemical bonds or strong physical adsorption with the metal surface of the heat sink base; the second type is designed to chemically react with the subsequently poured liquid epoxy resin. By constructing a chemically and physically bonded transition layer between these two materials with vastly different properties—metal and epoxy resin—interfacial stress and thermal stress caused by the mismatch in coefficients of thermal expansion can be more effectively transferred and dispersed, thereby reducing the risk of interface delamination.

[0033] S6. The processed heat dissipation base plate and the circuit components assembled with the heat dissipation base plate are placed into the molding die, and the molding die is pre-bent. Optionally, based on the expected warpage after the power module product is encapsulated and cured, the initial flatness of the incoming heat dissipation base plate is pre-bent to compensate, and the cavity surface of the encapsulation mold is pre-bent in the reverse direction to adjust, wherein the expected warpage is 0.1 mm to 1.2 mm.

[0034] For example, through preliminary process tests, it is known that for a specific design of silicon carbide power module, after its epoxy resin molding compound is fully cured and cooled to room temperature, the heat dissipation base plate will arch upward toward the insulating seal side. The maximum warpage at the center point is measured and predicted to be +0.5mm, with the positive sign indicating upward bending.

[0035] Before encapsulating the heat sink base plate, a jig is used to bend it into a shape opposite to the expected warpage. Circuit components are soldered onto the bent heat sink base plate, and the circuit components and heat sink base plate are encapsulated. The encapsulated heat sink base plate is then placed into a molding die. The cavity surface of the molding die that contacts the heat sink base plate is pre-bent, forming a non-planar contour that matches the pre-deformed shape of the heat sink base plate. This pre-sets the warpage change during the epoxy resin molding and cooling curing process in the springback of the mold cavity and the heat sink base plate. During the resin curing and cooling process, the stress that causes the heat sink base plate to warp in a certain direction due to material shrinkage differences is counteracted by the pre-stored springback stress of the heat sink base plate itself and the reverse constraint force of the mold cavity, thus achieving warpage control.

[0036] S7 pours liquid epoxy resin into the pre-bent molding die, and after curing, forms an insulating sealant that covers the circuit components and is bonded to the heat dissipation base plate through the interface layer.

[0037] Optionally, inorganic filler particles are uniformly dispersed in the liquid epoxy resin material. The inorganic filler is one or more of the following: silica, alumina, silicon nitride, aluminum nitride, and calcium carbonate. The mass fraction of the inorganic filler in the epoxy resin matrix is ​​in the range of 70% to 90%. By adding inorganic fillers, the coefficient of thermal expansion of the pure epoxy resin cured body can be reduced, making it closer to the coefficient of thermal expansion of the heat-dissipating metal base plate, thereby reducing the thermal stress caused by the difference in expansion and contraction between the two during temperature changes.

[0038] In one embodiment, the encapsulation method includes all steps S1 to S7.

[0039] In another embodiment, some steps S2 to S6 can be selectively implemented according to actual process requirements, instead of executing the entire process. This flexible combination of steps allows the packaging method to adapt to different application scenarios, cost control, or reliability level requirements.

[0040] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0041] The above embodiments merely illustrate preferred implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention should be determined by the appended claims.

Claims

1. A silicon carbide power module packaging structure, characterized in that, include: The circuit board and the heat dissipation base plate and the insulating seal respectively disposed on both sides of the circuit board; The heat dissipation base plate has a heat dissipation fin array on the side surface away from the circuit board, and the heat dissipation base plate has a locking groove on the other surfaces except the surface where the heat dissipation fin array is located. The insulating sealant covers the circuit board and the surface connected to the heat dissipation base plate, and fills the locking groove, so that the insulating sealant and the heat dissipation base plate are nested together through the locking groove, and the heat dissipation fin array is exposed outside the insulating sealant.

2. The silicon carbide power module packaging structure as described in claim 1, characterized in that, The adhesive locking groove includes a first adhesive locking groove, a second adhesive locking groove, a third adhesive locking groove and a fourth adhesive locking groove. The first adhesive locking groove and the second adhesive locking groove are disposed on the side of the heat dissipation base plate that connects to the circuit board. The second adhesive locking groove is connected between the first adhesive locking groove and the side of the heat dissipation base plate. The third and fourth locking grooves are located on the side of the heat dissipation base plate, with the third locking groove parallel to the side edge of the heat dissipation base plate.

3. The silicon carbide power module packaging structure as described in claim 2, characterized in that, The first adhesive groove is a square adhesive groove, and each side of the first adhesive groove is parallel to the adjacent side of the heat dissipation base plate. The second and third adhesive grooves are both line segment adhesive grooves. The fourth adhesive groove is a V-shaped adhesive groove, and the V-shaped opening of the fourth adhesive groove is set towards the side of the circuit board.

4. The silicon carbide power module packaging structure as described in claim 1, characterized in that, The heat dissipation fin array is a needle-shaped heat dissipation fin array, and the heat dissipation fin array is integrally formed with the heat dissipation base plate.

5. A silicon carbide power module packaging method, characterized in that, include: A corrosion-resistant coating is formed on the surface of the heat dissipation base plate by electroplating. Remove the corrosion-resistant coating from the connection surface of the heat dissipation base plate that is intended to contact the insulating seal; The connecting surfaces are machined to form locking grooves for nesting with the insulating sealant; The connecting surfaces after the corrosion-resistant material has been removed are subjected to plasma cleaning; A layer of interface material is sprayed onto the cleaned joint surface; The processed heat dissipation base plate and the circuit components assembled with the heat dissipation base plate are placed into the molding die, and the molding die is pre-bent. Liquid epoxy resin is poured into the pre-bent molding die, and after curing, it forms an insulating seal that covers the circuit components and is bonded to the heat dissipation base plate through the interface layer.

6. The silicon carbide power module packaging method as described in claim 5, characterized in that, The interface layer material includes a first type of functional group and a second type of functional group. The first type of functional group is used to bond with the metal surface of the heat dissipation base plate, and the second type of functional group is used to bond with the epoxy resin material.

7. The silicon carbide power module packaging method as described in claim 5, characterized in that, The removal of the corrosion-resistant material from the predetermined contact surface of the heat dissipation base plate with the insulating seal includes: The connecting surface is roughened by means of laser or cutting tool to form a three-dimensional shape, wherein the surface height difference of the three-dimensional shape is greater than 0.05 mm.

8. A silicon carbide power module packaging method as described in claim 5, characterized in that, The pre-bending process of the molding die includes: Based on the expected warpage after the power module product is encapsulated and cured, the initial flatness of the incoming heat dissipation base plate is pre-bent to compensate, and the cavity surface of the encapsulation mold is pre-bent in the reverse direction to adjust, wherein the expected warpage is 0.1mm to 1.2mm.

9. A silicon carbide power module packaging method as described in claim 5, characterized in that, The cast liquid epoxy resin material contains inorganic fillers, and the inorganic fillers have a mass fraction of 70% to 90% in the epoxy resin material.

10. A silicon carbide power module packaging method as described in claim 5, characterized in that, The inorganic filler is one or more of silicon dioxide, aluminum oxide, silicon nitride, aluminum nitride, and calcium carbonate.

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