An injection molded power module with a spray-on die attach interface coupling agent

Abstract

The utility model provides a kind of injection molding power module of spraying chip interface coupling agent, belong to power module technical field, including ceramic substrate, chip, diode, lead frame and plastic package shell, chip, diode and lead frame are set on ceramic substrate, and ceramic substrate, chip, diode and lead frame are encapsulated in plastic package shell, further including chip interface coupling agent reinforcing layer, respectively spray solidification in the surface of ceramic substrate, chip, diode and lead frame, and chip interface coupling agent reinforcing layer is encapsulated in plastic package shell. Advantageous effect: through chip interface coupling agent reinforcing layer, by the synergistic effect of high energy storage modulus and low thermal expansion coefficient, provide high temperature resistance, water resistance, high insulation, high bonding strength and thermal stress buffering and other multilayer protection, greatly optimize the thermal management, mechanical stress and electrical performance of silicon carbide power module, prolong the expected service life of module, improve its regular cycle life.

Description

Technical Field

[0001] This utility model relates to the field of power module technology, and in particular to an injection-molded power module with a chip interface coupling agent sprayed on it. Background Technology

[0002] Silicon carbide (SiC) power modules use silicon carbide semiconductors as switching elements. Leveraging their high voltage withstand capability, high temperature resistance, and high frequency characteristics, they achieve highly efficient power conversion, significantly improving the performance of power electronic devices. Compared to traditional power modules, SiC power modules have higher conversion efficiency, effectively reducing energy loss and lowering equipment operating costs. Furthermore, SiC power modules are available in various types and specifications, allowing for flexible selection based on different application scenarios and needs. Therefore, they are widely used in numerous fields such as electric vehicles, photovoltaic inverters, wind power generation, rail transportation, and industrial drives, offering advantages such as energy saving, environmental protection, improved performance, and reduced costs.

[0003] Especially in the field of new energy vehicles, with the rapid development of the electric vehicle market, the demand for silicon carbide power modules is increasing day by day, which puts forward higher requirements for the high reliability of automotive silicon carbide power modules. This requires further improvement of the process and packaging of automotive silicon carbide power modules.

[0004] In traditional power device packaging processes, improving the reliability of silicon carbide power modules involves not only high-quality silicon carbide chips but also focusing on the module packaging itself. Currently, power modules are typically encapsulated in epoxy resin, but epoxy resin is susceptible to moisture corrosion. In high-temperature environments, moisture penetration can lead to passivation layer corrosion or encapsulation delamination, ultimately causing module failure. This severely impacts the reliability and lifespan of silicon carbide power modules, limiting their further promotion and application in fields with high reliability requirements, such as new energy vehicles. Utility Model Content

[0005] To address the above technical problems, this utility model provides an injection-molded power module with a chip interface coupling agent sprayed on it.

[0006] The technical problem solved by this utility model can be achieved by the following technical solution: An injection-molded power module with a chip interface coupling agent sprayed on it includes a ceramic substrate, a chip, a diode, a lead frame, and a plastic encapsulation shell. The chip, the diode, and the lead frame are disposed on the ceramic substrate, and the ceramic substrate, the chip, the diode, and the lead frame are encapsulated within the plastic encapsulation shell. The module further includes: A chip interface coupling agent reinforcement layer is sprayed and cured onto the surfaces of the ceramic substrate, the chip, the diode, and the lead frame, respectively, and the chip interface coupling agent reinforcement layer is encapsulated within the plastic encapsulation shell.

[0007] Preferably, the chip interface coupling agent reinforcement layer uses a chip interface coupling agent material, which is in the form of a solution mixture and is sprayed onto the surfaces of the ceramic substrate, the chip, the diode, the bonding points, and the solder joints of the lead frame.

[0008] Preferably, the thickness of the chip interface coupling agent reinforcement layer is 10μm to 50μm.

[0009] Preferably, the power electrode on the front side of the chip is connected to the back side of the chip copper foil, the front side of the diode is connected to the back side of the diode copper foil, and the front side of the chip copper foil is connected to the front side of the diode copper foil and the circuit area of ​​the ceramic substrate.

[0010] Preferably, the diode is connected to the diode copper foil and to the ceramic substrate using a silver paste sintering process.

[0011] Preferably, the power electrode on the front side of the chip is connected to the back side of the chip copper foil, and the back side of the chip is connected to the circuit area on the front side of the ceramic substrate using a silver paste sintering process.

[0012] Preferably, the sintering temperature in the silver paste sintering process is 200℃-300℃, and the sintering pressure is 20Mpa-70Mpa.

[0013] Preferably, the power electrode of the chip is connected to the copper foil of the chip, and the power electrode of the chip is connected to the copper foil of the diode by copper wire bonding.

[0014] Preferably, the ceramic substrate is a silicon nitride ceramic substrate prepared by active metal brazing process.

[0015] Preferably, the encapsulated shell is made of epoxy resin material.

[0016] The advantages or beneficial effects of this utility model's technical solution are as follows: This invention forms a chip interface coupling agent reinforcement layer by spraying and curing it onto the surface of a ceramic substrate, chip, diode, and lead frame. This reinforcement layer, through the synergistic effect of high energy storage modulus and low thermal expansion coefficient, provides multi-layer protection such as high temperature resistance, water resistance, high insulation, high bonding strength, and thermal stress buffering. It significantly optimizes the thermal management, mechanical stress, and electrical performance of silicon carbide power modules, extends the expected service life of the modules, and improves their regular cycle life. Attached Figure Description

[0017] Figure 1 This is a front view of the injection molding power module with sprayed chip interface coupling agent in a preferred embodiment of the present invention. Figure 2 This is a schematic diagram of the power module without an injection-molded housing, which is a preferred embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures: 1. Chip; 11. Chip copper foil; 2. Ceramic substrate; 3. Diode; 31. Diode copper foil; 4. Lead frame; 5. Chip interface coupling agent reinforcement layer; 6. Plastic encapsulation shell; 7. Aluminum wire; 8. Copper wire. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention.

[0022] In a preferred embodiment of this utility model, based on the above-mentioned problems existing in the prior art, an injection-molded power module with a sprayed chip interface coupling agent is provided, such as... Figure 1 and Figure 2 As shown, it includes: Ceramic substrate 2, the front side of ceramic substrate 2 includes a circuit area and a signal area; Chip 1, the back side of chip 1 is connected to the circuit area on the front side of ceramic substrate 2, the gate of chip 1 is connected to the signal area on the front side of ceramic substrate 2, and the power electrode on the front side of chip 1 is connected to the circuit area on the front side of ceramic substrate 2. In this embodiment, chip 1 is preferably a silicon carbide chip. Of course, it is not limited to this and other types of power chips can also be used.

[0023] Diode 3 has its back side connected to the circuit area of ​​ceramic substrate 2, and its front side connected to the power electrode of chip 1. The lead frame 4 has its pins connected to the circuit area on the front side of the ceramic substrate 2 by laser welding, and its terminals are connected to the external circuit by laser welding. Chip interface coupling agent reinforcement layer 5 is sprayed and cured on the solder joint surfaces of ceramic substrate 2, chip 1, diode 3, bonding point and lead frame 4 respectively. The ceramic substrate 2, the chip 1, the diode 3, the lead frame 4, and the chip interface coupling agent reinforcement layer 5 are encapsulated within the plastic casing 6.

[0024] In a preferred embodiment of this invention, the plastic-encapsulated shell 6 is made of epoxy resin material.

[0025] Specifically, in this embodiment, epoxy resin is used for encapsulation. Epoxy resin has advantages such as excellent thermal stability and high reliability temperature certification, allowing the automotive power module to achieve a reliability temperature of over 200°C. Laser welding is used to connect the lead frame 4 and the front side of the ceramic substrate 2, which improves the module's temperature shock resistance and prevents the lead frame 4 from detaching from the front side of the ceramic substrate 2.

[0026] In this embodiment, the ceramic substrate 2 is a silicon nitride (Si3N4) ceramic substrate prepared by active metal bonding (AMB) process.

[0027] Specifically, in this embodiment, the Si3N4 ceramic substrate is a composite substrate formed by high-temperature welding of a copper layer to a silicon nitride ceramic plate using an active metal solder. It possesses advantages such as high thermal conductivity, low coefficient of thermal expansion, high bonding strength, and high reliability, making it suitable for high-power, high-temperature, and high-frequency semiconductor packaging applications, such as SiC and GaN. The Si3N4 ceramic substrate represents a further development of direct-bonded ceramic (DBC) substrates. Compared to DBC, the Si3N4 ceramic substrate can utilize a wider variety of ceramic materials, reduces welding temperature, and improves heat dissipation and insulation performance.

[0028] In a preferred embodiment of this utility model, such as Figure 2 As shown, the power electrode on the front of chip 1 is connected to the back of chip copper foil 11, the front of diode 3 is connected to the back of diode copper foil 31, and the front of chip copper foil 11 is connected to the front of diode copper foil 31 and the circuit area of ​​ceramic substrate 2.

[0029] In a preferred embodiment of the present invention, the power electrode of chip 1 is bonded to the chip copper foil 11, and the power electrode of chip 1 is bonded to the diode copper foil 31 by copper wire 8.

[0030] Specifically, in this embodiment, the copper foil used is oxygen-free copper with high conductivity and high thermal conductivity, and it covers the entire front power electrode of chip 1, which can improve the heat dissipation of chip 1; the power electrode of chip 1 is connected to the front area of ​​diode copper foil 31 and the circuit area on the front of Si3N4 ceramic substrate respectively through copper wire bonding process.

[0031] In this embodiment, the diameter of the copper wire 8 is about 12 mil. The copper wire 8 of the power electrode can improve the power cycling capability of the module and prevent the bonding points from detaching from the surface.

[0032] In this embodiment, the diameter of the aluminum wire 7 is about 12 mil, which is used to connect the gate of the chip 1 and the signal area on the front side of the ceramic substrate 2.

[0033] In this embodiment, the bonding points refer to the bonding points of all aluminum wires 7 and copper wires 8, including the bonding points of the gate of chip 1, the signal area on the front side of ceramic substrate 2, the front side of chip copper foil 11, the front side of diode copper foil 31, and the line bonding points of the circuit area of ​​ceramic substrate 2.

[0034] In a preferred embodiment of the present invention, the diode 3 is connected to the diode copper foil 31 and to the ceramic substrate 2 by a silver paste sintering process.

[0035] In a preferred embodiment of the present invention, the power electrode on the front side of the chip 1 is connected to the back side of the chip copper foil 11, and the back side of the chip 1 is connected to the circuit area on the front side of the ceramic substrate 2 using a silver paste sintering process.

[0036] In a preferred embodiment of this invention, the sintering temperature in the silver paste sintering process is 200℃-300℃, and the sintering pressure is 20Mpa-70Mpa.

[0037] In a preferred embodiment of the present invention, the pins of the lead frame 4 are connected to the circuit area of ​​the ceramic substrate 2 by laser welding, and the terminals of the lead frame 4 are connected to the external circuit by laser welding.

[0038] In a preferred embodiment of this utility model, the chip interface coupling agent reinforcement layer 5 is made of chip interface coupling agent material. The chip interface coupling agent material is in the form of a solution mixture, which is easy to operate. It is sprayed onto the solder joint surfaces of the ceramic substrate 2, chip 1, diode 3, bonding points and lead frame 4, and cured in segments.

[0039] In a preferred embodiment of this invention, the segmented curing is performed in two stages, wherein the first stage curing temperature is 80°C and the curing time is 1 hour; the second stage curing temperature is 210°C and the curing time is 1 hour.

[0040] In a preferred embodiment of this invention, the thickness of the chip interface coupling agent reinforcement layer 5 is 10μm to 50μm.

[0041] Specifically, in this embodiment, the chip interface coupling agent is sprayed onto the surfaces of the ceramic substrate 2, chip 1, diode 3, bonding points, and lead frame 4 solder joints using specialized equipment after bonding and before epoxy encapsulation. A segmented curing method of 80℃*1h+210℃*1h is employed to form a chip interface coupling agent reinforcement layer 5 with a thickness of 10μm~50μm. This interface coupling agent exhibits excellent thermal stability, capable of withstanding continuous operating temperatures up to 280℃ or even higher, and can even withstand short-term high temperatures up to 310℃, ensuring that thermal decomposition, deformation, or other problems will not occur.

[0042] The chip interface coupling agent reinforcement layer 5 formed by curing this invention can provide five-fold protection for the silicon carbide power module, and its specific functions are as follows: Function 1: High-temperature bonding layer The chip interface coupling agent reinforcement layer 5 forms a high-temperature bonding layer on the surfaces of chip 1 and diode 3. This bonding layer exhibits excellent thermal stability, with a glass transition temperature Tg ≥ 310℃ and a decomposition temperature Td ≥ 380℃. Under these high-temperature conditions, no thermal decomposition or deformation occurs, ensuring the stability and reliability of the power module in high-temperature environments.

[0043] Function 2: Strengthening and protecting the solder joints The chip interface coupling agent reinforcement layer 5 forms a solder joint reinforcement layer on the surface of the bonding points and the solder joints of chip 1, diode 3, and lead frame 4. The tensile strength of this reinforcement layer exceeds 172 MPa, which enhances the connection strength of the solder joints, reduces the risk of solder joint failure, and improves the tensile performance of the power module.

[0044] Function 3: Water-blocking protective layer The chip interface coupling agent reinforcement layer 5 acts as a water-blocking layer. It is non-tracking and has a low water absorption rate, which reduces the path of moisture penetration. The water absorption rate of the chip interface coupling agent reinforcement layer 5 can be reduced to 0.1% - 0.2%, which significantly reduces the risk of module failure such as passivation layer corrosion or encapsulation delamination caused by moisture penetration.

[0045] Because the potting materials for silicon carbide power modules typically need to meet high temperature resistance requirements (HTG > 200-230℃), the higher the HTG, the higher the water absorption rate of the epoxy resin molding compound tends to be. Secondly, although the Comparative Tracking Index (CTI) of epoxy resin can reach 400-600, as a thermosetting material, it easily forms conductive paths (tracking) after surface curing, and these tracks are highly susceptible to moisture erosion. The water-blocking properties of the chip interface coupling agent reinforcement layer 5 effectively solve this problem.

[0046] Function 4: Insulating protective layer The chip interface coupling agent reinforcement layer 5 also possesses excellent insulation properties, with a breakdown voltage ≥300V / μm. Typically, epoxy resin materials require the addition of particle trapping agents to improve insulation, but excessive addition can negatively impact performance, making it difficult to meet the insulation requirements of 1200V SiC power modules. However, the chip interface coupling agent reinforcement layer 5, with a breakdown voltage ≥300V / μm, meets the insulation requirements of 1700V SiC power modules. Therefore, conventional epoxy resin materials can be used without altering the material formulation, avoiding increased procurement costs and reducing reliance on expensive epoxy resins.

[0047] Function 5: Stress buffer layer The chip interface coupling agent reinforcement layer 5 can serve as a stress buffer layer. Its coefficient of thermal expansion (CTE) is approximately 84 ppm / ℃, which can solve the problem of interface tearing or solder joint fatigue that occurs during thermal cycling due to the large difference in the coefficients of thermal expansion between silicon carbide (SiC) chips (CTE ≈ 4.5 ppm / ℃) and copper substrates (CTE ≈ 17 ppm / ℃), thus ensuring the structural stability and reliability of the power module.

[0048] This invention involves spraying a new encapsulation material, also known as a chip interface coupling agent, between the silicon carbide chip and the encapsulation material (epoxy resin). This reinforcing layer, through the synergistic effect of its high energy storage modulus (2.5 GPa) and low coefficient of thermal expansion (CTE) (≤85 ppm / ℃), provides multi-layered protection including high temperature resistance, water resistance, high insulation, high bonding strength, and thermal stress buffering. This significantly optimizes the thermal management, mechanical stress, and electrical performance of the silicon carbide power module, increasing the module's expected lifespan by more than three times and achieving a power cycle life of over 100,000 cycles.

[0049] The above are merely preferred embodiments of the present utility model and are not intended to limit the implementation methods and protection scope of the present utility model. Those skilled in the art should realize that any equivalent substitutions and obvious changes made using the content of this specification and illustrations should be included within the protection scope of the present utility model.

Claims

1. A chip interface coupling agent sprayed onto an injection-molded power module, comprising a ceramic substrate, a chip, a diode, a lead frame, and a plastic encapsulation shell, wherein the chip, the diode, and the lead frame are disposed on the ceramic substrate, and the ceramic substrate, the chip, the diode, and the lead frame are encapsulated within the plastic encapsulation shell, characterized in that, Also includes: A chip interface coupling agent reinforcement layer is sprayed and cured onto the surfaces of the ceramic substrate, the chip, the diode, and the lead frame, respectively, and the chip interface coupling agent reinforcement layer is encapsulated within the plastic encapsulation shell.

2. The injection molding power module with sprayed chip interface coupling agent according to claim 1, characterized in that, The chip interface coupling agent reinforcement layer uses a chip interface coupling agent material, which is in the form of a solution mixture and is sprayed onto the surface of the ceramic substrate, the chip, the diode, the bonding point, and the solder joint of the lead frame.

3. The injection molding power module with sprayed chip interface coupling agent according to claim 1, characterized in that, The thickness of the chip interface coupling agent reinforcement layer is 10μm to 50μm.

4. The injection molding power module with sprayed chip interface coupling agent according to claim 1, characterized in that, The power electrode on the front side of the chip is connected to the back side of the chip copper foil, the front side of the diode is connected to the back side of the diode copper foil, and the front side of the chip copper foil is connected to the front side of the diode copper foil and the circuit area of ​​the ceramic substrate.

5. The injection molding power module with sprayed chip interface coupling agent according to claim 4, characterized in that, The diode is connected to the diode copper foil and to the ceramic substrate using a silver paste sintering process.

6. The injection molding power module with sprayed chip interface coupling agent according to claim 4, characterized in that, The power electrode on the front side of the chip is connected to the back side of the copper foil on the chip, and the back side of the chip is connected to the circuit area on the front side of the ceramic substrate using a silver paste sintering process.

7. The injection-molded power module with sprayed chip interface coupling agent according to claim 5 or 6, characterized in that, The sintering temperature in the silver paste sintering process is 200℃-300℃, and the sintering pressure is 20Mpa-70Mpa.

8. The injection molding power module with sprayed chip interface coupling agent according to claim 4, characterized in that, The power electrode of the chip is connected to the copper foil of the chip, and the power electrode of the chip is connected to the copper foil of the diode via copper wire bonding.

9. The injection molding power module with sprayed chip interface coupling agent according to claim 1, characterized in that, The ceramic substrate is a silicon nitride ceramic substrate prepared by active metal brazing process.

10. The injection molding power module with sprayed chip interface coupling agent according to claim 1, characterized in that, The encapsulated shell is made of epoxy resin.

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