A polymer coating for reliable electric field hierarchical management of a 10kV SiC power module at 200℃ and its preparation method.

Abstract

The application relates to the technical field of power semiconductor packaging, in particular to a polymer coating for 10kV SIC power module reliable electric field grading management under 200 DEG C and a preparation method thereof. The preparation method is as follows: dichloro-3,4,3',4'-tetraformic dianhydride and 4,4'-diamino-3,3'-dimethyl diphenyl are dissolved in chloroform to form a precursor solution, and then the precursor solution is heated and polymerized to obtain a polymer solution; the polymer solution is coated to form a polymer coating. The polymer coating is coated on a functional module, a coating is formed at a triple point and a chip periphery, a grading insulation structure is constructed to reduce the field intensity in high-voltage module organic silicon gel, improve a partial discharge inception voltage (PDIV), and meet 10kV / 200 DEG C long-term reliable operation.

Description

Technical Field

[0001] This invention relates to the field of power semiconductor packaging technology, specifically to a polymer coating for reliable electric field hierarchical management of a 10kV SiC power module at 200℃ and its preparation method. Background Technology

[0002] High-voltage SiC power devices are widely used in power grids and other fields. However, under high-voltage and high-temperature conditions, severe electric field concentration occurs at the three-phase point inside the power module and around the chip, which can easily lead to partial discharge and insulation failure. Although the use of silicone gel that can operate at 200℃ has been proposed, the dielectric properties of silicone gel deteriorate significantly at 200℃, which cannot meet the high-voltage insulation requirements.

[0003] While existing nonlinear dielectric constant coatings can effectively improve the partial discharge initiation voltage of DBCs and alleviate the electric field, they suffer from drawbacks such as failure due to high-temperature nonlinear effects and inapplicability to areas surrounding the chip. Therefore, if a material with high dielectric strength and no dielectric degradation at 200°C could be developed, and this material could be coated onto the chip periphery and triple point to form a coating of a certain thickness, followed by encapsulation with high-temperature resistant silicone gel, it would help high-voltage modules operate stably at 200°C. Summary of the Invention

[0004] To address the problems in the prior art, this invention provides a polymer coating for reliable electric field hierarchical management of a 10kV SiC power module at 200℃.

[0005] This invention is achieved through the following technical solution: A method for preparing a polymer coating for reliable electric field hierarchical management of a 10kV SiC power module at 200℃ involves dissolving dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride and 4,4'-diamino-3,3'-dimethylbiphenyl in chloroform to form a precursor solution, followed by heating and polymerization to obtain a polymer solution; the polymer solution is then coated to form a polymer coating.

[0006] Preferably, the molar ratio of dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride to 4,4'-diamino-3,3'-dimethylbiphenyl is 1:1.

[0007] Preferably, the molar ratio of chloroform, dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride and 4,4'-diamino-3,3'-dimethylbiphenyl is 80:1:1, and the mass fraction is 20%.

[0008] Preferably, the viscosity of the polymer solution is 500±5.

[0009] Preferably, the heating polymerization includes two stages. In the first stage, the temperature is first heated to 80°C for 200 min, and then the temperature is increased to 300°C at a rate of 60 min.

[0010] The polymer coating prepared by the method described above for reliable electric field hierarchical management of a 10kV SiC power module at 200℃ has a dielectric constant of 3.65 at 25℃ and 1kHz, and 3.52 at 100kHz when the thickness of the polymer coating is 10μm; it also has a dielectric constant of 3.65 at 200℃ and 1kHz, and 3.70 at 100kHz.

[0011] Preferably, when the thickness of the polymer coating is 10 μm, the breakdown strength is 578.6 kV / mm at 25°C and the dielectric strength is 565.3 kV / mm at 200°C.

[0012] Preferably, the polymer coating has a glass transition temperature of 299.1°C and a 5% thermal weight loss temperature of 487°C.

[0013] A 10kV SiC MOSFET power module, wherein the DBC substrate of the power module is coated with the polymer coating having a thickness of 40~50μm.

[0014] Preferably, the polymer coating is applied to the triple point and the area surrounding the chip on the DBC substrate, and also covers the junction between the copper layer and the ceramic layer.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a polymer coating for reliable electric field hierarchical management of a 10kV SiC power module at 200℃. The coating is made by dissolving two monomers, dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride and 4,4'-diamino-3,3'-dimethylbiphenyl, in chloroform solvent in a specific ratio, stirring until homogeneous to form a precursor solution, and then heating and polymerizing to obtain a polymer solution. Coating this polymer solution at the triple point and around the chip creates a hierarchical insulation structure that reduces the electric field strength within the high-voltage module's silicone gel and increases the partial discharge initiation voltage (PDIV), ensuring long-term reliable operation at 10kV / 200℃. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the preparation process of a polymer coating for reliable electric field hierarchical management of a 10kV SiC power module at 200℃, according to the present invention. Figure 2 This is a metallographic cross-sectional view of the polymer coating obtained in this invention; Figure 3 This is a process flow diagram of the fabrication of a 10kV SiC power module according to the present invention; Figure 4 Electric field distribution at the interface between the chip terminal and the silicon gel; Figure 5 The electric field distribution at the interface between the triple point and the silica gel; Figure 6 For comparison of partial discharge initiation voltage (PDIV). Detailed Implementation

[0017] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0018] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0019] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0020] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0021] This invention discloses a method for preparing a polymer coating for reliable electric field hierarchical management of a 10kV SiC power module at 200℃, referring to... Figure 1 Dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride and 4,4'-diamino-3,3'-dimethylbiphenyl were dissolved in a 20% (w / w) solution at a molar ratio of 1:1. Chloroform A precursor solution is formed, which is then heated and polymerized to obtain a polymer solution with a viscosity of 500±5. The polymer solution is then coated to form a polymer coating (such as...). Figure 2 The molar ratio of chloroform, dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride, and 4,4'-diamino-3,3'-dimethylbiphenyl is 80:1:1, and the mass fraction is 20%.

[0022] The heating polymerization consists of two stages. In the first stage, the temperature is first heated to 80°C for 200 min, and then gradually increased to 300°C for 60 min.

[0023] The present invention also discloses a polymer coating prepared by a method for reliable electric field hierarchical management of a 10kV SiC power module at 200℃. When the thickness of the polymer coating is 10μm, its dielectric constant is 3.65 at 25℃ and 1kHz, and 3.52 at 100kHz; at 200℃ and 1kHz, it is 3.65, and at 100kHz, it is 3.70.

[0024] When the thickness of the polymer coating is 10 μm, the breakdown strength is 578.6 kV / mm at 25℃ and the dielectric strength is 565.3 kV / mm at 200℃.

[0025] The polymer coating has a glass transition temperature of 299.1℃ and a 5% thermal weight loss temperature of 487℃.

[0026] This invention also discloses a 10kV SiC MOSFET power module. The DBC substrate of this power module is coated with a polymer coating of 40-50 μm thickness. Specifically, the polymer coating is applied to the three-phase point and the area surrounding the chip on the DBC substrate, and covers the interface between the copper and ceramic layers. Specifically: Dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride and 4,4'-diamino-3,3'-dimethylbiphenyl were dissolved in chloroform in a specific ratio to form a precursor solution. This precursor solution was then polymerized by heating to obtain a polymer solution. Subsequently, the polymer solution was coated using a casting process. The DBC substrate to be coated was placed flat, and the precursor solution was slowly added dropwise. The solution was allowed to stand, allowing it to form a continuous and uniform thin film under the influence of gravity and surface tension. During coating, the viscosity of the polymer solution was controlled at 500 mmol / L, and 5 ml of this solution was uniformly coated onto the DBC substrate to control the final coating thickness to be stable at 40-50 μm. The coated DBC substrate was then heated for polymerization and curing to form a dense, uniform, and high-temperature resistant polymer insulating coating. This coating simultaneously covers the three key areas of the DBC substrate, the chip periphery, and the interface between the copper and ceramic layers.

[0027] In addition, the power module includes a DBC substrate, a SiC MOSFET chip, bonding wires, terminals, and high-temperature resistant silicone gel. The upper and lower copper layers of the DBC substrate are both 0.3 mm thick, the middle alumina ceramic layer is 1 mm thick, and the terminal spacing is 2 mm. The entire power module is encapsulated with high-temperature resistant silicone gel to form a graded electric field insulation structure.

[0028] The module is assembled by bonding a polymer-coated DBC substrate to a 10kV SiC MOSFET chip using traditional processes such as soldering and wire bonding. Figure 3 As shown.

[0029] The above power modules were tested: Reference Figure 4 , 5 Through electric field simulation verification, the electric field at the three-phase point was reduced by 60.8%, and the electric field around the chip was reduced by 47.9%, effectively suppressing partial discharge. Subsequent partial discharge tests also proved this.

[0030] Partial discharge tests have shown (e.g.) Figure 6 Compared to uncoated DBC, coated DBC showed an average PDIV increase of 87.3% at 200℃, demonstrating the effectiveness, process compatibility, and long-term reliability of the coating. This provides a stable and efficient solution for the insulating packaging of high-temperature and high-pressure SiC power modules.

[0031] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A method for preparing a polymer coating for reliable electric field hierarchical management of a 10kV SiC power module at 200℃, characterized in that, Dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride and 4,4'-diamino-3,3'-dimethylbiphenyl are dissolved in chloroform to form a precursor solution, which is then heated and polymerized to obtain a polymer solution; the polymer solution is then coated to form a polymer coating.

2. The polymer coating for reliable electric field hierarchical management of a 10kV SiC power module at 200℃ according to claim 1, characterized in that, The molar ratio of dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride to 4,4'-diamino-3,3'-dimethylbiphenyl is 1:

1.

3. The polymer coating for reliable electric field hierarchical management of a 10kV SiC power module at 200℃ according to claim 1, characterized in that, The molar ratio of chloroform, dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride and 4,4'-diamino-3,3'-dimethylbiphenyl is 80:1:1, and the mass fraction is 20%.

4. The polymer coating for reliable electric field hierarchical management of a 10kV SiC power module at 200℃ according to claim 1, characterized in that, The viscosity of the polymer solution is 500±5.

5. The polymer coating for reliable electric field hierarchical management of a 10kV SiC power module at 200℃ according to claim 1, characterized in that, The heating polymerization consists of two stages. In the first stage, the temperature is first heated to 80°C for 200 min, and then gradually increased to 300°C for 60 min.

6. A polymer coating obtained by the polymer coating preparation method for reliable electric field hierarchical management of a 10kV SiC power module at 200℃ as described in any one of claims 1 to 5, characterized in that, When the thickness of the polymer coating is 10 μm, its dielectric constant is 3.65 at 25℃ and 1 kHz, and 3.52 at 100 kHz; at 200℃ and 1 kHz, it is 3.65, and 3.70 at 100 kHz.

7. The polymer coating according to claim 6, characterized in that, When the thickness of the polymer coating is 10 μm, the breakdown strength is 578.6 kV / mm at 25℃ and the dielectric strength is 565.3 kV / mm at 200℃.

8. The polymer coating according to claim 6, characterized in that, The polymer coating has a glass transition temperature of 299.1℃ and a 5% thermogravimetric temperature of 487℃.

9. A 10kV SiC MOSFET power module, characterized in that, The power module's DBC substrate is coated with a polymer coating of 40-50 μm thickness as described in any one of claims 5-7.

10. The 10kV SiC MOSFET power module according to claim 9, characterized in that, The polymer coating is applied to the three-phase point and the area surrounding the chip on the DBC substrate, and also covers the junction between the copper layer and the ceramic layer.

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