Micro-channel integrated axial flux motor stator and preparation method thereof

Abstract

The application belongs to the technical field of electric machines, and particularly discloses a micro-channel integrated axial flux motor stator and a preparation method thereof, wherein a metal layer of a metallized ceramic substrate is subjected to exposure, development and etching to form a continuous spiral winding, and a through hole is reserved at an interlayer connection point through laser cutting, interlayer interconnection pretreatment is performed, the metallized ceramic substrate after etching is divided into single-layer stator modules through laser cutting, the through hole is filled with nano silver paste, active metal solder paste is screen printed on the surface of the metal layer and the micro-channel, and the substrate layers are stacked in the order of "upper substrate layer-micro-channel layer-lower substrate layer", the interlayer through hole connection positions are aligned, a pre-tightening force is applied in a vacuum sintering furnace, and sintering integration is performed in the vacuum sintering furnace, and through the collaborative design of the metallized ceramic substrate and the micro-channel cooling, the heat dissipation efficiency of the high current density winding, the insulation reliability and the compactness of the structure are simultaneously solved.

Description

Technical Field

[0001] This invention belongs to the field of motor technology, specifically relating to a microchannel integrated axial flux motor stator and its fabrication method. Background Technology

[0002] The stator assembly of an axial flux motor typically uses a traditional printed circuit board (PCB) substrate as the winding support and electrical insulation structure. In existing technologies, the circuit layer of the PCB substrate is formed through a copper etching process, and the insulating substrate is mostly epoxy resin or polyimide. However, in high power density applications, this design has the following significant drawbacks:

[0003] Insufficient thermal conductivity: The thermal conductivity of the insulating material of the PCB substrate is low (0.3-0.4W / m·K), making it difficult for heat to be quickly dissipated from the windings, resulting in a significant increase in stator temperature and limiting the continuous power output of the motor;

[0004] Temperature resistance and reliability are limited: the long-term operating temperature of epoxy resin substrates is usually below 150°C. Under high temperature environment, thermal expansion delamination or copper foil peeling is likely to occur, which reduces insulation performance and mechanical stability.

[0005] Current carrying capacity limitation: Due to the thickness of the copper foil (generally ≤200μm) and the interlayer bonding process, local hot spots and energy loss are easily generated under high current conditions;

[0006] Therefore, there is an urgent need for a solution that combines high thermal conductivity, high temperature resistance, and reliable electrical insulation with heat dissipation to achieve synergistic optimization of heat dissipation and electrical performance of axial flux motors. Summary of the Invention

[0007] To achieve the above objectives, the present invention proposes a microchannel integrated axial flux motor stator, comprising an upper substrate layer, a microchannel layer, and a lower substrate layer. The upper and lower end faces of the microchannel layer are respectively fixed to the upper substrate layer and the lower substrate layer. Both the upper substrate layer and the lower substrate layer are composed of multiple processed metallized ceramic substrates. The metallized ceramic substrate includes a substrate and a metal layer, with the metal layer covering one side of the substrate. The microchannel layer includes microchannels.

[0008] A method for fabricating a microchannel integrated axial flux motor stator includes the following steps:

[0009] S1, Stator coil patterning: Expose, develop and etch the metal layer of the metallized ceramic substrate to form a continuous spiral winding, and pre-leave through holes at the interlayer connection points by laser cutting;

[0010] S2, Interlayer interconnection pretreatment: The metallized ceramic substrate that has completed step S1 is divided into single-layer stator modules by laser cutting, and the reserved through holes in S1 are filled with nano silver paste or copper paste.

[0011] S3, Microchannel-substrate interface solder layer construction: active metal solder paste is screen-printed on the surface of the metal layer and microchannel;

[0012] S4, Stacking and bonding: Stack the layers in the order of "upper substrate layer - microchannel layer - lower substrate layer", align the pre-reserved through-hole connection positions between the layers, and then apply pre-tightening force in the vacuum sintering furnace to ensure tight contact at the interface;

[0013] S5, Vacuum sintering: Sintering is carried out in a vacuum sintering furnace to form an integrated structure.

[0014] Preferably, the material of the single-sided metallized ceramic substrate in S1 is silicon nitride or alumina ceramic, and the material of the metal layer is copper, so as to provide excellent thermal conductivity and reliable electrical insulation performance, with a thickness of 0.1 to 1.2 mm;

[0015] Preferably, the continuous spiral winding in S1 is formed by first attaching a photosensitive film to the surface of the metal layer, then exposing and developing it using an exposure machine to form a spiral winding pattern. Then, the copper layer in the non-conductive area is removed by a wet etching process, finally forming a continuous spiral winding with a line width of 145-150μm and a spacing of 50μm-1000μm. The diameter of the reserved through hole is 0.2-0.5mm. The reserved through hole facilitates the subsequent filling of conductive material and ensures the electrical connection between layers.

[0016] Preferably, each single-layer stator module has a diameter of 50mm to match the motor magnetic pole structure. The solid content of the nano-silver paste or copper paste filling the reserved through holes is >85% and the filling density is >95%, which can avoid voids after sintering, improve conductivity and mechanical reliability. Pre-firing the single-layer stator module in a sintering furnace at 300°C for 60 minutes can remove solvent and enhance sintering stability.

[0017] Preferably, the composition of the metal solder paste in S3 is an Ag-Cu-Ti alloy, and the thickness of the metal solder paste is controlled at 30-50 μm, which can optimize wettability and ensure good interfacial bonding quality.

[0018] Preferably, after the assembly of the "upper substrate layer-microchannel layer-lower substrate layer" in S4 is completed, the assembly is fixed with a fixture to prevent relative slippage during the assembly process. The fixture applies a pre-tightening pressure of 5 to 10 MPa to the assembly, which can improve the interface contact quality, reduce porosity, and improve the overall structural stability.

[0019] Preferably, the vacuum sintering conditions in S5 are: vacuum degree: 10-3 to 10-2 Pa, heating rate: 5℃ / min, holding temperature: 800 to 950℃, and holding time: 4 to 10h.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. A multilayer axial flux stator is fabricated using a metallized substrate. Through the composite structure of high thermal conductivity ceramic and copper layer, the physical limitation of low thermal conductivity of traditional PCB substrates is overcome.

[0022] 2. A symmetrical sandwich structure of "upper substrate - microchannel - lower substrate" is adopted, and the overall warpage is ≤0.1mm by high-temperature co-firing bonding of the channel module and the substrate.

[0023] 3. The interface between modules is directly bonded through vacuum sintering, eliminating the need for traditional silicone grease / thermal pads and reducing interface thermal resistance.

[0024] 4. The microchannel integrated axial flux motor stator based on a metallized ceramic substrate prepared by the technical solution of the present invention significantly improves heat dissipation capacity, insulation reliability and current carrying capacity compared with the axial flux motor stator prepared by the traditional PCB substrate structure. It provides a better heat dissipation solution for high power density axial flux motors and has great engineering application value. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0026] Figure 2 This is a schematic diagram of the "upper substrate layer - microchannel layer - lower substrate layer" component structure of the present invention;

[0027] Figure 3 This is a schematic diagram of the microchannel structure of the present invention;

[0028] Figure 4 This is a schematic diagram of the structure of the single-layer stator module of the present invention.

[0029] 1. Metallized ceramic substrate; 2. Metal layer; 3. Continuous spiral winding; 4. Pre-reserved through-hole; 5. Microchannel; 6. Upper substrate layer; 7. Microchannel layer; 8. Lower substrate layer; 9. Substrate. Detailed Implementation

[0030] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the invention is not limited to the specific embodiments disclosed below.

[0032] The present invention will now be further described with reference to the accompanying drawings.

[0033] Example 1

[0034] A microchannel integrated axial flux motor stator is characterized by comprising an upper substrate layer 6, a microchannel layer 7, and a lower substrate layer 8. The upper and lower end faces of the microchannel layer 7 are respectively fixed to the upper substrate layer 6 and the lower substrate layer 8. The upper substrate layer 6 and the lower substrate layer 8 are each composed of multiple processed metallized ceramic substrates 1. The metallized ceramic substrate 1 includes a substrate 9 and a metal layer 2, with the metal layer 2 covering one side of the substrate 1. The microchannel layer 7 includes microchannels 5.

[0035] Example 2

[0036] A microchannel integrated axial flux motor stator and its fabrication method, comprising the following steps:

[0037] S1, Stator coil patterning: Expose, develop and etch the metal layer 2 of the metallized ceramic substrate 1 to form a continuous spiral winding 3, and pre-leave through holes 4 at the interlayer connection points by laser cutting.

[0038] S2, Interlayer interconnection pretreatment: The metallized ceramic substrate 1 that has completed step S1 is divided into single-layer stator modules by laser cutting, and nano silver paste is filled into the reserved through holes 4 in S1.

[0039] S3, Microchannel-substrate interface solder layer construction: active metal solder paste is screen-printed on the surface of metal layer 2 and microchannel 5.

[0040] S4, Stacking and bonding: Stack the layers in the order of "upper substrate layer 6 - microchannel layer 7 - lower substrate layer 8", align the connection positions of the pre-reserved through holes 4 between layers, and then apply pre-tightening force in the vacuum sintering furnace to ensure tight contact at the interface.

[0041] S5, Vacuum sintering: Sintering is carried out in a vacuum sintering furnace to form an integrated structure.

[0042] The metallized ceramic substrate 1 in S1 is made of silicon nitride ceramic. Silicon nitride ceramic has excellent thermal conductivity, high bending strength and low dielectric loss, which can meet the stringent requirements of thermal management, mechanical stability and electromagnetic efficiency of motors during continuous full-load operation. The metal layer 2 is made of copper and has a thickness of 0.4 mm.

[0043] The continuous spiral winding 3 in S1 is formed by first attaching a photosensitive film to the surface of the metal layer 2, and then exposing and developing it using an exposure machine to form a spiral winding pattern. Then, the copper layer in the non-conductive area is removed by a wet etching process, and finally a continuous spiral winding 3 with a line width of 150μm and a spacing of 300μm is formed. The diameter of the reserved through hole 4 is 0.4mm.

[0044] Each single-layer stator module has a diameter of 50 mm. The solid content of the nano-silver paste or copper paste filling the reserved through hole 4 is 90%, and the filling density is >95%. The single-layer stator module is pre-fired in a sintering furnace at 300°C for 60 min.

[0045] The composition of the metal solder paste in S3 is Ag-Cu-Ti alloy, and the thickness of the metal solder paste is controlled between 30 and 50 μm.

[0046] After the assembly of the “upper substrate layer 6-microchannel layer 7-lower substrate layer 8” in S4 is completed, the assembly is fixed with a clamp, and the clamp applies a preload pressure of 8MPa to the assembly.

[0047] The vacuum sintering conditions in S5 are: vacuum degree: 5×10-3 Pa, heating rate: 5℃ / min, holding temperature: 900℃, and holding time: 6h.

[0048] During sintering, the active metal solder paste undergoes diffusion bonding, forming an integral connection between the metal layer 12, the microchannel structure 5, and the pre-reserved through-holes 4, ensuring an interfacial bonding strength > 30 MPa and an interfacial thermal resistance below 0.2 K·cm. 2 / W.

[0049] Example 3

[0050] The difference between Example 3 and Example 2 is that the material of the metallized ceramic substrate 1 in this example is silicon nitride ceramic, as detailed below:

[0051] A microchannel integrated axial flux motor stator and its fabrication method, comprising the following steps;

[0052] S1, Stator coil patterning: Expose, develop and etch the metal layer 2 of the metallized ceramic substrate 1 to form a continuous spiral winding 3, and pre-leave through holes 4 at the interlayer connection points by laser cutting.

[0053] S2, Interlayer interconnection pretreatment: The metallized ceramic substrate 1 that has completed step S1 is divided into single-layer stator modules by laser cutting, and nano silver paste is filled into the reserved through holes 4 in S1.

[0054] S3, Microchannel-substrate interface solder layer construction: active metal solder paste is screen-printed on the surface of metal layer 2 and microchannel 5.

[0055] S4, Stacking and bonding: Stack the layers in the order of "upper substrate layer 6 - microchannel layer 7 - lower substrate layer 8", align the connection positions of the pre-reserved through holes 4 between layers, and then apply pre-tightening force in the vacuum sintering furnace to ensure tight contact at the interface.

[0056] S5, Vacuum sintering: Sintering is carried out in a vacuum sintering furnace to form an integrated structure.

[0057] The metallized ceramic substrate 1 in S1 is made of silicon nitride ceramic, and the metal layer 2 is made of copper with a thickness of 0.4 mm.

[0058] The continuous spiral winding 3 in S1 is formed by first attaching a photosensitive film to the surface of the metal layer 2, and then exposing and developing it using an exposure machine to form a spiral winding pattern. Then, the copper layer in the non-conductive area is removed by a wet etching process, and finally a continuous spiral winding 3 with a line width of 150μm and a spacing of 300μm is formed. The diameter of the reserved through hole 4 is 0.4mm.

[0059] Each single-layer stator module has a diameter of 50 mm. The solid content of the nano-silver paste or copper paste filling the reserved through hole 4 is 90%, and the filling density is >95%. The single-layer stator module is pre-fired in a sintering furnace at 300°C for 60 min.

[0060] The composition of the metal solder paste in S3 is Ag-Cu-Ti alloy, and the thickness of the metal solder paste is controlled between 30 and 50 μm.

[0061] After the assembly of the “upper substrate layer 6-microchannel layer 7-lower substrate layer 8” in S4 is completed, the assembly is fixed with a clamp, and the clamp applies a preload pressure of 8MPa to the assembly.

[0062] The vacuum sintering conditions in S5 are: vacuum degree: 5×10-3 Pa, heating rate: 5℃ / min, holding temperature: 900℃, and holding time: 6h.

[0063] During the sintering process, an oxide intermediate layer is formed between the metal layer and the alumina ceramic. This intermediate layer may contain recrystallization structures or microcracks. Although the contact surface is tight, incomplete diffusion during the sintering process may cause micropores or incomplete bonding, resulting in high interfacial thermal resistance. Furthermore, the thermal conductivity of the alumina ceramic sheet is relatively low, so the overall heat dissipation effect is generally poor.

[0064] Performance testing

[0065] The stator structures prepared in Examples 2 and 3 were tested under the same conditions, namely, liquid cooling at 2 L / min and an inlet temperature of 25°C, with a current of 10 A / mm. 2 After adjusting the current density, the stator structure prepared in Example 2 using silicon nitride ceramic as substrate material 9 has a stable surface temperature rise of less than 72°C and a winding DC resistance of 4.8mΩ, exhibiting excellent heat dissipation and current carrying capacity, making it suitable for high-load, continuous operation scenarios. In Example 3, the stator structure prepared using alumina ceramic as substrate material 9 has a stable surface temperature rise of 86°C and a winding DC resistance of 5.0mΩ, demonstrating good performance and being suitable for medium-to-high power density applications.

[0066] In contrast, the traditional air-cooled stator structure based on the PCB substrate in Comparative Example 1, under the same input power conditions, has a steady-state temperature rise of over 130°C and a winding resistance of 6.2mΩ. It exhibits obvious heat accumulation and local hot spots, limiting its heat dissipation capacity and failing to meet the requirements of continuous high-power operation for extended periods.

[0067] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A microchannel integrated axial flux motor stator, characterized in that, It includes an upper substrate layer (6), a microchannel layer (7), and a lower substrate layer (8). The upper and lower end faces of the microchannel layer (7) are fixed to the upper substrate layer (6) and the lower substrate layer (8), respectively. Both the upper substrate layer (6) and the lower substrate layer (8) are composed of multiple metallized ceramic substrates (1). The metallized ceramic substrate (1) includes a substrate (9) and a metal layer (2). The metal layer (2) covers one side of the substrate (9). The microchannel layer (7) includes microchannels (5). The method for fabricating a microchannel integrated axial flux motor stator includes the following steps: S1, Stator coil patterning: Expose-develop-etch the metal layer (2) of the metallized ceramic substrate (1) to form a continuous spiral winding (3), and reserve through holes (4) at the interlayer connection point by laser cutting; S2, Interlayer interconnection pretreatment: The metallized ceramic substrate (1) that has completed step S1 is divided into single-layer stator modules by laser cutting, and the reserved through holes (4) in S1 are filled with nano silver paste or copper paste. S3, Microchannel-substrate interface solder layer construction: active metal solder paste is screen printed on the surface of metal layer (2) and microchannel (5); S4, Stacking and bonding: Stack the layers in the order of "upper substrate layer (6) - microchannel layer (7) - lower substrate layer (8)", align the connection positions of the pre-reserved through holes (4) between layers, and then apply pre-tightening force in the vacuum sintering furnace to ensure tight contact of the interface; S5, Vacuum Sintering: Sintering and integral forming are carried out in a vacuum sintering furnace. The substrate (9) in S1 is made of silicon nitride ceramic or alumina ceramic, and the metal layer (2) is made of copper with a thickness of 0.1 to 1.2 mm. Each single-layer stator module has a diameter of 50 mm. The solid content of the nano-silver paste or copper paste filling the reserved through hole (4) is >85% and the filling density is >95%. The single-layer stator module is placed in a sintering furnace at 300°C for 60 min for pre-firing. The composition of the metal solder paste in S3 is Ag-Cu-Ti alloy, and the thickness of the metal solder paste is controlled at 30-50μm; After the assembly of the "upper substrate layer (6) - microchannel layer (7) - lower substrate layer (8)" in S4 is completed, the assembly is fixed with a clamp, and the clamp applies a pre-tightening pressure of 5 to 10 MPa to the assembly.

2. The method for fabricating a microchannel integrated axial flux motor stator according to claim 1, characterized in that, The continuous spiral winding (3) in S1 is formed by first attaching a photosensitive film to the surface of the metal layer (2), and then exposing and developing it using an exposure machine to form a spiral winding pattern. Then, the copper layer in the non-conductive area is removed by a wet etching process, and finally a continuous spiral winding (3) with a line width of 145-150μm and a spacing of 50μm-1000μm is formed. The diameter of the reserved through hole (4) is 0.2-0.5mm.

3. The method for fabricating a microchannel integrated axial flux motor stator according to claim 1, characterized in that, The vacuum sintering conditions in S5 are: vacuum degree: 10 -3 ~10 -2 Pa, heating rate: 5℃ / min, holding temperature: 800~950℃, holding time: 4~10h.

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