High-adhesiveness film sintered aluminum flat wire and preparation process thereof

Abstract

The invention discloses a high-adhesiveness film sintered aluminum flat wire and a preparation process thereof, a first coating contains plastic metal filler, a second coating contains high-modulus fibers, the high-modulus fibers in the second layer and the plastic metal filler in the first layer form a mechanical interlocking structure, and the metal filler and an aluminum matrix form physical metallurgical bonding. The fiber network in the second layer rapidly disperses local concentrated stress to a larger area by means of the high elastic modulus of the fiber network, and when the stress peak value which is not completely eliminated is transmitted to the first layer, the plastic metal filler can generate irreversible plastic deformation; the bonding strength between the thin film layers and between the thin film layers and the aluminum matrix is enhanced through a mechanical interlocking structure and physical metallurgical bonding, mechanical energy is converted into deformation work consumption, stress is prevented from being accumulated at an interface, and therefore the anti-fatigue and anti-impact performance of the coating is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of cable manufacturing technology, and more particularly to a high-adhesion thin-film sintered aluminum flat wire and its manufacturing process. Background Technology

[0002] Thin-film sintered aluminum flat wire is a high-performance electromagnetic wire formed by sequentially coating and high-temperature curing multiple layers of special resin films onto the surface of an aluminum flat conductor. Its core feature lies in utilizing the excellent electrical insulation, heat resistance, and mechanical strength of polymer films (such as polyester and polyimide) to construct an extremely thin yet robust insulating layer on the conductor surface. Compared to traditional enameled wire, this structure offers higher insulation levels, better thermal conductivity, and greater space utilization. Therefore, it is widely used in high-end electrical equipment such as drive motors for new energy vehicles, high-efficiency industrial motors, and transformers to meet their stringent requirements for miniaturization, high power density, and high reliability.

[0003] In existing technologies, the typical preparation process for thin-film sintered aluminum flat wire mainly includes surface cleaning of the aluminum conductor, electrostatic spraying or dip coating of the insulating coating, and subsequent curing in a high-temperature sintering furnace. Specifically, the process first degreases and chemically treats the aluminum flat wire to initially improve coating adhesion; then, a single-material or composite-material insulating coating is uniformly coated onto the conductor surface; finally, by controlling the temperature of the sintering furnace and the wire speed, the coating is melted, leveled, and cross-linked, ultimately forming a continuous insulating film on the conductor. Although this process is relatively mature, its coating structure is mostly a single material or a simple multi-layer superposition, and the design of process parameters often focuses on the overall uniformity and electrical performance of the coating, with insufficient consideration for the fine control of the interface microstructure and stress distribution.

[0004] However, the existing processes and products described above suffer from adhesion defects and reliability challenges due to deficiencies in interface design and stress management. The root causes of these problems can be attributed to two aspects: First, at the interface bonding level, existing technologies often fail to properly control the surface roughness of the aluminum substrate. Overly smooth surfaces limit the mechanical anchoring effect, while excessively rough surfaces easily lead to uneven coating coverage and air bubbles, both of which weaken the adhesion of the underlying layer and cause local electric field distortion. Second, at the structural stress level, the inherent rectangular cross-section of aluminum flat wire makes its four corners natural stress concentration points. Existing coating processes struggle to effectively compensate for these corners, causing the coating to easily crack and delaminate at these weak points under stresses such as bending and thermal cycling. These failure risks, caused by both weak interface bonding and stress concentration at corners, severely limit the service life and reliability of thin-film sintered aluminum flat wires under long-term dynamic operating conditions.

[0005] Therefore, improvements are needed to the existing thin-film sintered aluminum flat wire technology to address the aforementioned shortcomings. Summary of the Invention

[0006] This invention overcomes the shortcomings of the prior art and provides a high-adhesion thin-film sintered aluminum flat wire and its preparation process.

[0007] To achieve the above objectives, the technical solution adopted by this invention is as follows: a process for preparing high-adhesion thin-film sintered aluminum flat wire, comprising the following steps:

[0008] S1: The aluminum conductor itself is pretreated to obtain a pretreated substrate;

[0009] S2: Tin oxide powder is mixed with polyester resin to obtain a primary treatment solution. The primary treatment solution is coated onto the pretreated substrate in S1 and subjected to a first curing treatment to form a first coating.

[0010] S3: The first coating is etched to form microgrooves;

[0011] S4: Glass fiber is mixed with polyimide to obtain a secondary treatment liquid. The secondary treatment liquid is coated onto the first coating and subjected to a second curing treatment to form a second coating, thereby obtaining a high-adhesion thin-film sintered aluminum flat wire.

[0012] In a preferred embodiment of the present invention, the surface pretreatment in S1 includes a degreasing process and a surface roughening process; the degreasing process specifically involves using a silicate solution with a concentration of 5-10 wt% and a pH value of 10-12, controlling the temperature at 50-70°C, soaking or spraying for 3-10 minutes, and then cleaning thoroughly; the surface roughening process specifically involves using a 5-10 wt% phosphoric acid or nitric acid solution, treating at room temperature to 40°C for 30 seconds to 5 minutes, and then cleaning thoroughly.

[0013] In a preferred embodiment of the present invention, the tin oxide powder in S2 has a particle size of 1-5 μm and is added in an amount of 10-30 wt% of the solid content of the polyester resin, and the solid content of the polyester resin is 40-60%.

[0014] In a preferred embodiment of the present invention, the S2 mixing is carried out by stirring at a speed of 1000-3000 rpm for 30-60 min, the first curing treatment is carried out by preheating at 80-120℃ for 2-5 min, and then treating in a sintering furnace at 150-180℃ for 5-15 min.

[0015] In a preferred embodiment of the present invention, the etching process in S3 is plasma etching or laser micromachining. The plasma etching uses oxygen or argon gas, with a power of 200-500W and a processing time of 30s to 3min.

[0016] In a preferred embodiment of the present invention, the microgroove has a width of 5-20 μm, a depth of 6-10 μm, a center-to-center distance of 15-40 μm between adjacent microgrooves, and the direction of the microgroove is 30°-45° with the axial direction of the aluminum flat wire and the angle is consistent. The microgrooves are respectively disposed on the two narrow sides of the aluminum flat wire.

[0017] In a preferred embodiment of the present invention, the glass fiber in step S4 has a diameter of 5-15 μm and a length of 50-200 μm, the surface of the glass fiber is treated with a silane coupling agent, and the amount of glass fiber added is 5-20 wt% of the solid content of the polyimide resin.

[0018] In a preferred embodiment of the present invention, the polyimide resin solid content in S4 is 15-30 wt%, the mixing speed in S4 is 300-600 rpm, and the mixing time is 30-60 min.

[0019] In a preferred embodiment of the present invention, the second curing process is to treat at 80-120°C for 5-15 minutes, raise the temperature to 180-220°C at a rate of 1-3°C / min, hold for 10-20 minutes, raise the temperature to 280-320°C at a rate of 2-5°C / min, and hold for 20-40 minutes.

[0020] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a high-adhesion thin-film sintered aluminum flat wire: the thickness of the first coating is 30-60μm, and the thickness of the second coating is 40-80μm.

[0021] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0022] (1) The present invention provides a process for preparing high-adhesion thin-film sintered aluminum flat wire. The first coating contains plastic metal filler and the second coating contains high-modulus fiber. The high-modulus fiber in the second layer and the plastic metal filler in the first layer form a mechanical interlocking structure. The metal filler forms a physical metallurgical bond with the aluminum substrate. The fiber network in the second layer rapidly disperses the local concentrated stress to a larger area due to its high elastic modulus. When the stress peak that cannot be completely eliminated is transmitted to the first layer, the plastic metal filler will undergo irreversible plastic deformation. Compared with the thin-film sintered aluminum flat wire in the prior art, the mechanical interlocking structure and physical metallurgical bond enhance the bonding strength between thin film layers and between thin film layers and the aluminum substrate, and convert mechanical energy into deformation work for consumption, avoiding stress accumulation at the interface, thereby significantly improving the fatigue resistance and impact resistance of the coating.

[0023] (2) In this invention, microgrooves are pre-formed on the primary coating and the secondary coating contains chopped glass fibers. The microgrooves can accommodate more secondary coating materials. The hydrodynamic effect makes the fibers easier to be captured and retained by the microgrooves. The enriched fibers force the crack to change its path to consume more energy, thereby dissolving the macroscopic crack into a large number of tiny, harmless energy dissipation processes. Compared with the prior art, this invention changes the defect that the coating at the R-corner is prone to thinning and cracking. It selectively guides the glass fibers to be enriched in stress concentration areas such as the R-corner of the aluminum flat wire, thereby achieving targeted toughening.

[0024] (3) In this invention, the primary coating is doped with tin oxide alloy filler with high thermal conductivity, which improves the thermal conductivity of the primary coating itself. During the heating and cooling stages of sintering and operation, the tin oxide alloy particles form an efficient heat channel, making the temperature distribution of the aluminum substrate and the coating interface more uniform and reducing the thermal stress caused by excessive temperature difference. Compared with the prior art, the polyimide secondary coating itself has excellent thermal stability, and the glass fiber can suppress its thermal expansion, thereby ensuring the overall dimensional stability of the coating and reducing the damage of thermal cycling to the bonding interface. The high thermal conductivity of the metal filler combined with the dimensional stability of the fiber layer suppresses the generation of thermal stress from the source. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart illustrating the method steps of a preferred embodiment of the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Many 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. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0029] In the development of thin-film sintered aluminum flat wires for high-power-density motors, long-term reliability is severely constrained by two inherent technical bottlenecks: first, insufficient interfacial bonding strength between the conductor substrate and the insulating coating, making it prone to interface failure due to thermomechanical stress; second, the inherent angular effect of the flat wire geometry causes localized stress concentration, making the coating susceptible to crack initiation and delamination at the corners under bending or thermal cycling conditions. Existing technical solutions mostly focus on improving performance by optimizing individual coating materials or adjusting global process parameters; however, these methods fail to fundamentally solve the problem of synergistic management between interfacial bonding and bulk stress at the system level.

[0030] The inventors discovered that by constructing a functional gradient coating system of "metal composite bottom layer + fiber-reinforced top layer" and pre-setting microgrooves in the bottom layer, the fibers can be guided to accumulate in a directional manner in the stress concentration area. This allows the plastic deformation of the bottom metal and the bridging effect of the top fiber to form a cross-scale energy absorption and stress dispersion synergistic mechanism, thereby simultaneously improving the film adhesion and film toughness of the thin film sintered aluminum flat wire.

[0031] The bottom interface layer, through the introduction of ductile metal fillers and a pre-designed microgroove structure, achieves microscopic mechanical interlocking and macroscopic anchoring with the aluminum matrix, significantly improving the interfacial bonding strength. In the top structural layer, the fiber fillers selectively accumulate within the microgrooves and stress concentration areas at the edges under the influence of the flow field, forming a directional toughening network. Crucially, the combination of the plastic deformation capacity of the bottom metal and the elastic bridging effect of the top fibers solves the industry-wide problem of delamination caused by weak interfacial bonding and stress concentration at the edges.

[0032] like Figure 1 As shown, a process for preparing a high-adhesion thin-film sintered aluminum flat wire includes the following steps:

[0033] S1: The aluminum conductor itself is pretreated to obtain a pretreated substrate;

[0034] S2: Tin oxide powder is mixed with polyester resin to obtain a primary treatment solution. The primary treatment solution is coated onto the pretreated substrate in S1 and subjected to a first curing treatment to form a first coating.

[0035] S3: The first coating is etched to form microgrooves;

[0036] S4: Glass fiber is mixed with polyimide to obtain a secondary treatment liquid. The secondary treatment liquid is coated onto the first coating and subjected to a second curing treatment to form a second coating, thereby obtaining a high-adhesion thin-film sintered aluminum flat wire.

[0037] The first coating contains ductile metal filler, and the second coating contains high-modulus fibers. The high-modulus fibers in the second layer and the ductile metal filler in the first layer form a mechanically interlocked structure. The metal filler forms a physical-metallurgical bond with the aluminum substrate. The fiber network in the second layer, with its high elastic modulus, rapidly disperses localized concentrated stress to a larger area. When stress peaks that are not completely eliminated are transmitted to the first layer, the ductile metal filler undergoes irreversible plastic deformation. The mechanical interlocking structure and physical-metallurgical bond enhance the bonding strength between film layers and between film layers and the aluminum substrate, and convert mechanical energy into deformation work, thus avoiding stress accumulation at the interface and significantly improving the coating's fatigue and impact resistance.

[0038] Microgrooves are pre-formed on the primary coating, and the secondary coating contains chopped glass fibers. The microgrooves can accommodate more secondary coating material, and the hydrodynamic effect makes it easier for the fibers to be captured and retained by the microgrooves. The enriched fibers force the crack to change its path to consume more energy, thereby dissolving the macroscopic crack into a large number of tiny, harmless energy dissipation processes. This changes the defect of coating thinning and cracking at the R-corner, and selectively guides the glass fibers to enrich in stress concentration areas such as the R-corner of the aluminum flat wire, achieving targeted toughening.

[0039] The primary coating incorporates highly thermally conductive tin oxide alloy filler, enhancing its thermal conductivity. During the heating and cooling stages of sintering and operation, the tin oxide alloy particles form efficient heat channels, resulting in a more uniform temperature distribution at the aluminum substrate and coating interface. This reduces thermal stress caused by excessive temperature differences. The polyimide secondary coating itself possesses excellent thermal stability, while the glass fiber further inhibits its thermal expansion, thus ensuring the overall dimensional stability of the coating and reducing the damage to the bonding interface caused by thermal cycling. The combination of the high thermal conductivity of the metal filler and the dimensional stability of the fiber layer effectively suppresses the generation of thermal stress at its source.

[0040] In S1:

[0041] Surface pretreatment includes degreasing and surface roughening. The degreasing process involves using a silicate solution with a concentration of 5-10 wt% and a pH of 10-12, controlling the temperature at 50-70℃, soaking or spraying for 3-10 minutes, and then rinsing thoroughly. The surface roughening process involves using a 5-10 wt% phosphoric acid or nitric acid solution, treating at room temperature to 40℃ for 30 seconds to 5 minutes, and then rinsing thoroughly.

[0042] The aluminum conductor underwent a surface pretreatment that included degreasing and chemical roughening, resulting in a clean and active surface with a uniform microstructure. The degreasing treatment thoroughly removed surface contaminants and prevented the formation of a weak boundary layer. The subsequent controlled chemical etching formed a uniformly distributed micro-uneven structure on the aluminum substrate surface. This structure not only significantly increased the contact area between the coating and the substrate to enhance the mechanical interlocking effect, but also ensured uniform coverage of the subsequent coating due to its moderate roughness.

[0043] This process avoids areas of excessively thin coating or bubble formation caused by overly sharp contours, thus improving the reliability and consistency of interfacial bonding from the source. The pretreatment process, through the synergistic effect of step-by-step cleaning and etching, creates ideal interfacial conditions for a strong bond in subsequent coatings.

[0044] In S2:

[0045] The tin oxide powder has a particle size of 1-5μm and is added at 10-30wt% of the solid content of the polyester resin, which has a solid content of 40-60%.

[0046] Mixing involves stirring at 1000-3000 rpm for 30-60 minutes. The first curing treatment involves preheating at 80-120℃ for 2-5 minutes, followed by treatment in a sintering furnace at 150-180℃ for 5-15 minutes.

[0047] The tin oxide powder in the primary coating has a specific particle size and addition amount, and the polyester resin has a specific solid content, which ensures the dispersibility of the filler and the processability of the coating. The tin oxide filler with a specific particle size and content can form uniformly distributed reinforcing points in the polyester resin matrix. These filler particles not only optimize the flow behavior of the coating during the sintering process through rigid support, but also enable it to better replicate the surface morphology of the aluminum substrate and form microgrooves.

[0048] These high surface energy metallic filler particles significantly increase the contact tightness and thermodynamic stability between the coating and the aluminum substrate, thereby generating strong mechanical interlocking and physical adsorption in the interface region, providing a solid and highly reactive substrate for subsequent secondary coatings. The synergistic design of these material parameters enables the primary coating to form a transition layer with both ideal microstructure and interfacial activity after curing.

[0049] The mixing of the primary treatment solution employs a specific rotation speed and time. The first curing process utilizes a stepped temperature increase program, achieving uniform dispersion of the filler and forming a partially cured coating. Thorough mixing at high speeds ensures the uniform distribution of tin oxide filler in the resin, avoiding localized stress concentration or interface defects caused by filler agglomeration. The stepped curing process promotes solvent evaporation and coating leveling through a preheating stage, followed by sintering at a specific temperature and time to achieve a partially cross-linked resin state. This state allows the coating to possess sufficient strength to maintain the shape stability of the microgroove structure while retaining sufficient molecular chain activity to form chemical bonds with the upper layer during secondary coating. This optimizes the interface transition layer and enhances the overall coating system's cohesion. The synergistic effect of this mixing and curing process lays the foundation for the precise preparation of subsequent microgrooves and the stability of the final interface structure.

[0050] In S3:

[0051] The etching process is either plasma etching or laser micromachining. Plasma etching uses oxygen or argon gas, with a power of 200-500W and a processing time of 30 seconds to 3 minutes.

[0052] The microgrooves are 5-20μm wide and 6-10μm deep, with a center-to-center distance of 15-40μm between adjacent microgrooves. The direction of the microgrooves is 30°-45° to the axial direction of the aluminum flat wire and the angle is consistent. The microgrooves are respectively set on the two narrow sides of the aluminum flat wire.

[0053] Plasma with specific parameters is used to etch the surface of the primary coating, forming a precise microgroove structure on the coating surface. Plasma with specific power and gas environment can uniformly etch away the surface resin in an isotropic manner, while retaining the uniformly distributed tin oxide filler inside, thereby forming a microgroove array with controllable size and clear outline on the interface layer surface.

[0054] These microstructures not only significantly increase the effective contact area of ​​the secondary coating, but the glass fibers in the secondary coating also provide directional anchoring sites, allowing the fibers to mechanically interlock within the grooves. This creates a locally reinforced composite structure in the stress-concentrated, flat-line angular regions, effectively suppressing crack initiation and propagation. This etching process achieves precise control over the morphology of the interface transition layer through the controllable interaction between the energy beam and the material surface.

[0055] The two narrow sides of the aluminum flat wire are provided with an array of microgrooves with specific geometric parameters and orientation angles, which increases the contact area of ​​the secondary coating. The long axis of the microgrooves is set at an acute angle to the axis of the aluminum flat wire, so that when the flat wire is bent, the shear stress acting on the coating is effectively decomposed into components parallel to and perpendicular to the groove direction, which significantly reduces the stress component along the interface direction that is most likely to cause delamination failure.

[0056] By precisely positioning the grooves on the two narrow sides where stress concentration is most severe, the fibers in the secondary coating can be oriented and anchored in these critical areas. This, in addition to mechanical interlocking, further suppresses peel stress by changing the stress transmission path, greatly improving the coating's durability under dynamic bending conditions.

[0057] In S4:

[0058] The glass fiber has a diameter of 5-15μm and a length of 50-200μm. The surface of the glass fiber is treated with a silane coupling agent, and the amount of glass fiber added is 5-20wt% of the solid content of the polyimide resin.

[0059] The solid content of the polyimide resin is 15-30wt%, the mixing speed in S4 is 300-600rpm, and the mixing time is 30-60min.

[0060] The second curing process involves treating at 80-120℃ for 5-15 minutes, then heating at a rate of 1-3℃ / min to 180-220℃ and holding for 10-20 minutes, followed by heating at a rate of 2-5℃ / min to 280-320℃ and holding for 20-40 minutes.

[0061] The secondary coating uses glass fibers with specific dimensions and amounts treated with silane coupling agents. Its initial effect is to enhance the mechanical strength of the secondary coating itself. The fibers with specific aspect ratios are easy to orient and anchor in the microgrooves under the action of the flow field. The fiber surface treated with silane coupling agents can form a strong chemical bond with the polyimide resin, so that stress can be efficiently transferred from the less tough resin matrix to the high-strength fibers, thereby inhibiting the propagation of microcracks through the bridging effect of the fibers.

[0062] A uniformly dispersed fiber network can alter the distribution of the stress field, dispersing locally concentrated stress over a larger area, thereby significantly improving the coating's resistance to cracking in stress concentration areas such as flat lines and corners. This fiber parameter design, combined with the surface treatment process, achieves efficient stress transfer between the fibers and the resin matrix, and creates a cross-scale synergistic reinforcement effect with the microgroove structure of the primary coating.

[0063] The secondary treatment solution uses polyimide resin with a specific solid content and optimized mixing process parameters; its initial effect is to obtain a fiber-reinforced slurry with suitable viscosity and uniformity. The specific solid content and continuous mixing at medium and high speed give the resin system suitable rheological properties, which can not only fully impregnate and disperse the glass fibers treated with coupling agent to form a stable slurry, but also ensure that it can fill and anchor well in the micro-grooves of the primary coating during coating.

[0064] Uniformly dispersed fibers form a strong interfacial bond with the polyimide matrix through a coupling agent, while optimized viscosity prevents bubble entrainment and fiber sedimentation. This ultimately results in a dense, three-dimensional reinforcing network within the secondary coating, tightly integrated with the microstructure of the primary coating, significantly improving the overall structural integrity and anti-delamination capability of the insulation layer. The synergistic effect of this material system and mixing parameters ensures ideal fiber dispersion in the resin and effective integration with the interfacial structure of the primary coating.

[0065] The secondary coating curing process employs a programmed step-by-step heating process, which achieves full curing and imidization of the resin. The low-temperature stage promotes the full evaporation of the solvent and achieves preliminary interfacial fusion between the coatings. The medium-temperature stage allows the primary coating to fully crosslink and form chemical bonds with the secondary coating through slow heating, while also allowing the stress to be initially relaxed. The subsequent high-temperature imidization process is carried out under strictly controlled thermal history, which allows the polyimide molecular chains to rearrange in an orderly manner and complete cyclization.

[0066] The difference in thermal expansion between the fiber and the resin matrix is ​​gradually released, allowing the molecular chain segments at the interface to fully relax, ultimately forming a dense and stable coating system with significantly reduced internal stress. This fundamentally avoids coating warping or interface delamination caused by the accumulation of thermal stress. This multi-stage heat treatment process achieves effective release of internal stress and optimized integration of the interface structure by precisely controlling molecular chain movement and cross-linking reaction kinetics.

[0067] A high-adhesion thin-film sintered aluminum flat wire: the first coating thickness is 30-60μm, and the second coating thickness is 40-80μm.

[0068] By controlling the thickness of the first and second coatings within a specific range, the thickness of the first coating of 30-60 μm ensures that the tin oxide filler forms an effective conductive network to optimize the interface bonding, and also provides sufficient material depth for the processing of the microgroove structure without damaging the underlying interface. Meanwhile, the thickness of the second coating of 40-80 μm provides the necessary spatial dimension for the uniform distribution and directional arrangement of glass fibers, enabling them to be fully embedded in the microgrooves of the first coating and to construct a complete three-dimensional reinforcing skeleton.

[0069] This thickness combination allows for a spatially rational distribution of the stress buffer layer and the structural reinforcement layer. It avoids localized insulation failure caused by an excessively thin single layer, while also preventing increased internal stress and decreased flexibility due to excessive total thickness. This achieves an optimal balance between adhesion and resistance to bending fatigue while ensuring insulation strength. It ensures that the total thickness of the insulation layer meets electrical performance requirements, and this thickness configuration, along with the dual-layer functional design, creates a spatially synergistic optimization.

[0070] The specific types and sources of the materials used in Examples 1-9 and Comparative Example 1 are shown below:

[0071] Tin oxide powder, specifically YT-OSn-02, is from Yunnan Tin Industry Co., Ltd.; polyester resin, specifically TS-1850, is from Zhejiang Tiansong New Material Co., Ltd.; glass fiber, specifically ECS-303A-3, is from China Jushi Co., Ltd.; polyimide resin, specifically PI-2600, is from Shanghai Enjie New Material Technology Co., Ltd.; silane coupling agent, specifically KH-550, is from Nanjing Xiangyi New Material Co., Ltd.

[0072] Example 1:

[0073] This embodiment provides a process for preparing high-adhesion thin-film sintered aluminum flat wire, including the following steps:

[0074] S1: The aluminum conductor itself undergoes surface pretreatment, which includes degreasing and surface roughening. The degreasing process involves using an 8wt% silicate solution with a pH of 10, controlling the temperature at 60℃, immersing for 3-10 minutes, and then cleaning thoroughly. The surface roughening process involves using a 6wt% phosphoric acid solution, treating at room temperature for 3 minutes, and then cleaning thoroughly to obtain the pretreated substrate.

[0075] S2: Tin oxide powder is mixed with polyester resin to obtain a primary treatment solution. The primary treatment solution is coated onto the pretreated substrate in S1 and subjected to a first curing treatment to form a first coating.

[0076] The tin oxide powder has a particle size of 3μm and is added at 20wt% of the solid content of the polyester resin, which has a solid content of 50%.

[0077] S2 mixing involves stirring at 2500 rpm for 45 minutes, followed by a first curing process of preheating at 110°C for 3 minutes and then sintering in a furnace at 160°C for 10 minutes.

[0078] S3: The first coating is etched to form microgrooves;

[0079] The etching process is plasma etching, which uses argon gas at a power of 300W and a processing time of 2 minutes.

[0080] The microgrooves are 12μm wide and 4μm deep, with a center-to-center distance of 30μm between adjacent microgrooves. The direction of the microgrooves is 30° to the axis of the aluminum flat wire and the angle is consistent. The microgrooves are respectively set on the two narrow sides of the aluminum flat wire.

[0081] S4: Glass fiber is mixed with polyimide to obtain a secondary treatment liquid. The secondary treatment liquid is coated onto the first coating and subjected to a second curing treatment to form a second coating, thereby obtaining a high-adhesion thin-film sintered aluminum flat wire.

[0082] In S4, the glass fiber has a diameter of 10μm and a length of 120μm. The surface of the glass fiber is treated with a silane coupling agent, and the amount of glass fiber added is 15wt% of the solid content of the polyimide resin.

[0083] The polyimide resin solid content in S4 is 20wt%, the mixing speed in S4 is 400rpm, and the mixing time is 45min.

[0084] The second curing process involves treating at 100°C for 12 minutes, then heating to 200°C at a rate of 2°C / min and holding for 20 minutes, followed by heating to 300°C at a rate of 4°C / min and holding for 30 minutes.

[0085] The first coating has a thickness of 30 μm, and the second coating has a thickness of 60 μm.

[0086] Example 2:

[0087] The difference between this embodiment and Embodiment 1 is that the depth of the microgroove is 6μm, while the rest are the same.

[0088] Example 3:

[0089] The difference between this embodiment and Embodiment 1 is that the depth of the microgroove is 8μm, while the rest are the same.

[0090] Example 4:

[0091] The difference between this embodiment and Embodiment 1 is that the depth of the microgroove is 10 μm, while the rest are the same.

[0092] Example 5:

[0093] The difference between this embodiment and Embodiment 1 is that the depth of the microgroove is 12μm, while the rest are the same.

[0094] Example 6:

[0095] The difference between this embodiment and Embodiment 3 is that the thickness of the first coating is 15 μm, while the rest are the same.

[0096] Example 7:

[0097] The difference between this embodiment and Embodiment 3 is that the thickness of the first coating is 45 μm, while the rest are the same.

[0098] Example 8:

[0099] The difference between this embodiment and Embodiment 3 is that the thickness of the first coating is 60 μm, while the rest are the same.

[0100] Example 9:

[0101] The difference between this embodiment and Embodiment 3 is that the thickness of the first coating is 75 μm, while the rest are the same.

[0102] Comparative Example 1:

[0103] This comparative example provides a process for preparing thin-film sintered aluminum flat wire, including the following steps:

[0104] S1: The aluminum conductor itself undergoes surface pretreatment, which includes degreasing and surface roughening. The degreasing process involves using an 8wt% silicate solution with a pH of 10, controlling the temperature at 60℃, immersing for 3-10 minutes, and then cleaning thoroughly. The surface roughening process involves using a 6wt% phosphoric acid solution, treating at room temperature for 3 minutes, and then cleaning thoroughly to obtain the pretreated substrate.

[0105] S2: Polyester resin is used as a primary treatment liquid. The primary treatment liquid is coated onto the pretreated substrate in S1 and subjected to a first curing treatment to form a first coating. The solid content of the polyester resin is 50%.

[0106] S2 mixing involves stirring at 2500 rpm for 45 minutes, followed by a first curing process of preheating at 110°C for 3 minutes and then sintering in a furnace at 160°C for 10 minutes.

[0107] S3: Polyimide resin is used as a secondary treatment liquid. The secondary treatment liquid is coated onto the first coating and then subjected to a second curing treatment to form a second coating, thereby obtaining a high-adhesion thin-film sintered aluminum flat wire.

[0108] The polyimide resin solid content is 20wt%, the mixing speed in S4 is 400rpm, and the mixing time is 45min.

[0109] The second curing process involves treating at 100°C for 12 minutes, then heating to 200°C at a rate of 2°C / min and holding for 20 minutes, followed by heating to 300°C at a rate of 4°C / min and holding for 30 minutes.

[0110] The first coating has a thickness of 45 μm, and the second coating has a thickness of 60 μm.

[0111] Examples 1-9 and Comparative Example 1 were subjected to interface bonding strength and bending fatigue tests. The interface strength test standard was ASTM D903. The bending fatigue test standard was to repeatedly bend an aluminum flat wire around a round bar with a diameter of 20 mm, with a bending angle of ±90° and a bending frequency of 1 time / second. The number of insulation failures was recorded, and the data are shown in Table 1.

[0112] Table 1. Interfacial bond strength and flexural fatigue test data of Examples 1-9 and Comparative Example 1

[0113] Data source Interfacial bonding strength (N / mm) Number of insulation failures (times) Example 1 5.2 65824 Example 2 5.8 70947 Example 3 6.3 73149 Example 4 5.9 71093 Example 5 5.4 69381 Example 6 5.7 71354 Example 7 7.0 78396 Example 8 6.6 74628 Example 9 6.1 72039 Comparative Example 1 3.5 31853

[0114] As shown in Table 1, the interfacial bonding strength and flexural fatigue resistance of Examples 1-9 are greater than those of Comparative Example 1, indicating that this application has superiority.

[0115] In Examples 1-5, as the depth of the microgrooves increases, the interfacial bonding strength and resistance to flexural fatigue first increase and then decrease. This is because the increase in microgroove depth provides a larger mechanical anchor volume and a deeper fiber intercalation depth, thereby significantly enhancing the coating's anti-peeling ability. However, when the depth increases excessively, the excessively deep grooves will excessively weaken the effective load-bearing thickness of the primary coating interfacial layer and generate new stress concentration points at the sharp corners of the groove bottom. Simultaneously, it increases the risk of air bubbles encapsulating at the bottom of the groove during the coating process, which can become the origin of crack initiation, leading to a decrease in bonding strength and fatigue performance. Example 3 is the preferred embodiment.

[0116] In Examples 3 and 6-9, as the thickness of the first coating increases, the interfacial bonding strength and resistance to bending fatigue both first increase and then decrease. This is because increasing the thickness of the first coating provides more sufficient volume to accommodate the metal filler and construct the microgroove structure, enhancing the mechanical anchoring effect and improving stress buffering capacity. However, when the thickness increases excessively, the overly thick coating will generate significantly increased internal stress during the curing and cooling process due to the greater difference in thermal expansion coefficients between it and the aluminum substrate. At the same time, the flexibility of the coating itself decreases, making it prone to brittle cracking rather than plastic deformation under bending loads, which weakens the interfacial stability and reduces fatigue resistance. The preferred embodiment is Example 7.

[0117] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A process for preparing high-adhesion thin-film sintered aluminum flat wire, characterized in that, Includes the following steps: S1: The aluminum conductor itself is pretreated to obtain a pretreated substrate; S2: Tin oxide powder is mixed with polyester resin to obtain a primary treatment solution. The primary treatment solution is coated onto the pretreated substrate in S1 and subjected to a first curing treatment to form a first coating. S3: The first coating is etched to form microgrooves; S4: Glass fiber is mixed with polyimide to obtain a secondary treatment liquid. The secondary treatment liquid is coated onto the first coating and subjected to a second curing treatment to form a second coating, thereby obtaining a high-adhesion thin-film sintered aluminum flat wire.

2. The preparation process of a high-adhesion thin-film sintered aluminum flat wire according to claim 1, characterized in that: The surface pretreatment in S1 includes a degreasing process and surface roughening; the degreasing process specifically involves using a silicate solution with a concentration of 5-10 wt% and a pH value of 10-12, controlling the temperature at 50-70℃, soaking or spraying for 3-10 minutes, and then cleaning thoroughly; the surface roughening process specifically involves using a 5-10 wt% phosphoric acid or nitric acid solution, treating at room temperature to 40℃ for 30 seconds to 5 minutes, and then cleaning thoroughly.

3. The preparation process of a high-adhesion thin-film sintered aluminum flat wire according to claim 1, characterized in that: The tin oxide powder in S2 has a particle size of 1-5 μm and is added at 10-30 wt% of the solid content of the polyester resin, with the solid content of the polyester resin being 40-60%.

4. The preparation process of a high-adhesion thin-film sintered aluminum flat wire according to claim 1, characterized in that: The S2 mixing process involves stirring at 1000-3000 rpm for 30-60 minutes, followed by a first curing treatment at 80-120°C for 2-5 minutes, and then treatment in a sintering furnace at 150-180°C for 5-15 minutes.

5. The preparation process of a high-adhesion thin-film sintered aluminum flat wire according to claim 1, characterized in that: The etching process in S3 is plasma etching or laser micromachining. The plasma etching uses oxygen or argon gas, with a power of 200-500W and a processing time of 30s to 3min.

6. The preparation process of a high-adhesion thin-film sintered aluminum flat wire according to claim 1, characterized in that: The microgrooves are 5-20μm wide and 6-10μm deep, with a center-to-center distance of 15-40μm between adjacent microgrooves. The direction of the microgrooves is 30°-45° to the axial direction of the aluminum flat wire and the angle is consistent. The microgrooves are respectively disposed on the two narrow sides of the aluminum flat wire.

7. The preparation process of a high-adhesion thin-film sintered aluminum flat wire according to claim 1, characterized in that: The glass fiber in S4 has a diameter of 5-15 μm and a length of 50-200 μm. The surface of the glass fiber is treated with a silane coupling agent, and the amount of glass fiber added is 5-20 wt% of the solid content of the polyimide resin.

8. The preparation process of a high-adhesion thin-film sintered aluminum flat wire according to claim 1, characterized in that: The polyimide resin solid content in S4 is 15-30wt%, the mixing speed in S4 is 300-600rpm, and the mixing time is 30-60min.

9. The preparation process of a high-adhesion thin-film sintered aluminum flat wire according to claim 1, characterized in that: The second curing process involves treating at 80-120℃ for 5-15 minutes, then heating at a rate of 1-3℃ / min to 180-220℃ and holding for 10-20 minutes, followed by heating at a rate of 2-5℃ / min to 280-320℃ and holding for 20-40 minutes.

10. A high-adhesion thin-film sintered aluminum flat wire, based on the preparation process of a high-adhesion thin-film sintered aluminum flat wire according to any one of claims 1-9, characterized in that: The thickness of the first coating is 30-60 μm, and the thickness of the second coating is 40-80 μm.

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