Ultrasonic welding method for anodized alumina powder sintered foil and lead

Abstract

The invention relates to the technical field of aluminum electrolytic capacitor manufacturing, in particular to an ultrasonic welding method for an anodic aluminum oxide powder sintered foil and a lead. According to the ultrasonic welding method, the aluminum oxide film is accurately broken through segmented frequency-power cooperative control, metallurgical bonding is achieved, and meanwhile mechanical performance reduction of the aluminum foil is avoided. The method comprises the following steps: under a protective atmosphere, carrying out first-section welding according to a first process parameter so as to break an aluminum oxide film; and second-section welding is carried out according to a second process parameter to achieve metallurgical bonding, ultrasonic welding of the anodized aluminum oxide powder sintered foil and the lead is completed, and the problems that an existing welding method is prone to causing large aluminum foil contact resistance, aluminum foil brittle fracture, mechanical performance reduction and unstable welding quality are solved.

Description

Technical Field

[0001] This invention relates to the field of aluminum electrolytic capacitor manufacturing technology, specifically to an ultrasonic welding method for sintered foil made of anodic aluminum oxide powder and leads. Background Technology

[0002] Aluminum powder sintered foil, produced using additive manufacturing, is environmentally friendly. Compared to etched aluminum foil, the resulting foil has a larger specific surface area and higher specific capacitance, making it a promising method for manufacturing porous aluminum foil. Anodized aluminum foil, obtained by anodizing aluminum powder sintered foil, can be used as anode foil in aluminum electrolytic capacitors, significantly increasing energy density and reducing size. In the manufacturing of aluminum electrolytic capacitors, leads need to be welded to the aluminum core in the anodized aluminum foil to form an electron conduction channel. However, the thickness of the insulating alumina layer on the surface of the anodized aluminum foil is typically tens to hundreds of nanometers. This insulating alumina layer needs to be broken to achieve aluminum-to-aluminum connectivity. Simultaneously, the aluminum powder spheres in the sintered foil form a three-dimensional porous structure connected by sintered necks. Its bending strength is much lower than that of traditional etched aluminum foil, making the sintered necks prone to cracking and brittle fracture during lead welding, leading to a sharp increase in capacitor leakage current and failure. Therefore, effective welding of the anodized aluminum powder sintered foil to the leads is a crucial manufacturing step for its successful application in aluminum electrolytic capacitors.

[0003] Currently, common welding methods include resistance welding, cold riveting, laser welding, and ultrasonic welding. Among them, ultrasonic welding utilizes the high-frequency vibration of an ultrasonic vibrator, which is transmitted through the welding head to the contact point between the guide pin and the aluminum foil, causing the oxide film on the contact surface to break down and metal atoms to diffuse and bond together. While existing ultrasonic welding technology can reduce damage to three-dimensional structures to some extent by adjusting parameters such as frequency, amplitude, pressure, and contact time, it still has certain technical drawbacks: for example, insufficient breakdown of the oxide film at the welding interface results in a high residual rate, leading to high contact resistance; the sintering neck of the aluminum powder is prone to cracking during welding, easily damaging the aluminum foil structure and causing a decline in the mechanical properties of the aluminum foil; furthermore, aluminum is prone to re-oxidation during welding, affecting the stability of weld quality. Summary of the Invention

[0004] To address the problems of high contact resistance, brittle fracture, decreased mechanical properties, and unstable welding quality associated with existing welding methods, this invention provides an ultrasonic welding method for sintered alumina powder foil and leads. This ultrasonic welding method primarily achieves metallurgical bonding by precisely breaking down the alumina film through segmented frequency-power coordinated control, while simultaneously preventing aluminum foil cracking and decreased mechanical properties.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows.

[0006] This invention provides an ultrasonic welding method for sintered aluminum oxide powder foil and leads, comprising the following steps: First and second process parameters for ultrasonic welding are set. Under a protective atmosphere, the first stage of welding is performed using the first process parameters to break the alumina film. The second stage of welding is performed using the second process parameters to achieve metallurgical bonding, thus completing the ultrasonic welding of the sintered alumina powder foil and the lead wire. The first process parameters are: frequency 30kHz~40kHz, power 1500W~2000W, amplitude 8μm~10μm, pressure 0.3MPa~0.7MPa, and time 0.01s~0.5s. The second process parameters are: frequency 20kHz~30kHz, power 1000W~1500W, amplitude 5μm~8μm, pressure 0.1MPa~0.5MPa, and time 0.5s~2.5s.

[0007] In this invention, after performing ultrasonic welding of anodized aluminum powder sintered foil and lead wire, a cooling interval is required, followed by vibration of the welding head. The cooling interval is 0.01s to 1s, and the welding head vibration time is 0.01s to 3s to achieve head retraction vibration. The pressure for performing head retraction vibration is 0 to prevent the ultrasonic head from sticking to the aluminum foil.

[0008] Preferably, after the second stage of welding, the residual alumina film of the sintered foil of anodic aluminum oxide powder is <2%, the contact resistance is <0.1mΩ, and the tensile strength is >10N / weld point.

[0009] Preferably, the frequency and power of the first and second welding stages are determined by the following formula: P = 4μSFAf; where P represents power in W; μ represents the coefficient of friction; and S represents the weld area in mm. 2 F represents pressure, in N; A represents amplitude, in μm; f represents frequency, in kHz.

[0010] In the ultrasonic welding of this invention, frequency and power are in a proportional and synergistic relationship (P∝f), which can be quantified by the power calculation formula above.

[0011] In this invention, the effective welding area of ​​the sintered alumina powder foil is related to the power, pressure, amplitude, and frequency. The required weld area can be obtained by adjusting the corresponding parameters through the system. Specifically, the weld area of ​​the first welding stage is small to avoid damaging the internal sintering neck and breaking the alumina film. Appropriate amplitude, increased frequency, and power concentrate the force on the alumina shell.

[0012] The synergistic mechanism between frequency and power is as follows: The effect of frequency on energy distribution: Low frequency (15kHz~20kHz) has a longer wavelength and a greater energy penetration depth, but the amplitude is large, which can easily lead to cracking of aluminum powder sintered foil; High frequency (30kHz~40kHz) has a shorter wavelength, the energy is concentrated on the surface and the amplitude is small, which can reduce foil damage, but higher power is required to compensate for the energy dispersion defect.

[0013] Enhancement of frequency effect by power: For high-frequency welding (30kHz~40kHz), medium to high power (1500W~2000W) is required to achieve: oxide film breakage, sufficient frictional heat to break Al2O3 through plastic deformation; metallurgical bonding, so that the contact surface reaches the atomic diffusion temperature (400℃~500℃) to form a solid metallurgical bond.

[0014] Based on the characteristics of sintered foil made from anodized aluminum powder, this invention employs a two-stage frequency-power coordinated control. The first stage of welding is the oxide film breaking stage, with a frequency of 30kHz to 40kHz, a power of 1500W to 2000W, an amplitude of 8μm to 10μm, a pressure of 0.3MPa to 0.7MPa, and a time of 0.01s to 0.5s. The advantage is that the energy is concentrated on the surface oxide film without damaging the internal sintering neck, and the oxide film breaking rate is >98%. The second stage of welding is the metallurgical bonding stage, with a frequency of 20kHz to 30kHz, a power of 1000W to 1500W, an amplitude of 5μm to 8μm, a pressure of 0.1MPa to 0.5MPa, and a time of 0.5s to 2.5s. The advantage is that the wavelength is longer, allowing the energy to penetrate into the aluminum powder, promoting atomic diffusion to form a strong metallurgical bond and avoiding incomplete welding.

[0015] This invention selects process parameters such as power and frequency for the first welding stage and uses high-frequency vibration (30kHz~40kHz) to concentrate energy on the oxide film. If the frequency is lower than 30kHz, the alumina film cannot be broken; if the power is too high, it will damage the internal sintering neck. Therefore, the power and frequency are quantified based on the power calculation formula.

[0016] This invention selects process parameters such as power and frequency for the second stage of welding, and uses low-frequency vibration (20kHz~30kHz) with a relatively long wavelength and a relatively long heating time to allow energy to penetrate into the aluminum powder and promote atomic diffusion to form a strong metallurgical bond.

[0017] It should be noted that the outer surface of the anodic aluminum oxide powder sintered foil is an aluminum oxide film, and the inside is aluminum powder; the aluminum powder partially fuses to form a sintering neck, and the aluminum oxide film is formed on the oxidized surface. This invention ensures welding consistency through real-time monitoring.

[0018] Preferably, the protective atmosphere is nitrogen and / or argon, and the flow rate of the protective atmosphere is 10 L / min to 20 L / min. The protective atmosphere of the present invention is mainly an inert gas protection to prevent oxidation during the welding process.

[0019] Preferably, the thickness of the sintered foil made of anodic aluminum oxide powder is 60 μm to 200 μm.

[0020] Preferably, before performing the first welding, the lead wire is placed on the sintered foil of anodized aluminum powder and the ultrasonic welding head is pressed tightly onto the lead wire.

[0021] Preferably, the lead is a metal pin or a metal sheet lead; the material of the lead is copper or aluminum.

[0022] Preferably, the diameter of the metal guide pin is 1.5mm to 3mm; the width of the metal sheet lead is 3mm to 5mm. The method of the present invention is adapted to sintered aluminum powder foil of 50μm to 200μm and is compatible with aluminum / copper / nickel guide pins.

[0023] Preferably, the sintered aluminum oxide powder foil undergoes a pretreatment process before ultrasonic welding; the pretreatment method for the sintered aluminum oxide powder foil is as follows: The surface of the sintered foil made of anodized aluminum oxide powder is purged using a purging atmosphere, which may be air, nitrogen, or argon. The purpose is to remove impurities or debris from the surface of the sintered foil made of anodized aluminum oxide powder.

[0024] The beneficial effects of this invention are: 1. This invention achieves frequency and power coordinated control through segmentation, precisely breaks the alumina film, and protects the sintering neck, thereby achieving the integrity of the three-dimensional structure (sintering neck integrity rate >99%, bending strength increased by 45%), efficient oxide film breaking (residual rate <2%, contact resistance <0.1mΩ), and strong metallurgical bonding (strength >10N / weld point, false weld rate <1%). It solves the problems of high aluminum foil contact resistance, brittle aluminum foil, decreased mechanical properties, and insufficient welding quality in existing welding methods. Attached Figure Description

[0025] Figure 1 Electron photographs of the surface and cross-section of anodic aluminum oxide powder sintered foil and wide aluminum sheet leads welded using the conventional ultrasonic welding method employed in Comparative Example 1 are shown. (a) is a surface electron photograph; (b) is a cross-sectional electron photograph.

[0026] Figure 2 Electron photographs of the surface and cross-section of anodized aluminum powder sintered foil welded to a φ3mm aluminum guide needle using the ultrasonic welding method of Embodiment 3 of the present invention. (a) is a surface electron photograph; (b) is a cross-sectional electron photograph.

[0027] Figure 3This is a schematic diagram of the ultrasonic welding process of sintered aluminum oxide powder foil and lead wire provided in an embodiment of the present invention. (a) shows the welding process before welding; (b) shows oxide film breakage; (c) shows aluminum powder diffusion; and (d) shows metallurgical bonding. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] 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.

[0030] Because of the insulating aluminum oxide layer on the surface of anodic aluminum powder sintered foil, which is tens to hundreds of nanometers thick, it is necessary to break the insulating aluminum oxide layer before connecting the lead wire to the aluminum core in the anodic aluminum powder foil to achieve the connection between aluminum. At the same time, the aluminum powder balls in the aluminum powder sintered foil are connected by sintering necks to form a three-dimensional hole structure. The bending strength is much lower than that of traditional etched foil. When the lead wire is welded, it is very easy to cause the sintering neck to crack and break brittlely, resulting in a sharp increase in the leakage current of the capacitor and failure.

[0031] Current welding technologies are insufficient to solve the connection problem between sintered aluminum oxide powder foil and leads, exhibiting the following technical shortcomings: Insufficient oxide film fragmentation: Existing ultrasonic welding does not have specific parameters designed for the alumina insulation layer, resulting in a high oxide film residue rate and high contact resistance at the welding interface.

[0032] Aluminum foil structure is easily damaged: lack of precise control over welding energy can easily cause cracking of the aluminum powder sintering neck and a decline in the mechanical properties of aluminum foil.

[0033] No oxidation protection: During the welding process, the molten aluminum is easily oxidized again, affecting the stability of the welding quality.

[0034] The process parameters are limited: the porous structure of sintered aluminum oxide powder foil is not taken into account, making it unsuitable for foils of different thicknesses and various guide pin materials.

[0035] For example, in prior art 1, patent application CN116031070A uses a conventionally etched aluminum foil as the anode foil, and its ultrasonic welding point is the positive electrode conductive foil strip and the lead terminal. In prior art 2, patent application CN113257574B uses a conventionally etched aluminum foil as the anode foil, and its ultrasonic welding point is between the conductive foil strip and the lead; the connection between the lead and the conductive foil strip is achieved through a washer-based piercing connection. In prior art 3, patent application US7279686B2 uses a conventionally etched aluminum foil as the anode foil, and its ultrasonic welding point is between the electrode foil and the lead.

[0036] However, the existing technology differs from the foil structure used in this invention. Although both foils have an aluminum oxide film on their surface after anodizing, the traditional welding of etched aluminum foil uses single-frequency ultrasonic welding (without segmented design), which is also unsuitable for welding the anodized aluminum powder sintered foil and leads of this invention. Furthermore, the above welding method is not designed for the special structure of the anodized aluminum powder sintered foil (such as high specific surface area and porous structure), and single-frequency welding will lead to the breakage and embrittlement of the aluminum powder sintered foil.

[0037] Based on this, the present invention provides an ultrasonic welding method for sintered aluminum oxide powder foil and leads, which precisely breaks the oxide film and achieves metallurgical bonding through segmented frequency-power coordinated control, while avoiding the degradation of the mechanical properties of the aluminum foil.

[0038] The technical solution of the present invention will be further described below through specific embodiments.

[0039] In the following embodiments, unless otherwise specified, the methods described are conventional methods; and unless otherwise specified, the reagents and materials described are commercially available.

[0040] Example 1 like Figure 3 An ultrasonic welding method for sintered aluminum oxide powder foil and leads includes the following steps: Pretreatment: The surface of the sintered aluminum oxide powder foil is purged with dry, clean air, nitrogen, or argon to remove debris. The thickness of the sintered aluminum oxide powder foil is 120 μm, and the lead wire is a φ2 mm copper guide pin.

[0041] A 120μm anodic aluminum oxide powder sintered foil was ultrasonically welded to a φ2mm copper guide pin. First and second process parameters for ultrasonic welding were set. Under a protective atmosphere, the first stage of welding was performed using the first process parameters to break up the aluminum oxide film; the second stage of welding was performed using the second process parameters to achieve metallurgical bonding, thus completing the ultrasonic welding of the anodic aluminum oxide powder sintered foil and the lead wire. The first and second process parameters are shown in Table 1.

[0042] Table 1 Process parameters of Example 1 The welding effect of Example 1 shows that the oxide film at the weld joint has a high breakage rate, while the sintered neck is intact, without cracking or collapse. The tensile strength is 12N / weld joint, the contact resistance is 0.039mΩ, and the overall appearance is free of cracks and burn-through, with a smooth weld joint.

[0043] Example 2 An ultrasonic welding method for sintered aluminum oxide powder foil and leads includes the following steps: Pretreatment: The surface of the sintered aluminum oxide powder foil is purged with dry, clean air, nitrogen, or argon to remove debris. The thickness of the sintered aluminum oxide powder foil is 60 μm, and the lead wire is a φ1.5 mm nickel guide pin.

[0044] A 60μm anodic aluminum oxide powder sintered foil was ultrasonically welded to a φ1.5mm nickel guide needle. First and second process parameters for ultrasonic welding were set. Under a protective atmosphere, the first stage of welding was performed using the first process parameters to break up the aluminum oxide film; the second stage of welding was performed using the second process parameters to achieve metallurgical bonding, thus completing the ultrasonic welding of the anodic aluminum oxide powder sintered foil and the lead wire. The first and second process parameters are shown in Table 2.

[0045] Table 2 Process parameters of Example 2 The welding results of Example 2 show that there is no burn-through at the weld, the oxide film has a high breakage rate, the tensile strength is 10.5 N / weld point, and the contact resistance is 0.051 mΩ.

[0046] Example 3 An ultrasonic welding method for sintered aluminum oxide powder foil and leads includes the following steps: Pretreatment: The surface of the sintered aluminum oxide powder foil is purged with dry, clean air, nitrogen, or argon to remove debris. The thickness of the sintered aluminum oxide powder foil is 200 μm, and the lead wire is a φ3 mm aluminum guide pin.

[0047] A 200μm anodic aluminum oxide powder sintered foil was ultrasonically welded to a φ3mm aluminum guide needle. First and second process parameters for ultrasonic welding were set. Under a protective atmosphere, the first stage of welding was performed using the first process parameters to break up the aluminum oxide film; the second stage of welding was performed using the second process parameters to achieve metallurgical bonding, thus completing the ultrasonic welding of the anodic aluminum oxide powder sintered foil and the lead wire. The first and second process parameters are shown in Table 3.

[0048] Table 3 Process parameters of Example 3 Figure 2 Electron photographs of the surface and cross-section of anodized aluminum powder sintered foil welded to a φ3mm aluminum guide needle using the ultrasonic welding method of Embodiment 3 of the present invention. The welding effect of Embodiment 3 shows no internal cracking, a high oxide film breakage rate at the weld, a tensile strength of 15N / weld point, and a contact resistance of 0.076mΩ.

[0049] Example 4 An ultrasonic welding method for sintered aluminum oxide powder foil and leads includes the following steps: Pretreatment: The surface of the sintered aluminum oxide powder foil is purged with dry, clean air, nitrogen, or argon to remove debris. The thickness of the sintered aluminum oxide powder foil is 150 μm, and the leads are 5 mm wide aluminum sheet leads.

[0050] A 200μm anodic aluminum oxide powder sintered foil was ultrasonically welded to a 5mm wide aluminum sheet lead wire. First and second process parameters for ultrasonic welding were set. Under a protective atmosphere, the first stage of welding was performed using the first process parameter to break up the aluminum oxide film; the second stage of welding was performed using the second process parameter to achieve metallurgical bonding, thus completing the ultrasonic welding of the anodic aluminum oxide powder sintered foil and the lead wire. The first and second process parameters are shown in Table 4.

[0051] Table 4 Process parameters of Example 4 The welding effect of Example 4 shows that the metallurgical bonding layer is continuous and without gaps, the oxide film breakage rate at the weld is high, the tensile strength is 13N / weld point, and the contact resistance is 0.061mΩ.

[0052] Example 5 An ultrasonic welding method for sintered aluminum oxide powder foil and leads includes the following steps: Pretreatment: The surface of the sintered aluminum oxide powder foil is purged with dry, clean air, nitrogen, or argon to remove debris. The thickness of the sintered aluminum oxide powder foil is 130 μm, and the leads are 3 mm wide aluminum sheet leads.

[0053] A 130μm anodic aluminum oxide powder sintered foil was ultrasonically welded to a 3mm wide aluminum sheet lead wire. First and second process parameters for ultrasonic welding were set. Under a protective atmosphere, the first stage of welding was performed using the first process parameter to break up the aluminum oxide film; the second stage of welding was performed using the second process parameter to achieve metallurgical bonding, thus completing the ultrasonic welding of the anodic aluminum oxide powder sintered foil and the lead wire. The first and second process parameters are shown in Table 5.

[0054] Table 5 Process parameters of Example 5 The welding results of Example 5 show that the welding consistency is excellent, the oxide film breakage rate at the weld is high, the tensile strength is 12.5 N / weld point, and the contact resistance is 0.036 mΩ.

[0055] Practical application experiments show that when the aluminum foil obtained by the welding process of Example 5 of the present invention is wound into an aluminum electrolytic capacitor, its equivalent series resistance decreases from 71.86mΩ to 54.72mΩ, and the loss decreases from 5.41 to 4.38.

[0056] Example 6 An ultrasonic welding method for sintered aluminum oxide powder foil and leads includes the following steps: Pretreatment: The surface of the sintered aluminum oxide powder foil is purged with dry, clean air, nitrogen, or argon to remove debris. The thickness of the sintered aluminum oxide powder foil is 150 μm, and the leads are 5 mm wide aluminum sheet leads.

[0057] A 150μm anodic aluminum oxide powder sintered foil was ultrasonically welded to a 5mm wide aluminum sheet lead wire. First and second process parameters for ultrasonic welding were set. Without inert gas protection, the first stage of welding was performed using the first process parameters to break up the aluminum oxide film; the second stage of welding was performed using the second process parameters to achieve metallurgical bonding, thus completing the ultrasonic welding of the anodic aluminum oxide powder sintered foil and the lead wire. The first and second process parameters are shown in Table 6.

[0058] Table 6 Process parameters of Example 6 The welding results of Example 6 show that the oxide film at the weld joint has a high breakage rate, the sintering neck is intact, the tensile strength is 9N / weld joint, and the contact resistance is 1mΩ.

[0059] Experimental results show that without inert gas protection, molten aluminum exposed to air produces a new oxide film, leading to secondary oxidation of the welding interface, decreased tensile strength, and increased contact resistance.

[0060] Comparative Example 1 An ultrasonic welding method for sintered aluminum oxide powder foil and leads includes the following steps: Pretreatment: The surface of the sintered aluminum oxide powder foil is purged with dry, clean air, nitrogen, or argon to remove debris. The thickness of the sintered aluminum oxide powder foil is 130 μm, and the leads are 3 mm wide aluminum sheet leads.

[0061] The ultrasonic welding process parameters were set, and under no inert gas protection, 130μm anodic aluminum oxide powder sintered foil was ultrasonically welded to a 3mm wide aluminum sheet lead wire according to the set ultrasonic welding process parameters. The ultrasonic welding process parameters are shown in Table 7.

[0062] Table 7 Process parameters of Comparative Example 1 Comparative Example 1 uses conventional ultrasonic welding to weld sintered foil of anodized aluminum powder and a 3mm wide aluminum sheet lead wire. The results are as follows: Figure 1 As shown.

[0063] Figure 1 Electron photographs of the surface and cross-section of anodic aluminum oxide powder sintered foil and wide aluminum sheet leads welded using the conventional ultrasonic welding method employed in Comparative Example 1.

[0064] The welding results of Comparative Example 1 show that there is a lot of residual oxide film at the weld, severe cracking of the sintering neck, cracks on the foil surface, tensile strength of 6N / weld point, and contact resistance of 3mΩ.

[0065] In summary, the embodiments of the present invention provide an ultrasonic welding method for sintered foil made of anodic aluminum oxide powder, based on the proportional relationship between power and frequency, such as... Figure 3 The method employs a two-stage frequency-power matching: the first stage uses high frequency + medium-high power + short-time oxide film breaking; the second stage uses medium frequency + medium power + long time to achieve metallurgical bonding. Combined with pretreatment, inert gas protection, and real-time monitoring, it can ensure the integrity of the three-dimensional structure of the aluminum foil, with a weld joint tensile strength >10N / weld point, contact resistance <0.1mΩ, and an alumina film residue rate <2%. The ultrasonic welding method provided by this invention solves the problems of brittle aluminum foil fracture and high contact resistance caused by traditional welding methods, and is suitable for welding foils of different thicknesses and various guide pin materials.

[0066] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An ultrasonic welding method for sintered foil made of anodized aluminum powder and leads, characterized in that, Includes the following steps: Set the first and second process parameters for ultrasonic welding; Under a protective atmosphere, the first stage of welding is performed with the first process parameters to break the alumina film; the second stage of welding is performed with the second process parameters to achieve metallurgical bonding, thus completing the ultrasonic welding of the sintered foil of anodic alumina powder and the lead wire. The first process parameters are: frequency 30kHz~40kHz, power 1500W~2000W, amplitude 8μm~10μm, pressure 0.3MPa~0.7MPa, and time 0.01s~0.5s; The second process parameters are: frequency 20kHz~30kHz, power 1000W~1500W, amplitude 5μm~8μm, pressure 0.1MPa~0.5MPa, and time 0.5s~2.5s.

2. The ultrasonic welding method for sintered aluminum oxide powder foil and leads according to claim 1, characterized in that, After the second stage of welding, the residual alumina film of the sintered foil of anodic aluminum oxide powder is <2%, the contact resistance is <0.1mΩ, and the tensile strength is >10N / weld point.

3. The ultrasonic welding method for sintered aluminum oxide powder foil and leads according to claim 1, characterized in that, The frequency and power of the first and second welding stages are determined by the following formula: P=4μSFAf; Where P represents power; μ represents the coefficient of friction; S represents the weld area; F represents pressure; A represents amplitude; and f represents frequency.

4. The ultrasonic welding method for sintered aluminum oxide powder foil and leads according to claim 1, characterized in that, The protective atmosphere is nitrogen and / or argon, and the flow rate of the protective atmosphere is 10 L / min to 20 L / min.

5. The ultrasonic welding method for sintered aluminum oxide powder foil and leads according to claim 1, characterized in that, The thickness of the sintered foil made of anodized aluminum powder is 60μm to 200μm.

6. The ultrasonic welding method for sintered aluminum oxide powder foil and leads according to claim 1, characterized in that, Before performing the first welding, place the lead wire on the sintered foil of anodized aluminum powder and press the ultrasonic welding head firmly onto the lead wire.

7. The ultrasonic welding method for sintered aluminum oxide powder foil and leads according to claim 1 or 6, characterized in that, The lead is a metal pin or a metal sheet lead; the material of the lead is copper or aluminum.

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