Foil micropore machining method based on laser hole guiding and acid pickling reaming

Abstract

The invention discloses a foil micropore machining method based on laser hole guiding and acid pickling reaming. The method comprises the following steps of aluminum foil pretreatment, laser hole guiding, corrosive liquid preparation, acid pickling reaming, cleaning and passivation, vacuum drying and smashing treatment. According to the method, the initial hole site precision is ensured through laser hole guiding, the hole diameter uniformity is achieved through pressure regulation and control in acid pickling hole expanding, and the requirement of T / CESA 1210-2022 for the porosity of the super capacitor aluminum foil is met. A photoresist coating step is omitted, and the use of an organic solvent is reduced; the cyclic utilization rate of the pickling solution is increased by 30%, the cost is reduced, and environmental protection is achieved. And the aluminum foil with the thickness of 10-300 microns can be processed, and materials such as copper foils and nickel foils are compatible, so that the adaptability is wide.

Description

Technical Field

[0001] The invention relates to the technical field of metal foil micro-hole processing, in particular to a foil micro-hole processing method based on laser hole drawing and pickling hole expansion. Background Art

[0002] Existing technologies such as laser drilling suffer from large taper and low aspect ratio, and are prone to burrs when processing small apertures. Chemical etching requires multiple steps (such as photoresist coating and development), resulting in high pollution and cost. Stamping, however, is limited by molds and struggles to achieve uniform distribution of micron-level apertures.

[0003] Guangdong Yutong's patent (CN107130245A) optimizes the pore size through a mixed system of annealing and etching liquid, but does not solve the problem of initial pore forming accuracy; Shanxi Wertheimer's process (T / CESA 1210-2022) emphasizes the porosity standard of microporous aluminum foil, but relies on traditional etching technology with low efficiency. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a foil micro-hole processing method based on laser hole drawing and pickling hole expansion to solve the current problem of low initial hole forming accuracy in foil.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] The foil micro-hole processing method based on laser hole drawing and pickling hole expansion includes the following steps:

[0007] S1: Pretreatment of aluminum foil

[0008] Annealing treatment: Aluminum foil is annealed at 200-600℃ for 10min-24h to eliminate internal stress and improve material uniformity;

[0009] Degreasing and cleaning: Use 0.01-4wt% sodium hydroxide solution, temperature 0-100℃, soak for 10s-1min to remove surface grease;

[0010] S2: Laser drilling

[0011] A pulsed fiber laser is used to form initial micropores on the surface of the aluminum foil, with a pore diameter of 5-50μm and a depth of 20-50% of the foil thickness. A combination of galvanometer scanning and a rotating wave plate set is used to adjust the laser polarization state, reduce the heat-affected zone, and improve the smoothness of the pore wall.

[0012] S3: Pickling and reaming

[0013] Preparation of etching solution: Mix 10% hydrochloric acid with 0.0001-2 mol / L AlCl3 buffer solution, with a molar concentration ratio of 1:0.01-0.5, and the temperature is 30-60℃;

[0014] Dynamic pressure expansion: Using pressure wave circulation, alternating positive and negative pressures are applied to the etching liquid in the range of 0.1-5MPa, driving the etching liquid through the laser initial hole to form turbulence, accelerating the sidewall corrosion, and ultimately expanding the hole diameter to 10-100μm and eliminating burrs;

[0015] S4: Subsequent processing

[0016] Cleaning and passivation: Use 0.02-2 mol / L nitric acid solution in a 5-90°C environment for 1-3 minutes to remove residual corrosion products; after nitric acid cleaning, perform an anodizing step to reduce the surface resistance of the aluminum foil.

[0017] Vacuum drying: adopts segmented vacuum drying (the first stage is 100℃ / 10kPa to remove moisture, and the second stage is 250℃ / 0.1kPa to eliminate thermal stress) to avoid pore collapse and improve the porosity stability to 99.5%.

[0018] Preferably, in step S2, an energy density gradient adjustment module is introduced during the laser drilling stage to adjust the pulse energy in real time according to the thickness of the aluminum foil, and an energy distribution with high energy at the front and low energy at the back is adopted for the aluminum foil, and the energy adjustment range is 0.5-5J / cm 2 , can reduce the residue at the bottom of the hole and improve the taper. For example, for 50μm aluminum foil, the energy distribution with high front and low back (initial pulse 5J / cm 2 , and subsequently reduced to 2J / cm 2 ), reducing the cone angle from 15° to 8°. During the dynamic polarization state adjustment phase, the rotating wave plate assembly is linked to the online monitoring system to adjust the laser polarization direction based on real-time hole shape feedback, reducing the hole wall roughness Ra from 1.2μm to 0.5μm.

[0019] Preferably, the pulse fiber laser has a wavelength of 1064 nm, a pulse width of 10-100 ns, and a frequency of 10-100 kHz.

[0020] Preferably, in step S3, the pressure waveform is a sawtooth wave or a triangular wave. When applying pressure, the positive pressure is 2 MPa maintained for 5 seconds, and then the negative pressure is 0.5 MPa maintained for 3 seconds. Compared with the square wave, the etching liquid exchange efficiency can be improved by 30%, and the pore expansion rate is increased to 1.5 μm / min (the traditional immersion method is 0.8 μm / min).

[0021] Preferably, in step S3, 0.01-0.1 wt% polyethylene glycol (PEG 4000) is added to the mixed solution to inhibit H + The excessive diffusion of the lateral corrosion rate and the longitudinal corrosion rate ratio is increased from 1:1 to 3:1, ensuring the hole roundness with a roundness error of ≤5%.

[0022] Preferably, in step S4, the anodic oxidation is performed at a voltage of 10 V, with an electrolyte of 5% sulfuric acid, for 30 seconds to generate a dense aluminum oxide layer of 5-10 nm, reducing the surface resistance of the aluminum foil to 15 mΩ / cm 2 (The traditional passivation method is 25mΩ / cm 2 ).

[0023] Preferably, a negative pressure adsorption and centrifugal separation device is used to collect the metal debris generated by laser drilling, and the aluminum chips adsorbed by negative pressure are subjected to eddy current separation to remove impurities in the oxide layer, and then put into an alkaline electrolyte. The alkaline electrolyte is a NaOH electrolyte with a concentration of 2 mol / L and a current density of 200 A / m 2 , recycle high-purity aluminum particles (purity ≥ 99.9%), and increase the material utilization rate to 95%.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) Laser drilling ensures the initial hole position accuracy, and pickling and hole expansion achieve pore size uniformity through pressure regulation, meeting the porosity requirements of T / CESA 1210-2022 for supercapacitor aluminum foil.

[0026] (2) The photoresist coating step is eliminated, reducing the use of organic solvents; the recycling rate of the pickling solution is increased by 30%, reducing costs and being very environmentally friendly.

[0027] (3) It can process aluminum foil with a thickness of 10-300μm, and is compatible with materials such as copper foil and nickel foil, with wide adaptability.

[0028] (4) The sawtooth wave pressure cycle can improve the exchange efficiency of the corrosion liquid and the hole expansion rate compared with the square wave.

[0029] (5) Add polyethylene glycol (PEG 4000) to the AlCl3 solution to inhibit H + The excessive diffusion of corrosion products is reduced, the ratio of lateral corrosion rate to longitudinal corrosion rate is increased, and the roundness of the hole is ensured, with the roundness error ≤ 5%.

[0030] (6) After the aluminum chips adsorbed by negative pressure are eddy-current sorted to remove impurities in the oxide layer, they are put into NaOH alkaline electrolyte to recover high-purity aluminum particles, thereby improving material utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a process flow chart of the present invention; DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] Example 1

[0034] The foil micro-hole processing method based on laser hole drawing and pickling hole expansion includes the following steps:

[0035] S1: Pretreatment of aluminum foil: First, the aluminum foil is annealed at 300°C for 12 hours to eliminate internal stress and improve material uniformity; then it is immersed in 1wt% sodium hydroxide solution at 80°C for 1 minute to remove surface grease.

[0036] S2: Laser drilling: Using a pulsed fiber laser with a wavelength of 1064nm, a pulse width of 30ns, and a frequency of 50kHz, initial micropores are formed on the surface of the aluminum foil with a pore diameter of 5-50μm and a depth of 20-50% of the foil thickness. Combined with galvanometer scanning and a rotating wave plate set, the laser polarization state is adjusted to reduce the heat-affected zone and improve the smoothness of the hole wall.

[0037] In the laser drilling stage, an energy density gradient adjustment module, such as a variable attenuator, is introduced. For 50μm aluminum foil, a high-front-low energy distribution is adopted, and the initial pulse is 5J / cm 2 , and subsequently reduced to 2J / cm 2 , reducing the cone angle from 15° to 8°. During the dynamic polarization state adjustment stage, the rotating wave plate group is linked to the online monitoring system to adjust the laser polarization direction based on real-time hole shape feedback (such as CCD imaging), reducing the hole wall roughness Ra from 1.2μm to 0.5μm.

[0038] S3: Pickling and hole enlargement: First, 10% hydrochloric acid and 1 mol / L AlCl3 buffer solution were mixed at a molar concentration ratio of 1:0.01-0.5 and a temperature of 60°C to complete the preparation of the etching solution; then, a sawtooth wave cycle was used, first with a positive pressure of 2 MPa for 5 seconds, and then a negative pressure of 0.5 MPa for 3 seconds, to apply alternating positive and negative pressures to the etching solution, driving the etching solution through the laser initial hole to form turbulence, accelerate sidewall corrosion, and ultimately expand the pore diameter to 10-100 μm and eliminate burrs; 0.05 wt% polyethylene glycol (PEG 4000) was added to the mixed solution to inhibit H + excessive diffusion.

[0039] S4: Subsequent treatment: First, use 1 mol / L nitric acid solution to clean for 3 minutes at 60°C to remove residual corrosion products on the foil; then use an anodizing step to reduce the surface resistance of the aluminum foil. The anodizing voltage is 10V, the electrolyte is 5% sulfuric acid, and the time is 30s to generate a 5-10nm dense aluminum oxide layer to reduce the surface resistance of the aluminum foil.

[0040] Vacuum drying: adopt segmented vacuum drying, the first stage is 100℃ / 10kPa to remove moisture, the second stage is 250℃ / 0.1kPa to eliminate thermal stress, avoid pore collapse, improve porosity stability, and ensure the stability of pore structure.

[0041] S5: Debris treatment: Use negative pressure adsorption and centrifugal separation device to collect metal debris generated by laser drilling, and remove oxide layer impurities from the aluminum chips adsorbed by negative pressure through eddy current separation, and then put them into NaOH electrolyte with a concentration of 2 mol / L and a current density of 200 A / m 2 , recycle high-purity aluminum particles and improve material utilization.

[0042] Example 2

[0043] The foil micro-hole processing method based on laser hole drawing and pickling hole expansion includes the following steps:

[0044] S1: Pretreatment of aluminum foil: First, the aluminum foil is annealed at 300°C for 12 hours to eliminate internal stress and improve material uniformity; then it is immersed in 1wt% sodium hydroxide solution at 80°C for 1 minute to remove surface grease.

[0045] S2: Laser drilling: Using a pulsed fiber laser with a wavelength of 1064nm, a pulse width of 30ns, and a frequency of 50kHz, initial micropores are formed on the surface of the aluminum foil with a pore diameter of 5-50μm and a depth of 20-50% of the foil thickness. Combined with galvanometer scanning and a rotating wave plate set, the laser polarization state is adjusted to reduce the heat-affected zone and improve the smoothness of the hole wall.

[0046] In the laser drilling stage, an energy density gradient adjustment module, such as a variable attenuator, is introduced. For 50μm aluminum foil, a high-front-low energy distribution is adopted, and the initial pulse is 5J / cm 2 , and subsequently reduced to 2J / cm 2 , reducing the cone angle from 15° to 8°. During the dynamic polarization state adjustment stage, the rotating wave plate group is linked to the online monitoring system to adjust the laser polarization direction based on real-time hole shape feedback (such as CCD imaging), reducing the hole wall roughness Ra from 1.2μm to 0.5μm.

[0047] S3: Pickling and hole enlargement: First, 10% hydrochloric acid and 1 mol / L AlCl3 buffer solution were mixed at a molar concentration ratio of 1:0.01-0.5 and a temperature of 60°C to complete the preparation of the etching solution; then, a triangle wave cycle was used, first with a positive pressure of 2MPa for 5s, then a negative pressure of 0.5MPa for 3s, to apply alternating positive and negative pressures to the etching solution, driving the etching solution through the laser initial hole to form turbulence, accelerate sidewall corrosion, and ultimately expand the pore diameter to 10-100μm and eliminate burrs; 0.1wt% polyethylene glycol (PEG 4000) was added to the mixed solution to inhibit H + excessive diffusion.

[0048] S4: Subsequent treatment: First, use 1 mol / L nitric acid solution to clean for 3 minutes at 60°C to remove residual corrosion products on the foil; then use an anodizing step to reduce the surface resistance of the aluminum foil. The anodizing voltage is 10V, the electrolyte is 5% sulfuric acid, and the time is 30s to generate a 5-10nm dense aluminum oxide layer to reduce the surface resistance of the aluminum foil.

[0049] Vacuum drying: adopt segmented vacuum drying, the first stage is 100℃ / 10kPa to remove moisture, the second stage is 250℃ / 0.1kPa to eliminate thermal stress, avoid pore collapse, improve porosity stability, and ensure the stability of pore structure.

[0050] S5: Debris treatment: Use negative pressure adsorption and centrifugal separation device to collect metal debris generated by laser drilling, and remove oxide layer impurities from the aluminum chips adsorbed by negative pressure through eddy current separation, and then put them into NaOH electrolyte with a concentration of 2 mol / L and a current density of 200 A / m 2 , recycle high-purity aluminum particles and improve material utilization.

[0051] Example 3

[0052] The foil micro-hole processing method based on laser hole drawing and pickling hole expansion includes the following steps:

[0053] S1: Pretreatment of aluminum foil: First, the aluminum foil is annealed at 300°C for 12 hours to eliminate internal stress and improve material uniformity; then it is immersed in 0.1wt% sodium hydroxide solution at 80°C for 1 minute to remove surface grease.

[0054] S2: Laser drilling: Using a pulsed fiber laser with a wavelength of 1064nm, a pulse width of 30ns, and a frequency of 50kHz, initial micropores are formed on the surface of the aluminum foil with a pore diameter of 5-50μm and a depth of 20-50% of the foil thickness. Combined with galvanometer scanning and a rotating wave plate set, the laser polarization state is adjusted to reduce the heat-affected zone and improve the smoothness of the hole wall.

[0055] In the laser drilling stage, an energy density gradient adjustment module, such as a variable attenuator, is introduced. For 50μm aluminum foil, a high-front-low energy distribution is adopted, and the initial pulse is 5J / cm 2 , and subsequently reduced to 2J / cm 2 , reducing the cone angle from 15° to 8°. During the dynamic polarization state adjustment stage, the rotating wave plate group is linked to the online monitoring system to adjust the laser polarization direction based on real-time hole shape feedback (such as CCD imaging), reducing the hole wall roughness Ra from 1.2μm to 0.5μm.

[0056] S3: Pickling and hole enlargement: First, 10% hydrochloric acid and 1 mol / L AlCl3 buffer solution were mixed at a molar concentration ratio of 1:0.01-0.5 and a temperature of 60°C to complete the preparation of the etching solution; then, a sawtooth wave cycle was used, first with a positive pressure of 2 MPa for 5 seconds, and then a negative pressure of 0.5 MPa for 3 seconds, to apply alternating positive and negative pressures to the etching solution, driving the etching solution through the laser initial hole to form turbulence, accelerate sidewall corrosion, and ultimately expand the pore diameter to 10-100 μm and eliminate burrs; 0.2 wt% polyethylene glycol (PEG 4000) was added to the mixed solution to inhibit H + excessive diffusion.

[0057] S4: Subsequent treatment: First, use 1 mol / L nitric acid solution to clean for 3 minutes at 60°C to remove residual corrosion products on the foil; then use an anodizing step to reduce the surface resistance of the aluminum foil. The anodizing voltage is 10V, the electrolyte is 5% sulfuric acid, and the time is 30s to generate a 5-10nm dense aluminum oxide layer to reduce the surface resistance of the aluminum foil.

[0058] Vacuum drying: adopt segmented vacuum drying, the first stage is 100℃ / 10kPa to remove moisture, the second stage is 250℃ / 0.1kPa to eliminate thermal stress, avoid pore collapse, improve porosity stability, and ensure the stability of pore structure.

[0059] S5: Debris treatment: Use negative pressure adsorption and centrifugal separation device to collect metal debris generated by laser drilling, and remove oxide layer impurities from the aluminum chips adsorbed by negative pressure through eddy current separation, and then put them into NaOH electrolyte with a concentration of 2 mol / L and a current density of 200 A / m 2 , recycle high-purity aluminum particles and improve material utilization.

[0060] The data of the aluminum foils produced by the above embodiments are compared as follows:

[0061] Table 1: Effect of laser parameters on initial hole quality (aluminum foil thickness 50μm)

[0062]

[0063] Conclusion: At 3.5J / cm 2 , 30ns, 50kHz parameters, energy gradient control (initial pulse 5J / cm 2 , and subsequently reduced to 2J / cm 2 ) Combined with a 30ns pulse width, the cone angle is reduced to 8.1° and the residue is reduced by 68%, meeting the requirements of high-precision hole insertion.

[0064] Table 2: Effect of pressure waveform on hole expansion rate

[0065] Pressure waveform Hole expansion rate (μm / min) Pore ​​size uniformity (%) Square wave pressure (0.1-5MPa alternating) 0.8 8.2 Sawtooth wave pressure (2MPa↘0.5MPa) 1.5 4.1 Triangular wave pressure (0.1↗5↘0.1MPa) 1.2 5.3

[0066] Data source: The flow state of the etching solution was recorded by a high-speed camera (Phantom VEO 410L), and the pore size changes were analyzed using ImageJ software.

[0067] Table 3: Effect of PEG additives on corrosion selectivity

[0068]

[0069] Conclusion: 0.1wt% PEG 4000 makes the lateral / longitudinal corrosion rate ratio reach 3:1, the roundness error is ≤5%, and the hole shape is significantly improved.

[0070] Table 4: Effect of passivation process on the conductivity of aluminum foil

[0071]

[0072] Test standard: Surface resistivity is measured using the four-probe method (GB / T 1551-2021). Salt spray test is performed according to ASTM B117.

[0073] Table 5: Comparison of key indicators of supercapacitor aluminum foil

[0074]

[0075] Test method: Pore size distribution is determined by gas adsorption method (BET), and the cycle life test condition is 1 mA / cm 2 Constant current charge and discharge.

[0076] It should be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not preclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0077] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A foil micro-hole processing method based on laser hole drawing and pickling hole expansion is characterized by: The following steps are involved: S1: Pretreatment of aluminum foil Annealing treatment: Aluminum foil is annealed at 200-600℃ for 10min-24h to eliminate internal stress and improve material uniformity; Degreasing and cleaning: Use 0.01-4wt% sodium hydroxide solution, temperature 0-100℃, soak for 10s-1min to remove surface grease; S2: Laser drilling A pulsed fiber laser is used to form initial micropores on the surface of the aluminum foil, with a pore diameter of 5-50μm and a depth of 20-50% of the foil thickness. A combination of galvanometer scanning and a rotating wave plate set is used to adjust the laser polarization state, reduce the heat-affected zone, and improve the smoothness of the pore wall. S3: Pickling and reaming Preparation of etching solution: Mix 10% hydrochloric acid with 0.0001-2 mol / L AlCl3 buffer solution, with a molar concentration ratio of 1:0.01-0.5, and the temperature is 30-60℃; Dynamic pressure expansion: Using pressure wave circulation, alternating positive and negative pressures are applied to the etching liquid in the range of 0.1-5MPa, driving the etching liquid through the laser initial hole to form turbulence, accelerating the sidewall corrosion, and ultimately expanding the hole diameter to 10-100μm and eliminating burrs; S4: Subsequent processing Cleaning and passivation: Use 0.02-2 mol / L nitric acid solution at 5-90°C for 1-3 minutes to remove residual corrosion products; after nitric acid cleaning, perform an anodizing step to reduce the surface resistance of the aluminum foil. Vacuum drying: Use segmented vacuum drying to avoid pore collapse, improve porosity stability, and ensure stable pore structure.

2. The foil micro-hole processing method based on laser hole drawing and pickling hole expansion according to claim 1 is characterized in that: In step S2, an energy density gradient adjustment module is introduced during the laser drilling stage to adjust the pulse energy in real time according to the thickness of the aluminum foil. The energy adjustment range is 0.5-5J / cm 2 , so as to adopt a high-front-low-back energy distribution for the aluminum foil; in the dynamic adjustment stage of the polarization state, the wave plate group is rotated in conjunction with the online monitoring system to adjust the laser polarization direction according to the real-time hole shape feedback, so that the hole wall roughness Ra is reduced from 1.2μm to 0.5μm.

3. The foil micro-hole processing method based on laser hole drawing and pickling hole expansion according to claim 2 is characterized in that: The pulse fiber laser has a wavelength of 1064 nm, a pulse width of 10-100 ns, and a frequency of 10-100 kHz.

4. The foil micro-hole processing method based on laser hole drawing and pickling hole expansion according to claim 3 is characterized in that: In step S3, the pressure waveform is a sawtooth wave or a triangle wave. When applying pressure, the positive pressure is 2 MPa and maintained for 5 seconds, and then the negative pressure is 0.5 MPa and maintained for 3 seconds.

5. The foil micro-hole processing method based on laser hole drawing and pickling hole expansion according to claim 4 is characterized in that: In step S3, 0.01-0.1 wt% polyethylene glycol is added to the mixed solution prepared from the corrosive solution to inhibit H + The excessive diffusion of the lateral corrosion rate increases the ratio of the lateral corrosion rate to the longitudinal corrosion rate from 1:1 to 3:1, ensuring the roundness of the hole.

6. The foil micro-hole processing method based on laser hole drawing and pickling hole expansion according to claim 5 is characterized in that: In step S4, the anodic oxidation is performed at a voltage of 10 V, with an electrolyte of 5% sulfuric acid, for 30 seconds to generate a dense aluminum oxide layer of 5-10 nm, thereby reducing the surface resistance of the aluminum foil.

7. The foil micro-hole processing method based on laser hole drawing and pickling hole expansion according to claim 6, characterized in that: A negative pressure adsorption and centrifugal separation device is used to collect metal debris generated by laser drilling. The aluminum chips adsorbed by negative pressure are then subjected to eddy current separation to remove impurities in the oxide layer and then put into alkaline electrolyte to recover high-purity aluminum particles.

8. The foil micro-hole processing method based on laser hole drawing and pickling hole expansion according to claim 7, characterized in that: The alkaline electrolyte is NaOH electrolyte with a concentration of 2 mol / L and a current density of 200 A / m 2 .

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