Laser cladding technology for sideline repair

Abstract

The invention discloses a laser cladding technology for sideline repair, which comprises the following steps: S1, positioning a broken position of a sideline under a microscope, and making a positioning mark within a 5mm range of a defect area by using a laser marking machine; s2, a metal mold matched with the curvature of the surface of the base material is manufactured; s3, aligning the center line of the opening of the mold with the broken position of the side line through a microscopic vision system; s4, under the protection of inert gas, a coaxial powder feeding device is adopted for conveying metal powder to the opening area of the mold, and rectangular spot laser is used for conducting multi-channel lap-joint cladding; s5, after the mold is removed, electrolytic polishing is conducted on the repairing area, and the conductivity and insulativity of the repairing circuit are tested; compared with a traditional conductive silver paste coating or electrochemical deposition method, the laser cladding technology provided by the invention does not need a complex mask process, the repair efficiency is improved, and meanwhile, secondary damage to the brittle transparent substrate caused by contact type operation is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of microfabrication, and specifically to a laser cladding technology for edge repair. Background Art

[0002] With the rapid development of flexible display and touch technology, metal mesh has become one of the mainstream technologies in the field of transparent conductive films due to its high conductivity, excellent mechanical stability and good light transmittance. Especially in the application of ultra-large size and high-precision touch screens, the metal mesh can achieve micron-level line width control through the yellow light subtraction process to meet the high-resolution requirements. However, this process is vulnerable to environmental foreign matters such as dust and glue residues during processes such as film pressing and exposure, resulting in local fracture of the metal mesh edge line, seriously restricting the improvement of product yield.

[0003] Traditional repair methods such as conductive silver paste coating or electrochemical deposition can achieve circuit repair, but have obvious limitations: the bonding force between the conductive silver paste and the metal mesh interface is weak after curing and is easy to fall off during long-term use; electrochemical deposition requires a complex masking process, with low repair efficiency and easy to cause short circuits between adjacent circuits. In addition, both methods require contact operation, causing secondary damage to brittle transparent substrates such as PET and CPI. Laser welding technology has been tried for metal circuit repair, but the conventional laser heat input is too high, easily causing thermal deformation of the substrate or excessive ablation of the metal layer, and it is difficult to meet the high-precision repair requirements. Summary of the Invention

[0004] The purpose of the present invention is to provide a laser cladding technology for edge repair to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solution: a laser cladding technology for edge repair, the method comprising the following steps:

[0006] S1: Defect location: Locate the edge break position under a microscope with a magnification of 50 - 200 times, and use a laser marking machine to make a positioning mark within a range of 5 mm from the defect area;

[0007] S2: Mold preparation: Fabricate a metal mold that matches the surface curvature of the substrate. The mold opening width W = W0 + (10 - 20 μm), where W0 is the standard width of the edge line, and the opening length completely covers the notch and extends 1 - 5 mm at both ends;

[0008] S3: Precision positioning: Align the center line of the mold opening with the edge break position through a microscopic vision system;

[0009] S4: Laser cladding: Under the protection of an inert gas, use a coaxial powder feeding device to transport metal powder to the mold opening area, and use a rectangular spot laser for multi-pass overlapping cladding;

[0010] S5: Post-treatment: After removing the mold, electro-polish the repaired area and test the conductivity and insulation of the repaired circuit.

[0011] Preferably, the mold is made of invar alloy, with a thickness of 0.1 - 2 mm. A thermal conductive adhesive layer with a thickness of 0.05 - 0.1 mm is provided on the bottom surface of the mold, and the opening side wall is designed with a flaring angle of 5 - 15°.

[0012] Preferably, the laser power density is 15 - 25 kw / cm 2 , the scanning speed is 200 - 500 mm / min, the overlapping rate is 30 - 50%, and the aspect ratio of the light spot is 3:1 to 5:1.

[0013] Preferably, the metal powder is spherical copper alloy powder, with a particle size of 75 - 150 μm, and the composition includes 0.5 - 1.2 wt% of Ag and 0.05 - 0.2 wt% of rare earth elements.

[0014] Preferably, the main protective gas of the inert gas is argon, with a flow rate of 15 - 25 L / min, and the auxiliary protective gas is an argon-hydrogen mixture containing 2 - 5% of hydrogen, with a flow rate of 5 - 10 L / min.

[0015] Preferably, the multi-pass overlapping cladding includes a first transition layer, a main body layer, and a surface modification layer. The first transition layer uses copper-tin alloy powder with a particle size of 50 - 100 μm and a laser power of 2 - 2.5 kw; the main body layer uses copper-silver alloy powder with a particle size of 100 - 200 μm and a laser power of 3 - 4 kw; the surface modification layer uses pure copper powder with a particle size less than 50 μm and a laser power of 1 - 1.5 kw.

[0016] Preferably, the repaired area is subjected to surface texturing treatment with femtosecond laser to form a micro-groove array with a width of 20 - 50 μm and a depth of 5 - 15 μm.

[0017] Preferably, the temperature of the electrolyte for electro-polishing is 23 - 27 °C, the voltage is 3 - 5 V, the current density is 0.5 - 1.2 A / cm 2 , and the treatment time is 30 - 60 s.

[0018] Preferably, the conductivity test includes measuring the resistance ratios R1 / R0 and R2 / R0 of the repaired circuit to two adjacent original circuits, where R0 is the designed resistance value, and it satisfies |R1 - R0| / R0 ≤ 3% and |R2 - R0| / R0 ≤ 3%.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. The present invention realizes high-precision defect positioning by using an ultraviolet picosecond laser marking machine and matching with a three-dimensional substrate curvature model, avoids the deficiencies of traditional visual positioning, reduces repair deviation, thereby avoiding secondary damage to the brittle substrate. The mold matches the surface curvature of the substrate, and micro-EDM machining and elastic nickel-titanium alloy sheets are adopted to ensure the precise definition of the cladding area, reduce the flow resistance of the molten pool and the accumulation of metal powder, and improve the repair quality.

[0021] 2. The present invention realizes high-precision alignment of the mold and the fracture by adopting a double-CCD camera mechanism and a piezoelectric ceramic micro-motion platform, effectively preventing the risks of cladding vibration deviation and short circuit between adjacent circuits. The use of a rectangular spot laser and a coaxial powder feeding device, combined with optimized laser power density, scanning speed and overlap rate, realizes uniform heat distribution and reduces thermal stress concentration, avoiding substrate deformation and excessive ablation of the metal layer.

[0022] 3. The present invention enhances the wettability with the substrate, inhibits grain boundary oxidation, and reduces the surface roughness by designing multi-pass overlapping cladding of metal powders with different compositions and particle sizes, including a transition layer, a main body layer and a surface modification layer, realizes high-precision metallurgical bonding. Through femtosecond laser surface texturing treatment and electrolytic polishing, the anti-electrochemical migration ability of the repair area is improved, the surface roughness is reduced, and the conductivity and insulation of the repaired circuit are ensured to meet high-precision requirements. Description of the Drawings

[0023] Figure 1 is a flow chart of the laser cladding technology for edge repair of the present invention.

[0024] Figure 2 is a schematic structural diagram of the multi-pass overlapping cladding of the present invention. Detailed Embodiments

[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] Please refer to Figures 1 to 2 , the present invention provides a technical solution: a laser cladding technology for edge repair, and the method includes the following steps:

[0027] S1: Defect Location: Locate the position where the edge is disconnected under a microscope with a magnification of 50 - 200 times. Use an ultraviolet picosecond laser marking machine with a wavelength of 355 nm and a pulse width of 10 ps to etch a cross - positioning mark 3 mm away from the edge of the fracture to avoid the spread of the heat - affected zone. Match the positioning coordinates with the three - dimensional substrate curvature model to generate a repair path planning file, solving the problem of repair deviation caused by insufficient positioning accuracy of the traditional naked - eye method and avoiding secondary damage to the brittle substrate.

[0028] S2: Mold Preparation: Make a metal mold that matches the surface curvature of the substrate. The opening width W of the mold is W = W0+(10 - 20 μm), where W0 is the standard width of the edge. The opening length completely covers the notch and extends 1 - 5 mm at both ends.

[0029] The mold is made of invar alloy with a thickness of 0.1 - 2 mm. The mold is processed by micro - electro - discharge machining. There is a silicon - based thermal conductive adhesive filled with nano - silver particles with a thickness of 0.05 - 0.1 mm on the bottom surface of the mold. The side wall of the opening is designed with a flare angle of 5 - 15° to reduce the flow resistance of the molten pool and prevent the accumulation of metal powder.

[0030] Obtain the three - dimensional topography of the substrate through laser scanning. The bottom surface of the mold uses an elastic nickel - titanium alloy sheet to adaptively fit the curved substrate, overcoming the problems of low accuracy and uneven heat conduction in the traditional masking process and ensuring the precise limitation of the cladding area.

[0031] S3: Precision Positioning: Use a binocular CCD camera to establish a stereo vision to capture the spatial position of the mold and the fracture in real - time. Integrate a piezoelectric ceramic micro - motion platform to adjust the position of the mold according to the visual feedback to ensure that the center - line alignment error ≤ 3 μm. There is a micro - hole array on the back of the mold, and it is fixed on the surface of the substrate through negative - pressure adsorption to prevent vibration deviation during cladding, thus eliminating the traditional mechanical alignment error and avoiding short - circuit between adjacent circuits caused by cladding deviation.

[0032] S4: Laser Cladding: Under the protection of inert gas, use a coaxial powder - feeding device to transport metal powder to the opening area of the mold, and use a rectangular - spot laser for multi - pass overlapping cladding.

[0033] The rectangular spot has a major axis of 5 mm × a minor axis of 1 mm, with an energy gradient distribution, and the edge power density is reduced by 15% to reduce thermal stress concentration.

[0034] The laser power density is 15 - 25 kw / cm 2 , the scanning speed is 200 - 500 mm / min, the overlapping rate is 30 - 50%, and the aspect ratio of the spot is 3:1 to 5:1.

[0035] The main protective gas of the inert gas is argon, with a flow rate of 15 - 25 L / min. The auxiliary protective gas is an argon-hydrogen mixture containing 2 - 5% hydrogen, with a flow rate of 5 - 10 L / min. The main argon gas flow forms a laminar flow barrier, and the argon-hydrogen mixture is used to blow the molten pool directionally to reduce CuO to Cu.

[0036] The metal powder is spherical copper alloy powder, with a particle size of 75 - 150 μm, and the composition includes 0.5 - 1.2 wt% Ag and 0.05 - 0.2 wt% rare earth elements.

[0037] The multi-pass overlapping cladding includes a first transition layer, a main body layer, and a surface modification layer. The first transition layer uses copper-tin alloy powder with a particle size of 50 - 100 μm and a laser power of 2 - 2.5 kw to enhance the wettability with the substrate; the main body layer uses copper-silver alloy powder with a particle size of 100 - 200 μm and a laser power of 3 - 4 kw to inhibit grain boundary oxidation; the surface modification layer uses pure copper powder with a particle size less than 50 μm and a laser power of 1 - 1.5 kw. After laser remelting, the surface roughness is reduced.

[0038] Step S4 solves the substrate deformation caused by too high heat input in traditional laser welding and realizes high-precision metallurgical bonding.

[0039] S5: Post-treatment: After removing the mold, electro-polish the repaired area and test the conductivity and insulation of the repaired circuit.

[0040] The repaired area is subjected to surface texturing treatment with femtosecond laser to form a micro-groove array with a width of 20 - 50 μm and a depth of 5 - 15 μm. A 2-μm-thick Ni-P layer is electroplated in the grooves to improve the anti-electrochemical migration ability.

[0041] The electrolyte formula uses 65 vol% phosphoric acid, 25 vol% ethanol, 10 g / L sodium dodecyl sulfate, and the pH value is 1.5.

[0042] The temperature of the electrolyte for electro-polishing is 23 - 27 °C, the voltage is 3 - 5 V, and the current density control: in the initial stage, it is 1.2 A / cm 2 , to remove the oxide layer; in the later stage, it is reduced to 0.6 A / cm 2 , for mirror polishing. The surface roughness is reduced from 1.2 μm to 0.3 μm, and the treatment time is 30 - 60 s.

[0043] The conductivity test includes measuring the resistance ratios R1 / R0 and R2 / R0 of the repaired circuit to the two adjacent original circuits, where R0 is the designed resistance value, satisfying |R1 - R0| / R0 ≤ 3% and |R2 - R0| / R0 ≤ 3%. The four-probe method is used to measure the sheet resistance of the repaired area, and a 10-mA current is applied simultaneously to detect the insulation resistance between adjacent circuits.

[0044] In summary, by using an ultraviolet picosecond laser marking machine and matching with a three-dimensional substrate curvature model, the present invention achieves high-precision defect positioning, avoids the deficiencies of traditional naked-eye positioning, reduces repair deviation, and thus avoids secondary damage to the brittle substrate; the mold matches the surface curvature of the substrate, and micro-EDM and elastic nickel-titanium alloy sheets are used to ensure the precise definition of the cladding area, reduce the flow resistance of the molten pool and the accumulation of metal powder, and improve the repair quality; a dual-CCD camera and a piezoelectric ceramic micro-motion platform are used to achieve high-precision alignment of the mold and the fracture, effectively preventing the risks of cladding vibration deviation and short circuit between adjacent circuits; the use of a rectangular spot laser and a coaxial powder feeding device, combined with optimized laser power density, scanning speed, and overlapping rate, achieves uniform heat distribution and reduces thermal stress concentration, avoiding substrate deformation and excessive ablation of the metal layer;

[0045] By designing multi-pass overlapping cladding of metal powders with different compositions and particle sizes, including a transition layer, a main layer, and a surface modification layer, the wettability with the substrate is enhanced, grain boundary oxidation is inhibited, and the surface roughness is reduced, achieving high-precision metallurgical bonding; through femtosecond laser surface texturing treatment and electrolytic polishing, the anti-electrochemical migration ability of the repair area is improved, the surface roughness is reduced, and the electrical conductivity and insulation of the repaired circuit are ensured to meet high-precision requirements; compared with traditional conductive silver paste coating or electrochemical deposition methods, the laser cladding technology provided by the present invention does not require a complex mask process, improves the repair efficiency, and at the same time reduces secondary damage to the brittle transparent substrate caused by contact operation.

[0046] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A laser cladding technology for edge line repair, characterized in that: The method includes the following steps: S1: Defect location: Locate the position where the edge line is disconnected under a microscope with a magnification of 50 - 200 times, and use a laser marking machine to make a positioning mark within a range of 5 mm from the defect area; S2: Mold preparation: Fabricate a metal mold that matches the surface curvature of the substrate. The width W of the mold opening is W = W0 + (10 - 20 μm), where W0 is the standard width of the edge line, and the opening length completely covers the notch and extends 1 - 5 mm at both ends; S3: Precision positioning: Align the center line of the mold opening with the position where the edge line is disconnected through a microscopic vision system; S4: Laser cladding: Under the protection of an inert gas, use a coaxial powder feeding device to transport metal powder to the mold opening area, and perform multi-pass overlapping cladding with a rectangular spot laser; S5: Post-treatment: After removing the mold, electro-polish the repaired area, and test the conductivity and insulation of the repaired circuit.

2. The laser cladding technology for edge line repair according to claim 1, wherein: The mold is made of invar alloy, with a thickness of 0.1 - 2 mm. A thermal conductive adhesive layer with a thickness of 0.05 - 0.1 mm is provided on the bottom surface of the mold, and the opening side wall is designed with a flaring angle of 5 - 15°; 3. A laser cladding technology for edge line repair according to claim 1, characterized in that: The laser power density is 15 - 25 kw / cm 2 , the scanning speed is 200 - 500 mm / min, the overlapping rate is 30 - 50%, and the aspect ratio of the light spot is 3:1 to 5:

1.

4. A laser cladding technology for edge line repair according to claim 1, characterized in that: The metal powder is spherical copper alloy powder with a particle size of 75 - 150 μm, and the composition includes 0.5 - 1.2 wt% of Ag and 0.05 - 0.2 wt% of rare earth elements; 5. A laser cladding technology for edge line repair according to claim 1, characterized in that: The main protective gas of the inert gas is argon, with a flow rate of 15 - 25 L / min, and the auxiliary protective gas is an argon-hydrogen mixture containing 2 - 5% hydrogen, with a flow rate of 5 - 10 L / min; 6. A laser cladding technology for edge line repair according to claim 1, characterized in that: The multi-pass overlapping cladding includes a first transition layer, a main body layer, and a surface modification layer. The first transition layer uses copper-tin alloy powder with a particle size of 50 - 100 μm and a laser power of 2 - 2.5 kw; the main body layer uses copper-silver alloy powder with a particle size of 100 - 200 μm and a laser power of 3 - 4 kw; the surface modification layer uses pure copper powder with a particle size less than 50 μm and a laser power of 1 - 1.5 kw; 7. A laser cladding technology for edge line repair according to claim 1, characterized in that: The repaired area is subjected to surface texturing treatment with femtosecond laser to form a micro-groove array with a width of 20 - 50 μm and a depth of 5 - 15 μm; 8. A laser cladding technology for edge line repair according to claim 1, characterized in that: The temperature of the electrolyte for electrolytic polishing is 23-27 °C, the voltage is 3-5 V, and the current density is 0.5-1.2 A / cm 2 , and the treatment time is 30-60 s.

9. A laser cladding technology for edge line repair according to claim 1, characterized in that: The conductivity test includes measuring the resistance ratios R1 / R0 and R2 / R0 of the repaired circuit to two adjacent original circuits, where R0 is the designed resistance value, and it satisfies |R1 - R0| / R0 ≤ 3% and |R2 - R0| / R0 ≤ 3%;

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