Method for repairing open circuit defect of PCB (Printed Circuit Board) circuit

Abstract

According to the method for repairing the open circuit defect of the PCB circuit, the temperature of the PCB is controlled to be 50-100 DEG C, and deformation of an FR-4 base material is avoided; local heating can be achieved through laser parameter adjustment, and peripheral circuits are not affected; aOI detection, pattern design, powder spraying, laser sintering and vacuum suction removal are automatic in the whole process, personal errors are reduced, and the batch production efficiency is improved; dense lines of more than 25 microns and copper surface defects can be repaired, and the problem that dense lines or small-size lines cannot be repaired in the prior art is solved; metal powder is adopted to replace expensive conductive silver paste, the whole process is automatic, no labor cost exists, the comprehensive cost is obviously lower than that of an existing scheme, no short circuit or open circuit phenomenon exists, a sintered circuit is tightly combined with an original circuit, the long-term stability is good, and the method is suitable for being applied to repairing of PCB circuit open circuit defects on a large scale.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing technology, and in particular to a method for repairing open circuit defects in PCB circuits. Background Technology

[0002] A PCB (Printed Circuit Board) is a carrier of electronic components and an essential part of electronic and electrical equipment. During PCB manufacturing, open circuits can occur due to developing or etching processes. To avoid scrapping due to these defects, repairs are necessary. Currently, the most common repair method is manual repair using a wire-repairing machine: the hot-pressing module of the machine presses a solder-copper wire onto one end of the circuit to be repaired. After heating to a certain temperature, the solder-copper wire is soldered to the copper trace. The same process is then repeated to solder the other end of the solder-copper wire to the other end of the circuit to be repaired, creating a circuit. However, this method suffers from poor adhesion between the solder-copper wire and the substrate, often requiring the application of adhesive under the solder-copper wire. Furthermore, due to the limited width of the solder-copper wire and manual operation, areas with densely packed circuits cannot be repaired.

[0003] To address the above issues, patent application 201510143792 proposed a method for repairing lines by applying conductive silver paste to the open circuit, baking it, and then electroplating a layer of copper on the repair area. Although this solves the problems of bonding strength and repairing large areas of copper surface, the process is relatively cumbersome and cannot repair dense lines. Patent application 202111365194 solves the problem of repairing dense lines through steps such as film coating, laser grooving, conductive paste filling, heat curing, and film removal, but the process is complex, costly, and has poor feasibility. Summary of the Invention

[0004] To address the technical problems existing in the prior art, the present invention provides the following technical solution:

[0005] A method for repairing open-circuit defects in PCB circuits, the method comprising:

[0006] (1) Detect the PCB surface circuitry using automated optical inspection equipment to identify the location of open circuit defects;

[0007] (2) Perform image processing on the location of the open circuit defect and compare it with the circuit design draft to generate a repair graphic;

[0008] (3) Spray metal powder in and around the open circuit defect area;

[0009] (4) The metal powder is sintered by laser to form a conductive circuit;

[0010] (5) Remove unsintered metal powder.

[0011] Preferably, in step (1), the resolution of the automatic optical inspection device is 25 μm / pixel, the scanning speed is 0.5 m² / min, the circuit image is acquired by illuminating with a ring LED light source, and the open circuit defect is identified by a grayscale comparison algorithm.

[0012] Preferably, in step (2), the image processing includes grayscale conversion, Gaussian filtering, histogram equalization and edge detection, and the defect image is compared with the circuit design draft by using the SIFT feature point matching algorithm to automatically generate the repair graphic.

[0013] Preferably, in step (2), generating the repair pattern includes designing an overlap length on the copper surfaces at both ends of the open circuit, wherein the overlap length is 0.1-10mm and the overlap width is less than or equal to the original line width.

[0014] Preferably, in step (3), the particle size of the metal powder is 1-50 μm, the sphericity is ≥90%, the loose density is ≥4.5 g / cm³, the flowability is ≤30 s / 50 g, and the powder layer thickness is 1-100 μm.

[0015] Preferably, in step (3), a pneumatic powder spraying device is used when spraying metal powder, with a spraying pressure of 0.1-0.5MPa and a nozzle moving speed of 50-100mm / s.

[0016] Preferably, in step (4), the laser sintering uses a fiber laser with a wavelength of 1064nm, an output power of 10-50W, a spot diameter of 10-50μm, a scanning speed of 100-500mm / s, and a pulse frequency of 10-50kHz.

[0017] Preferably, in step (4), the PCB board temperature is controlled at 50-100℃ during laser sintering, and the resistivity of the sintered circuit is ≤1.5× Ω·m, with a resistivity difference of ≤10% from the original circuit.

[0018] Preferably, in step (5), the removal of unsintered metal powder is carried out by vacuum suction, with a vacuum degree of -0.08 to -0.1 MPa, a nozzle diameter of 2-5 mm, and a nozzle moving speed of 50-100 mm / s. After suction, compressed air is used to blow the PCB surface.

[0019] Preferably, the metal powder is selected from at least one of bronze alloy, stainless steel, nickel-aluminum alloy, cobalt-chromium alloy, and titanium alloy.

[0020] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0021] The repair method of the present invention has significant advantages over the prior art:

[0022] 1. Superior performance: resistivity difference ≤10%, adhesion ≥1.5N / mm², accuracy ±2-3μm, far superior to the performance of manual thread repair machine (Comparative Example 1);

[0023] 2. Higher efficiency: The repair time is only 10-12 seconds per piece, which is 5-6 times that of manual wire repair machines and about 4 times that of conductive silver paste method;

[0024] 3. Wider applicability: It can repair dense lines and copper surface defects larger than 25μm, solving the problem that existing technologies cannot repair dense lines or small-sized lines;

[0025] 4. Lower cost: It uses metal powder instead of expensive conductive silver paste, and the whole process is automated with no labor costs, resulting in a significantly lower overall cost than existing solutions;

[0026] 5. Enhanced reliability: No short circuits or open circuits occur. The sintered circuits are tightly bonded to the original circuits, exhibiting good long-term stability and making it suitable for large-scale application in repairing open circuit defects in PCB circuits. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart of a method for repairing open circuit defects in PCB circuits provided by an embodiment of the present invention. Detailed Implementation

[0029] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0030] In embodiments of the present invention, terms such as "for example" and "e.g." are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "for example" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the term "for example" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0031] In the embodiments of this invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that, without emphasizing the distinction between them, they convey the same meaning. Similarly, the terms "of," "corresponding (relevant)," and "corresponding" may sometimes be used interchangeably. It should be noted that, without emphasizing the distinction between them, they convey the same meaning.

[0032] In this embodiment of the invention, sometimes a subscript such as W1 may be mistakenly written as a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0033] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0034] This invention provides a method for repairing open-circuit defects in PCB circuits. The method includes:

[0035] (1) Detect the PCB surface circuitry using automated optical inspection equipment to identify the location of open circuit defects;

[0036] (2) Perform image processing on the location of the open circuit defect and compare it with the circuit design draft to generate a repair graphic;

[0037] (3) Spray metal powder in and around the open circuit defect area;

[0038] (4) The metal powder is sintered by laser to form a conductive circuit;

[0039] (5) Remove unsintered metal powder.

[0040] The specific implementation steps of each of the above steps will be described in detail below with reference to the embodiments.

[0041] like Figure 1 The diagram shows a repair route for open circuit defects in PCB circuits. This invention provides a method for repairing open circuit defects in PCB circuits, which can repair dense circuits and significantly improves repair efficiency compared to manual repair.

[0042] To achieve the above objectives, the present invention provides a method for repairing open circuit defects in PCB circuit boards, comprising the following steps:

[0043] 1. AOI inspection of PCB surface traces

[0044] An automated optical inspection system with a CCD sensor of 25 μm / pixel resolution was used to scan the PCB surface at a speed of 0.5 m² / min. Circuit images were acquired by illumination from a ring-shaped LED light source (wavelength 550 nm), and open-circuit defects were identified using a grayscale contrast algorithm.

[0045] By calculating the grayscale difference between adjacent pixels, an open circuit is identified when the difference exceeds a preset threshold (20-50 grayscale values). During implementation, a 3x3 sliding window is used to traverse the image, counting the number of grayscale variation points within the window. For example, if the window pixel grayscale values ​​are [[100,102,98],[105,50,103],[99,101,104]], and there are 6 variation points for the grayscale difference between adjacent pixels (e.g., the difference between the center 50 and the upper 102 is 52>30, and the difference between the center 50 and the right 103 is 53>30, etc.), then if more than 5 are found, the area is marked as a defect, achieving a positioning accuracy of ±5μm. Simultaneously, a 12-megapixel CCD camera is activated to photograph the defect location from a vertical top-down angle, with an exposure time controlled between 10-20ms to ensure clear visibility of defect details.

[0046] 2. Computer graphics processing and repair design:

[0047] Preprocessing of the captured defective images: Grayscale conversion is performed using the formula Y=0.299R+0.587G+0.114B to convert the RGB image into a single-channel grayscale image. For example, for RGB values ​​(R=255, G=200, B=150), the calculated Y=0.299×255+0.587×200+0.114×150=76.245+117.4+17.1=210.745≈211. Gaussian filtering is performed using a 5x5 convolution kernel (σ=1.4), with kernel weights such as [[0.003,0.013,0.022,0.013,0.003],[0.013,0.059,0.097,0.059,0.013],[0.022,0.097,0.003],[0.003, ...97],[0.003,0.013,0.059,0.097],[0.003,0.013,0.059,0.097],[0.003,0.013],[0.003,0.013,0.013],[0.003,0.013,0.013],[0.003,0.013,0.013],[0.003,0.013],[0.003,0.013],[0.003,0 [0.159,0.097,0.022],[0.013,0.059,0.097,0.059,0.013],[0.003,0.013,0.022,0.013,0.003]], filtering the gray values ​​of the neighborhood of the pixel [[90,92,95,93,91],[91,93,96,94,92],[92,94,100,95,93],[91,93,95,94,92],[90,92,94,93,91]], the filtered value is approximately 94.5; histogram equalization, for example: the original image pixel gray-level cumulative distribution function CDF(100)=0.3, the adjusted pixel value = CDF(100)×255≈76;

[0048] Defect contours are extracted using the Canny edge detection algorithm: a dual threshold (low threshold 50, high threshold 150) is used. For example, a pixel gradient value of 120 is between the two thresholds and is connected to the edge of the high threshold, so it is retained as an edge.

[0049] The SIFT feature point matching algorithm is used to compare the defect image with the circuit design draft (Gerber file). The steps include scale space extremum detection (e.g., the pixel value of 200 at scale layer σ=1.6 is an extremum point), key point localization (removing low contrast points), orientation assignment (e.g., 45° has the largest proportion in the gradient orientation histogram), and descriptor generation (128-dimensional vector). A Euclidean distance threshold of 0.6 is used for matching. The coordinates, size, and shape of the open circuit region are calculated: for example, the coordinates of the open circuit region are (0,0)-(1mm,1mm), and the size is 1. mm×1mm; the repair pattern is automatically generated based on the comparison results: for example, the open circuit length is 1mm, the copper surface overlap length at both ends is 0.5mm, and the repair pattern width is 25μm; for open circuits with copper surfaces at both ends, an overlap length of 0.1-10mm is designed on the copper surfaces at both ends (preferably 0.5-2mm to balance adhesion and accuracy), and the overlap width is ≤ the line width; for open circuits with copper surface defects at one end, an overlap length of 0.1-10mm is designed only on the effective copper surface side; the main body of the repair pattern strictly follows the width, direction, and spacing requirements of the original line design;

[0050] 3. Uniform metal powder spraying: Use a pneumatic powder spraying device to spray metal powder in the defect area and its surrounding 1-2mm range; the powder particle size is controlled at 1-50μm (preferably 5-20μm to balance flowability and sintering accuracy), sphericity ≥90%, loose density ≥4.5g / cm³, and flowability ≤30s / 50g; the powder layer thickness is 1-100μm (5-30μm depending on the line thickness); the spraying pressure is 0.1-0.5MPa, and the nozzle moving speed is 50-100mm / s to ensure uniform powder distribution without accumulation; for example: the defect area is 1mm×1mm, the perimeter expands by 1mm, the total area is 3mm×3mm, the nozzle moving speed is 80mm / s, and the spraying time is 3mm / (80mm / s)=0.0375s; the powder layer thickness is 10μm, and the powder mass in this area is 3mm×3mm×10μm×4.8g / cm³=0.432mg;

[0051] 4. Laser sintering to form conductive circuits: A fiber laser (wavelength 1064nm, photothermal conversion efficiency ≥90%) is used, with output power controlled at 10-50W and spot diameter at 10-50μm (matching the width of the repaired circuit); scanning speed is 100-500mm / s, and pulse frequency is 10-50kHz; laser energy density calculation: E=P / (v*d) (P is power, v is scanning speed, d is spot diameter); for example, bronze alloy powder requires an energy density of 1.67×10^5. With a laser beam density of W / m², a spot diameter of 25μm, and a scanning speed of 200mm / s, the calculated power P = E × v × d = 1.67e⁵ × 0.2 × 25e⁻⁶ = 0.835W (20W was actually used to ensure melting). Laser parameters were adjusted according to the type of metal powder: for low-melting-point alloys (such as bronze alloys, melting point approximately 900℃), 20W power and 200mm / s speed were used to achieve complete melting; for high-melting-point alloys (such as stainless steel, melting point approximately 1500℃), 30W power and 150mm / s speed were used to achieve surface melting. During laser sintering, the PCB board temperature was controlled between 50-100℃ to avoid deformation of the FR-4 substrate. The resistivity of the sintered circuit was ≤1.5 × 10⁻⁶. Ω·m, resistivity difference from the original circuit ≤10%;

[0052] 5. Vacuum removal of unsintered powder: Use a vacuum device with a vacuum level of -0.08 to -0.1 MPa, a nozzle diameter of 2-5 mm, and maintain a distance of 1-5 mm from the PCB surface; move the nozzle along the defect area at a speed of 50-100 mm / s to ensure that the unsintered powder is completely removed; after removal, use compressed air (pressure 0.1 MPa) to blow away the PCB surface to remove residual tiny powder particles; for example: if the defect area is 1 mm × 1 mm, the nozzle diameter is 3 mm, the speed is 60 mm / s, the removal time = 1 mm / (60 mm / s) = 0.0167 s; the compressed air blowing time is 0.1 s.

[0053] The specific implementation method is as follows:

[0054] AOI (Automated Optical Inspection) is a common method for inspecting PCB surface traces. This method involves scanning the physical board and comparing the scanned image with the original circuit design to determine if there are open or short circuit defects. If an open circuit defect is confirmed, its location is marked in the AOI. The PCB is then transferred to a trace repair device, and the defect location information recorded by the AOI is also transmitted to the repair device.

[0055] The line repair equipment locates the defect and photographs it. The photographs are processed by computer and compared with the original line design drawing to determine the repair pattern design. This repair pattern design requires an overlap length of 0.1µm to 10mm on the copper surfaces at both ends of the open circuit. For defects with missing copper surfaces, an overlap length of 0.1µm to 10mm can be designed only on one end. The overlap width can be less than (or equal to) the line width. Except for the overlap portion, the repair pattern can be based on the original line design drawing.

[0056] The circuit repair equipment evenly spreads a layer of metal powder around the defect location requiring repair. The thickness of the metal powder layer is 1µm to 100µm, and the metal powder can be cobalt-chromium alloy, stainless steel, bronze alloy, titanium alloy, or nickel-aluminum alloy, or a mixture of different alloy powders. These metal powders need to meet requirements such as small particle size, narrow particle size distribution, high sphericity, good flowability, and high loose packing density. A laser in the circuit repair equipment irradiates the metal powder according to the repair pattern, melting the powder, either on its surface or in the lower melting point portions. These molten portions connect the metal powder to form conductive metal circuits. Powder not irradiated by the laser remains in its original loose metal powder state and is subsequently removed by a vacuum device in the circuit repair equipment. Conductive circuits are left on the PCB board surface, completing the repair of the open circuit defect.

[0057] The above repair method is highly accurate and can repair open circuits larger than 25µm. It is also highly efficient, can be fully automated, and is suitable for mass production.

[0058] Example 1: Repairing an open circuit in a 25μm circuit using bronze alloy powder

[0059] 1.1 Experimental materials: PCB board (FR-4 substrate, line width 25μm, thickness 18μm), bronze alloy powder (particle size 5-10μm, sphericity 92%, loose density 4.8g / cm³, flowability 25s / 50g).

[0060] 1.2 Detection steps: AOI resolution 25μm / pixel, scanning speed 0.5m² / min, positioning accuracy ±5μm, image exposure time 15ms;

[0061] 1.3 Graphic design: Open circuit length 1mm, copper overlap length at both ends 0.5mm, overlap width 25μm;

[0062] 1.4 Powder spraying: pneumatic nozzle pressure 0.2MPa, moving speed 80mm / s, powder layer thickness 10μm;

[0063] 1.5 Laser parameters: fiber laser 1064nm, power 20W, spot diameter 25μm, scanning speed 200mm / s, pulse frequency 20kHz;

[0064] 1.6 Results: The resistivity of the repaired line was 1.2 × 10⁻⁶. Ω·m, 5% difference from the original circuit; adhesion test (tensile method) reaches 1.5N / mm²; accuracy ±2μm, no short circuit or open circuit; repair time 10s / piece;

[0065] Example 2: Repairing a 50μm open circuit with stainless steel powder

[0066] 2.1 Experimental materials: PCB board (FR-4 substrate, line width 50μm, thickness 20μm), stainless steel powder (particle size 10-20μm, sphericity 90%, loose density 5.2g / cm³, flowability 28s / 50g);

[0067] 2.2 Inspection steps: AOI resolution 25μm / pixel, scanning speed 0.5m² / min, positioning accuracy ±5μm, image exposure time 18ms;

[0068] 2.3 Graphic design: Open circuit length 2mm, copper overlap length at both ends 1mm, overlap width 50μm;

[0069] 2.4 Powder spraying: pneumatic nozzle pressure 0.3MPa, moving speed 70mm / s, powder layer thickness 15μm;

[0070] 2.5 Laser parameters: fiber laser 1064nm, power 30W, spot diameter 50μm, scanning speed 150mm / s, pulse frequency 30kHz;

[0071] 2.6 Results: The resistivity of the repaired line is 1.4 × Ω·m, 8% difference from the original circuit; adhesion test reached 1.8 N / mm²; accuracy ±3 μm; repair time 12 s / piece;

[0072] Example 3: Repairing defects on copper surfaces with nickel-aluminum alloy powder

[0073] 3.1 Experimental materials: PCB board (FR-4 substrate, line width 30μm, thickness 15μm, single-end copper surface defect 0.8mm), nickel-aluminum alloy powder (particle size 8-15μm, sphericity 91%, loose density 4.6g / cm³, flowability 26s / 50g).

[0074] 3.2 Inspection steps: AOI resolution 25μm / pixel, scanning speed 0.5m² / min, positioning accuracy ±5μm, image exposure time 16ms;

[0075] 3.3 Graphic design: The overlap length is only 0.8mm on the effective copper side, and the overlap width is 30μm;

[0076] 3.4 Powder spraying: pneumatic nozzle pressure 0.25MPa, moving speed 75mm / s, powder layer thickness 12μm;

[0077] 3.5 Laser parameters: fiber laser 1064nm, power 25W, spot diameter 30μm, scanning speed 180mm / s, pulse frequency 25kHz;

[0078] 3.6 Results: The resistivity of the repaired line is 1.3× Ω·m, 7% difference from the original circuit; adhesion test reached 1.6 N / mm²; accuracy ±2 μm; repair time 11 s / piece;

[0079] Comparative Example 1: Manual thread repair machine thread repair

[0080] 1.1 Experimental materials: The same PCB board as in Example 1;

[0081] 1.2 Operating steps: Manually operate the wire repair machine to press the tin-copper wire (diameter 25μm) onto both ends of the open circuit, heat the temperature to 350℃, and weld for 5 seconds per end;

[0082] 1.3 Results: The resistivity of the repaired line is 2.0 × 10⁻⁶. Ω·m, 33% difference from the original circuit; adhesion test 0.8 N / mm²; accuracy ±10 μm, 2 short circuit points present; repair time 60 s / piece;

[0083] Comparative Example 2: Conductive Silver Paste + Electroplating

[0084] 2.1 Experimental Materials: PCB board as in Example 1, conductive silver paste (resistivity 1.0 × 10⁻⁶). Ω·m);

[0085] 2.2 Operation steps: Apply silver paste (10μm thickness), bake at 150℃ for 30min; electroplat copper with a thickness of 5μm for 10min;

[0086] 2.3 Results: The resistivity of the repaired line was 1.1 × 10⁻ 6 Ω·m, 3% difference from the original circuit; adhesion test 1.2N / mm²; accuracy ±5μm; repair time 45s / piece; but it cannot repair circuits below 25μm, and the silver paste is expensive;

[0087] Comparative analysis of examples and comparative examples:

[0088]

[0089] Technical principle analysis:

[0090] 1. Laser sintering mechanism: After the laser energy is absorbed by the metal powder, it is converted into heat energy, which melts the powder particles or the surface, forming a metallurgical bond; for spherical powder, the surface tension of the molten liquid makes the particles more tightly connected, improving the conductivity and adhesion of the circuit.

[0091] 2. Powder selection criteria: Small particle size (5-20μm) can improve precision; high sphericity (≥90%) can improve flowability and loose packing density, ensuring uniform powder distribution; high loose packing density (≥4.5g / cm³) can reduce porosity after sintering.

[0092] 3. Temperature control: The PCB board temperature is controlled between 50-100℃ to avoid deformation of the FR-4 substrate (glass transition temperature of approximately 130℃); laser parameter adjustment can achieve localized heating without affecting surrounding circuitry.

[0093] 4. Automation advantages: AOI inspection, graphic design, powder spraying, laser sintering, and vacuum removal are all fully automated, reducing human error and improving the efficiency of mass production;

[0094] Therefore, the repair method of this invention has significant advantages over existing technologies: 1. Superior performance: resistivity difference ≤10%, adhesion ≥1.5N / mm², accuracy ±2-3μm, far superior to the performance of manual wire repair machines (Comparative Example 1); 2. Higher efficiency: repair time is only 10-12s / piece, which is 5-6 times that of manual wire repair machines and about 4 times that of conductive silver paste method; 3. Wider applicability: can repair dense lines and copper surface defects of 25μm or more, solving the problem that existing technologies cannot repair dense lines or small-sized lines; 4. Lower cost: uses metal powder instead of expensive conductive silver paste, and is fully automated with no labor costs, resulting in a significantly lower overall cost than existing solutions; 5. Stronger reliability: no short circuits or open circuits, the sintered lines are tightly bonded to the original lines, have good long-term stability, and are suitable for large-scale application in repairing open circuit defects in PCB lines.

[0095] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for repairing open-circuit defects in PCB circuits, characterized in that, The method includes: (1) Detect the PCB surface circuitry using automated optical inspection equipment to identify the location of open circuit defects; (2) Perform image processing on the location of the open circuit defect and compare it with the circuit design draft to generate a repair graphic; (3) Spray metal powder in and around the open circuit defect area; (4) The metal powder is sintered by laser to form a conductive circuit; (5) Remove unsintered metal powder.

2. The method according to claim 1, characterized in that, In step (1), the resolution of the automatic optical inspection device is 25 μm / pixel, the scanning speed is 0.5 m² / min, the circuit image is acquired by illuminating with a ring LED light source, and the open circuit defect is identified by a grayscale comparison algorithm.

3. The method according to claim 1, characterized in that, In step (2), the image processing includes grayscale conversion, Gaussian filtering, histogram equalization and edge detection, and the defect image is compared with the circuit design draft by using the SIFT feature point matching algorithm to automatically generate the repair graphic.

4. The method according to claim 1, characterized in that, In step (2), generating the repair pattern includes designing an overlap length on the copper surfaces at both ends of the open circuit. The overlap length is 0.1-10mm, and the overlap width is less than or equal to the original line width.

5. The method according to claim 1, characterized in that, In step (3), the metal powder has a particle size of 1-50 μm, a sphericity of ≥90%, a bulk density of ≥4.5 g / cm³, a flowability of ≤30 s / 50 g, and a powder layer thickness of 1-100 μm.

6. The method according to claim 1, characterized in that, In step (3), a pneumatic powder spraying device is used when spraying metal powder, with a spraying pressure of 0.1-0.5MPa and a nozzle moving speed of 50-100mm / s.

7. The method according to claim 1, characterized in that, In step (4), the laser sintering uses a fiber laser with a wavelength of 1064nm, an output power of 10-50W, a spot diameter of 10-50μm, a scanning speed of 100-500mm / s, and a pulse frequency of 10-50kHz.

8. The method according to claim 1, characterized in that, In step (4), the PCB temperature is controlled at 50-100℃ during laser sintering, and the resistivity of the sintered circuit is ≤1.5×10⁻ 6 Ω·m, with a resistivity difference of ≤10% from the original circuit.

9. The method according to claim 1, characterized in that, In step (5), the removal of unsintered metal powder is carried out by vacuum suction, with a vacuum degree of -0.08 to -0.1 MPa, a nozzle diameter of 2-5 mm, and a nozzle moving speed of 50-100 mm / s. After suction, compressed air is used to blow the PCB surface.

10. The method according to claim 1, characterized in that, The metal powder is selected from at least one of bronze alloy, stainless steel, nickel-aluminum alloy, cobalt-chromium alloy, and titanium alloy.

Images