Metal middle frame weld cracking detection and repair method

Abstract

The application discloses a kind of metal middle frame weld cracking detection and repair method, belong to electronic equipment structural member technical field.The middle frame includes the middle plate and outer frame connected by welding, and outer frame is divided into multiple independent antenna radiation sections.The method first makes test probe and each antenna radiation section corresponding feed point on middle plate electric contact, obtains S11 reflection coefficient curve, and based on abnormal waveform, identifies the bad point position caused by weld cracking leading to conduction failure and its belonging antenna radiation section;According to the weld cracking distribution model divided according to antenna radiation section established in advance, recess is formed in corresponding weld area by CNC machining;Then conductive paste is filled in recess to restore electrical continuity;Again, the repair area is insulated.This application effectively repairs the network division defect caused by weld cracking after injection molding by zoning modeling, precise grooving and conductive filling, significantly improves product yield, avoids whole piece scrap, and has good engineering application value.

Description

Technical Field

[0001] This invention relates to the field of electronic device structural components, and in particular to a method for detecting and repairing cracks in weld seams of metal mid-frames. Background Technology

[0002] With the rapid development of 5G communication technology, smartphones and other mobile terminals are placing higher demands on the electromagnetic compatibility and antenna performance of metal structural components. Currently, high-end mobile phone frames generally adopt a composite structure of die-cast mid-plate and metal outer frame. For example, a die-cast aluminum mid-plate is paired with a 6-series aluminum alloy outer frame: the die-cast aluminum mid-plate is formed by high-pressure die casting, possessing good rigidity and cost advantages; the aluminum alloy outer frame is precision machined by CNC and has multiple antenna isolation cutouts, dividing the outer frame into several independent antenna radiation areas. After the two are pre-positioned using positioning structures such as pins and pin holes, they are metallurgically bonded using laser welding to form an integral metal mid-frame.

[0003] However, in actual production, this type of midframe requires TRI nano-injection molding pretreatment and high-pressure injection molding after laser welding. TRI treatment uses electrochemical corrosion and triazine thiol film formation to generate nanoscale honeycomb pores on the metal surface to enhance plastic adhesion. However, this process slightly corrodes the weld area, reducing weld penetration and joint strength. Subsequently, under injection pressures as high as 50–150 MPa, some welds develop microcracks or even open cracks due to residual stress concentration or original welding defects, causing the antenna feed path, which should have been conductive, to be interrupted.

[0004] Such weld cracks typically occur at the interface between the middle plate and the outer frame, and are difficult to detect visually due to being covered by the subsequent injection molding layer. Currently, the industry mainly relies on CCD visual inspection after the welding process for interception: on the one hand, the flatness of the middle plate and the outer frame is measured to determine the assembly fit; on the other hand, a high-magnification lens is used to observe whether there are cracks or spalls on the weld surface. However, this method has significant limitations: (1) The flatness tolerance of the middle plate and the outer frame is present in the incoming material, which makes it impossible to effectively identify some defective products; (2) The surface of the weld is often covered with slag, oxides or spatter, which interferes with CCD imaging and causes misjudgment or missed detection; (3) CCD can only detect surface defects on the front side of the weld and cannot detect microcracks inside or on the back side; (4) Even if the welding appearance is qualified, TRI corrosion and injection stress may still induce subsequent cracking, causing defective products to flow into the final testing stage.

[0005] Ultimately, these products with weld cracks exhibited abnormal S11 reflection coefficients in specific frequency bands during vector network analysis testing (commonly referred to as "vector network analysis testing" in the industry). Due to the lack of conductivity in the antenna feed path, they were deemed unqualified, resulting in a failure rate as high as 8% during vector network analysis testing, severely lowering the overall yield rate. Currently, the industry lacks an effective rework solution for this type of weld cracking problem in injection-molded mid-frames, typically requiring scrapping, leading to waste of materials and production capacity.

[0006] Therefore, there is an urgent need for a repair technology that can accurately locate and efficiently repair weld continuity failures, especially suitable for metal frames with multi-antenna isolation structures, in order to restore their antenna electrical continuity and improve the yield of vector network analysis and testing. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for detecting and repairing weld cracks in metal mid-frames, in order to accurately locate and efficiently repair mid-frame products with weld continuity failures after injection molding, thereby improving product yield.

[0008] To achieve the above objectives, the present invention provides a method for detecting and repairing weld cracks in a metal frame. The metal frame includes a metal middle plate and a metal outer frame, which are connected by welding. The outer frame has multiple antenna isolation cuts, dividing it into multiple independent antenna radiation segments. The method includes the following steps: S1. Using a vector network analyzer, the test probe is electrically contacted with the feed point of each antenna radiation segment on the metal plate to perform antenna signal testing on each antenna radiation segment and obtain the corresponding S11 reflection coefficient curve. Based on the waveform difference between the S11 reflection coefficient curve and the reference good product curve in the preset test frequency band, the defective points caused by weld cracking and their corresponding antenna radiation segments are identified. The waveform difference is manifested as the offset of the peak or trough position of the measured curve relative to the reference curve exceeding a preset threshold. S2. Based on the pre-established weld crack distribution model divided by antenna radiation segment, determine the groove processing parameters of the weld area corresponding to the defective point, and form the groove in the weld area by CNC machining according to the groove processing parameters; the weld crack distribution model is established based on the following steps: select multiple representative defective samples for each antenna radiation segment, perform cross-sectional analysis, statistically analyze the distribution law of weld cracks in the radiation segment, and determine the corresponding groove processing parameters according to the distribution law; S3. Fill the groove with conductive paste to re-establish electrical connection between the metal parts on both sides of the crack, thereby restoring the electrical continuity between the antenna radiating section and its corresponding feed point; S4. Insulate the surface of the groove and test the antenna signal again through the feed point. Transfer the qualified product to the subsequent manufacturing process.

[0009] In the method for detecting and repairing weld cracks in the metal frame of the present invention, the establishment of the weld crack distribution model divided according to the antenna radiation segment includes the following steps: For each independent antenna radiating segment, multiple metal frame samples that were determined to be defective in that radiating segment by antenna signal testing were selected. The weld seam of the corresponding antenna radiation segment in each sample was sectioned, and the center line trajectory of the actual weld crack was obtained from the section image, and its spatial position and extension shape were recorded. After aligning the crack trajectories of each sample in a unified coordinate system, a reference center line characterizing the typical crack path of the antenna's radiating section is generated by statistical averaging and curve fitting. Based on the reference centerline, a conformal groove profile is generated along its direction and in combination with preset width and depth parameters, serving as a repair grooving template for the antenna radiating section. The repair grooving template is converted into grooving parameters to guide the rework of defective products in the same radiation section.

[0010] In the method for detecting and repairing weld cracks in the metal frame of the present invention, the conductive paste is conductive copper paste or conductive silver paste, and its volume resistivity is less than that of the middle plate and the outer frame.

[0011] In the method for detecting and repairing cracks in the weld seam of the metal frame of the present invention, the width of the groove is 0.8–1.2 mm, the depth is 0.8–0.9 mm, and it does not exceed the thickness of the plastic layer on the surface of the metal frame.

[0012] In the method for detecting and repairing cracks in the weld seam of the metal frame of the present invention, after filling the conductive slurry in step S3, the conductive slurry is further subjected to a heat curing treatment.

[0013] In the method for detecting and repairing cracks in the weld seam of the metal mid-frame of the present invention, the insulation treatment includes: melting plastic particles of the same material as the original plastic layer of the mid-frame and filling them into the surface of the groove, and then grinding them smooth; or applying instant insulating adhesive, UV curing adhesive, epoxy resin or nano-ceramic coating to the surface of the groove for insulation.

[0014] In the method for detecting and repairing cracks in the weld seam of the metal frame of the present invention, step S4, after the insulation treatment is completed, further includes: laser engraving the repair area to increase the surface roughness in order to improve the adhesion of the subsequent adhesive.

[0015] In the method for detecting and repairing cracks in the weld seam of the metal frame of the present invention, before CNC machining, the VC heat spreader and large adhesive backing material on the metal frame are removed, and the Z-axis zero position of the machining surface is calibrated by a probe to ensure that the groove position and the defective point are accurately aligned.

[0016] This invention offers the following advantages: The solution utilizes a vector network analyzer for antenna signal testing, accurately identifying the network distribution defects caused by weld cracks and their corresponding antenna radiation segments. This avoids the problem of traditional CCD inspection, which only allows surface inspection and misses internal or back-side micro-cracks, thus improving detection accuracy. Based on a pre-established partition model, the slotting location is determined, ensuring precise positioning of the repair operation to the actual cracked area, reducing blind spots and improving repair efficiency and success rate. By filling the groove with highly conductive slurry, welding defects are effectively compensated, the antenna feed path is restored, and product yield is improved. Through insulation treatment and retesting, the repaired frame meets antenna signal testing standards, ensuring the reliability and consistency of the final product. This invention effectively repairs network distribution defects caused by weld cracks after injection molding, significantly improving product yield, avoiding complete scrapping, and possessing significant engineering application value. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram illustrating the steps of a method for detecting and repairing cracks in the weld seam of a metal frame provided in an embodiment of the present invention.

[0018] Figures 2-3 This is a schematic diagram of an abnormal waveform in vector network analysis and testing provided in an embodiment of the present invention.

[0019] Figure 4 This is a schematic diagram of the weld sectioning effect provided in an embodiment of the present invention.

[0020] Figure 5 This is a schematic diagram of the grooving effect provided in an embodiment of the present invention.

[0021] 1. Plastic surface; 2. Weld seam; 3. Metal surface of the middle plate; 4. Laser engraved area of ​​the metal surface of the middle plate; 5. Groove; 6. Outer frame; 7. Plastic step; 8. Plastic burr. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. It should be understood that the embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0024] This invention provides a method for detecting and repairing weld cracks in a metal frame. The metal frame includes a metal middle plate and a metal outer frame, which are connected by welding. The outer frame has multiple antenna isolation cuts, dividing it into multiple independent antenna radiation segments. The method for detecting and repairing weld cracks in a metal frame includes the following steps: S1. Using a vector network analyzer, the test probe is electrically contacted with the feed point of each antenna radiation segment on the metal plate to perform antenna signal testing on each antenna radiation segment and obtain the corresponding S11 reflection coefficient curve. Based on the waveform difference between the S11 reflection coefficient curve and the reference good product curve in the preset test frequency band, the defective points caused by weld cracking and their corresponding antenna radiation segments are identified. The waveform difference is manifested as the offset of the peak or trough position of the measured curve relative to the reference curve exceeding a preset threshold. S2. Based on the pre-established weld crack distribution model divided by antenna radiation segment, determine the groove processing parameters of the weld area corresponding to the defective point, and form the groove in the weld area by CNC machining according to the groove processing parameters; the weld crack distribution model is established based on the following steps: select multiple representative defective samples for each antenna radiation segment, perform cross-sectional analysis, statistically analyze the distribution law of weld cracks in the radiation segment, and determine the corresponding groove processing parameters according to the distribution law; S3. Fill the groove with conductive paste to re-establish electrical connection between the metal parts on both sides of the crack, thereby restoring the electrical continuity between the antenna radiating section and its corresponding feed point; S4. Insulate the surface of the groove and test the antenna signal again through the feed point. Transfer the qualified product to the subsequent manufacturing process.

[0025] In practical applications, vector network analysis tests are conducted on mid-frame products. Defective points that are identified due to weld cracking and conduction failure are marked. Subsequently, these defective points are classified and reworked in a centralized manner according to their corresponding locations to save rework costs.

[0026] In this embodiment of the invention, a vector network analyzer is used for antenna signal testing to accurately identify the poor network distribution points caused by weld cracks and their corresponding antenna radiation segments. This avoids the problem of traditional CCD inspection, which can only inspect the surface and miss internal or back-side micro-cracks, thus improving detection accuracy. The slotting location is determined based on a pre-established partition model, ensuring that the repair operation is precisely positioned to the actual cracked area, reducing blind spots and improving repair efficiency and success rate. By filling the groove with highly conductive slurry, welding defects are effectively compensated, the antenna feed path is restored, and product yield is improved. Through insulation treatment and retesting, the repaired frame meets antenna signal testing standards, ensuring the reliability and consistency of the final product.

[0027] The purpose of vector network analysis (VNA) testing is to evaluate the impedance matching performance of an antenna in specific frequency bands, such as 5G, 4G, Wi-Fi, and Bluetooth. Better matching results in less reflected energy, higher antenna radiation efficiency, and better mobile signal and wireless connection quality. Its core is measuring the S-parameters of the antenna system, i.e., scattering parameters. For mobile phone frame testing, the most important parameter is the S11 parameter, i.e., reflection coefficient. The test procedure is as follows: The vector network analyzer generates a known, specific frequency RF signal and injects this signal into the antenna feed point on the mobile phone frame through an RF probe or cable. After the signal reaches the antenna, part of the energy is effectively radiated out, while the other part is reflected back due to impedance mismatch and other reasons. The network analyzer accurately measures the strength and phase of the reflected signal and compares it with the transmitted signal to calculate the S11 parameter.

[0028] In this embodiment of the invention, the waveform difference is manifested as the offset of the peak or trough position of the measured curve relative to the reference curve exceeding a preset threshold. By setting a specific offset threshold to determine whether weld cracking exists, the detection process becomes more standardized and objective, reducing human interference and improving the consistency and reliability of the detection results.

[0029] Figures 2-3 This is a schematic diagram of abnormal waveforms in vector network analysis testing provided in an embodiment of the present invention. The horizontal axis represents frequency in MHz, and the vertical axis represents the amplitude of the S11 reflection coefficient, i.e., return loss, in dB. The white curve is the reference curve, and the yellow curve is the measured curve. Figure 2 In the measured curve, the first trough (around 1500MHz) shows a significant shift relative to the reference curve. Figure 3 In the measured curve, the first peak (around 1900MHz) and the second trough (around 2100MHz) are significantly offset from the reference curve. Figure 2 and Figure 3The offset values ​​in the measured curves all exceeded the preset thresholds, therefore, the corresponding antenna radiating segments were determined to have weld cracking issues. If the measured curves and reference curves basically coincide, it indicates that there is no weld cracking. Each antenna radiating segment has a corresponding reference impedance, and the reference curve is obtained by fitting the S11 reflection coefficient amplitude corresponding to the reference impedance of that antenna radiating segment. In actual testing, if weld cracking exists, the actual impedance corresponding to that antenna radiating segment will be greater than the reference impedance, and the measured S11 reflection coefficient will deviate relative to the reference value. This is reflected in the S11 curve as a shift in the peaks and troughs.

[0030] In this embodiment of the invention, the establishment of the weld crack distribution model divided according to the antenna radiation segment includes the following steps: (1) For each independent antenna radiation segment, select multiple metal frame samples that are determined to be defective in that radiation segment by antenna signal testing; (2) Cut the weld of the corresponding antenna radiation section in each sample, obtain the center line trajectory of the actual weld crack based on the cut surface image, and record its spatial position and extension shape. (3) After aligning the crack trajectories of each sample in a unified coordinate system, a reference center line characterizing the typical crack path of the antenna radiation section is generated by statistical averaging and curve fitting. (4) Based on the reference center line, generate a conformal groove profile along its direction and in combination with preset width and depth parameters, as a repair grooving template for the antenna radiating section. (5) The repair grooving template is converted into grooving parameters to guide the rework of defective products in the same radiation section.

[0031] In one specific embodiment of the present invention, at least 10 defective samples from the same antenna radiation segment are selected. For each sample, its cross-sectional image is analyzed, and the weld crack centerline trajectory is obtained through algorithms such as Unet segmentation, represented as a discrete point sequence. ,in, Let be the number of sampling points for the i-th crack. Then, the CNC machining parameters are generated using the following algorithm: (1) Coordinate alignment and normalization. Based on the design CAD model of the antenna radiating section, the crack trajectories of all samples are rigidly registered through feature points to eliminate overall displacement / rotation deviation.

[0032] (2) Construct the average crack trajectory. Perform dynamic time warping on all aligned crack trajectories to make each trajectory have the same number of points, calculate the average position point by point, and obtain the average crack centerline.

[0033] (3) Fit a smooth curve and expand the width. Perform B-spline or cubic spline interpolation on the average crack centerline to generate a smooth and continuous reference curve. Using this curve as the centerline, offset w / 2 to both sides to generate equidistant offset curves, forming a closed curve groove profile, where w is the groove width.

[0034] (4) Determine the slot length and safety margin. Calculate the average trajectory length. The 95th percentile of the crack lengths of all samples was taken as the maximum coverage length. Extend the reference curve at both ends This ensures coverage of extremely long cracks.

[0035] (5) Generate CNC executable toolpaths. Discretize the curved groove contour into a high-density point set, convert it into G-code or a toolpath format supported by CAM software, and specify: tool diameter, depth of cut, and tool path direction.

[0036] In practice, if the cracks are distributed very irregularly and one grooving cannot repair all the cracks, multiple grooving methods can be used to repair all the cracks.

[0037] Figure 4 This is a schematic diagram illustrating the weld sectioning effect provided in an embodiment of the present invention. Figure 4 As shown, the weld is located on the middle plate. The cross-sectional view reveals that plastic surface 1 is attached to both sides of weld 2, and several scattered cracked areas appear in the middle of weld 2. For the same middle frame product, the location, shape, and size of the welds connecting different antenna radiating sections to the middle plate may vary. Therefore, it is necessary to cross-section the welds corresponding to each antenna radiating section separately, analyze the characteristics of the welds and cracks on them, and determine the center position, extension direction, length, and geometry of the slot based on statistical values. It should be noted that during rework, the welds are covered by the plastic layer, and the cracks are not visible. Therefore, it is necessary to analyze the weld characteristics by cross-sectioning some samples in the early stages to determine the processing parameters for subsequent slotting. Cross-sectioned samples will be scrapped. By cross-sectioning and analyzing representative samples of each independent antenna radiating section, the specific cracking patterns of welds in different areas can be accurately grasped, providing a scientific basis for subsequent rework and significantly improving the repair accuracy, reliability, and efficiency.

[0038] In this embodiment of the invention, step S4, after the insulation treatment is completed, further includes: laser engraving the repair area to increase surface roughness, thereby improving the adhesion of the subsequent adhesive. The main parameters for laser engraving are as follows: speed: 1000-3500 mm / s; power: 70%-100%; current: 1-10 A; frequency: 10-35 kHz; Q pulse width: 10-35; fill density: 0.1±0.05 mm; angle: 45° / 135°. In a specific embodiment of the invention, after laser engraving, the surface energy of the plastic surface is tested using a No. 36 dyne pen to determine its suitability for adhesive bonding. Laser engraving increases the roughness of the insulating surface, improves the bonding performance between the repair area and the subsequent adhesive, enhances the overall structural strength, and reduces quality problems caused by poor adhesion.

[0039] Figure 5 This is a schematic diagram illustrating the grooving effect provided in an embodiment of the present invention. Figure 5 As shown, a plastic step 7 is provided between the middle metal surface 3 and the outer frame 6, and the groove 5 is located on the side of the middle metal surface 3 near the plastic step 7. Both the plastic surface 1 and the middle metal surface 3 in the area near the groove 5 are laser-engraved with a grid-shaped texture to increase surface roughness. The laser-engraved area 4 on the middle metal surface is the area on the middle metal surface 3 where the pattern is laser-engraved. Because the weld is covered by the plastic surface 1 before CNC grooving, the plastic surface 1 is cut during CNC machining. During this process, plastic burrs 8 may be formed. After grooving, the plastic burrs 8 need to be removed before injecting conductive paste into the groove 5 to prevent the plastic burrs 8 from affecting the conductivity of the conductive paste.

[0040] In this embodiment of the invention, the conductive paste is conductive copper paste or conductive silver paste, and its volume resistivity is lower than that of the middle plate and the outer frame. Theoretically, as long as the two ends of the weld crack are connected by a conductive material to form a conductive channel, it is sufficient. However, since antenna signal testing is also related to the impedance of the object being tested, in practical applications, a conductive paste with a resistivity lower than that of the connected materials is generally chosen. In this embodiment of the invention, a low-resistivity conductive paste is used to fill the groove. Because its volume resistivity is lower than that of the metal middle plate and the outer frame material, it ensures that the conductivity after filling is better than that of the original weld joint, further enhancing the antenna signal transmission quality. The cost of conductive copper paste is lower than that of conductive silver paste; therefore, it is preferable to use conductive copper paste to fill the groove.

[0041] In this embodiment of the invention, the width of the groove is 0.8–1.2 mm, and the depth is 0.8–0.9 mm, not exceeding the thickness of the plastic layer on the surface of the metal frame. The thickness of the plastic layer on the surface of the metal frame is determined during product design. The width of the groove must be greater than the width of the crack, and must not affect the adhesion of related auxiliary materials. The design of a width of 0.8–1.2 mm and a depth of 0.8–0.9 mm ensures sufficient conductive area for good electrical connection, while avoiding excessively deep grooves that could damage structural integrity or exceed the thickness of the plastic layer, affecting appearance and subsequent processes.

[0042] In this embodiment of the invention, after filling the conductive paste in step S3, the conductive paste is further subjected to a heat-curing treatment. In some specific embodiments of the present invention, the conductive paste is conductive copper paste. After filling the groove with conductive copper paste, it is baked at 70°C for 30 minutes to cure the conductive copper paste. Heat curing enhances the bonding force between the conductive paste and the substrate, preventing detachment and failure due to temperature changes or mechanical stress, and ensuring a long-term stable and reliable electrical connection.

[0043] In this embodiment of the invention, the insulation treatment includes: melting plastic particles of the same material as the original mid-frame plastic layer and filling them into the groove surface, then polishing it smooth; or applying an instant-drying insulating adhesive, UV-curing adhesive, epoxy resin, or nano-ceramic coating to the groove surface for insulation. Whether melting plastic particles of the same material or using instant-drying adhesive or other methods, it effectively isolates conductive parts, prevents short-circuit risks, and adapts to different production environment requirements, improving process flexibility. In some specific embodiments of this invention, a soldering iron is used to melt plastic particles of the same material as the original mid-frame plastic layer and fill them into the groove surface, then polishing it smooth. The soldering iron temperature is set to 290°C. The plastic particles and the plastic layer have the same color and material, ensuring consistent appearance.

[0044] In this embodiment of the invention, before CNC machining, the VC heat spreader and large adhesive backing material on the metal frame are removed, and the machining surface is calibrated in the Z-axis direction using a probe to ensure precise alignment between the groove position and the defective point. After repair, the VC heat spreader and large adhesive backing material are reassembled. Removing the VC heat spreader and large adhesive backing material and performing Z-axis zero-position calibration ensures the high precision of the groove position during CNC machining, avoids errors caused by the presence of the materials, and improves the success rate and efficiency of the repair operation.

[0045] Before implementing the metal frame weld crack detection and repair method of this invention, defective products identified through vector network analysis testing had to be scrapped entirely. However, statistical data shows that after implementing this method, 95% of defective products identified through vector network analysis testing can be successfully repaired. To date, this solution has repaired 80,000 defective products identified through vector network analysis testing, significantly reducing the scrap rate of mid-frame products and lowering production costs.

[0046] The above are merely specific embodiments of the present invention and should not be construed as limiting the scope of the present invention. Equivalent variations made by those skilled in the art based on this invention, as well as changes well-known to those skilled in the art, should still fall within the scope of the present invention.

Claims

1. A method for detecting and repairing weld cracks in a metal frame, wherein the metal frame comprises a metal middle plate and a metal outer frame, which are connected by welding, wherein the outer frame has multiple antenna isolation cuts to divide the outer frame into multiple independent antenna radiation segments; characterized in that, The method includes the following steps: S1. Using a vector network analyzer, the test probe is electrically contacted with the feed point of each antenna radiation segment on the metal plate to perform antenna signal testing on each antenna radiation segment and obtain the corresponding S11 reflection coefficient curve. Based on the waveform difference between the S11 reflection coefficient curve and the reference good product curve in the preset test frequency band, the defective points caused by weld cracking and their corresponding antenna radiation segments are identified. The waveform difference is manifested as the offset of the peak or trough position of the measured curve relative to the reference curve exceeding a preset threshold. S2. Based on the pre-established weld crack distribution model divided by antenna radiation segment, determine the groove processing parameters of the weld area corresponding to the defective point, and form the groove in the weld area by CNC machining according to the groove processing parameters; the weld crack distribution model is established based on the following steps: select multiple representative defective samples for each antenna radiation segment, perform cross-sectional analysis, statistically analyze the distribution law of weld cracks in the radiation segment, and determine the corresponding groove processing parameters according to the distribution law; S3. Fill the groove with conductive paste to re-establish electrical connection between the metal parts on both sides of the crack, thereby restoring the electrical continuity between the antenna radiating section and its corresponding feed point; S4. Insulate the surface of the groove and test the antenna signal again through the feed point. Transfer the qualified product to the subsequent manufacturing process.

2. The method for detecting and repairing cracks in weld seams of a metal frame according to claim 1, characterized in that, The establishment of the weld crack distribution model divided according to the antenna radiation segment includes the following steps: For each independent antenna radiating segment, multiple metal frame samples that were determined to be defective in that radiating segment by antenna signal testing were selected. The weld seam of the corresponding antenna radiation segment in each sample was sectioned, and the center line trajectory of the actual weld crack was obtained from the section image, and its spatial position and extension shape were recorded. After aligning the crack trajectories of each sample in a unified coordinate system, a reference center line characterizing the typical crack path of the antenna's radiating section is generated by statistical averaging and curve fitting. Based on the reference centerline, a conformal groove profile is generated along its direction and in combination with preset width and depth parameters, serving as a repair grooving template for the antenna radiating section. The repair grooving template is converted into grooving parameters to guide the rework of defective products in the same radiation section.

3. The method for detecting and repairing cracks in weld seams of a metal frame according to claim 1, characterized in that, The conductive paste is a conductive copper paste or a conductive silver paste, and its volume resistivity is less than that of the middle plate and the outer frame.

4. The method for detecting and repairing cracks in the weld seams of a metal frame according to claim 1, characterized in that, The groove has a width of 0.8–1.2 mm and a depth of 0.8–0.9 mm, and does not exceed the thickness of the plastic layer on the surface of the metal frame.

5. The method for detecting and repairing cracks in weld seams of a metal frame according to claim 1, characterized in that, After filling the conductive paste in step S3, the conductive paste is further subjected to a thermosetting treatment.

6. The method for detecting and repairing cracks in weld seams of a metal frame according to claim 5, characterized in that, The insulation treatment includes: melting plastic particles of the same material as the original middle frame plastic layer and filling them into the groove surface, and then polishing them smooth; or applying instant insulating adhesive, UV curing adhesive, epoxy resin or nano-ceramic coating to the groove surface for insulation.

7. The method for detecting and repairing cracks in weld seams of a metal frame according to claim 1, characterized in that, In step S4, after the insulation treatment is completed, the following steps are also included: laser engraving the repair area to increase the surface roughness and improve the adhesion of the subsequent adhesive.

8. The method for detecting and repairing cracks in weld seams of a metal frame according to claim 1, characterized in that, Before CNC machining, the VC heat spreader and large adhesive backing material on the metal frame are removed, and the Z-axis zero position of the machining surface is calibrated by a probe to ensure that the groove position is accurately aligned with the defective point.

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