Method for improving poor gold surface of nickel immersion gold
By adding an automatic visual inspection and sorting step before the nickel plating process, copper surface defects can be identified and repaired, solving the problem of high gold surface defect rate after nickel plating in the existing technology, and achieving cost savings and improved quality stability.
Patent Information
- Application Number
- CN202610198821.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-11
- Publication Date
- 2026-04-24
AI Technical Summary
The existing immersion nickel-gold process cannot effectively identify and repair defects on the copper surface, resulting in a high defect rate on the gold surface after immersion nickel-gold and a persistently high product scrap rate.
An automated visual inspection and sorting step is added before the nickel-gold plating process. Defects are identified by scanning the copper surface image and comparing it with a standard image. Repairable defects are physically repaired, while unrepairable units are subjected to resist plating treatment, forming a closed-loop process to reduce the defect rate.
It significantly reduces the defect rate of gold surface after nickel plating due to copper surface defects, reduces product scrap, saves precious metal consumption, and improves production yield and quality stability.
Smart Images
Figure CN121924699A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of printed circuit board manufacturing technology, and more specifically to a method for improving defects in the immersion nickel-gold surface. Background Technology
[0002] Chemical plating (COP) is an important PCB surface treatment process that chemically deposits nickel and gold layers onto copper pads to provide components with a solderable surface and long-term protection. Its typical process flow mainly includes three stages: pretreatment, COP, and post-treatment. Pretreatment involves cleaning and activating the copper surface through steps such as grinding and sandblasting; followed by COP processing; and finally, post-treatment, such as cleaning, completes the entire process.
[0003] However, existing nickel-gold plating processes have significant limitations:
[0004] Its pretreatment process is essentially a highly efficient "cleaning and activation" procedure, primarily targeting common oxides, minor fingerprints, and oil stains on the copper surface. However, it is not a "repair" process. Existing pretreatment processes cannot effectively address physical defects on the copper surface, such as dents, scratches, and organic adhesive residue that has adhered after high-temperature baking.
[0005] Furthermore, once the PCB has undergone the nickel-gold plating process, if defects are found on the gold surface, such as exposed copper or gold surface pits caused by the aforementioned defects, these defective products are usually unrecoverable and must be scrapped because the nickel-gold layer is difficult to remove once formed and rework would damage its structure. This results in a high scrap rate for orders from customers with high requirements for gold surface quality, leading to significant cost waste.
[0006] Therefore, there is an urgent need in the field for a new method that can effectively identify and repair potential defects on the copper surface before the nickel plating process, thereby reducing the defect rate of the gold surface from the source. Summary of the Invention
[0007] This invention provides a method for improving the defects of the gold surface in immersion nickel-gold plating, which solves the technical problem that the existing immersion nickel-gold process cannot effectively identify and repair copper surface defects before plating, resulting in a high defect rate of the gold surface and serious product scrapping after immersion nickel-gold plating.
[0008] This invention is achieved through the following technical solution:
[0009] In a first aspect, this application provides a method for improving defects in the gold surface of immersion nickel-gold plating, comprising the following steps:
[0010] The copper surface of the circuit board is ground and sandblasted to obtain a circuit board that has undergone preliminary cleaning and activation.
[0011] The circuit board that has undergone preliminary cleaning and activation is subjected to automatic visual inspection to scan and identify copper surface defects, resulting in a circuit board with completed defect marking.
[0012] Based on the defect identifier, the circuit boards that have been identified as defective are inspected and sorted to obtain circuit boards that have been repaired or scrapped.
[0013] The circuit boards that have undergone defect repair or scrapping are sandblasted to obtain clean and activated circuit boards.
[0014] The clean and activated circuit board is subjected to immersion nickel-gold treatment to obtain the immersion nickel-gold treated circuit board.
[0015] A further optimization involves performing automatic visual inspection on the circuit board that has undergone preliminary cleaning and activation to scan and identify copper surface defects. This is accomplished by comparing the captured copper surface image with a reference image in a standard product database.
[0016] A further optimization scheme is proposed, which includes one or more of the following defects: foreign objects on the copper surface, dents, and scratches.
[0017] A further optimized solution is that, based on the defect identifier, the inspection and sorting of the circuit boards that have been identified as defective includes:
[0018] The defect images identified by automatic visual inspection are confirmed, and repairable defects are physically repaired, while the circuit board units containing unrepairable defects are marked and isolated.
[0019] A further optimized solution is that the physical repair includes using grinding or wiping tools to remove foreign objects from the copper surface or smooth out minor scratches.
[0020] A further optimized solution is to use adhesive tape as a resist marking on the unrepairable circuit board unit as the marking isolation.
[0021] A further optimized solution involves sandblasting the circuit boards that have undergone defect repair or scrapping sorting. The process parameters are configured to remove new oxide layers and fingerprints generated during the repair process, and the sandblasting pressure is lower than the sandblasting parameters used in the grinding and sandblasting of the copper surface of the circuit boards.
[0022] The further optimized solution also includes the following steps:
[0023] Collect and statistically analyze the types, quantities, and distribution of defects identified by automated visual inspection to obtain defect statistics.
[0024] The further optimized solution also includes the following steps:
[0025] Collect and statistically analyze the types, quantities, and distribution data of defects identified by the automatic visual inspection to generate a defect analysis report;
[0026] The defect analysis report is fed back to the upstream production system in the circuit board manufacturing process.
[0027] A further optimization involves feeding back the defect analysis report to the upstream production system in the circuit board manufacturing process, specifically including:
[0028] If the defect analysis report indicates that copper surface foreign object defects are the main defect type, then the relevant information is fed back to the production system of the circuit board solder mask text process;
[0029] If the defect analysis report indicates that pitting and scratches are the main defect types, then the relevant information is fed back to the production system of the circuit board lamination and pattern transfer process.
[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0031] By adding a closed-loop process of automatic visual inspection and sorting before the main process of nickel plating on circuit boards, a fundamental shift from passive scrapping to proactive prevention has been achieved. It can accurately identify defects such as foreign objects, dents and scratches on the copper surface online, and effectively repair repairable defects through inspection, thereby avoiding the problem of poor gold surface after nickel plating caused by such defects from the source, and significantly reducing the product scrap rate.
[0032] For irreparable units, a barrier treatment is applied, which effectively avoids the ineffective consumption of precious metal materials and saves production costs.
[0033] Based on the statistical analysis results of the test data, the pretreatment process parameters are dynamically adjusted through feedback, forming a continuous closed-loop mechanism for process optimization, which improves the overall quality stability and production yield of the nickel-gold plating panel. Attached Figure Description
[0034] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0035] In the attached diagram:
[0036] Figure 1 A flowchart of a method for improving defects in immersion nickel-gold surfaces provided in an embodiment of this application;
[0037] Figure 2This is a layout diagram of an existing nickel-gold plating equipment.
[0038] Figure 3 The layout diagram of the nickel-gold plating equipment with added scanning and maintenance functional areas is provided for the embodiments of this application. Detailed Implementation
[0039] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.
[0040] First, some of the technical terms used in this application will be explained to help those skilled in the art understand this application.
[0041] AVI: Automated Visual Inspection;
[0042] PCB: Printed Circuit Board;
[0043] ENIG: Electroless Nickel Immersion Gold, electroless nickel gold.
[0044] Firstly, such as Figure 1 As shown, this application provides a method for improving defects in the gold surface of immersion nickel-gold plating, including the following steps:
[0045] Step S1: Grind and sandblast the copper surface of the circuit board to obtain a circuit board that has undergone preliminary cleaning and activation;
[0046] Step S2: Perform automatic visual inspection on the circuit board that has undergone preliminary cleaning and activation to scan and identify copper surface defects, and obtain a circuit board with completed defect marking;
[0047] Step S3: Based on the defect identifier, inspect and sort the circuit boards that have been identified as defective to obtain circuit boards that have been repaired or scrapped.
[0048] Step S4: Sandblast the circuit boards that have completed defect repair or scrap sorting to obtain clean and activated circuit boards.
[0049] Step S5: Perform immersion nickel-gold treatment on the clean and activated circuit board to obtain the immersion nickel-gold treated circuit board.
[0050] This embodiment innovatively embeds an automated visual inspection and sorting step before the main nickel-gold plating process on the circuit board, thus preventing gold surface defects at the source. This method can accurately identify copper surface defects online and effectively repair repairable defects, significantly reducing the gold surface defect rate after nickel-gold plating caused by defects such as foreign objects, dents, and scratches on the copper surface, thereby greatly reducing product scrap. Simultaneously, by applying a resist plating treatment to unrepairable units, ineffective precious metal consumption is avoided, saving production costs.
[0051] like Figure 2 As shown, this is a layout plan of the basic equipment for immersion nickel plating in the prior art, covering the core process units from pretreatment to immersion nickel plating. To realize the online detection, inspection, and sorting technology of this invention, an automatic visual inspection and inspection functional area (the area within the red box in the figure) is integrated into the basic layout, forming a structure as shown... Figure 3 The optimized layout is shown.
[0052] In one embodiment, step S1: grinding and sandblasting the copper surface of the circuit board to obtain a circuit board that has undergone preliminary cleaning and activation, specifically including the following steps:
[0053] Step S11: Grind the copper surface of the circuit board with a mechanical brush; specifically, the brush material is a nylon needle brush, 800-1200 mesh, and the travel speed is 3.0-5.0 meters / minute, so as to effectively remove ordinary oxides on the copper surface and homogenize its roughness, and reduce or cover very shallow scratches.
[0054] Step S12: Sandblast the polished copper surface. Specifically, the sandblasting pressure is set to 0.1-0.2 MPa, and diamond abrasive with a particle size of 150-200 mesh is used. The processing time is about 30-60 seconds to further enhance the cleanliness and activation ability of the copper surface, and obtain a circuit board that has been preliminarily cleaned and activated.
[0055] In one embodiment, step S2: performing automatic visual inspection on the circuit board that has undergone preliminary cleaning and activation to scan and identify copper surface defects, thereby obtaining a circuit board with completed defect marking, specifically includes the following steps:
[0056] Step S21: Use a high-resolution CCD vision inspection device to scan the copper surface of the circuit board after preliminary cleaning and activation to capture a clear surface image;
[0057] Step S22: Transmit the captured surface image to the image processing system, perform pixel-level comparison and analysis with the reference image pre-stored in the standard product database, and automatically identify and locate defects such as foreign objects, dents, or scratches on the copper surface according to preset grayscale, contour, and texture difference thresholds, and generate identification information containing the defect location and type. Simultaneously, transmit the defect image to the repair station to obtain the circuit board with completed defect identification; more specifically, this is implemented as follows:
[0058] The surface images captured by the industrial camera are transmitted in real time to the image processing system via Gigabit Ethernet or Camera Link interface. The system calls image processing library functions such as OpenCV or Halcon to normalize the real-time images with standard images pre-stored in the SQLite database. Then, a template matching algorithm is used to perform pixel-level comparison analysis. By setting the grayscale difference threshold to ±15 grayscale levels, the contour matching degree threshold to ≥90%, and the texture feature variance threshold to ≤0.05, the system automatically identifies and locates defects such as foreign objects with a particle size >50μm, pits with a depth >5μm, and scratches with a width >10μm. Finally, the defect coordinates, type code, and confidence information containing the X and Y coordinates are encapsulated in JSON format to generate identification information. At the same time, the high-definition image stream of the defect area is pushed to the industrial control computer of the maintenance station via the RTSP protocol.
[0059] Among them, the defect types include foreign objects on the copper surface, dents, and scratches; the defect locations include the specific coordinates on the copper surface and the location of the circuit board unit where they are located.
[0060] In one specific embodiment, the generated defect identifier adopts a simplified format of "defect type-location-level". For example, FM-B3-2 indicates that there is a level 2 (medium) foreign object defect in area B3, Dent-A5-3 indicates that there is a level 3 (severe) dent defect in area A5, and Scratch-C3-1 indicates that there is a level 1 (minor) scratch defect in area C3. This identifier, through the combination of type abbreviation (FM: foreign object, Dent: dent, Scratch: scratch), grid location number (such as B3), and numerical level (level 1-3), intuitively reflects the defect classification, location coordinates, and severity, providing maintenance personnel with a quick basis for judgment.
[0061] In one embodiment, step S3: Based on the defect identifier, the circuit boards that have been defect-identified are inspected and sorted to obtain circuit boards that have completed defect repair or scrapping sorting, specifically including the following steps:
[0062] Step S31: For defects that are determined to be repairable after verification, physical methods are used for repair. Specifically, repairable defects are foreign objects attached to the surface or minor scratches. Specifically, a lint-free cloth dampened with a special cleaning agent is used for wiping, or a fine grinding tool is used for gentle smoothing. It is preferred to use professional tools to remove foreign objects to ensure the repair effect.
[0063] Step S32: For defects that are determined to be irreparable after verification, adhesive tape is firmly affixed to the corresponding circuit board unit as a resist marking, so that the unit will not deposit nickel gold in the subsequent nickel gold plating step, thereby saving gold salt while completing the sorting; specifically, irreparable defects are deep pits or severe scratches; specifically, the adhesive tape is green.
[0064] In one embodiment, step S4 involves sandblasting the circuit boards that have undergone defect repair or scrap sorting to obtain clean and activated circuit boards. The purpose of this treatment is to remove contaminants such as new oxide layers and fingerprints that may be generated during the repair process. To achieve this purpose and avoid excessive damage to the copper surface, the process parameters need to be set more gently. Specifically, without using a grinding brush, the sandblasting pressure can be controlled at 0.05–0.1 MPa, which is lower than the parameters of the first pretreatment. This way, while removing contaminants, the copper surface color remains consistent, and a clean and activated surface is obtained, preparing for the subsequent nickel-gold plating process.
[0065] In one embodiment, the nickel-gold plating process in step S5 is performed according to conventional process parameters in the art; specifically, the circuit board, which has been treated in all the preceding steps and has a clean and activated surface, is immersed in a chemical nickel-gold plating solution; more specifically, a nickel layer with a thickness of 3-5 micrometers and a gold layer with a thickness of 0.05-0.10 micrometers are deposited sequentially at a temperature of 80-90°C.
[0066] In one embodiment, the method further includes step S6, performing post-processing cleaning on the circuit board after nickel-gold plating; further comprising the following steps:
[0067] The circuit board after immersion nickel-gold treatment is cleaned to remove residual chemicals and other contaminants; specifically, it is rinsed with deionized water and then dried to obtain the final product.
[0068] In one embodiment, the method further includes step S7, defect data feedback, and root cause improvement. Further, it includes the following steps:
[0069] S71. The system collects and statistically analyzes the quantity, density, distribution pattern, and location information of various defects (such as foreign objects, dents, and scratches) identified in the automatic visual inspection steps, and generates a visual defect analysis report.
[0070] S72. The defect analysis report is fed back to the relevant upstream production unit in real time through the factory manufacturing execution system; specifically:
[0071] If the analysis shows that there is a high incidence of foreign object defects on the copper surface, the feedback is sent to the solder mask workshop to suggest checking the condition of the developing line or the rollers in the tunnel oven.
[0072] If the analysis shows that the defects such as pits and scratches are concentrated, the feedback is sent to the lamination and pattern transfer workshop to prompt the checking of the uniformity of lamination parameter pressure or the cleanliness of the exposed film.
[0073] S73. The preceding process adjusts process parameters or maintains equipment based on feedback information to eliminate or reduce defects at the source, thereby forming a closed-loop quality control mechanism across processes and improving overall production yield.
[0074] This embodiment automatically collects and statistically analyzes various defect information identified by visual inspection, generates a visual analysis report, and feeds it back in real time to relevant upstream process units such as solder mask text, graphic transfer, or lamination through the factory manufacturing execution system. Based on this, the upstream processes adjust process parameters or perform equipment maintenance, thereby eliminating the root cause of defects at the source, improving the accuracy of defect response and the overall process efficiency, reducing the gold surface defect rate and production costs, and achieving continuous optimization of overall production yield through data-driven approaches.
[0075] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for improving defects in the gold surface of immersion nickel-gold plating, characterized in that, Includes the following steps: The copper surface of the circuit board is ground and sandblasted to obtain a circuit board that has undergone preliminary cleaning and activation. The circuit board that has undergone preliminary cleaning and activation is subjected to automatic visual inspection to scan and identify copper surface defects, resulting in a circuit board with completed defect marking. Based on the defect identifier, the circuit boards that have been identified as defective are inspected and sorted to obtain circuit boards that have been repaired or scrapped. The circuit boards that have undergone defect repair or scrapping are sandblasted to obtain clean and activated circuit boards. The clean and activated circuit board is subjected to immersion nickel-gold treatment to obtain the immersion nickel-gold treated circuit board.
2. The method for improving defects in the immersion nickel-gold surface according to claim 1, characterized in that, The circuit board, after initial cleaning and activation, is subjected to automated visual inspection to scan and identify copper surface defects. This is accomplished by comparing the captured copper surface image with a reference image in a standard product database.
3. The method for improving defects in the immersion nickel-gold surface according to claim 2, characterized in that, The identified defects include one or more of the following: foreign objects on the copper surface, dents, and scratches.
4. The method for improving defects in the immersion nickel-gold surface according to claim 1, characterized in that, The process of inspecting and sorting the circuit boards that have been identified as defective based on the defect identifiers specifically includes the following steps: Maintenance personnel confirm the defect images identified by automatic visual inspection, physically repair repairable defects, and mark and isolate the circuit board units containing irreparable defects.
5. The method for improving defects in immersion nickel-gold plating surface according to claim 4, characterized in that, The physical repair includes using grinding or wiping tools to remove foreign objects from the copper surface or smooth out minor scratches.
6. The method for improving defects in the immersion nickel-gold surface according to claim 4, characterized in that, The marking isolation is achieved by affixing tape to the irreparable circuit board unit as a resist marking.
7. The method for improving defects in immersion nickel-gold plating surface according to claim 1, characterized in that, The circuit boards that have completed defect repair or scrap sorting are subjected to sandblasting. The process parameters are configured to remove new oxide layers and fingerprints generated during the repair process. The sandblasting pressure or abrasive particle size is smaller than the sandblasting parameters used in the grinding and sandblasting of the copper surface of the circuit board.
8. The method for improving defects in immersion nickel-gold plating surface according to claim 1, characterized in that, It also includes the following steps: Collect and statistically analyze the types, quantities, and distribution of defects identified by automated visual inspection to obtain defect statistics.
9. The method for improving defects in immersion nickel-gold plating surface according to claim 8, characterized in that, It also includes the following steps: Collect and statistically analyze the types, quantities, and distribution data of defects identified by the automatic visual inspection to generate a defect analysis report; The defect analysis report is fed back to the upstream production system in the circuit board manufacturing process.
10. The method for improving defects in immersion nickel-gold plating according to claim 9, characterized in that, The feedback of the defect analysis report to the upstream production system in the circuit board manufacturing process specifically includes: If the defect analysis report indicates that copper surface foreign object defects are the main defect type, then the relevant information is fed back to the production system of the circuit board solder mask text process; If the defect analysis report indicates that pitting and scratches are the main defect types, then the relevant information is fed back to the production system of the circuit board lamination and pattern transfer process.