PCB electroless silver surface treatment champagne bubble inspection method and device, computer equipment and storage medium

Abstract

The invention discloses a PCB electroless silver surface treatment champagne bubble inspection method and device, computer equipment and a storage medium. The method comprises the following steps: manufacturing an electroless silver champagne bubble standard sheet; taking a part of the standard sheet as a to-be-detected sample, and performing silver deposition treatment to obtain a silver-deposited to-be-detected standard sheet; additionally taking a standard sheet as a calibration sample, carrying out micro-etching treatment before silver deposition, and then carrying out silver deposition treatment to obtain a silver deposition X-ray calibration standard sheet; carrying out solder paste printing and reflow soldering treatment to obtain a standard component to be detected and an X-ray calibration standard component; scanning the X-ray calibration standard component to confirm that the state of the X-ray equipment is normal; scanning the to-be-detected standard component, and detecting whether aggregation holes exist in the edge area of each bonding pad or not; slicing the to-be-tested standard component to obtain a slice inspection result; and judging whether the current silver deposition process parameters are qualified or not. By implementing the method provided by the invention, the whole process quality control from process verification to batch release can be realized.

Description

Technical Field

[0001] This invention relates to the field of PCB silver plating inspection technology, and more specifically to PCB silver plating surface treatment champagne bubble inspection method, apparatus, computer equipment and storage medium. Background Technology

[0002] Printed circuit boards (PCBs) are core components in the electronics manufacturing industry, and their surface treatment processes directly determine the reliability of subsequent surface mount technology (SMT) soldering. Immersion silver (ImAg), a widely used surface treatment method, is particularly suitable for high-end applications such as fine-line circuits, BGA / QFN packages, high-speed and high-frequency circuit boards, and automotive electronics due to its advantages including high surface flatness, excellent solderability, good high-frequency signal transmission performance, and moderate cost.

[0003] The basic principle of chemical silver immersion is based on the displacement reaction between copper and silver ions: copper (Cu) loses electrons and is oxidized and dissolved, while silver ions (Ag) dissolve. + The silver plating process involves the absorption of electrons to reduce the silver content to metallic silver, which is then deposited on the copper surface. However, in actual production, if residual adhesive, micro-etching residues, or organic contaminants are present on the copper surface, the local contamination layer may detach during the silver plating process, exposing fresh copper. This leads to differences in electrochemical activity across different areas of the copper surface, inducing galvanic corrosion in localized anodic areas. This corroded area is subsequently covered by a silver layer, forming oxide micro-pits (also known as "caves") approximately 1 μm in size. Furthermore, if the micro-etching is not properly controlled during the pretreatment stage, or if the silver plating reaction conditions are out of control (e.g., parameters such as reagent concentration, temperature, and time deviate from the process window), "hyper-corrosion" may occur, further exacerbating the density and depth of the micro-pits.

[0004] During subsequent SMT reflow soldering, the high temperature causes the silver layer to dissolve rapidly into the solder. The flux penetrates into the micro-pits and reacts with the residual oxides, generating gases such as CO2 and water vapor. Because the solder joint solidifies quickly, the gases cannot escape in time and are eventually trapped at the interface between the intermetallic compound (IMC, mainly Cu6Sn5) and the solder, forming planar micro-voids—commonly known in the industry as "champagne bubbles".

[0005] Although these microvoids are small in scale, they significantly reduce the effective wetting area between the pads and component leads. When the area of ​​microvoids exceeds a threshold, it can lead to a decrease in solder strength, and in severe cases, cause components to detach, ultimately resulting in electrical connection failure, reduced product reliability, or even functional failure.

[0006] While electroless silvering is widely used, the PCB industry still lacks standardized, quantifiable, and mass-production-compatible electroless silvering immersion welding inspection methods and judgment criteria. Existing testing methods largely rely on experience-based judgment or post-process failure analysis, failing to achieve effective process monitoring and risk warning at the forefront of the electroless silvering process. Therefore, there is an urgent need to develop an electroless silvering immersion welding inspection method that can accurately simulate actual welding conditions, is repeatable, and has clearly defined acceptance standards, in order to improve the welding reliability of electroless silvered boards and ensure product quality consistency. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method, apparatus, computer equipment and storage medium for inspecting champagne foaming of PCB silver-plated surface treatment.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: The champagne bubble test method for PCB electroless silver surface treatment includes: Design and fabricate a double-sided silver champagne foam standard sheet, wherein the top and bottom surfaces of the standard sheet are provided with multiple non-solder resist defined copper pads of different sizes; A portion of the standard sheets are taken as test samples and subjected to conventional immersion silver treatment on an immersion silver production line to obtain immersion silver test standard sheets; at least one of the standard sheets is taken as a calibration sample, and the copper surface of the pads of the calibration sample is micro-etched before immersion silver treatment, and then subjected to immersion silver treatment on the same immersion silver production line to obtain immersion silver X-ray calibration standard sheets. The immersion silver test standard sheet and the immersion silver X-ray calibration standard sheet are respectively subjected to solder paste printing and reflow soldering to obtain the test standard piece and the X-ray calibration standard piece; The X-ray calibration standard is scanned using an X-ray device to verify whether the device can identify a simulated hole of a preset size on the calibration standard, in order to confirm that the X-ray device is in normal working order. Under normal equipment conditions, the X-ray equipment is used to scan the standard component under test to detect whether there are champagne bubble-shaped aggregated voids in the edge area of ​​each pad, and the test results are obtained. When the test results meet the slicing verification triggering conditions, the test standard is sliced, and the void morphology at the silver-tin alloy layer interface is observed under a microscope to obtain the slicing inspection results. The current immersion silver process parameters are determined based on the results of the slice inspection; if they are qualified, PCB mass production is permitted using the same parameters.

[0009] This invention also provides a champagne bubble inspection device for PCB silver plating surface treatment, comprising: The fabrication unit is used to design and fabricate a double-sided silver champagne foam standard sheet, wherein the top and bottom surfaces of the standard sheet are provided with multiple non-solder resist defined copper pads of different sizes. The processing unit is used to take a portion of the standard sheet as a test sample, and after conventional immersion silver treatment in the immersion silver production line, obtain an immersion silver test standard sheet; and take at least one of the standard sheets as a calibration sample, perform micro-etching on the copper surface of the pads of the calibration sample before immersion silver treatment, and then perform immersion silver treatment in the same immersion silver production line to obtain an immersion silver X-ray calibration standard sheet. The printing and soldering unit is used to print solder paste and reflow soldering processes on the immersion silver test standard sheet and the immersion silver X-ray calibration standard sheet respectively to obtain the test standard and the X-ray calibration standard. The scanning verification unit is used to scan the X-ray calibration standard using an X-ray device to verify whether the device can identify a simulated hole of a preset size on the calibration standard, so as to confirm that the X-ray device is in normal condition. The scanning and detection unit is used to scan the standard part under test using the X-ray equipment under normal equipment conditions to detect whether there are champagne bubble-shaped aggregated voids in the edge area of ​​each pad and obtain the detection results. The slice observation unit is used to slice the standard part to be tested when the test result meets the slice verification trigger condition, and observe the void morphology at the silver-tin alloy layer interface under a microscope to obtain the slice inspection result. The judgment unit is used to determine whether the current immersion silver process parameters are qualified based on the slice inspection results; if qualified, PCB mass production is allowed according to the same parameters.

[0010] The present invention also provides a computer device, the computer device including a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the above-described method.

[0011] The present invention also provides a storage medium storing a computer program that, when executed by a processor, implements the above-described method.

[0012] The advantages of this invention compared to existing technologies are as follows: By designing double-sided standard sheets with non-solder resist defined copper pads of various sizes and introducing calibration samples that have undergone pre-defined micro-etching treatment, a representative simulated void structure can be formed after reflow soldering. This structure can realistically reflect the behavior of micro-pits caused by hyper-corrosion or contamination in actual production evolving into interface micro-voids during the soldering process, thus providing a clear reference standard for X-ray inspection. This gives previously difficult-to-observe microscopic champagne bubble defects a physical carrier that can be identified and quantified by X-ray equipment. Furthermore, by scanning the calibration standard, the detection capability of the X-ray equipment for voids of specific sizes can be verified in advance, ensuring that the detection system is in an effective working state. This avoids missed detections or misjudgments due to insufficient equipment sensitivity or improper parameter settings, improving the reliability and repeatability of the detection results. Furthermore, by correlating the actual void morphology (location, shape, area ratio, etc.) observed in the cross-section with the welding reliability, it is possible to scientifically determine whether the current immersion silver process (including pretreatment, immersion silver solution state, reaction time, etc.) is under control. Only under the premise of passing the inspection can it be allowed to enter mass production, thereby preventing SMT welding failures caused by champagne immersion from the source and improving product yield and long-term reliability.

[0013] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram illustrating an application scenario of the champagne bubble inspection method for PCB silver plating surface treatment provided in this embodiment of the invention. Figure 2 This is a schematic flowchart of the champagne bubble test method for PCB silver plating surface treatment provided in an embodiment of the present invention; Figure 3 A schematic block diagram of a champagne bubble inspection device for PCB silver plating surface treatment provided in an embodiment of the present invention; Figure 4 A schematic block diagram of a computer device provided for an embodiment of the present invention. Detailed Implementation

[0016] 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, not all, of the embodiments of the present invention. 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.

[0017] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0018] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0019] Please see Figure 1 and Figure 2 , Figure 1 This is a schematic diagram illustrating an application scenario of the champagne immersion inspection method for PCB silver plating surface treatment provided in this embodiment of the invention. Figure 2 This is a schematic flowchart illustrating the champagne bubble inspection method for PCB silver plating surface treatment provided in this embodiment of the invention. This champagne bubble inspection method for PCB silver plating surface treatment is applied to a server, which interacts with the terminal. Through standardized samples, calibration mechanisms, and tiered inspection logic, it achieves end-to-end quality control from process verification to batch release, demonstrating outstanding practicality, advancement, and industrial application value.

[0020] Figure 2 This is a schematic flowchart of the champagne bubble inspection method for PCB silver plating surface treatment provided in an embodiment of the present invention. Figure 2 As shown, the method includes the following steps S110 to S170.

[0021] S110. Design and fabricate a double-sided silver champagne foam standard sheet, wherein the top and bottom surfaces of the standard sheet are provided with multiple non-solder resist defined copper pads of different sizes. Specifically, the standard sheet is made using a copper-clad laminate (such as FR-4) that is the same as or similar to the actual PCB substrate, and has a double-sided copper-clad structure. Multiple circular or square copper pads of the non-solder mask defined (NSMD) type are formed on the top and bottom surfaces of the standard sheet through conventional pattern transfer and etching processes. These pads are arranged according to preset rules and include at least three different sizes (e.g., diameters of 0.25mm, 0.3mm, 0.4mm, etc.) to simulate the pad specifications corresponding to common BGA, QFN, and other packages in actual products. No solder mask layer is covered around any of the pads to ensure that solder paste can completely wet the exposed copper surface, thereby realistically replicating the interface reaction behavior during the SMT soldering process.

[0022] In other words, by setting up NSMD pads of multiple sizes, the welding thermodynamics and wetting kinetics conditions under different application scenarios can be fully covered, making the test results more representative and universal; the double-sided structure increases the information density of a single sample and improves the testing efficiency; at the same time, the use of materials and processes consistent with mass-produced boards ensures that the behavior of the standard sheet is highly consistent with the actual product, enhancing the credibility of the test results.

[0023] S120. Take a portion of the standard sheet as the test sample, and after conventional immersion silver treatment in the immersion silver production line, obtain the immersion silver test standard sheet; take at least one of the standard sheets as the calibration sample, perform micro-etching on the copper surface of the pad of the calibration sample before immersion silver treatment, and then perform immersion silver treatment in the same immersion silver production line to obtain the immersion silver X-ray calibration standard sheet. Specifically, a batch of the aforementioned standard films was divided into two groups: Samples to be tested: These samples are directly fed into the current silver immersion production line to be verified. The chemical silver immersion treatment is completed according to the conventional production parameters (including micro-etching time, silver immersion solution concentration, temperature, immersion time, etc.) to obtain "silver immersion test standard sheets".

[0024] Calibration Sample Set: At least one standard sheet is selected, and before entering the immersion silver line, its copper pad surface undergoes a controlled enhanced micro-etching treatment (e.g., extending the micro-etching time by 10-30 seconds, or increasing the activity of the micro-etching solution) to artificially induce slight but uniform over-etching of the copper surface, forming micro-pits of a preset depth (e.g., 0.8-1.2 μm). Subsequently, this calibration sample and the sample to be tested undergo immersion silver treatment simultaneously on the same immersion silver production line to obtain an "immersion silver X-ray calibration standard sheet".

[0025] In other words, the calibration sample, through pre-defined micro-etching, stably reproduces the typical "cavity" defects caused by pre-processing abnormalities. After subsequent silver immersion and reflow soldering, these cavities are transformed into interface voids with clear geometric features, serving as a "known positive control" for X-ray equipment identification. The test sample, on the other hand, reflects the actual state of the current process. Processing both on the same line eliminates batch-to-batch differences, ensures the consistency of the comparison benchmark, and improves the accuracy and repeatability of the inspection.

[0026] S130. The immersion silver test standard sheet and the immersion silver X-ray calibration standard sheet are respectively printed with solder paste and reflow soldered to obtain the test standard piece and the X-ray calibration standard piece. Specifically, using the same stencil, solder paste type (such as SAC305 lead-free solder paste), and SMT placement / reflow soldering process parameters (including heating slope, peak temperature, reflow time, etc.) as the customer's product, fully automated solder paste printing and reflow soldering are performed on the immersion silver test standard and the immersion silver X-ray calibration standard, respectively, to obtain the "test standard" and the "X-ray calibration standard". This process completely simulates the actual SMT production process, allowing the silver layer to fully dissolve into the solder at high temperature and promoting flux penetration into potential micro-pits, inducing gas generation and void formation.

[0027] In other words, by activating the champagne bubble formation mechanism in a realistic reflow soldering environment, micro-defects are made to manifest as detectable void structures at the interface between the IMC (Cu6Sn5) and the solder. This step is a crucial bridge connecting the quality of the immersion silver process with the reliability of the final solder joint, ensuring that the inspection results are directly related to the actual performance of the product, rather than merely remaining at the surface morphology level.

[0028] S140. Use an X-ray device to scan the X-ray calibration standard to verify whether the device can identify a simulated hole of a preset size on the calibration standard, so as to confirm that the X-ray device is in normal condition. Specifically, the X-ray calibration standard is placed in a high-resolution X-ray inspection device (such as a 2D / 3D AXI system), and the same voltage, current, magnification, and image processing algorithm as conventional inspection are set. The device is then observed to see if it can clearly identify clustered voids (usually distributed in a ring or semi-ring shape) on the calibration standard, formed by pre-defined micro-etching, located at the edge of the solder pads. If the device can consistently detect voids of the pre-defined size, the X-ray system is considered to be in normal working order; otherwise, device calibration or maintenance is required.

[0029] In other words, this step establishes a "functional verification" mechanism for the X-ray inspection system, resolving the problem of missed detections caused by equipment sensitivity drift, improper parameter settings, or image algorithm failures in existing technologies. By introducing known defect samples as a "benchmark," the detection capability is quantitatively confirmed, providing a reliable premise for subsequent judgment of the samples to be tested.

[0030] S150. Under normal equipment conditions, the X-ray equipment is used to scan the standard part to be tested to detect whether there are champagne bubble-shaped aggregated voids in the edge area of ​​each pad, and the test results are obtained. Specifically, after confirming that the X-ray equipment is functioning normally, a full-board scan is performed on the standard component under test, focusing on the edge areas of pads of various sizes. Using image grayscale differences and morphological analysis, the system identifies whether there are non-randomly distributed microvoids arranged in clusters. The system can automatically count the number of voids, the percentage of total area, and the distribution density, and compare them with preset thresholds (such as a single pad void area exceeding 10%).

[0031] In other words, champagne bubbles have specific spatial distribution characteristics (concentrated at the edge of the solder pad) and morphological characteristics (planar, aggregated, non-spherical), distinguishing them from ordinary pores or inclusions. By specifically identifying these characteristics, potential soldering reliability risks caused by abnormalities in the immersion silver process can be efficiently screened out, enabling quality early warning before mass production.

[0032] S160. When the test result meets the slicing verification trigger condition, the test standard is sliced ​​and the void morphology at the silver-tin alloy layer interface is observed under a microscope to obtain the slicing inspection result. Specifically, when the X-ray inspection results meet the preset "slicing verification trigger conditions" (e.g., the void density of a certain size pad exceeds a threshold, or multiple pads show inconsistent anomalies), samples from the corresponding locations are selected from the same batch of standard parts to be tested for metallographic section preparation. After grinding, polishing, and, if necessary, SEM / EDS or optical microscopy observation, the focus is on checking whether there are planar microvoids at the interface between the silver-tin alloy layer (i.e., the IMC layer) and the solder, and measuring their size, morphology, distribution, and correspondence with the original pits on the copper surface.

[0033] In other words, cross-section analysis, as the "gold standard" verification method, can directly confirm the authenticity of X-ray identification results and provide microscopic mechanism evidence (such as whether the voids originate from copper surface corrosion or whether they are accompanied by oxide residues). This destructive verification is only performed when necessary, balancing the rigor of inspection with cost control, forming an efficient hierarchical inspection model of "non-destructive initial screening + destructive confirmation".

[0034] S170. Determine whether the current immersion silver process parameters are qualified based on the slice inspection results; if qualified, PCB mass production is allowed according to the same parameters.

[0035] Specifically, based on the cross-section inspection results, if the percentage of void area at the interface is lower than the industry acceptable standard (e.g., <10%) and there are no continuous or penetrating defects, then the current immersion silver process parameters (including micro-etching intensity, immersion silver time, chemical maintenance status, etc.) are considered to be within the controllable range, and the process is deemed qualified. Otherwise, the parameters need to be adjusted and the inspection process repeated. Only after being deemed qualified can the same process parameters be used for mass immersion silver production of customer PCBs.

[0036] In other words, by directly linking inspection results to process release decisions, a shift from "experience-based release" to "data-driven release" has been achieved. This mechanism can effectively prevent batch welding failures caused by immersion silver over-corrosion, reduce customer on-site failure rates and after-sales costs, while providing quantitative basis for process window optimization and improving overall manufacturing reliability.

[0037] In one embodiment, the scanning magnification of the X-ray device is not less than 60 times, and the equivalent diameter of the simulated cavity in the X-ray calibration standard is not less than 15 μm.

[0038] Specifically, during X-ray inspection, the image magnification of the X-ray equipment is set to at least 60x (i.e., a combined effect of geometric and digital magnification) to ensure that micron-level structures can be clearly distinguished. Simultaneously, during the fabrication of X-ray calibration standards, the depth of the enhanced micro-etching and the silver immersion / reflow soldering parameters are controlled to ensure that the resulting interface voids have an equivalent diameter of not less than 15μm (calculated as an area equivalent circle). This dimension can be calibrated through pre-experimentation to ensure a clear grayscale contrast at 60x magnification.

[0039] In other words, champagne bubble cavities are typically tiny (5-30 μm). If the equipment's magnification is insufficient or the cavities are too small, they are difficult to distinguish from background noise, easily leading to missed detections. Setting a lower limit of 60x magnification and a lower limit of 15 μm cavities ensures that the detection system's sensitivity is within the effective range while avoiding sacrificing detection efficiency or introducing artifacts in pursuit of excessive resolution. This combination of parameters constitutes the minimum capability threshold for an X-ray system to reliably identify champagne bubbles, providing a reliable basis for the subsequent determination of the sample to be tested.

[0040] In one embodiment, the pad edge region refers to an annular region that is 25% of the width of the corresponding side length or diameter of the pad from the pad edge.

[0041] Specifically, for circular pads, an annular zone with an inner radius of 0.75R and an outer radius of R (where R is the pad radius) is drawn outward from the center of the pad; for square pads, an annular region with a width of 25% of the side length is drawn inside each side. This region is the "pad edge region," which serves as the key area of ​​focus for X-ray image analysis and void statistics.

[0042] In other words, the formation of champagne bubbles originates from localized corrosion of the copper surface during the immersion silver process. This type of corrosion is most likely to occur at the edges of the solder pads—where residual organic matter or uneven micro-etching is more likely to occur due to pattern etching, misalignment of solder mask openings, or cleaning dead zones, leading to concentrated galvanic corrosion. Limiting the analysis area to 25% of the edge not only focuses on high-risk areas and improves the targeting of detection, but also avoids data redundancy and misjudgment interference caused by full solder pad scanning, thus improving the signal-to-noise ratio and engineering practicality of defect identification.

[0043] In one embodiment, the slice verification trigger condition is: there are three or more voids with a diameter greater than 20 μm in the edge region of any pad, or the total coverage area of ​​voids in the edge region exceeds 10% of the area of ​​the region.

[0044] Specifically, during the X-ray image analysis phase, the system automatically identifies the number of voids, their individual diameters, and the total area within each pad edge region. The slice verification process is triggered when any of the following conditions are met: (1) there are 3 or more individual voids with a diameter exceeding 20 μm; (2) the sum of the projected areas of all voids exceeds 10% of the total area of ​​the edge region.

[0045] In other words, the triggering condition is established based on a large number of failure case statistics and reliability tests, taking into account both void size (large voids have a more significant impact on strength) and density (high coverage weakens the overall bonding force). Destructive slicing is only initiated when the defect reaches a critical level that may affect the reliability of the weld. This avoids the cost waste caused by excessive inspection and ensures that high-risk batches are not missed, realizing a risk-oriented hierarchical control strategy.

[0046] In one embodiment, the determination of the slice inspection results is performed at a magnification of 200x or higher. The qualification criteria are: all voids are located within the silver-tin alloy layer, with the interface between the silver-tin alloy layer and the copper layer as the judgment boundary, and any of the following conditions are met: Individual cavities are between 15-30 μm in size and there are fewer than 5 cavities in total; The void size is less than 15μm and the number is less than 20; At the same time, the width of all voids along the pad edge direction shall not exceed 25% of the width of the corresponding pad.

[0047] Specifically, after metallographic preparation of the triggered section sample, the IMC interface is observed under an optical microscope at a magnification of no less than 200x. The interface between the silver-tin alloy layer (i.e., Cu6Sn5 IMC) and the underlying copper is used as the baseline boundary for judgment; only voids located at this interface or within the silver-tin alloy layer are counted. Acceptance requires simultaneous fulfillment of the following conditions: The width of a continuous cluster of voids along the edge of the pad shall not exceed 25% of the width (or diameter) of the pad. And meet any of the following quantity / size combinations: Individual cavities are between 15-30 μm in size and the total number is less than 5. All voids are less than 15μm and the total number is less than 20.

[0048] In other words, this judgment rule scientifically distinguishes between "acceptable process variations" and "dangerous defects." Small-sized, low-quantity voids have limited impact on weld strength; however, large voids or dense clusters weaken interfacial bonding, especially when continuously distributed along the edges, easily becoming crack propagation paths. Limiting the cluster width to ≤25% of the pad size prevents the formation of penetrating weakening zones. 200x magnification ensures accurate differentiation of voids at the 10μm level, providing a microscopically reliable basis for the judgment and avoiding subjective misjudgments.

[0049] In one embodiment, the micro-etching treatment refers to using a micro-etching solution formed by mixing 98wt% sulfuric acid, 30wt% hydrogen peroxide and pure water in a preset ratio to perform micro-etching roughening treatment on the copper surface of the pads of the calibration sample.

[0050] Specifically, in the enhanced micro-etching step of the calibration sample, a micro-etching solution is used, which is a mixture of concentrated sulfuric acid (98wt%), industrial-grade hydrogen peroxide (30wt%) and deionized water in a volume ratio (e.g., H2SO4:H2O2:H2O = 4:1:5). The calibration sample is immersed in the solution at 25±2℃ for 30-60 seconds to achieve controllable roughening of the copper pad surface and form a uniform micro-concave structure.

[0051] In other words, this acidic hydrogen peroxide system possesses advantages such as strong oxidizing power, stable reaction rate, and uniform copper dissolution. It can accurately reproduce the hyper-corrosion state caused by excessive micro-etching, generating micropits with a depth of approximately 0.8-1.2 μm, which can then be transformed into typical champagne bubbles through immersion silver and reflow soldering. Compared to other micro-etching systems (such as sodium persulfate), this formulation is easier to control and has better repeatability, ensuring the consistency and reproducibility of defects in calibration standards, and providing stable and reliable positive samples for X-ray calibration.

[0052] In one embodiment, the solder paste printing refers to using a stencil with a thickness of 125μm, the stencil opening size being consistent with the pad size, and controlling the solder paste thickness to be 40μm to 70μm through stencil printing; the reflow soldering refers to performing one reflow soldering operation using a preset reflow soldering temperature profile.

[0053] Specifically, a 125μm thick laser-cut stencil is used, with its opening size perfectly matching the pads on the standard board (1:1 design). Solder paste is applied using a standard SMT printer, and the squeegee pressure and speed are controlled to ensure the actual deposited solder paste thickness falls within the range of 40-70μm. Subsequently, the board with the solder paste printed is sent to a reflow oven and undergoes a complete thermal cycle according to a verified lead-free reflow profile (e.g., preheating 150-180℃ / 90s, reflow peak 240-245℃ / 40-60s).

[0054] In other words, solder paste thickness directly affects the volume and wetting behavior of molten solder during reflow. Too thin a layer may result in insufficient flux and inadequate gas escape, while too thick a layer may mask interface defects. The 40-70μm range covers the practical application window for most BGA / QFN packages, ensuring that inspection conditions closely resemble real production. Furthermore, a single reflow simulates a conventional SMT process, avoiding the introduction of additional variables from multiple reflows. These standardized soldering parameters guarantee the repeatability and engineering representativeness of the champagne bubble formation process, enabling inspection results to directly guide mass production.

[0055] The aforementioned PCB silver-plated surface treatment champagne bubble inspection method, by designing double-sided standard sheets with non-solder resist defined copper pads of various sizes and introducing calibration samples that have undergone pre-defined micro-etching treatment, can form a representative simulated void structure after reflow soldering. This structure can realistically reflect the behavior of micro-pits caused by hyper-corrosion or contamination in actual production evolving into interface micro-voids during the soldering process, thus providing a clear reference standard for X-ray inspection. This gives the previously difficult-to-observe microscopic champagne bubble defects a physical carrier that can be identified and quantified by X-ray equipment. In addition, by scanning the calibration standard, the X-ray equipment's ability to detect voids of specific sizes can be verified in advance, ensuring that the inspection system is in an effective working state and avoiding missed detections or misjudgments due to insufficient equipment sensitivity or improper parameter settings, thereby improving the reliability and repeatability of the inspection results. Furthermore, by correlating the actual void morphology (location, shape, area ratio, etc.) observed in the cross-section with the welding reliability, it is possible to scientifically determine whether the current immersion silver process (including pretreatment, immersion silver solution state, reaction time, etc.) is under control. Only under the premise of passing the inspection can it be allowed to enter mass production, thereby preventing SMT welding failures caused by champagne immersion from the source and improving product yield and long-term reliability.

[0056] Figure 3 This is a schematic block diagram of a champagne bubble inspection device 300 for PCB silver plating surface treatment provided in an embodiment of the present invention. Figure 3As shown, corresponding to the above-described champagne bubble inspection method for PCB silver plating surface treatment, the present invention also provides a champagne bubble inspection apparatus 300 for PCB silver plating surface treatment. This champagne bubble inspection apparatus 300 includes a unit for performing the above-described champagne bubble inspection method for PCB silver plating surface treatment, and the apparatus can be configured in a server. Specifically, please refer to... Figure 3 The 300 PCB silver surface treatment champagne bubble inspection device includes: Fabrication unit 301 is used to design and fabricate a double-sided silver champagne foam standard sheet, wherein the top and bottom surfaces of the standard sheet are provided with multiple non-solder resist defined copper pads of different sizes. Processing unit 302 is used to take a portion of the standard sheet as a test sample, and after conventional immersion silver processing on the immersion silver production line, obtain immersion silver test standard sheet; take at least one of the standard sheets as a calibration sample, perform micro-etching on the copper surface of the pad of the calibration sample before immersion silver processing, and then perform immersion silver processing on the same immersion silver production line to obtain immersion silver X-ray calibration standard sheet. The printing and soldering unit 303 is used to print solder paste and reflow soldering process on the immersion silver test standard sheet and the immersion silver X-ray calibration standard sheet respectively to obtain the test standard and the X-ray calibration standard. The scanning verification unit 304 is used to scan the X-ray calibration standard using an X-ray device to verify whether the device can identify a simulated hole of a preset size on the calibration standard, so as to confirm that the X-ray device is in normal condition. The scanning detection unit 305 is used to scan the standard part to be tested using the X-ray equipment under normal equipment conditions, to detect whether there are champagne bubble-type aggregated voids in the edge area of ​​each pad, and to obtain the detection results. The slice observation unit 306 is used to slice the standard part to be tested when the test result meets the slice verification triggering condition, and observe the void morphology at the silver-tin alloy layer interface under a microscope to obtain the slice inspection result. The judgment unit 307 is used to determine whether the current immersion silver process parameters are qualified based on the slice inspection results; if qualified, PCB mass production is allowed according to the same parameters.

[0057] In one embodiment, the scanning magnification of the X-ray device is not less than 60 times, and the equivalent diameter of the simulated cavity in the X-ray calibration standard is not less than 15 μm.

[0058] In one embodiment, the pad edge region refers to an annular region that is 25% of the width of the corresponding side length or diameter of the pad from the pad edge.

[0059] In one embodiment, the slice verification trigger condition is: there are three or more voids with a diameter greater than 20 μm in the edge region of any pad, or the total coverage area of ​​voids in the edge region exceeds 10% of the area of ​​the region.

[0060] In one embodiment, the determination of the slice inspection results is performed at a magnification of 200x or higher. The qualification criteria are: all voids are located within the silver-tin alloy layer, with the interface between the silver-tin alloy layer and the copper layer as the judgment boundary, and any of the following conditions are met: Individual cavities are between 15-30 μm in size and there are fewer than 5 cavities in total; The void size is less than 15μm and the number is less than 20; At the same time, the width of all voids along the pad edge direction shall not exceed 25% of the width of the corresponding pad.

[0061] In one embodiment, the micro-etching treatment refers to using a micro-etching solution formed by mixing 98wt% sulfuric acid, 30wt% hydrogen peroxide and pure water in a preset ratio to perform micro-etching roughening treatment on the copper surface of the pads of the calibration sample.

[0062] In one embodiment, the solder paste printing refers to using a stencil with a thickness of 125μm, the stencil opening size being consistent with the pad size, and controlling the solder paste thickness to be 40μm to 70μm through stencil printing; the reflow soldering refers to performing one reflow soldering operation using a preset reflow soldering temperature profile.

[0063] It should be noted that those skilled in the art can clearly understand that the specific implementation process of the above-mentioned PCB silver surface treatment champagne bubble inspection device 300 and each unit can be referred to the corresponding description in the foregoing method embodiments. For the sake of convenience and brevity, it will not be repeated here.

[0064] The aforementioned PCB silver plating surface treatment champagne bubble inspection device 300 can be implemented as a computer program, which can perform, for example... Figure 4 It runs on the computer device shown.

[0065] Please see Figure 4 , Figure 4 This is a schematic block diagram of a computer device provided in an embodiment of this application. The computer device 500 can be a server, wherein the server can be a standalone server or a server cluster composed of multiple servers.

[0066] See Figure 4 The computer device 500 includes a processor 502, a memory, and a network interface 505 connected via a system bus 501. The memory may include a non-volatile storage medium 503 and internal memory 504.

[0067] The non-volatile storage medium 503 may store an operating system 5031 and a computer program 5032. The computer program 5032 includes program instructions that, when executed, cause the processor 502 to perform a champagne bubble inspection method for PCB silver surface treatment.

[0068] The processor 502 provides computing and control capabilities to support the operation of the entire computer device 500.

[0069] The internal memory 504 provides an environment for the operation of the computer program 5032 in the non-volatile storage medium 503. When the computer program 5032 is executed by the processor 502, the processor 502 can perform a champagne bubble inspection method for PCB silver surface treatment.

[0070] This network interface 505 is used for network communication with other devices. Those skilled in the art will understand that... Figure 4 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device 500 to which the present application is applied. The specific computer device 500 may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0071] The processor 502 is used to run a computer program 5032 stored in the memory to perform the following steps: Design and fabricate a double-sided immersion silver champagne standard sheet, wherein the top and bottom surfaces of the standard sheet are provided with multiple non-solder resist defined copper pads of different sizes; take a portion of the standard sheets as test samples, and after conventional immersion silver treatment on an immersion silver production line, obtain immersion silver test standard sheets; take at least one of the standard sheets as calibration samples, and before immersion silver treatment, perform micro-etching on the copper surface of the pads of the calibration sample, and then perform immersion silver treatment on the same immersion silver production line to obtain immersion silver X-ray calibration standard sheets; print solder paste and reflow solder the immersion silver test standard sheets and immersion silver X-ray calibration standard sheets respectively to obtain test standard parts and X-ray calibration standard parts; use X-ray equipment. The X-ray calibration standard is scanned to verify whether the equipment can identify simulated voids of a preset size on the calibration standard, thus confirming that the X-ray equipment is functioning normally. Under normal equipment conditions, the X-ray equipment is used to scan the standard under test to detect whether there are champagne bubble-shaped aggregated voids in the edge areas of each pad, obtaining the detection results. When the detection results meet the slicing verification trigger conditions, the standard under test is sliced, and the void morphology at the silver-tin alloy layer interface is observed under a microscope, obtaining the slicing inspection results. Based on the slicing inspection results, it is determined whether the current immersion silver process parameters are qualified. If qualified, PCB mass production is allowed according to the same parameters.

[0072] It should be understood that in the embodiments of this application, the processor 502 may be a central processing unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor.

[0073] It will be understood by those skilled in the art that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program includes program instructions and can be stored in a storage medium, which is a computer-readable storage medium. The program instructions are executed by at least one processor in the computer system to implement the process steps of the embodiments of the above methods.

[0074] Therefore, the present invention also provides a storage medium. This storage medium can be a computer-readable storage medium. The storage medium stores a computer program, wherein when executed by a processor, the computer program causes the processor to perform the following steps: Design and fabricate a double-sided immersion silver champagne standard sheet, wherein the top and bottom surfaces of the standard sheet are provided with multiple non-solder resist defined copper pads of different sizes; take a portion of the standard sheets as test samples, and after conventional immersion silver treatment on an immersion silver production line, obtain immersion silver test standard sheets; take at least one of the standard sheets as calibration samples, and before immersion silver treatment, perform micro-etching on the copper surface of the pads of the calibration sample, and then perform immersion silver treatment on the same immersion silver production line to obtain immersion silver X-ray calibration standard sheets; print solder paste and reflow solder the immersion silver test standard sheets and immersion silver X-ray calibration standard sheets respectively to obtain test standard parts and X-ray calibration standard parts; use X-ray equipment. The X-ray calibration standard is scanned to verify whether the equipment can identify simulated voids of a preset size on the calibration standard, thus confirming that the X-ray equipment is functioning normally. Under normal equipment conditions, the X-ray equipment is used to scan the standard under test to detect whether there are champagne bubble-shaped aggregated voids in the edge areas of each pad, obtaining the detection results. When the detection results meet the slicing verification trigger conditions, the standard under test is sliced, and the void morphology at the silver-tin alloy layer interface is observed under a microscope, obtaining the slicing inspection results. Based on the slicing inspection results, it is determined whether the current immersion silver process parameters are qualified. If qualified, PCB mass production is allowed according to the same parameters.

[0075] The storage medium can be any computer-readable storage medium capable of storing program code, such as a USB flash drive, portable hard drive, read-only memory (ROM), magnetic disk, or optical disk.

[0076] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0077] In the several embodiments provided by this invention, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For example, the division of each unit is merely a logical functional division, and there may be other division methods in actual implementation. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed.

[0078] The steps in the method of this invention can be adjusted, merged, or reduced in order according to actual needs. The units in the device of this invention can be merged, divided, or reduced according to actual needs. Furthermore, the functional units in the various embodiments of this invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0079] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, a terminal, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention.

[0080] 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 person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered 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 champagne bubble test method for PCB silver plating surface treatment, characterized in that, include: Design and fabricate a double-sided silver champagne foam standard sheet, wherein the top and bottom surfaces of the standard sheet are provided with multiple non-solder resist defined copper pads of different sizes; A portion of the standard sheets are taken as test samples and subjected to conventional immersion silver treatment on an immersion silver production line to obtain immersion silver test standard sheets; at least one of the standard sheets is taken as a calibration sample, and the copper surface of the pads of the calibration sample is micro-etched before immersion silver treatment, and then subjected to immersion silver treatment on the same immersion silver production line to obtain immersion silver X-ray calibration standard sheets. The immersion silver test standard sheet and the immersion silver X-ray calibration standard sheet are respectively subjected to solder paste printing and reflow soldering to obtain the test standard piece and the X-ray calibration standard piece; The X-ray calibration standard is scanned using an X-ray device to verify whether the device can identify a simulated hole of a preset size on the calibration standard, in order to confirm that the X-ray device is in normal working order. Under normal equipment conditions, the X-ray equipment is used to scan the standard component under test to detect whether there are champagne bubble-shaped aggregated voids in the edge area of ​​each pad, and the test results are obtained. When the test results meet the slicing verification triggering conditions, the test standard is sliced, and the void morphology at the silver-tin alloy layer interface is observed under a microscope to obtain the slicing inspection results. Determine whether the current immersion silver process parameters are qualified based on the results of the slice inspection; If the design is approved, mass production of PCBs with the same parameters is permitted.

2. The champagne bubble test method for PCB silver plating surface treatment according to claim 1, characterized in that, The X-ray device has a scanning magnification of not less than 60 times, and the equivalent diameter of the simulated cavity in the X-ray calibration standard is not less than 15 μm.

3. The champagne bubble test method for PCB silver plating surface treatment according to claim 1, characterized in that, The pad edge region refers to the annular area that is 25% of the width of the corresponding side length or diameter of the pad, located at a distance from the pad edge.

4. The champagne bubble test method for PCB silver plating surface treatment according to claim 1, characterized in that, The slice verification trigger condition is: there are 3 or more voids with a diameter greater than 20μm in the edge area of ​​any pad, or the total coverage area of ​​voids in the edge area exceeds 10% of the area of ​​the area.

5. The champagne bubble test method for PCB silver plating surface treatment according to claim 1, characterized in that, The determination of the slice inspection results is carried out at a magnification of 200x or higher. The acceptance criteria are: all voids are located within the silver-tin alloy layer, with the interface between the silver-tin alloy layer and the copper layer as the judgment boundary, and any of the following conditions are met: Individual cavities are between 15-30 μm in size and there are fewer than 5 cavities in total; The void size is less than 15μm and the number is less than 20; At the same time, the width of all voids along the pad edge direction shall not exceed 25% of the width of the corresponding pad.

6. The champagne bubble test method for PCB silver plating surface treatment according to claim 1, characterized in that, The micro-etching treatment refers to the use of a micro-etching solution formed by mixing 98wt% sulfuric acid, 30wt% hydrogen peroxide and pure water in a preset ratio to roughen the copper surface of the pads of the calibration sample through micro-etching.

7. The champagne bubble test method for PCB silver plating surface treatment according to claim 1, characterized in that, The solder paste printing refers to using a stencil with a thickness of 125μm, the stencil opening size being consistent with the pad size, and controlling the solder paste thickness to be 40μm to 70μm through stencil printing; the reflow soldering refers to performing one reflow soldering operation using a preset reflow soldering temperature profile.

8. A champagne bubble inspection device for PCB silver plating surface treatment, characterized in that, include: The fabrication unit is used to design and fabricate a double-sided silver champagne foam standard sheet, wherein the top and bottom surfaces of the standard sheet are provided with multiple non-solder resist defined copper pads of different sizes. The processing unit is used to take a portion of the standard sheet as a test sample, and after conventional immersion silver treatment in the immersion silver production line, obtain an immersion silver test standard sheet; and take at least one of the standard sheets as a calibration sample, perform micro-etching on the copper surface of the pads of the calibration sample before immersion silver treatment, and then perform immersion silver treatment in the same immersion silver production line to obtain an immersion silver X-ray calibration standard sheet. The printing and soldering unit is used to print solder paste and reflow soldering processes on the immersion silver test standard sheet and the immersion silver X-ray calibration standard sheet respectively to obtain the test standard and the X-ray calibration standard. The scanning verification unit is used to scan the X-ray calibration standard using an X-ray device to verify whether the device can identify a simulated hole of a preset size on the calibration standard, so as to confirm that the X-ray device is in normal condition. The scanning and detection unit is used to scan the standard part under test using the X-ray equipment under normal equipment conditions to detect whether there are champagne bubble-shaped aggregated voids in the edge area of ​​each pad and obtain the detection results. The slice observation unit is used to slice the standard part to be tested when the test result meets the slice verification trigger condition, and observe the void morphology at the silver-tin alloy layer interface under a microscope to obtain the slice inspection result. The judgment unit is used to determine whether the current silver immersion process parameters are qualified based on the slice inspection results. If the design is approved, mass production of PCBs with the same parameters is permitted.

9. A computer device, characterized in that, The computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the method as described in any one of claims 1 to 7.

10. A storage medium, characterized in that, The storage medium stores a computer program that, when executed by a processor, implements the method as described in any one of claims 1 to 7.

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