Method for judging plating defects in electronic manufacturing

Abstract

The invention discloses a method for judging plating defects in electronic manufacturing, which comprises the following steps: respectively acquiring a first sample without film stripping after electroplating and a second sample without etching after film stripping for a target area with tin dissolving risk on a substrate; comparing and analyzing the microscopic surface topography difference of the first sample and the second sample at the same position point; and judging that the cause of the tin dissolving defect belongs to an electroplating link or a film stripping link based on the specific structure damage characteristics appearing in the second sample. According to the method, the problem that the tin dissolving defect caused by an electroplating link (uneven tin layer) or a film stripping link (liquid medicine erosion) cannot be accurately distinguished in the existing PCB manufacturing is solved.

Description

Technical Field

[0001] The present invention relates to the field of PCB technology, and in particular to a method for determining plating defects in electronic manufacturing. Background Art

[0002] During the pattern electroplating to alkaline etching process in PCB fabrication, areas such as the isolated annular ring are prone to "tin dissolution" defects (due to an excessively thin tin layer, resulting in ineffective etching protection). Existing identification methods primarily rely on empirical judgment or traditional cross-section analysis. Empirical methods are highly subjective and difficult to pinpoint the root cause of the problem (whether it is insufficient electroplated tin or erosion by the stripping solution). While cross-sectioning methods allow for observation, thickness measurements of small curved surfaces (such as the isolated annular ring) suffer from significant deviations, making it difficult to reliably capture subtle variations in the plating layer. Furthermore, data instability is affected by stripping solution fluctuations (batch-to-batch / time-to-time). This makes it difficult to effectively distinguish the responsible party for tin dissolution (electroplating or stripping), blurring the path to improvement and resulting in inconsistent quality between batches (one batch passing, the next batch dissolution). Therefore, a more objective, microscopic analysis method is urgently needed to clarify the cause of the defect. This paper proposes a method for identifying plating defects in electronics manufacturing. By comparing the microscopic surfaces of the electroplated and stripped (particularly the isolated annular ring) using SEM, the method clearly identifies the characteristic cracking of the tin layer after stripping. This method goes beyond the limitations of relying solely on thickness and provides direct evidence of structural damage. It can clearly distinguish whether it is an inherent defect in the coating or tin dissolution caused by excessive attack during the film stripping process, thereby accurately identifying the problem link and guiding effective improvement. Summary of the Invention

[0003] The technical solution of the present invention aims to at least partially address one of the technical problems in the related art. To this end, the main purpose of the present invention is to provide a method for determining plating defects in electronics manufacturing, aiming to address the problem in existing PCB manufacturing where it is difficult to accurately distinguish whether tin dissolution defects are caused by the electroplating process (uneven tin layer) or the film stripping process (chemical erosion).

[0004] To achieve the above object, the present invention provides a method for determining coating defects in electronic manufacturing, comprising the following steps: For a target area on the substrate at risk of tin dissolution, a first sample is obtained after electroplating but not stripped, and a second sample is obtained after stripping but not etched; Comparative analysis of microscopic surface morphology differences between the first sample and the second sample at the same location; Based on the specific structural damage characteristics that appeared in the second sample, it was determined that the cause of the tin dissolution defect was attributed to the electroplating process or the film stripping process.

[0005] As a further aspect of the present invention, the target area includes an isolated conductive structure with uneven current distribution.

[0006] As a further solution of the present invention, the isolated conductive structure is an independent hole ring or an independent pad on the PCB.

[0007] As a further solution of the present invention, the specific structural damage characteristics include local cracking, fissures or peeling of the tin layer after film stripping.

[0008] As a further solution of the present invention, the comparative analysis step is specifically as follows: if the second sample shows the specific structural damage feature but the first sample does not have this feature, it is determined that the tin dissolution is caused by the erosion of the chemical solution in the film stripping process; if both samples show discontinuous coating or abnormal thickness, it is determined that the tin dissolution is caused by defects in the coating in the electroplating process.

[0009] As a further solution of the present invention, the first sample and the second sample are prepared by cutting positions of the same risk area of ​​the substrate.

[0010] As a further solution of the present invention, the microscopic surface morphology analysis is observed using a scanning electron microscope.

[0011] As a further solution of the present invention, the method is applied to the diagnosis of tin dissolution defects in the process from pattern electroplating to alkaline etching in the positive film process of printed circuit boards.

[0012] As a further solution of the present invention, the defects in the electroplating process include insufficient thickness or lack of density of the tin layer caused by uneven current density.

[0013] As a further solution of the present invention, the defects in the film stripping process include tin layer corrosion caused by abnormal solution concentration, temperature or action time.

[0014] The beneficial effects of the present invention are as follows: This technical solution involves obtaining a first sample (pre-plated, unstripped) and a second sample (post-stripped, unetched) from target areas on the substrate at risk of tin dissolution. The samples are then carefully taken from the same location. Using a scanning electron microscope (SEM), the two samples are then compared for microscopic surface morphology differences. This approach accurately identifies specific structural damage features (such as localized cracking, crazing, or delamination) that appear only in the second sample (post-stripped, unetched). If the second sample is damaged while the first is intact, the tin dissolution is clearly caused by a defect in the stripping process, requiring adjustment of the chemical parameters. If both samples show discontinuous coatings or abnormal thickness, the problem is confirmed to be a defect in the electroplating process, requiring optimization of the electric field distribution. This solution addresses the issues of misjudgment, leading to incorrect improvement directions and batch-to-batch quality fluctuations in the pattern electroplating to alkaline etching process of printed circuit board positive manufacturing. It provides irreplaceable direct microscopic evidence for quickly pinpointing the root cause of tin dissolution in isolated conductive structures (electroplating or stripping), significantly improving process control efficiency and product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the technical solutions of the present invention or the technical solutions of the invention in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the technical solutions of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0016] Figure 1 It is a schematic block diagram of the main implementation steps of the present invention.

[0017] Figure 2 The difference in coating and the cracking of tin surface of independent hole ring before and after film stripping were observed by electron microscope in actual application of this scheme. DETAILED DESCRIPTION

[0018] as follows: Please see the attached Figure 1-2 , The main implementation steps are as follows: For target areas on the substrate at risk of tin dissolution, a first sample without stripping after electroplating and a second sample without etching after stripping are obtained. The differences in the microscopic surface morphology of the first and second samples at the same location are compared and analyzed. Based on the specific structural damage characteristics appearing in the second sample, it is determined that the cause of the tin dissolution defect is attributable to the electroplating process or the stripping process.

[0019] The technical principles are as follows: This technical solution sets the steps of obtaining the first sample that has not been stripped after electroplating and the second sample that has not been etched after stripping by setting the target area on the substrate where there is a risk of tin dissolution. This solves the problem that the existing technology cannot stably obtain effective detection objects (the traditional slicing method has a measurement deviation greater than the actual plating difference due to the small size and curved surface characteristics of isolated conductive structures with uneven current distribution such as independent hole rings), ensuring that the sample status is clear and highly comparable. By comparing and analyzing the differences in the microscopic surface morphology of the first sample and the second sample at the same position, and using scanning electron microscopy (SEM) observation (or other observation methods), this breaks through the subjectivity of existing empirical judgments and the limitations of traditional slicing methods that only rely on thickness data (the latter cannot distinguish whether the plating defects are congenital or later eroded), and instead captures specific structural damage characteristics (such as local cracking, cracking or peeling of the tin layer after stripping). Please refer to the attached Figure 2The large copper surface coating and the coating at the independent location are not much different at the microscopic level, but after stripping, the coatings are significantly different, and obvious tin surface cracks can be seen at the independent location. This direct display of microstructural changes makes the conclusion that the cause of the tin dissolution defect is attributed to the electroplating process or the stripping process more objective and reliable. In other words, when the second sample has specific structural damage while the first sample is intact, it clearly points to a defect in the stripping process (such as corrosion caused by abnormal solution concentration, temperature, or exposure time). If both samples show abnormalities (such as discontinuous coating or insufficient thickness), it is confirmed to be a defect in the electroplating process (such as lack of tin layer density due to uneven current density). Therefore, this technical solution accurately locates the root cause of tin dissolution in the specific responsible link (electroplating or stripping) in the printed circuit board positive process from pattern electroplating to alkaline etching, solving the problems of misjudgment, unclear improvement direction, and unstable quality between batches caused by detection errors and interference factors (such as fluctuations in stripping solution batches) in the existing technology.

[0020] In a preferred embodiment of the present invention, the target area includes an isolated conductive structure with uneven current distribution.

[0021] Specifically, target areas include isolated conductive structures with uneven current distribution (such as independent annular rings or independent pads). This is because such areas are prone to uneven current density due to electric field distortion during the electroplating process, resulting in locally thin or poorly dense coatings. Furthermore, their minutely curved surfaces cause significant deviations in thickness measurement using traditional slicing methods, making it difficult to accurately assess coating quality. Selecting such areas as key inspection areas directly targets weak points where tin dissolution defects are most likely to occur. Subsequent microscopic morphology comparisons can more sensitively capture structural evidence of defects from electroplating (congenital plating deficiencies) or film stripping (solvent erosion), thereby precisely pinpointing the root cause of the problem.

[0022] In a preferred embodiment of the present invention, the isolated conductive structure is an independent hole ring or an independent pad on the PCB.

[0023] In this technical solution, the isolated conductive structure is an independent hole ring or independent pad on the PCB. This is because these areas have the most uneven electric field distribution during graphic electroplating, and it is very easy for the tin layer to be too thin or loose due to uneven current density. In addition, the tiny curved surface characteristics make it difficult for traditional slicing methods to measure accurately, making them the risk point with the highest incidence of tin dissolution defects. Through microscopic morphology comparison, specific structural damage characteristics can be captured more efficiently, and it can be accurately distinguished whether the tin dissolution is caused by defects in the electroplating process or defects in the film stripping process.

[0024] A preferred embodiment of the present invention: the specific structural damage characteristics include local cracking, fissures or peeling of the tin layer after film stripping.

[0025] Specifically, these features will not appear in the first sample that has not been stripped after electroplating, but only appear in the second sample that has not been etched after stripping. This indicates that the tin layer was destroyed by the chemical attack during the stripping process rather than insufficient plating during electroplating. This intuitive structural evidence overcomes the error interference of traditional thickness measurement and can clearly lock the cause of tin dissolution to defects in the stripping process rather than defects in the electroplating process, avoiding misjudgment.

[0026] A preferred embodiment of the present invention is as follows: if the second sample shows specific structural damage characteristics while the first sample does not, it is determined that the tin dissolution is caused by erosion of the chemical solution during the film stripping process; if both samples show discontinuous coating or abnormal thickness, it is determined that the tin dissolution is caused by coating defects during the electroplating process.

[0027] The core purpose of this comparative analysis step in this technical solution is to establish an intuitive judgment standard. Specifically, if the second sample (after stripping) exhibits specific structural damage features (such as chipping or cracking) while the first sample (after electroplating) remains intact, it directly proves that the tin dissolution is caused by chemical erosion during the stripping process. If both samples show discontinuous coatings or abnormal thickness, defects in the electroplating process are confirmed to be the cause. This eliminates the uncertainty of single-stage testing and accurately distinguishes defects in the stripping process from those in the electroplating process.

[0028] In a preferred embodiment of the present invention, the first sample and the second sample are prepared by cutting positions of the same risk area of ​​the substrate.

[0029] In this solution, the first sample and the second sample are required to be prepared by cutting the position of the same risk area of ​​the substrate, which can ensure that the initial states of the two samples (such as graphic design, current distribution conditions) are completely consistent, avoid the introduction of interference variables due to position differences, and make the subsequent comparison results of the microscopic surface morphology differences at the same position point of the first sample that has not been stripped after electroplating and the second sample that has not been etched after stripping highly reliable, accurately reflect the real impact of defects in the stripping process or the electroplating process, and eliminate interference from other variables.

[0030] A preferred embodiment of the present invention: microscopic surface morphology analysis is performed using a scanning electron microscope.

[0031] Of course, the scanning electron microscope in this solution is a relatively conventional observation method, and other observation methods and devices can be used according to the actual process.

[0032] A preferred embodiment of the present invention is to apply the method to the diagnosis of tin dissolution defects in the process from pattern electroplating to alkaline etching in the positive film process of printed circuit boards.

[0033] Specifically, because independent hole rings and other areas are most likely to cause tin dissolution due to uneven current distribution and fluctuations in the stripping solution, and traditional methods are difficult to distinguish the causes of defects in the electroplating process from defects in the stripping process in this scenario, this solution accurately determines through microscopic morphology comparison and specifically solves the quality control problems unique to this process.

[0034] In a preferred embodiment of the present invention, defects in the electroplating process include insufficient thickness or lack of density of the tin layer caused by uneven current density.

[0035] In this solution, when it was found that both samples showed discontinuous coating or abnormal thickness, the core problem of the electroplating process (out-of-control current distribution) was directly located, providing a clear direction for improving the electric field uniformity in isolated conductive structure areas.

[0036] A preferred embodiment of the present invention: defects in the film stripping process include tin layer corrosion caused by abnormal solution concentration, temperature or action time.

[0037] In this technical solution, when the second sample shows specific structural damage characteristics (such as cracking) while the first sample is intact, the specific out-of-control parameters (concentration, temperature or time) of the film stripping process can be directly determined, providing a basis for precise adjustment of the solution and avoiding waste of resources.

[0038] The above description is only a preferred embodiment of the technical solution of the present invention, and does not limit the patent scope of the technical solution of the present invention. All equivalent structural transformations made by using the contents of the technical solution description and drawings of the present invention under the conception of the technical solution of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the technical solution of the present invention.

Claims

1. A method for determining coating defects in electronic manufacturing, characterized in that: The following steps are involved: S1. For a target area on a substrate at risk of tin dissolution, obtain a first sample that has not been stripped after electroplating and a second sample that has not been etched after stripping; S2. Comparative analysis of microscopic surface morphology differences between the first sample and the second sample at the same location; S3. Based on the specific structural damage characteristics appearing in the second sample, it is determined that the cause of the tin dissolution defect is attributed to the electroplating process or the film stripping process.

2. The method for determining coating defects in electronic manufacturing according to claim 1, wherein: The target area includes isolated conductive structures with uneven current distribution.

3. The method for determining coating defects in electronic manufacturing according to claim 2, wherein: The isolated conductive structure is an independent hole ring or an independent pad on the PCB.

4. The method for determining coating defects in electronic manufacturing according to claim 1, wherein: The specific structural damage characteristics include local cracking, cracking or peeling of the tin layer after film stripping.

5. The method for determining coating defects in electronic manufacturing according to claim 1, wherein: The comparative analysis step is specifically as follows: if the second sample shows the specific structural damage feature but the first sample does not have this feature, it is determined that the tin dissolution is caused by the erosion of the chemical solution in the film stripping process; if both samples show discontinuous coating or abnormal thickness, it is determined that the tin dissolution is caused by coating defects in the electroplating process.

6. The method for determining coating defects in electronic manufacturing according to claim 1, wherein: The first sample and the second sample are prepared by cutting positions of the same risk area of ​​the substrate.

7. The method for determining coating defects in electronic manufacturing according to claim 1, wherein: The microscopic surface morphology analysis is performed using a scanning electron microscope.

8. The method for determining coating defects in electronic manufacturing according to claim 1, wherein: The method is applied to the diagnosis of tin dissolution defects in the process from pattern electroplating to alkaline etching in the positive film process of a printed circuit board.

9. The method for determining coating defects in electronic manufacturing according to claim 1, wherein: The defects in the electroplating process include insufficient thickness or lack of density of the tin layer due to uneven current density.

10. The method for determining coating defects in electronic manufacturing according to claim 1, wherein: The defects in the film stripping process include tin layer corrosion caused by abnormal solution concentration, temperature or action time.

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