Defect position analysis method for MLCC short-circuit product

Abstract

The invention provides an MLCC short-circuit product defect position analysis method, and belongs to the technical field of multilayer ceramic capacitor failure analysis. The method comprises the following steps: carrying out rapid leakage current detection on MLCC products for 0.5-2 seconds, and screening out short-circuit products of which the leakage current is greater than a first preset threshold value; products with crack defects are eliminated through an acoustic scanning microscope; gradually applying increased direct-current voltage to the screened crack-free short-circuit product, monitoring leakage current in real time, and terminating the test when the sudden change amplitude of the current exceeds a second preset threshold value; then acoustic scanning is carried out on the protective cover surface and the cutting surface, and two-dimensional coordinates of defect points on the two surfaces are extracted; and calculating the three-dimensional coordinates of the defect in the MLCC through image registration and a spatial inversion algorithm. According to the method, the internal hidden short circuit defect can be identified and positioned in a non-destructive manner, the positioning precision and the analysis efficiency are improved, and the method is suitable for batch failure analysis and manufacturing process optimization.

Description

Technical Field

[0001] This application relates to the technical field of MLCC product testing, and particularly to a method for analyzing the defect position of MLCC short-circuited products. Background Art

[0002] With the gradual development of electronic devices towards miniaturization and lightweight, as an essential basic component for high-performance electrical equipment, multilayer ceramic capacitors (MLCCs) are widely used in electronic fields such as electronic vehicles and communication devices.

[0003] As Figure 1 shown, an MLCC is a monolithic capacitor composed of a series of laminated ceramic films and printed electrodes. As Figure 2 shown in Figure 1 / 3, the structure of the MLCC has particularity, that is, there is a height difference between the position where the electrodes face each other and the margin positions on both sides. Therefore, after the MLCCs are stacked and sintered, the electrodes at the margin positions inside the MLCC will not remain straight, but will Figure 4 extend and bend inwards, forming a margin area. The electrode position thickness in the margin area is much smaller than that in the area where the electrodes face each other, resulting in a thinning defect of the film in the area where the electrodes face each other near the margin. After sintering, short circuits are likely to occur in this area.

[0004] During the film stacking and forming process of the MLCC, the degree of electrode extension and bending is highly related to factors such as the film tensile strength, printed electrode thickness, stacking process, and voltage equalization process. Therefore, when a short-circuited MLCC is detected, it is necessary to analyze the position of internal defects in the short-circuited product.

[0005] In traditional technologies, first, an insulation resistance (IR) test is performed on the MLCC. After applying the rated voltage to the MLCC and charging (for 1 minute or 2 minutes), the leakage current is measured to calculate the insulation resistance value. For short-circuited products with unqualified insulation resistance, the DPA analysis (Destructive Physical Analysis) method is used to analyze the position of internal defects. Due to this, this analysis technology has the following defects:

[0006] (1) Low efficiency: Starting from sample preparation, through resin molding, grinding and polishing, etc., and then to metallographic analysis, it takes a long time (100 min);

[0007] (2) The internal facing area of the MLCC is relatively large, and it is difficult to analyze the defect points. It is necessary to grind 10 times or more for defect positioning, which takes a long time (about 200 min). The facing area of a small-sized MLCC product with a capacity of 0402 - 10 μF (length: 1 ± 0.2 mm / width: 0.5 ± 0.2 mm) reaches 210 mm 2, it is necessary to find a defect point of 0.002mm * 0.002mm, which is basically very difficult to find, and the probability of finding the defect point is only 5% - 10%. Summary of the Invention

[0008] Based on this, the present application provides a method for analyzing the defect position of MLCC short - circuit products that can solve the above - mentioned technical problems.

[0009] The above object of the present application is achieved by the following technical solutions:

[0010] The present application provides a method for analyzing the defect position of MLCC short - circuit products, and the method includes the following steps:

[0011] Place the MLCC products to be tested in a testing device for batch leakage current detection. The detection time is from 0.5 seconds to 2 seconds, and short - circuit products with leakage current greater than the first preset threshold are screened out;

[0012] Scan the short - circuit products through an acoustic scanning microscope, and screen out defective products without internal crack - like defects;

[0013] Connect the two outer electrode ends of the defective products to an adjustable DC regulated power supply with an output voltage range including 0 to 5V, gradually increase the output voltage of the DC regulated power supply, and monitor the leakage current value in real - time; when it is detected that the leakage current value jumps and its amplitude exceeds the second preset threshold, terminate the test;

[0014] Conduct acoustic scans on the protective cover surface and the cut surface of the defective products through an acoustic scanning microscope respectively to determine the two - dimensional spatial positions of the defect points on each surface;

[0015] Based on the position coordinates of the defect points on the protective cover surface and the cut surface, calculate the three - dimensional spatial coordinates of the defect points inside the MLCC, including the X - axis, Y - axis, and Z - axis positions.

[0016] In an optional embodiment, calculating the three - dimensional spatial coordinates of the defect points inside the MLCC includes the following steps:

[0017] Perform image pre - processing on the obtained protective cover surface image and cut surface image to enhance the image contrast and highlight the edge features of the area where the defect points are located;

[0018] Extract at least three groups of common feature points in the two images. The common feature points include the outer contour boundary of the MLCC, the edge of the metal electrode, or the intersection points of the internal layered structure;

[0019] Based on the extracted common feature points, establish a two - dimensional spatial transformation matrix required for image registration;

[0020] Perform an affine transformation or a projective transformation on one of the images to complete spatial registration with the other image in a unified coordinate system;

[0021] Identify the corresponding positions of the defect points in the two perspectives in the registered images, and calculate the three-dimensional spatial coordinates of the defect points, including the X, Y, and Z positions, through a spatial inversion algorithm.

[0022] In an optional embodiment, the steps of calculating the three-dimensional spatial coordinates of the defect points through a spatial inversion algorithm include:

[0023] Obtain the two-dimensional coordinates of the defect points in the registered cover surface image and cutting surface image;

[0024] Combine the structural parameters of the MLCC to establish a mapping relationship between the two-dimensional image coordinates and the three-dimensional spatial coordinates, where the structural parameters include the layer thickness and size calibration data;

[0025] Based on the orthographic projection geometric model, calculate the intersection point of the projection lines corresponding to the defect points in the two perspectives as the three-dimensional position of the defect point inside the MLCC.

[0026] In an optional embodiment, after calculating the three-dimensional spatial coordinates of the defect points, the following steps are further included:

[0027] Map the three-dimensional coordinates of the defect points of multiple defective products to a unified three-dimensional model of the MLCC to generate a three-dimensional spatial distribution map of the defect points, where the three-dimensional spatial distribution map is superimposed and displayed through the transparent modeled MLCC housing structure;

[0028] Perform three-dimensional rotation and projection observation on the three-dimensional spatial distribution map to analyze the aggregation area and distribution trend of the defect points.

[0029] In an optional embodiment, when generating the three-dimensional spatial distribution map of the defect points, the following steps are further included:

[0030] Calculate the three-dimensional spatial Euclidean distance between any two defect points;

[0031] When the three-dimensional distance between a certain defect point and an existing defect point is less than or equal to a preset distance threshold, determine that their spatial positions coincide;

[0032] Merge all defect points that meet the distance threshold condition into a representative defect point, and record the number of occurrences as the weight value of the defect point;

[0033] Visualize and enhance the defect point in the three-dimensional spatial distribution map according to the weight value.

[0034] In an alternative embodiment, the defect point is visually enhanced in the three-dimensional spatial distribution map according to the weight value, which specifically includes at least one of the following:

[0035] Set the display size, color depth, or transparency of the defect point according to the weight value.

[0036] In an alternative embodiment, after generating the three-dimensional spatial distribution map of the defect points, the following steps are further included:

[0037] Generate a statistical analysis result of the defect distribution according to the three-dimensional spatial distribution map, and the statistical analysis result includes one of the following:

[0038] A distribution frequency histogram of the defect points in the X, Y, and Z directions;

[0039] The concentration assessment of the defect points in a specific spatial region;

[0040] The position label of the high-frequency region of the defect points.

[0041] In an alternative embodiment, the steps of connecting the two external electrode ends of the defective product to an adjustable DC regulated power supply include:

[0042] Perform pre-drying treatment on the defective product;

[0043] Place the dried defective product at the corresponding station on the solder board, and the station is pre-coated with solder paste for connecting the external electrodes of the defective product;

[0044] Fix the defective product on the solder board through the reflow soldering process to achieve the conduction connection between its two external electrode ends and the adjustable DC regulated power supply.

[0045] In an alternative embodiment, the output voltage of the DC regulated power supply is gradually increased at a rate not greater than 1V / s until a leakage current jump is detected or the test voltage upper limit is reached.

[0046] In an alternative embodiment, the second preset threshold for the leakage current jump is 1 mA or above.

[0047] This application has the following beneficial effects:

[0048] The method for analyzing the defect position of MLCC short - circuit products in this embodiment can efficiently and accurately identify and locate the position of non - cracked short - circuit defects in MLCC products. By introducing a fast leakage current screening mechanism of 0.5 - 2 seconds, the rapid elimination of short - circuit products in a large number of products is realized, significantly shortening the detection cycle. After using an acoustic scanning microscope to screen out products with obvious structural cracks, it further focuses on non - structural manufacturing defects such as electrode printing and electrode offset, improving the pertinence and accuracy of subsequent analysis. By applying a gradually increasing DC voltage to the selected non - cracked defective products, internal latent defects can be gently activated, only triggering the initial conduction position, and at the same time, local punctate breakdown is formed around the defect point, which is conducive to the precise correspondence and three - dimensional positioning analysis of subsequent acoustic imaging results, effectively avoiding non - target breakdown and sample damage caused by one - time application of high voltage. At the same time, by performing acoustic scanning on the protective cover surface and the cut surface, combined with the geometric inversion algorithm, the precise calculation of the three - dimensional coordinates (X / Y / Z) of the defect inside the MLCC is completed. The overall solution has the advantages of high positioning accuracy, small operation damage, and being suitable for large - batch analysis, and can be widely applied to failure mode analysis, process defect traceability, and product quality control in the MLCC manufacturing process.

[0049] This application also uniformly maps the defect data of multiple defective products to a standard MLCC three - dimensional model, and a three - dimensional spatial distribution map of defect points can be generated, intuitively reflecting the distribution trend and concentrated area of defects inside the product, and assisting in identifying process weak points.

[0050] This application further performs visual enhancement processing according to the defect weight value, and can achieve significant marking of the defect hot - spot area. For example, by deepening the color, enlarging the size, or adjusting the transparency, the high - frequency defect positions are clearly visible in the three - dimensional view. Description of the Drawings

[0051] Figure 1 is a schematic structural diagram of an MLCC;

[0052] Figure 2-3 is a schematic diagram of the principle of height difference inside an MLCC;

[0053] Figure 4-5 is a schematic diagram of thinning defects of an MLCC;

[0054] Figure 6 is a schematic diagram of the steps of the method for analyzing the defect position of MLCC short - circuit products in an exemplary embodiment;

[0055] Figure 7 is a three - dimensional spatial distribution map of multiple MLCC short - circuit defect points in a batch;

[0056] Figure 8-10 is a schematic diagram of observing the three - dimensional spatial distribution map of MLCC short - circuit defect points from different angles;

[0057] Figure 11 Schematic diagram of the defects of short - circuit non - conforming products before implementing the method of the embodiment of the present application;

[0058] Figure 12 Schematic diagram of the defects of short - circuit non - conforming products after implementing the method of the embodiment of the present application;

[0059] Figure 13 Schematic diagram of scanning short - circuit products by an acoustic scanning microscope before implementing the method of the embodiment of the present application;

[0060] Figure 14 Schematic diagram of scanning short - circuit products by an acoustic scanning microscope after implementing the method of the embodiment of the present application;

[0061] Figure 15 Schematic diagram for comparing the method of the present application with the traditional technology. Detailed implementation manners

[0062] In order to make the above - mentioned objects, features and advantages of the present application more obvious and understandable, the following detailed description is made on the specific implementation manners of the present application. Many specific details are set forth in the following description in order to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0063] In addition, the terms "first", "first" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "first" can explicitly or implicitly include at least one of such features. In the description of the present application, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0064] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0065] In view of the technical problems in the background art, the present application provides a method for analyzing the defect positions of MLCC short - circuit products. As Figure 6 shown, in one embodiment, the method for analyzing the defect positions of MLCC short - circuit products of the present application includes the following steps:

[0066] S601: Place the MLCC products to be tested in a testing device for batch leakage current detection. The detection time is from 0.5 second to 2 seconds, and short-circuited products with leakage current greater than the first preset threshold are screened out.

[0067] In this embodiment, an existing testing device (such as the high-precision MLCC four-parameter testing mechanism in the existing patent CN218727718U) can be used to first perform batch testing on the MLCC products to be tested, and short-circuited products are screened out.

[0068] In traditional technologies, for leakage current testing, a rated voltage needs to be applied to the MLCC and charged for 1 - 2 minutes before measuring its leakage current, which takes a long time. In this embodiment, since the number of MLCC products in each batch may be as high as tens of thousands, therefore, in this embodiment, only a quick test within 0.5 second to 2 seconds is performed on the MLCC products, which can quickly screen out products with obvious short-circuit characteristics, thus greatly shortening the short-circuit analysis time for the entire batch.

[0069] Preferably, the detection time is 1 second. In this embodiment, short-circuited products refer to MLCC products with extremely high leakage current during static electrical performance detection, usually caused by internal defects (such as short circuits, metal migration, etc.). In this embodiment, through quick testing, short-circuited products with leakage current greater than the first preset threshold can be quickly screened out from a large number of MLCC products for further analysis of the defect location.

[0070] The first preset threshold in this embodiment can be determined according to the specific testing time and testing voltage. Among them, the testing voltage can be AC or DC. According to the testing time and testing voltage, the value range of the first preset threshold can be determined to determine the screening range of short-circuited products, so as to preliminarily screen out short-circuited products with obvious abnormalities by using the leakage current test within a short time.

[0071] S602: Scan the short-circuited products with an acoustic scanning microscope, and screen out defective products without internal crack-like defects.

[0072] An acoustic scanning microscope (C-SAM) is a non-destructive testing device that obtains information about internal defects of materials through ultrasonic reflection, and can image internal cracking, cavities and other structures. In this embodiment, the acoustic scanning microscope realizes the imaging of internal defects of the MLCC through the propagation and reflection of ultrasonic waves in the material.

[0073] The crack - like defects detected in acoustic scanning are commonly found in the mechanical damage of MLCCs (such as cutting cracks, sintering stress cracks, press - fitting cracks, etc.). For such defects, there are usually clear failure causes, such as external forces, cold cracks, sintering process stress, etc., and they do not belong to the "hidden defects" in manufacturing processes such as printing, electrode misalignment, and slurry penetration. Therefore, the core purpose of this method is not to confirm whether there is structural damage, but to locate the components that short - circuit under the premise of no cracking damage, focusing on more concealed manufacturing defects.

[0074] In this embodiment, by excluding the samples with these "known failure paths", it is ensured that the current mutation triggered during the subsequent electrical breakdown process is caused by "non - structural" reasons (such as electrode misalignment, short - circuit between layers, etc.), thereby improving the positioning accuracy.

[0075] S603: Connect the two outer electrode ends of the defective product to an adjustable DC regulated power supply with an output voltage range including 0 to 5V. Gradually increase the output voltage of the DC regulated power supply and monitor the leakage current value in real - time; when it is detected that the leakage current value jumps and its amplitude exceeds the second preset threshold, terminate the test.

[0076] Among them, the adjustable DC regulated power supply is a DC power supply device with continuously adjustable output voltage, which is used to apply a stable and controllable DC voltage to the object under test.

[0077] In this embodiment, connect the outer electrodes of the remaining defective products to an adjustable DC regulated power supply within the range of 0 - 5V, slowly increase the voltage and monitor the change of the leakage current in real - time. When a current mutation (such as instantaneously jumping from 10 μA to > 1 mA) is detected, record this voltage and abort the test.

[0078] During the process of gradually increasing the voltage, there already exists a local defect point with concentrated electric field strength inside the defective products selected from the short - circuited products (such as the distance between two electrodes being too close, ceramic pores, electrode burrs, slurry penetration, etc.). This point may not be fully conductive yet. However, as the externally applied voltage gradually rises, the local electric field strength continuously increases, and finally one of the following events may occur:

[0079] 1. Thermal breakdown or electrical breakdown of the micro - short - circuit path. As the voltage increases, the electric field reaches the critical strength at the weak dielectric (such as pores, corners, inter - layer separation areas), and then thermal breakdown (local heating and melting) or electron breakdown (electrons breaking through the ceramic dielectric) occurs, forming a permanent conduction path; at this time, the resistance drops suddenly → the current mutates.

[0080] 2. Discharge channels are generated between the electrodes (such as perforation, arc). Local electrode burrs and stacking offsets result in too small a distance. When the voltage rises to a certain extent, it may ionize in the air pores to form a discharge channel; the discharge will burn the dielectric, causing electrode short - circuit → the current mutates.

[0081] 3. Residual process defects are activated (such as silver migration). In the presence of moisture or impurity ions, increasing the voltage induces metal migration. The electrode material moves along the ceramic boundary under a high electric field and finally connects and conducts, resulting in a sharp increase in leakage current.

[0082] Before breakdown, the leakage current is almost stable or slowly increasing. At the moment of breakdown, the impedance of the local conduction path drops sharply, and the leakage current jumps from dozens of microamperes to several milliamperes instantaneously (typical mutation). Overall, it shows a sudden jump point on a smooth curve. This is an important technical basis for the present invention to utilize the leakage current mutation as the defect trigger point.

[0083] In this embodiment, by gradually increasing the voltage from 0V or a low voltage (such as +0.1 - 1V per second), the electric field gradient change received by the MLCC increases smoothly, which is convenient for observing the critical state of the defect point. The whole process of current change can be recorded, and the mutation point can be found. The damage risk of defective products is relatively low, and the area of non-defect points is prevented from being broken down in advance. At the same time, gradually increasing the voltage only triggers the initial conduction position of breakdown, forming a dot-like defect around the defect point, which is conducive to the precise correspondence with the dot-like defects in acoustic imaging.

[0084] If a high voltage such as the rated voltage is directly applied to the two outer electrode ends of the defective product for a long time, the electric field changes suddenly, and the breakdown behavior is uncontrollable. The direct damage risk of the defective product is extremely high, and it is easy to cause mis-breakdown, explosion, and thermal failure of the defective product. Acoustic scanning may only observe a large reflected area after the breakdown channel is ablated and cannot correspond to the original defect point.

[0085] In this embodiment, the second preset threshold can be determined according to the specific test product and test voltage, and its preferred setting is 1mA or above. The output voltage of the DC regulated power supply is preferably increased gradually at a rate not greater than 1V / s.

[0086] S604: Acoustically scan the protective cover surface and the cut surface of the defective product respectively through an acoustic scanning microscope to determine the two-dimensional spatial position of the defect point on each surface.

[0087] The protective cover surface refers to the encapsulation surface on the front of the MLCC product, usually the appearance inspection surface, corresponding to the top view direction of the capacitor. Sound waves can be vertically incident from this direction to detect the stacking state of the electrode layer. The cut surface refers to the plane obtained by cutting the MLCC from the side direction, exposing the longitudinal layer structure of the ceramic stack, which is suitable for observing the lateral behavior of interlayer extended defects (such as bridging, migration, layer deviation, etc.).

[0088] In this embodiment, an acoustic scanning microscope is set in the corresponding scanning direction so that the ultrasonic beam acts vertically on the protective cover surface and the cutting surface of the MLCC; when the ultrasonic wave passes through the dielectric layer and encounters a region of density discontinuity (such as cracking, voids, foreign objects, ablation marks, etc.), reflection or scattering will occur; the receiver records the echo intensity and time delay to form a two-dimensional image; the defect points are manifested as image features such as enhanced reflection, blurred edges, and chaotic echoes, and their two-dimensional coordinates can be directly located on the image.

[0089] S605: Based on the position coordinates of the defect points on the protective cover surface and the cutting surface, calculate the three-dimensional space coordinates of the defect points inside the MLCC, including the X-axis, Y-axis, and Z-axis positions.

[0090] The three-dimensional space coordinates refer to the space coordinate system composed of the X (width direction), Y (length direction), and Z (thickness direction) axes in which the defect points are located inside the MLCC with the product body as the reference system.

[0091] In this embodiment, since the protective cover surface and the cutting surface respectively provide the planar projections in the two-dimensional image (such as the X-Y and X-Z or Y-Z planes), the defect has a position coordinate in each of the two planes; after unifying the two images to the same coordinate system, the points on the two planes can be intersected and inverted into three-dimensional coordinates through geometric inversion methods (such as the intersection of perpendicular lines or the intersection of projection lines) to obtain the actual position of the defect in the three-dimensional space of the MLCC.

[0092] The method for analyzing the defect position of the short-circuited MLCC products in this embodiment can efficiently and accurately identify and locate the positions of non-crack short-circuit defects in MLCC products. By introducing a fast leakage current screening mechanism of 0.5 - 2 seconds, the rapid elimination of short-circuited products in a large number of products is realized, significantly shortening the detection cycle. After using the acoustic scanning microscope to screen out the products with obvious structural cracks, the focus is further on non-structural manufacturing defects such as electrode printing and electrode offset, improving the pertinence and accuracy of subsequent analysis. By applying a gradually increasing DC voltage to the selected non-crack defective products, the internal latent defects can be gently activated, only triggering the initial conduction position, and at the same time, local puncture breakdown is formed around the defect points, which is beneficial to the precise correspondence and three-dimensional positioning analysis of the subsequent acoustic imaging results, effectively avoiding non-target breakdown and sample damage caused by the one-time application of high voltage. At the same time, through acoustic scanning of the protective cover surface and the cutting surface and combining with the geometric inversion algorithm, the precise calculation of the three-dimensional coordinates (X / Y / Z) of the defect inside the MLCC is completed. The overall solution has the advantages of high positioning accuracy, small operation damage, and suitability for large-scale analysis, and can be widely applied to the failure mode analysis, process defect traceability, and product quality control in the MLCC manufacturing process.

[0093] In an alternative embodiment, calculating the three-dimensional spatial coordinates of the defect point inside the MLCC includes the following steps:

[0094] Perform image preprocessing on the obtained protective cover surface image and cutting surface image to enhance the image contrast and highlight the edge features of the area where the defect point is located;

[0095] Extract at least three groups of common feature points in the two images, where the common feature points include the outer contour boundary of the MLCC, the edge of the metal electrode, or the intersection points of the internal layered structure;

[0096] Based on the extracted common feature points, establish a two-dimensional spatial transformation matrix required for image registration;

[0097] Perform an affine transformation or a projection transformation on one of the images to complete spatial registration with the other image in a unified coordinate system;

[0098] Identify the corresponding positions of the defect point in the two perspectives in the registered image, and calculate the three-dimensional spatial coordinates of the defect point, including the X, Y, and Z positions, through a spatial inversion algorithm.

[0099] In this embodiment, image preprocessing refers to performing processing operations such as contrast enhancement, edge extraction, and filtering and noise reduction on the original acoustic scan image to improve the recognizability of the defect area where the defect point is located in the image.

[0100] Common feature points refer to structural identification points that can be recognized in both the protective cover surface image and the cutting surface image and have a spatial correspondence relationship, including the outer contour corner points of the MLCC, the electrode edge lines, the intersection points of the internal layered electrode structures, etc.

[0101] The two-dimensional spatial transformation matrix is a mathematical matrix used to describe the spatial correspondence relationship between two images, which can be established through an affine transformation or a projection transformation to achieve spatial registration between the images. Image registration is to unify two images from different angles into the same coordinate reference system, so that the positions of the same structure in different images can correspond one by one, providing a basis for subsequent spatial reconstruction.

[0102] In this embodiment, the spatial inversion algorithm analyzes the projection coordinates of the defect point in two orthogonal perspectives and derives the intersection point in the three-dimensional space to achieve three-dimensional positioning of the defect.

[0103] This embodiment utilizes the orthogonal two-dimensional projection information provided by the protective cover surface image and the cutting surface image, establishes a geometric transformation relationship between the two images through image registration, and then combines the structural parameters of the MLCC to inversely deduce the projection coordinates of the defect point in the two-dimensional image into the three-dimensional spatial coordinates inside the MLCC through a spatial inversion algorithm.

[0104] In a specific embodiment, the steps of calculating the three-dimensional spatial coordinates of the defect points by the space inversion algorithm include:

[0105] Obtain the two-dimensional coordinates of the defect points in the registered protective cover surface image and the cut surface image;

[0106] Combine the structural parameters of the MLCC to establish a mapping relationship between the two-dimensional image coordinates and the three-dimensional spatial coordinates, where the structural parameters include the layer thickness and the dimension calibration data;

[0107] Based on the orthogonal projection geometric model, calculate the intersection point of the projection lines corresponding to the defect points in the two perspectives as the three-dimensional position of the defect points inside the MLCC.

[0108] In this embodiment, the two-dimensional coordinates in the registered image refer to the position data of the defect points in their respective image coordinate systems in the registered protective cover surface image and the cut surface image, usually (x1, y1) and (x2, y2).

[0109] The structural parameters refer to the MLCC product body parameters used to convert the image coordinates into real physical coordinates, mainly including: the total size (length, width, thickness) of the ceramic body, the spacing between each layer, the number of layers, the electrode spacing, etc., for calibrating the image size to the real three-dimensional size.

[0110] This embodiment is based on the image shooting angle, the physical structure and dimension calibration of the MLCC ceramic body, and converts the image pixel position into the mathematical relationship of the position coordinates in the MLCC entity space, that is, the mapping relationship between the two-dimensional coordinates and the three-dimensional coordinates.

[0111] The orthogonal projection geometric model refers to taking two orthogonal perspectives (such as top view and side view) as the basis, regarding the two-dimensional projections of the defect points in different images as rays passing through the three-dimensional space, and determining the spatial position through the intersection points of these rays.

[0112] This embodiment uses the two orthogonal projection perspectives provided by the protective cover surface and the cut surface, respectively records the coordinates of the defect points in the two-dimensional image, converts the image coordinates into geometric rays in the three-dimensional reference system through the structural parameters, and then uses the spatial geometric model (such as the vertical plane projection line intersection point algorithm) to calculate the coordinates of the ray intersection, so as to determine the actual spatial position of the defect points inside the MLCC.

[0113] For better intuitive and unified overall analysis of the entire batch of MLCCs, in a preferred embodiment, after calculating the three-dimensional spatial coordinates of the defect points, the following steps are further included:

[0114] Map the three-dimensional coordinates of the defect points of multiple defective products to a unified three-dimensional model of MLCC to generate a three-dimensional spatial distribution map of the defect points, where the three-dimensional spatial distribution map is superimposed and displayed through the MLCC housing structure with transparent modeling;

[0115] Perform three-dimensional rotation and projection observation on the three-dimensional spatial distribution map to analyze the aggregation area and distribution trend of the defect points.

[0116] In this embodiment, after performing three-dimensional defect positioning on multiple short-circuit defective products in a batch, collect the three-dimensional spatial coordinates (X, Y, Z) of each defect point inside its MLCC, and uniformly map the three-dimensional coordinate data of each defect point to the same standard three-dimensional model of MLCC. With the help of transparent modeling technology, the defect points can be clearly visible in the structural model. Use a three-dimensional graphics engine to achieve multi-angle dynamic observation of the entire three-dimensional spatial distribution map, which is convenient for identifying systematic manufacturing problems such as high-incidence areas of defects, regular distribution trends, and interlayer offsets of defects, so as to guide product structure optimization or process improvement.

[0117] As Figure 7-10 shown, Figure 7 Fig. is the three-dimensional spatial distribution map of multiple MLCC short-circuit defect points in a batch, Figure 8 Fig. is the distribution of defect positions observed in the length-thickness direction, Figure 9 Fig. is the distribution of defect positions observed in the width-thickness direction, Figure 10 Fig. is the distribution of defect positions observed in the length-width direction. Through intuitive observation in different directions, the impact of the structural defects of MLCC stacking and forming can be accurately evaluated, providing an inspection means for the subsequent improvement and adjustment of the diaphragm tensile strength, printed electrode thickness, stacking process, and voltage equalization process.

[0118] If a specific process defect causes the defect points to be too concentrated, it is necessary to perform enhanced display processing on this. Therefore, in a preferred embodiment, when generating the three-dimensional spatial distribution map of the defect points, the following steps are further included:

[0119] Calculate the three-dimensional spatial Euclidean distance between any two defect points;

[0120] When the three-dimensional distance between a certain defect point and an existing defect point is less than or equal to a preset distance threshold, determine that they are spatially coincident;

[0121] Merge all defect points that meet the distance threshold condition into a representative defect point, and record the number of occurrences as the weight value of this defect point;

[0122] Visualize and enhance this defect point in the three-dimensional spatial distribution map according to the weight value.

[0123] Among them, the Euclidean distance is the straight-line distance between two points in three-dimensional space and is often used to measure the relative positional relationship between elements in space. When the three-dimensional Euclidean distance between two or more defect points is less than or equal to a set threshold, it is considered that these defect points are close enough in space, that is, their spatial positions coincide, and they can be classified as the same physical defect or the same regional defect.

[0124] In this embodiment, after merging multiple overlapping defect points, a central position point is selected as a representative defect point to represent the positions of all similar defect points in this area. The weight value is used to record the count value of how many original defect points are merged into a certain representative defect point, and is used to measure the occurrence frequency or aggregation severity of this point.

[0125] In this embodiment, according to the weight value of the defect points, in the three-dimensional space distribution diagram, visual highlighting is performed on them by means of color deepening, size enlargement, brightness enhancement, etc. to achieve visualization enhancement. Specifically, the visualization enhancement may include at least one of the following: setting the display size, color depth or transparency of the defect points according to the weight value.

[0126] In this embodiment, after the three-dimensional space distribution diagram of the defect points of the entire batch is constructed, there may be a situation where multiple defect points are highly concentrated in a specific area, especially more obvious when there are systematic process defects such as printing offset and interlayer bridging. In this embodiment, by calculating the three-dimensional Euclidean distance between the defect points, points with highly close positions are automatically identified, and these overlapping points are merged into a representative point. By assigning a weight value to the representative point and significantly marking it in the visualization interface, a hot spot highlighting effect is formed in the three-dimensional space distribution diagram. This enhanced display can help technicians more intuitively identify the problem concentration area, facilitating root cause analysis and process improvement.

[0127] In one embodiment, to further facilitate data analysis of the defect points, after generating the three-dimensional space distribution diagram of the defect points, the following steps are further included:

[0128] Generating a statistical analysis result of the defect distribution according to the three-dimensional space distribution diagram, and the statistical analysis result includes one of the following:

[0129] A frequency histogram of the distribution of defect points in the X, Y, and Z directions;

[0130] An evaluation of the concentration of defect points in a specific spatial area;

[0131] The position label of the high-frequency area of the defect points.

[0132] In a specific embodiment, the steps of connecting the two outer electrode ends of the defective product to an adjustable DC regulated power supply include:

[0133] Perform pre-drying treatment on the defective products;

[0134] Place the dried defective products at the corresponding stations on the solder board, and the stations are pre-coated with solder paste for connecting the external electrodes of the defective products;

[0135] Fix the defective products on the solder board through the reflow soldering process to achieve the conduction connection between its two external electrode ends and the adjustable DC regulated power supply.

[0136] MLCC may come into contact with cleaning liquid, coupling agent or humid air during the preliminary test or acoustic scanning. Therefore, drying can eliminate the moisture or residues on the surface of the external electrodes, prevent false soldering or oxidation during the reflow soldering process, and ensure good wetting and reliable connection between the external electrodes and the solder paste.

[0137] The solder board is a printed circuit board with several pads and preset circuit traces, which is used to temporarily or formally connect the defective products to be tested with the adjustable DC regulated power supply. The solder paste is used to melt and form solder joints during the reflow soldering process to achieve the electrical connection of the defective products.

[0138] In this embodiment, to achieve a reliable and low-impedance connection between the two external electrodes of the MLCC sample and the adjustable DC regulated power supply, the reflow soldering method in the standard surface mount technology (SMT) process is used for soldering. By pre-coating the solder paste at the corresponding stations on the solder board and placing the dried samples in place, a stable conduction connection can be achieved. The DC regulated power supply can be connected to the solder joints through a pre-arranged circuit for easy testing.

[0139] As Figure 11 shown, before implementing the method of this application embodiment, the defect of the short-circuit defective product is extremely small and not obvious. As Figure 13 shown, it is difficult to find its defect through an acoustic scanning microscope. As Figure 12 shown, after implementing the method of this application embodiment, the defect of the short-circuit defective product is more obvious. As Figure 14 shown, the defect points of the short-circuit defective product can be clearly found through an acoustic scanning microscope.

[0140] As Figure 15 shown, compared with the traditional scheme, the scheme of this application embodiment improves the analysis efficiency by more than 60%.

[0141] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0142] The above-described embodiments merely represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for analyzing the defect position of an MLCC short-circuit product, characterized in that The method includes the following steps: Place the MLCC products to be tested in a testing device for batch leakage current detection. The detection time is from 0.5 second to 2 seconds, and short-circuited products with leakage current greater than the first preset threshold are screened out; Scan the short-circuited products through an acoustic scanning microscope, and screen out defective products without internal crack-like defects; Connect the two outer electrode ends of the defective products to an adjustable DC regulated power supply with an output voltage range including 0 to 5V respectively. Gradually increase the output voltage of the DC regulated power supply and monitor the leakage current value in real time; when it is detected that the leakage current value jumps and its amplitude exceeds the second preset threshold, terminate the test; Perform acoustic scanning on the protective cover surface and the cut surface of the defective products through an acoustic scanning microscope respectively to determine the two-dimensional spatial positions of the defect points on each surface; Based on the position coordinates of the defect points on the protective cover surface and the cut surface, calculate the three-dimensional spatial coordinates of the defect points inside the MLCC, including the X-axis, Y-axis, and Z-axis positions.

2. The method for analyzing the defect position of the MLCC short circuit product according to claim 1, wherein: Calculating the three-dimensional spatial coordinates of the defect points inside the MLCC includes the following steps: Perform image preprocessing on the obtained protective cover surface image and cut surface image to enhance the image contrast and highlight the edge features of the area where the defect points are located; Extract at least three groups of common feature points in the two images. The common feature points include the outer contour boundary of the MLCC, the edge of the metal electrode, or the intersection points of the internal layered structure; Based on the extracted common feature points, establish a two-dimensional spatial transformation matrix required for image registration; Perform affine transformation or projective transformation on one of the images to complete spatial registration with the other image in a unified coordinate system; Identify the corresponding positions of the defect points in the two perspectives in the registered images, and calculate the three-dimensional spatial coordinates of the defect points, including the X, Y, and Z positions, through a spatial inversion algorithm.

3. The method for analyzing the defect position of the MLCC short-circuit product according to claim 2, wherein The steps of calculating the three-dimensional spatial coordinates of the defect points through a spatial inversion algorithm include: Obtain the two-dimensional coordinates of the defect points in the registered protective cover surface image and cut surface image; Combine the structural parameters of the MLCC to establish a mapping relationship between the two-dimensional image coordinates and the three-dimensional spatial coordinates. Among them, the structural parameters include layer thickness and size calibration data; Based on the orthogonal projection geometric model, calculate the intersection point of the projection lines corresponding to the defect points in the two perspectives as the three-dimensional position of the defect points inside the MLCC.

4. The method for analyzing the defect position of the MLCC short-circuited product according to any one of claims 1 to 3, characterized in that, After calculating the three-dimensional spatial coordinates of the defect points, the following steps are also included: Map the three-dimensional coordinates of the defect points of multiple defective products to a unified three-dimensional model of the MLCC to generate a three-dimensional spatial distribution map of the defect points, where the three-dimensional spatial distribution map is superimposed and displayed through the transparent modeling of the MLCC housing structure; Perform three-dimensional rotation and projection observation on the three-dimensional spatial distribution map to analyze the aggregation area and distribution trend of the defect points.

5. The method for analyzing the defect position of the MLCC short circuit product according to claim 4, characterized in that, When generating the three-dimensional spatial distribution map of the defect points, the following steps are also included: Calculate the three-dimensional spatial Euclidean distance between any two defect points; When the three-dimensional distance between a certain defect point and the existing defect points is less than or equal to the preset distance threshold, determine that they are spatially coincident; Merge all defect points that meet the distance threshold condition into a representative defect point, and record the number of occurrences as the weight value of the defect point; Visualize and enhance the defect point in the three-dimensional space distribution diagram according to the weight value.

6. The method for analyzing the defect position of the MLCC short-circuit product according to claim 5, wherein, Visualize and enhance the defect point in the three-dimensional space distribution diagram according to the weight value, specifically including at least one of the following: Set the display size, color depth or transparency of the defect point according to the weight value.

7. The method for analyzing the defect position of the MLCC short circuit product according to claim 4, characterized in that, After generating the three-dimensional space distribution diagram of the defect points, the following steps are further included: Generate a statistical analysis result of the defect distribution according to the three-dimensional space distribution diagram, and the statistical analysis result includes one of the following: Distribution frequency histograms of defect points in the X, Y, and Z directions; Concentration assessment of defect points in a specific spatial region; Location labels of high-frequency regions of defect points.

8. The method for analyzing the defect position of the MLCC short-circuit product according to claim 1, wherein, The steps of connecting the two outer electrode ends of the defective product to the adjustable DC regulated power supply include: Perform pre-drying treatment on the defective product; Place the dried defective product at the corresponding station on the solder board, and the station is pre-coated with solder paste for connecting the outer electrodes of the defective product; Fix the defective product on the solder board through the reflow soldering process to achieve the conduction connection between its two outer electrode ends and the adjustable DC regulated power supply.

9. The method for analyzing the defect position of the MLCC short-circuited product according to claim 1, wherein: The output voltage of the DC regulated power supply is gradually increased at a rate not exceeding 1V / s until a leakage current jump is detected or the test voltage upper limit is reached.

10. The method for analyzing the defect position of the MLCC short-circuited product according to claim 1, wherein: The second preset threshold for the leakage current jump is 1mA or above.

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