Solar cell lamination quality detection method

Abstract

This application discloses a method for inspecting the lamination quality of solar cells. The method includes: acquiring an electroluminescence image and an infrared thermal imaging image of a target solar cell, wherein the target solar cell is a solar cell obtained after the lamination process; comparing the electroluminescence image and the infrared thermal imaging image and identifying a target risk area, wherein the target risk area is a region in the target solar cell where both electroluminescence defects and infrared thermal imaging defects exist; and detecting the quality parameters of the intermetallic compound layer in the target risk area, wherein the quality parameters include the thickness and thickness uniformity of the intermetallic compound layer, which can accurately detect the quality of the IMC layer formed after lamination.

Description

Technical Field

[0001] This application relates to solar cell technology, and includes, but is not limited to, a method for detecting the lamination quality of solar cells. Background Technology

[0002] Back-contact solar cell technology is a high-efficiency photovoltaic technology. Its core feature is that all electrode grid lines are designed on the back of the cell, which makes the front of the cell completely unobstructed by grid lines. The lamination process of back-contact solar cells is as follows: the series-connected back-contact cell strings, encapsulating film, backsheet, and other materials are fed into a laminator. Under precisely controlled temperature, vacuum, and pressure conditions, the encapsulating film melts and flows to fill all gaps, and then cures to form a solid structure. Finally, the cell and the upper and lower layers are firmly bonded together to form a single encapsulated module.

[0003] In the lamination process of photovoltaic modules, the thickness of the intermetallic compound (IMC) layer is a key microscopic indicator determining the long-term reliability of the solder joints. Throughout the long service life of the module, continuous thermal cycling stress (e.g., diurnal and seasonal temperature differences) and potential mechanical stress (e.g., wind and snow loads) repeatedly act on the solder joints. IMC layers that are too thin or too thick can easily become the origin of microcracks. Therefore, accurately detecting the quality of the IMC layer formed after lamination has become an urgent technical problem to be solved. Summary of the Invention

[0004] In view of this, the solar cell lamination quality detection method provided in this application embodiment can accurately detect the quality of the IMC layer formed after lamination. The solar cell lamination quality detection method provided in this application embodiment is implemented as follows: In a first aspect, embodiments of this application provide a method for detecting the lamination quality of solar cells, the method comprising: Acquire electroluminescence images and infrared thermal images of the target solar cell, wherein the target solar cell is a solar cell obtained after a lamination process; The electroluminescent image and the infrared thermal imaging image are compared and the target risk area is identified. The target risk area is the area in the target solar cell where both electroluminescent defects and infrared thermal imaging defects exist simultaneously. The quality parameters of the intermetallic compound layer in the target risk area are detected, including the thickness and thickness uniformity of the intermetallic compound layer.

[0005] In some embodiments, comparing the electroluminescent image and the infrared thermal imaging image to identify the target risk area includes: The electroluminescent image and the infrared thermal image are superimposed to obtain the superimposed image; The region where the EL dark spot and IR hot spot overlap are identified from the superimposed image and designated as the target risk region.

[0006] In some embodiments, detecting the quality parameters of the intermetallic compound layer in the target risk region includes: Multiple target analysis points are selected from the target risk area, and the microstructure of the intermetallic compound layer at the multiple target analysis points is analyzed. The quality parameters of the intermetallic compound layer are determined based on the microstructure.

[0007] In some embodiments, the method further includes: The lamination quality of the target solar cell is determined based on the quality parameters of the intermetallic compound layer.

[0008] In some embodiments, determining whether the lamination quality of the target solar cell is qualified based on the quality parameters of the intermetallic compound layer includes: If the thickness of the intermetallic compound layer is greater than or equal to the first thickness threshold, the lamination quality is deemed unqualified.

[0009] In some embodiments, determining whether the lamination quality of the target solar cell is qualified based on the quality parameters of the intermetallic compound layer includes: If the thickness of the intermetallic compound layer is less than the second thickness threshold, the lamination quality is determined to be unqualified, wherein the second thickness threshold is less than the first thickness threshold.

[0010] In some embodiments, determining whether the lamination quality of the target solar cell is qualified based on the quality parameters of the intermetallic compound layer includes: If the thickness uniformity value of the intermetallic compound layer is less than a preset uniformity threshold, the lamination quality is deemed unqualified.

[0011] In some embodiments, determining whether the lamination quality of the target solar cell is qualified based on the quality parameters of the intermetallic compound layer includes: If the intermetallic compound layer is completely etched with silver and there are continuous cracks at the interface of the intermetallic compound layer, the lamination quality is deemed unqualified.

[0012] In some embodiments, the method further includes: Based on the test results, lamination parameter adjustment information is generated.

[0013] In some embodiments, generating lamination parameter adjustment information based on the detection results includes: When the thickness of the intermetallic compound layer is greater than the first thickness threshold, first lamination parameter adjustment information is generated. The first lamination parameter adjustment information includes: reducing the lamination preheating temperature, shortening the lamination heat preservation time, and optimizing the temperature curve peak of the laminator. When the thickness of the intermetallic compound layer is less than the second thickness threshold, second lamination parameter adjustment information is generated. The second lamination parameter adjustment information includes: increasing the lamination temperature and replacing the solder paste material with better wettability. If the thickness uniformity of the intermetallic compound layer is less than a preset uniformity threshold, a third lamination parameter adjustment information is generated. The third lamination parameter adjustment information includes checking the flatness of the laminator heating plate, the vacuum seal, and the uniformity of pressure application.

[0014] This application provides a method for inspecting the lamination quality of solar cells. By acquiring electroluminescence and infrared thermal imaging images of the target solar cell, comparing the electroluminescence and infrared thermal imaging images, and identifying target risk areas, a non-destructive scanning method can be used to scan the laminated solar cell module and quickly locate high-risk solder joints with increased series resistance or abnormal heating. Then, the quality parameters of the intermetallic compound layer in the target risk area are detected, which can accurately detect the quality of the IMC layer formed after lamination and effectively detect reliability risks caused by excessively thick or thin IMC layers. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with this application and, together with the specification, serve to explain the technical solutions of this application.

[0016] Figure 1 This is a flowchart illustrating a method for detecting the lamination quality of solar cells, provided in an embodiment of this application. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the specific technical solutions of this application will be further described in detail below with reference to the accompanying drawings of the embodiments of this application. The following embodiments are used to illustrate this application, but are not intended to limit the scope of this application.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0019] In the following description, references are made to “some embodiments,” which describe a subset of all possible embodiments. However, it is understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0020] It should be noted that the terms "first, second, third" used in the embodiments of this application are used to distinguish similar or different objects and do not represent a specific order of objects. It can be understood that "first, second, third" can be interchanged in a specific order or sequence where permitted, so that the embodiments of this application described herein can be implemented in an order other than that illustrated or described herein.

[0021] Please see Figure 1 , Figure 1 This is a flowchart illustrating a solar cell lamination quality testing method provided in an embodiment of this application, which may include the following implementation steps: S101. Acquire electroluminescence and infrared thermal imaging images of the target solar cell; S102. Compare the electroluminescent image and the infrared thermal imaging image and identify the target risk area; S103. Detect the quality parameters of the intermetallic compound (IMC) layer in the target risk area.

[0022] In step S101, electroluminescence (EL) imaging detection can be performed on the target solar cell to obtain an electroluminescence image of the target solar cell, and infrared thermal imaging (IR) detection can be performed on the target solar cell to obtain an infrared thermal image of the target solar cell. This allows for the rapid identification of potential risk points and precise spatial positioning without damaging the solar cell assembly. The target solar cell is a solar cell assembly obtained after a lamination process. For example, the EL and IR detection processes can be as follows: a test current is applied to the laminated solar cell assembly to perform an EL test and generate an EL image; then, the EL image is analyzed to identify all dark spots, dark lines, and areas of uneven brightness in the EL image; then, an infrared thermal imager is used to capture a temperature distribution map of the solar cell assembly (i.e., an IR image), and local hot spots in the IR image are identified.

[0023] In step S102, regions in the target solar cell where EL dark spots and IR hot spots highly overlap can be screened out, that is, regions in the target solar cell where both electroluminescence defects and infrared thermal imaging defects exist simultaneously.

[0024] In step S103, in this embodiment of the application, the quality parameters include, but are not limited to, the thickness and thickness uniformity of the intermetallic compound layer. To detect the quality parameters of the IMC layer in the target risk area, a sample containing the IMC layer can be prepared by sampling the target risk area. Then, a scanning electron microscope (SEM) can be used to observe the cross-section of the IMC layer. For example, a small sample containing a complete abnormal solder joint and a surrounding normal area as a control can be cut from the center of the target risk area using a precision cutting device (e.g., a precision cutting machine or laser cutting). The sampling process should ensure that the cutting path does not damage the solder joint interface to be observed. The cross-section is then subjected to a series of sandpaper grinding processes, followed by fine polishing with a diamond suspension until a mirror-like finish is achieved, ensuring that the IMC layer interface is free of scratches and trailing. To obtain better observation results, especially for thin IMC layers, the polished cross-section can also be subjected to ion polishing to remove the surface stress layer and obtain an atomically flat observation surface.

[0025] During SEM observation, the sample is placed in the SEM sample chamber and observed in backscattered electron mode. In this mode, materials with different average atomic numbers have different contrasts, making it possible to clearly distinguish the silver grid lines, IMC layer, and solder. At magnifications of 5000x or higher, the solder-silver grid line interface between abnormal and normal points is located.

[0026] This application provides a method for inspecting the lamination quality of solar cells. By acquiring electroluminescence and infrared thermal imaging images of the target solar cell, comparing the electroluminescence and infrared thermal imaging images, and identifying target risk areas, a non-destructive scanning method can be used to scan the laminated solar cell module and quickly locate high-risk solder joints with increased series resistance or abnormal heating. Then, the quality parameters of the intermetallic compound layer in the target risk area are detected, which can accurately detect the quality of the IMC layer formed after lamination and effectively detect reliability risks caused by excessively thick or thin IMC layers.

[0027] In one optional implementation, step S102 includes: Step 1) Overlay the electroluminescent image with the infrared thermal image to obtain the overlaid image; Step 2) Identify the area where the EL dark spot and IR hot spot overlap in the superimposed image as the target risk area.

[0028] In step 1), the EL and IR images of the same solar cell module can be superimposed to obtain the superimposed image. For better accurate positioning, the EL and IR images can be the same size.

[0029] In step 2), the area where the EL dark spot and IR hot spot overlap has the highest probability of having serious interface defects (such as excessive IMC causing a surge in resistance), and therefore can be marked as a "high-risk test point," that is, marked as a target risk area. The detection method of this application embodiment replaces the existing blind, random, and destructive sampling inspection, which can significantly improve the accuracy of locating high-risk solder joints, reduce misjudgments, improve detection efficiency, and save time and labor costs.

[0030] In one optional implementation, step S103 includes: Step A: Select multiple target analysis points from the target risk area and analyze the microstructure of the intermetallic compound layer at the multiple target analysis points; Step B: Determine the quality parameters of the intermetallic compound layer based on the microstructure.

[0031] In steps A and B, for example, multiple target analysis points can be randomly selected within the target risk area, such as selecting 2, 3, 4, 5, 6, 8, or 10 sampling points as target analysis points. When determining the quality parameters of the IMC layer, the thickness of the IMC layer at the target analysis points can be measured, the average thickness of the IMC layer at multiple sampling points can be calculated, and the continuity, uniformity, and presence of cracks or voids in the IMC layer can be observed. Simultaneously with SEM observation, energy dispersive spectroscopy (EDS) can be used to perform point or line scans of the IMC layer for elemental analysis. For example, multiple points can be selected on the IMC layer to analyze its elemental composition (mainly Ag and Sn, possibly containing Pb, Bi, etc.) to determine the IMC type (e.g., Ag3Sn); or, by drawing a line perpendicular to the interface across silver, the IMC layer, and solder, elemental distribution curves can be plotted to display the elemental diffusion gradient of the IMC layer.

[0032] In an optional implementation, the solar cell lamination quality detection method of this application further includes: The lamination quality of the target solar cell is determined based on the quality parameters of the intermetallic compound layer.

[0033] This step can be performed after S103. Since the quality parameters of the IMC layer can reflect the lamination quality of the target solar cell, this embodiment of the application can determine whether the lamination quality of the target solar cell is qualified based on the quality parameters of the IMC layer, further improving the accuracy of IMC layer quality detection.

[0034] In one optional implementation, the step of determining whether the lamination quality of the target solar cell is qualified based on the quality parameters of the intermetallic compound layer includes: If the thickness of the intermetallic compound layer is greater than or equal to the first thickness threshold, the lamination quality is deemed unqualified.

[0035] In this embodiment, if the thickness of the IMC layer is greater than or equal to a first thickness threshold, the brittleness of the IMC layer increases, and cracks are prone to rapid propagation under subsequent thermal cycling stress, leading to rapid solder joint failure. Therefore, the lamination quality is determined to be unqualified, thus accurately judging the quality of the IMC layer based on its thickness. The aforementioned first thickness threshold can be a value determined by a technician based on the normal upper limit of the IMC layer thickness, for example, it can be 2 μm.

[0036] In one optional implementation, the step of determining whether the lamination quality of the target solar cell is qualified based on the quality parameters of the intermetallic compound layer includes: If the thickness of the intermetallic compound layer is less than the second thickness threshold, the lamination quality is determined to be unqualified, wherein the second thickness threshold is less than the first thickness threshold.

[0037] In this embodiment, if the thickness of the IMC layer is less than the second thickness threshold, the metallurgical bonding at the IMC layer interface is insufficient, and the original bonding force is low. Under long-term thermomechanical stress, the interface itself becomes a weak point, easily leading to cracking and causing long-term reliability risks. Therefore, the lamination quality is determined to be unqualified, thus accurately judging the IMC layer quality based on its thickness. The aforementioned second thickness threshold can be a value determined by a technician based on the lower limit of the normal thickness of the IMC layer, for example, it can be 0.5 μm.

[0038] In one optional implementation, the step of determining whether the lamination quality of the target solar cell is qualified based on the quality parameters of the intermetallic compound layer includes: If the thickness uniformity value of the intermetallic compound layer is less than a preset uniformity threshold, the lamination quality is deemed unqualified.

[0039] In this embodiment of the application, if the thickness uniformity value of the IMC layer is less than the preset uniformity threshold, the brittleness of the IMC layer will also increase. Under subsequent thermal cycling stress, cracks are very likely to propagate rapidly, leading to rapid failure of the solder joint. Therefore, it is determined that the lamination quality is unqualified, and the quality of the IMC layer can be accurately judged based on the thickness uniformity of the IMC layer.

[0040] In one optional implementation, the step of determining whether the lamination quality of the target solar cell is qualified based on the quality parameters of the intermetallic compound layer includes: If the IMC layer is completely etched with silver and there are continuous cracks at the interface of the IMC layer, it indicates that there is a defect in the IMC layer. The brittleness of the IMC layer will also increase, and the lamination quality will be judged as unqualified.

[0041] In an optional implementation, the solar cell lamination quality detection method of this application further includes: Based on the test results, lamination parameter adjustment information is generated.

[0042] In this embodiment, based on the detection results, such as the thickness and uniformity of the IMC layer, lamination parameter adjustment information can be generated to adjust the lamination parameters of the subsequent solar cell module. This can accurately guide the adjustment of lamination parameters, thereby achieving control over the interface quality of the IMC layer and process optimization, and improving the long-term reliability of the solar cell module.

[0043] In one optional implementation, the step of generating lamination parameter adjustment information based on the detection results includes: Step A: When the thickness of the intermetallic compound layer is greater than the first thickness threshold, generate first lamination parameter adjustment information. The first lamination parameter adjustment information includes: reducing the lamination preheating temperature, shortening the lamination heat preservation time, and optimizing the temperature curve peak of the laminator. Step B: When the thickness of the intermetallic compound layer is less than the second thickness threshold, generate second lamination parameter adjustment information. The second lamination parameter adjustment information includes: increasing the lamination temperature and replacing the solder paste material with better wettability. Step C: If the thickness uniformity of the intermetallic compound layer is less than a preset uniformity threshold, generate third lamination parameter adjustment information. The third lamination parameter adjustment information includes: checking the flatness of the laminator heating plate, checking the vacuum seal of the laminator heating plate, and checking the uniformity of pressure application to the laminator heating plate.

[0044] In step A, an IMC layer thickness greater than or equal to a first thickness threshold indicates that the IMC layer is too thick. This suggests that the heat input during the current lamination preheating is too high, the heat input during the lamination process is too high, or the lamination process time is too long. At this point, first lamination parameter adjustment information can be generated, such as information to reduce the lamination preheating temperature, information to shorten the lamination insulation time, or information to optimize the peak temperature curve of the laminator. This allows for adjustments to the lamination parameters of the subsequent solar cell module, achieving control over the IMC layer interface quality and process optimization.

[0045] In step B, if the thickness of the IMC layer is less than the second thickness threshold, it indicates that the IMC layer is too thin. This suggests insufficient heat input, poor solder paste activity, or poor solder paste wetting. At this point, second lamination parameter adjustment information can be generated, such as information to increase the lamination temperature or information to replace the solder paste material with one that has better wetting properties. This allows for adjustment of the lamination parameters of the subsequent solar cell module, achieving control over the interface quality of the IMC layer and process optimization.

[0046] In step C, a thickness uniformity value of the IMC layer less than a preset uniformity threshold indicates poor thickness uniformity of the IMC layer. This suggests that the temperature field or pressure field during the welding process is uneven. At this point, second lamination parameter adjustment information can be generated. For example, information can be generated to check the flatness of the laminator heating plate, the vacuum seal of the laminator heating plate, or the uniformity of pressure application on the laminator heating plate. This allows for adjustment of the lamination parameters of the subsequent solar cell module, achieving control over the interface quality of the IMC layer and process optimization.

[0047] In addition, if the IMC layer is discontinuous, it indicates insufficient heat input, poor solder paste activity, or poor solder paste wettability. Second lamination parameter adjustment information can be generated to adjust the lamination parameters of subsequent solar cell modules, thereby controlling the interface quality of the IMC layer and optimizing the process.

[0048] It should be understood that the phrases "one embodiment," "an embodiment," or "some embodiments" mentioned throughout the specification mean that a specific feature, structure, or characteristic related to an embodiment is included in at least one embodiment of this application. Therefore, "in one embodiment," "in one embodiment," or "in some embodiments" appearing throughout the specification do not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. It should be understood that in the various embodiments of this application, the sequence numbers of the above-described processes do not imply a sequential order of execution; the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application. The sequence numbers of the above-described embodiments are merely for descriptive purposes and do not represent the superiority or inferiority of the embodiments. The descriptions of the various embodiments above tend to emphasize the differences between the various embodiments; their similarities or commonalities can be referred to mutually, and for the sake of brevity, they will not be repeated here.

[0049] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three kinds of relationships. For example, object A and / or object B can represent three situations: object A exists alone, object A and object B exist simultaneously, and object B exists alone.

[0050] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0051] The methods disclosed in the several method embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments.

[0052] The features disclosed in the several method embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments.

[0053] The above description is merely an embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for detecting the lamination quality of solar cells, characterized in that, The method includes: Acquire electroluminescence images and infrared thermal images of the target solar cell, wherein the target solar cell is a solar cell obtained after a lamination process; The electroluminescent image and the infrared thermal imaging image are compared and the target risk area is identified. The target risk area is the area in the target solar cell where both electroluminescent defects and infrared thermal imaging defects exist simultaneously. The quality parameters of the intermetallic compound layer in the target risk area are detected, including the thickness and thickness uniformity of the intermetallic compound layer.

2. The solar cell lamination quality testing method according to claim 1, characterized in that, The step of comparing the electroluminescent image and the infrared thermal imaging image to identify the target risk area includes: The electroluminescent image and the infrared thermal image are superimposed to obtain the superimposed image; The region where the EL dark spot and IR hot spot overlap are identified from the superimposed image and designated as the target risk region.

3. The solar cell lamination quality testing method according to claim 1, characterized in that, The detection of quality parameters of the intermetallic compound layer in the target risk area includes: Multiple target analysis points are selected from the target risk area, and the microstructure of the intermetallic compound layer at the multiple target analysis points is analyzed. The quality parameters of the intermetallic compound layer are determined based on the microstructure.

4. The solar cell lamination quality testing method according to claim 1, characterized in that, The method further includes: The lamination quality of the target solar cell is determined based on the quality parameters of the intermetallic compound layer.

5. The solar cell lamination quality testing method according to claim 4, characterized in that, The determination of whether the lamination quality of the target solar cell is qualified based on the quality parameters of the intermetallic compound layer includes: If the thickness of the intermetallic compound layer is greater than or equal to the first thickness threshold, the lamination quality is deemed unqualified.

6. The solar cell lamination quality testing method according to claim 5, characterized in that, The determination of whether the lamination quality of the target solar cell is qualified based on the quality parameters of the intermetallic compound layer includes: If the thickness of the intermetallic compound layer is less than the second thickness threshold, the lamination quality is determined to be unqualified, wherein the second thickness threshold is less than the first thickness threshold.

7. The solar cell lamination quality testing method according to claim 4, characterized in that, The determination of whether the lamination quality of the target solar cell is qualified based on the quality parameters of the intermetallic compound layer includes: If the thickness uniformity value of the intermetallic compound layer is less than a preset uniformity threshold, the lamination quality is deemed unqualified.

8. The solar cell lamination quality testing method according to claim 4, characterized in that, The determination of whether the lamination quality of the target solar cell is qualified based on the quality parameters of the intermetallic compound layer includes: If the intermetallic compound layer is completely etched with silver and there are continuous cracks at the interface of the intermetallic compound layer, the lamination quality is deemed unqualified.

9. The method for detecting the lamination quality of solar cells according to any one of claims 1 to 4, characterized in that, The method further includes: Based on the test results, lamination parameter adjustment information is generated.

10. The method for detecting the lamination quality of solar cells according to claim 9, characterized in that, The step of generating lamination parameter adjustment information based on the detection results includes: When the thickness of the intermetallic compound layer is greater than the first thickness threshold, first lamination parameter adjustment information is generated. The first lamination parameter adjustment information includes: reducing the lamination preheating temperature, shortening the lamination heat preservation time, and optimizing the temperature curve peak of the laminator. When the thickness of the intermetallic compound layer is less than the second thickness threshold, second lamination parameter adjustment information is generated. The second lamination parameter adjustment information includes: increasing the lamination temperature and replacing the solder paste material with better wettability. If the thickness uniformity of the intermetallic compound layer is less than a preset uniformity threshold, a third lamination parameter adjustment information is generated. The third lamination parameter adjustment information includes checking the flatness of the laminator heating plate, the vacuum seal, and the uniformity of pressure application.

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