Test method, test piece and preparation method thereof

Abstract

The invention relates to the technical field of photovoltaic module testing, and provides a testing method, a testing piece and a preparation method of the testing piece. The test piece is used for testing the peel strength of a packaging adhesive film of a photovoltaic module, and comprises a back plate which comprises a first surface and a second surface which are opposite to each other; the supporting screen is located on the first face, and meshes of the supporting screen are exposed out of the partial area of the first face; the packaging adhesive film is located on the side, away from the back plate, of the supporting screen; the substrate is located on the side, away from the supporting screen, of the packaging adhesive film. The invention is at least beneficial to improving the success rate and the reliability of the peel strength test of the photovoltaic module packaging adhesive film.

Description

Cross-references to related applications

[0001] This application is a divisional application of the patent application filed on September 2, 2025, application number: 202511247835.1, entitled "Testing method, test piece and preparation method thereof". Technical Field

[0002] This disclosure relates to the field of photovoltaic module testing technology, and in particular to a testing method, a test piece, and a method for preparing the same. Background Technology

[0003] Solar power generation primarily relies on photovoltaic cells to directly convert solar energy into electrical energy. A photovoltaic module includes solar cells, a glass cover, backsheet material, and an encapsulating film. The encapsulating film serves several purposes, including supporting and securing the solar cells, maintaining high solar transmittance, isolating the cells from harmful environmental factors, ensuring the module's electrical insulation performance, and guaranteeing thermal conductivity.

[0004] Since the encapsulating film needs to form an effective bond with the glass or backsheet to ensure its good sealing effect, evaluating the adhesion performance of the encapsulating film to the glass or backsheet is of great engineering significance and application value for improving the reliability, weather resistance and overall life of photovoltaic modules. Summary of the Invention

[0005] This disclosure provides a testing method, a test piece, and a method for preparing the same, which at least helps to improve the success rate and reliability of peel strength testing of photovoltaic module encapsulation films.

[0006] According to some embodiments of this disclosure, one aspect of this disclosure provides a test piece for peel strength testing of encapsulating film in photovoltaic modules. The test piece includes: a backplate, including a first side and a second side facing each other; a support screen located on the first side, the mesh of the support screen exposing a portion of the first side; an encapsulating film located on the side of the support screen away from the backplate; and a substrate located on the side of the encapsulating film away from the support screen.

[0007] In some embodiments, the first surface includes a first region and a second region, the first region being disposed around the second region; the supporting screen includes: a first screen portion located in the first region; and a second screen portion located in the second region, wherein the mesh count of the first screen portion is greater than the mesh count of the second screen portion.

[0008] In some embodiments, the thickness of the first screen portion is greater than the thickness of the second screen portion.

[0009] In some embodiments, the thickness of the first screen portion decreases in the direction from the first region toward the second region.

[0010] In some embodiments, the area of ​​the first region accounts for 10% to 15% of the total area of ​​the first surface.

[0011] In some embodiments, the mesh openings of the first screen portion include a conical structure, wherein the aperture of the conical structure near the back plate is larger than the aperture of the side near the encapsulating film; the mesh openings of the second screen portion include a cylindrical structure.

[0012] In some embodiments, the mesh size of the first screen portion is 180 to 200 mesh, and the mesh size of the second screen portion is 150 to 180 mesh.

[0013] In some embodiments, the thickness of the supporting screen is 90µm to 120µm.

[0014] In some embodiments, the aperture of the mesh is 70µm to 80µm.

[0015] In some embodiments, the material of the support screen includes stainless steel.

[0016] According to some embodiments of this disclosure, another aspect of this disclosure provides a method for preparing a test piece, comprising: providing a backplate, the backplate including a first side and a second side opposite to each other; fixing a support screen to the first side, the mesh of the support screen exposing a portion of the first side; fixing an encapsulating film to the side of the support screen away from the backplate; fixing a substrate to the side of the encapsulating film away from the support screen; and laminating the backplate, the support screen, the encapsulating film, and the substrate together to obtain the test piece.

[0017] In some embodiments, the process parameters of the lamination step include: lamination temperature of 120℃~150℃ and lamination time of 455s~465s.

[0018] According to some embodiments of this disclosure, another aspect of this disclosure also provides a testing method, implemented using the test piece described in the above embodiments or the test piece prepared by the preparation method described in the above embodiments; the testing method includes: placing the test piece in a tensile testing machine; fixing the substrate of the test piece by a first clamp of the tensile testing machine; clamping one end of the composite structure composed of the back plate, the support screen and the encapsulating film of the test piece by a second clamp, and performing a tensile test, so that the encapsulating film causes the back plate and the support screen to peel off from the substrate, and measuring the peel strength between the encapsulating film and the substrate.

[0019] In some embodiments, prior to performing the tensile test, the method further includes performing one or more of the following on the test piece: a pressure cooker test, a damp heat aging test, a wet freeze test, and an ultraviolet aging test.

[0020] In some embodiments, the tensile speed during the tensile test is 95 mm / min to 105 mm / min.

[0021] The technical solutions provided in this disclosure have at least the following advantages: The test specimen provided in this embodiment incorporates a support screen located on one side of a backplate. The support screen has a mesh structure, and an encapsulating film is positioned between the support screen and the substrate. The support screen provides mechanical reinforcement to the backplate, preventing localized tearing or deformation during testing, thereby improving the test success rate. Simultaneously, the mesh structure of the support screen helps maintain the authenticity of water vapor permeation. Attached Figure Description

[0022] One or more embodiments are illustrated by way of example with corresponding pictures in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the pictures in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this disclosure or the conventional technology, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A partial cross-sectional schematic diagram of a test specimen provided in an embodiment of this disclosure; Figure 2 A schematic diagram of a supporting screen provided in an embodiment of this disclosure; Figure 3 A schematic diagram of a backplate provided in one embodiment of this disclosure; Figure 4 A schematic diagram of another structure of the support screen provided in an embodiment of this disclosure; Figure 5 A partial cross-sectional schematic diagram of a support screen provided in an embodiment of the present disclosure; Figure 6 This is another partial cross-sectional schematic diagram of a support screen provided in an embodiment of the present disclosure; Figure 7 A flowchart illustrating the steps of a method for preparing a test specimen according to an embodiment of this disclosure; Figure 8 A flowchart illustrating the steps of a testing method provided in an embodiment of this disclosure; Figure 9 This is a schematic diagram of a tensile test of a test specimen provided in an embodiment of the present disclosure.

[0024] Figure label: Back plate 10, support screen 11, encapsulating film 12, substrate 13, first surface 101, second surface 102, mesh 110, first region I, second region II, first screen portion 111, second screen portion 112. Detailed Implementation

[0025] After photovoltaic modules undergo long-term aging conditions such as damp heat, ultraviolet radiation, or thermal cycling, the backsheet material may degrade, leading to a decline in its mechanical properties and a tendency to become brittle. During peel strength testing, such brittle backsheets are prone to tearing, cracking, or localized deformation at stress concentration points because the edge areas are subjected to clamping forces and tensile loads. This prevents the completion of the peel process, resulting in interruptions in the peel strength test or data distortion, significantly reducing the success rate and reliability of the peel strength test.

[0026] To address or improve the aforementioned technical problems, this disclosure provides a test piece for peel strength testing of photovoltaic module encapsulation films. By embedding a support screen between the backsheet and the encapsulation film, the support screen mechanically reinforces the backsheet, preventing localized tearing or deformation during testing, thereby improving the success rate and reliability of the peel strength test. Furthermore, the support screen has a mesh structure, allowing the encapsulation film to fill the mesh during lamination, thus bonding the encapsulation film to the backsheet. This enhances the mechanical anchoring effect, increases the bonding strength between the backsheet and the support screen, and prevents interface cracking or delamination between the backsheet and the support screen during clamping or stretching, further improving the reliability of the test.

[0027] In the description of the embodiments of this disclosure, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary or secondary relationship of the indicated technical features. In the description of the embodiments of this disclosure, "multiple" means two or more, unless otherwise explicitly defined. Similarly, "multiple sets" refers to two or more sets (including two sets), and "multiple pieces" refers to two or more pieces (including two pieces).

[0028] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this disclosure. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] In the description of the embodiments of this disclosure, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0030] In the description of the embodiments of this disclosure, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the embodiments of this disclosure and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the embodiments of this disclosure. For example, if the device or element in the illustration is inverted, then the element described as "below," "under," "below," or "bottom" of other elements or features will be oriented "above" or "top" of said other elements or features. Therefore, the term "below" may, depending on the context in which the term is used, encompass both above and below orientations, which will be obvious to those skilled in the art. Materials may be oriented in other ways (e.g., rotated 90 degrees, inverted, flipped), and the spatial relative descriptive terms used herein may be interpreted accordingly.

[0031] In the description of the embodiments of this disclosure, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this disclosure according to the specific circumstances.

[0032] In the accompanying drawings corresponding to the embodiments of this disclosure, the thickness and area of ​​the layers are enlarged for better understanding and ease of description. Furthermore, when describing a component as "generally" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor on a portion of the edge of the entire surface.

[0033] In the description of the embodiments of this disclosure, when a component "includes" another component, other components are not excluded unless otherwise stated, and may be further included. The formation or placement of a second component above or on a first component, or on the surface of a first component, or on one side of a first component, may include embodiments where the first and second components are in direct contact, and may also include embodiments where an additional component may be placed between the first and second components, thereby preventing direct contact between the first and second components. For simplicity and clarity, various components may be drawn at different scales. In the drawings, some layers / components may be omitted for simplicity. Unless otherwise specified, the formation or placement of a second component on the surface of a first component refers to direct contact between the first and second components. The term "component" can refer to a layer, film, region, portion, structure, etc.

[0034] The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "component" is also intended to include the plural form unless the context clearly indicates otherwise. Components include layers, films, regions, or plates, etc.

[0035] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this disclosure to facilitate a better understanding of the disclosure. However, the technical solutions claimed in this disclosure can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0036] The test specimens provided in this disclosure are used for peel strength testing of the encapsulating film of photovoltaic modules.

[0037] refer to Figures 1 to 3 The test components include: a backplate 10, a support screen 11, an encapsulating film 12, and a substrate 13.

[0038] The back panel 10 includes a first surface 101 and a second surface 102 facing each other.

[0039] The backplate 10 provides electrical insulation, moisture and water resistance, mechanical support, and long-term protection against environmental stresses such as ultraviolet radiation, high temperature and humidity, dust, and chemical corrosion. The backplate 10 can be a fluorine-free, PET-free (polyethylene terephthalate) all-polyolefin backplate, a fluorine-containing, PET-free, fluorine-free, or fluorine-containing polyolefin backplate. The material of the backplate 10 is not limited here.

[0040] The support screen 11 is located on the first surface 101, and the mesh 110 of the support screen 11 exposes a portion of the first surface 101.

[0041] The support screen 11 is used to provide mechanical reinforcement and structural support for the back plate 10, preventing it from undergoing local deformation, tearing or breakage during clamping, stretching or other operations during the testing process.

[0042] In this embodiment, the support screen 11 only provides structural support and does not participate in chemical bonding or deep physical interlocking. It can truly reflect the adhesion force between the encapsulation film and the backing plate. The adhesion force error between the encapsulation film and the backing plate in the test piece provided in this embodiment is less than 5%, which can truly reflect the actual bonding performance.

[0043] Optionally, the support screen 11 can be made of a material with high tensile strength, good heat resistance, and chemical stability. For example, any one of stainless steel, polyethylene terephthalate (PET), polyimide (PI), glass fiber, or nickel alloy.

[0044] The support screen 11 has a mesh structure that provides necessary mechanical support for the backsheet 10 while maintaining unobstructed water vapor permeation paths on its surface. This structure ensures that water molecules can pass freely through the mesh area, thereby simulating the real water vapor transport environment of the actual photovoltaic module backsheet and maintaining the authenticity of the water permeation state.

[0045] Furthermore, the porosity of the support screen 11 is 80%~90%. This high porosity design, while ensuring the support function, maximizes the open channel area, making the water vapor transport path and permeation rate highly consistent with the actual component, thereby ensuring that environmental stress can be applied to the backing material more accurately and uniformly during aging tests. Experiments show that the water vapor transmission rate (WVTR) measured under these structural parameters deviates by less than 3% compared to the actual component, significantly improving the reliability and accuracy of the test results.

[0046] The encapsulating film 12 is located on the side of the supporting screen 11 away from the back plate 10, and also fills the mesh 110, and contacts a portion of the first surface 101 exposed by the mesh 110.

[0047] In some embodiments, the encapsulating film 12 partially fills the mesh 110, thereby bonding the encapsulating film 12 with the backplate 10, enhancing the anchoring effect, and thus improving the bonding strength of the backplate-encapsulating film interface, preventing the backplate 10 from breaking during clamping or stretching, and further improving the reliability of the test.

[0048] In some embodiments, the encapsulating film 12 can be an organic encapsulating film such as polyvinyl butyral (PVB) film, ethylene-vinyl acetate copolymer (EVA) film, polyvinyl octene elastomer (POE) film, or polyethylene terephthalate (PET) film. Alternatively, the encapsulating film 12 can also be an EP film, EPE film, or PVP film. Specifically, an EP film refers to a co-extruded film composed of stacked EVA and POE films; an EPE film refers to a co-extruded film formed by sequentially stacking EVA, POE, and EVA films; and a PVP film refers to a co-extruded film formed by stacking POE, EVA, and POE films. The co-extruded film can be prepared by sequentially extruding one or more raw materials onto another pre-made film during the film processing, or by bonding different types of pre-made films together.

[0049] The substrate 13 is located on the side of the encapsulating film 12 away from the supporting screen 11.

[0050] In some embodiments, the substrate 13 includes one of patterned glass, float glass, and a backsheet. The material of the substrate 13 can be selected according to the actual situation of the photovoltaic module to enable testing of the adhesion performance between the encapsulating film and the glass, and between the encapsulating film and the backsheet in the photovoltaic module, thereby improving the reliability of the photovoltaic module.

[0051] It is worth noting that, compared to the technical solution where the support screen is placed on the side of the backplate away from the encapsulating film, in this embodiment, the support screen with a mesh structure is placed between the backplate and the encapsulating film. This not only provides mechanical reinforcement to the backplate, preventing local tearing or deformation during testing and thus improving the success rate and reliability of the peel strength test, but also allows the encapsulating film to fill the mesh of the support screen, enabling the encapsulating film to bond with the backplate, enhancing the mechanical anchoring effect, and increasing the bonding strength between the backplate and the support screen. This not only helps prevent moisture from penetrating from the side edge interface of the test piece, reducing the risk of corrosion during damp heat aging, but also effectively prevents interface cracking or delamination between the backplate and the support screen during clamping or stretching, further improving the reliability of the test.

[0052] The embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings.

[0053] refer to Figures 3 to 4In some embodiments, the first surface 101 includes a first region I and a second region II, with the first region I surrounding the second region II; the supporting screen 11 includes: a first screen portion 111 located in the first region I; and a second screen portion 112 located in the second region II, wherein the mesh count of the first screen portion 111 is greater than the mesh count of the second screen portion 112.

[0054] Region I is located at the edge of the backplate 10. This edge area bears the clamping force and tensile load of the fixture, and is prone to tearing, cracking, or localized deformation at stress concentration points, thus requiring stronger mechanical support. Region I uses a high-mesh support screen 11. The larger the mesh count, the finer the mesh distribution, and the smaller the mesh diameter, the higher the mesh count support screen 11 can provide stronger mechanical support for the backplate 10, effectively suppressing tearing or deformation of the backplate 10 edge during testing and improving structural stability.

[0055] Region II is located at the center of backplate 10, and it uses a lower mesh size support screen. The smaller the mesh size, the sparser the mesh distribution, and the larger the pore size. From the perspective of water vapor transport efficiency and permeation path unobstructedness, larger pore sizes are more conducive to water vapor diffusion than smaller pore sizes. Therefore, using a lower mesh size support screen in Region II is more beneficial for maintaining a true water vapor permeation path.

[0056] It should be noted that the first region I and the second region II are defined for ease of description. Furthermore, in other embodiments, the mesh count of the support screen 11 may be the same in different regions; that is, the mesh count of the support screen 11 is uniformly distributed, and the mesh count of the first region I is the same as that of the second region II.

[0057] refer to Figure 5 In some embodiments, the thickness d1 of the first screen portion 111 is greater than the thickness d2 of the second screen portion 112.

[0058] Region I, located at the edge of the backplate 10, is the area where the fixture holds the components and where stress concentrates. Using a thicker first screen portion 111 significantly improves local stiffness and tear resistance, preventing damage or deformation of the backplate edge during testing. The thinner second screen portion 112 reduces rigid constraints on the central region while maintaining basic support functions, allowing the adhesive surface between the encapsulation film and the substrate to crack more easily during testing. The crack propagation pattern more closely resembles the actual debonding process in use, thus more accurately reflecting the peel strength between the encapsulation film and the substrate.

[0059] It should be noted that the reference Figure 6In other embodiments, the thickness of the first screen portion 111 and the thickness of the second screen portion 112 may also be the same, that is, the supporting screen 11 has a structure with a uniform overall thickness.

[0060] For example, in some embodiments, the mesh count of the first screen portion 111 is greater than the mesh count of the second screen portion 112, and the thickness of the first screen portion 111 is greater than the thickness of the second screen portion 112.

[0061] This design achieves functional zoning optimization by configuring differentiated structural parameters in different regions of the support screen. On the one hand, in the first region (I), the higher mesh count and greater thickness endow this part with higher structural rigidity and tear resistance, effectively suppressing stress concentration and local deformation caused by clamping or load transfer during testing, thus improving the overall mechanical stability and clamping reliability of the structure. On the other hand, in the second region (II), the lower mesh count and smaller thickness help reduce the obstruction to the flow of the encapsulating film, making it easier to fill and form effective anchoring during hot-pressing lamination, while maintaining a larger open channel area, which is conducive to the free penetration of environmental media such as water molecules, truly reflecting the moisture penetration state inside the photovoltaic module. Through the above zoning design, the support screen ensures structural integrity while taking into account the realism of interface anchoring behavior and environmental simulation, thereby significantly improving the reliability and accuracy of the test results.

[0062] In some embodiments, the thickness of the supporting screen 11 is 90um to 120um, for example, it can be 90um, 92um, 94um, 96um, 98um, 100um, 102um, 104um, 106um, 108um, 110um, 112um, 114um, 116um, 118um or 120um, etc.

[0063] The thickness d1 of the first screen portion 111 can be 106um~120um, for example, it can be 106um, 107um, 108um, 109um, 110um, 111um, 112um, 113um, 114um, 115um, 116um, 117um, 118um, 119um or 120um; the thickness d2 of the second screen portion 112 is 90um~105um, for example, it can be 90um, 91um, 92um, 93um, 94um, 95um, 96um, 97um, 98um, 99um, 100um, 101um, 102um, 103um, 104um or 105um.

[0064] By setting the thickness of the first screen portion 111 to be greater than that of the second screen portion 112, not only is sufficient mechanical support ensured for the edge area of ​​the back plate 10, preventing tearing or deformation of the back plate 10 during the peel strength test, but the functional integrity of the central area of ​​the test piece as the main peel behavior area is also preserved, ensuring the normal initiation and stable propagation path of the crack, and significantly improving the accuracy and reliability of the peel strength test.

[0065] In some embodiments, the thickness of the first screen portion 111 decreases in the direction from the first region I toward the second region II.

[0066] The first screen section 111 is not a uniform thickness structure, but rather its thickness gradually decreases along the direction from the first region I to the second region II, forming a smoothly transitioning gradient thickness structure. The edge region of the first screen section 111 is thicker to provide sufficient mechanical support and prevent edge tearing; the thickness gradually decreases inward to avoid abrupt changes in stiffness, reduce stress concentration, and make the stress on the entire test piece more uniform.

[0067] It should be noted that in other embodiments, the thickness of each part of the first screen portion 111 may also be the same, that is, the first screen portion 111 has a structure with a uniform overall thickness.

[0068] In some embodiments, the area of ​​the first region I accounts for 10% to 15% of the total area of ​​the first surface 101, for example, it can be 10%, 11%, 12%, 13%, 14% or 15%.

[0069] If the area of ​​the first region I is greater than 15%, the proportion of the area of ​​the first screen portion 111 to the total area of ​​the supporting screen 11 is too large. This results in the coverage of the first screen portion 111 extending excessively towards the center of the backplate 10, reducing the effective area of ​​the second region II. Since the area corresponding to the second region II in the test piece is the main area for crack initiation and stable propagation in the peel strength test, its compressed area may inhibit the normal peeling behavior between the encapsulation film and the substrate interface, affecting the controllable initiation and propagation path of the crack, thereby reducing the repeatability and representativeness of the test results. If the area of ​​the first region I is less than 10%, the proportion of the area of ​​the first screen portion 111 to the total area of ​​the supporting screen 11 is too small. This results in insufficient mechanical support of the supporting screen 11 for the edge area of ​​the backplate 10, making the backplate 10 prone to tearing or deformation. The first region I has a moderate proportion (10%~15%), meaning that the area of ​​the first screen part 111 accounts for a moderate proportion of the total area of ​​the supporting screen 11. This not only ensures that the edge area of ​​the back plate 10 receives sufficient mechanical support, preventing the back plate 10 from tearing or deforming during the test, but also preserves the functional integrity of the central area of ​​the test piece as the main peeling behavior area, ensuring the normal initiation and stable propagation path of the crack, and significantly improving the accuracy and reliability of the peel strength test.

[0070] In some embodiments, the mesh openings of the first screen portion 111 include a conical structure, wherein the aperture of the conical structure on the side near the back plate 10 is larger than the aperture on the side near the encapsulating film 12; the mesh openings of the second screen portion 112 include a cylindrical structure.

[0071] The encapsulating film 12 is located above the support screen 11. During the lamination process, it softens and flows when heated. Under pressure, some of the adhesive fills into the mesh of the support screen 11 and forms physical contact and adhesion with the back plate surface exposed through the mesh.

[0072] In the first region I, after the encapsulating film 12 enters the mesh of the conical structure, due to the geometric feature that the aperture is larger on the side of the channel closer to the back plate 10 and smaller on the side closer to the encapsulating film 12, a mechanical anchoring structure resembling a "mushroom head" or "nail head" is formed after curing. When subjected to tensile force, the encapsulating film 12 needs to overcome greater pull-out resistance to be pulled out of the mesh, thereby significantly improving the bonding strength between the back plate and the supporting screen, effectively preventing interface cracking or delamination between the back plate and the supporting screen during testing, and further improving the reliability of the test.

[0073] Region II employs a cylindrical mesh structure with a consistent pore size along the thickness direction, which facilitates the free diffusion of water molecules and reduces moisture transport resistance. In damp heat aging tests, moisture can smoothly penetrate to the encapsulation film-backsheet interface, more realistically simulating the moisture intrusion behavior and interface degradation process of actual components during long-term outdoor operation, significantly improving the accuracy of peel strength tests.

[0074] It should be noted that in other embodiments, the mesh openings of the first screen portion 111 and the second screen portion 112 can be of the same shape, that is, the mesh opening shape of the supporting screen 11 is uniform.

[0075] In some embodiments, the mesh openings of the supporting screen 11 can also be regular or irregular geometric shapes such as hexagonal, square, trapezoidal, gourd-shaped, etc.

[0076] In some embodiments, the mesh size of the first screen portion 111 is 180 to 200 mesh, for example, it can be 180 mesh, 182 mesh, 184 mesh, 186 mesh, 188 mesh, 190 mesh, 192 mesh, 194 mesh, 196 mesh, 198 mesh or 200 mesh; the mesh size of the second screen portion 112 is 150 to 180 mesh, for example, it can be 150 mesh, 152 mesh, 154 mesh, 156 mesh, 158 mesh, 160 mesh, 162 mesh, 164 mesh, 166 mesh, 168 mesh, 170 mesh, 172 mesh, 174 mesh, 176 mesh, 178 mesh or 180 mesh.

[0077] refer to Figure 4 The first screen section has a relatively dense distribution of 111 mesh holes, corresponding to smaller hole diameters and higher structural rigidity. This effectively improves the local deformation and tear resistance of the back plate, prevents tearing or deformation of the back plate edge during testing, and improves the success rate and reliability of peel strength testing.

[0078] The second screen section 112 has a relatively sparse mesh distribution and a larger pore size. From the perspective of water vapor transmission efficiency and permeation path unobstructedness, a larger pore size is more conducive to water vapor diffusion. That is, the second screen section 112 is more conducive to maintaining the true water vapor permeation path.

[0079] In some embodiments, the mesh size is 70µm to 80µm, for example, it can be 70µm, 71µm, 72µm, 73µm, 74µm, 75µm, 76µm, 77µm, 78µm, 79µm, or 80µm. By setting the mesh size of the support screen to 70µm to 80µm, it is ensured that the support screen has good mechanical strength while maintaining a real water vapor permeation path.

[0080] In some embodiments, the first screen portion 111 and the second screen portion 112 are configured with different apertures depending on the functional area.

[0081] refer to Figure 4The first screen section 111 has a mesh size k1 of 70µm~75µm, which is a relatively small mesh size range. This results in a higher mesh density and a more compact structure, which enhances the mechanical interlocking effect between the encapsulating film and the backplane, significantly improving the bonding strength between the backplane and the supporting screen. This prevents tearing or delamination of the interface between the backplane and the supporting screen due to clamping or stretching during peel strength testing. The second screen section 112 has a mesh size k2 of 75µm~80µm, which is relatively large. The larger mesh size reduces the diffusion resistance of water molecules, helping to maintain the penetration path of water vapor to the encapsulating film-backplane interface during damp heat aging testing, thus improving the realism of environmental simulation.

[0082] In some embodiments, the material supporting the screen 11 includes stainless steel.

[0083] Optionally, the support screen can be made of 304 stainless steel or 316L stainless steel. Stainless steel has high tensile strength, good corrosion resistance, good ductility, and a stable geometric structure, making it suitable for high-temperature and high-humidity aging test environments. By selecting stainless steel as the material for the support screen, not only is the overall performance of the test piece improved in terms of mechanical strength, environmental resistance, and structural stability, but it also takes into account low cost and process adaptability, combining practicality and economy.

[0084] The test specimen provided in this disclosure introduces a supporting screen, which mechanically reinforces the backplate, preventing local tearing or deformation of the backplate during testing, thereby improving the success rate and reliability of the peel strength test. Furthermore, it allows the encapsulating film to fill the mesh of the supporting screen, bonding the encapsulating film to the backplate and enhancing the mechanical anchoring effect. This improves the bonding strength between the backplate and the supporting screen, helping to prevent moisture intrusion from the test specimen's side edges, reducing the risk of corrosion during humid aging, and effectively preventing interface cracking or delamination between the backplate and the supporting screen during clamping or stretching, further improving test reliability. In addition, based on the functional requirements of the supporting screen in different areas of the test specimen, its thickness, mesh shape, mesh count, and aperture parameters are differentiated to ensure sufficient mechanical strength in the edge areas for structural support, while maintaining a moisture permeation path comparable to that of the actual component in the central area, thus balancing structural stability and environmental simulation realism.

[0085] Accordingly, another embodiment of this disclosure also provides a method for preparing a test specimen, which can be used to manufacture the test specimens provided in the above embodiments. The method for preparing a test specimen according to another embodiment of this disclosure will be described in detail below with reference to the accompanying drawings. For parts that are the same as or corresponding to the previous embodiment, please refer to the corresponding descriptions of the foregoing embodiments; detailed descriptions will not be repeated below.

[0086] refer to Figure 7The method for preparing the test specimen provided in this disclosure includes at least the following steps: S101: Provides a back panel, which includes a first side and a second side facing each other.

[0087] The first side is used to form an adhesive interface with the encapsulating film, and the second side is an air surface.

[0088] S102: Fix the support screen to the first surface, with the mesh of the support screen protruding from a portion of the first surface.

[0089] Align and attach the support screen to the first side of the backplate, ensuring that its mesh structure exposes a portion of the first side, forming a channel for the encapsulation film to penetrate.

[0090] In some embodiments, the support screen can be fixed by electrostatic adsorption, temporary bonding, or clamp positioning to prevent displacement.

[0091] S103: Fix the encapsulating film to the side of the support screen away from the back plate.

[0092] An encapsulating film is laid on top of the supporting screen, covering the entire surface of the supporting screen.

[0093] S104: Fix the substrate to the side of the encapsulating film away from the supporting screen.

[0094] A substrate is placed on top of the encapsulating film to form the bonding interface to be tested with the encapsulating film. The positions of each layer can be fixed by clamps or edge strips.

[0095] S105: The backplate, support screen, encapsulating film and substrate are laminated together so that the encapsulating film partially fills the mesh and contacts a portion of the first exposed surface of the mesh to obtain a test piece.

[0096] The assembled laminated structure is placed in a laminator for lamination. During this process, the encapsulating film melts and flows, partially filling the mesh of the support screen, and contacts and bonds with the first surface area of ​​the backplate exposed through the mesh. After cooling, a strong mechanical anchoring structure is formed, ultimately resulting in a complete test piece.

[0097] It is worth noting that the preparation method provided in this disclosure adopts a one-step lamination process, simultaneously completing the bonding between the encapsulating film and the substrate, the filling of the support screen mesh by the encapsulating film, and the contact between the encapsulating film and the exposed backplane area. This integrated process avoids residual stress, interface aging, or alignment errors caused by step-by-step curing, ensuring that each functional interface is formed under the same thermal conditions, thereby improving structural integrity and test reliability.

[0098] In some embodiments, the process parameters for the lamination step include: a lamination temperature of 120℃~150℃, for example, 120℃, 121℃, 122℃, 123℃, 124℃, 125℃, 126℃, 127℃, 128℃, 129℃, 130℃, 131℃, 132℃, 133℃, 134℃, 135℃, 136℃, 137℃, 138℃, 1 39℃, 140℃, 141℃, 142℃, 143℃, 144℃, 145℃, 146℃, 147℃, 148℃, 149℃ or 150℃; lamination time is 455s~465s, for example, it can be 455s, 456s, 457s, 458s, 459s, 460s, 461s, 462s, 463s, 464s or 465s.

[0099] At temperatures between 120°C and 150°C, the encapsulating film material reaches a suitable melt viscosity, allowing it to flow smoothly into the mesh of the supporting screen under pressure. Furthermore, the lamination temperature does not exceed 150°C, preventing thermal degradation or yellowing of the polymer layer in the backing plate.

[0100] The 455s–465s time window precisely covers the process of the encapsulating film from melting and cross-linking to initial curing, ensuring that the cross-linking degree of the encapsulating film reaches over 90%, forming a stable three-dimensional network structure, thereby enhancing the adhesion strength between the encapsulating film and the backing plate. Furthermore, precise time control avoids excessive aging of the encapsulating film or the generation of byproducts (such as acetic acid) due to prolonged heating, which could affect the reliability of the test specimens.

[0101] In some embodiments, before step S102, a pretreatment step of the support screen is included: ultrasonic cleaning with ethanol, followed by drying with nitrogen to remove surface contaminants and residual impurities, thereby improving the reliability of subsequent interface bonding.

[0102] Accordingly, another embodiment of this disclosure also provides a testing method, which is implemented using the test specimen described in the above embodiments or the test specimen prepared by the preparation method described in the above embodiments. The testing method provided in another embodiment of this disclosure will be described in detail below with reference to the accompanying drawings. For parts that are the same as or corresponding to the previous embodiment, please refer to the corresponding descriptions of the foregoing embodiments, which will not be repeated in detail below.

[0103] refer to Figure 8 The testing method provided in this disclosure includes at least the following steps: S201: Place the test piece in the tensile testing machine.

[0104] Standard specimen dimensions are typically 10mm to 25mm wide and no less than 150mm long. Before testing, the test piece is cut into multiple sets of specimens according to the standard specimen dimensions. It is important to note that sampling should avoid the edge areas of the test piece, prioritizing sampling from the central area. This is because the edge areas of the test piece are susceptible to external interference during lamination, cooling, or handling, potentially leading to defects such as uneven encapsulation film filling, poor interfacial bonding, microcracks, or stress concentration. Sampling from the edge areas may cause test results to deviate from the actual bonding performance, resulting in data bias.

[0105] Understandably, before placing the test piece into the tensile testing machine, the encapsulating film and the substrate should be manually peeled apart by a certain distance to facilitate clamping by the fixture.

[0106] S202: The substrate of the test piece is fixed by the first clamp of the tensile testing machine.

[0107] S203: The test piece is held in a second clamp at one end of a composite structure consisting of a back plate, a support screen, and an encapsulating film. A tensile test is then performed to cause the encapsulating film to peel the back plate and the support screen from the substrate. The peel strength between the encapsulating film and the substrate is then measured.

[0108] The use of clamps should ensure that the test piece is subjected to uniform force during the tensile process, and avoid local stress concentration or tensile deformation due to improper clamping.

[0109] In some embodiments, the test specimen is placed in the fixtures of the testing machine, and the fixture spacing should be adjusted according to the thickness of the test specimen. Fixture spacing refers to the initial distance between the two clamping fixtures on the testing machine, that is, the vertical or horizontal distance between the first and second fixtures before the start of the test. Fixture spacing ensures that the test specimen is in a naturally relaxed state before testing, i.e., without additional tension or compression, avoiding pre-stretching of the test specimen due to an initial spacing that is too small, or sagging of the test specimen due to an initial spacing that is too large, thus affecting the accuracy of the peel force.

[0110] For example, the clamp spacing can be set to 25mm, which is suitable for test pieces with a standard thickness of 1mm to 3mm. This spacing can effectively fix the test piece, reduce the risk of bending or slippage, and ensure a smooth peeling process and reliable data.

[0111] In some embodiments, after the test is started, the testing machine applies tensile force along the direction of the trapezoidal crack until the encapsulating film is completely separated from the substrate. During the peeling process, the change curve of tensile force with displacement is recorded. According to the calculation method specified in relevant standards, the data of the stable peeling stage in the curve is analyzed to obtain the average peeling force per unit width, which is defined as the peel strength of the test piece.

[0112] In some embodiments, in order to reduce random errors caused by factors such as test piece preparation, clamping state or local interface fluctuations in a single test, multiple test pieces from the same batch need to be tested repeatedly, and the arithmetic mean of the obtained peel strength data is used as the final result, thereby effectively improving the repeatability of test data and the accuracy of results.

[0113] In some embodiments, the peel strength test method includes one or more of 180° peel, 90° peel, and T-shaped peel.

[0114] For example, refer to Figure 9 The present invention can employ a 180° peel strength test method. The test piece is placed in a tensile testing machine. The substrate 13 of the test piece is fixed by the first clamp of the tensile testing machine. One end of the composite structure consisting of the back plate 10, the support screen 11, and the encapsulating film 12 of the test piece is held by the second clamp. Tension is applied in the direction indicated by the arrow until the encapsulating film 12 is completely separated from the substrate 13. The peel strength between the encapsulating film 12 and the substrate 13 is then measured.

[0115] It is worth noting that during the test, the tensile force is applied through the second clamp to the composite structure consisting of the backplate, support screen, and encapsulating film, causing the encapsulating film to act as the force-bearing entity, pulling the entire composite structure off the substrate. This mode directly measures the separation force between the encapsulating film and the substrate, effectively avoiding interference from insufficient strength or fragility of the backplate itself on the test results, and ensuring that the measured peel strength truly reflects the actual adhesion between the encapsulating film and the substrate interface.

[0116] In some embodiments, prior to performing the tensile test, the method further includes performing one or more of the following on the test specimen: a pressure cooker test, a damp heat aging test, a wet freeze test, and an ultraviolet aging test.

[0117] In some embodiments, damp heat test (DH) conditions may include: a temperature of 85°C, a relative humidity of 85%, and a duration of 1000 hours. Pressure cooker test (PCT) conditions may include: a temperature of 121°C, a relative humidity of 100%, a pressure of 0.2 MPa, and a test time typically of 48 hours or 96 hours.

[0118] The accelerated aging test simulates the harsh environmental conditions faced by photovoltaic modules during long-term outdoor operation, such as high temperature and humidity, temperature cycling, and strong ultraviolet radiation. This makes the peel strength data obtained from the subsequent tensile test more realistically reflect the interface performance of photovoltaic modules in actual application environments, thereby improving the authenticity and representativeness of the test results.

[0119] In some embodiments, the tensile speed during the tensile test is 95 mm / min to 105 mm / min, for example, it can be 95 mm / min, 96 mm / min, 97 mm / min, 98 mm / min, 99 mm / min, 100 mm / min, 101 mm / min, 102 mm / min, 103 mm / min, 104 mm / min or 105 mm / min.

[0120] This speed range is suitable for peel strength testing, especially in 180° peel mode, which ensures stable crack propagation and yields continuous, repeatable force-displacement curves.

[0121] Optionally, the stretching speed can be 100 mm / min, suitable for evaluating the adhesion performance between most encapsulation films and glass or backing materials.

[0122] The following is a specific embodiment of the test method provided in this application and its corresponding comparative example.

[0123] Example 1 Test conditions: temperature 121℃, relative humidity 100%, saturated vapor pressure approximately 0.2MPa, duration 96 hours (PCT, 96h). Test objects: Test pieces using the structure described in the embodiments of this disclosure, i.e., laminated structures including supporting screens, with 5 sets of test samples set; Test method: The 180° peel strength test was performed using the test method provided in the embodiments of this disclosure.

[0124] The results showed that all five test samples in Example 1 successfully completed the peeling process without any abnormalities such as backplate tearing, clamping failure, or structural damage. The measured peel strength was 21.3 ± 2.8 N / cm, which was valid and concentrated, indicating stable interfacial adhesion performance and good repeatability and reliability of the test process.

[0125] Comparative Example 1 Test conditions: Same as in Example 1; Test objects: Traditional structure test pieces without supporting screens, with other materials and preparation processes consistent with Example 1, and 5 sets of test samples were set; Test method: Perform the 180° peel strength test as well.

[0126] The test results showed that all five test samples in Comparative Example 1 experienced backplate breakage during the clamping or initial peeling stage, failing to complete effective peeling, resulting in a 100% test failure rate. This result indicates that after undergoing high-temperature and high-humidity aging, the mechanical strength of the backplate, lacking structural reinforcement, significantly decreases, making it difficult to withstand the tensile load required for peel strength testing, thus preventing the test from being conducted.

[0127] Example 2 Test conditions: temperature 85℃, relative humidity 85%, duration 3000 hours (DH3000h); Test objects: Test pieces using the structure described in the embodiments of this disclosure, i.e., laminated structures including supporting screens, with 5 sets of test samples set; Test method: The 180° peel strength test was performed using the test method provided in the embodiments of this disclosure.

[0128] Test results show that all five test samples in Example 2 successfully completed the peel strength test. The interface crack propagation was stable and continuous, and no backing plate tearing or clamping failure occurred. The measured peel strength was 27.3 ± 3.6 N / cm. This result indicates that after 3000 hours of damp heat aging, the interface between the adhesive film and the substrate still maintains good adhesion, and the test process has high repeatability and structural stability.

[0129] Comparative Example 2 Test conditions: Same as in Example 2; Test objects: Traditional structure test pieces without supporting screens, with other materials and preparation processes consistent with Example 2, and 5 sets of test samples were set up; Test method: Perform the 180° peel strength test as well.

[0130] The test results show that the backing plate of the five test samples in Comparative Example 2 cracked during the clamping stage or the initial peeling process, making effective peeling impossible and rendering the test data invalid. This phenomenon indicates that under long-term damp heat aging, the mechanical properties of the backing plate material decrease significantly due to moisture absorption and degradation. Without structural reinforcement measures, it is difficult to withstand the tensile load required for the peel strength test, leading to the failure of the peel strength test.

[0131] Based on a cumulative sample size of more than 50, and after multiple rounds of verification using PCT96h and DH3000h, the experimental group using the test specimens and test methods disclosed herein achieved a test success rate of over 95%, which is significantly better than the traditional unreinforced structure. At the same time, the relative standard deviation (RSD) of the peel strength data is less than 5%, indicating that the test results have excellent repeatability and high stability.

[0132] The above results demonstrate that by introducing a support screen, the test specimen provided in this embodiment can effectively suppress backplane breakage even after undergoing extreme high temperature and humidity and long-term damp heat aging, ensuring the smooth implementation of the peel strength test. The obtained peel strength data is not only effective and reliable but also exhibits good consistency, truly reflecting the adhesion performance of the encapsulation film and substrate interface under complex environmental stress.

[0133] Those skilled in the art will understand that the above embodiments are specific examples of implementing this disclosure, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of this disclosure. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this disclosure; therefore, the scope of protection of this disclosure should be determined by the scope defined in the claims.

Claims

1. A test piece, characterized in that, For peel strength testing of encapsulating films for photovoltaic modules, the test specimen includes: Back panel, comprising a first and a second opposing side; A supporting screen is located on the first surface, and the mesh of the supporting screen exposes a portion of the first surface; The encapsulating film is located on the side of the supporting screen away from the back plate; The substrate is located on the side of the encapsulating film away from the supporting screen.

2. The test piece according to claim 1, characterized in that, The first surface includes a first region and a second region, wherein the first region surrounds the second region; the supporting screen includes: The first screen portion is located in the first region; The second screen portion is located in the second region, wherein the mesh count of the first screen portion is greater than the mesh count of the second screen portion.

3. The test piece according to claim 2, characterized in that, The thickness of the first screen portion is greater than the thickness of the second screen portion.

4. The test piece according to claim 3, characterized in that, The thickness of the first screen portion decreases from the first region toward the second region.

5. The test piece according to claim 2, characterized in that, The area of ​​the first region accounts for 10% to 15% of the total area of ​​the first surface.

6. The test piece according to claim 2, characterized in that, The mesh of the first screen portion includes a conical structure, wherein the aperture of the conical structure near the back plate is larger than the aperture of the side near the encapsulating film; the mesh of the second screen portion includes a cylindrical structure.

7. The test piece according to claim 2, characterized in that, The mesh size of the first screen portion is 180-200 mesh, and the mesh size of the second screen portion is 150-180 mesh.

8. The test piece according to claim 1, characterized in that, The thickness of the supporting screen is 90um~120um.

9. The test piece according to claim 1, characterized in that, The mesh aperture is 70um~80um.

10. The test piece according to claim 1, characterized in that, The material of the supporting screen includes stainless steel.

11. A method for preparing a test specimen, characterized in that, include: A backplate is provided, the backplate comprising opposing first and second surfaces; The support screen is fixed to the first surface, and the mesh of the support screen is exposed in a portion of the first surface; The encapsulating film is fixed to the side of the supporting screen away from the back plate; The substrate is fixed to the side of the encapsulating film away from the supporting screen. The backplate, the support screen, the encapsulating film, and the substrate are laminated together to obtain a test piece.

12. The preparation method according to claim 11, characterized in that, The process parameters for the lamination step include: The lamination temperature is 120℃~150℃, and the lamination time is 455s~465s.

13. A testing method, characterized in that, The test is performed using a test specimen as described in any one of claims 1 to 10 or a test specimen prepared by the preparation method described in claim 11 or 12; the test method includes: Place the test specimen in the tensile testing machine; The substrate of the test piece is fixed by the first clamp of the tensile testing machine; A second clamp holds one end of the composite structure consisting of the back plate, support screen, and encapsulating film of the test piece, and a tensile test is performed to cause the encapsulating film to peel the back plate and support screen from the substrate, and the peel strength between the encapsulating film and the substrate is measured.

14. The test method according to claim 13, characterized in that, Prior to performing the tensile test, the method further includes: The test piece is subjected to one or more of the following tests: pressure cooker test, damp heat aging test, wet freeze test, and ultraviolet aging test.

15. The test method according to claim 13, characterized in that, When performing the tensile test, the tensile speed is 95 mm / min to 105 mm / min.

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