A photovoltaic module main grid structure, a preparation method and use thereof

Abstract

The application provides a photovoltaic module main grid structure, a preparation method and use thereof. The photovoltaic module main grid structure comprises a main grid and at least two pads arranged on the main grid in a spaced manner, and the area of the pads gradually increases from a low temperature area to a high temperature area. By arranging the pads with different areas in the main grid structure, the problem of inconsistent welding tension caused by uneven heating of the pads during welding is effectively improved, and the cell welding tension is effectively improved.

Description

Technical Field

[0001] This invention belongs to the technical field and relates to a photovoltaic module main grid structure, its preparation method and application. Background Technology

[0002] Photovoltaic modules consist of photovoltaic cells connected in series via solder ribbons to form a circuit that conducts current. Silver is typically printed on the cells, and solder ribbons are welded onto this silver, enabling current transfer from the silver to the solder ribbons. The soldering of the ribbons to the silver is primarily achieved through high-temperature tinning, where tin and silver form an Ag3Sn metallic compound layer, providing the soldering pull force. Controlling the soldering pull force at the module end is generally achieved by controlling the pull force between the solder ribbon and the silver pads (pads). The pad pull force helps to fix the solder ribbon in place, ensuring product reliability.

[0003] The tensile strength between the pad and the solder ribbon is affected by three factors: 1. the adhesion between silver and the battery; 2. the tensile strength of Ag3Sn itself; and 3. the tin content in the solder ribbon's tin-lead layer. Factors 2 and 3 are both affected by temperature. Ag3Sn thickness growth is a process of tin diffusing into silver at high temperatures, leaving a lead-rich layer in the tin-lead layer, thus losing its mechanical properties. Simultaneously, Ag3Sn's granular structure also grows, becoming long and brittle, leading to a decrease in the tensile strength of the Ag3Sn layer. However, excessively low temperatures or insufficient soldering time can result in insufficient Ag3Sn layer growth, leading to poor solder joints. Generally, Ag3Sn layers with a thickness between 500nm and 3µm exhibit good solder tensile strength, with the highest tensile strength around 1µm.

[0004] The soldering of the solder ribbon to the PAD points is generally achieved through heating of the base plate and lamp tube. The temperature sources are mainly the heating of the base plate under the battery and the lamp heating. Silver, as a highly reflective material, generally reflects light. Silicon, as an absorption source, can effectively absorb light and convert it into heat, which is transferred to the silver PAD points, and then the heat is transferred to the solder ribbon through the silver PAD points. Therefore, the heat source for the solder ribbon to melt is from the silicon wafer conducted through silver. During the soldering process, one or more batteries are usually soldered together. The PAD points of the batteries near the edge of the enclosure have relatively lower temperatures due to their shorter heat dissipation channels, while the PAD points of the batteries near the center of the soldering enclosure have higher temperatures due to their longer heat dissipation channels. This results in a temperature gradient difference among the batteries on a main grid, which leads to uneven soldering tension on a main grid. During soldering, the lamp intensity and base plate temperature are generally adjusted to achieve the optimal soldering tension for the middle PAD points, while the tension for the edge PADs is lower. Among them, the PAD points located on the outside of the oven have lower tensile strength due to the relatively thin Ag3Sn compound layer caused by the lower soldering temperature, resulting in a weak solder joint. The PAD points located on the inside of the oven have lower tensile strength due to the higher soldering temperature, resulting in a thinner Ag3Sn compound layer. S The relatively thick compound layer is due to the low tensile strength caused by excessive welding.

[0005] CN213242563U discloses a solar cell with one or more spaced-apart PADs on one side. The solar cell also has multiple spaced-apart fine grids and sub-main grids corresponding to the number of PADs. The PADs are located on one side along the length of the fine grids. Each sub-main grid is connected to all the fine grids, and one end of each sub-main grid is connected to a corresponding PAD. With this configuration, during current transmission, the current collected by the fine grids is transmitted to the sub-main grids, and then to the corresponding PADs, thus greatly shortening the current transmission path and reducing current transmission loss, significantly improving the conversion efficiency of the solar cell. Furthermore, to transmit the same amount of current to the PADs, this novel solar cell requires far fewer fine grids than a conventional solar cell of the same size, thereby significantly reducing the production cost of the solar cell.

[0006] CN212874497U discloses a novel solar cell with one or more sets of current collection and transmission devices. Each set of current collection and transmission devices includes a PAD point and multiple fine grids. The PAD point is located on one side of the solar cell and is coated with silver paste. One end of each of the multiple fine grids is connected to the PAD point. With this configuration, the solar cell does not require a main grid, i.e., it does not require silver paste connecting two adjacent PAD points, thus greatly reducing the amount of silver paste used and significantly reducing production costs. Furthermore, during current transmission, the current collected by the fine grids can be directly transmitted to the PAD point, thereby greatly reducing the current transmission path, lowering the series resistance of the solar cell, and thus significantly improving the conversion efficiency of the solar cell.

[0007] Ensuring consistent welding tension at different PAD points on the battery main grid during the welding process has become an urgent problem to be solved. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a photovoltaic module main grid structure, its preparation method, and its applications. By setting different areas of the pads in the main grid structure, the present invention effectively improves the problem of inconsistent welding tensile force caused by uneven heating of the pads during the welding process, thereby effectively increasing the welding tensile force of the battery.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a photovoltaic module main grid structure, the photovoltaic module main grid structure including a main grid and at least two pads spaced apart on the main grid, the area of ​​the pads increasing sequentially from low to high temperature.

[0011] This invention sets up a pad structure in which the area of ​​the pads increases sequentially along the direction from the main grid to the center of the solder box, i.e., from low to high temperature. This adjusts the distance of heat flow to the solder ribbon and changes the temperature of different pads. During the soldering process, this achieves the effect of controlling the tinning temperature, offsetting the effects of uneven temperature, making the pad tension more uniform, and thus improving the soldering tension of the battery.

[0012] It should be noted that the causes of uneven temperature in this invention are not specifically required or limited. For example, they could be temperature differences caused by the pressure plate of the welding machine or temperature differences caused by the position of the oven.

[0013] It should be noted that most battery grids use rectangular pads, which are relatively longer perpendicular to the main grid and relatively shorter parallel to the main grid. Therefore, heat is relatively easy to transfer from the shorter side to the solder ribbon.

[0014] As a preferred embodiment of the present invention, the pad is provided with a hollow structure, and the hollow patterns in the hollow structure are arranged at intervals.

[0015] The present invention further improves the battery welding pull by setting a hollow structure on the pad and optimizing the heat transfer path of the pad structure, changing the heat transfer path from two-dimensional surface transfer to one-dimensional line transfer, and further adjusting the pad temperature to make the welding pull more consistent.

[0016] Preferably, the hollow structure includes one or a combination of at least two of the following: linear hollow, circular hollow, or grid hollow.

[0017] As a preferred embodiment of the present invention, the hollow structure is a linear hollow structure, and the angle between the linear hollow structure on the pad and the main gate increases sequentially from low to high temperature.

[0018] The present invention further adjusts the angle between the linear cutout and the main gate to change the heat transfer path and balance the temperature of the pads.

[0019] Preferably, the angle between the linear perforation and the main grid is 0 to 90°, for example, 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80° or 90°.

[0020] As a preferred embodiment of the present invention, the welding pad located at the center of the welding box has a linear perforation at an angle of 90° to the main grid.

[0021] Preferably, the angle between the linear perforation of the pad located at the edge of the welding box and the main gate is 0°.

[0022] As a preferred embodiment of the present invention, the spacing of the cutout structure on the pad decreases sequentially from low to high temperature.

[0023] Preferably, the width of the hollow pattern in the hollow structure is 30 to 100 μm, for example, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm.

[0024] Preferably, the spacing between the cutouts is 30–350 μm, for example, 30 μm, 60 μm, 90 μm, 120 μm, 150 μm, 180 μm, 210 μm, 240 μm, 270 μm, 300 μm, 330 μm, or 350 μm. The width of the cutout spacing is the distance between two adjacent cutout patterns. Taking the linear cutout of the silver pad as an example, the width of the silver line is the width of the cutout spacing.

[0025] As a preferred embodiment of the present invention, the solder pad is provided with solder strips.

[0026] Preferably, a welding layer is provided between the solder pad and the solder strip.

[0027] Preferably, the solder layer includes a tin-lead layer and an Ag3Sn layer stacked together, with the Ag3Sn layer located near the solder pad.

[0028] In this invention, the Ag3Sn layer is generated during the soldering process between the tin-lead layer and the silver pad, ensuring the tensile strength of the soldering.

[0029] Preferably, the solder strip comprises copper solder strip.

[0030] Preferably, the pads are made of silver.

[0031] In a second aspect, the present invention provides a method for fabricating the photovoltaic module busbar structure described in the first aspect, the method comprising:

[0032] A main grid is set on the substrate of a photovoltaic module, and pads with progressively larger areas are set on the main grid from low to high temperature to obtain the photovoltaic module main grid structure.

[0033] As a preferred embodiment of the present invention, the preparation method specifically includes the following steps:

[0034] The main grid is printed on the substrate of the photovoltaic module. The substrate with the main grid is placed on a heating table, and the solder layer is placed on the solder pad in sequence. After soldering under lamp heating, the main grid structure of the photovoltaic module is obtained.

[0035] As a preferred embodiment of the present invention, the heating temperature of the heating table is 25 to 100°C, for example, 25°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C or 100°C.

[0036] It should be noted that the lamp tube emits heating light for irradiation and heating during the lamp heating process.

[0037] Thirdly, the present invention provides a photovoltaic module, the photovoltaic module comprising a substrate and grid lines, wherein the main grid lines adopt the photovoltaic module main grid structure described in the first aspect.

[0038] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] This invention sets up a pad structure in which the area of ​​the pads increases sequentially along the direction from the main grid to the center of the solder box, i.e., from low to high temperature. This adjusts the distance of heat flow to the solder ribbon and changes the temperature of different pads. During the soldering process, this achieves the effect of controlling the tinning temperature, offsetting the effects of uneven temperature, making the pad tension more uniform, and thus improving the soldering tension of the battery. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the photovoltaic module main grid structure provided in Embodiments 1-4 of the present invention, wherein I represents the photovoltaic module main grid structure of Embodiment 1, II represents the photovoltaic module main grid structure of Embodiment 2, III represents the photovoltaic module main grid structure of Embodiment 3, and IV represents the photovoltaic module main grid structure of Embodiment 4.

[0042] Figure 2 This is a schematic diagram of a hollow structure provided in a specific embodiment of the present invention, wherein a, b and c represent horizontal linear hollow, vertical linear hollow and diagonal linear hollow, respectively, d represents grid hollow and e represents circular hollow;

[0043] Figure 3 This is a schematic diagram illustrating the fabrication process of the photovoltaic module main busbar structure provided in a specific embodiment of the present invention.

[0044] Wherein, 1-substrate; 2-pad; 3-Ag3Sn layer; 4-tin-lead layer; 5-solder ribbon; 6-heating stage; 7-lamp tube; 8-heating light; 9-main gate. Detailed Implementation

[0045] It should be understood that in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the invention and for simplifying the description, and 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. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0046] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0047] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0048] In one specific embodiment, the present invention provides a photovoltaic module main grid structure, the photovoltaic module main grid structure including a main grid 9 and at least two pads 2 spaced apart on the main grid 9, the area of ​​the pads 2 increasing sequentially from low temperature to high temperature region.

[0049] This invention sets up a pad 2 structure, with the area of ​​the pad 2 increasing sequentially along the direction of the main grid 9 near the center of the welding box, i.e., the area from low to high temperature. This adjusts the distance of heat flow to the solder ribbon 5, changes the temperature of different pads 2, and achieves the effect of controlling the tinning temperature during the welding process. This counteracts the effects of uneven temperature, makes the pull force of the pad 2 tend to be uniform, and achieves the effect of improving the welding pull force of the battery.

[0050] Specifically, the solder pad 2 has a hollow structure with intermittent hollow patterns within it. This invention further optimizes the heat transfer path of the solder pad 2 by creating a hollow structure, changing the heat transfer path from a two-dimensional surface to a one-dimensional line, thereby further regulating the temperature of the solder pad 2 and making the welding pull force more consistent, thus improving the battery welding pull force.

[0051] Furthermore, such as Figure 2 As shown, the hollow structure includes one or a combination of at least two of the following: linear hollow, circular hollow, or grid-like hollow.

[0052] Furthermore, the perforated structure is a linear perforation. Along the direction of the main gate 9 near the center of the soldering box, i.e., from low to high temperature, the angle between the linear perforation on the pad 2 and the main gate 9 increases sequentially, ranging from 0° to 90°. Specifically, the pad 2 located at the center of the soldering box has a 90° angle between the linear perforation and the main gate 9, i.e., a horizontal linear perforation; the pad 2 located at the edge of the soldering box has a 0° angle between the linear perforation and the main gate 9, i.e., a vertical linear perforation. Additionally, when the angle between the linear perforation and the main gate 9 is between 0° and 90°, it is an oblique linear perforation. This invention further adjusts the angle between the linear perforation and the main gate 9 to change the heat transfer path and equalize the temperature of the pad 2.

[0053] Specifically, from low to high temperature, the spacing between the cutouts on pad 2 decreases sequentially. Further, the spacing between the cutouts is 30–350 μm, and the width of the cutout pattern (e.g., the width of the silver line) is 30–100 μm.

[0054] Specifically, solder strips 5 are provided on the pad 2. A solder layer is provided between the pad 2 and the solder strip 5. The solder layer includes a tin-lead layer 4 and an Ag3Sn layer 3 stacked together, with the Ag3Sn layer 3 closer to the pad 2. The solder strip 5 includes copper solder strips 5, and the pad 2 is made of silver. In this invention, the Ag3Sn layer 3 is generated during the soldering process between the tin-lead layer 4 and the silver pad 2, ensuring the tensile strength of the solder joint.

[0055] In another specific embodiment, the present invention provides a method for fabricating the above-mentioned photovoltaic module busbar structure, such as... Figure 3 As shown, the preparation method specifically includes the following steps:

[0056] The main grid 9 is printed on the substrate 1 of the photovoltaic module. The substrate 1 with the main grid 9 is placed on a heating stage 6 at 25-100°C, and the solder layer is sequentially placed on the solder pad 2. After soldering under lamp heating, the main grid structure of the photovoltaic module is obtained. During the lamp heating process, the lamp tube 7 emits heating light 8 for irradiation and heating.

[0057] The present invention also provides a photovoltaic module, the photovoltaic module comprising a substrate 1 and grid lines, wherein the main grid line 9 of the grid lines adopts the above-described photovoltaic module main grid structure.

[0058] Example 1

[0059] This embodiment provides a photovoltaic module busbar structure, based on a specific implementation method, such as... Figure 1As shown in Figure Ⅰ, the area of ​​the pads 2 increases sequentially along the direction of the main gate 9 near the center of the welding box.

[0060] Example 2

[0061] This embodiment provides a photovoltaic module busbar structure, which, compared to Embodiment 1, is as follows: Figure 1 As shown in II, along the direction of the main gate 9 near the center area of ​​the welding box, the area of ​​the pad 2 increases sequentially, and linear cutouts are set on the pad 2, which are divided into 4 vertical linear cutouts and 5 horizontal linear cutouts.

[0062] Example 3

[0063] This embodiment provides a photovoltaic module busbar structure, which, compared to Embodiment 1, is as follows: Figure 1 As shown in section III, along the direction of the main gate 9 near the center area of ​​the welding box, the area of ​​the pad 2 increases sequentially, and linear cutouts are set on the pad 2, which are divided into 3 longitudinal linear cutouts, 3 diagonal linear cutouts and 3 transverse linear cutouts.

[0064] Example 4

[0065] This embodiment provides a photovoltaic module busbar structure, which, compared to Embodiment 1, is as follows: Figure 1 As shown in section IV, along the direction of the main gate 9 near the center area of ​​the welding box, the area of ​​the pad 2 increases sequentially, and linear cutouts are set on the pad 2, which are divided into 4 vertical linear cutouts and 5 horizontal linear cutouts.

[0066] Comparative Example 1

[0067] This comparative example provides a photovoltaic module busbar structure. Compared with Example 1, the difference is that the structure and area of ​​each pad 2 are the same.

[0068] The welding pull force of the pads 2 prepared in Examples 1, 2 and Comparative Example 1 was tested, such as... Figure 1 As shown, the pads of I and II are numbered 1, 2...9 from top to bottom, and the test results are shown in Table 1.

[0069] Table 1

[0070]

[0071]

[0072] As can be seen from the table above, the welding tensile test results of Example 1 are significantly better than those of Comparative Example 1. In Example 2, although the welding tensile force is reduced due to the hollow structure, the overall difference in tensile force distribution is smaller than that of Comparative Example 1, which improves the uniformity of tensile force on the pads. In Comparative Example 1, some pads are close to the edge of the solder box, and some pads are close to the inside of the solder box, so there is a difference in the temperature of the pads. During serial soldering, there is a tendency for over-soldering and under-soldering. Among them, the pads near the outer edge of the oven have lower tensile force because the welding temperature is low and the Ag3Sn layer 3 is not fully grown. The pads near the middle of the oven have lower tensile force because the welding temperature is high and the Ag3Sn layer 3 is thicker. It can be seen that by setting the structure of the pads 2, the area of ​​the pads 2 increases sequentially along the direction of the main grid 9 near the center area of ​​the welding box, thereby adjusting the distance of heat flow to the solder strip 5 and changing the temperature of different pads 2. During the welding process, the effect of controlling the tinning temperature is achieved, the influence of uneven temperature is offset, and the tension of the pads 2 tends to be uniform, thereby improving the welding tension of the battery.

[0073] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A photovoltaic module busbar structure, characterized by, The photovoltaic module main grid structure includes a main grid and at least two pads spaced apart on the main grid, with the area of ​​the pads increasing sequentially from low to high temperature. The area from low to high temperature is the pad along the main grid towards the center of the welding box; The pads are provided with a hollow structure; The hollow structure is a linear hollow, and the angle between the linear hollow on the pad and the main gate increases sequentially from low to high temperature. The solder pads are provided with solder strips.

2. The photovoltaic module busbar structure according to claim 1, characterized in that, The hollowed-out patterns within the hollowed-out structure are spaced out.

3. The photovoltaic module busbar structure according to claim 1, characterized in that, The angle between the linear cutout and the main grille is 0 to 90°.

4. The photovoltaic module busbar structure according to claim 3, characterized in that, The welding pad located at the center of the welding box has a linear perforation at an angle of 90° to the main grid.

5. The photovoltaic module busbar structure according to claim 3, characterized in that, The welding pads located at the edge of the welding box have a linear perforation at an angle of 0° to the main gate.

6. The photovoltaic module busbar structure according to claim 1, characterized in that, From low to high temperature, the spacing of the cutout structure on the pad decreases sequentially.

7. The photovoltaic module busbar structure according to claim 2, characterized in that, The width of the hollowed-out pattern in the hollowed-out structure is 30–100 μm.

8. The photovoltaic module busbar structure according to claim 6, characterized in that, The spacing between the cutouts is 30–350 μm.

9. The photovoltaic module busbar structure according to claim 1, characterized in that, A welding layer is provided between the solder pad and the solder strip.

10. The photovoltaic module busbar structure according to claim 9, characterized in that, The solder layer includes a tin-lead layer and an Ag3Sn layer stacked together, with the Ag3Sn layer located near the solder pad.

11. The photovoltaic module busbar structure according to claim 1, characterized in that, The solder strip includes copper solder strip.

12. The photovoltaic module busbar structure according to claim 1, characterized in that, The pads are made of silver.

13. A method for fabricating a photovoltaic module main busbar structure according to any one of claims 1-12, characterized in that, The preparation method includes: A main grid is set on the substrate of a photovoltaic module, and pads with progressively larger areas are set on the main grid from low to high temperature to obtain the photovoltaic module main grid structure.

14. The preparation method according to claim 13, characterized in that, The preparation method specifically includes the following steps: The main grid is printed on the substrate of the photovoltaic module. The substrate with the main grid is placed on a heating table, and the solder layer is placed on the solder pad in sequence. After soldering under lamp heating, the main grid structure of the photovoltaic module is obtained.

15. The preparation method according to claim 14, characterized in that, The heating temperature of the heating platform is 25–100°C.

16. A photovoltaic module, characterized in that, The photovoltaic module includes a substrate and grid lines, wherein the main grid lines adopt the photovoltaic module main grid structure according to any one of claims 1-12.

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