A photovoltaic module and a method of manufacturing the same

Abstract

The application provides a photovoltaic module and a preparation method thereof, wherein the preparation method comprises the following steps: providing a to-be-welded cell piece subjected to a first drying treatment, the to-be-welded cell piece being provided with a solder paste containing a welding aid, and an oxide layer being formed on the surface of the solder paste; performing a second drying treatment on the to-be-welded cell piece to obtain a twice-dried solder paste, the melting temperature of the tin alloy in the solder paste being T0, the drying temperature of the second drying treatment being T2, the range of T2 being T0-50 DEG C to T0-10 DEG C, and the drying time of the second drying treatment being 20 s to 40 s; and setting a welding strip on the twice-dried solder paste and performing a welding treatment on the welding strip, so that the virtual welding condition of the cell piece can be improved, and the welding performance of the cell piece based on the semi-drying process is improved.

Description

Technical Field

[0001] This application relates to the field of solar cells, and more particularly to a photovoltaic module and its fabrication method. Background Technology

[0002] BC (Back Contact) structure solar cells are gradually becoming the mainstream choice for high-efficiency modules due to their advantages such as no grid lines on the front side, high photoelectric conversion efficiency, and beautiful appearance.

[0003] All electrode grid lines of BC solar cells are located on the back side. To avoid short circuits between the solder ribbon and the irregular grid lines, insulating adhesive needs to be printed on the back side. At the same time, to compensate for the height difference between the PAD point (soldering point) and the solder ribbon caused by the insulating adhesive, solder paste needs to be printed on the PAD point to achieve a reliable connection of the solder ribbon.

[0004] Currently, a semi-drying solder paste process is commonly used for soldering. This involves controlling the temperature below the solder paste's melting point during the drying process, allowing only some of the solvent to evaporate before soldering. However, after this semi-drying process, the solder paste surface of the cells may oxidize during prolonged storage, leading to a significant decrease in soldering performance. Summary of the Invention

[0005] To address the aforementioned technical problems, this application discloses a photovoltaic module and its preparation method to improve the welding performance of solar cells based on a semi-drying process.

[0006] In the first aspect, this application provides a method for preparing a photovoltaic module, comprising the following steps: Provided a battery cell to be soldered after a first drying treatment, the battery cell to be soldered having solder paste containing soldering aid, and an oxide layer formed on the surface of the solder paste; The battery cell to be welded is subjected to a second drying process to obtain a secondary dried solder paste. The melting temperature of the tin alloy in the solder paste is T0, the drying temperature of the second drying process is T2, and the range of T2 is: T0-50℃~T0-10℃. The drying time of the second drying process is 20s~40s. Solder strips are placed on the secondary dried solder paste and the solder strips are soldered.

[0007] In some embodiments of this application, the step of performing a second drying process on the battery cells to be welded includes: During the second drying process, the soldering flux inside the solder paste migrates to the surface and undergoes a reduction reaction with the oxide layer.

[0008] In some embodiments of this application, after the second drying process, the cumulative evaporation rate of the soldering flux in the solder paste is 5wt% to 9wt%.

[0009] In some embodiments of this application, the storage time of the battery cell to be welded is greater than or equal to 12 hours, and the oxide layer includes at least one of SnO and SnO2.

[0010] In some embodiments of this application, the tin alloy is Sn63Pb37 alloy, and the temperature of the secondary drying treatment is 133℃~173℃; The tin alloy is Sn60Pb40 alloy, and the temperature of the secondary drying treatment is 133℃~173℃. The tin alloy is Sn43Pb43Bi14 alloy, and the temperature of the secondary drying treatment is 94℃~133℃.

[0011] In some embodiments of this application, the step of welding the solder strip includes: After the second drying process, the welding process is performed within a preset time period.

[0012] In some embodiments of this application, the preset time period is t1, where 0 min < t1 ≤ 60 min.

[0013] In some embodiments of this application, the first drying process includes: The battery cell to be welded is subjected to a first drying treatment to obtain a first-dry solder paste. The melting temperature of the tin alloy in the solder paste is T0, the drying temperature of the first drying treatment is T1, and the range of T1 is: T0-50℃~T0-10℃. The drying time of the first drying treatment is 20s~40s.

[0014] In some embodiments of this application, after the first drying process, the evaporation rate of the soldering flux in the solder paste is 1wt% to 7wt%.

[0015] Thirdly, this application provides a photovoltaic module, which is prepared by the photovoltaic module preparation method described in the first aspect.

[0016] Compared with the prior art, this application has at least the following beneficial effects: This application provides a photovoltaic module and its manufacturing method. In the manufacturing method, a secondary drying solder paste is obtained by subjecting the cells to be soldered to a second drying process. The temperature range of T2 is T0-50℃ to T0-10℃, meaning the drying temperature of the secondary drying process is 10℃ to 50℃ lower than the melting temperature of the tin alloy in the solder paste. Compared to existing semi-drying processes based on primary drying, this application, by subjecting the cells to be soldered to a secondary drying process and controlling the temperature and time of the secondary drying process within the range of this application, enables the soldering flux inside the solder paste to migrate to the surface, thereby reacting with the oxide layer on the solder paste surface to eliminate the oxide layer, improving soldering activity, and improving the solderability of the cells, thus enhancing the soldering performance of cells based on the semi-drying process. Furthermore, because the drying temperature is always lower than the melting temperature of the solder paste, the solder paste does not melt, and intermetallic compounds (IMCs) hardly grow, thereby reducing the risk of premature reaction or over-soldering between the solder paste and the silver layer. Furthermore, in existing semi-drying processes, when an oxide layer forms on the surface of the solder paste due to long-term storage, the solderability will be greatly reduced, and these solar cells will have to be scrapped. However, this application improves the solderability of these solar cells by performing a secondary drying process, which enables these solar cells to be reused in subsequent normal production, thereby reducing the production cost of photovoltaic modules. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 The images show the electroluminescence (EL) of solar cells after welding, with and without the secondary drying process. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0021] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0022] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; 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, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0023] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, components, or parts (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, components, or parts. Unless otherwise stated, "a plurality of" means two or more.

[0024] The technical solution of this application will be further described below with reference to the embodiments and accompanying drawings.

[0025] With the continuous advancement of cost reduction and efficiency improvement in photovoltaic modules, the thickness of silver PAD dots is generally controlled below 3μm to reduce silver consumption costs. However, thin silver layers are prone to over-soldering during the manufacturing process, where solder paste reacts with the silver layer at high temperatures to form excessively thick intermetallic compounds (IMCs), leading to solder joint embrittlement, decreased tensile strength, and even desoldering. To alleviate this problem, a semi-drying solder paste process is gradually being adopted. However, after the semi-drying process, the surface of the solder paste on the cells will oxidize during long-term storage, resulting in a significant decrease in solderability.

[0026] In view of this, firstly, this application provides a method for manufacturing a photovoltaic module, comprising the following steps: Step A: Provide the battery cell to be soldered after the first drying treatment. The battery cell to be soldered has solder paste on it, which contains soldering aids and has an oxide layer on its surface. Step B: Perform a second drying process on the battery cells to be soldered to obtain secondary dried solder paste. The melting temperature of the tin alloy in the solder paste is T0, the drying temperature of the second drying process is T2, and the range of T2 is: T0-50℃~T0-10℃. The drying time of the second drying process is 20s~40s. Step C: Place solder ribbons on the secondary dried solder paste and perform soldering on the solder ribbons.

[0027] In step A, the battery cells to be soldered include, but are not limited to, back contact cells. The solder paste contains solvents and soldering aids; the soldering aids contain active ingredients, such as rosin-based resins and organic acids. The oxide layer on the surface of the solder paste is formed on the battery cells to be soldered after prolonged exposure to air. For example, the exposure time is greater than or equal to 24 hours, typically 48-72 hours.

[0028] In step B, for example, T2 is: T0-50℃, T0-40℃, T0-30℃, T0-20℃, or T0-10℃; the drying time is 20s, 30s, or 40s. During the second drying process, heating causes the flux inside the solder paste to volatilize and migrate to the outside, redistributing it to the surface of the solder paste, restoring the wetting and protective capabilities of the solder paste. Furthermore, the active ingredients in the flux react with the oxide layer on the surface of the solder paste to generate volatile products, thereby eliminating the oxide layer on the surface of the solder paste and exposing the fresh metal surface.

[0029] This application provides a method for manufacturing photovoltaic modules. A secondary drying process is performed on the cells to be soldered to obtain a secondary dried solder paste. The temperature range of T2 is T0-50℃ to T0-10℃, meaning the drying temperature of the secondary drying process is 10℃ to 50℃ lower than the melting temperature of the tin alloy in the solder paste. Compared to existing semi-drying processes based on primary drying, this application, by performing a secondary drying process on the cells to be soldered and controlling the temperature and time of the secondary drying process within the specified range, enables the soldering flux inside the solder paste to migrate to the surface, thereby reacting with the oxide layer on the solder paste surface to eliminate the oxide layer, improving soldering activity, and mitigating poor solder joints in the cells. This improves the soldering performance of cells based on the semi-drying process. Furthermore, because the drying temperature is consistently lower than the melting temperature of the solder paste, the solder paste does not melt, and intermetallic compounds (IMCs) hardly grow, thus reducing the risk of premature reaction or over-soldering between the solder paste and the silver layer. Furthermore, in existing semi-drying processes, when an oxide layer forms on the surface of the solder paste due to long-term storage, the solderability will be greatly reduced, and these solar cells will have to be scrapped. However, this application improves the solderability of these solar cells by performing a secondary drying process, which enables these solar cells to be reused in subsequent normal production, thereby reducing the production cost of photovoltaic modules.

[0030] In some embodiments of this application, the step of performing a second drying process on the solar cells to be welded includes: During the second drying process, the soldering flux inside the solder paste migrates to the surface and undergoes a reduction reaction with the oxide layer, thus eliminating the oxide layer. Specifically, the organic acids and rosin reducing components in the soldering flux migrate to the surface of the solder paste along with the soldering flux, and undergo a reduction reaction with SnO, SnO2, and other components on the surface of the solder paste, thereby eliminating the oxide layer.

[0031] In some embodiments of this application, after the second drying process, the cumulative evaporation rate of the soldering flux in the solder paste is 5 wt% to 9 wt%. For example, 5 wt%, 6 wt%, 7 wt%, 8 wt%, or 9 wt%. The aforementioned cumulative evaporation rate refers to the sum of the evaporation rates of the flux during the first and second drying processes. The fact that the cumulative evaporation rate of the soldering flux is within the aforementioned range ensures that a sufficient amount of soldering flux remains in the solder paste after the two drying processes, which is beneficial for ensuring soldering quality.

[0032] In some embodiments of this application, the storage time of the solar cells to be soldered is greater than or equal to 24 hours, and the oxide layer includes at least one of SnO and SnO2. For example, the storage time is 12 hours, 24 hours, 48 ​​hours, or 72 hours. Due to production scheduling or uncontrollable reasons, the solar cells that have undergone the first semi-drying treatment cannot be completely consumed. An oxide layer containing SnO, SnO2, etc., will form on the surface of the solder paste of these solar cells, affecting the soldering performance. Furthermore, the additives continue to slowly evaporate, reducing the surface additive concentration and leading to a decrease in activity. This application improves the soldering performance of these solar cells by performing a second drying treatment, enabling these solar cells to be reused in subsequent normal production and reducing the production cost of photovoltaic modules.

[0033] In some embodiments of this application, the tin alloy is Sn63Pb37 alloy, and the temperature of the secondary drying treatment is 133℃~173℃; The tin alloy is Sn60Pb40 alloy, and the temperature for the secondary drying treatment is 133℃~173℃. The tin alloy is Sn43Pb43Bi14 alloy, and the secondary drying treatment temperature is 93℃~133℃.

[0034] For tin alloys with a single melting point, such as Sn63Pb37 alloy, the melting temperature refers to the melting point of the tin alloy; for tin alloys with a melting temperature range, such as Sn43Pb43Bi14 alloy, the melting temperature refers to the temperature at which the tin alloy completely melts, that is, its liquidus point temperature.

[0035] In some embodiments of this application, the step of welding the solder strip includes: After the second drying process, soldering is performed within a preset time period. That is, the time interval between the second drying process and the soldering process should not be too long to prevent the re-formation of an oxide layer on the surface of the solder paste, which would affect the soldering performance.

[0036] In some embodiments of this application, the time period is defined as t1, where 0 min < t1 ≤ 60 min, for example, t1 is 5 min, 10 min, 20 min, 50 min, or 60 min. The time interval between the second drying process and the soldering process is within the above range, which prevents the re-formation of an oxide layer on the surface of the solder paste, thereby further improving soldering performance.

[0037] In some embodiments of this application, the first drying process includes: The battery cells to be soldered undergo a first drying process to obtain a first-dry solder paste. The melting temperature of the tin alloy in the solder paste is T0, and the drying temperature of the first drying process is T1, ranging from T0-50℃ to T0-10℃. The drying time of the first drying process is 20s to 40s. For example, T1 can be T0-50℃, T0-40℃, T0-30℃, T0-20℃, or T0-10℃; and the drying time can be 20s, 30s, or 40s. The purpose of the first drying process is to keep the temperature below the melting temperature of the solder paste, allowing only a portion of the solvent in the solder paste to evaporate.

[0038] In some embodiments of this application, after the first drying process, the evaporation rate of soldering flux in the solder paste is 1 wt% to 7 wt%. For example, 1 wt%, 3 wt%, 5 wt%, or 7 wt%, thereby retaining sufficient active ingredients to maintain subsequent reactivity.

[0039] The photovoltaic module manufacturing method of this application, after secondary drying, can extend the effective welding window from 24 hours to 72 hours or even longer, and is compatible with existing production lines without the need for additional complex equipment. It can be carried out directly on the original drying equipment and with the original drying parameters, and can protect the low silver layer structure, avoid excessive growth of IMC caused by increasing welding temperature or welding time, and ensure the long-term reliability of the solder joint.

[0040] Secondly, this application provides a photovoltaic module, which is prepared by the photovoltaic module preparation method described in any of the above embodiments.

[0041] This application also provides a photovoltaic module for converting received light energy into electrical energy and transmitting it to an external load. The photovoltaic module includes: at least one cell string, which is composed of multiple solar cells connected together; an encapsulating film for covering the surface of the cell string; and a cover plate for covering the surface of the encapsulating film facing away from the cell string.

[0042] Example The photovoltaic modules and their preparation methods according to the embodiments of this application will be further described below with reference to more specific examples.

[0043] Example 1 <Supply of battery cells to be soldered> The provided material consists of solar cells undergoing a first drying process, which is then stored for 48 hours, resulting in an oxide layer forming on the surface of the solder paste. The solder paste contains Sn63Pb37 tin alloy and 10.5wt%±1wt% soldering flux. The first drying process was carried out at a temperature (T1) of 150℃ for 30 seconds. After the first drying process, the evaporation rate of the soldering flux in the solder paste is 6wt%. <Second Drying Process> The battery cells to be soldered undergo a second drying process to obtain secondary dried solder paste. The drying temperature (T2) for the second drying process is 150℃, and the drying time is 30 seconds. After the second drying process, the re-evaporation rate of the soldering flux in the solder paste is 3 wt%, resulting in a cumulative evaporation rate of 9 wt%. <Welding Process> Within 60 minutes of the completion of the second drying process, solder ribbons are placed on the second-drying solder paste and soldered. The soldering temperature is 235℃ and the soldering time is 2 seconds. Standard string soldering equipment is used to obtain photovoltaic modules.

[0044] Examples 2 to 5 Except for adjusting the drying temperature and drying time in the second drying process according to Table 1, the rest is the same as in Example 1.

[0045] Examples 6-7 Except for adjusting the storage time after the first drying process according to Table 1 in the section on "Supply of Cells to be Welded", the rest is the same as in Example 1.

[0046] Examples 8-9 Except for adjusting the type of tin alloy in the solder paste according to Table 1 in the section on "Supply of Battery Cells to be Soldered", the rest is the same as in Example 1.

[0047] Comparative Example 1 The process employs a single-stage drying process, specifically: the cells to be welded are first dried at a temperature of 150°C for 30 seconds; then solder ribbons are placed on the first-drying solder paste and soldered at a temperature of 235°C for 2 seconds; and finally, photovoltaic modules are obtained using standard string soldering equipment.

[0048] Comparative Examples 2 to 3 Except for adjusting the drying temperature of the second drying process according to Table 1 in the <Second Drying Process>, the rest is the same as in Example 1.

[0049] Table 1: Relevant data for each embodiment and comparative example

[0050] In Table 1, " / " indicates that no relevant preparation parameters exist.

[0051] As can be seen from Examples 1-5 and Comparative Example 1, when the storage time after the first drying treatment is 48 hours, the solder joints in the photovoltaic module of this application all form a metallurgical bond with the solder strip; while in Comparative Example 1, some solder joints do not form a metallurgical bond with the solder strip, with the non-bonded percentage being ≤5%. As can be seen from Examples 6 and Comparative Example 2, when the storage time after the first drying treatment is 72 hours, some solder joints in the photovoltaic module of this application do not form a metallurgical bond with the solder strip, with the non-bonded percentage being ≤5%; while in Comparative Example 2, some solder joints do not form a metallurgical bond with the solder strip, with the non-bonded percentage being >5% and ≤10%. As can be seen from Examples 7 and Comparative Example 3, when the storage time after the first drying treatment is 120 hours, some solder joints in the photovoltaic module of this application do not form a metallurgical bond with the solder strip, with the non-bonded percentage being >5% and ≤10%; while in Comparative Example 3, some solder joints do not form a metallurgical bond with the solder strip, with the non-bonded percentage being >10% and ≤30%. It is evident that the solution of this application improves the welding performance compared to the corresponding comparative examples for different storage durations.

[0052] As can be seen from Examples 1 and 8-9, the solution of this application can improve the welding performance of battery cells based on the semi-drying process for solder pastes with different tin alloy compositions.

[0053] Figure 1 The figures show the electroluminescence (EL) images of solar cells manufactured using a single-stage drying process and those manufactured using a double-stage drying process after welding. The figures show that, compared to solar modules manufactured using a single-stage drying process, solar modules manufactured using a single-stage drying process exhibit significantly fewer instances of solder joints failing to form a metallurgical bond with the solder strip, indicating a significant reduction in the occurrence of cold solder joints. In particular, solar modules stored for no more than 48 hours show virtually no instances of solder joints failing to form a metallurgical bond with the solder strip, indicating that cold solder joints are essentially nonexistent and can be reused in normal production. The figures also show that as storage time increases, the number of instances of solder joints failing to form a metallurgical bond with the solder strip gradually increases, but the number of instances in solar modules manufactured using the double-stage drying process is significantly less than that in solar modules manufactured using the single-stage drying process.

[0054] The present application provides a detailed description of a photovoltaic module and its preparation method. Specific examples have been used to illustrate the principles and implementation methods of the present application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core inventive points of the embodiments of the present application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present application. Therefore, the content of this specification should not be construed as a limitation of the present application.

Claims

1. A method for preparing a photovoltaic module, characterized in that, Includes the following steps: Provided a battery cell to be soldered after a first drying treatment, the battery cell to be soldered having solder paste containing soldering aid, and an oxide layer formed on the surface of the solder paste; The battery cell to be welded is subjected to a second drying process to obtain a secondary dried solder paste. The melting temperature of the tin alloy in the solder paste is T0, the drying temperature of the second drying process is T2, and the range of T2 is: T0-50℃~T0-10℃. The drying time of the second drying process is 20s~40s. Solder strips are placed on the secondary dried solder paste and the solder strips are soldered.

2. The method for preparing a photovoltaic module according to claim 1, characterized in that, The step of performing a second drying process on the battery cells to be welded includes: During the second drying process, the soldering flux inside the solder paste migrates to the surface and undergoes a reduction reaction with the oxide layer.

3. The method for preparing a photovoltaic module according to claim 1, characterized in that, After the second drying process, the cumulative evaporation rate of the soldering flux in the solder paste is 5wt%~9wt%.

4. The method for preparing a photovoltaic module according to claim 1, characterized in that, The storage time of the battery cell to be welded is greater than or equal to 12 hours, and the oxide layer includes at least one of SnO and SnO2.

5. The method for preparing a photovoltaic module according to claim 1, characterized in that, The tin alloy is Sn63Pb37 alloy, and the temperature of the secondary drying treatment is 133℃~173℃. The tin alloy is Sn60Pb40 alloy, and the temperature of the secondary drying treatment is 133℃~173℃. The tin alloy is Sn43Pb43Bi14 alloy, and the temperature of the secondary drying treatment is 94℃~133℃.

6. The method for preparing a photovoltaic module according to claim 1, characterized in that, The steps of welding the solder strip include: After the second drying process, the welding process is performed within a preset time period.

7. The method for preparing a photovoltaic module according to claim 6, characterized in that, The preset time period is t1, where 0 min < t1 ≤ 60 min.

8. The method for preparing a photovoltaic module according to claim 1, characterized in that, The first drying process includes: The battery cell to be welded is subjected to a first drying treatment to obtain a first-dry solder paste. The melting temperature of the tin alloy in the solder paste is T0, the drying temperature of the first drying treatment is T1, and the range of T1 is: T0-50℃~T0-10℃. The drying time of the first drying treatment is 20s~40s.

9. The method for preparing a photovoltaic module according to claim 8, characterized in that, After the first drying process, the evaporation rate of the soldering flux in the solder paste is 1wt%~7wt%.

10. A photovoltaic module, characterized in that, The photovoltaic module is prepared by any one of claims 1 to 9.

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