Welding method, battery string, battery assembly, and photovoltaic system

Abstract

The application is suitable for the photovoltaic power generation technical field, and provides a welding method, a cell string, a cell module and a photovoltaic system. The method is applied to a welding device. The welding device comprises a solder pre-melting device and a welding device. The solder pre-melting device comprises a heat source, a heat conduction plate, a temperature detection device and a temperature control device. Since the heat source is in contact with the heat conduction plate, the temperature detection device detects the temperature of the heat conduction plate and outputs the detection result to the temperature control device. The temperature control device controls the heat source according to the detection result, so that the temperature of the heat conduction plate is in a preset interval. The preset interval is associated with the melting point of the solder. Therefore, the heat conduction plate can conduct heat to the solar cell, realize contact heating of the solar cell, make the solder at each position of the solar cell be heated more uniformly, make the solder melting process be basically consistent, make the solidified solder be firmly attached to the solar cell and keep a certain height, facilitate subsequent welding, and improve the string welding effect.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic power generation technology, and particularly relates to welding methods, battery strings, battery modules and photovoltaic systems. Background Technology

[0002] Solar cell power generation is a sustainable and clean energy source that uses the photovoltaic effect of semiconductor pn junctions to convert sunlight into electrical energy.

[0003] In related technologies, to improve the string bonding effect of solar cells, solder is typically applied to the solder joints of the solar cells before string bonding, and a curing oven is used to pre-melt and cure the solder. However, due to the difficulty in controlling the temperature field in the curing oven, temperature differences exist at various locations within the oven, resulting in uneven curing. This can easily lead to over-melting of the solder in some areas of the same solar cell, causing it to lose height and making welding difficult, while insufficient melting of the solder in other areas can lead to it detaching easily.

[0004] Therefore, how to melt the solder placed on the solar cells to improve the stringing effect has become an urgent problem to be solved. Summary of the Invention

[0005] This invention provides a welding method aimed at solving the problem of how to melt the solder disposed on a solar cell and maintain the height of the solder to improve the stringing effect.

[0006] The present invention is implemented as follows: a welding method applicable to welding equipment, the welding equipment including a solder pre-melting device and a welding device, the solder pre-melting device including a heat source, a heat-conducting plate, a temperature detection device, and a temperature control device;

[0007] The heat source is in contact with the heat-conducting plate, the temperature detection device is electrically connected to the temperature control device, and the temperature control device is electrically connected to the heat source.

[0008] Welding methods include:

[0009] Start the heat source;

[0010] The temperature of the heat-conducting plate is detected using a temperature detection device;

[0011] Based on the detection results of the temperature detection device, the heat source is controlled by the temperature control device so that the temperature of the heat-conducting plate is within a preset range, which is related to the melting point of the solder.

[0012] The solar cell is placed on the surface of the heat-conducting plate, and the solder on the solar cell is melted.

[0013] The solder has solidified and melted.

[0014] Welding equipment is used to weld the solder strip to the cured solder.

[0015] Furthermore, the duration for which the solar cell is placed on the surface of the heat-conducting plate is related to the temperature of the heat-conducting plate.

[0016] Furthermore, the heat source includes several heating rods or heating wires that are in contact with the heat-conducting plate.

[0017] Furthermore, the solder pre-melting device also includes an adsorption tank, an adsorption interface, and an adsorption device. The adsorption tank is connected to the adsorption device through the adsorption interface, and the adsorption tank is located on the side surface of the heat-conducting plate that contacts the solar cell.

[0018] The method also includes:

[0019] Start the adsorption device to adsorb the solar cells onto the adsorption tank.

[0020] Furthermore, the contact surface between the heat-conducting plate and the solar cell is convex.

[0021] Furthermore, the solar cell includes a solder area for setting solder, and a limiting post on the contact surface between the heat-conducting plate and the solar cell. The step of placing the solar cell on the surface of the heat-conducting plate includes:

[0022] The solar cells are placed on the contact surface according to the position of the limiting post, so that the adsorption tank and the solder area are staggered.

[0023] Furthermore, prior to the step of placing the solar cell on the surface of the heat-conducting plate, the welding method includes:

[0024] Solder is applied to solar cells using a screen printing process.

[0025] Furthermore, the solder pre-melting device includes an automatic optical detector used to monitor the melting of the solder.

[0026] Furthermore, a heat-resistant layer is provided on the contact surface between the heat-conducting plate and the solar cell.

[0027] Furthermore, the solder pre-melting device also includes a self-cleaning mechanism for cleaning contaminants on the heat-conducting plate.

[0028] This invention also provides a battery string manufactured using the welding method described above.

[0029] This invention also provides a battery assembly, including the battery string as described above.

[0030] This invention also provides a photovoltaic system, including the battery module as described above.

[0031] The beneficial effects achieved by this invention are as follows: The welding equipment includes a solder pre-melting device and a welding device. The solder pre-melting device includes a heat source, a heat-conducting plate, a temperature detection device, and a temperature control device. Since the heat source is in contact with the heat-conducting plate, the solar cell can be placed on the surface of the heat-conducting plate. The temperature detection device detects the temperature of the heat-conducting plate and outputs the detection result to the temperature control device. The temperature control device controls the heat source according to the detection result, ensuring that the temperature of the heat-conducting plate is within a preset range. This preset range is related to the melting point of the solder, so the heat-conducting plate can conduct heat to the solar cell, achieving contact heating of the solar cell. This results in more uniform heating of the solder throughout the solar cell, a basically consistent solder melting process, and solidified solder that firmly adheres to the solar cell while maintaining a certain height, facilitating subsequent welding and improving the stringing effect. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of one embodiment of the solder pre-melting device in the welding method provided by the present invention;

[0033] Figure 2 This is a schematic diagram of another embodiment of the solder pre-melting device in the welding method provided by the present invention;

[0034] Figure 3 This is an enlarged schematic diagram of part A in diagram 1;

[0035] Figure 4 This is a schematic diagram of the structure of a solar cell placement device in an embodiment of the welding method provided by the present invention.

[0036] Figure 5 This is a schematic diagram of the structure of the convex surface of the heat-conducting plate in one embodiment of the solder pre-melting device in the welding method provided by the present invention;

[0037] Figure 6 This is a schematic diagram of the structure of a solar cell placed on a convex surface in one embodiment of the solder pre-melting device in the welding method provided by the present invention;

[0038] Figure 7 This is a schematic flowchart of one embodiment of the welding method provided in this invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] The heat-conducting plate in this embodiment can conduct heat to the solar cell, achieving contact heating of the solar cell. This makes the solder in all parts of the solar cell more evenly heated, and the solder melting process is basically the same. The solidified solder can firmly adhere to the solar cell and retain a certain height, which facilitates subsequent welding and improves the stringing effect.

[0041] Example 1

[0042] like Figure 7 As shown, one embodiment of this application provides a welding method applicable to welding equipment. The welding equipment includes a solder pre-melting device and a welding device. The solder pre-melting device includes a heat source 100, a heat-conducting plate 200, a temperature detection device 300, and a temperature control device. The heat source 100 is in contact with the heat-conducting plate 200, and the temperature detection device 300 is electrically connected to the temperature control device, which is also electrically connected to the heat source 100. The welding method includes:

[0043] S1100, Start the heat source;

[0044] S1200: The temperature of the heat-conducting plate is detected using a temperature detection device;

[0045] S1300: Based on the detection results of the temperature detection device, the heat source is controlled by the temperature control device so that the temperature of the heat-conducting plate is within a preset range, which is related to the melting point of the solder.

[0046] S1400: Place the solar cell on the surface of the heat-conducting plate and melt the solder on the solar cell;

[0047] It is understandable that "placing the solar cell on the surface of the heat-conducting plate" can also be performed before S1400. For example, the solar cell can be placed on the surface of the heat-conducting plate first, and then the heat-conducting plate can be heated so that the temperature of the heat-conducting plate is within a preset range.

[0048] S1500, the solder after solidification and melting;

[0049] It is understandable that the "solder solidification after melting" can be completed on the heat-conducting plate. For example, a heat source first heats the heat-conducting plate to melt the solder, and then the heat source stops working, allowing the temperature of the heat-conducting plate to gradually decrease, thereby causing the solder to solidify. Of course, the "solder solidification after melting" can also be completed after the solar cell is removed from the heat-conducting plate. For example, a robotic arm removes the solar cell, allowing the solder to cool and solidify.

[0050] S1600: Welding the solder strip to the cured solder using a welding device.

[0051] like Figures 1 to 6As shown, the solder pre-melting device of the welding equipment is used to pre-melt the solder on the solar cell 400 so that the solder printed on the solar cell 400 is first firmly connected to the solar cell 400 and maintained at a certain height, and then serially welded by the welding device.

[0052] Optionally, the solder pre-melting device includes a heat source 100, which generates heat. Specifically, the heat source 100 is in contact with a heat-conducting plate 200, allowing the heat generated by the heat source 100 to be conducted to the heat-conducting plate 200. The heat-conducting plate 200 supports the solar cell 400; typically, the upper surface of the heat-conducting plate 200 is considered the supporting surface for the solar cell 400. Both the temperature detection device 300 and the heat source 100 are electrically connected to a temperature control device. The temperature detection device 300 detects the temperature of the heat-conducting plate 200 and outputs it to the temperature control device. The temperature control device controls the heat source 100 based on the detection result output by the temperature detection device 300.

[0053] Optionally, the welding equipment is equipped with a processor, which is electrically connected to a temperature control device and also electrically connected to the welding equipment. The steps of the welding method provided in this application can be executed by the processor. In implementation, the processor can be an actual processor on the welding equipment or a virtual processor in the cloud, without limitation.

[0054] Optionally, the processor first activates the heat source 100, which generates heat and transfers it to the heat conduction plate 200. Then, the processor detects the temperature of the heat conduction plate 200 through the temperature detection device 300, and based on the detection result of the temperature detection device 300, sends a control signal to the temperature control device, so that the temperature control device controls the working state of the heat source 100 to keep the temperature of the heat conduction plate 200 within a preset range.

[0055] As another implementation, the temperature detection device 300 can send the detected result to the temperature control device, which then controls the working state of the heat source 100 based on the detection result.

[0056] Optionally, the working state of the heat source 100 can be regarded as including a heating state, a constant temperature state, and a cooling state. The heating state refers to the heat source 100 heating the heat conduction plate 200 to raise the temperature of the heat conduction plate 200. The constant temperature state refers to the heat source 100 maintaining the temperature of the heat conduction plate 200 at a constant temperature. The cooling state refers to the heat source 100 not working or reducing its power to lower the temperature of the heat conduction plate 200, which will not be elaborated further.

[0057] Optionally, the preset range can be set according to the melting point of the solder. For example, the value of X can be from 0℃ to 20℃. The preset range is equal to the melting point of the solder plus X. That is, the temperature of the heat-conducting plate after heating is 0℃ to 20℃ higher than the melting point of the solder, so that the solder can be melted.

[0058] Optionally, the range of X from 0°C to 20°C is an example of one embodiment of this application and not a specific limitation of this application. In other embodiments, X can take other numerical ranges. For example, X can be designed to be from 2°C to 15°C. Of course, X can also be any value between 0°C and 20°C. For example, X can be 5°C, 7°C, 10°C or 12°C, etc., as long as it can keep a certain height while the solder melts. There is no limitation.

[0059] After the temperature of the heat-conducting plate 200 reaches the preset range, the solar cell 400 is placed on the supporting surface of the heat-conducting plate 200 to melt the solder on the solar cell 400. Alternatively, the solar cell 400 can be placed on the supporting surface of the heat-conducting plate 200 first, and then the heat-conducting plate 200 can be heated to the preset range.

[0060] Optionally, the welding equipment is equipped with a robotic arm for picking up and placing the solar cell 400. For example, the robotic arm can place the solar cell 400 onto the heat-conducting plate 200 by gripping or using a suction cup. The heat-conducting plate 200 then heats the solar cell 400, melting the solder on the solar cell 400 and maintaining it at a certain height.

[0061] Then the robotic arm removes the solar cell 400 from the heat-conducting plate 200, allowing the molten solder to solidify. The robotic arm then moves the solar cell 400 to a subsequent workstation, such as the welding station of the welding device, so that the welding device can weld the solder strip to the solidified solder.

[0062] As one possible implementation, the molten solder can be solidified first and then removed by a robotic arm. For example, the heat source 100 (controlled by a processor or temperature control device) first heats the heat-conducting plate 200 to melt the solder. Then, the heat source 100 stops working, causing the temperature of the heat-conducting plate 200 to gradually decrease, thereby solidifying the solder. The robotic arm then removes the solar cell 400 from the heat-conducting plate 200 and moves it to a subsequent workstation.

[0063] It should be noted that the solder referred to in this application is a soldering agent. In practice, various types of soldering agents can be used, such as solder paste, and the preset range also needs to be adjusted according to the type of soldering agent, which will not be elaborated here.

[0064] In this embodiment, the welding equipment includes a solder pre-melting device and a welding device. The solder pre-melting device includes a heat source 100, a heat-conducting plate 200, a temperature detection device 300, and a temperature control device. Since the heat source 100 is in contact with the heat-conducting plate 200, the solar cell 400 can be placed on the surface of the heat-conducting plate 200. The temperature detection device 300 detects the temperature of the heat-conducting plate 200 and outputs the detection result to the temperature control device. The temperature control device controls the heat source 100 according to the detection result, so that the temperature of the heat-conducting plate 200 is within a preset range. The preset range is related to the melting point of the solder, so the heat-conducting plate 200 can conduct heat to the solar cell 400, realizing contact heating of the solar cell 400. This makes the solder on all parts of the solar cell 400 more uniformly heated, and the solder melting process is basically the same. The solidified solder can firmly adhere to the solar cell 400 and retain a certain height, which facilitates subsequent welding and improves the string welding effect.

[0065] Example 2

[0066] In some embodiments, the duration for which the solar cell 400 is placed on the surface of the heat-conducting plate 200 is related to the temperature of the heat-conducting plate 200. In other words, the duration for which the solar cell 400 is heated is related to the temperature of the heat-conducting plate 200.

[0067] In one approach, after the heat-conducting plate 200 is heated to a preset temperature range, the solar cell 400 is placed on it. At this point, the temperature of the heat-conducting plate 200 can be considered constant; therefore, the solder only needs to be placed on the heat-conducting plate 200 for a certain period to melt it. The duration for which the solar cell 400 is placed on the surface of the heat-conducting plate 200 can be controlled to ensure the solder melts without over-melting and losing its height.

[0068] Alternatively, the solar cell 400 can be placed on the supporting surface of the heat-conducting plate 200, and then the heat-conducting plate 200 can be heated, causing its temperature to gradually rise to a preset range. Compared to causing the temperature of the solar cell 400 to rise rapidly, this method can reduce the probability of microcracks appearing in the solar cell 400.

[0069] In practice, the relationship between the duration of the solar cell 400 placed on the surface of the heat-conducting plate 200 and the temperature of the heat-conducting plate 200 is stored in the processor. For example, the duration and temperature are measured through a certain number of experiments and a table is generated and stored. The processor controls the duration of the solar cell 400 placed on the surface of the heat-conducting plate 200 by monitoring the temperature of the heat-conducting plate 200 and combining the table.

[0070] Example 3

[0071] Furthermore, the solder can be solder paste. Due to the diversity of solder paste types, its melting point also varies. The melting point of solder paste is related to the alloy composition of the solder powder. For example, lead-free low-temperature solder paste has a melting point of around 140°C, lead-free medium-temperature solder paste around 180°C, lead-free high-temperature solder paste around 217°C, lead-free ultra-high-temperature solder paste around 260°C, leaded low-temperature solder paste around 180°C, and leaded high-temperature solder paste around 296°C.

[0072] Understandably, a corresponding preset range can be set for each type of solder paste. For example, for lead-free low-temperature solder paste, the preset range can be set to 140°C to 143°C.

[0073] Example 4

[0074] Furthermore, the heat source 100 includes several heating rods or heating wires that are in contact with the heat-conducting plate 200.

[0075] In practice, the heat source 100 consists of several heating rods or heating wires, which heat the heat-conducting plate 200. The heat-conducting plate 200 has a fast temperature rise rate and good heating effect.

[0076] Optionally, several heating rods or heating wires can have the same specifications. Taking heat source 100 as a heating rod as an example, several heating rods have the same specifications, so that the heating efficiency of several heating rods is consistent and the heating effect is consistent, which facilitates temperature rise control.

[0077] In some possible embodiments, several heating rods or heating wires are evenly distributed and in contact with the heat-conducting plate 200. Taking the heat source 100 as a heating rod as an example, the several heating rods are evenly distributed and in contact with the heat-conducting plate 200, so that the heating rods heat the heat-conducting plate 200 more evenly, and thus the heat-conducting plate 200 heats the solar cell 400 more evenly, resulting in a better heating effect.

[0078] Example 5

[0079] Furthermore, the solder pre-melting device also includes an adsorption tank 210, an adsorption interface 220, and an adsorption device (not shown in the figure). The adsorption tank 210 is connected to the adsorption device through the adsorption interface 220. The adsorption tank 210 is located on the side surface of the heat-conducting plate 200 that contacts the solar cell 400.

[0080] The welding method provided in this application also includes:

[0081] Start the adsorption device to adsorb the solar cell 400 onto the adsorption tank 210.

[0082] In implementation, the heat-conducting plate 200 is provided with an adsorption groove 210, which can be regarded as a slot on the bearing surface. The adsorption groove 210 is connected to the adsorption device through the adsorption interface 220, and the adsorption device is electrically connected to the processor. After the solar cell 400 is placed on the surface of the heat-conducting plate 200, the air between the adsorption groove 210 and the solar cell 400 can be absorbed by the adsorption device, so that a negative pressure is formed between the solar cell 400 and the heat-conducting plate 200, so that the solar cell 400 is adsorbed on the heat-conducting plate 200. The heat conducted from the heat-conducting plate 200 to the solar cell 400 is more uniform, the heat transfer effect is better, and the solar cell 400 can also be prevented from warping.

[0083] Example 6

[0084] Furthermore, such as Figure 5 and Figure 6 As shown, the contact surface between the heat-conducting plate 200 and the solar cell 400 is convex.

[0085] It is understood that, in this sixth embodiment, as one method, the solar cell 400 is adsorbed onto the convex surface of the heat-conducting plate 200 through an adsorption device, an adsorption tank 210, and an adsorption interface 220.

[0086] Compared to the significant warping that occurs when the solar cell 400 is heated and cooled on a flat heating plate, this embodiment of the application designs the contact surface between the heat-conducting plate 200 and the solar cell 400 as a convex surface with a certain curvature. This effectively reduces the warping of the solar cell 400 after heating and cooling on the convex surface, ensures the overall flatness of the solar cell 400, and improves the yield of the solar cell 400.

[0087] Example 7

[0088] Furthermore, the solar cell 400 includes a solder area for setting solder, and the contact surface between the heat-conducting plate 200 and the solar cell 400 has locating posts (not shown in the figure);

[0089] The steps of placing the solar cell on the surface of the heat-conducting plate include:

[0090] The solar cell is placed on the contact surface according to the position of the limiting post, so that the adsorption groove 210 on the heat-conducting plate is offset from the solder area on the solar cell.

[0091] In practice, the solder area of ​​the solar cell 400 is used to place the solder. When the solar cell 400 is placed on the heat-conducting plate 200, the limiting post limits the solar cell 400 so that the solar cell 400 is accurately and quickly placed in the predetermined position, thereby offsetting the adsorption tank 210 from the solder area, so that the solder area is in direct contact with the heat-conducting plate 200, thereby quickly transferring heat to the solder area to accelerate the solder melting process, resulting in better heat transfer and higher solder melting efficiency.

[0092] In some embodiments, prior to the step of placing the solar cell on the surface of the heat-conducting plate, the welding method provided in this application includes:

[0093] Solder is applied to the solar cell.

[0094] For example, solder can be applied to the solar cell 400 using a screen printing process. Alternatively, solder can be applied to the solar cell 400 by applying solder paste.

[0095] Screen printing refers to using a screen as a base and creating a screen printing plate with images and text through a photosensitive plate-making method. This method involves printing on the solder area of ​​a solar cell 400 using a screen to ensure that the solder is placed in the solder area. This method is highly efficient.

[0096] Example 8

[0097] Furthermore, the solder pre-melting device includes an automatic optical detector used to monitor the melting of the solder.

[0098] In implementation, the automatic optical detector can be an AOI (Automated Optical Inspection) device. AOI devices are based on optical principles to detect common defects encountered in welding production, thereby monitoring the heating process of the solder or detecting the heating and melting effect of the solder, which can effectively improve the product yield.

[0099] As one implementation method, AOI equipment can detect the melting of solder in real time. The host computer can adjust the temperature control strategy or control the robotic arm to grab the solar cell at the appropriate time based on the detection results, or the system can alarm when the AOI equipment detects poor heating effect.

[0100] For example, when the AOI equipment detects that some of the solder on the solar cell is not fully melted, the host computer adjusts the temperature control strategy, raising the temperature of that area. Conversely, when the AOI equipment detects that some of the solder is over-melted, the host computer adjusts the temperature control strategy, lowering the temperature of that area. Alternatively, the AOI equipment can monitor the melting of the solder on the solar cell in real time. When the solder melting reaches a preset standard, the host computer controls a robotic arm to pick up the solar cell. Or, if the AOI equipment detects that the solder melting effect does not meet the preset standard, the system will issue an alarm.

[0101] Example 9

[0102] Furthermore, a heat-resistant layer is provided on the contact surface between the heat-conducting plate 200 and the solar cell 400.

[0103] In practice, the contact surface between the heat-conducting plate 200 and the solar cell 400 is the aforementioned bearing surface. This bearing surface is provided with a heat-resistant layer, which is used to protect the solar cell 400 and prevent high temperature from damaging the solar cell 400.

[0104] Optionally, the heat-resistant layer can be made of a high-temperature resistant film or a high-temperature resistant coating, such as attaching Teflon tape 230 to the bearing surface of the heat-conducting plate 200, or spraying high-temperature resistant materials such as Teflon onto the bearing surface of the heat-conducting plate 200 to protect the solar cell 400.

[0105] Alternatively, the heat-conducting plate 200 can be made of a material with high thermal conductivity, such as aluminum alloy plate or copper alloy. As another implementation method, the bearing surface of the heat-conducting plate 200 can be subjected to hard anodizing treatment.

[0106] Optionally, the solder pre-melting device involved in this application may also include a self-cleaning mechanism, which can clean the dirt on the heat-conducting plate 200, thereby reducing the probability of the solar cell 400 being contaminated or damaged, and making the solar cell 400 and the heat-conducting plate 200 in closer contact, thus improving the heating effect.

[0107] For example, the self-cleaning mechanism can be a negative pressure vacuum cleaner. Another example is that the self-cleaning structure can be a brush device.

[0108] Example 10

[0109] This invention also provides a battery string manufactured using the welding method described above.

[0110] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the structure and implementation principle of the battery string described above can be referred to the corresponding structure and implementation principle in the aforementioned embodiments one to nine, and will not be repeated here.

[0111] Example 11

[0112] This invention also provides a battery assembly, including the battery string as described above.

[0113] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the structure and implementation principle of the battery assembly described above can be referred to the corresponding structure and implementation principle in the foregoing embodiments one to ten, and will not be repeated here.

[0114] Example 12

[0115] This invention also provides a photovoltaic system, including the battery module as described above.

[0116] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the structure and implementation principle of the photovoltaic system described above can be referred to the corresponding structure and implementation principle in the foregoing embodiments one to eleven, and will not be repeated here.

[0117] The heat-conducting plate in this embodiment can conduct heat to the solar cell, achieving contact heating of the solar cell. This makes the solder in all parts of the solar cell more evenly heated, and the solder melting process is basically the same. The solidified solder can firmly adhere to the solar cell and retain a certain height, which facilitates subsequent welding and improves the stringing effect.

[0118] It is understood that those skilled in the art can combine various implementation methods in the above embodiments under the guidance of the above examples to obtain technical solutions with multiple implementation methods.

[0119] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A welding method, characterized in that, The method is applicable to welding equipment, which includes a solder pre-melting device and a welding device. The solder pre-melting device includes a heat source, a heat-conducting plate, a temperature detection device, and a temperature control device. The heat source is in contact with the heat-conducting plate, the temperature detection device is electrically connected to the temperature control device, and the temperature control device is electrically connected to the heat source; The welding method includes: Start the heat source; The temperature of the heat-conducting plate is detected using the temperature detection device. Based on the detection results of the temperature detection device, the heat source is controlled by the temperature control device so that the temperature of the heat-conducting plate is within a preset range, which is related to the melting point of the solder. The solar cell is placed on the surface of the heat-conducting plate, and the solder on the solar cell is melted. The solder after solidification and melting; The welding device is used to weld the solder strip to the cured solder.

2. The welding method as described in claim 1, characterized in that, The duration for which the solar cell is placed on the surface of the heat-conducting plate is related to the temperature of the heat-conducting plate.

3. The welding method as described in claim 1, characterized in that, The heat source includes several heating rods or heating wires that are in contact with the heat-conducting plate.

4. The welding method as described in claim 1, characterized in that, The solder pre-melting device further includes an adsorption tank, an adsorption interface, and an adsorption device. The adsorption tank is connected to the adsorption device through the adsorption interface. The adsorption tank is located on the side surface of the heat-conducting plate that contacts the solar cell. The method further includes: The adsorption device is activated to adsorb the solar cell into the adsorption tank.

5. The welding method as described in claim 4, characterized in that, The contact surface between the heat-conducting plate and the solar cell is convex.

6. The welding method as described in claim 5, characterized in that, The solar cell includes a solder area for distributing the solder, and the contact surface between the heat-conducting plate and the solar cell has locating posts. The step of placing the solar cell on the surface of the heat-conducting plate includes: The solar cell is placed on the contact surface according to the position of the limiting post, so that the adsorption groove is offset from the solder area.

7. The welding method as described in claim 1, characterized in that, Prior to the step of placing the solar cell on the surface of the heat-conducting plate, the welding method includes: The solder is applied to the solar cell using a screen printing process.

8. The welding method as described in claim 1, characterized in that, The solder pre-melting device includes an automatic optical detector for monitoring the melting of the solder.

9. The welding method as described in claim 1, characterized in that, The contact surface between the heat-conducting plate and the solar cell is provided with a heat-resistant layer.

10. The welding method as described in claim 1, characterized in that, The solder pre-melting device also includes a self-cleaning mechanism for cleaning contaminants on the heat-conducting plate.

11. A battery string, characterized in that, It is manufactured by the welding method as described in any one of claims 1-10.

12. A battery assembly, characterized in that, Includes the battery string as described in claim 11.

13. A photovoltaic system, characterized in that, Includes the battery assembly as described in claim 12.

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