Photovoltaic welding equipment and method for connecting battery piece and welding strip

Abstract

The invention discloses photovoltaic welding equipment and a method for connecting a battery piece and a welding strip. The photovoltaic welding equipment comprises a conveying mechanism and a heating mechanism, the heating mechanism is used for forming a welding thermal field in a welding space, the welding space is provided with an inlet and an outlet, and the conveying mechanism is used for driving a battery string to penetrate through the welding space through the inlet and the outlet. The welding space comprises a first temperature zone, a second temperature zone and a third temperature zone which are sequentially connected, and the unit area thermal power of the heating mechanism in the second temperature zone is larger than the unit area thermal power of the heating mechanism in the first temperature zone and the second temperature zone. According to the photovoltaic welding equipment provided by the embodiment of the invention, the solidification of the glue points on the battery string and the welding of the welding strip can be completed at the same time through a welding thermal field formed by one piece of equipment, and the solidification of the glue points and the welding of the welding strip do not need to be completed step by step, so that the process efficiency is high and the process cost is relatively low.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic, in particular to a photovoltaic welding device and a connection method of a cell and a welding band. BACKGROUND

[0002] Solar cell is the core component in solar power generation system, which converts solar energy into electricity through photoelectric effect. The welding band is a key component for connecting the cell in series and realizing the current conduction of the cell. When connecting the cell and the welding band, the cell and the welding band are usually stacked and accurately positioned through the specific mechanical structure of the welding machine, and then conveyed to the welding station through the conveying belt. The welding mechanism is arranged on the welding station, and the current is collected and transmitted by melting the solder on the surface of the welding band and forming an alloy with the silver paste on the grid line of the cell through the high-temperature heat source. The alloy plays two roles, one is to interconnect the cell and the welding band through the fixing force of the alloy, and the other is to collect and transmit the current on the cell. The main advantages of the main grid-free interconnection packaging technology (0BB technology) include significantly reducing the amount of silver paste, reducing the light loss, shortening the current transmission path, reducing the series resistance, thereby improving the power of the component and reducing the cost. In order to ensure that the fine grid and the welding band have sufficient fixing force to support the process production requirements, the welding dispensing process is used to connect the cell and the welding band in the related technology.

[0003] However, in the welding dispensing process in the related technology, dispensing and welding are carried out in steps, which leads to low process efficiency and high equipment investment cost due to the large number of process steps. SUMMARY

[0004] The purpose of the present application includes providing a photovoltaic welding device and a connection method of a cell and a welding band, which can improve the connection efficiency of the cell and the welding band, and has low process cost.

[0005] Embodiments of the present application can be implemented as follows: In a first aspect, the present application provides a photovoltaic welding device for welding a welding band and a cell in a cell string, the photovoltaic welding device forms a welding space, the photovoltaic welding device includes a conveying mechanism and a heating mechanism, the heating mechanism is used to form a welding heat field in the welding space, the welding space has an inlet and an outlet, the conveying mechanism is used to drive the cell string to pass through the welding space through the inlet and the outlet, along the conveying direction of the conveying mechanism, the welding space includes a first temperature zone, a second temperature zone and a third temperature zone connected in sequence, and the unit area heat power of the heating mechanism in the second temperature zone is greater than the unit area heat power of the heating mechanism in the first temperature zone and the second temperature zone.

[0006] In an optional embodiment, the heating mechanism comprises a top heating assembly and a bottom heating assembly, and the welding space is formed between the top heating assembly and the bottom heating assembly.

[0007] In an optional embodiment, the top heating assembly comprises a plurality of infrared lamp tubes arranged along the conveying direction, and the arrangement density of the infrared lamp tubes in the second temperature zone is greater than that of the infrared lamp tubes in the first temperature zone and the third temperature zone.

[0008] In an optional embodiment, the first temperature zone has a starting section adjacent to the inlet, and the arrangement density of the infrared lamp tubes corresponding to the starting section is less than that of the infrared lamp tubes corresponding to other positions in the first temperature zone.

[0009] In an optional embodiment, the bottom heating assembly comprises a plurality of heating rods arranged along the conveying direction.

[0010] In an optional embodiment, the photovoltaic welding device further comprises an exhaust fan, and the exhaust fan is used to exhaust hot air in the welding space.

[0011] In an optional embodiment, the photovoltaic welding device comprises a plurality of exhaust fans, and the exhaust fans are arranged above the top heating assembly, and the first temperature zone, the second temperature zone and the third temperature zone are respectively opposite to at least one exhaust fan in the vertical direction.

[0012] In an optional embodiment, the conveying mechanism comprises a conveying belt and a driving member, the driving member is in transmission connection with the conveying belt, the conveying belt is attached to the surface of the bottom heating assembly, and the conveying belt is used to carry the battery string.

[0013] In an optional embodiment, the photovoltaic welding device further comprises a temperature detection assembly, and the temperature detection assembly is used to detect the temperature of the first temperature zone, the second temperature zone and the third temperature zone.

[0014] In an optional embodiment, the photovoltaic welding device further comprises a control device, the temperature detection assembly and the heating mechanism are electrically connected with the control device, and the control device is used to adjust the power of the heating mechanism according to the information fed back by the temperature detection assembly.

[0015] In an optional embodiment, the lengths of the first temperature zone, the second temperature zone and the third temperature zone in the conveying direction are sequentially shortened.

[0016] In an optional embodiment, the length ratio of the first temperature zone, the second temperature zone and the third temperature zone is (5-12):(3-6):2.

[0017] In an optional embodiment, the length of the welding space in the conveying direction is 600-2000mm.

[0018] In a second aspect, the application provides a method for connecting a cell and a solder ribbon, which is welded by using the photovoltaic welding device in any of the foregoing embodiments, and the method comprises: connecting the solder ribbon with the uncured glue point on the cell, and making the solder ribbon contact the grid line on the cell; controlling the conveying mechanism to convey the solder ribbon and the cell through the welding space, so that the glue point is gradually cured in the welding heat field formed by the heating mechanism, and the solder ribbon and the grid line are welded and connected in the welding heat field.

[0019] The photovoltaic welding device and the method for connecting a cell and a solder ribbon provided by the embodiments of the application have the following beneficial effects: The photovoltaic welding device provided by the application forms a welding space, and the photovoltaic welding device comprises a conveying mechanism and a heating mechanism. The heating mechanism is used to form a welding heat field in the welding space. The welding space has an inlet and an outlet. The conveying mechanism is used to drive a cell string to pass through the welding space through the inlet and the outlet. In the conveying direction of the conveying mechanism, the welding space comprises a first temperature zone, a second temperature zone and a third temperature zone connected in sequence. The unit area heat power of the heating mechanism in the second temperature zone is greater than the unit area heat power of the heating mechanism in the first temperature zone and the second temperature zone. Because the unit area heat power of the heating mechanism in the second temperature zone is greater than the unit area heat power of the heating mechanism in the first temperature zone and the second temperature zone, the cell string can be at a relatively low temperature in the first temperature zone, and the uncured glue point for pre-fixing the cell and the solder ribbon can be gradually cured in the first temperature zone. The cell string can rise to a peak temperature in the second temperature zone, which can meet the welding requirements. Therefore, the solder ribbon and the grid line of the cell are welded in the second temperature zone, and the glue point can be completely cured in the second temperature zone. The unit area heat power in the third temperature zone is relatively low compared with the second temperature zone. Therefore, the temperature of the cell string decreases in the third temperature zone, and the cell string can release internal stress (especially stress at the welding position) in the third temperature zone, thereby ensuring the reliability of the cell string welding. It can be seen that the photovoltaic welding device provided by the embodiments of the application can simultaneously complete the curing of the glue point on the cell string and the welding of the solder ribbon through a welding heat field formed by one device, without completing the curing of the glue point and the welding of the solder ribbon in steps. Therefore, the process efficiency is high and the process cost is low.

[0020] The method for connecting a cell and a solder ribbon provided by the embodiments of the application can be realized by the photovoltaic welding device described above, and therefore has the advantages of high process efficiency and low process cost. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be regarded as a limitation to the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0022] Figure 1 A schematic diagram of a photovoltaic welding device in an embodiment of the present application; Figure 2 A partial schematic diagram of a cell string in an embodiment of the present application; Figure 3 A schematic diagram of the connection of a glue dot, a grid line and a solder strip on a cell surface in an embodiment of the present application; Figure 4 A schematic diagram of the cross section of the bonding position of a glue dot and a solder strip in an embodiment of the present application; Figure 5 A block diagram of a photovoltaic welding device in an embodiment of the present application; Figure 6 A flow chart of a cell and a solder strip connection method in an embodiment of the present application; Figure 7 A schematic diagram of the temperature change of a cell string in the process of passing through a welding heat field in an embodiment of the present application.

[0023] Figure legend: 100 - conveying mechanism; 110 - conveying belt; 200 - heating mechanism; 201 - welding space; 202 - inlet; 203 - outlet; 210 - top heating component; 211 - infrared lamp tube; 220 - bottom heating component; 230 - first temperature zone; 231 - initial section; 232 - transition section; 240 - second temperature zone; 250 - third temperature zone; 300 - exhaust fan; 400 - temperature detection component; 500 - control device; 600 - cell string; 610 - cell; 611 - grid line; 620 - solder strip; 630 - glue dot. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0025] The following detailed description of embodiments of the application in the drawings attached hereto is included to provide a thorough understanding of the application. Descriptions of well-known functions and constructions can be omitted to avoid obscuring the application. Other embodiments of the application can be utilized and derived therefrom, such that structural and operational changes relating to the particular embodiments described herein are within the scope of the application, without departing from the scope of the application. Thus, for example, insomuch as the application relates to a method of manufacturing a semiconductor device, it is to be understood that the application is equally applicable to the manufacture of other devices, and that the application is not limited to the manufacture of semiconductor devices.

[0026] It should be noted that like reference numerals and letters refer to like items in the drawings, and as a result, once an item is defined in one drawing, it need not be further defined and explained in subsequent drawings.

[0027] In the description of the application, it should be noted that the terms "upper", "lower", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the application is usually placed, and are only for the convenience of describing the application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application.

[0028] In addition, the terms "first", "second", and the like appear only for the purpose of distinguishing descriptions, and cannot be understood as indicating or implying relative importance.

[0029] It should be noted that the features in the embodiments of the application can be combined with each other without conflict.

[0030] In the related art, the connection between the battery piece and the welding strip is realized by the dispensing process and the welding process, and finally the welding strip connects multiple battery pieces in series or parallel to form a battery string. However, in the related art, the curing of the glue point after dispensing and welding are carried out by different devices, for example, the curing device is used first to allow the glue to cure, and then the battery string is transported to the welding device for welding to allow the grid lines on the battery piece to be alloyed with the welding strip. Alternatively, after the welding strip and the grid lines on the battery piece are welded, the welding strip is reinforced by dispensing and curing. However, the dispensing and curing process in the related art is carried out in steps and uses different devices, resulting in low process efficiency, high process cost, and large space occupation of the workstations.

[0031] In order to improve at least one of the above-mentioned deficiencies in the related art, the embodiments of the application provide a photovoltaic welding device capable of realizing the curing of the glue point and the welding of the welding strip in the same welding thermal field, thereby improving the process efficiency, reducing the process cost, and reducing the space occupation.

[0032] Figure 1 A schematic view of a photovoltaic welding device in an embodiment of the application is shown in FIG. 1. As shown in FIG. 1, the photovoltaic welding device comprises a welding thermal field 1, a dispensing device 2, and a curing device 3. Figure 1As shown, the photovoltaic welding device forms a welding space 201, and the photovoltaic welding device comprises a conveying mechanism 100 and a heating mechanism 200, and the heating mechanism 200 is used to form a welding heat field in the welding space 201. The welding space 201 has an inlet 202 and an outlet 203, and the conveying mechanism 100 is used to drive the cell string 600 to pass through the welding space 201 through the inlet 202 and the outlet 203, and the welding space 201 comprises a first temperature zone 230, a second temperature zone 240 and a third temperature zone 250 connected in sequence in the conveying direction of the conveying mechanism 100, and the unit area heat power of the heating mechanism 200 in the second temperature zone 240 is greater than the unit area heat power of the heating mechanism 200 in the first temperature zone 230 and the second temperature zone 240. It should be understood that the unit area heat power of the heating mechanism 200 in the second temperature zone 240 is greater than the unit area heat power of the heating mechanism 200 in the first temperature zone 230 and the second temperature zone 240, which means that the cell string 600 on the conveying mechanism 100 can absorb heat from the heating mechanism 200 in unit time per unit area. It should be understood that the heat transfer mode of the heating mechanism 200 to the cell sheet 610 is mainly thermal radiation, supplemented by heat conduction, and there is a small amount of convective heat transfer (convective heat transfer of hot air in the welding space 201).

[0033] Figure 2 A partial view of the cell string 600 in an embodiment of the present application is shown. Figure 3 A schematic view of the connection between the glue point 630, the grid line 611 and the solder strip 620 on the surface of the cell sheet 610 in an embodiment of the present application is shown. Figure 2 And Figure 3 As shown, in an embodiment of the present application, the cell string 600 comprises the cell sheet 610 and the solder strip 620, and before the cell sheet 610 and the solder strip 620 are welded, the cell sheet 610 and the solder strip 620 can be pre-fixed by the glue point 630, that is, the glue point 630 adheres and fixes the solder strip 620 and the cell sheet 610 by its own adhesion, so as to prevent the cell sheet 610 and the solder strip 620 from slipping relative to each other during subsequent transportation and welding, so that the solder strip 620 can be accurately connected to a specific position on the cell sheet 610, and the welding effect of the solder strip 620 is ensured. Optionally, the front surface and the back surface of the cell sheet 610 are both provided with the grid line 611, the front surface of one of the two adjacent cell sheets 610 is adhered and connected to the solder strip 620, and the back surface of the other of the two adjacent cell sheets 610 is adhered and connected to the solder strip 620; it should be understood that the above-mentioned "adhered and connected" is realized by the un-solidified glue point 630. The solder strip 620 is bent between the two adjacent cell sheets 610, so that a part of the solder strip 620 is overlapped on the front surface of one of the cell sheets 610, and the other part of the solder strip 620 is attached to the back surface of the other cell sheet 610. Figure 2Only two battery pieces 610 and one solder strip 620 are shown to be connected, it can be understood that the battery string 600 composed of battery pieces 610 and solder strips 620 can include more battery pieces 610 and more solder strips 620.

[0034] Figure 4 A cross-sectional view of the bonding position of the glue dot 630 and the solder strip 620 in an embodiment of the present application is shown. As shown, in the thickness direction of the battery piece 610, the glue dot 630 has a certain height, and the solder strip 620 is sunk into the glue dot 630 along the thickness direction of the battery piece 610. Figure 4

[0035] When the battery string 600 to be welded (at this time, the glue dot 630 is not cured, and the solder strip 620 is not connected with the grid line 611) enters the welding space 201 from the entrance 202, and under the conveying of the conveying mechanism 100, passes through the welding space 201 along the preset path, and finally can be sent out of the welding space 201 from the exit 203. During the whole process in the welding space 201, the battery string 600 is in the welding heat field formed by the heating mechanism 200, and in the first temperature zone 230, the battery string 600 is at a lower temperature, in the second temperature zone 240, the battery string 600 rises to a higher temperature, and in the third temperature zone 250, the battery string 600 gradually cools down. During the whole process, the battery string 600 is completely welded and the glue dot 630 is cured.

[0036] In the embodiment, the heating mechanism 200 includes a top heating assembly 210 and a bottom heating assembly 220, and the welding space 201 is formed between the top heating assembly 210 and the bottom heating assembly 220. The top heating assembly 210 and the bottom heating assembly 220 are arranged in a vertical direction; the entrance 202 and the exit 203 of the welding space 201 are opposite in a horizontal direction.

[0037] ​Further, the top heating assembly 210 comprises a plurality of infrared lamp tubes 211 arranged along the conveying direction, the arrangement density of the infrared lamp tubes 211 in the second temperature zone 240 is greater than that in the first temperature zone 230 and the third temperature zone 250. By setting the arrangement density of the infrared lamp tubes 211 in the first temperature zone 230 and the third temperature zone 250 to be less than that in the second temperature zone 240, the temperature of the battery string 600 in the first temperature zone 230 and the third temperature zone 250 is lower than that in the second temperature zone 240 when the power of the single infrared lamp tube 211 is the same. The temperature of the battery string 600 in the second temperature zone 240 is high enough to enable the grid lines 611 on the battery sheet 610 to be welded with the solder strip 620, while the temperature in the first temperature zone 230 and the second temperature zone 240 is lower but higher than room temperature, which can avoid damage to the battery sheet 610 due to too fast temperature change and too large thermal stress. In addition, the first temperature zone 230 is at a lower temperature, which can provide sufficient time for the curing of the glue dots 630, and will not affect the subsequent welding effect due to the volatilization of the flux on the solder strip 620, and will also avoid the volatilization of the flux affecting the adhesion of the glue dots 630. It should be understood that the top heating assembly 210 is spaced from the battery string 600, and the top heating assembly 210 mainly transfers heat to the battery string 600 in the form of heat radiation; the top heating assembly 210 can also heat the air in the welding space 201, and the hot air exchanges heat with the battery string 600 by heat conduction and convection.

[0038] In the embodiment, the first temperature zone 230 has a starting section 231 adjacent to the inlet 202, the length of the starting section 231 accounts for more than 25% of the length of the first temperature zone 230, and the arrangement density of the infrared lamp tubes 211 corresponding to the starting section 231 is less than that of the infrared lamp tubes 211 corresponding to other positions of the first temperature zone 230. By reducing the arrangement density of the infrared lamp tubes 211 in the starting section 231, the starting section 231 has a lower temperature under the condition that the overall temperature of the first temperature zone 230 is lower, which can further reduce the volatilization of the flux on the solder strip 620. In the embodiment, the first temperature zone 230 is composed of the starting section 231 and a transition section 232, the length of the starting section 231 is shorter than that of the transition section 232, and the starting section 231 accounts for 25%-50% of the length of the first temperature zone 230.

[0039] In the embodiment, the bottom heating assembly 220 is a heating bottom plate, which comprises a plurality of heating rods arranged along the conveying direction. The heating rods are provided with electric heating elements, which can heat the heating rods by electric heating, and the temperature of the heating rods can be adjusted by controlling the current, so as to adjust the temperature of the battery string 600.

[0040] Figure 5This is a block diagram of the photovoltaic welding equipment in one embodiment of this application. Figure 5 As shown, the photovoltaic welding equipment provided in this application also includes a control device 500 and a temperature detection component 400. The temperature detection component 400 is used to detect the temperatures of the first temperature zone 230, the second temperature zone 240, and the third temperature zone 250. Optionally, the temperature detection component 400 includes a thermocouple. The temperature detection component 400 and the heating mechanism 200 are both electrically connected to the control device 500. The control device 500 is used to adjust the power of the heating mechanism 200 based on the information fed back by the temperature detection component 400. That is, the temperature of the infrared lamps 211 in the first temperature zone 230, the second temperature zone 240, and the third temperature zone 250 can be adjusted independently, and the power of the bottom heating components 220 in different temperature zones can also be adjusted independently. Through the cooperation of the control device 500, the temperature detection component 400, and the heating mechanism 200, the temperature trend can be precisely controlled during the movement of the battery string 600 in the welding space 201, thereby precisely controlling the holding time of the battery string 600 at different temperatures, thus ensuring the welding and curing effect of the adhesive dots 630.

[0041] In this embodiment, the photovoltaic welding equipment also includes an exhaust fan 300, which is used to exhaust hot air from the welding space 201. The exhaust fan 300 can expel excess hot air, thereby cooling the battery string 600 to a certain extent; when the battery string 600 temperature is too high, the exhaust fan 300 can be turned on. The photovoltaic welding equipment includes multiple exhaust fans 300, which are positioned above the top heating component 210. The first temperature zone 230, the second temperature zone 240, and the third temperature zone 250 are vertically opposite at least one exhaust fan 300. Figure 1 In this embodiment, the exhaust fan 300 is directed upwards, and the airflow passes through the gap between the infrared lamps 211 from bottom to top, thereby exiting the welding space 201. Optionally, the exhaust fan 300 is electrically connected to the control device 500, and the exhaust fans 300 in different temperature zones can be controlled independently, which is beneficial for achieving precise temperature control of the battery string 600 in different temperature zones.

[0042] In this embodiment, the conveying mechanism 100 includes a conveyor belt 110 and a drive member. The drive member is drively connected to the conveyor belt 110. The conveyor belt 110 is attached to the surface of the bottom heating assembly 220 and is used to carry the battery string 600. The bottom heating assembly 220 can transfer heat to the conveyor belt 110 through thermal conduction, and then the conveyor belt 110 transfers the heat to the battery string 600. In this embodiment, the drive member of the conveying mechanism 100 is electrically connected to the control device 500, so that the control device 500 can control the conveying speed of the conveying mechanism 100 as needed, and thus control the residence time of the battery string 600 in different temperature zones.

[0043] Optionally, the lengths of the first temperature zone 230, the second temperature zone 240 and the third temperature zone 250 are sequentially shortened along the conveying direction. By setting the first temperature zone 230 to be longer, the length of time that the battery string 600 stays in the first temperature zone 230 can be increased, so that the glue point 630 has sufficient time to complete the pre-curing, and the uniformity of the internal and external curing is ensured, and the reliability of the finally cured glue point 630 is improved; the temperature of the second temperature zone 240 is relatively high, and the time is relatively shortened, so that the process efficiency can be improved under the premise of ensuring the completion of welding and complete curing of the glue, and the negative effects of long time high temperature on the battery piece 610 are also reduced; the third temperature zone 250 is used for releasing stress at the welding position. Under the action of releasing stress, the length of time that the battery string 600 stays in the third temperature zone 250 is appropriately shortened, so that the process efficiency can be improved. Optionally, the length ratio of the first temperature zone 230, the second temperature zone 240 and the third temperature zone 250 is 6:3:1. It can be understood that, in the case that the battery string 600 moves at a constant speed, the length ratio of the first temperature zone 230, the second temperature zone 240 and the third temperature zone 250 is the ratio of the length of time that the battery string 600 stays in the first temperature zone 230, the second temperature zone 240 and the third temperature zone 250. Optionally, the length of the welding space 201 is 600-2000 mm along the conveying direction; in the embodiment, the size of the welding space 201 is not greater than 2 m, so that the space occupation of the equipment can be saved. It should be understood that, in other optional embodiments, the lengths and ratios of the first temperature zone 230, the second temperature zone 240 and the third temperature zone 250 can be set as needed, such as the lengths of the second temperature zone 240, the first temperature zone 230 and the third temperature zone 250 are sequentially increased; or the second temperature zone 240 and the first temperature zone 230 are equal in length, and the third temperature zone 250 is longer than either the first temperature zone 230 or the second temperature zone 240.

[0044] Figure 6 A flowchart of a method for connecting a battery piece and a solder strip in an embodiment of the present application is shown in FIG. 10. As shown in FIG. 10, the method for connecting a battery piece and a solder strip provided by the embodiment of the present application can be implemented by the photovoltaic welding device described above. The method for connecting a battery piece and a solder strip includes the following steps: Figure 6 Step S100, connecting the solder strip 620 and the uncured glue point 630 on the battery piece 610, and making the solder strip 620 contact the grid line 611 on the battery piece 610.

[0045] Optionally, the battery piece 610 and the solder strip 620 are connected in the manner as shown in FIG. 11; in other embodiments, the connection form of the solder strip 620 and the battery piece 610 is not limited to Figure 2 Figure 3 Figure 2 ​​​In the shown form, the solder strips 620 can be connected to the same side of the respective battery sheet 610, for example. The uncured glue dots 630 are formed by glue, which is thermosetting glue; optionally, the thermosetting glue has a thermal initiation temperature of 50-200°C.

[0046] Optionally, the components of the uncured glue dots 630 (i.e. the thermosetting glue) include vinyl-terminated dimethyl (siloxane and polysiloxane), dimethyl methyl hydrogen (siloxane and polysiloxane), and a reaction product of dimethyl (siloxane and polysiloxane) and silicon dioxide. Optionally, the uncured glue dots 630 contain 50-70% of vinyl-terminated dimethyl (siloxane and polysiloxane), 20-40% of dimethyl methyl hydrogen (siloxane and polysiloxane), and 1-10% of the reaction product of dimethyl (siloxane and polysiloxane) and silicon dioxide, by mass percentage. The above components can be searched by the registration number of the Chemical Abstracts Service (CAS), wherein the registration number of the vinyl-terminated dimethyl (siloxane and polysiloxane) is CAS No. 68083-19-2, the registration number of the dimethyl methyl hydrogen (siloxane and polysiloxane) is CAS No. 68037-59-2, and the registration number of the reaction product of dimethyl (siloxane and polysiloxane) and silicon dioxide is CAS No. 67762-90-7.

[0047] By selecting the components of the thermosetting glue, the thermosetting glue has a suitable thermal initiation temperature, which can match the subsequent soldering process between the solder strips 620 and the grid lines 611, so as to ensure that the curing of the glue dots 630 and the soldering of the solder strips 620 do not interfere with each other, thereby ensuring the connection performance (including structural bonding reliability and electrical connection reliability) of the battery sheets 610 and the solder strips 620. It should be understood that in alternative embodiments, other glues that match the soldering process can also be selected to form the glue dots 630; that is, the components of the glue dots 630 can be replaced as needed, and the content can be adjusted as needed.

[0048] As Figure 4As shown, the solder strip 620 is in contact with the surface of the battery sheet 610, or the solder strip 620 has a gap with the surface of the battery sheet 610, and the gap is filled with the glue. In order to ensure that the glue spot 630 has better bonding force with the solder strip 620, the glue spot 630 can be wrapped around the bonding part of the solder strip 620 in the circumferential direction of the solder strip 620. Alternatively, the bonding part of the solder strip 620 is covered by the glue spot 630, and the central angle A of the bonding part around the solder strip 620 in the circumferential direction is greater than a preset angle value. The preset angle value can be any value between 100° and 360°, such as 120°, 150°, 180°, 210°, 240°, 270°, 300°, 330° or 360°. When the value of the central angle A is 360°, it means that the glue spot 630 completely wraps the bonding part of the solder strip 620 in the circumferential direction of the solder strip 620.

[0049] In the embodiment of the present application, the step of connecting the solder strip 620 with the uncured glue spot 630 on the battery sheet 610 and making the solder strip 620 contact the grid line 611 on the battery sheet 610 can specifically include: Step S110, printing the glue spot 630 on the surface of the battery sheet 610.

[0050] Optionally, before printing the glue spot 630, the battery sheet 610 can be positioned by a visual inspection system, and then the printing of the glue spot 630 is performed on the front and back surfaces of the battery sheet 610. The number of glue spots 630 can be selected as needed. In the case of a larger size of the battery sheet 610 and a larger number of solder strips 620, more glue spots 630 can be printed to improve the reliability of the pre-fixing. It should be noted that the glue spot 630 will block the light irradiated on the battery sheet 610 to a certain extent, and too many glue spots 630 can reduce the light entering the battery sheet 610, resulting in a decrease in the battery efficiency of the battery sheet 610. Therefore, the number of glue spots 630 needs to be determined by comprehensively considering the connection reliability and the battery efficiency.

[0051] Optionally, the application position of the glue spot 630 is distributed between the grid lines 611 (as shown in the figure); the glue spot 630 can be in contact with or not in contact with the grid line 611; or the glue spot 630 can also cover part of the grid line 611. Figure 3

[0052] Step S120, overlapping the solder strip 620 on the battery sheet 610, so that the solder strip 620 is connected to the battery sheet 610 through the glue spot 630, and the solder strip 620 abuts against the grid line 611.

[0053] ​In the case that the glue points 630 are distributed between the grid lines 611, the bonding sites of the solder strip 620 for bonding with the battery piece 610 and the soldering sites for soldering with the grid lines 611 are different sites spaced from each other. In the embodiment of the present application, the bonding sites of the solder strip 620 are bonded with the surface of the battery piece 610 through the un-solidified glue points 630, and the surface of the battery piece 610 is formed by a passivation layer or a transparent conductive layer according to different types of the battery piece 610. The grid lines 611 on the battery piece 610 protrude from the surface of the battery piece 610, so the solder strip 620 will lap on the grid lines 611, contact with the grid lines 611, and there is a certain pre-pressure between the solder strip 620 and the grid lines 611, thereby ensuring the subsequent soldering effect.

[0054] In the embodiment of the present application, the cross section of the solder strip 620 is circular; in alternative embodiments, the cross section of the solder strip 620 can also be elliptical, polygonal or other irregular shapes.

[0055] Optionally, the solder strip 620 comprises a copper core and a plating layer wrapped on the surface of the copper core, and the plating layer is a tin-lead alloy or a tin-lead-bismuth alloy. The plating layer is formed by electroplating or hot-dip plating process, and the molten SnPb or SnPbBi alloy solidifies on the surface of the copper core to form a continuous metal alloy layer covering the entire surface of the copper core. The thickness of the plating layer is usually between several microns and tens of microns, for example, the thickness is 10-30 μm. The main function of the alloy plating layer of the solder strip 620 is to protect the copper matrix from oxidation and to provide a soldering interface. Since tin and its alloys are relatively stable in the atmosphere, they can effectively prevent the internal copper from being oxidized and blackened, thereby ensuring good weldability and electrical conductivity. During the soldering process, the alloy plating layer with a relatively low melting point will melt first to form a reliable solder joint on the grid lines 611 of the battery piece 610.

[0056] Optionally, after the connection (i.e. pre-fixing) of the solder strip 620 and the battery piece 610 is completed, a pressing block (not shown in the figure) can be further placed on the solder strip 620 to press the solder strip 620 against the grid lines 611, and the pressing block will pass through the soldering heat field together with the battery piece 610 and the solder strip 620 in the subsequent soldering process. It can be understood that when the solder strip 620 laps on the glue points 630, there can be a gap between the solder strip 620 and the grid lines 611 of the battery piece 610 or a too small contact area due to the relatively high height of the glue points 630, which will affect the soldering effect between the grid lines 611 and the solder strip 620 in the subsequent soldering. By placing the pressing block on the solder strip 620, the pressing block can exert a downward pressure on the solder strip 620 to ensure that the solder strip 620 and the grid lines 611 can be closely abutted before soldering, thereby ensuring that the problem of false welding is less likely to occur subsequently.

[0057] In the embodiments of the present application, before the welding strip 620 is connected to the non-solidified glue point 630 on the battery piece 610, the method for connecting the battery piece and the welding strip also includes applying flux on the welding strip 620. Specifically, before the welding strip 620 is overlapped on the battery piece 610, flux is applied on the welding strip 620, and the position of the flux application should at least cover the welding position of the welding strip 620, or the entire welding strip 620 is coated with flux. The main purpose of the flux is to ensure that the welding process is carried out smoothly and a high-reliability and low-resistance welding point is formed. Specifically, whether it is the alloy plating layer of the welding strip 620 or the grid line 611 on the battery piece 610, a very thin oxide film can be formed in the air, and this oxide film will hinder the direct contact between the molten solder and the base metal (such as the grid line 611 and the welding strip 620). The active agent (usually organic acid or halide) in the flux can chemically react with these oxides at the welding temperature, dissolve or reduce them into easily removable substances, thereby exposing the clean and active metal surface, creating the necessary conditions for the formation of metallurgical bonding between the molten solder and the base metal. Secondly, the molten solder (i.e. the plating layer on the welding strip 620 after melting) has a high surface tension and tends to gather into a spherical shape, which is not easy to spread on the metal surface. However, the flux can effectively reduce the surface tension of the molten solder, so that it can better wet the surface of the welding strip 620 itself and the grid line 611, uniformly spread and fill into the small gaps of the contact surface, form a continuous, smooth and well-covered welding point, and ensure the maximum contact area. Further, the welding is carried out at a high temperature, and the metal surface exposed to the air will be rapidly re-oxidized at this high temperature. The molten flux forms a liquid protective film covering the heated metal surface and the molten solder, which isolates the air (oxygen) and effectively prevents the welding site from being re-oxidized at high temperature, ensuring the cleanliness of the welding interface. In addition, the flux itself is a fluid, which helps to more evenly transfer the heat of the welding heat source (usually infrared radiation or hot air) to the contact interface of the welding strip 620 and the grid line 611, promoting the interface temperature of the plating layer of the welding strip 620 and the grid line 611 to quickly and uniformly reach the melting point required for welding, which helps to form a uniform and consistent welding point. Moreover, by improving the wettability and removing the oxide film, the flux enables good welding results at relatively lower temperatures and shorter heating times, which is beneficial to prevent the thin and brittle battery piece 610 from being cracked or broken due to excessive thermal stress.

[0058] Optionally, the components of the flux include a film-forming agent, succinic acid and a solvent. Further, the solvent can include an alcohol solvent and / or deionized water. The film-forming agent can be selected from dipropylene glycol methyl ether (registration number CAS. No. 34590-94-8), and the alcohol solvent can be isopropyl alcohol (registration number CAS. No. 67-63-0). Optionally, the activation temperature of the flux is 100-170°C.

[0059] In step S200, the conveying mechanism 100 conveys the solder strip 620 and the battery piece 610 through the welding space 201, so that the glue point 630 gradually solidifies in the welding heat field formed by the heating mechanism 200, and the solder strip 620 and the grid line 611 are welded and connected in the welding heat field.

[0060] As shown in FIG. 6, in the embodiment, the battery string 600 after the pre-fixing is driven by the conveying mechanism 100 to move along a preset path, and passes through a continuous welding heat field during the movement, so that the fixing of the glue point 630 and the welding of the solder strip 620 and the grid line 611 are completed in the welding heat field. Along the conveying direction, the temperature in the welding heat field changes, so that the temperature of the battery string 600 being conveyed can first rise and then fall. Figure 1

[0061] In the embodiment, the temperature of the battery piece 610 gradually rises during the movement in the first temperature zone 230, the temperature of the battery piece 610 first rises and then falls during the movement in the second temperature zone 240, and the temperature of the battery piece 610 gradually falls during the movement in the third temperature zone 250. In the first temperature zone 230, the glue point 630 can be pre-solidified, that is, the solvent volatilizes, the viscosity significantly decreases, and the adhesion significantly increases. In the second temperature zone 240, as the temperature further rises, the glue point 630 completes the solidification, and the welding of the solder strip 620 and the grid line 611 is completed. In the third temperature zone 250, the temperature gradually decreases, and stress can be gradually released in the process, thereby ensuring the reliability of the device.

[0062] Figure 7 FIG. 7 shows a schematic diagram of the temperature change of the battery string 600 during the movement through the welding heat field in the embodiment. As shown in FIG. 7, the vertical coordinate of the curve is the temperature, and the horizontal coordinate is the time; two dashed lines in the figure represent the time t1 when the battery string 600 reaches the boundary between the first temperature zone 230 and the second temperature zone 240, and the time t2 when the battery piece 610 reaches the boundary between the second temperature zone 240 and the third temperature zone 250. Alternatively, the temperature of the battery string 600 in the first temperature zone 230 is 50-150°C, the temperature of the battery string 600 in the second temperature zone 240 is 100-240°C, and the temperature of the battery string 600 in the third temperature zone 250 is 80-150°C. Further, the average temperature of the battery string 600 in the first temperature zone 230, the average temperature of the battery string 600 in the third temperature zone 250, and the average temperature of the battery string 600 in the second temperature zone 240 increase in turn. Figure 7

[0063] ​​The temperature setting scheme described above makes the glue reach the thermal initiation temperature, and the glue point 630 starts to solidify when the battery piece 610 is in the first temperature zone 230. However, due to the low temperature, the amount of flux volatilized on the solder strip 620 is small, which can ensure that there is enough flux remaining after entering the high temperature. For the solidification of the glue point 630, on the one hand, the volatilization rate of the flux in the first temperature zone 230 is low, so that the glue point 630 which is not completely solidified is not easily impacted by the volatilized gas of the flux, which is beneficial to the solidification and formation of the glue point 630; on the other hand, the temperature of the first temperature zone 230 is relatively low, so that the difference between the internal and external solidification rates of the glue point 630 is reduced, which is beneficial to the escape of volatile components (such as solvents) in the inside of the glue point 630, and avoids the blockage of the internal volatile components to the outside when the inside of the glue point 630 is rapidly solidified from the outside to the inside. Therefore, the risk of destroying the pre-solidified part due to the volatilized components of the glue point 630 or reducing the adhesion due to the difficulty of the volatilized components to escape is reduced.

[0064] In addition, in the first temperature zone 230, there is a "low temperature" welding between the solder strip 620 and the grid line 611, which is beneficial to improve the density of the welding alloy, thereby improving the bonding force and conductivity between the solder strip 620 and the grid line 611.

[0065] In the present embodiment, since the heating mechanism 200 has a lower lamp arrangement density at the starting section 231 of the first temperature zone 230, the temperature of the battery string 600 is lower in the starting section 231 after entering the welding space 201. Figure 7 In the present embodiment, the temperature of the battery string 600 is lower in the starting section 231 after entering the welding space 201. The starting section 231 of the first temperature zone 230 is an interval extending a preset distance in the conveying direction from the entrance 202; in the present embodiment, the preset distance is not less than 25% of the length of the first temperature zone 230. Alternatively, the temperature of the battery string 600 when in the starting section 231 of the first temperature zone 230 is 100°C or lower; further alternatively, the temperature of the battery string 600 when in the starting section of the first temperature zone 230 is 85°C or lower. By further reducing the temperature of the battery string 600 in the starting section 231 of the first temperature zone 230 (such as about 20°C lower than other sections of the first temperature zone 230), the volatilization of the flux can be further reduced, the protection of the glue point 630 which is not completely solidified is better, and it is beneficial to obtain a solidified glue point 630 with better adhesion. In addition, the starting section can play a role in preheating, avoiding the generation of thermal damage to the battery piece 610 due to the too high instantaneous heating power / temperature.

[0066] Alternatively, the temperature of the battery string 600 when at the junction of the first temperature zone 230 and the second temperature zone 240 is 100-150°C.

[0067] Optionally, the heating mechanism 200 can be controlled to ensure that the temperature rising rate of the battery string 600 is kept at a low level, such as less than 20℃ / s, during the process of moving the battery string 600 in the first temperature zone 230, so as to help the battery string 600 keep low temperature (relative to the second temperature zone 240) for a relatively long time, and ensure the uniformity of the solidification of the glue points 630. When the battery string 600 enters the second temperature zone 240, the pre-solidification of the glue points 630 is completed, and the battery string 600 can be quickly heated to the peak temperature in the second temperature zone 240 to complete the welding of the grid lines 611 and the solder strips 620. During the process of heating the battery string 600 in the second temperature zone 240, the flux is activated, and the solvent in the flux volatilizes. When the temperature rises to a higher temperature (such as above 150℃), the organic acid in the flux reacts with the oxides on the solder strips 620 and the grid lines 611 to reduce the oxides and expose clean metal surfaces. Then the temperature continues to rise, and the alloy coating on the surface of the solder strips 620 reaches the eutectic melting point and melts into liquid solder. The molten solder spreads along the grid lines 611 under the action of the flux reducing the surface tension, and fills the micro gaps between the solder strips 620 and the grid lines 611. Some metal atoms of the grid lines 611 dissolve into the liquid solder, and finally a supersaturated solid solution can be formed; and the dissolution rate is controlled by temperature, and the higher the temperature, the faster the dissolution rate. During the welding process, an intermetallic compound layer can be formed at the interface between the grid lines 611 and the solder, which can provide bonding force and form an electrical connection between them. It should be understood that an intermetallic compound layer can also be formed between the copper core of the solder strip 620 and the solder (molten coating) during the welding process. Before the battery piece 610 rises to the peak temperature in the second temperature zone 240, the high-boiling volatile components in the glue points 630 are also completely removed, so that the glue points 630 are completely solidified.

[0068] The peak temperature of the battery string 600 in the second temperature zone 240 can be reasonably selected according to the material properties of the coating, the flux and the grid lines 611. Optionally, the peak temperature of the battery piece 610 in the second temperature zone 240 is 140-240℃; optionally, the peak temperature of the battery string 600 in the second temperature zone 240 is 180-230℃.

[0069] Optionally, from the time when the battery piece 610 enters the second temperature zone 240 to the time when the battery piece 610 reaches the peak temperature, the temperature rising rate can be higher than the temperature rising rate of the battery piece 610 in the first temperature zone 230, such as greater than 20℃ / s. In this way, the process time can be shortened, the process efficiency can be improved, and the damage of the battery piece 610 caused by thermal shock due to long duration of high temperature can be avoided.

[0070] Optionally, the temperature of the third temperature zone 250 at the junction with the second temperature zone 240 is 100-150°C. Optionally, the temperature decreasing rate of the battery piece 610 can be 10-25°C from the time when the temperature of the battery string 600 reaches the peak temperature to the time when the battery string 600 reaches the junction of the second temperature zone 240 and the third temperature zone 250. It can be understood that a faster temperature decreasing rate can improve the process efficiency, but it is easy to cause the stress of the battery piece 610 and the welding position to be unable to be released, affecting the reliability.

[0071] The temperature gradually decreases during the movement of the battery string 600 in the third temperature zone 250. Optionally, the temperature decreasing rate of the battery string 600 in the third temperature zone 250 is kept at a low level, such as no more than 15°C. By setting the third temperature zone 250 with a phased temperature decrease, the battery string 600 can release the internal stress in the third temperature zone 250, reduce the risk of the welding position being disconnected due to stress concentration in the subsequent process or use process, and improve the product reliability.

[0072] In the embodiment, the residence time of the battery string 600 in the first temperature zone 230, the second temperature zone 240 and the third temperature zone 250 is shortened in turn. By setting in this way, the battery piece 610 can be kept in the first temperature zone 230 with a lower temperature for a longer time, so that the glue point 630 has sufficient time to complete the pre-curing, and the uniformity of the internal and external curing is ensured, and the reliability of the finally cured glue point 630 is improved; the temperature of the second temperature zone 240 is relatively high, and the time is relatively shortened, which can improve the process efficiency under the premise of ensuring the completion of welding and complete curing of the glue, and also reduce the negative effects of long time high temperature on the battery piece 610; the third temperature zone 250 is used for releasing the stress of the welding position, and the residence time of the battery piece 610 in the third temperature zone 250 is appropriately shortened under the condition of being able to release the stress, which can improve the process efficiency.

[0073] Optionally, the residence time of the battery string 600 in the first temperature zone 230 is 1-15s, and further, the residence time is 3-15s; the residence time of the battery string 600 in the second temperature zone 240 is 1-8s, and further, the residence time is 2-8s; the residence time of the battery string 600 in the third temperature zone 250 is 1-15s, and further, the residence time is 1-3s. Optionally, the residence time of the battery string 600 in the first temperature zone 230, the second temperature zone 240 and the third temperature zone 250 can be set in proportion, such as in the proportion of (5-12):(3-6):2. Specifically, it can be set in the proportion of 5:3:2, or set in the proportion of 6:3:1.

[0074] In one embodiment, the battery piece 610 stays in the first temperature zone 230 for 6s, in the second temperature zone 240 for 3s, and in the third temperature zone 250 for 1s. It is appreciated that the curing and welding effects of the glue spot 630 are mainly determined by the temperature and the time length. The temperature can be controlled by the heating mechanism 200, while the time length can be determined by the moving speed of the battery string 600 and the length of each temperature zone of the welding thermal field. Alternatively, the battery string 600 moves at a constant speed during the process of passing through the welding thermal field, and in this case, the length ratio of each temperature zone is equal to the time length ratio of the battery piece 610 in each temperature zone. For example, in the embodiment of the present application, the total length of the welding thermal field is 600-2000mm, and the moving speed of the battery string 600 is 50-200mm / s. In one embodiment, the total length of the welding thermal field is 1000mm, and the moving speed of the battery piece 610 is 100mm / s.

[0075] In other alternative embodiments, the conveying mechanism 100 can also be controlled to move the battery string 600 at variable speed, so that the time length of the battery string 600 in each temperature zone can be adjusted by adjusting the moving speed.

[0076] In summary, the embodiment of the present application provides a photovoltaic welding device and a connection method of a cell and a welding strip. The photovoltaic welding device forms a welding space 201, and the photovoltaic welding device comprises a conveying mechanism 100 and a heating mechanism 200. The heating mechanism 200 is used to form a welding heat field in the welding space 201. The welding space 201 has an inlet 202 and an outlet 203. The conveying mechanism 100 is used to drive a cell string 600 to pass through the welding space 201 through the inlet 202 and the outlet 203. Along the conveying direction of the conveying mechanism 100, the welding space 201 comprises a first temperature zone 230, a second temperature zone 240 and a third temperature zone 250 connected in sequence. The unit area heat power of the heating mechanism 200 in the second temperature zone 240 is greater than the unit area heat power of the heating mechanism 200 in the first temperature zone 230 and the second temperature zone 240. Since the unit area heat power of the heating mechanism 200 in the second temperature zone 240 is greater than the unit area heat power of the heating mechanism 200 in the first temperature zone 230 and the second temperature zone 240, the cell string 600 can be at a relatively low temperature in the first temperature zone 230, and the un-solidified glue points 630 of the cell 610 and the welding strip 620 can gradually solidify in the first temperature zone 230. The cell string 600 can rise to a peak temperature in the second temperature zone 240, and can meet the welding requirements, so that the welding strip 620 and the grid line 611 of the cell 610 are welded in the second temperature zone 240, and the glue points 630 can be completely solidified in the second temperature zone 240. The unit area heat power in the third temperature zone 250 is relatively low compared with the second temperature zone 240, so that the temperature of the cell string 600 in the third temperature zone 250 is reduced, and the cell string 600 can release internal stress (especially stress at the welding position) in the third temperature zone, thereby ensuring the reliability of the welding of the cell string 600. It can be seen that the photovoltaic welding device provided by the embodiment of the present application can complete the solidification of the glue points 630 on the cell string 600 and the welding of the welding strip 620 in one welding heat field formed by one device, without completing the solidification of the glue points 630 and the welding of the welding strip 620 in steps, so that the process efficiency is high and the process cost is low.

[0077] The connection method of the cell and the welding strip provided by the embodiment of the present application can be realized by the photovoltaic welding device described above, and has the advantages of high process efficiency and low process cost.

[0078] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any changes or replacements within the technical range disclosed by the present application can be easily thought by those skilled in the art, and should be covered in the protection scope of the present application.

Claims

1. A photovoltaic soldering apparatus for soldering a solder ribbon and a cell tab in a cell string, characterized by, The photovoltaic welding device forms a welding space, and comprises a conveying mechanism and a heating mechanism for forming a welding heat field in the welding space. The welding space has an inlet and an outlet, and the conveying mechanism is used to drive the cell string to pass through the welding space through the inlet and the outlet. The welding space comprises a first temperature zone, a second temperature zone and a third temperature zone connected in sequence along the conveying direction of the conveying mechanism. The unit area heat power of the heating mechanism in the second temperature zone is greater than that in the first temperature zone and the third temperature zone.

2. The photovoltaic welding apparatus of claim 1, wherein, The heating mechanism comprises a top heating assembly and a bottom heating assembly, and the welding space is formed between the top heating assembly and the bottom heating assembly.

3. The photovoltaic welding apparatus of claim 2, wherein, The top heating assembly comprises a plurality of infrared lamp tubes arranged along the conveying direction. The arrangement density of the infrared lamp tubes in the second temperature zone is greater than that in the first temperature zone and the third temperature zone.

4. The photovoltaic welding apparatus of claim 3, wherein, The first temperature zone has a starting section adjacent to the inlet. The arrangement density of the infrared lamp tubes corresponding to the starting section is less than that of the infrared lamp tubes corresponding to other positions in the first temperature zone.

5. The photovoltaic welding apparatus of claim 2, wherein, The bottom heating assembly comprises a plurality of heating rods arranged along the conveying direction.

6. The photovoltaic welding apparatus of claim 2, wherein, The photovoltaic welding device further comprises an exhaust fan for exhausting hot air in the welding space.

7. The photovoltaic welding apparatus of claim 6, wherein, The photovoltaic welding device comprises a plurality of exhaust fans arranged above the top heating assembly. The first temperature zone, the second temperature zone and the third temperature zone are respectively opposite to at least one exhaust fan in the vertical direction.

8. The photovoltaic welding apparatus of claim 2, wherein, The conveying mechanism comprises a conveyor belt and a driving member in transmission connection with the conveyor belt. The conveyor belt is attached to the surface of the bottom heating assembly and is used to carry the cell string.

9. The photovoltaic welding apparatus of claim 1, wherein, The photovoltaic welding device further comprises a temperature detection assembly for detecting the temperature of the first temperature zone, the second temperature zone and the third temperature zone.

10. The photovoltaic welding apparatus of claim 9, wherein, The photovoltaic welding device further comprises a control device. The temperature detection assembly and the heating mechanism are electrically connected to the control device. The control device is used to adjust the power of the heating mechanism according to the information fed back by the temperature detection assembly.

11. The photovoltaic welding apparatus of claim 1, wherein, The lengths of the first temperature zone, the second temperature zone and the third temperature zone in the conveying direction are sequentially shortened.

12. The photovoltaic welding apparatus of claim 11, wherein, The length ratio of the first temperature zone, the second temperature zone and the third temperature zone is (5-12):(3-6):

2.

13. The photovoltaic welding apparatus of claim 1, wherein, The length of the welding space in the conveying direction is 600-2000 mm.

14. A method for connecting a battery cell to a solder strip, characterized in that, The connection method of the cell piece and the solder strip using the photovoltaic welding device of any one of claims 1-13 comprises: connecting the solder strip with the uncured glue point on the cell piece, and making the solder strip contact the grid line on the cell piece; The conveying mechanism is controlled to convey the solder strip and the battery piece through the welding space, so that the glue points gradually solidify in the welding heat field formed by the heating mechanism, and the solder strip and the grid line are welded and connected in the welding heat field.

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