Welding method and photovoltaic module

Abstract

The invention provides a welding method and a photovoltaic module, and relates to the technical field of solar photovoltaic, the method is used for welding a back contact solar cell, the cell comprises a positive electrode and a negative electrode, the positive electrode and the negative electrode comprise a main gate electrode, a fine gate electrode and a bonding pad located on the main gate electrode, the main gate electrode intersects with the fine gate electrode; the method comprises the following steps: printing insulating glue on heterogenous fine gate electrodes at least on the side edges of a positive electrode and a negative electrode in a battery piece, and then printing conductive glue on a bonding pad; the conductive adhesive printing height is greater than or equal to the insulating adhesive printing height; and connecting at least two batteries in series based on the conductive adhesive and the bonding pad to form a battery string. According to the invention, the thin grid lines at the edge of the bonding pad are covered with the printing insulating glue, and the conductive glue is additionally printed on the bonding pad, so that the height difference formed between the conductive wire and the bonding pad due to the existence of the insulating glue is eliminated, and the problem of insufficient soldering of battery welding is solved.

Description

[0001] This patent application is a divisional application of the invention patent application with application number 202211117164.3, application date September 14, 2022, and application name "A welding method and photovoltaic module". Technical Field

[0002] The present application relates to the field of solar photovoltaic technology, and in particular to a welding method and a photovoltaic assembly. Background Art

[0003] Back contact (Interdigitated back contact, IBC) solar cells refer to solar cells with no electrodes on the front of the cell, and the positive and negative electrodes are arranged on the back of the cell. This can reduce the shading of the electrodes to the cell, increase the short-circuit current of the cell, and improve the energy conversion efficiency of the cell.

[0004] The back side of the existing back-contact solar cell adopts multi-busbar electrode technology (MULTI-BUSBAR, MBB) to set the electrodes, that is, the positive electrode located on the back side of the cell includes a positive busbar electrode and a positive fine grid, the negative electrode includes a negative busbar electrode and a negative fine grid, the positive busbar electrode and the negative busbar electrode are arranged in parallel, the positive fine grid and the negative fine grid are arranged in a finger-like cross-shaped manner, and the busbar electrodes and fine grids of the same polarity are interconnected, and the busbar electrodes and fine grids of different polarities are isolated from each other to avoid short circuit.

[0005] When assembling back-contact solar cells to form photovoltaic modules, welding strips are often used to connect adjacent cells. Because the positive and negative fine grid lines on the back of the cell are arranged in an alternating pattern, when using welding strips to connect adjacent cells, it is necessary to use insulating glue to print the fine grid lines on both sides of the main grid electrode to prevent short circuits caused by the connection of opposite-sex grid lines when the welding strips are interconnected.

[0006] However, when the insulating glue is printed on the fine grid line, a certain height will be formed, so that during welding, a height difference will be formed between the welding strip and the welding pad, resulting in abnormal welding and affecting the quality of photovoltaic modules. Summary of the invention

[0007] The present application provides a welding method and a photovoltaic module, which are intended to reduce the problem of cold welding during the welding process of back-contact solar cell sheets and conductive wires and improve welding quality.

[0008] In a first aspect, an embodiment of the present application provides a welding method for welding a back-contact solar cell, wherein the cell comprises a positive electrode and a negative electrode, the positive electrode and the negative electrode comprise a main grid electrode, a fine grid electrode and a pad located on the main grid electrode, and the main grid electrode intersects with the fine grid electrode;

[0009] The method comprises:

[0010] After printing insulating glue at least on the anisotropic fine grid electrodes on the sides of the positive electrode and the negative electrode in the battery cell, printing conductive glue to form at least two solder joints on each of the solder pads; the printing height of the conductive glue is greater than or equal to the printing height of the insulating glue;

[0011] Based on the conductive glue and the pad, at least two batteries are connected in series to form a battery string.

[0012] Optionally, the welding method further comprises:

[0013] Cutting the battery cell after printing the conductive glue into half battery cells;

[0014] Based on the conductive glue and the pad, at least two batteries are connected in series to form a battery string, including:

[0015] Based on the conductive adhesive and the soldering pad, at least two battery halves are serially soldered using a plurality of soldering ribbons to form a battery string.

[0016] Optionally, in the welding method, the negative electrode is a silver electrode, the positive electrode is an aluminum electrode, the positive electrode pad and the negative electrode pad are both silver pads, and an aluminum frame is provided around the pad of the positive electrode;

[0017] In the step of printing the conductive glue on the pad, the size of the conductive glue printed at the positive electrode pad in the battery cell is controlled to be smaller than the size of the conductive glue printed at the negative electrode pad.

[0018] Optionally, in the welding method, when printing insulating glue on the heterogeneous fine grid electrodes on the sides of the positive electrode and the negative electrode in the battery cell, the printing width of the insulating glue is controlled to be larger than the width of the heterogeneous fine grid electrodes, and the printing width of the insulating glue is controlled to cover the heterogeneous fine grid electrodes, and the width is the width along the extension direction of the fine grid electrodes.

[0019] Optionally, before using a plurality of welding ribbons to perform series welding on at least two battery half cells, the welding method further comprises:

[0020] The tin layer on the surface of each soldering strip is thinned, and the thickness of the tin layer of the soldering strip after the thinning treatment is 3 to 10 μm;

[0021] And / or the two ends of the welding strip are flattened, and the flattened length of the welding strip is 1 to 10 mm.

[0022] Optionally, in the welding method, the plurality of welding strips include a first welding strip, a second welding strip and a third welding strip;

[0023] Use multiple welding strips to weld at least two battery halves in series, including:

[0024] Welding one end of the third welding strip to at least one negative electrode pad on the battery half-cell, and welding the other end of the third welding strip to at least one positive electrode pad on the adjacent battery half-cell;

[0025] For the first battery half cell located at the first position of the battery string, one end of the first welding strip is extended and welded to the first bus bar, and the other end of the first welding strip is welded to at least one positive electrode pad on the battery half cell;

[0026] For the second battery half cell located at the end of the battery string, one end of the second welding strip is welded to at least one negative electrode pad on the second battery half cell, and the other end of the second welding strip is extended and welded to the second bus bar.

[0027] Optionally, in the welding method, extending one end of the first welding strip and welding it to the first bus bar includes:

[0028] Applying soldering flux to the first bus bar in advance, and then extending one end of the first soldering strip and soldering it to the first bus bar;

[0029] Extending the other end of the second welding strip and welding it to the second bus bar comprises:

[0030] Soldering flux is applied to the second bus bar in advance, and then the other end of the second welding strip is extended out and welded to the second bus bar.

[0031] Optionally, before using a plurality of welding ribbons to perform serial welding on at least two battery half cells, the method further comprises:

[0032] Black expandable polyethylene is arranged between two adjacent battery halves, between the first battery half-sheet and the first bus bar, and between the second battery half-sheet and the second bus bar.

[0033] In a second aspect, an embodiment of the present application provides a photovoltaic assembly, which is welded by the welding method as described above.

[0034] In an embodiment of the present application, after printing insulating glue on at least the opposite-sex fine grid electrodes on the sides of the positive electrode and the negative electrode in the battery cell, a conductive glue is printed on each pad at the main grid electrode to form at least two welding points, and the printing height of the conductive glue is greater than or equal to the printing height of the insulating glue, and then at least two batteries are welded in series based on the conductive glue and the pad to form a battery string. In the present application, by printing insulating glue to cover the fine grid lines at the edge of the pad, and additionally printing conductive glue at least two welding points on the pad, not only the risk of battery grid breakage and the short circuit of the opposite-sex grid lines when the conductive wires are interconnected are reduced, but also the height difference between the conductive wire and the pad due to the presence of insulating glue is eliminated, and the conductive glue is prevented from being unable to contact the conductive wire due to the offset of the conductive wire, and it is also ensured that after the battery cell is cut in half, there is still enough conductive glue at the pad of each half battery cell to weld with the conductive wire, solving the problem of cold welding of the conductive wire. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0036] Figure 1 A flowchart of a welding method according to an embodiment of the present invention is shown;

[0037] Figure 2 A schematic diagram of the structure of a back contact cell in an embodiment of the present application is shown;

[0038] Figure 3 A schematic diagram of the structure of a photovoltaic module in an embodiment of the present application is shown;

[0039] Figure 4 Shows Figure 3 A partial enlarged view of the middle G part;

[0040] Figure 5 A schematic diagram of printing the conductive adhesive at a first angle in an embodiment of the present application is shown;

[0041] Figure 6 A schematic diagram of the second angle printing of the conductive adhesive in the embodiment of the present application is shown;

[0042] Figure 7 A schematic diagram of the structure of the welding strip after flattening treatment in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0043] The following will be combined with 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 part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0044] Before describing the embodiments of the present application in detail, the application scenarios of the embodiments of the present application are first introduced.

[0045] When the back-contact solar cells are assembled to obtain a photovoltaic module, one end of the conductive wire is connected to a portion of the positive main grid on the back of the cell, and extends along the positive main grid to the negative main grid on the back of the adjacent cell, and the other end of the conductive wire is connected to a portion of the negative main grid, thereby conducting the current collected by the positive main grid and the negative main grid, and connecting two adjacent back-contact solar cells in series. At the same time, in order to prevent the conductive wire from short-circuiting when it is connected to the main grid electrode in the cell and contacting the fine grid electrode of the opposite polarity, it is necessary to provide an insulating layer in the cell except for the position where the main grid electrode is connected to the conductive wire, so that even if the conductive wire connected to the main grid electrode is offset to a certain extent, it will not contact the fine grid electrode of the opposite polarity.

[0046] However, the insulating glue printed on the fine grid line will form a certain height, which makes it difficult to weld during welding. 导电 There will be a height difference between the wire and the pad, which will lead to abnormal welding and affect the quality of photovoltaic modules.

[0047] Based on the above problems, the embodiments of the present application provide a welding method and a photovoltaic module, which aim to reduce the problem of cold solder joints between the back contact solar cell and the conductive wire caused by printing insulating glue on the side of the main grid, and improve the welding quality of the photovoltaic module.

[0048] Reference Figure 1 , Figure 1 A step flow chart of a welding method according to an embodiment of the present application is shown, wherein the method is used for welding a back-contact solar cell, wherein the cell comprises a positive electrode and a negative electrode, wherein the positive electrode and the negative electrode comprise a main grid electrode, a fine grid electrode and a pad located on the main grid electrode, wherein the main grid electrode intersects with the fine grid electrode; the method may comprise steps 101 to 102.

[0049] like Figure 2As shown, the back-contact cell in the embodiment of the present application includes: a semiconductor substrate 10, and a positive electrode 20 and a negative electrode 30 arranged on the backlight surface of the semiconductor substrate 10, the positive electrode 20 may include a positive main grid electrode 21 and a positive fine grid electrode 22, the negative electrode 30 may include a negative main grid electrode 31 and a negative fine grid electrode 32, the positive main grid electrode 21 and the negative main grid electrode 31 are parallel to each other and spaced apart along a first direction A, the positive fine grid electrode 22 and the negative fine grid electrode 32 are parallel to each other and spaced apart along a second direction B, that is, the positive fine grid electrode 22 and the negative fine grid electrode 32 are arranged in a finger-like cross-arrangement, the first direction A and the second direction B are not parallel to each other, and in one case of the embodiment of the present application, the first direction A may be perpendicular to the second direction B.

[0050] At the same time, since the positive fine gate electrode 22 is distributed on the surface of the semiconductor substrate 10, it is used to collect the positively charged carriers generated on the surface of the semiconductor substrate 10, and transfer and converge the collected positively charged carriers to the positive main gate electrode 21, that is, current is formed and converged in the positive fine gate electrode 22 and the positive main gate electrode 21; the negative fine gate electrode 32 is distributed on the surface of the semiconductor substrate 10, and is used to collect the negatively charged carriers generated on the surface of the semiconductor substrate 10, and transfer and converge the collected negatively charged carriers to the negative main gate electrode 31, that is, current is formed and converged in the negative fine gate electrode 32 and the negative main gate electrode 31. Therefore, the positive fine gate electrode 22 is connected to the positive main gate electrode 21 and is spaced apart from the negative main gate electrode 31 by a first preset distance, that is, one end C of the positive fine gate electrode 22 is connected to the positive main gate electrode 21, and the other end D (the second endpoint) is spaced apart from the negative main gate electrode 31 by the first preset distance, thereby achieving disconnection from the negative main gate electrode 31 and avoiding a short circuit; the negative fine gate electrode 32 is connected to the negative main gate electrode 31 and is spaced apart from the positive main gate electrode 21 by a second preset distance, that is, one end E of the negative fine gate electrode 32 is connected to the negative main gate electrode 31, and the other end F (the first endpoint) is spaced apart from the positive main gate electrode 21 by a second preset distance, thereby achieving disconnection from the positive main gate electrode 21 and avoiding a short circuit.

[0051] The first preset distance and the second preset distance may be equal or unequal, and the first preset distance and the second preset distance may be the distances when no short circuit occurs between the main gate electrode and the fine gate electrode with opposite polarity.

[0052] Multiple IBC solar cells can be interconnected by conductive wires to form photovoltaic modules, such as Figure 3 As shown, the current generated and concentrated in multiple solar cells is further concentrated to supply power to external devices.

[0053] Specifically, the positive electrode main grid electrode 21 in the battery cell may include: a plurality of first pads 211 for connecting to the conductive wire, and a positive electrode connection grid line 212 connecting adjacent first pads 211; the negative electrode main grid electrode 31 may include: a plurality of second pads 311 for connecting to the conductive wire, and a negative electrode connection grid line 312 connecting adjacent second pads 311. Accordingly, one end C of the positive electrode fine grid electrode 22 is connected to the first pad 211 or the positive electrode connection grid line 212, and the other end D (second endpoint) is spaced a first preset distance from the second pad 311 or the negative electrode connection grid line 312; one end E of the negative electrode fine grid electrode 32 is connected to the negative electrode connection point 311 or the negative electrode connection grid line 312, and the other end F (first endpoint) is spaced a second preset distance from the positive electrode connection point 211 or the positive electrode connection grid line 212.

[0054] Specifically, when the conductive wire is used to connect adjacent solar cells, the first pad 211 and the second pad 311 can be used as welding points to be welded to the conductive wire, so that the conductive wire extends along the positive main grid electrode 21 and the negative main grid electrode 31 .

[0055] Step 101, after printing insulating glue at least on the anisotropic fine grid electrodes on the sides of the positive electrode and the negative electrode in the battery cell, printing conductive glue on the pad; the conductive glue printing height is greater than or equal to the insulating glue printing height.

[0056] In this step, if Figures 3 to 6 As shown, the main grid electrode includes a positive main grid electrode 21 and a negative main grid electrode 31, and the pad includes the above-mentioned first pad 211 and the second pad 311. After printing the insulating glue 40 on at least part of one side or both sides of the main grid electrode in the battery cell, the conductive glue 50 is printed on the pad on the main grid electrode; wherein the above-mentioned at least part includes the first end point of the opposite polarity fine grid close to the above-mentioned main grid, that is, it can effectively avoid that when the conductive wire 60 is used for series welding with other battery cells in the later stage, even if the conductive wire 60 connected to the main grid electrode is offset to a certain extent, it will not contact the fine grid electrode of the opposite polarity.

[0057] In this step, when a plurality of battery cells are serially soldered using the conductive wire 60, the conductive wire 60 needs to be soldered to a plurality of pads, and the insulating glue 40 printed on the fine grid line will form a certain height, which results in a height difference between the conductive wire 60 and the pad due to the protrusion of the insulating glue 40, resulting in abnormal cold soldering between the conductive wire 60 and the pad, affecting the quality of the photovoltaic module; in the embodiment of the present application, an additional conductive glue 50 is printed at the pad to fill the height difference between the conductive wire 60 and the pad, so that when the pad and the conductive wire 60 are soldered, the soldering is performed based on the conductive glue 50, which can effectively avoid the problem of cold soldering between the conductive wire 60 and the pad.

[0058] In the embodiment of the present application, the back contact solar cell may be specifically of a size of 166 mm, 182 mm or 210 mm in side length, etc. The number of the main grid electrodes may be 6 to 25; the pads may be silver pads, which may be rectangular, circular or elliptical, with a size of 0.5 to 5 mm, and the distance from the pads at the head and tail positions of the main grid electrodes to the edge of the cell is 0 to 10 mm.

[0059] Optionally, the number of the main grid electrodes may be 15, the pads are rectangular with a size of 2*3 mm, and the pads at the head and tail of the main grid electrodes are 3 mm away from the battery cell to prevent the battery cell from cracking.

[0060] In the welding method provided in the embodiment of the present application, in the process of printing the insulating glue 40 on the heterogeneous fine grid electrodes on the sides of the positive electrode and the negative electrode in the battery cell, the printing width of the insulating glue 40 is controlled to be greater than the width of the heterogeneous fine grid electrodes, and the printing width of the insulating glue 40 is controlled to cover the heterogeneous fine grid of the main grid electrode, and the above width is the width along the extension direction of the fine grid electrode. Among them, by covering the fine grid lines at the edge of the pad with the printed insulating glue 40, not only can the main grid electrode be prevented from contacting the fine grid electrode of the opposite polarity when the conductive wire 60 is used for series welding with other battery cells, resulting in a short circuit, but also the risk of battery grid breakage can be effectively reduced.

[0061] Optionally, in the welding method provided in the present application, the printing width of the insulating adhesive 40 is 1.5-10 mm, and the printing height of the insulating adhesive 40 is 10-80 μm. For example, the printing width of the insulating adhesive 40 is controlled to be 4.8 mm, and the printing height of the insulating adhesive 40 is controlled to be 40 μm.

[0062] In the embodiment of the present application, the printed shape of the conductive adhesive 50 can be a cube, an elliptical cylinder or a cylinder.

[0063] Optionally, in the welding method, in the step of printing the conductive glue 50 on the pad at the main gate electrode, the conductive glue 50 is a cube with a length, a width, and a height of 1-2 mm, 1-2 mm, and 0.1-1 mm, respectively.

[0064] Optionally, in an embodiment of the present application, the negative electrode is a silver electrode, the positive electrode is an aluminum electrode, the positive electrode pad and the negative electrode pad are both silver pads, and an aluminum frame is provided on the periphery of the pad of the negative electrode;

[0065] In the step of printing the conductive glue on the pad, the size of the conductive glue printed at the positive electrode pad in the battery cell is controlled to be smaller than the size of the conductive glue printed at the negative electrode pad.

[0066] In the embodiment of the present application, the positive electrode pad (i.e., the first pad 211) and the negative electrode pad (i.e., the second pad 311) of the back-contact solar cell are different in base velvet surface, and an aluminum frame 213 is provided at the first pad; in the step of printing the conductive glue 50 on the pad at the main grid electrode, the size of the conductive glue 50 printed at the first pad 211 in the cell is controlled to be smaller than the size of the conductive glue 50 printed at the second pad 311.

[0067] Among them, because the conductive glue 50 melts during the welding process, the silver in the welding pad connects to the conductive glue 50, and then connects to the conductive wire 60. In this process, the "silver eating" phenomenon will occur, which reduces the height of the conductive glue 50. Therefore, in order to ensure the welding tension, it is necessary to set the size of the conductive glue 50 in the first welding pad 211 to be smaller than the size of the conductive glue 50 in the second welding pad 311 to weaken the "silver eating" phenomenon on the second welding pad, so as to avoid the conductive wire being suspended due to the existence of the aluminum frame after the silver is consumed, and thus unable to fully contact with the conductive glue.

[0068] Optionally, the area of ​​the conductive glue printed at the positive electrode pad is half of the area of ​​the conductive glue printed at the negative electrode pad.

[0069] Optionally, in the welding method, the length, width and height of the conductive glue 50 at the positive electrode pad are 0.5 mm, 0.5 mm and 0.15 mm respectively, and the length, width and height of the conductive glue 50 at the negative electrode pad are 1 mm, 1 mm and 0.15 mm respectively.

[0070] Considering that the welding quality at the head and tail positions is more critical when the conductive wire 60 is used for series connection, and that the battery cell needs to be cut into two halves along the middle position of the vertical main grid electrode later, so that the middle position of the main grid electrode becomes the head and tail position of the new conductive wire 60 series welding, in the step of printing the conductive glue 50 on the pad at the main grid electrode, the conductive glue 50 is printed on the pad at the head and tail positions and the middle position of the main grid electrode to form double welding points, so as to avoid the conductive glue 50 being unable to contact the conductive wire 60 due to the deviation of the conductive wire 60, thereby causing a cold solder joint. The printing effect of the conductive glue 50 is as follows: Figure 3 As shown, the conductive glue 50 of a single solder joint is printed on the other pads except the first and last positions and the middle position of the main gate electrode, so as to save the amount of the conductive glue 50.

[0071] Optionally, in one implementation, in the step of printing the conductive paste on the pads, the conductive paste is printed on each pad to form a double solder joint.

[0072] In this embodiment, by printing conductive glue to form double welding points at each pad, not only can the conductive glue 50 be prevented from being unable to contact the conductive wire 60 due to the offset of the conductive wire 60, thereby preventing a cold solder joint, but it also ensures that after the battery cell is cut in half, there is still enough conductive glue and conductive wire at the pad of each half battery cell for welding.

[0073] Optionally, the pads at the beginning and end and the middle of the main gate electrode are wider than the pads at other positions, that is, the beginning and end and the middle of the main gate electrode are widened to better print the conductive glue 50 for forming double solder joints. Optionally, the size of the widened pad is 4*3mm.

[0074] Step 102: Based on the conductive adhesive and the pad, at least two batteries are connected in series to form a battery string.

[0075] In this step, the conductive glue 50 melts during the welding process, so that the silver in the pad is connected to the conductive glue 50, and the conductive glue 50 is connected to the pad, thereby realizing the welding of the pad and the conductive wire 60 to obtain the above-mentioned battery string, and then through the lamination process, multiple battery strings are welded through the bus bar to obtain a photovoltaic module. In this step, because of the presence of the conductive glue 50, the use of flux can be omitted.

[0076] The welding method provided in the embodiment of the present application is used for welding back-contact solar cell sheets, after printing insulating glue on at least the heterogeneous fine grid electrodes on the sides of the positive electrode and the negative electrode in the cell sheet, printing conductive glue on the pad at the main grid electrode, and the printing height of the conductive glue is greater than or equal to the printing height of the insulating glue, and then based on the conductive glue and the pad, at least two cells are welded in series to form a battery string. In the present application, by printing insulating glue to cover the thin grid lines at the edge of the pad, and additionally printing conductive glue on the pad, not only the risk of battery grid breakage and the short circuit of heterogeneous grid lines when the conductive wires are interconnected are reduced, but also the height difference between the conductive wire and the pad due to the presence of the insulating glue is eliminated, solving the problem of cold solder joints in the conductive wire welding.

[0077] The welding method provided in the embodiment of the present application further includes step 103 before the above step 102 , and the above step 102 specifically includes step 1021 .

[0078] Step 103, cutting the battery cell after printing the conductive glue into half battery cells.

[0079] In this step, the cell is cut into two halves along the middle of the vertical main grid, namely the above-mentioned half cell. The top corners of the cell located on both sides of the main grid electrode are chamfered so that after the cell is cut into half, the other half of the cell does not need to be rotated 180°, and the cut edge of the cell can be interconnected with the other cut edge welding strip 61, and the chamfered edge can be interconnected with the other chamfered edge welding strip 61 of the cell.

[0080] Step 1021: Based on the conductive adhesive and the soldering pad, at least two battery halves are serially soldered using a plurality of soldering ribbons to form a battery string.

[0081] The conductive wire 60 may be a welding strip 61 , which may be a conventional flat welding strip, a round welding strip or a triangular welding strip, and may be a flat welding strip, so as to better contact the conductive adhesive 50 and the pad and improve the welding strength.

[0082] Optionally, in one embodiment, the plurality of welding strips include a first welding strip, a second welding strip and a third welding strip;

[0083] The above step 102 includes steps 201 to 203:

[0084] Step 201, welding one end of the third welding ribbon to at least one negative electrode pad on a battery half-cell, and welding the other end of the third welding ribbon to at least one positive electrode pad on an adjacent battery half-cell;

[0085] Step 202: for the first battery half cell located at the first position of the battery string, one end of the first welding ribbon is extended and welded to the first bus bar, and the other end of the first welding ribbon is welded to at least one positive electrode pad on the battery half cell;

[0086] Step 203: For the second battery half cell located at the end of the battery string, one end of the second welding strip is welded to at least one negative electrode pad on the second battery half cell, and the other end of the second welding strip is extended and welded to the second bus bar.

[0087] In this embodiment, one end of the welding strip 61 is connected to a portion of the positive main grid electrode on the back of the battery half-cell, and extends along the positive main grid electrode 21 to the negative main grid on the back of the adjacent battery half-cell, and the other end of the welding strip is connected to a portion of the negative main grid electrode, thereby conducting the current collected by the positive main grid electrode 21 and the negative main grid electrode 31, and connecting two adjacent back-contact solar cells in series;

[0088] At the same time, in order to assemble a photovoltaic module, it is necessary to use a bus bar 70 to connect multiple battery strings. Therefore, the positive main grid electrode 21 of the first battery half and the first bus bar are respectively welded to the two ends of the welding strip, and the negative main grid electrode 31 of the last battery half and the second bus bar are respectively welded to the two ends of the welding strip, so as to realize the connection and conduction of multiple battery strings, and then assemble a photovoltaic module.

[0089] Optionally, in a specific implementation manner, the welding method provided in the embodiment of the present application further includes step 104 before the above step 1021:

[0090] Step 104, reducing the thickness of the tin layer on the surface of each soldering strip.

[0091] In this specific implementation, because the pads are printed with conductive glue 50, the conductive glue 50 will melt during the welding process, making it firmly connected to the pads and the welding strips. Therefore, there is no need to consider the welding effect of the tin layer of the welding strip itself, so the thickness of the tin layer on the surface of the welding strip 61 can be thinned, which can not only save the cost of the welding strip 61, but also reduce the risk of broken grid when the silver grid line is in a state without insulating glue 40.

[0092] Optionally, after the thinning process, the thickness of the tin layer of the soldering strip 61 is 3-10 μm, for example, 5 μm.

[0093] Optionally, in a specific implementation method, extending one end of the first welding strip and welding it to the first bus bar includes:

[0094] Applying soldering flux to the first bus bar in advance, and then extending one end of the first soldering strip and soldering it to the first bus bar;

[0095] Extending the other end of the second welding strip and welding it to the second bus bar comprises:

[0096] Soldering flux is applied to the second bus bar in advance, and then the other end of the second welding strip is extended out and welded to the second bus bar.

[0097] In this specific embodiment, because the thickness of the tin layer on the surface of the welding strip 61 is thinned, and there is no conductive glue 50 at the bus bar, in order to ensure the welding effect between the welding strip 61 and the bus bar, flux is pre-applied to the first bus bar connected to the first battery half-cell at the first position and the second bus bar connected to the second battery half-cell at the last position, and then welded to the welding strip 61 extending from the positive main grid electrode direction of the first battery half-cell, or welded to the welding strip 61 extending from the negative main grid electrode direction of the second battery half-cell, so as to respectively connect the positive electrode of the first battery half-cell to the first bus bar and the negative electrode of the second battery half-cell to the second bus bar.

[0098] Optionally, in one embodiment, the welding method provided in the embodiment of the present application, before using a plurality of welding ribbons to perform series welding on at least two battery half cells, further comprises:

[0099] Step 105: Flatten the two ends of the welding strip.

[0100] In this embodiment, the two ends of the cut solder strip 61 are flattened to prevent the solder strip 61 from piercing the insulating glue 40, causing the opposite electrode grid lines to cause welding short circuits. At the same time, the flattened solder strip 61 can increase the welding area and improve the welding yield. Figure 7 shown.

[0101] Optionally, the flattened length of the welding strip 61 is 1-10 mm, for example, 3 mm.

[0102] Optionally, in one embodiment, the welding method provided in the embodiment of the present application, before using a plurality of welding ribbons to perform series welding on at least two battery half cells, further comprises:

[0103] Step 106: Dispose black expandable polyethylene between two adjacent battery halves, between the first battery half and the first bus bar, and between the second battery half and the second bus bar.

[0104] In this embodiment, black expandable polyethylene 80 is provided between two adjacent battery halves that need to be serially welded, between the first battery half-cell and the first bus bar, and between the last battery half-cell and the second bus bar, thereby filling the gaps, shielding all welding strips 61 for subsequent serial welding, protecting the welding strips 61, and making the overall structure more beautiful.

[0105] The black expandable polyethylene 80 may be a small strip of high temperature resistant black expandable polyethylene tape.

[0106] The width of the black expandable polyethylene 80 is determined according to the actual gap between the battery halves. Optionally, the width of the black expandable polyethylene 80 between the battery strings is greater than the width between the battery halves.

[0107] An embodiment of the present application also provides a photovoltaic module, which is prepared by the welding method as described above.

[0108] Among them, in the process of welding and preparing the above photovoltaic modules, not only the insulating glue is printed on both sides of the main grid of the battery cell, but also the conductive glue is printed on the pad. The printing height of the conductive glue is greater than or equal to the printing height of the insulating glue, eliminating the height difference between the welding strip and the pad, solving the abnormal welding of the conductive wire, and the printed insulating glue covers the fine grid line at the edge of the pad, which can effectively reduce the risk of the battery grid breaking. Therefore, the photovoltaic module provided by the embodiment of the present application has good welding effect, high yield, and firm grid line, so it is stable and durable.

[0109] It should be noted that, for the method embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the embodiments of the present application are not limited by the described order of actions, because according to the embodiments of the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions involved are not necessarily required by the embodiments of the present application.

[0110] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0111] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for a terminal (which can be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to execute the methods described in each embodiment of the present application.

[0112] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

Claims

1. A welding method, characterized in that: Used for welding a back contact solar cell, the cell comprises a positive electrode and a negative electrode, the positive electrode and the negative electrode comprise a main grid electrode, a fine grid electrode and a welding pad located on the main grid electrode, the main grid electrode intersects with the fine grid electrode; The method comprises: After printing insulating glue at least on the anisotropic fine grid electrodes on the sides of the positive electrode and the negative electrode in the battery cell, printing conductive glue to form at least two solder joints on each of the solder pads; the printing height of the conductive glue is greater than or equal to the printing height of the insulating glue; Based on the conductive glue and the pad, at least two batteries are connected in series to form a battery string.

2. The welding method according to claim 1, characterized in that: The method further comprises: Cutting the battery cell after printing the conductive glue into half battery cells; Based on the conductive glue and the pad, at least two batteries are connected in series to form a battery string, including: Based on the conductive adhesive and the soldering pad, at least two battery halves are serially soldered using a plurality of soldering ribbons to form a battery string.

3. The welding method according to claim 1, characterized in that: The negative electrode is a silver electrode, the positive electrode is an aluminum electrode, the positive electrode pad and the negative electrode pad are both silver pads, and an aluminum frame is provided around the pad of the positive electrode; In the step of printing the conductive glue on the pad, the size of the conductive glue printed at the positive electrode pad in the battery cell is controlled to be smaller than the size of the conductive glue printed at the negative electrode pad.

4. The welding method according to claim 1, characterized in that: When printing insulating glue on the heterogeneous fine grid electrodes on the sides of the positive electrode and the negative electrode in the battery cell, the printing width of the insulating glue is controlled to be larger than the width of the heterogeneous fine grid electrodes, and the printing width of the insulating glue is controlled to cover the heterogeneous fine grid electrodes, and the width is the width along the extension direction of the fine grid electrodes.

5. The welding method according to claim 2, characterized in that: Before using a plurality of welding ribbons to string together at least two battery halves, the method further includes: The tin layer thickness on the surface of each soldering strip is thinned, and the tin layer thickness of the soldering strip after the thinning treatment is 3 to 10 μm; and / or, the two ends of the soldering strip are flattened, and the flattened length of the soldering strip is 1 to 10 mm.

6. The welding method according to claim 2, characterized in that: The plurality of welding strips include a first welding strip, a second welding strip and a third welding strip; Use multiple welding strips to weld at least two battery halves in series, including: Welding one end of the third welding strip to at least one negative electrode pad on the battery half-cell, and welding the other end of the third welding strip to at least one positive electrode pad on the adjacent battery half-cell; For the first battery half cell located at the first position of the battery string, one end of the first welding strip is extended and welded to the first bus bar, and the other end of the first welding strip is welded to at least one positive electrode pad on the battery half cell; For the second battery half cell located at the end of the battery string, one end of the second welding strip is welded to at least one negative electrode pad on the second battery half cell, and the other end of the second welding strip is extended and welded to the second bus bar.

7. The welding method according to claim 6, characterized in that: Extending one end of the first welding strip and welding it to the first bus bar comprises: Applying soldering flux to the first bus bar in advance, and then extending one end of the first soldering strip and soldering it to the first bus bar; Extending the other end of the second welding strip and welding it to the second bus bar comprises: Soldering flux is applied to the second bus bar in advance, and then the other end of the second welding strip is extended out and welded to the second bus bar.

8. The welding method according to claim 6, characterized in that: Before using a plurality of welding ribbons to perform series welding on at least two battery half-cells, the method further includes: Black expandable polyethylene is arranged between two adjacent battery halves, between the first battery half-sheet and the first bus bar, and between the second battery half-sheet and the second bus bar.

9. A photovoltaic module, characterized in that: The method is welded by the welding method according to any one of claims 1 to 8.

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