Photovoltaic module and method for manufacturing the same

Abstract

To improve reliability of an electric connection of a junction box in a photovoltaic module, and improve an efficiency of when conducting a photo-generated current of the photovoltaic module.SOLUTION: A photovoltaic power laminate forms at least one cell string through connection of a plurality of battery cells via a welding strip, and the cell string is provided laminated on a back plate. The welding strip is connected to a bus bar, and the junction box is positioned on a side separated from each battery cell, of the back plate, and fixedly connected to the back plate, and the junction box is provided with pads. Therein, the bus bar is in contact with the pad through an opening provided in the back plate, the bus bar and the pad are laser-welded to be connected with each other. When an area of a region where the bus bar and the pad are contacted is define to be a first area, and an area of a region where the bus bar and the pad are welded is defined to be a second area, the second area is 30% to 60% of the first area.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The embodiments of the present application relate to the field of photovoltaic new energy, and in particular to a photovoltaic module and a method for manufacturing a photovoltaic module. [Background technology]

[0002] With the development of science and technology, photovoltaic technology is also developing rapidly. Among them, photovoltaic technology refers to a technology that can directly convert the light energy of the sun into electrical energy. In particular, when implementing photovoltaic technology, the light receiving surface of the photovoltaic laminate receives the light irradiated from the sun, the light energy of the sun is converted into electrical energy by the cell string of the photovoltaic laminate, and the converted electrical energy is transported from the cell string of the photovoltaic laminate to the junction box by the bus bar of the photovoltaic laminate, and the electrical power is extracted by the junction box for user use.

[0003] Before the bus bar of the photovoltaic stack transports the electric energy converted from the cell strings of the photovoltaic stack to the junction box, the bus bar of the photovoltaic stack and the pad of the junction box need to be fixed to each other and electrically connected. However, in the conventional technology, after the bus bar of the photovoltaic stack and the pad of the junction box are fixed to each other and electrically connected, the reliability of the electrical connection between the bus bar and the pad is poor, resulting in poor stability and low efficiency when deriving the photocurrent of the photovoltaic stack. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention aims to provide a photovoltaic module for improving the reliability of the electrical connection of a junction box in a photovoltaic module and improving the efficiency in deriving the photocurrent of the photovoltaic module. [Means for solving the problem]

[0005] In order to solve the above problem, an embodiment of the present invention provides a solar cell, comprising: a photovoltaic stack; and a junction box; the photovoltaic stack comprises a plurality of battery cells, at least one welding strip, a back plate, and a bus bar; the plurality of battery cells are connected via the welding strips to form at least one cell string; the at least one cell string is stacked on the back plate; the welding strip is connected to the bus bar; the junction box is located on a side of the back plate away from the battery cells and fixedly connected to the back plate; and the junction box is fixed to the back plate. a pad is provided on a back plate, wherein the bus bar passes through an opening provided in the back plate and abuts against the pad, the bus bar and the pad are connected to each other by laser welding, and a plurality of weld seams are formed in the welded area, wherein the welded area refers to an area where laser welding is performed between the bus bar and the pad, and the bus bar and the pad are formed as an integral structure by the plurality of weld seams, wherein each weld seam extends from the bus bar toward the inside of the pad, and the extension depth of each weld seam in the pad is 80% or less of the thickness of the pad.

[0006] The present embodiment further provides a method for manufacturing a photovoltaic module, comprising: providing a photovoltaic stack, the photovoltaic stack including a plurality of battery cells, at least one welding strip, a back plate, and a bus bar, wherein a plurality of the battery cells are connected to each other via the welding strips to form at least one cell string, the at least one cell string being stacked on the back plate, and the welding strip being connected to the bus bar; and providing a junction box, the junction box being disposed on a side of the back plate away from the battery cells, and the back plate being disposed on the side of the back plate away from the battery cells. and providing pads within the junction box; passing the busbar through an opening in the back plate and abutting the pad; and laser welding the busbar and the pad to connect them to each other, wherein a plurality of weld seams are formed in a welded area, the welded area referring to an area where laser welding is performed between the busbar and the pad, the busbar and the pad being formed as an integral structure by the plurality of weld seams, and an extension depth of each of the weld seams within the pad is no more than 80% of a thickness of the pad. Effect of the Invention

[0007] The photovoltaic module provided by the embodiments of the present application can improve the efficiency in drawing out the photocurrent of the photovoltaic module. [Brief description of the drawings]

[0008] One or more embodiments are illustratively illustrated in corresponding figures in the accompanying drawings, but these illustrative illustrations are not intended to be limiting of the embodiments, and parts having the same or similar reference numbers in the accompanying drawings represent the same or similar parts, and unless otherwise stated, the figures in the accompanying drawings do not form a proportional limitation. [Figure 1] FIG. 1 is a cross-sectional view of a photovoltaic module provided according to some embodiments of the present application. [Diagram 2] FIG. 2 is a plan view of a photovoltaic module provided by some embodiments of the present application. [Diagram 3] FIG. 3 is a plan view of a photovoltaic module provided by some embodiments of the present application. [Figure 4] FIG. 4 is a plan view of a photovoltaic module provided by some embodiments of the present application. [Diagram 5] FIG. 5 is a plan view of a photovoltaic module provided by some embodiments of the present application. [Figure 6] FIG. 6 is a diagram illustrating a connection structure between bus bars and pads in a junction box in a photovoltaic module provided according to some embodiments of the present application. [Figure 7] FIG. 7 is a cross-sectional view of a connection structure between a bus bar and a pad in a junction box in a photovoltaic module provided according to some embodiments of the present application. [Figure 8] FIG. 8 is a diagram illustrating a structure of a junction box provided by some embodiments of the present application. [Figure 9] FIG. 9 is a diagram illustrating a combined junction box and subar structure provided by some embodiments of the present application. [Figure 10] FIG. 10 is a diagram illustrating a structure of a junction box provided by some embodiments of the present application. [Figure 11] FIG. 11 is a flow chart of a manufacturing process for a photovoltaic module provided according to some embodiments of the present application. [Figure 12] FIG. 12 is a flow chart of the steps for manufacturing a laminate provided by some embodiments of the present application. [Figure 13] FIG. 13 is a flow chart of steps for visually detecting the relative positions of bus bars and a junction box provided by some embodiments of the present application. [Figure 14]FIG. 14 is a flow chart of steps for positioning and taking pictures of a junction box provided by some embodiments of the present application. [Figure 15] FIG. 15 is a flow chart of steps for positioning and photographing busbars provided by some embodiments of the present application. [Figure 16] FIG. 16 is a diagram showing an image of a laminate before welding provided by some embodiments of the present application. [Figure 17] FIG. 17 is a diagram showing a photograph of the position of the diode before welding provided by some embodiments of the present application. [Figure 18] FIG. 18 is a diagram illustrating a photograph of the position of a busbar before welding provided by some embodiments of the present application. [Figure 19] FIG. 19 is a diagram showing a photograph of the position of a busbar after welding provided by some embodiments of the present application. [Figure 20] FIG. 20 is a diagram showing the structure of a photovoltaic module manufacturing apparatus provided by some embodiments of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In the prior art, when manufacturing a photovoltaic module, the busbar and the pads in the junction box are fixed by thermocompression bonding. The pads are parts that provide a fixed position for the busbar in the junction box. That is, in the connection structure between the busbar and the junction box of the photovoltaic module, the space between the busbar and the pad is filled with metal tin, which is derived from the tin paste in the thermocompression bonding. The space between the busbar and the pads in the junction box is fixed with metal tin. Since the metal material of the busbar and the pad is significantly different from metal tin, the interface connection strength formed during the connection process is easily affected by changes in external conditions. For example, during the actual operation of the photovoltaic module, the environmental cold and hot conditions change drastically, so the connection interface formed between the busbar and the pad via the metal tin is easily peeled off depending on the degree of expansion, and unsoldering occurs. At the same time, during the soldering process, the spreading direction of the tin paste after melting is affected by the surface flatness of the busbar and the pad, so the phenomenon of cold solder connection is likely to occur. In addition, the tin layer of the thermocompression bonding has metallic tin distributed around the busbar and pad in addition to the metallic tin located between the busbar and pad. The above phenomenon affects the connection reliability of the photovoltaic module of the junction box, leading to poor stability and low efficiency when deriving the photocurrent of the photovoltaic stack.

[0010] In response to this, the inventor of the present application has designed a photovoltaic module including a photovoltaic stack and a junction box. The photovoltaic stack includes a plurality of battery cells, at least one welding strip, a back plate, and a bus bar, and the plurality of battery cells are connected via the welding strip to form at least one cell string, and the at least one cell string is stacked on the back plate, and the welding strip is connected to the bus bar. The junction box is located on the side of the back plate away from the battery cells, and is fixedly connected to the back plate, and a pad is provided on the junction box. Here, the bus bar passes through an opening provided in the back plate and abuts against the pad, and the bus bar and the pad are connected to each other by laser welding. The welded area includes a plurality of weld seams, the welded area being the area where laser welding is performed between the busbar and the pad, and the busbar and the pad are formed as an integral structure by the plurality of weld seams, each of the weld seams extending from the busbar toward the inside of the pad, and the extension depth of each of the weld seams within the pad is 80% or less of the thickness of the pad.

[0011] In use, the photovoltaic module of the present application receives light irradiated from the sun on the light-receiving surface of the photovoltaic stack, whereby the cell strings of the photovoltaic stack convert the light energy emitted from the sun into electrical energy, and then transmit the electrical energy to the busbars via the welding strips, and then transmit the received electrical energy to the junction box via the busbars. Through the connection action of the busbars, the cell strings in the photovoltaic module are connected together with the junction box to an external circuit, and electrical energy is delivered for use by users.

[0012] In the photovoltaic module of the present application, a weld seam is formed between the busbar in the photovoltaic module and the pad in the junction box by laser welding, the weld seam penetrating the busbar and extending into the pad. The metal materials of the busbar and the pad located at the weld seam are integrated. As a result, a strong connection structure is formed between the busbar and the pad in the junction box by laser welding. The metal materials of the busbar and the pad are melted together by the action of the laser, and there is no need to connect them with metal tin. As a result, an integrated structure with high connection strength is formed at the connection interface between the busbar and the pad in the junction box. In particular, when both the busbar and the pad in the junction box use copper in an actual situation, the connection reliability between the two can be further ensured by fusing the same type of metal. In addition, in the laser welding, a thin tin layer may be provided around the busbar and the pad, and such a tin layer can play a role in preventing oxidation of the copper metal on the surface of the busbar or the surface of the pad. This makes it possible to avoid the phenomenon of cold solder connection that is likely to occur when soldering is used in the electrical connection between the busbar and the pad as in conventional technology, and also to avoid the same on-off phenomenon that is likely to occur when soldering is used in conventional technology, thereby improving the stability and efficiency when deriving the photocurrent of the photovoltaic stack.

[0013] In the process of installing the junction box, the photovoltaic module is obtained by first forming a photovoltaic laminate, and then stacking the sealing adhesive film and the protective plate on the front and back of the cell string group, respectively. After the photovoltaic laminate is obtained, the junction box is fixed on the surface of the photovoltaic laminate, and a part of the bus bar connected to the cell string is inserted into the junction box. The junction box is provided with a circuit structure formed by a diode and a cable, and the diode mainly plays the role of protecting the cell string group from abnormalities, and the cable can realize the electrical connection with the external electrical control device.

[0014] Usually, the junction box is provided on the back surface of the photovoltaic stack, that is, on the surface of the protective plate on the back surface of the cell string group in the photovoltaic stack. The photovoltaic stack may be provided with one or more junction boxes, for example, the number of junction boxes provided in the photovoltaic stack may be 2 to 6, preferably 3. The junction box may be located on the back surface of the photovoltaic stack, and may be located on the edge of the photovoltaic stack or on the inside close to the center of the photovoltaic stack. When the junction box is provided on the inside close to the center of the photovoltaic stack, it is preferably provided on the center line of the photovoltaic stack, more preferably on the center line of the long side of the photovoltaic stack. At least one diode is provided inside each junction box provided in the photovoltaic stack, and the electrical connection between at least one diode and a bus bar in one photovoltaic module is realized by the technical means of the present invention.

[0015] In order to clarify the objectives, technical solutions and advantages of the embodiments of the present application, the following detailed description of each embodiment of the present application will be given with reference to the drawings. However, those skilled in the art will understand that although many technical details are proposed in each embodiment of the present application to allow readers to better understand the present application, the technical solutions claimed for protection by the present application can also be realized through various changes and modifications based on the following embodiments.

[0016] As shown in Figs. 1 to 7, a photovoltaic module provided by some embodiments of the present application includes a photovoltaic stack 100 and a junction box 200. The photovoltaic stack 100 includes a plurality of battery cells 110, at least one welding strip 120, a back plate 130, and a bus bar 140. The plurality of battery cells 110 are connected by the welding strip 120 to form at least one cell string 150, and the cell string 150 is stacked with the back plate 130, and the welding strip 120 is connected to the bus bar 140. The junction box 200 is located on the side of the back plate 130 away from the battery cells 110 and is fixed to the back plate 130, and the junction box 200 is provided with a pad 210. Among them, the busbar 140 penetrates an opening in the backplate 130 and abuts against the pad 210, the busbar 140 and the pad 210 are connected to each other by laser welding, and a plurality of weld seams 310 are formed in the welded area, where the welded area refers to the area where the laser welding is performed between the busbar 140 and the pad 210, and the busbar 140 and the pad 210 are formed as an integral structure by the plurality of weld seams 310, where each weld seam 310 extends from the busbar 140 toward the inside of the pad 210, and the extension depth of each weld seam 310 in the pad 210 is 80% or less of the thickness of the pad 210.

[0017] The photovoltaic stack 100 in the present application may further include other components, but is not limited thereto in the present application. In one example, the photovoltaic stack 100 further includes an adhesive film (not shown) located between the cell string 150 and the back plate 130. In another example, the photovoltaic stack 100 includes a front plate (not shown) located on the side of the cell string 150 away from the back plate 130, and in this case, an adhesive film (not shown) may be provided between the front plate and the cell string 150.

[0018] As shown in Figures 2 and 3, multiple weld seams 310 are formed in the area between busbar 140 and pad 210 where welding occurs. In this manner, the weld pattern for fixing the weld between busbar 140 and pad 210 is distributed in a dispersed manner over a portion of the surfaces of busbar 140 and pad 210 where they abut against each other, thereby increasing the stability of busbar 140 and pad 210 after welding.

[0019] As shown in Figures 6 and 7, each weld seam 310 extends from the surface of the busbar 140 away from the pad 210 toward the inside of the pad 210, the busbar 140 is formed as a unitary structure with the pad 210 by laser welding at the weld seam 310, and the extension depth of the weld seam 310 within the pad 210 is less than 80% of the thickness of the pad 210.

[0020] The weld seam 310 on the bus bar 140 is formed by laser irradiation, and the weld seam 310 penetrates the bus bar 140 and extends into the inside of the pad 210. The extension depth of the weld seam 310 in the pad 210 is 80% or less (greater than 0 and 80% or less) of the thickness of the pad 210, for example, in an actual situation, the extension depth of the weld seam 310 in the pad 210 may be 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, 5% or 3% of the thickness of the pad 210, and is preferably 15% to 45%.

[0021] It should be noted that the extension depth of the weld seam 310 in the pad 210 is correlated with the laser power and the laser irradiation time. In practical situations, with the increase of the laser power and / or the extension of the laser irradiation time, the extension depth of the weld seam 310 in the pad 210 also increases. If the extension depth of the weld seam 310 in the pad 210 is too large, the laser will melt through the pad 210 and touch the bottom of the junction box 200. If the extension depth of the weld seam 310 in the pad 210 is too small, poor contact will occur between the bus bar 140 and the pad 210. Table 1 below effectively describes the ratio of the extension depth of the weld seam 310 in the pad 210 to the thickness of the pad 210 listed above based on the product defect rate that appears when the junction box is installed on the photovoltaic module.

[0022] Table 1: Product defect rate of photovoltaic module 10 under different extension depth ratios of weld seam 310 (the extension depth ratios in the table are divided into two types, the extension depth ratios in Comparative Example 1 and Comparative Example 2 indicate the ratio of the extension depth of weld seam 310 at busbar 140 to the thickness of busbar 140, the extension depth ratios in Comparative Example 3, Comparative Example 4 and Examples 1 to 7 indicate the ratio of the extension depth of weld seam 310 at pad 210 to the thickness of pad 210, the product defect rate indicates the rate of defective products when junction box 200 is installed on photovoltaic module 10, the contact failure rate indicates the rate of products in which contact failure between busbar 140 and pad 160 occurs when junction box 200 is installed on photovoltaic module 10, and the pad melt-through rate indicates the rate of products in which pad melt-through occurs when junction box 200 is installed on photovoltaic module 10).

[0023] Table 1 TIFF0007671271000001.tif135161

[0024] As can be seen from Table 1, when the weld seam 310 is formed only in the bus bar 140 (as shown in Comparative Example 1 and Comparative Example 2), the product yield of the photovoltaic module 10 is low. When the extension depth of the weld seam 310 in the pad 210 exceeds 80% of the thickness of the pad 210 (as shown in Comparative Example 3 and Comparative Example 4), the product defect rate of the photovoltaic module 10 is high. When the extension depth of the weld seam 310 in the pad 210 accounts for 15% to 45% of the thickness of the pad 210 (as shown in Examples 3 to 6), the product yield of the photovoltaic module 10 is high, that is, the percentage of products in which the contact failure phenomenon between the bus bar 140 and the pad 210 occurs when the junction box 200 is installed in the photovoltaic module 10 is low, and at the same time, the percentage of products in which the melt-through phenomenon of the pad 210 occurs is low.

[0025] Furthermore, the weld seam 310 may be formed by continuous laser irradiation or pulsed laser irradiation, and a linear weld seam 310 is formed along the laser irradiation path on the surface of the busbar 140. Among these, the weld seam 310 formed by continuous laser irradiation is not obviously divided along the laser irradiation path, while the weld seam 310 formed by pulsed laser irradiation appears as dots regularly arranged along the laser irradiation path.

[0026] In the photovoltaic module 10 according to some embodiments of the present application, a weld seam 310 is formed between the bus bar 140 and the pad 210 in the junction box 200 by laser welding, so that the bus bar 140 and the pad 210 located at the weld seam 310 are formed as an integral structure, and the extension depth of the weld seam 310 in the pad 210 is 80% or less of the thickness of the pad 210. In this way, the metal material of the bus bar 140 and the metal material of the pad 210 are integrated under the action of a laser, and there is no need to connect them with metal tin. This forms an integral structure with high connection strength at the connection interface between the bus bar 140 and the pad 210 in the junction box 200, avoiding the problem that the connection interface between the bus bar 140 and the pad 210 is filled with metal tin and is easily affected by external conditions, and ensures the connection reliability of the photovoltaic module 10 in the junction box 200.

[0027] 7 is a diagram showing a cross-sectional structure of the bus bar 140 and the pad 210 after laser welding in the junction box 200 according to some embodiments of the present application. As can be seen from FIG. 7, there is no obvious tin storage groove structure in the pad 210 according to some embodiments of the present application.

[0028] As shown in Figures 6 and 7, in some embodiments of the present application, pad 210 includes a welded area 2101 that is bonded to busbar 140, and a surface of pad 210 facing busbar 140 and a recessed area 2102 located within welded area 2101, where recessed area 2102 surrounds weld seam 310, and there is a gap between the surface of pad 210 located in recessed area 2102 and the surface of busbar 140 facing pad 210.

[0029] By forming the recessed area 2102 in the welding area 2101 of the pad 210, a filling space can be provided for the molten metal material of the busbar 140, and the range of the integrated connection area between the busbar 140 and the pad 210 can be expanded, thereby further increasing the connection strength between the busbar 140 and the pad 210. At the same time, a space can be provided for slag generated during welding, which can prevent the slag from filling the connection interface between the metal materials of the busbar 140 and the pad 210 and affecting the weld strength between them.

[0030] As shown in FIG. 7 , in some embodiments of the present application, the weld seam 310 includes a first segment 314 located within the busbar 140 and a second segment 315 located within the pad 210, where the first segment 314 and the second segment 315 meet at the bonding interface between the busbar 140 and the pad 210.

[0031] A first segment 314 of the weld seam 310 is located inside the busbar 140 and penetrates the entire busbar 140 in the thickness direction. A second segment 315 of the weld seam 310 extends from the surface of the pad 210 facing the busbar 140 into the pad 210 and is joined to the first segment of the weld seam 310 at the interface where the busbar 140 and the pad 210 are joined.

[0032] In some embodiments of the present application, the width of the first segment 314 in the direction from the bus bar 140 to the pad 210 is fixed, or the width of the first segment 314 in the direction from the bus bar 140 to the pad 210 gradually decreases.

[0033] That is, the width of the first segment 314 of the weld seam 310 may remain constant anywhere within the busbar 140 , or may exhibit a tapering trend along the interior of the busbar 140 in a direction closer to the pad 210 .

[0034] As can be seen, the width of the weld seam 310 can be controlled by adjusting the laser power and the laser irradiation time. When the laser power is large and / or the laser irradiation time is long, the laser does not attenuate obviously in the process of melting through the busbar 140. As a result, the weld seam 310 with a constant width is formed in the busbar 140, and appears as the weld seam 310 with an elongated rectangular shape in the weld cross section. When the laser power is small and / or the laser irradiation time is short, the laser is attenuated to some extent in the process of melting through the busbar 140. As a result, the weld seam 310 with a gradually decreasing width is formed in the busbar 140, and appears as the weld seam 310 with an elongated cone shape in the weld cross section.

[0035] In practical situations, different types of weld seams 310 can be formed to control the connection strength between the busbar 140 and the pad 210. In order to achieve high connection strength between the busbar 140 and the pad 210, a weld seam 310 with a constant width can be formed inside the busbar 140 to ensure that the weld seam 310 at the connection interface between the busbar 140 and the pad 210 has a sufficient width.

[0036] In some embodiments of the present disclosure, the width of the second segment 315 across the thickness of the pad 210 is fixed, or the width of the second segment 315 across the thickness of the pad 210 is tapered.

[0037] Similar to the first segment 314 of the weld seam 310, the width of the second segment 315 of the weld seam 310 can be kept constant at any location in the pad 210, or it can be tapered along the direction away from the busbar 140 in the pad 210. Similarly, different types of weld seams 310 can be formed to control the connection strength between the busbar 140 and the pad 210. When the width of the second segment 315 of the weld seam 310 is kept consistent at any location inside the pad 210, the weld seam 310 formed in the pad 210 can be uniform, and the stress change at each location of the weld seam 310 can be uniform, so that the weld seam 310 is not easily destroyed by the change of the external conditions. When the width of the second segment 315 of the weld seam 310 tends to decrease within the pad 210 in the direction away from the busbar 140, the extent of change in the internal structure of the pad 210 can be reduced, so that the original structure within the pad 210 is not destroyed as much as possible, and the structural strength of the original structure of the pad 210 can be ensured.

[0038] In some embodiments of the present application, the width of the joint between first segment 314 and second segment 315 is 50% to 120% of the width of first segment 314 at the surface of busbar 140 away from pad 210 .

[0039] For example, in a practical situation, the width of the joint between first segment 314 and second segment 315 may be 50%, 60%, 70%, 80%, 90%, 100%, 110% or 120% of the width of first segment 314 at the surface of busbar 140 away from pad 210, preferably 65% ​​to 85%.

[0040] In addition, when busbar 140 and pad 210 are in close contact with each other, no obvious molten metal filling is observed at the connection interface between busbar 140 and pad 210, and the width of the joint between first segment 314 and second segment 315 is kept within the range of the width of first segment 314 at the surface of busbar 140 away from pad 210. In addition, when pad 210 has recessed region 2102, the molten metal fills the recessed region 2102 during laser welding, so that the width of the joint between first segment 314 and second segment 315 is somewhat increased compared to the width of first segment 314 at the surface of busbar 140 away from pad 210. In some embodiments, when the width of first segment 314 at the surface of busbar 140 away from pad 210 is 0.3 mm to 0.4 mm, the width of the joint between first segment 314 and second segment 315 may be 0.25 mm to 0.45 mm.

[0041] By controlling the width of the joint between the first segment 314 and the second segment 315 of the weld seam 310, it is possible to provide sufficient connection strength at the connection interface between the bus bar 140 and the pad 210, thereby ensuring the connection reliability between the bus bar 140 and the pad 210.

[0042] In some embodiments of the present application, the weld seam 310 is linear on the surface of the bus bar 140, and the number of the linear weld seams 310 is at least one.

[0043] That is, during the welding process, the path along which the laser passes through busbar 140 may be straight or curved. Also, the path along which the laser passes through busbar 140 may be one or more.

[0044] By controlling the shape of the path that the laser takes through the busbar 140, a weld seam 310 can be formed across most of the surface area of ​​the busbar 140, forming a fixed connection between most of the surface area of ​​the busbar 140 and the pad 210.

[0045] In a practical situation, the shape of the weld seam 310 on the surface of the busbar 140 is a straight line, a wavy line, an S line, or a reciprocating telephone line shape. The start position of the weld seam 310 can be close to, away from, or overlap with the end position. For example, if the weld seam 310 on the surface of the busbar 140 is a straight line, the start position of the weld seam 310 is away from the end position. If the weld seam 310 on the surface of the busbar 140 is a non-closed circle, the start position of the weld seam 310 is close to the end position. If the weld seam 310 on the surface of the busbar 140 is a closed shape such as a square or circle, the start position of the weld seam 310 overlaps with the end position.

[0046] In some embodiments of the present application, there are multiple weld seams 310, and the multiple weld seams 310 are distributed sequentially along the width direction of the busbar 140, and the length of each weld seam 310 is greater than or equal to 3 mm and less than or equal to 5 mm, and the width of each weld seam 310 is greater than or equal to 0.35 mm and less than or equal to 0.45 mm.

[0047] For example, in practical situations, the length of the weld seam 310 may be 3 mm, 4 mm, or 5 mm, and the width of the weld seam 310 may be 0.35, 0.40, or 0.45. The width of the busbar 140 may be 4 mm to 7 mm.

[0048] By distributing multiple weld seams 310 sequentially along the width direction of busbar 140, the extension direction of weld seams 310 can be aligned with the longitudinal direction of busbar 140. This makes it possible to achieve a good fixing effect between busbar 140 and pad 210 along the longitudinal direction of busbar 140.

[0049] In practical situations, depending on the width of the busbar 140, the number of weld seams 310 may be two, three, four or five.

[0050] In some embodiments of the present application, the distance between two adjacent weld seams 310 is greater than or equal to 0.4 mm and less than or equal to 0.6 mm.

[0051] For example, in practical situations, the distance between two adjacent weld seams 310 may be 0.4 mm, 0.5 mm, or 0.6 mm.

[0052] By controlling the distance between two adjacent weld seams 310, interference between weld seams 310 can be avoided, and a good fixing effect can be achieved in the width direction of bus bar 140.

[0053] In some embodiments of the present application, the start positions of the multiple weld seams 310 are distributed on the surface of the busbar 140 along a single straight line, the end positions of the multiple weld seams 310 are distributed on the surface of the busbar 140 along a single straight line, and the line on which the start positions of the multiple weld seams 310 are located is parallel to the line on which the end positions are located.

[0054] In other words, the multiple weld seams 310 are distributed on the surface of the bus bar 140 while maintaining a parallel state, so that the weld seams 310 formed on the surface of the bus bar 140 can be made uniform. At the same time, it becomes easier to control the welding path of the laser head during the actual welding process, which is advantageous for smoothly completing the welding process.

[0055] In some embodiments, the area of ​​the region where bus bar 140 and pad 210 abut is defined as a first area, the area of ​​the region where welding occurs between bus bar 140 and pad 210 is defined as a second area, and the second area is 30% to 60% of the first area.

[0056] In the photovoltaic module of the present application, the second area is 30% to 60% of the first area, which ensures that there is a sufficient welding area between busbar 140 and pad 210 and that the welding area between busbar 140 and pad 210 is not too large, and therefore it is possible to ensure that busbar 140 does not melt when welding busbar 140. This ensures that there is a high pull-out force between busbar 140 and pad 210 after laser welding, and it is possible to improve the stability of busbar 140 and pad 210 after welding.

[0057] In some embodiments, the first area is 13 mm2 to 15 mm2. Note that the present application does not limit the value of the second area in this embodiment, and the second area is, for example, 4 mm2 to 7 mm2. This ensures that the second area is 30% to 60% of the first area.

[0058] In one example, the first area is 13 mm2 and the second area is 4 mm2. In another example, the first area is 14 mm2 and the second area is 6 mm2.

[0059] In some embodiments, the second area is 40% to 50% of the first area, which ensures that there is a sufficient welding area between busbar 140 and pad 210, and that the welding area between busbar 140 and pad 210 is not too large, which ensures that busbar 140 does not melt when welding busbar 140, and further ensures that there is a high pull-out force between busbar 140 and pad 210 after laser welding, thereby improving the stability of busbar 140 and pad 210 after welding.

[0060] In one example, the second area is 40% of the first area, which allows for optimal post-weld stability of the busbar 140 and the pad 210. In another example, the second area is 45% of the first area.

[0061] In the present application, there are no limitations on the specific shape of the welding pattern for welding and fixing bus bar 140 and pad 210, as long as the second area is 30% to 60% of the first area.

[0062] In some embodiments, the contact surfaces of the busbar and the pad are both flat surfaces.

[0063] In some embodiments, each weld seam 310 has both ends that are arranged sequentially along a first direction (i.e., the X direction shown in FIGS. 2 and 3), and the weld seams 310 are arranged sequentially along a second direction (i.e., the Y direction shown in FIGS. 2 and 3), where the first direction is perpendicular to the second direction. This allows the weld pattern for fixing the weld between the busbar 140 and the pad 210 to be distributed over a portion of the surfaces where the busbar 140 and the pad 210 abut against each other, which can further increase the stability of the busbar 140 and the pad 210 after welding.

[0064] In one example, the shape of the weld seam 310 on the surface of the busbar that is separated from the multiple battery cells 110 is a straight line, a broken line, or a curved line. When the shape of the weld seam 310 is a straight line, the number of weld seams 310 is three or more. This can prevent the width of the weld seam 310 from being too wide, and facilitate the use of laser welding, while ensuring that the second area is 30% to 60% of the first area.

[0065] 4 and 5, in some other embodiments, the multiple weld seams 310 include a first weld seam 311 and a second weld seam 312, where the first weld seam 311 surrounds and forms a closed pattern, and the second weld seam 312 is located within the closed pattern surrounded by the first weld seam 311. This allows the weld patterns for welding and fixing between the bus bar 140 and the pad 210 to be distributed over a portion of the surfaces of the bus bar 140 and the pad 210 that abut against each other, thereby improving the stability of the bus bar 140 and the pad 210 after welding.

[0066] In addition, the present application does not limit the shape of the closed pattern surrounded by the first weld seam 311. In one example, the shape of the closed pattern surrounded by the first weld seam 311 is circular. Alternatively, the shape of the closed pattern surrounded by the first weld seam 311 is rectangular.

[0067] In some embodiments, the shape of the second weld seam 312 is the same as the shape of the first weld seam 311 on the surface of the busbar. This allows the weld patterns for fixing the busbar 140 and the pad 210 by welding to be distributed over a portion of the surfaces of the busbar 140 and the pad 210 that abut against each other, further improving the stability after welding the busbar 140 and the pad 210. At the same time, the weld patterns can be easily formed by using a laser.

[0068] In addition, in other embodiments, the shape of the second welded seam 312 does not have to be the same as the shape of the first welded seam 311, in which case the shape of the second welded seam 312 may be a straight line, a broken line, or a curved line.

[0069] 5, in one example, the plurality of weld seams 310 further includes a third weld seam 313, and the second weld seam 312 surrounds and forms a closed pattern, and the third weld seam 313 is located within the closed pattern surrounded by the second weld seam 312. This can ensure that the second area is 30%-60% of the first area, and can prevent the weld seam 310 from being too wide, facilitating the use of laser welding.

[0070] In this example, the shape of the third welded seam 313 on the surface of the busbar may be the same as the shape of the second welded seam 312 and / or the first welded seam 311. Alternatively, the shape of the third welded seam 313 does not have to be the same as the shape of the second welded seam 312 and / or the first welded seam 311, in which case the shape of the third welded seam 313 may be a straight line, a broken line, or a curved line.

[0071] 1 to 5, in some embodiments, the number of bus bars 140 is two, the number of pads 210 is also two, and the bus bars 140 and the pads 210 are provided in one-to-one correspondence. In this embodiment, the junction box 200 may also be provided with a diode 220, one end of which is connected to one pad 210 and the other end of which is connected to another pad 210. In this manner, the diode 220 can provide a protective effect when the light receiving surface of the photovoltaic stack 100 is shaded.

[0072] In some embodiments, the materials of the busbar 140 and the pad 210 are the same. Thus, after the busbar 140 and the pad 210 are fixed by laser welding, the hot expansion volume / cold contraction volume of the busbar 140 is the same as the hot expansion volume / cold contraction volume of the pad 210. This can avoid the layer split phenomenon occurring between the busbar 140 and the pad 210. In one example, the materials of the busbar 140 and the pad 210 are both copper.

[0073] In some embodiments, the pad has a positioning region, the region where the bus bar and the pad abut is a facing region, the area of ​​the positioning region is larger than the area of ​​the facing region, and the facing region is located within the positioning region.

[0074] This ensures that, even if an error occurs in the process of aligning a portion of the surface of the busbar 140 with the facing area 112 before using a laser to weld the busbar 140 and the pad 210, and the portion of the surface of the busbar 140 is not perfectly aligned with the facing area 112, it is possible to ensure as much as possible that the portion of the surface of the busbar 140 is positioned facing the positioning area 111, and that the busbar 140 can be fixed to the pad 210 by laser welding.

[0075] It should be noted that in one example, the positioning region 111 occupies a portion of the surface of the pad 210 facing the busbar 140. In another example, the positioning region 111 occupies a portion of the surface of the pad 210 facing the busbar 140.

[0076] In some embodiments, the positioning area 111 has two first edges 113 arranged opposite each other in a first direction (i.e., the X direction shown in Figures 8 and 10), and the facing area 112 is located between the two first edges 113 and has a gap between it and either one of the two first edges 113.

[0077] This ensures that in the process of aligning a portion of the surface of busbar 140 with facing area 112, whether busbar 140 shifts along the first direction or along a direction opposite to the first direction, the portion of the surface of busbar 140 is positioned facing positioning area 111, and busbar 140 and pad 210 are fixed by laser welding.

[0078] In the present application, the dimension of the facing region 112 in the first direction is not limited, and the distance between the facing region 112 and either one of the two first edges 113 is also not limited.

[0079] In some embodiments, the dimension of the facing region 112 in the first direction is 3 mm to 5 mm, and there is a gap of 2 mm or more between the facing region 112 and either one of the two first edges 113. In one example, the dimension of the facing region 112 in the first direction is 4 mm, and there is a gap of 2 mm between the facing region 112 and either one of the two first edges 113.

[0080] In this embodiment, the dimension of facing region 112 in the first direction may be the same as the dimension of busbar 140 in the first direction, where the first direction may be the width direction of busbar 140.

[0081] In some embodiments, a portion of the facing region 112 is a welding region 2101, which is used to be attached to and welded to a portion of the bus bar 140 extending along the second direction (i.e., the Y direction shown in Figures 8 and 10), the first direction is perpendicular to the second direction, the positioning region 111 has two second edges 115 arranged opposite each other in the second direction, and the welding region 2101 is located between the two second edges 115 and has a gap between it and either one of the two second edges 115.

[0082] This ensures that, in the process of fixing a portion of the surface of the busbar 140 to the welding area 2101 of the pad 210 by laser welding, even if the busbar 140 is shifted along the second direction or along a direction opposite to the second direction, the portion of the surface of the busbar 140 is positioned directly opposite the positioning area 111, and the busbar 140 and the positioning area 111 of the pad 210 are fixed together by laser welding.

[0083] In the present application, the dimension of the welded area 2101 in the second direction is not limited, and the distance between the welded area 2101 and either one of the two second edges 115 is also not limited.

[0084] In some embodiments, the dimension of the welded area 2101 in the second direction is between 3 mm and 5 mm, with a distance of 2 mm or more between the welded area 2101 and one of the two second edges 115. In one example, the dimension of the welded area 2101 in the first direction is 4 mm, with a distance of 2 mm between the welded area 2101 and one of the two second edges 115.

[0085] In this embodiment, the longitudinal direction of the portion where bus bar 140 is attached to welded region 2101 and fixed by welding may be the second direction.

[0086] In some embodiments, the two pads 210 are disposed on opposite sides of the diode 220. In this case, the two pads 210 may have the same shape and size (as shown in FIGS. 8 and 9), or may have different shapes and sizes. This application is not limited thereto.

[0087] In some other examples, the diode 220 is located between two pads 210, and the two pads 210 and the diode 220 are distributed in a "U" shape (as shown in FIG. 10).

[0088] Some embodiments of the present application further provide a method for manufacturing a photovoltaic module, the method comprising:

[0089] Step 1: providing a photovoltaic stack, the photovoltaic stack including a plurality of battery cells, a welding strip, a back plate, and a bus bar, in which a plurality of battery cells are connected via the welding strip to form at least one cell string, the at least one cell string is stacked on the back plate, the welding strip is connected to the bus bar, and the plurality of cell strings are connected via the bus bar to form a cell string group, and the series connection of the cell strings can be automatically performed by an automatic serial welding machine;

[0090] Step 2: providing a junction box, the junction box being installed on a side of the back plate away from the battery cells and fixedly connected to the back plate, the junction box having a pad provided therein, the junction box being capable of being fixed to the back plate by adhesive;

[0091] a step 3 of passing the busbar through an opening provided in the back plate, exposing a part of the busbar on a surface of the back plate of the photovoltaic stack, and introducing the part of the busbar that has passed through the back plate into a junction box, with the part of the busbar being in a bent state; after the busbar has been introduced into the junction box, the bent part of the busbar abuts against a pad in the junction box, and the busbar can be automatically pressed against the pad by an indenter;

[0092] and step 4, using a laser head, laser welding the abutment points of the busbar and the pad to connect the busbar and the pad to each other, whereby a plurality of weld seams are formed in the area where welding has occurred between the busbar and the pad, the weld seams extending from the surface of the busbar away from the pad toward the inside of the pad, the busbar and the pad located at the weld seam points being formed as an integral structure by the laser welding, and the extension depth of each weld seam within the pad is 80% or less of the thickness of the pad.

[0093] In some embodiments of the present application, the power of the laser emitted from the laser head is 550W (watts) to 750W.

[0094] For example, in practical situations, the power of the laser emitted from the laser head may be 550W, 580W, 600W, 620W, 640W, 660W, 680W, 700W, 720W or 750W.

[0095] As the output power of the laser head increases, the depth of the weld seam formed in the connection structure between the busbar and the pad also increases, and the weld seam that extends into the pad is closer to the bottom of the junction box. By keeping the power of the laser output from the laser head within the range of 550W to 750W, the extension depth of the weld seam in the pad is appropriate, and it can be ensured that there is good fixing effect and good current transmission effect between the busbar and the pad.

[0096] In some embodiments of the present application, the welding speed of the laser head is greater than or equal to 60 mm / s (millimeters per second) and less than or equal to 100 mm / s.

[0097] For example, in practical situations, the welding speed of the laser head may be 60mm / s, 70mm / s, 80mm / s, 90mm / s or 100mm / s.

[0098] As the welding speed of the laser head increases, the width of the weld seam formed on the busbar decreases. If the welding speed is too fast, the connection strength of the busbar and the pad may be insufficient. If the welding speed is too slow, melt-through may occur in some areas of the pad. Therefore, by controlling the welding speed of the laser head, it is possible to avoid poor quality of the weld seam caused by the welding speed of the laser head being too fast, and to avoid melt-through on the pad in the junction box caused by the welding speed of the laser head being too slow.

[0099] In addition, as the width of the irradiation area on the busbar surface of the laser emitted from the laser head increases, the width of the weld seam formed on the busbar also increases. Since the width of the weld seam can reflect the welding quality to a certain extent, the welding quality of the busbar and pad connection structure in the photovoltaic module can be ensured by controlling the width of the irradiation area on the busbar surface of the laser light emitted from the laser head in an actual situation so that the welding quality of the busbar and pad connection structure can meet the requirements. For example, in some embodiments, when the width of the weld seam on the busbar is 0.3 mm or more and 0.4 mm or less, the welding quality is considered to meet the requirements. Therefore, the width of the irradiation area on the busbar surface of the laser light emitted from the laser head can be controlled to be maintained within a range of 0.3 mm to 0.4 mm.

[0100] In response to the problem that the conventional inspection method cannot meet the production demand of the photovoltaic module, some embodiments of the present application further provide another photovoltaic module manufacturing method.

[0101] In the prior art, during the process of welding the busbar and the pad, it is necessary to confirm the position of the busbar and the junction box with human eyes to ensure the welding accuracy between the busbar and the pad in the junction box. At the same time, after the welding is completed, it is necessary to check with human eyes whether the welding result meets the expected requirements. Since the detection accuracy of the human eye is low, it is easy to produce defective products such as welding misalignment and welding errors during welding, and there is a disadvantage that it is easy to cause oversights when the human eye detects after the welding is completed, which may lead to products with poor welding being sent to the next process.

[0102] In contrast, another photovoltaic module manufacturing method provided by some embodiments of the present application further includes visually detecting the position before welding and the weld seam after welding. The positions of the busbar and the junction box are located by a visual detection system to determine the welding position of the busbar in the actual welding process. Furthermore, the visual detection system detects the weld seam formed after welding, and judges whether the weld seam meets the expected requirements based on the detection result.

[0103] The manufacturing process of this photovoltaic module includes the following steps.

[0104] Step S100, a photovoltaic stack is provided.

[0105] The photovoltaic stack includes a cell string group, the cell string group includes a plurality of cell strings, and the plurality of cell strings are connected by a bus bar. Each cell string is formed by connecting a plurality of battery cells in series with a welding strip. The cell string is formed by connecting a plurality of battery cells in series, and the cell string group is formed by connecting a plurality of cell strings in series or parallel, thereby increasing the voltage and power of the photovoltaic module and ensuring that the power generation effect of the photovoltaic module can meet the expected requirements.

[0106] Step S200: a junction box is installed on the photovoltaic stack, and a bus bar of the photovoltaic stack is introduced into the junction box.

[0107] The photovoltaic module is electrically connected to the external electronic control device through a junction box, and includes a diode in the junction box and a circuit formed through a cable. The diode provides protection for the cell string group of the photovoltaic module, and a conductive terminal portion of the diode is connected to the bus bar to connect the cell string group of the photovoltaic module to the external electronic control device.

[0108] Step S300: Press the busbar against the pad inside the junction box.

[0109] The pads in the junction box can provide a fixed position for the busbar. The pads can be formed on the conductive terminals of the diodes, i.e., the conductive terminals of the diodes are formed to extend in a plane with a certain area to realize connection with the busbar. Alternatively, the pads can be independent pad parts, i.e., the independent pad parts are fixed in the junction box by fasteners such as rivets, the independent pad parts are connected to the conductive terminals of the diodes, and the busbars are pressed against the pads in the junction box, which is favorable for subsequent laser welding.

[0110] Step S400: Pre-weld visual detection is performed on the relative positions of the busbar and the junction box.

[0111] Visual detection can be realized by a CCD machine vision system, which includes a CCD camera and a control center, where the CCD camera moves under the control of the control center to photograph the object to be detected, and the photographed result can be transmitted to the control center for recognition, and the CCD machine vision system includes positioning function, measurement function and recognition function, that is, the CCD machine vision system can automatically position the external position features of the object to be detected, automatically measure the external dimensions of the object to be detected, and recognize the color, graphic or character code of the object to be detected, etc. At the same time, the CCD machine vision system can build a database model, and compare the image of the object to be detected with the image in the database to determine whether the object to be detected is acceptable.

[0112] By detecting the relative positions of the busbar and the junction box, the weld area and the start and end positions of the weld on the busbar can be determined prior to welding.

[0113] Step S500: Using a laser head, laser weld the busbar and the pad.

[0114] The laser head can achieve welding by emitting a laser beam of a specific power. After the laser beam emitted from the laser head reaches the surface of the busbar, it melts the busbar and the pad. As the laser beam moves, a weld seam is formed along the path the laser beam passes, and the busbar located at the weld seam is melted together with the pad.

[0115] Step S600: perform post-weld visual inspection on the weld seam after the laser welding. By performing post-weld visual inspection on the weld seam after the laser welding, it can be determined whether the weld seam formed after welding meets the requirements.

[0116] The manufacturing process of the photovoltaic module provided by some embodiments of the present application adopts laser welding instead of the conventional thermocompression bonding. In the process of laser welding, a direct contact part can be formed at the interface between the busbar and the pad, which can replace the metal tin fused at the interface between the busbar and the pad in the conventional thermocompression bonding. Since there is no need to use tin paste to fix the busbar and the pad, the connection reliability between the busbar and the pad is not affected by the cold solder connection caused by the lack of tin paste. At the same time, after the busbar and the pad are fixed, the metal material of the busbar and the metal material of the pad are melted together, so that the connection strength between them can be ensured. This can avoid the occurrence of poor connection of the diode in the junction box during the manufacturing process of the photovoltaic module.

[0117] In addition, by visually detecting the relative positions of the busbar and the pad before welding, the welding position of the busbar on the pad can be determined based on the detection result, and precise control can be achieved during welding between the busbar and the pad, so that the welding is performed within a preset range and defects such as welding deviation and welding errors are prevented. At the same time, by visually detecting the weld seam after welding is completed, it can be determined based on the detection result whether the weld seam meets the requirements, and welded products that do not meet the requirements can be selected in a timely manner.

[0118] In some embodiments of the present application, as shown in FIG. 12, step S100 of providing a photovoltaic stack includes the following steps.

[0119] S110, serial welding is performed on the battery cells to form a cell string group.

[0120] A battery cell generally includes a substrate, a PN junction and a passivation structure formed on the substrate, and a grid line electrode located on the surface of the battery cell. The substrate is generally a silicon substrate, and the PN junction formed on the silicon substrate generates a current when irradiated with light. The grid line electrode includes fine grid lines, which are used to extract the current generated by the PN junction. The battery cell can be automatically serially welded by an automatic serial welding machine. In the serial welding process, a cell string is formed by first connecting multiple battery cells with a welding strip, and then a cell string group is formed by connecting multiple cell strings with a bus bar.

[0121] S120, a first sealing adhesive film is laid on a cover plate.

[0122] The cover plate is a protective plate located in front of the cell string group, and serves to protect the cell string group. At the same time, the cover plate can adopt glass to achieve the function of transmitting light in front of the cell string group. The first sealing adhesive film can be an EVA adhesive film, a POE adhesive film or a PVB adhesive film, and is used to perform the adhesive function in front of the cell string group.

[0123] S130, laying the cell string group on a first sealing adhesive film.

[0124] S140, welding busbars to cell string groups.

[0125] The welding strips on the busbar and the cell string are welded while maintaining a crossed state, and in actual situations, the welding strips on the busbar and the cell string can be kept vertical, reducing the transport path of the photocurrent generated from the cell string and lowering current loss.

[0126] S150, laying a second sealing adhesive film on the cell string group.

[0127] The second sealing adhesive film is located on the rear surface of the cell string group, and the second sealing adhesive film can be an EVA film, a POE film or a PVB film, and is used to perform an adhesive function on the rear surface of the cell string group.

[0128] S160, laying a back plate on the second sealing adhesive film.

[0129] The backplate plays a protective role on the rear side of the cell string group, and the backplate can also adopt glass to play a role of transmitting light on the rear side of the cell string group. At the same time, the backplate has a wire lead hole, and the busbar can pass through the wire lead hole of the backplate and be partially exposed on the surface of the backplate. Usually, the backplate has one to three sets of wire lead holes, and each wire lead hole corresponds to a pair of busbars.

[0130] S170, the cover plate, the first sealing adhesive film, the cell string group, the second sealing adhesive film and the back plate are laminated and fixed to obtain a photovoltaic laminate.

[0131] The lamination process can be carried out in the lamination cavity of the laminator, and the surface of the cover plate and the back plate can be covered with a high temperature cloth before lamination, so as to prevent the sealing adhesive film from protruding during the lamination process. At the same time, the bus bar penetrating the back plate can be kept attached to the back plate during lamination, that is, the part of the bus bar penetrating the back plate during lamination can be folded, and the part of the bus bar penetrating the back plate can be kept attached to the back plate, so as to avoid affecting the closing of the lamination cavity of the laminator. After the lamination is completed to form the photovoltaic laminate, the bus bar attached to the back plate can be returned to its original position, and the part of the bus bar penetrating the back plate can be kept perpendicular to the back plate, so that the bus bar can be introduced into the junction box when the junction box is installed. After the lamination is completed to form the photovoltaic laminate, it can be detected whether the photovoltaic laminate has defects such as hidden cracks, fragments, and cold solder connections.

[0132] After the manufacturing of the photovoltaic stack is completed, a junction box is provided on the photovoltaic stack. The junction box can be fixed to the photovoltaic stack with an adhesive, and the junction box is provided on the surface of the back plate of the photovoltaic stack corresponding to the position of the bus bar. At the same time, the bus bar introduced into the junction box can be pressed against the pad in the junction box with an indenter. Furthermore, the positions of the bus bar and the junction box are detected before starting welding.

[0133] Usually, one or more junction boxes can be provided in the photovoltaic stack, and for example, the number of junction boxes provided in the photovoltaic stack may be 2 to 6, and preferably 3. The position of the junction box on the back surface of the photovoltaic stack may be an edge of the photovoltaic stack or an inner side close to the center of the photovoltaic stack. When the junction box is provided on the inner side close to the center of the photovoltaic stack, it is preferably provided on the center line of the photovoltaic stack, and more preferably on the center line of the long side of the photovoltaic stack. At least one diode is provided inside each junction box provided in the photovoltaic stack, and the electrical connection between at least one diode and a bus bar in one photovoltaic module is realized by using the technical means of the present invention.

[0134] In some embodiments of the present application, as shown in FIG. 13, the step S400 of performing pre-weld visual detection on the relative positions of the busbar and the junction box includes the following steps.

[0135] Step S410: positioning and photographing the junction box.

[0136] In the detection process by the visual detection system, the detection object needs to be located first, and after the position of the detection object is obtained, the junction box is accurately photographed so as to accurately recognize the position of the junction box according to the structural features in the junction box. In some embodiments, the precise position of the junction box can be detected according to the peripheral contour features or internal component features of the junction box.

[0137] In step S420, the busbar is positioned and photographed.

[0138] Similar to a junction box, when detecting the position of a busbar, the position of the busbar is first obtained, and then the busbar is accurately photographed and the position of the busbar is detected according to the structural features of the busbar.

[0139] Step S430: obtain the relative positions of the busbar and the junction box based on the photographed results of the junction box and the busbar.

[0140] After obtaining the precise position of the junction box and the precise position of the busbar respectively, the relative positions of the busbar and the junction box can be obtained, i.e., the actual position of the busbar with respect to the pad in the junction box can be obtained, so that the actual welding position of the busbar with respect to the pad in the junction box can be easily controlled.

[0141] In some embodiments of the present application, as shown in FIG. 14, step S410 of positioning and photographing the junction box includes the following steps.

[0142] S411, photographing a photovoltaic stack, and recognizing a diode in a junction box based on the photographing result of the photovoltaic stack.

[0143] A junction box is provided on the surface of the back plate of the photovoltaic stack, and in the process of welding, the surface of the back plate of the photovoltaic stack is facing upward, and the photovoltaic stack can be photographed to obtain a surface image of the back plate of the photovoltaic stack. The image of the photovoltaic stack contains the pixel feature of the junction box. Since the diode is fixed in the junction box and does not change position, the position of the diode can be obtained by obtaining the position of the junction box. Therefore, the position of the junction box can be obtained by recognizing a specific pixel feature in the photographed result of the photovoltaic stack, that is, the diode in the junction box. It should be noted that the recognition of the diode can be realized by recognizing the color, and the packaging color of the diode in the junction box is black, which is obviously different from the metal color of the surrounding pads, so it is easy to recognize. At the same time, the packaging material of the diode is further provided with a text label to indicate the parameter characteristics of the diode. By combining the text label on the package of the diode, the feature of the diode in the image of the photovoltaic stack can be easily recognized. The resulting image of the photovoltaic stack is shown in FIG. 16 and as can be seen, the diodes in the junction box have a more pronounced dark black character compared to the pads which have a bright white surrounding.

[0144] S412, photographing the position of the diode, and obtaining the position of the junction box based on the photographing result.

[0145] After obtaining the position of the junction box by recognizing the features of the diode in the photovoltaic stack image, the diode in the junction box is photographed, and the precise position of the diode is detected from the relative position between the outer contour or text label of the diode in the diode image and the photographing center point, thereby obtaining the precise position of the junction box. The photographed image of the diode position can be seen in Figure 17, as can be seen from the figure, the junction box is obviously located at the center of the image, and the position of the junction box can be obtained precisely by using the outer contour of the diode.

[0146] After obtaining the precise position of the junction box, the precise position of the busbar is subsequently detected.

[0147] In some embodiments of the present application, as shown in FIG. 15, step S420 of positioning and photographing the busbar may include the following steps.

[0148] S421, an image of a photovoltaic stack is captured, and two opposing edges of a bus bar in a width direction are recognized based on the captured image of the photovoltaic stack.

[0149] When performing position detection for the busbar in accordance with the acquired position of the junction box, the photovoltaic stack can be photographed first, and the acquired image of the photovoltaic stack includes pixel features of the busbar. When the busbar is pressed against the pad in the junction box, two opposite edges in the width direction of the busbar are located within the weldable area of ​​the pad. Therefore, in the acquired image of the photovoltaic stack, the busbar can be recognized by the boundary line formed by the two opposite edges in the width direction of the busbar, and the position of the busbar can be obtained.

[0150] S422, two opposing edges of the bus bar in the width direction are photographed, and the position of the bus bar is obtained based on the photographing results.

[0151] After obtaining the position of the busbar by recognizing the edge features of the busbar in the image of the photovoltaic stack, the busbar inside the junction box is photographed, and the precise position of the busbar is detected and obtained from the relative position between the outer contour of the busbar in the busbar image and the photographing center point. The photographed image of the busbar location can be seen in Figure 18, and as can be seen from the figure, the two opposing edges of the busbar in the width direction have obvious bright white color features (the edges indicated by the upper and lower two long sides of the left rectangular dotted frame in the image in Figure 18), and the position of the busbar can be obtained precisely from the two opposing edges in the width direction of the busbar.

[0152] After obtaining the precise positions of the junction box and the busbar respectively, the positions of the two can be compared to obtain the relative positions of the busbar and the junction box. That is, based on the precise positions of the junction box and the busbar, the actual position where the busbar is located in the junction box can be detected. After determining the precise position of the junction box, the position of the pad in the junction box can be determined. In this way, the actual position where the busbar is pressed against the pad in the junction box can be obtained, and it can be determined whether the position of the busbar on the pad in the junction box is misaligned.

[0153] Some embodiments of the present application include performing position sensing on the relative positions of the busbar and pads and then adjusting the welding position of the laser head based on the relative positions of the busbar and junction box prior to using the laser head to laser weld the busbar and pads.

[0154] As can be understood, in the process of pressing the busbar against the pad in the junction box with the indenter, the actual pressing position may be deviated due to the flatness of the surface of the busbar, the flatness of the surface of the pad, or the pressure center of gravity of the indenter. After obtaining the relative positions of the busbar and the junction box by the visual detection system, the welding position of the laser head can be adjusted according to the relative positions so that the welding process can be performed along a predetermined path on the surface of the busbar. This can avoid welding misalignment, welding errors, and also avoid the pad melt-through problem caused by welding misalignment.

[0155] In the actual welding process, the laser head can weld on the surface of the busbar along a straight or curved path. At the same time, the laser head can weld the busbar and the pad along a closed or non-closed path. That is, the weld seam formed by the path of the laser light on the surface of the busbar can be straight or curved. Moreover, the weld seam formed by the path of the laser light on the surface of the busbar can have a closed pattern such as a square, a circle, or an non-closed pattern such as a wavy or S-shape.

[0156] In addition, the weld seam formed after welding needs to be inspected to determine whether the final welded product meets the requirements. Usually, the parameter characteristics of the weld seam that meet the requirements can be obtained through pre-testing. For example, the length characteristic, width characteristic, or depth characteristic of the weld seam must be within a certain range to obtain a welded product that meets the requirements. In order to facilitate the judgment of the weld quality of the busbar after laser welding, in actual situations, the products that pass the weld quality test are selected and tested to confirm under what circumstances the weld seam on the surface of the busbar can meet the weld quality requirements.

[0157] In some embodiments of the present application, performing post-weld visual detection on the weld seam after laser welding includes photographing the weld seam and detecting whether the width of the weld seam is within a range of 0.3 mm to 0.4 mm.

[0158] That is, after the welding between the busbar and the pad in the junction box is completed, the width of the weld seam on the surface of the busbar can be detected to judge whether the welding quality meets the requirements. If the width of the weld seam is 0.3 mm or more and 0.4 mm or less, it is considered that the welding quality meets the requirements. On the other hand, if the width of the weld seam is less than 0.3 mm or more than 0.4 mm, it is considered that the welding quality does not meet the requirements. The result of photographing the position of the busbar after welding can be referred to FIG. 19. Here, there is a phenomenon that some of the parallel weld seams located on the left side of the image are too wide, and therefore there is an interference phenomenon between two adjacent weld seams, that is, there is a part of the welding area of ​​the two adjacent weld seams overlapping (the black block area formed by the adhesion of two parallel black lines in the left circle in FIG. 19), and the welding quality is poor. The distribution of the multiple parallel weld seams on the right side of the image is relatively uniform, and there is obvious space between two adjacent weld seams (the bright white area between the two parallel black lines in the right circle in Figure 19), indicating good weld quality.

[0159] Additionally, some embodiments of the present application include using the laser head to laser weld the busbar and the pad together, and further including using a photoelectric sensor to detect an optical emission signal during the welding process of the laser head.

[0160] By detecting the welding process of the busbar and the pads in the junction box, it is possible to determine in real time whether there is a problem with the welding process, and if a problem occurs in the welding, the welding can be stopped immediately, and by combining this with the pre-welding position detection of the visual detection system, the final welding quality can be ensured.

[0161] The optical emission signal may include any of and combinations of visible light signals, laser reflection signals, and infrared light signals.

[0162] The optical radiation phenomena involved in the laser welding process include visible light, laser reflection and infrared light. These emitted optical signals can reflect the state of the weld and whether defects occur during the welding process. The visible light comes from metal vapor, the laser reflection comes from the laser signal emitted from the laser head, and the infrared light comes from the thermal radiation from the metal molten pool formed by the laser irradiation. The photoelectric sensor can convert the optical radiation signal generated during the welding process into an electrical signal and then transmit the electrical signal to the detection system, so that the inspection system can analyze the emitted optical signal and check the quality of the busbar welding, thereby achieving the purpose of defect detection and quality monitoring. Different optical radiation signals can be detected by different photoelectric sensors.

[0163] In the visible light detection results, a decrease in the visible light signal indicates a decrease in the amount of metal vapor during the welding process, and an increase in the visible light signal indicates an increase in the amount of metal during the welding process. In the laser reflection signal detection results, a decrease in the laser reflection signal indicates an attenuation of the laser power, a decrease in the depth of the keyhole formed by the laser irradiation, and a decrease in the laser light reflected by the keyhole, and an increase in the laser reflection signal indicates a decrease in the absorption of the laser energy by the metal, and an increase in the laser reflection. In the infrared light signal detection results, a decrease in the infrared light signal indicates a decrease in the energy arriving at the molten pool, and a decrease in the thermal radiation of the molten pool, and an increase in the infrared light signal indicates an increase in the energy arriving at the molten pool, and an increase in the thermal radiation of the molten pool.

[0164] In practical situations, a threshold value can be set for each optical emission signal to determine whether defects will occur in the welding process. The threshold value can also be obtained by testing. Based on the parameter range of each optical emission signal when the welding quality between the busbar and the pad in the junction box meets the requirements, the range in which each optical emission signal needs to be controlled in the welding process is obtained. If each optical emission signal exceeds the corresponding threshold value, it indicates that there is a high possibility that welding defects will occur in the welding process, and the progress of the welding process can be controlled according to whether the detection result of each optical emission signal exceeds the threshold value.

[0165] In some embodiments of the present application, when the bus bar and the pad are laser welded using a laser head, the power of the laser emitted from the laser head is 550 W (watts) or more and 750 W or less, and the welding speed is 60 mm / s or more and 100 mm / s or less.

[0166] For example, in practical situations, the laser power emitted from the laser head may be 550W, 580W, 600W, 620W, 640W, 660W, 680W, 700W, 720W or 750W, and the welding speed of the laser head may be 60mm / s, 70mm / s, 80mm / s, 90mm / s or 100mm / s.

[0167] By controlling the welding power of the laser head, it is possible to control the energy intensity of the laser light emitted from the laser head when it reaches the busbar surface, and to control the energy intensity of the laser light that reaches the busbar surface during the welding process to be within a reasonable range, thereby avoiding the failure to obtain the expected welding depth due to low laser energy intensity, and avoiding the problem of the pad melting through due to high laser energy.

[0168] At the same time, the welding speed of the laser head is controlled to finally form a welded finished product that meets the quality requirements, avoiding a welding speed that is too slow, which will cause the laser to stay in the welding area for a long time and resulting in a weld seam that is too wide, and avoiding a welding speed that is too fast, which will ultimately result in a weld seam that is too narrow.

[0169] In addition, since the width of the weld seam can reflect the welding quality to some extent, in order to ensure that the welding quality of the busbar-pad connection structure in the photovoltaic module meets the requirements, in a practical situation, the width of the irradiation area on the busbar surface of the laser light emitted from the laser head can be controlled to ensure the welding quality of the busbar and pad. For example, in some embodiments, it is considered that the welding quality can meet the requirements when the width of the weld seam on the busbar is 0.3 mm or more and 0.4 mm or less. Therefore, the width of the irradiation area on the busbar surface of the laser light emitted from the laser head can be controlled to be within the range of 0.3 mm to 0.4 mm.

[0170] In some embodiments of the present application, introducing the busbars of the photovoltaic stack into the junction box includes bending the busbars and passing the bent portion through the junction box.

[0171] The bend angle may be 90 degrees, the bent portion being perpendicular to the surface on which the backplate of the photovoltaic stack is located, the bent portion penetrating into the junction box and parallel to the pads in the junction box, and can be bonded to the pads in the junction box.

[0172] As shown in FIG. 20 , some embodiments of the present application further provide a photovoltaic module manufacturing apparatus including a mounting mechanism 20, a pressing mechanism 30, a laser head 40, and a visual detection system, where the mounting mechanism 20 is used for mounting the photovoltaic stack 100, the pressing mechanism 30 is used for pressing the busbar against a pad in a junction box 200 on the photovoltaic stack 100, the laser head 40 is used for laser welding the busbar and the pad, and the visual detection system includes a first visual detector 50 for performing pre-welding visual detection of the relative positions of the busbar and the junction box 200 and a second visual detector 60 for performing post-welding visual detection of the weld seam after laser welding.

[0173] Here, the mounting mechanism 20 not only mounts the photovoltaic stack 100, but also transports the photovoltaic stack 100. The pressing mechanism 30 can move the indenter by using an elastic and transmission structure. The first visual detector 50 and the second visual detector 60 can use CCD cameras and are electrically connected to the same control center, and images taken by the first visual detector 50 and the second visual detector 60 can be transmitted to the same control center, so that the relative positions of the busbar and the junction box 200 and the weld seam after laser welding can be sequentially visually detected on the same monitor screen during the manufacturing process of the photovoltaic module.

[0174] Those skilled in the art will understand that the above embodiments are specific examples for implementing the present application, but various changes in form and details are possible in practice without departing from the spirit and scope of the present application. Since any person skilled in the art can make changes and modifications without departing from the spirit and scope of the present application, the scope of protection of the present application should be based on the scope limited by the claims.

Claims

1. a photovoltaic stack and a junction box; The photovoltaic stack includes a plurality of battery cells, at least one welding strip, a back plate, and a bus bar, and the plurality of battery cells are connected via the welding strip to form at least one cell string, and the at least one cell string is stacked on the back plate, and the welding strip is connected to the bus bar, the junction box is located on a side of the back plate away from the battery cells, the junction box is fixedly connected to the back plate, and a pad is provided on the junction box; wherein the bus bar passes through an opening provided in the back plate and comes into contact with the pad, and the bus bar and the pad are connected to each other by laser welding; a plurality of weld seams are formed in the welded region, the welded region referring to an area where laser welding is performed between the bus bar and the pad, the bus bar and the pad are formed as an integral structure by the plurality of weld seams, each weld seam extends from the bus bar toward the inside of the pad, and the extension depth of each weld seam within the pad is always 30% to 45% of the thickness of the pad; The bus bar and the pad are made of the same material, the pad includes a surface of the pad facing the busbar and a plurality of recessed areas formed in the weld area, the recessed areas each surrounding the weld seam, and there is a gap between a portion of the surface of the pad facing the busbar that is located within the recessed area and a surface of the busbar facing the pad. A photovoltaic module comprising:

2. the plurality of weld seams penetrate an entire thickness of the bus bar, and the shapes of the plurality of weld seams on a surface of the bus bar that is away from the plurality of battery cells are straight lines, broken lines, or curved lines.

2. The photovoltaic module of claim 1.

3. each of the plurality of weld seams includes a first segment located inside the bus bar and a second segment located inside the pad, the first segment and the second segment being in contact with each other at an interface where the bus bar and the pad are bonded to each other; 2. The photovoltaic module of claim 1.

4. a width of the first segment is fixed in a direction from the bus bar to the pad, or a width of the first segment is gradually reduced in a direction from the bus bar to the pad; 4. A photovoltaic module according to claim 3.

5. The width of the second segment in the thickness direction of the pad is fixed, or the width of the second segment in the thickness direction of the pad is gradually reduced.

4. A photovoltaic module according to claim 3.

6. the plurality of weld seams have a straight line shape on a surface of the busbar, the plurality of weld seams are distributed along a width direction of the busbar, the length of each of the weld seams is 3 mm or more and 5 mm or less, and the width of each of the weld seams is 0.3 mm or more and 0.4 mm or less.

2. The photovoltaic module of claim 1.

7. the plurality of weld seams on a surface of the bus bar are linear, and a distance between two adjacent weld seams is 0.4 mm or more and 0.6 mm or less; 2. The photovoltaic module of claim 1.

8. an area where the bus bar and the pad contact each other is defined as a first area, an area where welding occurs between the bus bar and the pad is defined as a second area, and the second area is 30% to 60% of the first area; 8. The photovoltaic module according to claim 1, wherein the photovoltaic module is a photovoltaic module.

9. the second area is between 40% and 50% of the first area; 9. The photovoltaic module of claim 8.

10. the plurality of weld seams includes a first weld seam and a second weld seam, the first weld seam surrounds and forms a closed pattern, and the second weld seam is located within the closed pattern surrounded by the first weld seam; 2. The photovoltaic module of claim 1.

11. a shape of the second weld seam is the same as a shape of the first weld seam on a surface of the bus bar; 11. The photovoltaic module of claim 10.

12. The plurality of weld seams further includes a third weld seam, the second weld seam surrounding and forming a closed pattern, and the third weld seam is located within the closed pattern surrounded by the second weld seam.

11. The photovoltaic module of claim 10.

13. the pad has a positioning region, the positioning region occupying a part or all of a surface of the pad facing the busbar; a region where the bus bar and the pad contact each other is a facing region, an area of ​​the positioning region is larger than an area of ​​the facing region, and the facing region is located within the positioning region; 2. The photovoltaic module of claim 1.

14. The positioning area includes two first edges disposed opposite to each other in a first direction, and the facing area is located between the two first edges and has a gap between the facing area and either one of the two first edges.

14. The photovoltaic module of claim 13.

15. a welding area is an area where welding occurs between the bus bar and the pad, the positioning area has two second edges arranged opposite to each other in a second direction perpendicular to the first direction, the welding area is located between the two second edges and has a gap between the welding area and either one of the two second edges; 15. Photovoltaic module according to claim 13 or 14.

16. The number of the pads is two, and the two pads are used to connect to different bus bars of the same photovoltaic stack.

2. The photovoltaic module of claim 1.

17. the junction box further includes a diode, one end of the diode being connected to one of the two pads and the other end of the diode being connected to the other of the two pads; 17. The photovoltaic module of claim 16.

18. The diode is located between the two pads, and the two pads and the diode are distributed in a "U" shape.

20. The photovoltaic module of claim 17.

19. A photovoltaic stack is provided, the photovoltaic stack including a plurality of battery cells, at least one welding strip, a back plate, and a bus bar, wherein a plurality of the battery cells are connected to each other via the welding strip to form at least one cell string, the at least one cell string being stacked on the back plate, and the welding strip being connected to the bus bar; A junction box is provided, the junction box being disposed on a side of the back plate away from the battery cells and fixedly connected to the back plate, and a pad is provided within the junction box; the bus bar is passed through an opening provided in the back plate and brought into contact with the pad; and laser welding the busbar and the pad to connect the busbar and the pad to each other; a plurality of weld seams are formed in the welded region, the welded region referring to an area where laser welding is performed between the bus bar and the pad, the bus bar and the pad are formed as an integral structure by the plurality of weld seams, each weld seam extends from the bus bar toward the inside of the pad, and the extension depth of each weld seam within the pad accounts for 30% to 45% of the thickness of the pad in all cases; The bus bar and the pad are made of the same material, the pad includes a surface of the pad facing the busbar and a plurality of recessed areas formed in the weld area, the recessed areas each surrounding the weld seam, and there is a gap between a portion of the surface of the pad facing the busbar that is located within the recessed area and a surface of the busbar facing the pad. A method for manufacturing a photovoltaic module comprising the steps of:

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